Science.gov

Sample records for cluster cooling flows

  1. SIMULATING THE COOLING FLOW OF COOL-CORE CLUSTERS

    SciTech Connect

    Li Yuan; Bryan, Greg L.

    2012-03-01

    We carry out high-resolution adaptive mesh refinement simulations of a cool core cluster, resolving the flow from Mpc scales down to pc scales. We do not (yet) include any active galactic nucleus (AGN) heating, focusing instead on cooling in order to understand how gas reaches the supermassive black hole at the center of the cluster. We find that, as the gas cools, the cluster develops a very flat temperature profile, undergoing a cooling catastrophe only in the central 10-100 pc of the cluster. Outside of this region, the flow is smooth, with no local cooling instabilities, and naturally produces very little low-temperature gas (below a few keV), in agreement with observations. The gas cooling in the center of the cluster rapidly forms a thin accretion disk. The amount of cold gas produced at the very center grows rapidly until a reasonable estimate of the resulting AGN heating rate (assuming even a moderate accretion efficiency) would overwhelm cooling. We argue that this naturally produces a thermostat which links the cooling of gas out to 100 kpc with the cold gas accretion in the central 100 pc, potentially closing the loop between cooling and heating. Isotropic heat conduction does not affect the result significantly, but we show that including the potential well of the brightest cluster galaxy is necessary to obtain the correct result. Also, we found that the outcome is sensitive to resolution, requiring very high mass resolution to correctly reproduce the small transition radius.

  2. Cooling Flow Spectra in Ginga Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III

    1997-01-01

    The primary focus of this research project has been a joint analysis of Ginga LAC and Einstein SSS X-ray spectra of the hot gas in galaxy clusters with cooling flows is reported. We studied four clusters (A496, A1795, A2142 & A2199) and found their central temperatures to be cooler than in the exterior, which is expected from their having cooling flows. More interestingly, we found central metal abundance enhancements in two of the clusters, A496 and A2142. We have been assessing whether the abundance gradients (or lack thereof) in intracluster gas is correlated with galaxy morphological gradients in the host clusters. In rich, dense galaxy clusters, elliptical and SO galaxies are generally found in the cluster cores, while spiral galaxies are found in the outskirts. If the metals observed in clusters came from proto-ellipticals and proto-S0s blowing winds, then the metal distribution in intracluster gas may still reflect the distribution of their former host galaxies. In a research project which was inspired by the success of the Ginga LAC/Einstein SSS work, we analyzed X-ray spectra from the HEAO-A2 MED and the Einstein SSS to look for temperature gradients in cluster gas. The HEAO-A2 MED was also a non-imaging detector with a large field of view compared to the SSS, so we used the differing fields of view of the two instruments to extract spatial information. We found some evidence of cool gas in the outskirts of clusters, which may indicate that the nominally isothermal mass density distributions in these clusters are steepening in the outer parts of these clusters.

  3. A study of cooling flows in poor clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Kriss, Gerard A.; Dillingham, Stephen

    1995-01-01

    We observed three poor clusters with central dominant galaxies (AWM 4, MKW 4, and MKW 3's) using the Position Sensitive Proportional Counter on the ROSAT X-ray satellite. The images reveal smooth, symmetrical X-ray emission filling the cluster with a sharp peak on each central galaxy. The cluster surface brightness profiles can be decomposed using superposed King models for the central galaxy and the intracluster medium. The King model parameters for the cluster portions are consistent with previous observations of these clusters. The newly measured King model parameters for the central galaxies are typical of the X-ray surface brightness distributions of isolated elliptical galaxies. Spatially resolved temperature measurements in annular rings throughout the clusters show a nearly isothermal profile. Temperatures are consistent with previously measured values, but are much better determined. There is no significant drop in temperature noted in the innermost bins where cooling flows are likely to be present, nor is any excess absorption by cold gas required. All cold gas columns are consistent with galactic foreground absorption. We derive mass profiles for the clusters assuming both isothermal temperature profiles and cooling flow models with constant mass flow rates. Our results are consistent with previous Einstein IPC observations by Kriss, Cioffi, & Canizares, but extend the mass profiles out to 1 Mpc in these poor clusters.

  4. A study of cooling flows in poor clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Kriss, Gerard A.; Dillingham, Stephen

    1995-08-01

    We observed three poor clusters with central dominant galaxies (AWM 4, MKW 4, and MKW 3's) using the Position Sensitive Proportional Counter on the ROSAT X-ray satellite. The images reveal smooth, symmetrical X-ray emission filling the cluster with a sharp peak on each central galaxy. The cluster surface brightness profiles can be decomposed using superposed King models for the central galaxy and the intracluster medium. The King model parameters for the cluster portions are consistent with previous observations of these clusters. The newly measured King model parameters for the central galaxies are typical of the X-ray surface brightness distributions of isolated elliptical galaxies. Spatially resolved temperature measurements in annular rings throughout the clusters show a nearly isothermal profile. Temperatures are consistent with previously measured values, but are much better determined. There is no significant drop in temperature noted in the innermost bins where cooling flows are likely to be present, nor is any excess absorption by cold gas required. All cold gas columns are consistent with galactic foreground absorption. We derive mass profiles for the clusters assuming both isothermal temperature profiles and cooling flow models with constant mass flow rates. Our results are consistent with previous Einstein IPC observations by Kriss, Cioffi, & Canizares, but extend the mass profiles out to 1 Mpc in these poor clusters.

  5. H I absorption toward cooling flows in clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Mcnamara, Brian R.; O'Connell, Robert W.; Bregman, Joel N.

    1990-01-01

    An H I survey of 14 cooling flow clusters and two noncooling flow clusters was conducted, and H I absorption features were detected against the nuclear radio continuum sources of two cooling flow dominant (CFD) galaxies, 2A 0335 + 096 and MKW3s. The absorption features are broad and redshifted with respect to the stellar absorption-line velocity of the CFDs by 90-225 km/s. This indicates that the H I is falling onto, and is probably gravitationally bound to, the CFDs. The kinematics of the H I clouds suggest a possible kinematic link between the warm and cold phases of the intracluster medium. The clouds are orders of magnitude smaller in radius and mass and larger in density than Galactic H I clouds. The detected CFDs have mass-accretion rates that are about 2.5 times larger than the CFDs that were not detected.

  6. Thermal conduction and reduced cooling flows in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Voigt, L. M.; Fabian, A. C.

    2004-02-01

    Conduction may play an important role in reducing cooling flows in galaxy clusters. We analyse a sample of 16 objects using Chandra data and find that a balance between electron conduction and cooling can exist in the hotter clusters (T>~ 5 keV), provided that the plasma conductivity is close to the unhindered Spitzer value. In the absence of any additional heat sources, a reduced mass inflow must then develop in the cooler objects in the sample. We fit cooling flow models to deprojected spectra and compare the spectral mass deposition rates found to the values required to account for the excess luminosity, assuming Spitzer-rate heat transfer over the observed temperature gradients. The measured mass inflow rates are insufficient to maintain energy balance in at least five clusters. However, emission from cooling gas may be partially absorbed. We also compute the flux supplied by turbulent heat transport and find conductivity profiles that follow a strikingly similar temperature dependence to the conductivity values required to prevent cooling. The larger-scale turbulent motions implied by this process are required to have velocities of between 10 and 50 per cent of the speed of sound in the local intracluster gas.

  7. Heat conduction in cooling flows. [in clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Bregman, Joel N.; David, L. P.

    1988-01-01

    It has been suggested that electron conduction may significantly reduce the accretion rate (and star foramtion rate) for cooling flows in clusters of galaxies. A numerical hydrodynamics code was used to investigate the time behavior of cooling flows with conduction. The usual conduction coefficient is modified by an efficiency factor, mu, to realize the effects of tangled magnetic field lines. Two classes of models are considered, one where mu is independent of position and time, and one where inflow stretches the field lines and changes mu. In both cases, there is only a narrow range of initial conditions for mu in which the cluster accretion rate is reduced while a significant temperature gradient occurs. In the first case, no steady solution exists in which both conditions are met. In the second case, steady state solutions occur in which both conditions are met, but only for a narrow range of initial values where mu = 0.001.

  8. EVIDENCE FOR RAPID REDSHIFT EVOLUTION OF STRONG CLUSTER COOLING FLOWS

    SciTech Connect

    Samuele, R.; McNamara, B. R.; Vikhlinin, A.; Mullis, C. R.

    2011-04-10

    We present equivalent widths of the [O II]{lambda}3727 and H{alpha} nebular emission lines for 77 brightest cluster galaxies (BCGs) selected from the 160 Square Degree ROSAT X-ray survey. We find no [O II]{lambda}3727 or H{alpha} emission stronger than -15 A or -5 A, respectively, in any BCG. The corresponding emission-line luminosities lie below L {approx} 6 x 10{sup 40} erg s{sup -1}, which is a factor of 30 below that of NGC 1275 in the Perseus Cluster. A comparison to the detection frequency of nebular emission in BCGs at z {approx}< 0.35 drawn from the Brightest Cluster Survey indicates that we should have detected roughly one dozen emission-line galaxies, assuming that the two surveys are selecting similar clusters in the X-ray luminosity range 10{sup 42} erg s{sup -1} to 5 x 10{sup 44} erg s{sup -1}. The absence of luminous nebular emission (i.e., Perseus-like systems) in our sample is consistent with an increase in the number density of strong cooling flow (cooling core) clusters between z = 0.5 and today. The decline in their numbers at higher redshift could be due to cluster mergers and heating by active galactic nuclei.

  9. SPIRAL FLOWS IN COOL-CORE GALAXY CLUSTERS

    SciTech Connect

    Keshet, Uri

    2012-07-10

    We argue that bulk spiral flows are ubiquitous in the cool cores (CCs) of clusters and groups of galaxies. Such flows are gauged by spiral features in the thermal and chemical properties of the intracluster medium, by the multiphase properties of CCs, and by X-ray edges known as cold fronts. We analytically show that observations of piecewise-spiral fronts impose strong constraints on the CC, implying the presence of a cold, fast flow, which propagates below a hot, slow inflow, separated by a slowly rotating, trailing, quasi-spiral, tangential discontinuity surface. This leads to the nearly logarithmic spiral pattern, two-phase plasma, {rho} {approx} r{sup -1} density (or T {approx} r{sup 0.4} temperature) radial profile, and {approx}100 kpc size, characteristic of CCs. By advecting heat and mixing the gas, such flows can eliminate the cooling problem, provided that a feedback mechanism regulates the flow. In particular, we present a quasi-steady-state model for an accretion-quenched, composite flow, in which the fast phase is an outflow, regulated by active galactic nucleus bubbles, reproducing the observed low star formation rates and explaining some features of bubbles such as their R{sub b} {proportional_to}r size. The simplest two-component model reproduces several key properties of CCs, so we propose that all such cores harbor a spiral flow. Our results can be tested directly in the next few years, for example by ASTRO-H.

  10. Color gradients in cooling flows in clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Mcnamara, Brian R.; O'Connell, Robert W.

    1992-01-01

    U-, b-, V-, and I-band CCD images of 19 centrally dominant galaxies were obtained in cooling-flow clusters (CFDs) and four centrally dominant galaxies in clusters without cooling flows. Photometry through synthetic elliptical apertures was used to determine that many CFDs exhibit color-profile anomalies with respect to the control sample and to gE photometry from the recent literature. The anomalies are stronger and extend to larger galactic radii for higher mass accretion rates (HMARs) as estimated from X-ray observations. At least 11 CFDs with HMARs greater than or approximately equal to 70 solar masses/yr have blue color-profile anomalies that extend radially 5-20 kpc. Some CFDs with smaller HMARs have milder anomalies extending only less than or approximately equal to 5 kpc. The prevalence of color anomalies suggests that star formation which includes massive blue stars occurs continuously for a substantial fraction of the Hubble time, or in frequent episodes.

  11. A cooling flow cluster at redshift z = 0.2

    NASA Technical Reports Server (NTRS)

    Wolter, Anna; Schild, R.; Gioia, I. M.; Maccacaro, T.; Morris, S. L.; Nesci, R.; Perola, G. C.

    1990-01-01

    The cluster of galaxies 1E0839.9 + 2938, discovered in X-ray observations by Nesci et al. (1988), is characterized on the basis of VLA 6-cm radio observations, Whipple Observatory CCD photometry, and spectroscopic observations obtained with the Multiple Mirror Telescope and the 88-inch University of Hawaii Telescope at Mauna Kea. The data are presented in tables, maps, and sample images and spectra and briefly characterized. The bright X-ray object is identified with a cluster at redshift z = 0.195; its central galaxy has radio emission of 1.1 x 10 exp 24 W/Hz as well as strong optical line emission which is not restricted to its nucleus. It is concluded that 1E0839.9 + 2938 is a cooling-flow cluster similar to 3C295 (found at z = 0.461 by Henry et al., 1986). The need for space observations (by Rosat or the AXAF) to determine the object's X-ray luminosity distribution is indicated.

  12. Star formation in cooling flows in clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Mcnamara, Brian R.; O'Connell, Robert W.

    1989-01-01

    Spectrophotometry (wavelength = 3400-5100 A) has been obtained for the nuclei of 13 cD galaxies in cooling flows. Spectral anomalies are found in 8 of the objects, consisting of abnormally strong forbidden O II emission or excess flux effects. Consideration is given to metallicity effects, the relationship between UV excesses and the presence of massive OB stars formed from the cooling flows, and low-level effects related to accretion.

  13. A massive, cooling-flow-induced starburst in the core of a luminous cluster of galaxies.

    PubMed

    McDonald, M; Bayliss, M; Benson, B A; Foley, R J; Ruel, J; Sullivan, P; Veilleux, S; Aird, K A; Ashby, M L N; Bautz, M; Bazin, G; Bleem, L E; Brodwin, M; Carlstrom, J E; Chang, C L; Cho, H M; Clocchiatti, A; Crawford, T M; Crites, A T; de Haan, T; Desai, S; Dobbs, M A; Dudley, J P; Egami, E; Forman, W R; Garmire, G P; George, E M; Gladders, M D; Gonzalez, A H; Halverson, N W; Harrington, N L; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Jones, C; Joy, M; Keisler, R; Knox, L; Lee, A T; Leitch, E M; Liu, J; Lueker, M; Luong-Van, D; Mantz, A; Marrone, D P; McMahon, J J; Mehl, J; Meyer, S S; Miller, E D; Mocanu, L; Mohr, J J; Montroy, T E; Murray, S S; Natoli, T; Padin, S; Plagge, T; Pryke, C; Rawle, T D; Reichardt, C L; Rest, A; Rex, M; Ruhl, J E; Saliwanchik, B R; Saro, A; Sayre, J T; Schaffer, K K; Shaw, L; Shirokoff, E; Simcoe, R; Song, J; Spieler, H G; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Stubbs, C W; Suhada, R; van Engelen, A; Vanderlinde, K; Vieira, J D; Vikhlinin, A; Williamson, R; Zahn, O; Zenteno, A

    2012-08-16

    In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.

  14. ANISOTROPIC THERMAL CONDUCTION AND THE COOLING FLOW PROBLEM IN GALAXY CLUSTERS

    SciTech Connect

    Parrish, Ian J.; Sharma, Prateek; Quataert, Eliot

    2009-09-20

    We examine the long-standing cooling flow problem in galaxy clusters with three-dimensional magnetohydrodynamics simulations of isolated clusters including radiative cooling and anisotropic thermal conduction along magnetic field lines. The central regions of the intracluster medium (ICM) can have cooling timescales of {approx}200 Myr or shorter-in order to prevent a cooling catastrophe the ICM must be heated by some mechanism such as active galactic nucleus feedback or thermal conduction from the thermal reservoir at large radii. The cores of galaxy clusters are linearly unstable to the heat-flux-driven buoyancy instability (HBI), which significantly changes the thermodynamics of the cluster core. The HBI is a convective, buoyancy-driven instability that rearranges the magnetic field to be preferentially perpendicular to the temperature gradient. For a wide range of parameters, our simulations demonstrate that in the presence of the HBI, the effective radial thermal conductivity is reduced to {approx}<10% of the full Spitzer conductivity. With this suppression of conductive heating, the cooling catastrophe occurs on a timescale comparable to the central cooling time of the cluster. Thermal conduction alone is thus unlikely to stabilize clusters with low central entropies and short central cooling timescales. High central entropy clusters have sufficiently long cooling times that conduction can help stave off the cooling catastrophe for cosmologically interesting timescales.

  15. X-ray-emitting filaments in the cooling flow cluster A2029

    NASA Technical Reports Server (NTRS)

    Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

    1992-01-01

    High-resolution X-ray observations of the cluster A2029 are presented which confirm the presence of a cooling flow, despite the lack of optical line emission or evidence for recent star formation. The cooling rate and radius are about 370 solar mass/yr and 230 kpc, respectively. Emission from the inner cooling flow is dominated by a number of X-ray-emitting filaments. This may be the first case where such inhomogeneities are clearly resolved. The filaments are theorized to be supported in part by magnetic fields and may be connected with the filaments of very strong Faraday rotation seen in several nearly cooling flows.

  16. On the Origin of the Extended Hα Filaments in Cooling Flow Clusters

    NASA Astrophysics Data System (ADS)

    McDonald, Michael; Veilleux, Sylvain; Rupke, David S. N.; Mushotzky, Richard

    2010-10-01

    We present a high spatial resolution Hα survey of 23 cooling flow clusters using the Maryland Magellan Tunable Filter, covering 1-2 orders of magnitude in cooling rate, dM/dt, temperature, and entropy. We find that 8/23 (35%) of our clusters have complex, filamentary morphologies at Hα, while an additional 7/23 (30%) have marginally extended or nuclear Hα emission, in general agreement with previous studies of line emission in cooling flow cluster brightest cluster galaxies. A weak correlation between the integrated near-UV luminosity and the Hα luminosity is also found for our complete sample with a large amount of scatter about the expected relation for photoionization by young stars. We detect Hα emission out to the X-ray cooling radius, but no further, in several clusters and find a strong correlation between the Hα luminosity contained in filaments and the X-ray cooling flow rate of the cluster, suggesting that the warm ionized gas is linked to the cooling flow. Furthermore, we detect a strong enhancement in the cooling properties of the intracluster medium (ICM) coincident with the Hα emission, compared to the surrounding ICM at the same radius. While the filaments in a few clusters may be entrained by buoyant radio bubbles, in general, the radially infalling cooling flow model provides a better explanation for the observed trends. The correlation of the Hα and X-ray properties suggests that conduction may be important in keeping the filaments ionized. The thinness of the filaments suggests that magnetic fields are an important part of channeling the gas and shielding it from the surrounding hot ICM.

  17. OT1_sveilleu_1: Cold Gas and Dust in the Filamentary Complexes of Cluster Cooling Flows

    NASA Astrophysics Data System (ADS)

    Veilleux, S.

    2010-07-01

    We propose to obtain deep PACS + SPIRE far-IR photometry and 2D PACS [C II] 158 um spectroscopy of 7 cooling-flow clusters with extended Halpha filaments to constrain the properties of the dust and cooling gas in these systems. Our targets are part of a large sample of clusters that were imaged at Halpha using the Maryland Magellan Tunable Filter (MMTF) as part of a comprehensive multiwavelength survey. The superb sensitivity and resolution of the MMTF data have uncovered, often for the very first time, spectacular filaments of warm ionized gas extending as far as 50 kpc from the cluster core. The origin and heating source of these filaments remains a mystery. Our MMTF images have served as a guide to extract on-filament X-ray and optical spectra for a large sample of clusters, leading to the discovery that the X-ray ICM is cooling at a highly accelerated rate in the vicinity of these filaments. This direct link between the warm and hot phases may be the first direct evidence for the purported cooling flow. Given the high FIR fluxes detected in cluster cores, it is possible that dust grain cooling plays an important role in the cooling flow process. However, it remains unclear whether the observed dust is associated with the warm filaments or limited to the center of the brightest cluster galaxy (BCG). Current key programs cannot address this question given their lack of information on the Halpha filaments. Our proposed Herschel observations of the 7 cooling-flows clusters from our sample with the most extended Halpha filaments will directly address this question and help us determine: a) the role of dust cooling in the cooling-flow process, b) whether the observed dust is associated with the BCG or the warm filaments, and c) whether gas is cooling below 10^4 K, the temperature probed by Halpha. Providing answers to these questions will improve our understanding of the cooling processes in galaxy clusters and constrain the role of heating processes, such as AGN

  18. Stirring Up the Pot: Can Cooling Flows in Galaxy Clusters be Quenched by Gas Sloshing?

    NASA Astrophysics Data System (ADS)

    ZuHone, J. A.; Markevitch, M.; Johnson, R. E.

    2010-07-01

    X-ray observations of clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts." In relaxed clusters with cool cores, these commonly observed edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. Such sloshing may provide a source of heat to the cluster core by mixing hot gas from the cluster outskirts with the cool-core gas. Using high-resolution N-body/Eulerian hydrodynamic simulations, we model gas sloshing in galaxy clusters initiated by mergers with subclusters. The simulations include merger scenarios with gas-filled and gasless subclusters. The effect of changing the viscosity of the intracluster medium is also explored, but heat conduction is assumed to be negligible. We find that sloshing can facilitate heat inflow to the cluster core, provided that there is a strong enough disturbance. Additionally, sloshing redistributes the gas in the cluster core, causing the gas to expand and decreasing the efficiency of radiative cooling. In adiabatic simulations, we find that sloshing can raise the entropy floor of the cluster core by nearly an order of magnitude in the strongest cases. If the ICM is viscous, the mixing of gases with different entropies is decreased and consequently the heat flux to the core is diminished. In simulations where radiative cooling is included, we find that although eventually a cooling flow develops, sloshing can prevent the significant buildup of cool gas in the core for times on the order of a Gyr for small disturbances and a few Gyr for large ones. If repeated encounters with merging subclusters sustain the sloshing of the central core gas, as is observed, this process can provide a relatively steady source of heat to the core, which can help prevent a significant cooling flow.

  19. STIRRING UP THE POT: CAN COOLING FLOWS IN GALAXY CLUSTERS BE QUENCHED BY GAS SLOSHING?

    SciTech Connect

    ZuHone, J. A.; Markevitch, M.; Johnson, R. E.

    2010-07-10

    X-ray observations of clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as 'cold fronts'. In relaxed clusters with cool cores, these commonly observed edges have been interpreted as evidence for the 'sloshing' of the core gas in the cluster's gravitational potential. Such sloshing may provide a source of heat to the cluster core by mixing hot gas from the cluster outskirts with the cool-core gas. Using high-resolution N-body/Eulerian hydrodynamic simulations, we model gas sloshing in galaxy clusters initiated by mergers with subclusters. The simulations include merger scenarios with gas-filled and gasless subclusters. The effect of changing the viscosity of the intracluster medium is also explored, but heat conduction is assumed to be negligible. We find that sloshing can facilitate heat inflow to the cluster core, provided that there is a strong enough disturbance. Additionally, sloshing redistributes the gas in the cluster core, causing the gas to expand and decreasing the efficiency of radiative cooling. In adiabatic simulations, we find that sloshing can raise the entropy floor of the cluster core by nearly an order of magnitude in the strongest cases. If the ICM is viscous, the mixing of gases with different entropies is decreased and consequently the heat flux to the core is diminished. In simulations where radiative cooling is included, we find that although eventually a cooling flow develops, sloshing can prevent the significant buildup of cool gas in the core for times on the order of a Gyr for small disturbances and a few Gyr for large ones. If repeated encounters with merging subclusters sustain the sloshing of the central core gas, as is observed, this process can provide a relatively steady source of heat to the core, which can help prevent a significant cooling flow.

  20. Cooling or Boiling? Cooling Flow Problem and MHD Instabilities in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Bogdanovic, Tamara; Reynolds, C. S.; Balbus, S. A.; Parrish, I. J.

    2010-03-01

    In recent years our understanding of the action of thermal conduction in the atmospheres such as the intercluster matter (ICM) is undergoing a revolution. It has been realized that thermal conduction can lead to magnetohydrodynamic (MHD) instabilities at all radii in the ICM of clusters and in such way affect the evolution of their thermodynamic properties. I will describe findings based on several global models of cooling core clusters in which we explored the role of heat conduction and heat flux buoyancy instability (HBI) on the evolution of these cores. Our main finding is that a cooling core in the aftermath of HBI cannot be rescued from the cooling catastrophe by thermal conduction alone, although its action can significantly delay the catastrophic core collapse. This is because HBI tends to wrap the lines of magnetic field onto spherical surfaces surrounding the cooling core and in such way greatly suppress further conductive heating along the lines of magnetic field. We speculate that in real clusters, the central AGN and possibly mergers play the role of "stirrers", periodically disrupting the azimuthal field structure and allowing thermal conduction to sporadically heat the core. Support for this project is provided by NASA through Einstein Postdoctoral Fellowship Award PF9-00061 and by the National Science Foundation under grant AST0908212.

  1. On VI Observations of Galaxy Clusters: Evidence for Modest Cooling Flows

    NASA Astrophysics Data System (ADS)

    Bregman, Joel N.; Fabian, A. C.; Miller, Eric D.; Irwin, Jimmy A.

    2006-05-01

    A prediction of the galaxy-cluster cooling flow model is that as gas cools from the ambient cluster temperature, emission lines are produced in gas at subsequently decreasing temperatures. Gas passing through 105.5 K emits in the lines of O VI λλ1032, 1035, and here we report a FUSE study of these lines in three cooling flow clusters, Abell 426, Abell 1795, and AWM 7. No emission was detected from AWM 7, but O VI is detected from the centers of Abell 426 and Abell 1795, and possibly to the south of the center in Abell 1795, where X-ray and optical emission line filaments lie. In Abell 426 these line luminosities imply a cooling rate of 32+/-6 Msolar yr-1 within the central r=6.2 kpc region, while for Abell 1795 the central cooling rate is 26+/-7 Msolar yr-1 (within r=22 kpc), and about 42+/-9 Msolar yr-1 including the southern pointing. Including other studies, three of six clusters have O VI emission, and they also have star formation as well as emission lines from 104 K gas. These observations are generally consistent with the cooling flow model, but at a rate closer to 30 Msolar yr-1 than to the originally suggested values of 102-10 3 Msolar yr-1.

  2. FUSE Observations of Warm Gas in the Cooling Flow Clusters A1795 and A2597

    NASA Technical Reports Server (NTRS)

    Oegerle, W. R.; Cowie, L.; Davidsen, A.; Hu, E.; Hutchings, J.; Murphy, E.; Sembach, K.; Woodgate, B.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present far-ultraviolet spectroscopy of the cores of the massive cooling flow clusters Abell 1795 and 2597 obtained with FUSE. As the intracluster gas cools through 3 x 10(exp 5)K, it should emit strongly in the O VI lambda(lambda)1032,1038 resonance lines. We report the detection of O VI (lambda)1032 emission in A2597, with a line flux of 1.35 +/- 0.35 x 10(exp -15) erg/sq cm s, as well as detection of emission from C III (lambda)977. A marginal detection of C III (lambda)977 emission is also reported for A1795. These observations provide evidence for a direct link between the hot (10(exp 7) K) cooling flow gas and the cool (10(exp 4) K) gas in the optical emission line filaments. Assuming simple cooling flow models, the O VI line flux in A2597 corresponds to a mass deposition rate of approx. 40 solar mass /yr within the central 36 kpc. Emission from O VI (lambda)1032 was not detected in A1795, with an upper limit of 1.5 x 10(exp -15) erg/sq cm s, corresponding to a limit on the mass cooling flow rate of M(28 kpc) less than 28M solar mass/ yr. We have considered several explanations for the lack of detection of O VI emission in A1795 and the weaker than expected flux in A2597, including extinction by dust in the outer cluster, and quenching of thermal conduction by magnetic fields. We conclude that a turbulent mixing model, with some dust extinction, could explain our O VI results while also accounting for the puzzling lack of emission by Fe(sub XVII) in cluster cooling flows.

  3. FUSE Observations of Cooling-Flow Gas in the Galaxy Clusters A1795 and A2597

    NASA Astrophysics Data System (ADS)

    Oegerle, W. R.; Cowie, L.; Davidsen, A.; Hu, E.; Hutchings, J.; Murphy, E.; Sembach, K.; Woodgate, B.

    2001-10-01

    We present far-ultraviolet spectroscopy of the cores of the massive cooling-flow clusters Abell 1795 and 2597, obtained with the Far Ultraviolet Spectroscopic Explorer. As the intracluster gas cools through 3×105 K, it should emit strongly in the O VI λλ1032, 1038 resonance lines. We report the detection of O VI λ1032 emission in A2597, with a line flux of (1.35+/-0.35)×10-15 ergs cm-2 s-1, as well as detection of emission from C III λ977. A marginal detection of C III λ977 emission is also reported for A1795. These observations provide evidence for a direct link between the hot (107 K) cooling-flow gas and the cool (104 K) gas in the optical emission line filaments. Assuming simple cooling-flow models, the O VI line flux in A2597 corresponds to a mass deposition rate of ~40 Msolar yr-1 within the central 36 kpc. Emission from O VI λ1032 was not detected in A1795, with an upper limit of 1.5×10-15 ergs cm-2 s-1, corresponding to a limit on the mass cooling-flow rate of M(28 kpc)<28 Msolar yr-1. We have considered several explanations for the lack of detection of O VI emission in A1795 and the weaker than expected flux in A2597, including extinction by dust in the outer cluster and quenching of thermal conduction by magnetic fields. We conclude that a turbulent mixing model, with some dust extinction, could explain our O VI results while also accounting for the puzzling lack of emission by Fe XVII in cluster cooling flows.

  4. Marriage à-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle

    NASA Astrophysics Data System (ADS)

    Milgrom, Mordehai

    2008-05-01

    I start with a brief introduction to MOND phenomenology and its possible roots in cosmology—a notion that may turn out to be the most far reaching aspect of MOND. Next I discuss the implications of MOND for the dark matter (DM) doctrine: MOND's successes imply that baryons determine everything. For DM this would mean that the puny tail of leftover baryons in galaxies wags the hefty DM dog. This has to occur in many intricate ways, and despite the haphazard construction history of galaxies—a very tall order. I then concentrate on galaxy clusters in light of MOND, which still requires some yet undetected cluster dark matter, presumably in some baryonic form (CBDM). This CBDM might contribute to the heating of the X-ray emitting gas and thus alleviate the cooling flow puzzle. MOND, qua theory of dynamics, does not directly enter the microphysics of the gas; however, it does force a new outlook on the role of DM in shaping the cluster gas dynamics: MOND tells us that the cluster DM is not cold dark matter, is not so abundant, and is not expected in galaxies; it is thus not subject to constraints on baryonic DM in galaxies. The mass in CBDM required in a whole cluster is, typically, similar to that in hot gas, but is rather more centrally concentrated, totally dominating the core. The CBDM contribution to the baryon budget in the universe is thus small. Its properties, deduced for isolated clusters, are consistent with the observations of the "bullet cluster". Its kinetic energy reservoir is much larger than that of the hot gas in the core, and would suffice to keep the gas hot for many cooling times. Heating can be effected in various ways depending on the exact nature of the CBDM, from very massive black holes to cool, compact gas clouds.

  5. Self-regulated cooling flows in elliptical galaxies and in cluster cores - Is exclusively low mass star formation really necessary?

    NASA Technical Reports Server (NTRS)

    Silk, J.; Djorgovski, S.; Wyse, R. F. G.; Bruzual A., G.

    1986-01-01

    A self-consistent treatment of the heating by supernovae associated with star formation in a spherically symmetric cooling flow in a cluster core or elliptical galaxy is presented. An initial stellar mass function similar to that in the solar neighborhood is adopted. Inferred star-formation rates, within the cooling region - typically the inner 100 kpc around dominant galaxies at the centers of cooling flows in XD clusters - are reduced by about a factor of 2, relative to rates inferred when the heat input from star formation is ignored. Truncated initial mass functions (IMFs) are also considered, in which massive star formation is suppressed in accordance with previous treatments, and colors are predicted for star formation in cooling flows associated with central dominant elliptical galaxies and with isolated elliptical galaxies surrounded by gaseous coronae. The low inferred cooling-flow rates around isolated elliptical galaxies are found to be insensitive to the upper mass cutoff in the IMF, provided that the upper mass cutoff exceeds 2 M solar mass. Comparison with observed colors favors a cutoff in the IMF above 1 M solar mass in at least two well-studied cluster cooling flows, but a normal IMF cannot be excluded definitively. Models for NGC 1275 support a young (less than about 3 Gyr) cooling flow. As for the isolated elliptical galaxies, the spread in colors is consistent with a normal IMF. A definitive test of the IMF arising via star formation in cooling flows requires either UV spectral data or supernova searches in the cooling-flow-centered galaxies.

  6. Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data

    NASA Astrophysics Data System (ADS)

    Hicks, A. K.; Mushotzky, R.

    2005-12-01

    We have analyzed XMM-Newton Optical Monitor UV (180-400 nm) data for a sample of 33 galaxies. Thirty are cluster member galaxies, and nine are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates between 8 and 525 Msolar yr-1. By comparing the ratio of UV to 2MASS J-band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, consistent with several previous studies based on optical imaging data (McNamara & O'Connell Cardiel et al.; Crawford et al.). This UV excess is a direct indication of the presence of young massive stars and, therefore, recent star formation. Using the Starburst99 model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2-219 Msolar yr-1 for the cooling flow sample. For two-thirds of this sample, it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV-inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well-populated XMM UV cluster archive, and a more extensive follow-up study is currently underway.

  7. Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data

    NASA Technical Reports Server (NTRS)

    Hicks, A. K.; Mushotzky, R.

    2005-01-01

    We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a sample of 33 galaxies. 30 are cluster member galaxies, and nine of these are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates which span a range of 8 - 525 solar mass per year. By comparing the ratio of UV to 2MASS J band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, a finding consistent with the outcome of previous studies based on optical imaging data (McNamara & O Connell 1989; Cardiel, Gorgas, & Aragon-Salamanca 1998; Crawford et al. 1999). This UV excess is a direct indication of the presence of young massive stars, and therefore recent star formation, in these galaxies. Using the Starburst99 spectral energy distribution (SED) model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2 - 219 solar mass per year for the cooling flow sample. For 2/3 of this sample it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well populated XMM UV cluster archive and a more extensive follow up study is currently underway.

  8. Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data

    NASA Technical Reports Server (NTRS)

    Hicks, A. K.; Mushotzky, R.

    2006-01-01

    We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a sample of 33 galaxies. 30 are cluster member galaxies, and nine of these are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates which span a range of 8 - 525 Solar Mass/yr. By comparing the ratio of UV to 2MASS J band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, a finding consistent with the outcome of previous studies based on optical imaging data (McNamara & O'Connell 1989; Cardiel, Gorgas, & Aragon-Salamanca 1998; Crawford et al. 1999). This UV excess is a direct indication of the presence of young massive stars, and therefore recent star formation, in these galaxies. Using the Starburst99 spectral energy distribution (SED) model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2 - 219 solar Mass/yr for the cooling flow sample. For 2/3 of this sample it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well populated XMM UV cluster archive and a more extensive follow up study is currently underway.

  9. Analysis of Mass Profiles and Cooling Flows of Bright, Early-Type Galaxies AO2, AO3 and Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters AO3

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III

    1998-01-01

    This final report uses ROSAT observations to analyze two different studies. These studies are: Analysis of Mass Profiles and Cooling Flows of Bright, Early-Type Galaxies; and Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters.

  10. X-ray and optical emission-line filaments in the cooling flow cluster 2A 0335 + 096

    NASA Technical Reports Server (NTRS)

    Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

    1992-01-01

    We present a new high-resolution X-ray image of the 2A 0335 + 096 cluster of galaxies obtained with the High Resolution Imager (HRI) aboard the ROSAT satellite. The presence of dense gas having a very short cooling time in the central regions confirms its earlier identification as a cooling flow. The X-ray emission from the central regions of the cooling flow shows a great deal of filamentary structure. Using the crude spectral resolution of the HRI, we show that these filaments are the result of excess emission, rather than foreground X-ray absorption. Although there are uncertainties in the pointing, many of the X-ray features in the cooling flow region correspond to features in H-alpha optical line emission. This suggests that the optical emission line gas has resulted directly from the cooling of X-ray-emitting gas. The filament material cannot be in hydrostatic equilibrium, and it is likely that other forces such as rotation, turbulence, and magnetic fields influence the dynamical state of the gas.

  11. HIGH-RESOLUTION XMM-NEWTON SPECTROSCOPY OF THE COOLING FLOW CLUSTER A3112

    SciTech Connect

    Bulbul, G. Esra; Smith, Randall K.; Foster, Adam; Cottam, Jean; Loewenstein, Michael; Mushotzky, Richard; Shafer, Richard

    2012-03-01

    We examine high signal-to-noise XMM-Newton European Photon Imaging Camera (EPIC) and Reflection Grating Spectrometer (RGS) observations to determine the physical characteristics of the gas in the cool core and outskirts of the nearby rich cluster A3112. The XMM-Newton Extended Source Analysis Software data reduction and background modeling methods were used to analyze the XMM-Newton EPIC data. From the EPIC data, we find that the iron and silicon abundance gradients show significant increase toward the center of the cluster while the oxygen abundance profile is centrally peaked but has a shallower distribution than that of iron. The X-ray mass modeling is based on the temperature and deprojected density distributions of the intracluster medium determined from EPIC observations. The total mass of A3112 obeys the M-T scaling relations found using XMM-Newton and Chandra observations of massive clusters at r{sub 500}. The gas mass fraction f{sub gas} = 0.149{sup +0.036}{sub -0.032} at r{sub 500} is consistent with the seven-year Wilkinson Microwave Anisotropy Probe results. The comparisons of line fluxes and flux limits on the Fe XVII and Fe XVIII lines obtained from high-resolution RGS spectra indicate that there is no spectral evidence for cooler gas associated with the cluster with temperature below 1.0 keV in the central <38'' ({approx}52 kpc) region of A3112. High-resolution RGS spectra also yield an upper limit to the turbulent motions in the compact core of A3112 (206 km s{sup -1}). We find that the contribution of turbulence to total energy is less than 6%. This upper limit is consistent with the energy contribution measured in recent high-resolution simulations of relaxed galaxy clusters.

  12. Abundance gradients in cooling flow clusters: Ginga Large Area Counters and Einstein Solid State Spectrometer spectra of A496, A1795, A2142, and A2199

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III; Day, C. S. R.; Hatsukade, Isamu; Hughes, John P.

    1994-01-01

    We analyze the Ginga Large Area Counters (LAC) and Einstein Solid State Spectrometer (SSS) spectra of four cooling flow clusters, A496, A1795, A2142, and A2199, each of which shows firm evidence of a relatively cool component. The inclusion of such cool spectral components in joint fits of SSS and LAC data leads to somewhat higher global temperatures than are derived from the high-energy LAC data alone. We find little evidence of cool emission outside the SSS field of view. Metal abundances appear to be centrally enhanced in all four clusters, with varying degrees of model dependence and statistical significance: the evidence is statistically strongest for A496 and A2142, somewhat weaker for A2199 and weakest for A1795. We also explore the model dependence in the amount of cold, X-ray-absorbing matter discovered in these clusters by White et al.

  13. Cool Cluster Correctly Correlated

    SciTech Connect

    Varganov, Sergey Aleksandrovich

    2005-01-01

    Atomic clusters are unique objects, which occupy an intermediate position between atoms and condensed matter systems. For a long time it was thought that physical and chemical properties of atomic dusters monotonically change with increasing size of the cluster from a single atom to a condensed matter system. However, recently it has become clear that many properties of atomic clusters can change drastically with the size of the clusters. Because physical and chemical properties of clusters can be adjusted simply by changing the cluster's size, different applications of atomic clusters were proposed. One example is the catalytic activity of clusters of specific sizes in different chemical reactions. Another example is a potential application of atomic clusters in microelectronics, where their band gaps can be adjusted by simply changing cluster sizes. In recent years significant advances in experimental techniques allow one to synthesize and study atomic clusters of specified sizes. However, the interpretation of the results is often difficult. The theoretical methods are frequently used to help in interpretation of complex experimental data. Most of the theoretical approaches have been based on empirical or semiempirical methods. These methods allow one to study large and small dusters using the same approximations. However, since empirical and semiempirical methods rely on simple models with many parameters, it is often difficult to estimate the quantitative and even qualitative accuracy of the results. On the other hand, because of significant advances in quantum chemical methods and computer capabilities, it is now possible to do high quality ab-initio calculations not only on systems of few atoms but on clusters of practical interest as well. In addition to accurate results for specific clusters, such methods can be used for benchmarking of different empirical and semiempirical approaches. The atomic clusters studied in this work contain from a few atoms to

  14. Projection effects in X-ray cores of cooling flow galaxy clusters

    NASA Astrophysics Data System (ADS)

    Ettori, Stefano

    2002-03-01

    Recent analyses of Newton-XMM and Chandra data of the cores of X-ray bright clusters of galaxies show that modelling with a multi-phase gas in which several temperatures and densities are in equilibrium might not be appropriate. Instead, a single-phase model seems able to reproduce properly the spectra collected in annuli from the central region. The measured single-phase temperature profiles indicate a steep positive gradient in the central 100-200kpc and the gas density shows a flat profile in the central few 10s of kpc. Given this observational evidence, we estimate the contribution to the projected-on-the-sky rings from the cluster emissivity as function of the shell volume fraction sampled. We show that the observed projected X-ray emission mimics the multi-phase status of the plasma even though the input distribution is single-phase. This geometrical projection affects (i) analyses of data where insufficient spatial resolution is accessible, (ii) the central bin when its dimension is comparable to the extension of any flatness in the central gas density profile.

  15. Hot versus cold: The dichotomy in spherical accretion of cooling flows onto supermassive black holes in elliptical galaxies, galaxy groups, and clusters

    SciTech Connect

    Guo, Fulai; Mathews, William G.

    2014-01-10

    Feedback heating from active galactic nuclei (AGNs) has been commonly invoked to suppress cooling flows predicted in hot gas in elliptical galaxies, galaxy groups, and clusters. Previous studies have focused on if and how AGN feedback heats the gas but have little paid attention to its triggering mechanism. Using spherically symmetric simulations, we investigate how large-scale cooling flows are accreted by central supermassive black holes (SMBHs) in eight well-observed systems and find an interesting dichotomy. In massive clusters, the gas develops a central cooling catastrophe within about the cooling time (typically ∼100-300 Myr), resulting in cold-mode accretion onto SMBHs. However, in our four simulated systems on group and galaxy scales at a low metallicity Z = 0.3 Z {sub ☉}, the gas quickly settles into a long-term state that has a cuspy central temperature profile extending to several tens to about 100 pc. At the more realistic solar metallicity, two groups (with R {sub e} ∼ 4 kpc) still host the long-term, hot-mode accretion. Both accretion modes naturally appear in our idealized calculations where only cooling, gas inflow, and compressional heating are considered. The long-term, hot-mode accretion is maintained by the quickly established closeness between the timescales of these processes, preferably in systems with low gas densities, low gas metallicities, and importantly, compact central galaxies, which result in strong gravitational acceleration and compressional heating at the intermediate radii. Our calculations predict that central cuspy temperature profiles appear more often in smaller systems than galaxy clusters, which instead often host significant cold gas and star formation.

  16. Coma Cluster: Hot and Cool Mixture

    NASA Astrophysics Data System (ADS)

    Ishizaka, Chiharu; Mineshige, Shin

    1996-06-01

    ASCA has revealed a rather complex temperature structure in the intraclus ter medium (ICM) around the Coma cluster. Significantly, hot parts (with kT g eq 10 keV) are located far ( ~ 1 Mpc) distant from both the center of the Coma cluster and the galaxy group NGC 4839. There also exist relatively cool re gions (with kT <~ 5 keV). Using N-body + Hydrodynamic simulations, w e have demonstrated that such an observed temperature distribution is naturally accounted for if the subgroup NGC 4839 passed through the center of the Coma c luster about 1 Gyr ago, which was first proposed by Burns et al. When the subc luster passed through the Coma cluster, the ICM in the subcluster was compresse d due to the ram pressure by the ICM in the Coma, and there formed a bow shock with an arc shape just between the two centers. The ICM has thus been heated th ere, emitting hard radiation. A part of the ICM is reflected by the shock front , and flows backward (with respect to the! direction of the subcluster motio n) around the Coma cluster center, being cooled due to an adiabatic expansion. After detouring the center, cooled gas collides with each other at the opposit e side of the Coma cluster (to the place of the subcluster), producing another hot region. These simulate d features are in good agreement with what ASCA found. Further, we present rath er unique features in the temperature profiles that can be caused by a merger ( or an encounter) with a subgroup of galaxies.

  17. RADIATING BONDI AND COOLING SITE FLOWS

    SciTech Connect

    Mathews, William G.; Guo, Fulai

    2012-08-01

    Steady accretion of a radiating gas onto a central mass point is described and compared to classic Bondi accretion. Radiation losses are essential for accretion flows to be observed. Unlike Bondi flows, radiating Bondi flows pass through a sonic point at a finite radius and become supersonic near the center. The morphology of all radiating flows is described by a single dimensionless parameter proportional to M-dot /MT{sub s} where T{sub s} is the gas temperature at the sonic point. In radiating Bondi flows the relationship between the mass accretion rate and central mass, M-dot {proportional_to}M{sup p} with p {approx} 1, differs significantly from the quadratic dependence in classical Bondi flows, M-dot {proportional_to}M{sup 2}. Mass accretion rates onto galaxy or cluster-centered black holes estimated from traditional and radiating Bondi flows are significantly different. In radiating Bondi flows the gas temperature increases at large radii, as in the cores of many galaxy groups and clusters, allowing radiating Bondi flows to merge naturally with gas arriving from their cluster environments. Some radiating flows cool completely before reaching the center of the flow, and this also occurs in cooling site flows, in which there is no central gravitating mass.

  18. X-ray Spectroscopy of Cooling Cluster

    SciTech Connect

    Peterson, J.R.; Fabian, A.C.; /Cambridge U., Inst. of Astron.

    2006-01-17

    We review the X-ray spectra of the cores of clusters of galaxies. Recent high resolution X-ray spectroscopic observations have demonstrated a severe deficit of emission at the lowest X-ray temperatures as compared to that expected from simple radiative cooling models. The same observations have provided compelling evidence that the gas in the cores is cooling below half the maximum temperature. We review these results, discuss physical models of cooling clusters, and describe the X-ray instrumentation and analysis techniques used to make these observations. We discuss several viable mechanisms designed to cancel or distort the expected process of X-ray cluster cooling.

  19. COOL CORE CLUSTERS FROM COSMOLOGICAL SIMULATIONS

    SciTech Connect

    Rasia, E.; Borgani, S.; Murante, G.; Planelles, S.; Biffi, V.; Granato, G. L.; Beck, A. M.; Steinborn, L. K.; Dolag, K.; Ragone-Figueroa, C.

    2015-11-01

    We present results obtained from a set of cosmological hydrodynamic simulations of galaxy clusters, aimed at comparing predictions with observational data on the diversity between cool-core (CC) and non-cool-core (NCC) clusters. Our simulations include the effects of stellar and active galactic nucleus (AGN) feedback and are based on an improved version of the smoothed particle hydrodynamics code GADGET-3, which ameliorates gas mixing and better captures gas-dynamical instabilities by including a suitable artificial thermal diffusion. In this Letter, we focus our analysis on the entropy profiles, the primary diagnostic we used to classify the degree of cool-coreness of clusters, and the iron profiles. In keeping with observations, our simulated clusters display a variety of behaviors in entropy profiles: they range from steadily decreasing profiles at small radii, characteristic of CC systems, to nearly flat core isentropic profiles, characteristic of NCC systems. Using observational criteria to distinguish between the two classes of objects, we find that they occur in similar proportions in both simulations and observations. Furthermore, we also find that simulated CC clusters have profiles of iron abundance that are steeper than those of NCC clusters, which is also in agreement with observational results. We show that the capability of our simulations to generate a realistic CC structure in the cluster population is due to AGN feedback and artificial thermal diffusion: their combined action allows us to naturally distribute the energy extracted from super-massive black holes and to compensate for the radiative losses of low-entropy gas with short cooling time residing in the cluster core.

  20. Cooling, AGN Feedback, and Star Formation in Simulated Cool-core Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Bryan, Greg L.; Ruszkowski, Mateusz; Voit, G. Mark; O’Shea, Brian W.; Donahue, Megan

    2015-10-01

    Numerical simulations of active galactic nuclei (AGNs) feedback in cool-core galaxy clusters have successfully avoided classical cooling flows, but often produce too much cold gas. We perform adaptive mesh simulations that include momentum-driven AGN feedback, self-gravity, star formation, and stellar feedback, focusing on the interplay between cooling, AGN heating, and star formation in an isolated cool-core cluster. Cold clumps triggered by AGN jets and turbulence form filamentary structures tens of kpc long. This cold gas feeds both star formation and the supermassive black hole (SMBH), triggering an AGN outburst that increases the entropy of the intracluster medium (ICM) and reduces its cooling rate. Within 1–2 Gyr, star formation completely consumes the cold gas, leading to a brief shutoff of the AGN. The ICM quickly cools and redevelops multiphase gas, followed by another cycle of star formation/AGN outburst. Within 6.5 Gyr, we observe three such cycles. There is good agreement between our simulated cluster and the observations of cool-core clusters. ICM cooling is dynamically balanced by AGN heating, and a cool-core appearance is preserved. The minimum cooling time to free-fall time ratio typically varies between a few and ≳ 20. The star formation rate (SFR) covers a wide range, from 0 to a few hundred {M}ȯ {{yr}}-1, with an average of ∼ 40 {M}ȯ {{yr}}-1. The instantaneous SMBH accretion rate shows large variations on short timescales, but the average value correlates well with the SFR. Simulations without stellar feedback or self-gravity produce qualitatively similar results, but a lower SMBH feedback efficiency (0.1% compared to 1%) results in too many stars.

  1. Liquid cooled counter flow turbine bucket

    DOEpatents

    Dakin, James T.

    1982-09-21

    Means and a method are provided whereby liquid coolant flows radially outward through coolant passages in a liquid cooled turbine bucket under the influence of centrifugal force while in contact with countercurrently flowing coolant vapor such that liquid is entrained in the flow of vapor resulting in an increase in the wetted cooling area of the individual passages.

  2. Wavy flow cooling concept for turbine airfoils

    DOEpatents

    Liang, George

    2010-08-31

    An airfoil including an outer wall and a cooling cavity formed therein. The cooling cavity includes a leading edge flow channel located adjacent a leading edge of the airfoil and a trailing edge flow channel located adjacent a trailing edge of the airfoil. Each of the leading edge and trailing edge flow channels define respective first and second flow axes located between pressure and suction sides of the airfoil. A plurality of rib members are located within each of the flow channels, spaced along the flow axes, and alternately extending from opposing sides of the flow channels to define undulating flow paths through the flow channels.

  3. Modeling active galactic nucleus feedback in cool-core clusters: The balance between heating and cooling

    SciTech Connect

    Li, Yuan; Bryan, Greg L.

    2014-07-01

    We study the long-term evolution of an idealized cool-core galaxy cluster under the influence of momentum-driven active galactic nucleus (AGN) feedback using three-dimensional high-resolution (60 pc) adaptive mesh refinement simulations. The feedback is modeled with a pair of precessing jets whose power is calculated based on the accretion rate of the cold gas surrounding the supermassive black hole (SMBH). The intracluster medium first cools into clumps along the propagation direction of the jets. As the jet power increases, gas condensation occurs isotropically, forming spatially extended structures that resemble the observed Hα filaments in Perseus and many other cool-core clusters. Jet heating elevates the gas entropy, halting clump formation. The cold gas that is not accreted onto the SMBH settles into a rotating disk of ∼10{sup 11} M {sub ☉}. The hot gas cools directly onto the disk while the SMBH accretes from its innermost region, powering the AGN that maintains a thermally balanced state for a few Gyr. The mass cooling rate averaged over 7 Gyr is ∼30 M {sub ☉} yr{sup –1}, an order of magnitude lower than the classic cooling flow value. Medium resolution simulations produce similar results, while in low resolution runs, the cluster experiences cycles of gas condensation and AGN outbursts. Owing to its self-regulating mechanism, AGN feedback can successfully balance cooling with a wide range of model parameters. Our model also produces cold structures in early stages that are in good agreement with the observations. However, the long-lived massive cold disk is unrealistic, suggesting that additional physical processes are still needed.

  4. Alternatives to the existence of large cooling flows

    NASA Technical Reports Server (NTRS)

    Tucker, Wallace

    1990-01-01

    Arguments against the existence of large-scale cooling flows in clusters of galaxies are presented. The evidence for cooling flows is all circumstantial, consisting of observations of cool gas or hot gas with a radiative cooling time less than the Hubble time, or a central peak in the X-ray surface brightness profile. There is no evidence for large quantities (several tens to several hundreds of solar masses per year) of matter actually flowing anywhere. On the contrary, several lines of evidence suggest thaat cooling flows, if they exist, must be suppressed by one to two orders of magnitude from the values implied by simple estimates based on the radiative cooling time of the X-ray emitting gas. Two heat sources which might accomplish this, thermal conduction and relativistic particles, are considered, and an alternative to the standard model for cooling flows is presented: an accretion flow with feedback wherein the accretion of gas into a massive black hole in the central galaxy generates high energy particles that heat the gas and act to limit the accretion.

  5. The Properties of Cold Clouds in Cooling Flows

    NASA Astrophysics Data System (ADS)

    Daines, S. J.; Fabian, A. C.; Thomas, P. A.

    1994-06-01

    We discuss the properties of the large masses of cold gas found in the central regions of cooling flow clusters via X-ray absorption, and explore some consequences of inefficient star formation in cooling flows. The X-ray-absorbing cold gas must be in the form of small, cold, pressure-confined clouds, whIch are supported against infall in the cluster potential by the hot, X-ray-emitting gas ad approximately comove with it. Magnetic fields are important in supporting ad containing the clouds. Cold gas deposited at large radii in the cooling flow may simply accumulate and have negligible star formation; the inner regions of the cooling flow accumulate dynamically dominant masses of cold gas on a short time-scale and some gas-removal process must be operating. We show that the constraints placed by observational detections and limits of H I ad CO in some flows leave little room there for widespread cold gas in a form which is either atomic or similar to Galactic molecular clouds. Ongoing cluster mergers, or stirring produced by a intermittent central radio source, disrupt accumulated cold clouds in the core of a flow and release enough kinetic or thermal energy via cloud collisions or mixing layers to power transiently the optical emission-line nebulosity around central cluster galaxies. The large masses of disordered clumpy, turbulent atomic gas observed near the centre of the Perseus cluster via 21-cm absorption have probably been stirred up by such an event in the past few billion years.

  6. HUBBLE SPACE TELESCOPE FAR-ULTRAVIOLET OBSERVATIONS OF BRIGHTEST CLUSTER GALAXIES: THE ROLE OF STAR FORMATION IN COOLING FLOWS AND BCG EVOLUTION

    SciTech Connect

    O'Dea, Kieran P.; Quillen, Alice C.; O'Dea, Christopher P.; Tremblay, Grant R.; Snios, Bradford T.; Baum, Stefi A.; Christiansen, Kevin; Noel-Storr, Jacob; Edge, Alastair C.; Donahue, Megan; Voit, G. Mark

    2010-08-20

    Quillen et al. and O'Dea et al. carried out a Spitzer study of a sample of 62 brightest cluster galaxies (BCGs) from the ROSAT brightest cluster sample, which were chosen based on their elevated H{alpha} flux. We present Hubble Space Telescope Advanced Camera for Surveys far-ultraviolet (FUV) images of the Ly{alpha} and continuum emission of the luminous emission-line nebulae in seven BCGs found to have an infrared (IR) excess. We confirm that the BCGs are actively forming stars which suggests that the IR excess seen in these BCGs is indeed associated with star formation. Our observations are consistent with a scenario in which gas that cools from the intracluster medium fuels the star formation. The FUV continuum emission extends over a region {approx}7-28 kpc (largest linear size) and even larger in Ly{alpha}. The young stellar population required by the FUV observations would produce a significant fraction of the ionizing photons required to power the emission-line nebulae. Star formation rates estimated from the FUV continuum range from {approx}3 to {approx}14 times lower than those estimated from the IR, however, both the Balmer decrements in the central few arcseconds and detection of CO in most of these galaxies imply that there are regions of high extinction that could have absorbed much of the FUV continuum. Analysis of archival Very Large Array observations reveals compact radio sources in all seven BCGs and kpc scale jets in A-1835 and RXJ 2129+00. The four galaxies with archival deep Chandra observations exhibit asymmetric X-ray emission, the peaks of which are offset from the center of the BCG by {approx}10 kpc on average. A low feedback state for the active galactic nucleus could allow increased condensation of the hot gas into the center of the galaxy and the feeding of star formation.

  7. The initial cooling of pahoehoe flow lobes

    USGS Publications Warehouse

    Keszthelyi, L.; Denlinger, R.

    1996-01-01

    In this paper we describe a new thermal model for the initial cooling of pahoehoe lava flows. The accurate modeling of this initial cooling is important for understanding the formation of the distinctive surface textures on pahoehoe lava flows as well as being the first step in modeling such key pahoehoe emplacement processes as lava flow inflation and lava tube formation. This model is constructed from the physical phenomena observed to control the initial cooling of pahoehoe flows and is not an empirical fit to field data. We find that the only significant processes are (a) heat loss by thermal radiation, (b) heat loss by atmospheric convection, (c) heat transport within the flow by conduction with temperature and porosity-dependent thermal properties, and (d) the release of latent heat during crystallization. The numerical model is better able to reproduce field measurements made in Hawai'i between 1989 and 1993 than other published thermal models. By adjusting one parameter at a time, the effect of each of the input parameters on the cooling rate was determined. We show that: (a) the surfaces of porous flows cool more quickly than the surfaces of dense flows, (b) the surface cooling is very sensitive to the efficiency of atmospheric convective cooling, and (c) changes in the glass forming tendency of the lava may have observable petrographic and thermal signatures. These model results provide a quantitative explanation for the recently observed relationship between the surface cooling rate of pahoehoe lobes and the porosity of those lobes (Jones 1992, 1993). The predicted sensitivity of cooling to atmospheric convection suggests a simple field experiment for verification, and the model provides a tool to begin studies of the dynamic crystallization of real lavas. Future versions of the model can also be made applicable to extraterrestrial, submarine, silicic, and pyroclastic flows.

  8. AGN Feedback and Cooling Flows: Problems with Simple Hydrodynamic Models

    NASA Astrophysics Data System (ADS)

    Vernaleo, John C.; Reynolds, Christopher S.

    2006-07-01

    In recent years it has become increasingly clear that active galactic nuclei, and radio galaxies in particular, have an impact on large-scale structure and galaxy formation. In principle, radio galaxies are energetic enough to halt the cooling of the virialized intracluster medium (ICM) in the inner regions of galaxy clusters, solving the cooling flow problem and explaining the high-mass truncation of the galaxy luminosity function. We explore this process through a series of high-resolution, three-dimensional hydrodynamic simulations of jetted active galaxies that act in response to cooling-mediated accretion of an ICM atmosphere. We find that our models are incapable of producing a long-term balance of heating and cooling; catastrophic cooling can be delayed by the jet action but inevitably takes hold. At the heart of the failure of these models is the formation of a low-density channel through which the jet can freely flow, carrying its energy out of the cooling core. It is possible that this failure is due to an oversimplified treatment of the fast jet (which may underestimate the ``dentist drill'' effect). However, it seems likely that additional complexity (large-angle jet precession or ICM turbulence) or additional physics (magnetohydrodynamic effects and plasma transport processes) is required to produce a spatial distribution of jet heating that can prevent catastrophic cooling. This work also underscores the importance of including jet dynamics in any feedback model, as opposed to the isotropically inflated bubble approach taken in some previous works.

  9. Magnetorotational instability in cool cores of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Nipoti, Carlo; Posti, L.; Ettori, S.; Bianconi, M.

    2015-10-01

    > Clusters of galaxies are embedded in halos of optically thin, gravitationally stratified, weakly magnetized plasma at the system's virial temperature. Owing to radiative cooling and anisotropic heat conduction, such intracluster medium (ICM) is subject to local instabilities, which are combinations of the thermal, magnetothermal and heat-flux-driven buoyancy instabilities. If the ICM rotates significantly, its stability properties are substantially modified and, in particular, also the magnetorotational instability (MRI) can play an important role. We study simple models of rotating cool-core clusters and we demonstrate that the MRI can be the dominant instability over significant portions of the clusters, with possible implications for the dynamics and evolution of the cool cores. Our results give further motivation for measuring the rotation of the ICM with future X-ray missions such as ASTRO-H and ATHENA.

  10. Decay processes and radiative cooling of small anionic copper clusters

    NASA Astrophysics Data System (ADS)

    Breitenfeldt, Christian; Blaum, Klaus; Froese, Michael W.; George, Sebastian; Guzmán-Ramírez, Gregorio; Lange, Michael; Menk, Sebastian; Schweikhard, Lutz; Wolf, Andreas

    2016-09-01

    The decay of copper clusters Cun- with size n =4 -7 , produced in a metal ion sputter source, was studied in an electrostatic ion-beam trap. The neutral products after electron emission and fragmentation were monitored for ion storage times of up to a second. The observations indicated the presence of radiative cooling. The energy distributions of the remaining clusters were probed by laser irradiation up to several further seconds of storage time. This defined excitation lead to photoinduced decay signals which, again, showed signs of radiative cooling for Cu6,7 -, not, however, for Cu4,5 -.

  11. Lava Flows Cooling: The initial hypothesis

    NASA Astrophysics Data System (ADS)

    Cordonnier, B.; Self, S.; Manga, M.

    2013-12-01

    Many cooling models of lava have one precondition: an instantaneous-thick layer emplacement with a spatially uniform temperature, often as high as the effusion temperature. The cooling is then mostly controlled by conduction and is a function of the thermal parameters and dimensions of the lava flow (most important being thickness). However, many lavas, especially pahoehoe and compound lavas, are not directly emplaced with an established lava thickness but, rather, inflate from their core or result from piling-up of several layers, respectively. In both cases, this leads initially to thin fast-cooling lavas in which the final emplacement temperature may differ strongly from the initial temperature of the liquid lava feeding the flow. Here we investigate both the behavior of inflating flows and superposition layering of lava. With a modified Peclet Number (Pe), where the velocity has been replaced by the inflation rate, we identify the conditions where lavas lose the most of their thermal energy before the final thickness is reached. For a given growth rate, inflating flows are hotter than those that grow through superposition. In the latter case, temperature depends not only with Pe, but also on the discrete lava-layer thickness. A clear quantification of the energy loss during these processes has been established and demonstrates the impact of each of them on the temperature of emplacement. Apart from this simple point, our study raises the question of lava-flow morphology. The two processes described, despite having opposite thermal effects, may be coupled during a single eruptive event. When a lava reaches its emplacement temperature and stops, then the pressing material uphill starts to bifurcate, turn around or superpose the previously emplaced layer. Our Peclet number could be again modified to consider the traditional emplacement condition of a Graetz number of 300. Beyond this point, the inflating process turns into a superposing process and the conditions

  12. Counter-Flow Cooling Tower Test Cell

    NASA Astrophysics Data System (ADS)

    Dvořák, Lukáš; Nožička, Jiří

    2014-03-01

    The article contains a design of a functional experimental model of a cross-flow mechanical draft cooling tower and the results and outcomes of measurements. This device is primarily used for measuring performance characteristics of cooling fills, but with a simple rebuild, it can be used for measuring other thermodynamic processes that take part in so-called wet cooling. The main advantages of the particular test cell lie in the accuracy, size, and the possibility of changing the water distribution level. This feature is very useful for measurements of fills of different heights without the influence of the spray and rain zone. The functionality of this test cell has been verified experimentally during assembly, and data from the measurement of common film cooling fills have been compared against the results taken from another experimental line. For the purpose of evaluating the data gathered, computational scripts were created in the MATLAB numerical computing environment. The first script is for exact calculation of the thermal balance of the model, and the second is for determining Merkel's number via Chebyshev's method.

  13. Heat conduction boundary layers of condensed clumps in cooling flows

    NASA Astrophysics Data System (ADS)

    Boehringer, H.; Fabian, A. C.

    1989-04-01

    The structure of heat conduction boundary layers of gaseous condensations embedded in the hot intergalactic gas in clusters of galaxies is investigated by means of steady, one-dimensional, hydrodynamic models. It is assumed that heat conduction is effective only on scales much smaller than the total region of the cooling flow. Models are calculated for an arbitrary scaling factor, accounting for the reduction in heat conduction efficiency compared to the classical Spitzer case. The results imply a lower limit to the size spectrum of the condensations. The enhancement of cooling in the ambient medium due to heat conduction losses is calculated for a range of clump parameters. The luminosity of several observable emission lines, the extreme ultraviolet (EUV) and soft X-ray emission spectrum, and the column density of some important ions are determined for the model boundary layers and compared with observations.

  14. Multiphase groundwater flow near cooling plutons

    USGS Publications Warehouse

    Hayba, D.O.; Ingebritsen, S.E.

    1997-01-01

    We investigate groundwater flow near cooling plutons with a computer program that can model multiphase flow, temperatures up to 1200??C, thermal pressurization, and temperature-dependent rock properties. A series of experiments examines the effects of host-rock permeability, size and depth of pluton emplacement, single versus multiple intrusions, the influence of a caprock, and the impact of topographically driven groundwater flow. We also reproduce and evaluate some of the pioneering numerical experiments on flow around plutons. Host-rock permeability is the principal factor influencing fluid circulation and heat transfer in hydrothermal systems. The hottest and most steam-rich systems develop where permeability is of the order of 10-15 m2. Temperatures and life spans of systems decrease with increasing permeability. Conduction-dominated systems, in which permeabilities are ???10-16m2, persist longer but exhibit relatively modest increases in near-surface temperatures relative to ambient conditions. Pluton size, emplacement depth, and initial thermal conditions have less influence on hydrothermal circulation patterns but affect the extent of boiling and duration of hydrothermal systems. Topographically driven groundwater flow can significantly alter hydrothermal circulation; however, a low-permeability caprock effectively decouples the topographically and density-driven systems and stabilizes the mixing interface between them thereby defining a likely ore-forming environment.

  15. The galaxy cluster RXC J1504-0248: a remarkable cool core near us

    NASA Astrophysics Data System (ADS)

    Cecília Soja, Ana; Sodre, Laerte; Serra Cypriano, Eduardo; Lima Neto, Gastao B.

    2015-08-01

    One of the most intriguing questions for our understanding of galaxy clusters evolution is the identification of the mechanisms that regulate the temperature of the intergalactic medium in the cluster central region. Conventional cooling models predict a cooling flow of the intracluster gas much higher than observed, suggesting that some mechanisms heats the gas and inhibits the predicted cooling rates. Among the mechanisms proposed for heating the gas, stand out star formation and nuclear activity. The galaxy cluster RXC J1504-0248, located at z = 0.215, is a remarkable example of cool core cluster relatively close to us; its BCG has an extraordinary external filamentary gas structure, comparable to that observed in NGC 1275, in the Perseus cluster. We have studied this object with optical images and spectra obtained with the Gemini South Telescope. We have estimated the cluster mass through weak and strong gravitational lensing techniques, using a NFW-type profile and the analysis of two gravitational arc, respectively. We have obtained 1.5(5) x 10¹⁵ h-1M⊙ within a 3 h-1 Mpc radius (from WL) and 3.74 (3) x 10¹³ M⊙ inside a 62.9 h-1 kpc radius (from SL). These results are consistent with previous estimations obtaneid by Borhringer et al., of 1.7(3) x 10¹⁵ h-1 M⊙ within 3 h-1 Mpc, based in X-ray analysis; the agreement between the WL and X-ray masses estimates is an indication that the cluster is approximately in dynamical equilibrium. Thus, the processes affecting its central region must rely primarily on internal processes to the cluster and, in particular, associated with its dominant galaxy. The analysis of the BCG emission lines with a BPT diagram indicates that, while the nuclear emission is consitent with a LINER, the emission lines from the filamentary region around the BCG comes from star formation.

  16. Radiative cooling of Al{sub 4}{sup -} clusters

    SciTech Connect

    Toker, Y.; Aviv, O.; Eritt, M.; Rappaport, M. L.; Heber, O.; Zajfman, D.; Schwalm, D.

    2007-11-15

    The radiative cooling of isolated, negatively charged four-atom aluminum clusters has been measured using an electrostatic ion beam trap. Stored Al{sub 4}{sup -} ions were irradiated by a short laser pulse at different times after their production in a hot ion source, and delayed electron emission was observed up to hundreds of microseconds after the laser pulse. The decay curves could be well reproduced using an Arrhenius decay law and allowed us to deduce the cluster temperatures at the time of the laser pulse. Using this sensitive molecular thermometer, the cluster temperature could be determined as a function of storage time. The radiation intensity is found to decrease from 40 eV/s at T=1400 K to 1 eV/s at 500 K with a temperature dependence as given by T{sup b} with b=3.5{+-}0.2--i.e., similar to what would be expected from a blackbody. This cooling behavior requires the presence of either electronic transitions or very collective infrared-active vibrations at transition energies around {approx}200 meV.

  17. The Relation between Cool Cluster Cores and Herschel-detected Star Formation in Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Rawle, T. D.; Edge, A. C.; Egami, E.; Rex, M.; Smith, G. P.; Altieri, B.; Fiedler, A.; Haines, C. P.; Pereira, M. J.; Pérez-González, P. G.; Portouw, J.; Valtchanov, I.; Walth, G.; van der Werf, P. P.; Zemcov, M.

    2012-03-01

    We present far-infrared (FIR) analysis of 68 brightest cluster galaxies (BCGs) at 0.08 < z < 1.0. Deriving total infrared luminosities directly from Spitzer and Herschel photometry spanning the peak of the dust component (24-500 μm), we calculate the obscured star formation rate (SFR). 22+6.2 -5.3% of the BCGs are detected in the far-infrared, with SFR = 1-150 M ⊙ yr-1. The infrared luminosity is highly correlated with cluster X-ray gas cooling times for cool-core clusters (gas cooling time <1 Gyr), strongly suggesting that the star formation in these BCGs is influenced by the cluster-scale cooling process. The occurrence of the molecular gas tracing Hα emission is also correlated with obscured star formation. For all but the most luminous BCGs (L TIR > 2 × 1011 L ⊙), only a small (lsim0.4 mag) reddening correction is required for SFR(Hα) to agree with SFRFIR. The relatively low Hα extinction (dust obscuration), compared to values reported for the general star-forming population, lends further weight to an alternate (external) origin for the cold gas. Finally, we use a stacking analysis of non-cool-core clusters to show that the majority of the fuel for star formation in the FIR-bright BCGs is unlikely to originate from normal stellar mass loss. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  18. Chandra Observation of Abell 1142: A Cool-core Cluster Lacking a Central Brightest Cluster Galaxy?

    NASA Astrophysics Data System (ADS)

    Su, Yuanyuan; Buote, David A.; Gastaldello, Fabio; van Weeren, Reinout

    2016-04-01

    Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s-1. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous LX-TX scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.

  19. Chandra Observation of Abell 1142: A Cool-core Cluster Lacking a Central Brightest Cluster Galaxy?

    NASA Astrophysics Data System (ADS)

    Su, Yuanyuan; Buote, David A.; Gastaldello, Fabio; van Weeren, Reinout

    2016-04-01

    Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s‑1. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous LX–TX scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.

  20. Cluster analysis of multiple planetary flow regimes

    NASA Technical Reports Server (NTRS)

    Mo, Kingtse; Ghil, Michael

    1987-01-01

    A modified cluster analysis method was developed to identify spatial patterns of planetary flow regimes, and to study transitions between them. This method was applied first to a simple deterministic model and second to Northern Hemisphere (NH) 500 mb data. The dynamical model is governed by the fully-nonlinear, equivalent-barotropic vorticity equation on the sphere. Clusters of point in the model's phase space are associated with either a few persistent or with many transient events. Two stationary clusters have patterns similar to unstable stationary model solutions, zonal, or blocked. Transient clusters of wave trains serve as way stations between the stationary ones. For the NH data, cluster analysis was performed in the subspace of the first seven empirical orthogonal functions (EOFs). Stationary clusters are found in the low-frequency band of more than 10 days, and transient clusters in the bandpass frequency window between 2.5 and 6 days. In the low-frequency band three pairs of clusters determine, respectively, EOFs 1, 2, and 3. They exhibit well-known regional features, such as blocking, the Pacific/North American (PNA) pattern and wave trains. Both model and low-pass data show strong bimodality. Clusters in the bandpass window show wave-train patterns in the two jet exit regions. They are related, as in the model, to transitions between stationary clusters.

  1. Star Formation Efficiency in the Cool Cores of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    McDonald, Michael; Veilleux, Sylvain; Rupke, David S. N.; Mushotzky, Richard; Reynolds, Christopher

    2011-06-01

    We have assembled a sample of high spatial resolution far-UV (Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel) and Hα (Maryland-Magellan Tunable Filter) imaging for 15 cool core galaxy clusters. These data provide a detailed view of the thin, extended filaments in the cores of these clusters. Based on the ratio of the far-UV to Hα luminosity, the UV spectral energy distribution, and the far-UV and Hα morphology, we conclude that the warm, ionized gas in the cluster cores is photoionized by massive, young stars in all but a few (A1991, A2052, A2580) systems. We show that the extended filaments, when considered separately, appear to be star forming in the majority of cases, while the nuclei tend to have slightly lower far-UV luminosity for a given Hα luminosity, suggesting a harder ionization source or higher extinction. We observe a slight offset in the UV/Hα ratio from the expected value for continuous star formation which can be modeled by assuming intrinsic extinction by modest amounts of dust (E(B - V) ~ 0.2) or a top-heavy initial mass function in the extended filaments. The measured star formation rates vary from ~0.05 M sun yr-1 in the nuclei of non-cooling systems, consistent with passive, red ellipticals, to ~5 M sun yr-1 in systems with complex, extended, optical filaments. Comparing the estimates of the star formation rate based on UV, Hα, and infrared luminosities to the spectroscopically determined X-ray cooling rate suggests a star formation efficiency of 14+18 - 8%. This value represents the time-averaged fraction, by mass, of gas cooling out of the intracluster medium, which turns into stars and agrees well with the global fraction of baryons in stars required by simulations to reproduce the stellar mass function for galaxies. This result provides a new constraint on the efficiency of star formation in accreting systems.

  2. The clustering of warm and cool IRAS galaxies

    NASA Astrophysics Data System (ADS)

    Mann, R. G.; Saunders, W.; Taylor, A. N.

    1996-03-01

    We use a series of statistical techniques to compare the clustering of samples of IRAS galaxies selected on the basis of their far-infrared emission temperature, to see whether a temperature-dependent effect, such as might be produced by interaction-induced star formation, could be responsible for the increase in clustering strength with redshift in the QDOT redshift survey that has been reported by several authors. The temperature-luminosity relation for IRAS galaxies means that warm and cool samples drawn from a flux-limited sample like QDOT will sample quite different volumes of space. To overcome this problem, and to distinguish truly temperature-dependent results from those depending directly on the volume of space sampled, we consider a pair of samples of warmer and cooler galaxies with matched redshift distributions, as well as pairs of samples selected using a simple temperature cut. We find that the redshift-space autocorrelation function of warm QDOT galaxies is significantly stronger than that of cool galaxies on large scales, but that this difference disappears when we come to consider the warmer and cooler samples with matched redshift distributions. A counts- in-cells analysis reveals no significant difference between the clustering of the warm and cool QDOT samples, while the use of a new, symmetric estimator reveals that the cross-correlations of warm and cool IRAS galaxies with Abell clusters do not differ significantly. A higher signal-to-noise ratio test is provided by computing the projected cross- correlations of the matched samples with the parent two-dimensional catalogue from which QDOT is drawn, and this does yield a marginal detection of greater large-scale power for warmer galaxies. A direct comparison of the distributions of the warmer and cooler samples, using a new technique which tests the null hypothesis that they are drawn from the same population, reveals that the two classes of galaxy do cluster differently on small scales in

  3. Radially-Inflowing Molecular Gas Deposited by a X-ray Cooling Flow

    NASA Astrophysics Data System (ADS)

    Lim, Jeremy; Ao, Y.; Dinh, V.

    2006-12-01

    Galaxy clusters are immersed in hot X-ray-emitting gas that constitutes a large fraction of their baryonic mass. Radiative cooling of this gas, if not adequately balanced by heat input, should result in an inflow of cooler gas to the central dominant giant elliptical (cD) galaxy. Although a straightforward prediction made nearly twenty years ago, the occurrence of such X-ray cooling flows is widely questioned as gas at lower temperatures is often not found at the predicted quantities. The exceptions are cD galaxies harbouring large quantities of cool molecular gas, but the origin of this gas is uncertain as ram-pressure stripping or cannibalism of gas-rich cluster galaxies provide viable alternatives to cooling flows. Here, we present the most direct evidence yet for the deposition of molecular gas in a cD galaxy, Perseus A, from a X-ray cooling flow. The molecular gas detected in this galaxy is concentrated in three radial filaments with projected lengths of at least 2 kpc, one extending inwards close to the active nucleus and the other two extending outwards to at least 8 kpc on the east and west. All three filaments coincide with bright Hα features, and lie along a central X-ray ridge where any cooling flow is strongest. The two outer filaments exhibit increasingly blueshifted velocities at smaller radii that we show trace radial inflow along the gravitational potential of the galaxy. The innermost filament appears to be settling into the potential well, and may fuel the central supermassive black hole whose radio jets heat gas over a large solid angle in the north-south direction. Our results demonstrate that X-ray cooling flows can indeed deposit large quantities of cool gas, but only intermittently along directions where the X-ray gas is not being reheated.

  4. Effect of weak swirling flow on film cooling performance

    NASA Astrophysics Data System (ADS)

    Gau, C.; Hwang, W. B.

    1990-10-01

    Experiments have been performed in a large circular pipe to study and obtain the film cooling effectivenesses with the presence of weak swirling flow in the mainstream. The swirling flow is generated by a flat vane swirler situated upstream. Cooling film is injected from an annular slot formed by the pipe wall and the circular cover plate. The radial temperature distribution measurements at several axial locations were used to infer the rate of mixing of film jet with swirling flow. The swirl number, which increases with turbulence intensity and swirl velocity in the mainstream, can significantly increase the mixing rate of film jet with swirl flow and decrease the film cooling effectiveness. During the course of the experiments, the blowing ratio ranged from 0.5 to 1.75 and the swirl number ranged from 0 to 0.6. Correlation equations for the film cooling effectiveness, which account for the effect of swirling flow, are obtained.

  5. TURBINE COOLING FLOW AND THE RESULTING DECREASE IN TURBINE EFFICIENCY

    NASA Technical Reports Server (NTRS)

    Gauntner, J. W.

    1994-01-01

    This algorithm has been developed for calculating both the quantity of compressor bleed flow required to cool a turbine and the resulting decrease in efficiency due to cooling air injected into the gas stream. Because of the trend toward higher turbine inlet temperatures, it is important to accurately predict the required cooling flow. This program is intended for use with axial flow, air-breathing jet propulsion engines with a variety of airfoil cooling configurations. The algorithm results have compared extremely well with figures given by major engine manufacturers for given bulk metal temperatures and cooling configurations. The program calculates the required cooling flow and corresponding decrease in stage efficiency for each row of airfoils throughout the turbine. These values are combined with the thermodynamic efficiency of the uncooled turbine to predict the total bleed airflow required and the altered turbine efficiency. There are ten airfoil cooling configurations and the algorithm allows a different option for each row of cooled airfoils. Materials technology is incorporated and requires the date of the first year of service for the turbine stator vane and rotor blade. The user must specify pressure, temperatures, and gas flows into the turbine. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 3080 series computer with a central memory requirement of approximately 61K of 8 bit bytes. This program was developed in 1980.

  6. THE GROWTH OF COOL CORES AND EVOLUTION OF COOLING PROPERTIES IN A SAMPLE OF 83 GALAXY CLUSTERS AT 0.3 < z < 1.2 SELECTED FROM THE SPT-SZ SURVEY

    SciTech Connect

    McDonald, M.; Bautz, M. W.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Vikhlinin, A.; Stalder, B.; Ashby, M. L. N.; Bayliss, M.; De Haan, T.; Lin, H. W.; Aird, K. A.; Bocquet, S.; Desai, S.; Brodwin, M.; Cho, H. M.; Clocchiatti, A.; and others

    2013-09-01

    We present first results on the cooling properties derived from Chandra X-ray observations of 83 high-redshift (0.3 < z < 1.2) massive galaxy clusters selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. We measure each cluster's central cooling time, central entropy, and mass deposition rate, and compare these properties to those for local cluster samples. We find no significant evolution from z {approx} 0 to z {approx} 1 in the distribution of these properties, suggesting that cooling in cluster cores is stable over long periods of time. We also find that the average cool core entropy profile in the inner {approx}100 kpc has not changed dramatically since z {approx} 1, implying that feedback must be providing nearly constant energy injection to maintain the observed ''entropy floor'' at {approx}10 keV cm{sup 2}. While the cooling properties appear roughly constant over long periods of time, we observe strong evolution in the gas density profile, with the normalized central density ({rho}{sub g,0}/{rho}{sub crit}) increasing by an order of magnitude from z {approx} 1 to z {approx} 0. When using metrics defined by the inner surface brightness profile of clusters, we find an apparent lack of classical, cuspy, cool-core clusters at z > 0.75, consistent with earlier reports for clusters at z > 0.5 using similar definitions. Our measurements indicate that cool cores have been steadily growing over the 8 Gyr spanned by our sample, consistent with a constant, {approx}150 M{sub Sun} yr{sup -1} cooling flow that is unable to cool below entropies of 10 keV cm{sup 2} and, instead, accumulates in the cluster center. We estimate that cool cores began to assemble in these massive systems at z{sub cool}=1.0{sup +1.0}{sub -0.2}, which represents the first constraints on the onset of cooling in galaxy cluster cores. At high redshift (z {approx}> 0.75), galaxy clusters may be classified as ''cooling flows'' (low central entropy, cooling time) but not

  7. Groundwater flow as a cooling agent of the continental lithosphere

    NASA Astrophysics Data System (ADS)

    Kooi, Henk

    2016-03-01

    Groundwater that flows through the outer shell of the Earth as part of the hydrologic cycle influences the distribution of heat and, thereby, the temperature field in the Earth’s crust. Downward groundwater flow in recharge areas lowers crustal temperatures, whereas upward flow in discharge areas tends to raise temperatures relative to a purely conductive geothermal regime. Here I present numerical simulations of generalized topography-driven groundwater flow. The simulations suggest that groundwater-driven convective cooling exceeds groundwater-driven warming of the Earth’s crust, and hence that groundwater flow systems cause net temperature reductions of groundwater basins. Moreover, the simulations demonstrate that this cooling extends into the underlying crust and lithosphere. I find that horizontal components of groundwater flow play a central role in this net subsurface cooling by conveying relatively cold water to zones of upward groundwater flow. The model calculations suggest that the crust and lithosphere beneath groundwater basins can cool by several tens of degrees Celsius where groundwater flows over large distances in basins that consist of crustal rock. In contrast, groundwater-induced cooling is small in unconsolidated sedimentary settings, such as deltas.

  8. Large eddy simulations of turbulent flows on graphics processing units: Application to film-cooling flows

    NASA Astrophysics Data System (ADS)

    Shinn, Aaron F.

    Computational Fluid Dynamics (CFD) simulations can be very computationally expensive, especially for Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS) of turbulent ows. In LES the large, energy containing eddies are resolved by the computational mesh, but the smaller (sub-grid) scales are modeled. In DNS, all scales of turbulence are resolved, including the smallest dissipative (Kolmogorov) scales. Clusters of CPUs have been the standard approach for such simulations, but an emerging approach is the use of Graphics Processing Units (GPUs), which deliver impressive computing performance compared to CPUs. Recently there has been great interest in the scientific computing community to use GPUs for general-purpose computation (such as the numerical solution of PDEs) rather than graphics rendering. To explore the use of GPUs for CFD simulations, an incompressible Navier-Stokes solver was developed for a GPU. This solver is capable of simulating unsteady laminar flows or performing a LES or DNS of turbulent ows. The Navier-Stokes equations are solved via a fractional-step method and are spatially discretized using the finite volume method on a Cartesian mesh. An immersed boundary method based on a ghost cell treatment was developed to handle flow past complex geometries. The implementation of these numerical methods had to suit the architecture of the GPU, which is designed for massive multithreading. The details of this implementation will be described, along with strategies for performance optimization. Validation of the GPU-based solver was performed for fundamental bench-mark problems, and a performance assessment indicated that the solver was over an order-of-magnitude faster compared to a CPU. The GPU-based Navier-Stokes solver was used to study film-cooling flows via Large Eddy Simulation. In modern gas turbine engines, the film-cooling method is used to protect turbine blades from hot combustion gases. Therefore, understanding the physics of

  9. Hot Gaseous Atmospheres in Galaxy Groups and Clusters Are Both Heated and Cooled by X-Ray Cavities

    NASA Astrophysics Data System (ADS)

    Brighenti, Fabrizio; Mathews, William G.; Temi, Pasquale

    2015-04-01

    Expanding X-ray cavities observed in hot gas atmospheres of many galaxy groups and clusters generate shock waves and turbulence that are primary heating mechanisms required to avoid uninhibited radiatively cooling flows which are not observed. However, we show here that the evolution of buoyant cavities also stimulates radiative cooling of observable masses of low-temperature gas. During their early evolution, radiative cooling occurs in the wakes of buoyant cavities in two locations: in thin radial filaments parallel to the buoyant velocity and more broadly in gas compressed beneath rising cavities. Radiation from these sustained compressions removes entropy from the hot gas. Gas experiencing the largest entropy loss cools first, followed by gas with progressively less entropy loss. Most cooling occurs at late times, ˜ 108-109 yr, long after the X-ray cavities have disrupted and are impossible to detect. During these late times, slightly denser low entropy gas sinks slowly toward the centers of the hot atmospheres where it cools intermittently, forming clouds near the cluster center. Single cavities of energy 1057-1058 ergs in the atmosphere of the NGC 5044 group create 108-109 M⊙ of cooled gas, exceeding the mass of extended molecular gas currently observed in that group. The cooled gas clouds we compute share many attributes with molecular clouds recently observed in NGC 5044 with ALMA: self-gravitationally unbound, dust-free, quasi-randomly distributed within a few kiloparsecs around the group center.

  10. Quantitative prediction of clustering instabilities in gas-solid homogeneous cooling systems

    NASA Astrophysics Data System (ADS)

    Hrenya, Christine; Mitrano, Peter; Li, Xiaoqi; Yin, Xiaolong

    2014-11-01

    Dynamic particle clusters are widely documented in gas-solid flow systems, including gasification units for coal or biomass, gravity-driven flow over an array of tubes, pneumatic transport lines, etc. Continuum descriptions based on kinetic theory have been known for over a decade to qualitatively predict the presence of such clustering instabilities. The quantitative ability of such continuum descriptions is relatively unexplored, however, and remains unclear given the low-Knudsen assumption upon which the descriptions are based. In particular, the concentration gradient is relatively large across the boundary between the cluster and the surrounding dilute region, which is counter to the small-gradient assumption inherent in the low-Knudsen-number expansion. In this work, we use direct numerical simulations (DNS) of a gas-solid homogeneous cooling system to determine the critical system size needed for the clustering instability to develop. We then compare the results to the same quantity predicted by a continuum description based on kinetic theory. The agreement is quite good over a wide range of parameters. This finding is reminiscent of molecular fluids, namely the ability of the Navier-Stokes equations to predict well outside the expected range of Knudsen numbers.

  11. Compound cooling flow turbulator for turbine component

    SciTech Connect

    Lee, Ching-Pang; Jiang, Nan; Marra, John J; Rudolph, Ronald J

    2014-11-25

    Multi-scale turbulation features, including first turbulators (46, 48) on a cooling surface (44), and smaller turbulators (52, 54, 58, 62) on the first turbulators. The first turbulators may be formed between larger turbulators (50). The first turbulators may be alternating ridges (46) and valleys (48). The smaller turbulators may be concave surface features such as dimples (62) and grooves (54), and/or convex surface features such as bumps (58) and smaller ridges (52). An embodiment with convex turbulators (52, 58) in the valleys (48) and concave turbulators (54, 62) on the ridges (46) increases the cooling surface area, reduces boundary layer separation, avoids coolant shadowing and stagnation, and reduces component mass.

  12. Influence of cooling on lava-flow dynamics

    NASA Astrophysics Data System (ADS)

    Stasiuk, Mark V.; Jaupart, Claude; Stephen, R.; Sparks, J.

    1993-04-01

    Experiments have been carried out to determine the effects of cooling on the flow of fluids with strongly temperature dependent viscosity. Radial viscous-gravity currents of warm glucose syrup were erupted at constant rate into a flat tank filled with a cold aqueous solution. Cold, viscous fluid accumulates at the leading edge, altering the flow shape and thickness and slowing the spreading. The flows attain constant internal temperature distributions and bulk viscosities. The value of the bulk viscosity depends on the Péclet number, which reflects the advective and diffusive heat transport properties of the flow, the flow skin viscosity, which reflects cooling, and the eruption viscosity. Our results explain why most lava flows have bulk viscosities much higher than the lava eruption viscosity. The results can be applied to understanding dynamic lava features such as flow-front thickening, front avalanches, and welded basal breccias.

  13. Flow Cooling of Superconducting Magnets for Spacecraft Applications

    NASA Astrophysics Data System (ADS)

    Dietz, A. J.; Audette, W. E.; Barton, M. D.; Hilderbrand, J. K.; Marshall, W. S.; Rey, C. M.; Winter, D. S.; Petro, A. J.

    2008-03-01

    The development and testing of a flow cooling system for high-temperature superconducting (HTS) magnets is described. The system includes a turbo-Brayton cryocooler, a magnet thermal interface, and a magnet thermal isolation and support system. The target application is the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). Turbo-Brayton coolers are well suited to such spacecraft applications, as they are compact, modular, lightweight, and efficient, with long maintenance-free lifetimes. Furthermore, the technology scales well to high-cooling capacities. The feasibility of using turbo-Brayton coolers in this application was proven in a design exercise in which existing cooler designs were scaled to provide cooling for the magnet sets required by 200 kW and 1 MW VASIMR engines. The performance of the concepts for the thermal interface and the thermal isolation and support system were measured in separate laboratory tests with a demonstration system built about a representative HTS magnet. Cooling for these tests was provided by a flow cooling loop comprising a compressor, recuperator and GM cryocooler, with the flow pressure, temperature, and mass flow rate selected to effectively simulate the turbo-Brayton operating condition. During system testing, the magnet was cooled below its design operating temperature of 35 K, and good thermal uniformity (<0.4 K) and low thermal loads (<0.5 W) were demonstrated.

  14. Cool Core Bias in Sunyaev-Zel’dovich Galaxy Cluster Surveys

    SciTech Connect

    Lin, Henry W.; McDonald, Michael; Benson, Bradford; Miller, Eric

    2015-03-18

    Sunyaev-Zeldovich (SZ) surveys find massive clusters of galaxies by measuring the inverse Compton scattering of cosmic microwave background off of intra-cluster gas. The cluster selection function from such surveys is expected to be nearly independent of redshift and cluster astrophysics. In this work, we estimate the effect on the observed SZ signal of centrally-peaked gas density profiles (cool cores) and radio emission from the brightest cluster galaxy (BCG) by creating mock observations of a sample of clusters that span the observed range of classical cooling rates and radio luminosities. For each cluster, we make simulated SZ observations by the South Pole Telescope and characterize the cluster selection function, but note that our results are broadly applicable to other SZ surveys. We find that the inclusion of a cool core can cause a change in the measured SPT significance of a cluster between 0.01%–10% at z > 0.3, increasing with cuspiness of the cool core and angular size on the sky of the cluster (i.e., decreasing redshift, increasing mass). We provide quantitative estimates of the bias in the SZ signal as a function of a gas density cuspiness parameter, redshift, mass, and the 1.4 GHz radio luminosity of the central AGN. Based on this work, we estimate that, for the Phoenix cluster (one of the strongest cool cores known), the presence of a cool core is biasing the SZ significance high by ~6%. The ubiquity of radio galaxies at the centers of cool core clusters will offset the cool core bias to varying degrees

  15. Cool Core Bias in Sunyaev-Zel’dovich Galaxy Cluster Surveys

    DOE PAGES

    Lin, Henry W.; McDonald, Michael; Benson, Bradford; Miller, Eric

    2015-03-18

    Sunyaev-Zeldovich (SZ) surveys find massive clusters of galaxies by measuring the inverse Compton scattering of cosmic microwave background off of intra-cluster gas. The cluster selection function from such surveys is expected to be nearly independent of redshift and cluster astrophysics. In this work, we estimate the effect on the observed SZ signal of centrally-peaked gas density profiles (cool cores) and radio emission from the brightest cluster galaxy (BCG) by creating mock observations of a sample of clusters that span the observed range of classical cooling rates and radio luminosities. For each cluster, we make simulated SZ observations by the Southmore » Pole Telescope and characterize the cluster selection function, but note that our results are broadly applicable to other SZ surveys. We find that the inclusion of a cool core can cause a change in the measured SPT significance of a cluster between 0.01%–10% at z > 0.3, increasing with cuspiness of the cool core and angular size on the sky of the cluster (i.e., decreasing redshift, increasing mass). We provide quantitative estimates of the bias in the SZ signal as a function of a gas density cuspiness parameter, redshift, mass, and the 1.4 GHz radio luminosity of the central AGN. Based on this work, we estimate that, for the Phoenix cluster (one of the strongest cool cores known), the presence of a cool core is biasing the SZ significance high by ~6%. The ubiquity of radio galaxies at the centers of cool core clusters will offset the cool core bias to varying degrees« less

  16. A CHANDRA X-RAY ANALYSIS OF ABELL 1664: COOLING, FEEDBACK, AND STAR FORMATION IN THE CENTRAL CLUSTER GALAXY

    SciTech Connect

    Kirkpatrick, C. C.; McNamara, B. R.; Kazemzadeh, F.; Cavagnolo, K. W.; Rafferty, D. A.; BIrzan, L.; Nulsen, P. E. J.; Wise, M. W.; Gitti, M.

    2009-05-20

    The brightest cluster galaxy (BCG) in the Abell 1664 cluster is unusually blue and is forming stars at a rate of {approx} 23 M {sub sun} yr{sup -1}. The BCG is located within 5 kpc of the X-ray peak, where the cooling time of 3.5 x 10{sup 8} yr and entropy of 10.4 keV cm{sup 2} are consistent with other star-forming BCGs in cooling flow clusters. The center of A1664 has an elongated, 'barlike' X-ray structure whose mass is comparable to the mass of molecular hydrogen, {approx}10{sup 10} M {sub sun} in the BCG. We show that this gas is unlikely to have been stripped from interloping galaxies. The cooling rate in this region is roughly consistent with the star formation rate, suggesting that the hot gas is condensing onto the BCG. We use the scaling relations of BIrzan et al. to show that the active galactic nucleus (AGN) is underpowered compared to the central X-ray cooling luminosity by roughly a factor of three. We suggest that A1664 is experiencing rapid cooling and star formation during a low state of an AGN feedback cycle that regulates the rates of cooling and star formation. Modeling the emission as a single-temperature plasma, we find that the metallicity peaks 100 kpc from the X-ray center, resulting in a central metallicity dip. However, a multi-temperature cooling flow model improves the fit to the X-ray emission and is able to recover the expected, centrally peaked metallicity profile.

  17. An XMM-Newton Study of the Core of the Antlia Cluster: Heating and Chemical Enrichment in a Galaxy Cluster without a Cool Core

    NASA Astrophysics Data System (ADS)

    Hawley, William; Machacek, M.; Kraft, R. P.

    2011-09-01

    A fundamental question for models of structure formation is how energy and heavy elements are distributed throughout the intra-cluster medium (ICM) as the cluster evolves hierarchically by sub-cluster mergers along filaments in the cosmic web. The dominant dynamical processes -- hydrodynamic and tidal stripping, supernovae and stellar winds, bulk gas motions induced by mergers, and matter entrainment uplifted by AGN driven jets and buoyant bubbles -- create distinct X-ray signatures in surface brightness images and temperature and abundance maps of the cluster gas. The relative efficiencies of these processes during the early stages of cluster evolution are not well understood. We use a 53 ks XMM-Newton exposure of the inner 12 arcminutes of the Antlia cluster, the nearest example of a galaxy cluster in an intermediate merger stage without a cool core, to study energy and metal transport throughout the cluster gas. We construct density, temperature, pressure, entropy and abundance maps to identify gas motions and heat flows, relate these motions to the metal abundance ratios and gradients, and test simple models for chemical enrichment and heating of the Antlia cluster ICM.

  18. Compliant Metal Enhanced Convection Cooled Reverse-Flow Annular Combustor

    NASA Technical Reports Server (NTRS)

    Paskin, Marc D.; Acosta, Waldo A.

    1994-01-01

    A joint Army/NASA program was conducted to design, fabricate, and test an advanced, reverse-flow, small gas turbine combustor using a compliant metal enhanced (CME) convection wall cooling concept. The objectives of this effort were to develop a design method (basic design data base and analysis) for the CME cooling technique and tben demonstrate its application to an advanced cycle, small, reverse-flow combustor with 3000 F (1922 K) burner outlet temperature (BOT). The CME concept offers significant improvements in wall cooling effectiveness resulting in a large reduction in cooling air requirements. Therefore, more air is available for control of burner outlet temperature pattern in addition to the benefit of improved efficiency, reduced emissions, and smoke levels. Rig test results demonstrated the benefits and viability of the CME concept meeting or exceeding the aerothermal performance and liner wall temperature characteristics of similar lower temperature-rise combustors, achieving 0.15 pattern factor at 3000 F (1922 K) BOT, while utilizing approximately 80 percent less cooling air than conventional, film-cooled combustion systems.

  19. Inductively coupled plasma torch with laminar flow cooling

    DOEpatents

    Rayson, Gary D.; Shen, Yang

    1991-04-30

    An improved inductively coupled gas plasma torch. The torch includes inner and outer quartz sleeves and tubular insert snugly fitted between the sleeves. The insert includes outwardly opening longitudinal channels. Gas flowing through the channels of the insert emerges in a laminar flow along the inside surface of the outer sleeve, in the zone of plasma heating. The laminar flow cools the outer sleeve and enables the torch to operate at lower electrical power and gas consumption levels additionally, the laminar flow reduces noise levels in spectroscopic measurements of the gaseous plasma.

  20. Lava Flows on Io: Modelling Cooling After Solidification

    NASA Technical Reports Server (NTRS)

    Davies, A. G.; Matson, D. L.; Veeder, G. J.; Johnson, T. V.; Blaney, D. L.

    2003-01-01

    We have modeled the cooling of lava bodies on Io after solidification of the lava, a process that has been little explored since Carr (1986). With recent estimates of lava flow thicknesses on Io ranging from 1 m to 10 m, the modeling of thermal emission from active volcanism must take into account the cooling behaviour after the solidification of the lava, which we model using a finite-element model. Once a lava body is fully solidified, the surface temperature decreases faster, as heat loss is no longer buffered by release of latent heat. This is significant as observed surface temperature is often the only clue available to determine lava surface age. We also find that cooling from the base of the lava is an important process that accelerates the solidification of a flow and therefore subsequent cooling. It is necessary to constrain the cooling process in order to better understand temperature-area relationships on Io's surface and to carry out stochastic modelling of lava flow emplacement.

  1. Highly-luminous Cool Core Clusters of Galaxies: Mechanically-driven or Radiatively-driven AGN?

    NASA Astrophysics Data System (ADS)

    Hlavacek-Larrondo, Julie; Fabian, Andy

    2011-12-01

    Cool core clusters of galaxies require strong feedback from their central AGN to offset cooling. We present a study of strong cool core, highly-luminous (most with Lx >= 1045 erg s-1), clusters of galaxies in which the mean central AGN jet power must be very high yet no central point X-ray source is detected. Using the unique spatial resolution of Chandra, a sample of 13 clusters is analysed, including A1835, A2204, and one of the most massive cool core clusters, RXCJ1504.1-0248. All of the central galaxies host a radio source, indicating an active nucleus, and no obvious X-ray point source. For all clusters in the sample, the nucleus has an X-ray bolometric luminosity below 2 per cent of that of the entire cluster. We investigate how these clusters can have such strong X-ray luminosities, short radiative cooling-times of the inner intracluster gas requiring strong energy feedback to counterbalance that cooling, and yet have such radiatively-inefficient cores with, on average, Lkin/Lnuc exceeding 200. Explanations of this puzzle carry significant implications for the origin and operation of jets, as well as on establishing the importance of kinetic feedback for the evolution of galaxies and their surrounding medium.

  2. Direct Numerical Simulation of A Shaped Hole Film Cooling Flow

    NASA Astrophysics Data System (ADS)

    Oliver, Todd; Moser, Robert

    2015-11-01

    The combustor exit temperatures in modern gas turbine engines are generally higher than the melting temperature of the turbine blade material. Film cooling, where cool air is fed through holes in the turbine blades, is one strategy which is used extensively in such engines to reduce heat transfer to the blades and thus reduce their temperature. While these flows have been investigated both numerically and experimentally, many features are not yet well understood. For example, the geometry of the hole is known to have a large impact on downstream cooling performance. However, the details of the flow in the hole, particularly for geometries similar to those used in practice, are generally know well-understood, both because it is difficult to experimentally observe the flow inside the hole and because much of the numerical literature has focused on round hole simulations. In this work, we show preliminary direct numerical simulation results for a film cooling flow passing through a shaped hole into a the boundary layer developing on a flat plate. The case has density ratio 1.6, blowing ratio 2.0, and the Reynolds number (based on momentum thickness) of incoming boundary layer is approximately 600. We compare the new simulations against both previous experiments and LES.

  3. X-ray Observations of the Outskirts of the Nearest Non-Cool Core Cluster: the Antlia Cluster

    NASA Astrophysics Data System (ADS)

    Wong, Ka-Wah; Irwin, Jimmy; Wik, Daniel R.

    2015-01-01

    Suzaku X-ray observations have revealed hot gas properties of a number of clusters of galaxies out to their virial radii (R200), allowing us to explore regions that was not possible in the past. We present results of our Suzaku mosaic observations of the nearest non-cool core cluster, the Antlia Cluster (distance D = 39 Mpc), out to its degree-scale virial radius (R200 = 1 Mpc = 88 arcmin) in the East direction. Together with Chandra and XMM-Newton observations, we are able to reduce the systematic uncertainty caused by background point sources. We compare our results to: 1) a similarly nearby system but with a cool core, the Virgo Cluster (D = 16 Mpc), which has a similar virial temperature and radius as the Antlia Cluster, 2) the universal pressure profile, and 3) the entropy profile predicted with self-similar model. Our results suggest that the outskirts of this non-cool core are similar to those of the cool cores. More observations with (regular) non-cool cores are needed to test if thisis general.

  4. Clustering and velocity distributions in granular gases cooling by solid friction

    NASA Astrophysics Data System (ADS)

    Das, Prasenjit; Puri, Sanjay; Schwartz, Moshe

    2016-09-01

    We present large-scale molecular dynamics simulations to study the free evolution of granular gases. Initially, the density of particles is homogeneous and the velocity follows a Maxwell-Boltzmann (MB) distribution. The system cools down due to solid friction between the granular particles. The density remains homogeneous, and the velocity distribution remains MB at early times, while the kinetic energy of the system decays with time. However, fluctuations in the density and velocity fields grow, and the system evolves via formation of clusters in the density field and the local ordering of velocity field, consistent with the onset of plug flow. This is accompanied by a transition of the velocity distribution function from MB to non-MB behavior. We used equal-time correlation functions and structure factors of the density and velocity fields to study the morphology of clustering. From the correlation functions, we obtain the cluster size, L , as a function of time, t . We show that it exhibits power law growth with L (t ) ˜t1 /3 .

  5. Atomic scale simulations of vapor cooled carbon clusters

    NASA Astrophysics Data System (ADS)

    Bogana, M. P.; Colombo, L.

    2007-03-01

    By means of atomistic simulations we observed the formation of many topologically non-equivalent carbon clusters formed by the condensation of liquid droplets, including: (i) standard fullerenes and onion-like structures, (ii) clusters showing extremely complex surfaces with both positive and negative curvatures and (iii) complex endohedral structures. In this work we offer a thorough structural characterization of the above systems, as well as an attempt to correlate the resulting structure to the actual protocol of growth. The IR and Raman responses of some exotic linear carbon structures have been further investigated, finding good agreement with experimental evidence of carbinoid structures in cluster-assembled films. Towards the aim of fully understanding the process of cluster-to-cluster coalescence dynamics, we further simulated an aerosol of amorphous carbon clusters at controlled temperatures. Various annealing temperatures and times have been observed, identifying different pathways for cluster ripening, ranging from simple coalescence to extensive reconstruction.

  6. Regional spinal cord blood flow during local cooling

    SciTech Connect

    Sakamoto, T.; Monafo, W.W. )

    1990-06-01

    We used the tissue distribution of ({sup 14}C)butanol to quantitate regional blood flow in the spinal cord (RSCBF) of pentobarbital-anesthetized, normothermic rats in which segmental local cooling pentobarbital-anesthetized, normothermic rats in which segmental local cooling of the spinal cord (to 25-28{degrees}C) at vertebral levels C4-C6 (n = 6) or T13-L1 (n = 6) was induced. Thirty minutes later, blood flow measurements were made at seven levels of the spinal cord and in the sciatic nerve trunks and biceps femoris muscles. Sham-cooled rats served as controls (n = 12). In control rats, RSCBF varied between 41.5 +/- 2.4 and 65.1 +/- 3.2 ml.min-1.100 g-1. Local cooling of the C4-C6 cord segment reduced RSCBF by 32%, from 65.1 +/- 3.2 to 44.4 +/- 3.5 ml.min-1.100 g-1 (P less than 0.01). Tissue vascular resistance (R) in the cooled C4-C6 segment was elevated versus control. There were no other changes in RSCBF at the other cord levels or in the cauda equina. Similarly, local cooling of the T13-L1 segment resulted in a 40% fall in RSCBF in that segment, from 57.1 +/- 2.4 to 34.1 +/- 4.3 ml.min-1.100 g-1 (P less than 0.001). R in the cooled T13-L1 segment was elevated versus control. RSCBF was reduced by 30% in the adjacent proximal T12 segment (P less than 0.001) and by 21% in the adjacent distal L2-L3 segment (P less than 0.05). R was increased in both of these adjacent segments. RSCBF was not altered elsewhere in the cord.

  7. X-ray Observations of the Outskirts of the Nearest Non-Cool Core Cluster: the Antlia Cluster

    NASA Astrophysics Data System (ADS)

    Wong, Ka-Wah; Irwin, Jimmy; Wik, Daniel R.

    2014-08-01

    Recent Suzaku X-ray observations have revealed hot gas properties of a number of clusters of galaxies out to their virial radii, allowing us to explore regions that was not possible in the past. We will present results of our Suzaku mosaic observations of the nearest non-cool core cluster, the Antlia Cluster, out to its degree-scale virial radius in the East direction. Together with Chandra and XMM-Newton observations, systematic uncertainty caused by background point sources is greatly reduced. Physical properties such as surface brightness and temperature profiles will be presented and compared to theoretical models and other clusters. Implications of our results will be discussed.

  8. Mapping the nearest non-cool core cluster out to R200

    NASA Astrophysics Data System (ADS)

    Wong, Ka-Wah

    2012-09-01

    We propose to carry out mosaic observations (49 ks) of the Antlia cluster, the third closest galaxy cluster highly ignored by the X-ray community, out to R200. It is the nearest non-cool core cluster with a similarly low temperature as the cool core Virgo Cluster, allowing us to make a direct comparison to the cool core counterpart in our neighborhood. Physical properties such as density and temperature will be studied around the virial radius. These data can place important constraints on theoretical models of clusters and their environments. We will test models for clumping, electron-ion equipartition, and non-equilibrium ionization. The excellent Chandra spatial resolution combining with the low Suzaku background allows this measurement.

  9. Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

    NASA Technical Reports Server (NTRS)

    Baum, S. A.; O'Dea, C. P.

    1991-01-01

    Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

  10. The effects of magnetic fields in cold clouds in cooling flows

    NASA Astrophysics Data System (ADS)

    Friaça, A. C. S.; Jafelice, L. C.

    1999-01-01

    Large masses of absorbing material are inferred to exist in cooling flows in clusters of galaxies from the excess X-ray absorption in the spectra of some X-ray clusters. The absorbing material is probably in the form of cold clouds pressure-confined by the surrounding, hot, X-ray-emitting gas. The cold clouds could remain relatively static until they are destroyed by evaporation or ablation, or give rise to star formation. If the final fate of the clouds is stars, the initial mass function (IMF) of the stars formed over the whole cooling-flow region (r~ 100 kpc) should be biased to low masses, to avoid a very luminous, blue halo for the central galaxy of the cooling flow. However, there is evidence for bright star formation in the innermost (r<= 10 kpc) regions of some cooling flows, and, therefore, the biasing of the IMF towards low masses should not occur or should be less important at smaller radii. The consideration of magnetic fields may shed light on these two points. If magnetic fields are present, the magnetic critical mass should be considered, besides the Jeans mass, in establishing a natural mass-scale for star formation. When this new mass-scale is taken into account, we obtain the right variation of the biasing of the IMF with the radius in addition to inhibition of high-mass star formation at large radii. We also demonstrate that magnetic reconnection is a more efficient mechanism than ambipolar diffusion to remove magnetic fields in cold clouds.

  11. Eocene cooling linked to early flow across the Tasmanian Gateway

    PubMed Central

    Bijl, Peter K.; Bendle, James A. P.; Bohaty, Steven M.; Pross, Jörg; Schouten, Stefan; Tauxe, Lisa; Stickley, Catherine E.; McKay, Robert M.; Röhl, Ursula; Olney, Matthew; Sluijs, Appy; Escutia, Carlota; Brinkhuis, Henk; Klaus, Adam; Fehr, Annick; Williams, Trevor; Carr, Stephanie A.; Dunbar, Robert B.; Gonzàlez, Jhon J.; Hayden, Travis G.; Iwai, Masao; Jimenez-Espejo, Francisco J.; Katsuki, Kota; Kong, Gee Soo; Nakai, Mutsumi; Passchier, Sandra; Pekar, Stephen F.; Riesselman, Christina; Sakai, Toyosaburo; Shrivastava, Prakash K.; Sugisaki, Saiko; Tuo, Shouting; van de Flierdt, Tina; Welsh, Kevin; Yamane, Masako

    2013-01-01

    The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52–50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ∼49–50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2–4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling. PMID:23720311

  12. Eocene cooling linked to early flow across the Tasmanian Gateway.

    PubMed

    Bijl, Peter K; Bendle, James A P; Bohaty, Steven M; Pross, Jörg; Schouten, Stefan; Tauxe, Lisa; Stickley, Catherine E; McKay, Robert M; Röhl, Ursula; Olney, Matthew; Sluijs, Appy; Escutia, Carlota; Brinkhuis, Henk

    2013-06-11

    The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52-50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ~49-50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2-4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.

  13. Film Cooling Flow Effects on Post-Combustor Trace Chemistry

    NASA Technical Reports Server (NTRS)

    Wey, Thomas; Liu, Nan-Suey

    2003-01-01

    Film cooling injection is widely applied in the thermal design of turbomachinery, as it contributes to achieve higher operating temperature conditions of modern gas turbines, and to meet the requirements for reliability and life cycles. It is a significant part of the high-pressure turbine system. The film cooling injection, however, interacts with the main flow and is susceptible to have an influence on the aerodynamic performance of the cooled components, and through that may cause a penalty on the overall efficiency of the gas turbine. The main reasons are the loss of total pressure resulting from mixing the cooling air with mainstream and the reduction of the gas stagnation temperature at the exit of the combustion chamber to a lower value at the exit of nozzle guide vane. In addition, the impact of the injected air on the evolution of the trace species of the hot gas is not yet quite clear. This work computationally investigates the film cooling influence on post-combustor trace chemistry, as trace species in aircraft exhaust affect climate and ozone.

  14. EVOLUTION OF SUPER STAR CLUSTER WINDS WITH STRONG COOLING

    SciTech Connect

    Wuensch, Richard; Palous, Jan; Silich, Sergiy; Tenorio-Tagle, Guillermo; Munoz-Tunon, Casiana

    2011-10-20

    We study the evolution of super star cluster winds driven by stellar winds and supernova explosions. Time-dependent rates at which mass and energy are deposited into the cluster volume, as well as the time-dependent chemical composition of the re-inserted gas, are obtained from the population synthesis code Starburst99. These results are used as input for a semi-analytic code which determines the hydrodynamic properties of the cluster wind as a function of cluster age. Two types of winds are detected in the calculations. For the quasi-adiabatic solution, all of the inserted gas leaves the cluster in the form of a stationary wind. For the bimodal solution, some of the inserted gas becomes thermally unstable and forms dense warm clumps which accumulate inside the cluster. We calculate the evolution of the wind velocity and energy flux and integrate the amount of accumulated mass for clusters of different mass, radius, and initial metallicity. We also consider conditions with low heating efficiency of the re-inserted gas or mass loading of the hot thermalized plasma with the gas left over from star formation. We find that the bimodal regime and the related mass accumulation occur if at least one of the two conditions above is fulfilled.

  15. Analysis of Turbine Blade Relative Cooling Flow Factor Used in the Subroutine Coolit Based on Film Cooling Correlations

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.

    2015-01-01

    Heat transfer correlations of data on flat plates are used to explore the parameters in the Coolit program used for calculating the quantity of cooling air for controlling turbine blade temperature. Correlations for both convection and film cooling are explored for their relevance to predicting blade temperature as a function of a total cooling flow which is split between external film and internal convection flows. Similar trends to those in Coolit are predicted as a function of the percent of the total cooling flow that is in the film. The exceptions are that no film or 100 percent convection is predicted to not be able to control blade temperature, while leaving less than 25 percent of the cooling flow in the convection path results in nearing a limit on convection cooling as predicted by a thermal effectiveness parameter not presently used in Coolit.

  16. Numerical Flow Visualization in Basic- and Hyper-Cluster Spheres

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Athavale, M. M.; Braun, M. J.; Lattime, S.

    1997-01-01

    Packed spherical particle beds have wide applications throughout the process industry and are usually analyzed using an appropriate combination of laminar and turbulent flows with empirically derived coefficients of which the Ergun (1952) relation is probably the best known. The 3-D complexity of the void distribution within the beds has precluded detailed studies of sphere clusters. Numerical modeling and flow vector visualization for the basic tetra- and hexa-sphere clusters and two hyper-sphere clusters are presented at two Reynolds numbers, 400 and 1200. Cutting planes are used to enable visualization of the complex flows generated within the sphere clusters and are discussed herein. The boundary conditions and flow fields for the simple clusters are also compared to the hyper-clusters with larger variations found for hexa-clusters.

  17. SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

    SciTech Connect

    Blanchard, Peter K.; Bayliss, Matthew B.; McDonald, Michael; Dahle, Hakon; Gladders, Michael D.; Sharon, Keren; Mushotzky, Richard

    2013-07-20

    The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminosity and star formation, we measure, for a sample of 89 SL clusters, the fraction of clusters that have [O II]{lambda}{lambda}3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 A break, D{sub 4000}, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R{sub arc}, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D{sub 4000} as a function of R{sub arc}, a proxy observable for SL cross-sections. D{sub 4000} is constant with all values of R{sub arc}, and the [O II] emission fractions show no dependence on R{sub arc} for R{sub arc} > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R{sub arc} < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections.

  18. How unusual is the cool-core radio halo cluster CL1821+643?

    NASA Astrophysics Data System (ADS)

    Kale, Ruta; Parekh, Viral

    2016-07-01

    Massive galaxy clusters with cool cores typically host diffuse radio sources called mini-haloes, whereas, those with non-cool cores host radio haloes. We attempt to understand the unusual nature of the cool-core galaxy cluster CL1821+643, which hosts a megaparsec-scale radio halo, using new radio observations and morphological analysis of its intra-cluster medium. We present the Giant Metrewave Radio Telescope (GMRT) 610-MHz image of the radio halo. The spectral index α, defined as S ∝ ν-α, of the radio halo is 1.0 ± 0.1 over the frequency range of 323-610-1665 MHz. Archival Chandra X-ray data were used to make surface brightness and temperature maps. The morphological parameters Gini, M20 and concentration (C) were calculated on X-ray surface brightness maps by including and excluding the central quasar (H1821+643) in the cluster. We find that the cluster CL1821+643, excluding the quasar, is a non-relaxed cluster as seen in the morphological parameter planes. It occupies the same region as other merging radio halo clusters in the temperature versus morphology parameter plane. We conclude that this cluster has experienced a non-core-disruptive merger.

  19. Removing Cool Cores and Central Metallicity Peaks in Galaxy Clusters with Powerful Active Galactic Nucleus Outbursts

    NASA Astrophysics Data System (ADS)

    Guo, Fulai; Mathews, William G.

    2010-07-01

    Recent X-ray observations of galaxy clusters suggest that cluster populations are bimodally distributed according to central gas entropy and are separated into two distinct classes: cool core (CC) and non-cool core (NCC) clusters. While it is widely accepted that active galactic nucleus (AGN) feedback plays a key role in offsetting radiative losses and maintaining many clusters in the CC state, the origin of NCC clusters is much less clear. At the same time, a handful of extremely powerful AGN outbursts have recently been detected in clusters, with a total energy ~1061-1062 erg. Using two-dimensional hydrodynamic simulations, we show that if a large fraction of this energy is deposited near the centers of CC clusters, which is likely common due to dense cores, these AGN outbursts can completely remove CCs, transforming them to NCC clusters. Our model also has interesting implications for cluster abundance profiles, which usually show a central peak in CC systems. Our calculations indicate that during the CC to NCC transformation, AGN outbursts efficiently mix metals in cluster central regions and may even remove central abundance peaks if they are not broad enough. For CC clusters with broad central abundance peaks, AGN outbursts decrease peak abundances, but cannot effectively destroy the peaks. Our model may simultaneously explain the contradictory (possibly bimodal) results of abundance profiles in NCC clusters, some of which are nearly flat, while others have strong central peaks similar to those in CC clusters. A statistical analysis of the sizes of central abundance peaks and their redshift evolution may shed interesting insights on the origin of both types of NCC clusters and the evolution history of thermodynamics and AGN activity in clusters.

  20. Jammed Clusters and Non-locality in Dense Granular Flows

    NASA Astrophysics Data System (ADS)

    Kharel, Prashidha; Rognon, Pierre

    We investigate the micro-mechanisms underpinning dense granular flow behaviour from a series of DEM simulations of pure shear flows of dry grains. We observe the development of transient clusters of jammed particles within the flow. Typical size of such clusters is found to scale with the inertial number with a power law that is similar to the scaling of shear-rate profile relaxation lengths observed previously. Based on the simple argument that transient clusters of size l exist in the dense flow regime, the formulation of steady state condition for non-homogeneous shear flow results in a general non-local relation, which is similar in form to the non-local relation conjectured for soft glassy flows. These findings suggest the formation of jammed clusters to be the key micro-mechanism underpinning non-local behaviour in dense granular flows. Particles and Grains Laboratory, School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia.

  1. Origin and dynamics of emission line clouds in cooling flow environments

    NASA Technical Reports Server (NTRS)

    Loewenstein, Michael

    1990-01-01

    The author suggests that since clouds are born co-moving in a turbulent intra-cluster medium (ICM), the allowed parameter space can now be opened up to a more acceptable range. Large-scale motions can be driven in the central parts of cooling flows by a number of mechanisms including the motion of the central and other galaxies, and the dissipation of advected, focussed rotational and magnetic energy. In addition to the velocity width paradox, two other paradoxes (Heckman et al. 1989) can be solved if the ICM is turbulent. Firstly, the heating source for the emission line regions has always been puzzling - line luminosities are extremely high for a given (optical or radio) galaxy luminosity compared to those in non-cooling flow galaxies, therefore a mechanism peculiar to cooling flows must be at work. However most, if not all, previously suggested heating mechanisms either fail to provide enough ionization or give the wrong line ratios, or both. The kinetic energy in the turbulence provides a natural energy source if it can be efficiently converted to cloud heat. Researchers suggest that this can be done via magneto-hydrodynamic waves through plasma slip. Secondly, while the x ray observations indicate extended mass deposition, the optical line emission is more centrally concentrated. Since many of the turbulence-inducing mechanisms are strongest in the central regions of the ICM, so is the method of heating. In other words material is dropping out everywhere but only being lit up in the center.

  2. Misty Mountain clustering: application to fast unsupervised flow cytometry gating

    PubMed Central

    2010-01-01

    Background There are many important clustering questions in computational biology for which no satisfactory method exists. Automated clustering algorithms, when applied to large, multidimensional datasets, such as flow cytometry data, prove unsatisfactory in terms of speed, problems with local minima or cluster shape bias. Model-based approaches are restricted by the assumptions of the fitting functions. Furthermore, model based clustering requires serial clustering for all cluster numbers within a user defined interval. The final cluster number is then selected by various criteria. These supervised serial clustering methods are time consuming and frequently different criteria result in different optimal cluster numbers. Various unsupervised heuristic approaches that have been developed such as affinity propagation are too expensive to be applied to datasets on the order of 106 points that are often generated by high throughput experiments. Results To circumvent these limitations, we developed a new, unsupervised density contour clustering algorithm, called Misty Mountain, that is based on percolation theory and that efficiently analyzes large data sets. The approach can be envisioned as a progressive top-down removal of clouds covering a data histogram relief map to identify clusters by the appearance of statistically distinct peaks and ridges. This is a parallel clustering method that finds every cluster after analyzing only once the cross sections of the histogram. The overall run time for the composite steps of the algorithm increases linearly by the number of data points. The clustering of 106 data points in 2D data space takes place within about 15 seconds on a standard laptop PC. Comparison of the performance of this algorithm with other state of the art automated flow cytometry gating methods indicate that Misty Mountain provides substantial improvements in both run time and in the accuracy of cluster assignment. Conclusions Misty Mountain is fast, unbiased

  3. Efficient generation of fusion neutrons from cryogenically cooled heteronuclear clusters irradiated by intense femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Lu, Haiyang; Li, Song; Xu, Yi; Guo, Xiaoyang; Leng, Yuxin; Liu, Jiansheng; Shen, Baifei; Li, Ruxin; Xu, Zhizhan

    2014-02-01

    We present experimental studies on the conversion efficiency of fusion neutrons generated from Coulomb explosion of cryogenically cooled heteronuclear deuterated methane (CD4) clusters irradiated by intense femtosecond laser pulses. A stronger nonlinear relationship between the cluster size and the stagnation temperature for CD4 clusters than that for monoatomic or diatomic clusters is revealed, resulting in marked increases in the average kinetic energy of deuterons and the fusion neutron yield. Finally, a significantly enhanced conversion efficiency of 1.9 × 107 neutrons/J of incident laser energy is achieved by lowering the stagnation temperature to 217 K under a backing pressure of 80 bars.

  4. POLYCYCLIC AROMATIC HYDROCARBONS, IONIZED GAS, AND MOLECULAR HYDROGEN IN BRIGHTEST CLUSTER GALAXIES OF COOL-CORE CLUSTERS OF GALAXIES

    SciTech Connect

    Donahue, Megan; Mark Voit, G.; Hoffer, Aaron; De Messieres, Genevieve E.; O'Connell, Robert W.; McNamara, Brian R.; Nulsen, Paul E. J. E-mail: voit@pa.msu.edu

    2011-05-01

    We present measurements of 5-25 {mu}m emission features of brightest cluster galaxies (BCGs) with strong optical emission lines in a sample of nine cool-core clusters of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. These systems provide a view of dusty molecular gas and star formation, surrounded by dense, X-ray-emitting intracluster gas. Past work has shown that BCGs in cool-core clusters may host powerful radio sources, luminous optical emission-line systems, and excess UV, while BCGs in other clusters never show this activity. In this sample, we detect polycyclic aromatic hydrocarbons (PAHs), extremely luminous, rotationally excited molecular hydrogen line emission, forbidden line emission from ionized gas ([Ne II] and [Ne III]), and infrared continuum emission from warm dust and cool stars. We show here that these BCGs exhibit more luminous forbidden neon and H{sub 2} rotational line emission than star-forming galaxies with similar total infrared luminosities, as well as somewhat higher ratios of 70 {mu}m/24 {mu}m luminosities. Our analysis suggests that while star formation processes dominate the heating of the dust and PAHs, a heating process consistent with suprathermal electron heating from the hot gas, distinct from star formation, is heating the molecular gas and contributing to the heating of the ionized gas in the galaxies. The survival of PAHs and dust suggests that dusty gas is somehow shielded from significant interaction with the X-ray gas.

  5. A Chandra Study of the Image Power Spectra of 41 Cool Core and Non-cool Core Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Zhang, Chenhao; Xu, Haiguang; Zhu, Zhenghao; Li, Weitian; Hu, Dan; Wang, Jingying; Gu, Junhua; Gu, Liyi; Zhang, Zhongli; Liu, Chengze; Zhu, Jie; Wu, Xiang-Ping

    2016-06-01

    In this work we propose a new diagnostic to segregate cool core (CC) clusters from non-CC (NCC) clusters by studying the two-dimensional power spectra of the X-ray images observed with the Chandra X-ray observatory. Our sample contains 41 members (z=0.01{--}0.54) which are selected from the Chandra archive when a high photon count, an adequate angular resolution, a relatively complete detector coverage, and coincident CC-NCC classifications derived with three traditional diagnostics are simultaneously guaranteed. We find that in the log-log space the derived image power spectra can be well represented by a constant model component at large wavenumbers, while at small wavenumbers a power excess beyond the constant component appears in all clusters, with a clear tendency that the excess is stronger in CC clusters. By introducing a new CC diagnostic parameter, i.e., the power excess index (PEI), we classify the clusters in our sample and compare the results with those obtained with three traditional CC diagnostics. We find that the results agree with each other very well. By calculating the PEI values of the simulated clusters, we find that the new diagnostic works well at redshifts up to 0.5 for intermediately sized and massive clusters with a typical Chandra or XMM-Newton pointing observation. The new CC diagnostic has several advantages over its counterparts, e.g., it is free of the effects of the commonly seen centroid shift of the X-ray halo caused by merger event, and the corresponding calculation is straightforward, almost irrelevant to the complicated spectral analysis.

  6. Numerical analysis of hypersonic turbulent film cooling flows

    NASA Technical Reports Server (NTRS)

    Chen, Y. S.; Chen, C. P.; Wei, H.

    1992-01-01

    As a building block, numerical capabilities for predicting heat flux and turbulent flowfields of hypersonic vehicles require extensive model validations. Computational procedures for calculating turbulent flows and heat fluxes for supersonic film cooling with parallel slot injections are described in this study. Two injectant mass flow rates with matched and unmatched pressure conditions using the database of Holden et al. (1990) are considered. To avoid uncertainties associated with the boundary conditions in testing turbulence models, detailed three-dimensional flowfields of the injection nozzle were calculated. Two computational fluid dynamics codes, GASP and FDNS, with the algebraic Baldwin-Lomax and k-epsilon models with compressibility corrections were used. It was found that the B-L model which resolves near-wall viscous sublayer is very sensitive to the inlet boundary conditions at the nozzle exit face. The k-epsilon models with improved wall functions are less sensitive to the inlet boundary conditions. The testings show that compressibility corrections are necessary for the k-epsilon model to realistically predict the heat fluxes of the hypersonic film cooling problems.

  7. Influence of Flow Rotation Within a Cooling Tower on the Aerodynamic Interaction with Crosswind Flow

    NASA Astrophysics Data System (ADS)

    Kashani, M. M. Hemmasian; Dobrego, K. V.

    2014-03-01

    Environmental crosswind changes the aerodynamic pattern inside a cooling tower, destroys uniform and axisymmetric distribution of flow at its inlet and outlet, and may degrade fill zone performance. In this paper, the effect of flow rotation in the over-shower zone of a natural draft cooling tower (NDCT) on the aerodynamic interaction with crosswind is studied numerically. The 3D geometry of an actual NDCT and three models of induced rotation velocity fields are utilized for simulation. It is demonstrated that flow rotation results in homogenization of the aerodynamic field in the over-shower zone. The inhomogeneity of the velocity field in the outlet cross section decreases linearly with rotation intensification. The effect of main stream switching under strong wind conditions is found. It is shown that even moderate flow rotation eliminates this effect.

  8. Vortex generating flow passage design for increased film-cooling effectiveness and surface coverage. [aircraft engine blade cooling

    NASA Technical Reports Server (NTRS)

    Papell, S. S.

    1984-01-01

    The fluid mechanics of the basic discrete hole film cooling process is described as an inclined jet in crossflow and a cusp shaped coolant flow channel contour that increases the efficiency of the film cooling process is hypothesized. The design concept requires the channel to generate a counter rotating vortex pair secondary flow within the jet stream by virture of flow passage geometry. The interaction of the vortex structures generated by both geometry and crossflow was examined in terms of film cooling effectiveness and surface coverage. Comparative data obtained with this vortex generating coolant passage showed up to factors of four increases in both effectiveness and surface coverage over that obtained with a standard round cross section flow passage. A streakline flow visualization technique was used to support the concept of the counter rotating vortex pair generating capability of the flow passage design.

  9. Studying the Nearest Non-Cool Core Galaxy Cluster with XMM-Newton and Suzaku

    NASA Astrophysics Data System (ADS)

    Wong, Ka-Wah

    X-ray studies of the most nearby galaxy clusters have proved to provide new insights and surprising results compared to studying their more distant counterparts. On small scales within the central ~50 kpc region, the thermodynamic and abundance structures of hot gas within clusters have been mapped to a spatial resolution of a few kpc for the nearest galaxy clusters (e.g., Virgo and Fornax) with high spatial resolution X-ray telescopes such as Chandra or XMM-Newton. The results of these high resolution studies challenge the current picture of the metal enrichment processes in the intracluster medium (ICM), suggesting that the ICM in the central region is primarily enriched by core-collapse supernovae instead of Type Ia supernovae. On a large scale, a few nearby clusters (e.g., Perseus and Virgo) have been mapped with mosaic Suzaku pointings out to their virial radii of Mpc order (or degrees order in angular scale). These results indicate that cluster outskirts are not that simple: near the virial radius, the surface brightness of the ICM is higher and the measured entropy is lower than predictions by self-similar models. These suggest that the ICM in the outer region may be clumpy or that collisional equilibrium may not be achieved due to its very low density. Antlia is the third nearest galaxy cluster that was highly ignored in X-ray in the sky. It is also the nearest non-cool core cluster with a similar low temperature as the cool core Virgo Cluster, allowing us to make a direct comparison to the cool core counterpart in our neighborhood. We request NASA ADAP support for our comprehensive program to study the Antlia Cluster in detail with our recently approved 180 ks XMM-Newton (AO- 11) and 204 ks Suzaku (AO-07) observations, together with the existing XMM-Newton, Suzaku, and ROSAT data in the archive. With our deep XMM-Newton data, we will determine the thermodynamic structures (e.g., density, temperature, entropy, etc) in a scale of few kpc. We will also

  10. COOLING TIME, FREEFALL TIME, AND PRECIPITATION IN THE CORES OF ACCEPT GALAXY CLUSTERS

    SciTech Connect

    Voit, G. Mark; Donahue, Megan

    2015-01-20

    Star formation in the universe's largest galaxies—the ones at the centers of galaxy clusters—depends critically on the thermodynamic state of their hot gaseous atmospheres. Central galaxies with low-entropy, high-density atmospheres frequently contain multiphase star-forming gas, while those with high-entropy, low-density atmospheres never do. The dividing line between these two populations in central entropy, and therefore central cooling time, is amazingly sharp. Two hypotheses have been proposed to explain the dichotomy. One points out that thermal conduction can prevent radiative cooling of cluster cores above the dividing line. The other holds that cores below the dividing line are subject to thermal instability that fuels the central active galactic nucleus (AGN) through a cold-feedback mechanism. Here we explore those hypotheses with an analysis of the Hα properties of ACCEPT galaxy clusters. We find that the two hypotheses are likely to be complementary. Our results support a picture in which cold clouds inevitably precipitate out of cluster cores in which cooling outcompetes thermal conduction and rain down on the central black hole, causing AGN feedback that stabilizes the cluster core. In particular, the observed distribution of the cooling-time to freefall-time ratio is nearly identical to that seen in simulations of this cold-feedback process, implying that cold-phase accretion, and not Bondi-like accretion of hot-phase gas, is responsible for the AGN feedback that regulates star formation in large galaxies.

  11. Linear-optical simulation of the cooling of a cluster-state Hamiltonian system.

    PubMed

    Aguilar, G H; Kolb, T; Cavalcanti, D; Aolita, L; Chaves, R; Walborn, S P; Souto Ribeiro, P H

    2014-04-25

    A measurement-based quantum computer could consist of a local-gapped Hamiltonian system, whose thermal states-at sufficiently low temperature-are universal resources for the computation. Initialization of the computer would correspond to cooling the system. We perform an experimental quantum simulation of such a cooling process with entangled photons. We prepare three-qubit thermal cluster states exploiting the equivalence between local dephasing and thermalization for these states. This allows us to tune the system's temperature by changing the dephasing strength. We monitor the entanglement as the system cools down and observe the transitions from separability to bound entanglement, and then to free entanglement. We also analyze the performance of the system for measurement-based single-qubit state preparation. These studies constitute a basic characterization of experimental cluster-state computation under imperfect conditions.

  12. Red blood cell clustering in Poiseuille microcapillary flow

    NASA Astrophysics Data System (ADS)

    Tomaiuolo, Giovanna; Lanotte, Luca; Ghigliotti, Giovanni; Misbah, Chaouqi; Guido, Stefano

    2012-05-01

    Red blood cells (RBC) flowing in microcapillaries tend to associate into clusters, i.e., small trains of cells separated from each other by a distance comparable to cell size. This process is usually attributed to slower RBCs acting to create a sequence of trailing cells. Here, based on the first systematic investigation of collective RBC flow behavior in microcapillaries in vitro by high-speed video microscopy and numerical simulations, we show that RBC size polydispersity within the physiological range does not affect cluster stability. Lower applied pressure drops and longer residence times favor larger RBC clusters. A limiting cluster length, depending on the number of cells in a cluster, is found by increasing the applied pressure drop. The insight on the mechanism of RBC clustering provided by this work can be applied to further our understanding of RBC aggregability, which is a key parameter implicated in clotting and thrombus formation.

  13. Diffuse Extreme-Ultraviolet Emission from the Coma Cluster: Evidence for Rapidly Cooling Gases at Submegakelvin Temperatures

    PubMed

    Lieu; Mittaz; Bowyer; Breen; Lockman; Murphy; Hwang

    1996-11-22

    The central region of the Coma cluster of galaxies was observed in the energy band from 0.065 to 0.245 kiloelectron volts by the Deep Survey telescope aboard the Extreme Ultraviolet Explorer. A diffuse emission halo of angular diameter approximately 30 arc minutes was detected. The extreme-ultraviolet (EUV) emission level exceeds that expected from the x-ray temperature gas in Coma. This halo suggests the presence of two more phases in the emitting gas, one at a temperature of approximately 2 x 10(6) kelvin and the other at approximately 8 x 10(5) kelvin. The latter phase cools rapidly and, in steady state, would have produced cold matter with a mass of approximately 10(14) solar masses within the EUV halo. Although a similar EUV enhancement was discovered in the Virgo cluster, this detection in Coma applies to a noncooling flow system. PMID:8910264

  14. Diffuse Extreme-Ultraviolet Emission from the Coma Cluster: Evidence for Rapidly Cooling Gases at Submegakelvin Temperatures

    PubMed

    Lieu; Mittaz; Bowyer; Breen; Lockman; Murphy; Hwang

    1996-11-22

    The central region of the Coma cluster of galaxies was observed in the energy band from 0.065 to 0.245 kiloelectron volts by the Deep Survey telescope aboard the Extreme Ultraviolet Explorer. A diffuse emission halo of angular diameter approximately 30 arc minutes was detected. The extreme-ultraviolet (EUV) emission level exceeds that expected from the x-ray temperature gas in Coma. This halo suggests the presence of two more phases in the emitting gas, one at a temperature of approximately 2 x 10(6) kelvin and the other at approximately 8 x 10(5) kelvin. The latter phase cools rapidly and, in steady state, would have produced cold matter with a mass of approximately 10(14) solar masses within the EUV halo. Although a similar EUV enhancement was discovered in the Virgo cluster, this detection in Coma applies to a noncooling flow system.

  15. Deep Chandra study of the truncated cool core of the Ophiuchus cluster

    NASA Astrophysics Data System (ADS)

    Werner, N.; Zhuravleva, I.; Canning, R. E. A.; Allen, S. W.; King, A. L.; Sanders, J. S.; Simionescu, A.; Taylor, G. B.; Morris, R. G.; Fabian, A. C.

    2016-08-01

    We present the results of a deep Chandra observation of the Ophiuchus cluster, the second brightest galaxy cluster in the X-ray sky. The cluster hosts a truncated cool core, with a temperature increasing from kT ˜ 1 keV in the core to kT ˜ 9 keV at r ˜ 30 kpc. Beyond r ˜ 30 kpc, the intracluster medium (ICM) appears remarkably isothermal. The core is dynamically disturbed with multiple sloshing-induced cold fronts, with indications for both Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The residual image reveals a likely subcluster south of the core at the projected distance of r ˜ 280 kpc. The cluster also harbours a likely radio phoenix, a source revived by adiabatic compression by gas motions in the ICM. Even though the Ophiuchus cluster is strongly dynamically active, the amplitude of density fluctuations outside of the cooling core is low, indicating velocities smaller than ˜100 km s-1. The density fluctuations might be damped by thermal conduction in the hot and remarkably isothermal ICM, resulting in our underestimate of gas velocities. We find a surprising, sharp surface brightness discontinuity, that is curved away from the core, at r ˜ 120 kpc to the south-east of the cluster centre. We conclude that this feature is most likely due to gas dynamics associated with a merger. The cooling core lacks any observable X-ray cavities and the active galactic nucleus (AGN) only displays weak, point-like radio emission, lacking lobes or jets. The lack of strong AGN activity may be due to the bulk of the cooling taking place offset from the central supermassive black hole.

  16. New XMM-Newton observation of the Phoenix cluster: properties of the cool core

    NASA Astrophysics Data System (ADS)

    Tozzi, P.; Gastaldello, F.; Molendi, S.; Ettori, S.; Santos, J. S.; De Grandi, S.; Balestra, I.; Rosati, P.; Altieri, B.; Cresci, G.; Menanteau, F.; Valtchanov, I.

    2015-08-01

    Aims: We present a spectral analysis of a deep (220 ks) XMM-Newton observation of the Phoenix cluster (SPT-CL J2344-4243). We also use Chandra archival ACIS-I data that are useful for modeling the properties of the central bright active galactic nucleus and global intracluster medium. Methods: We extracted CCD and reflection grating spectrometer (RGS) X-ray spectra from the core region to search for the signature of cold gas and to finally constrain the mass deposition rate in the cooling flow that is thought to be responsible for the massive star formation episode observed in the brightest cluster galaxy (BCG). Results: We find an average mass-deposition rate of Ṁ = 620 (-190 + 200)stat (-50 + 150)syst M⊙ yr-1 in the temperature range 0.3-3.0 keV from MOS data. A temperature-resolved analysis shows that a significant amount of gas is deposited at about 1.8 keV and above, while only upper limits on the order of hundreds of M⊙ yr-1 can be placed in the 0.3-1.8 keV temperature range. From pn data we obtain Ṁ = 210 (-80 + 85)stat (-35 + 60)syst M⊙ yr-1 in the 0.3-3.0 keV temperature range, while the upper limits from the temperature-resolved analysis are typically a factor of 3 lower than MOS data. No line emission from ionization states below Fe XXIII is seen above 12 Å in the RGS spectrum, and the amount of gas cooling below ~3 keV has a formal best-fit value Ṁ = 122-122+343 M⊙ yr-1. In addition, our analysis of the far-infrared spectral energy distribution of the BCG based on Herschel data provides a star formation rate (SFR) equal to 530 M⊙ yr-1 with an uncertainty of 10%, which is lower than previous estimates by a factor 1.5. Overall, current limits on the mass deposition rate from MOS data are consistent with the SFR observed in the BCG, while pn data prefer a lower value of Ṁ ~ SFR/ 3, which is inconsistent with the SFR at the 3σ confidence level. Conclusions: Current data are able to firmly identify a substantial amount of cooling gas only

  17. On the nature of local instabilities in rotating galactic coronae and cool cores of galaxy clusters

    SciTech Connect

    Nipoti, Carlo; Posti, Lorenzo

    2014-09-01

    A long-standing question is whether radiative cooling can lead to local condensation of cold gas in the hot atmospheres of galaxies and galaxy clusters. We address this problem by studying the nature of local instabilities in rotating, stratified, weakly magnetized, optically thin plasmas in the presence of radiative cooling and anisotropic thermal conduction. For both axisymmetric and nonaxisymmetric linear perturbations, we provide general equations which can be applied locally to specific systems to establish whether they are unstable and, in case of instability, to determine the kind of evolution (monotonically growing or overstable) and the growth rates of the unstable modes. We present results for models of rotating plasmas representative of Milky-Way-like galaxy coronae and cool-cores of galaxy clusters. We show that the unstable modes arise from a combination of thermal, magnetothermal, magnetorotational, and heat-flux-driven buoyancy instabilities. Local condensation of cold clouds tends to be hampered in cluster cool cores, while it is possible under certain conditions in rotating galactic coronae. If the magnetic field is sufficiently weak, then the magnetorotational instability is dominant even in these pressure-supported systems.

  18. Experimental flow coefficients of a full-coverage film-cooled-vane chamber

    NASA Technical Reports Server (NTRS)

    Meitner, P. L.; Hippensteele, S. A.

    1977-01-01

    Ambient- and elevated-temperature flow tests were performed on a four-times-actual-size model of an impingement- and film-cooled segment of a core engine turbine vane. Tests were conducted with the impingement and film cooling plates combined to form a chamber and also with each of the individual separated plates. For the combined tests, the proximity of the film cooling plate affected the flow of coolant through the impingement plate, but not conversely. Impingement flow is presented in terms of a discharge coefficient, and the film cooling flow discharging into still air with no main stream gas flow is presented in terms of a total pressure-loss coefficient. The effects of main stream gas flow on discharge from the film cooling holes are evaluated as a function of coolant to main-stream gas momentum flux ratio. A smoothing technique is developed that identifies and helps reduce flow measurement data scatter.

  19. ON THE ROAD TO MORE REALISTIC GALAXY CLUSTER SIMULATIONS: THE EFFECTS OF RADIATIVE COOLING AND THERMAL FEEDBACK PRESCRIPTIONS ON THE OBSERVATIONAL PROPERTIES OF SIMULATED GALAXY CLUSTERS

    SciTech Connect

    Skory, Stephen; Hallman, Eric; Burns, Jack O.; Skillman, Samuel W.; O'Shea, Brian W.; Smith, Britton D.

    2013-01-20

    Flux-limited X-ray surveys of galaxy clusters show that clusters come in two roughly equally proportioned varieties: 'cool core' clusters (CCs) and non-'cool core' clusters (NCCs). In previous work, we have demonstrated using cosmological N-body + Eulerian hydrodynamic simulations that NCCs are often consistent with early major merger events that destroy embryonic CCs. In this paper we extend those results and conduct a series of simulations using different methods of gas cooling and of energy and metal feedback from supernovae, where we attempt to produce a population of clusters with realistic central cooling times, entropies, and temperatures. We find that the use of metallicity-dependent gas cooling is essential to prevent early overcooling, and that adjusting the amount of energy and metal feedback can have a significant impact on observable X-ray quantities of the gas. We are able to produce clusters with more realistic central observable quantities than have previously been attained. However, there are still significant discrepancies between the simulated clusters and observations, which indicates that a different approach to simulating galaxies in clusters is needed. We conclude by looking toward a promising subgrid method of modeling galaxy feedback in clusters that may help to ameliorate the discrepancies between simulations and observations.

  20. Flow and heat transfer predictions for film cooling.

    PubMed

    Acharya, S; Tyagi, M; Hoda, A

    2001-05-01

    Film cooling flows are characterized by a row of jets injected at an angle from the blade surface or endwalls into the heated crossflow. The resulting flowfield is quite complex, and accurate predictions of the flow and heat transfer have been difficult to obtain, particularly in the near field of the injected jet. The flowfield is characterized by a spectrum of vortical structures including the dominant kidney vortex, the horse-shoe vortex, the wake vortices and the shear layer vortices. These anisotropic and unsteady structures are not well represented by empirical or ad-hoc turbulence models, and lead to inaccurate predictions in the near field of the jet. In this paper, a variety of modeling approaches have been reviewed, and the limitations of these approaches are identified. Recent emergence of Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) tools allow the resolution of the coherent structure dynamics, and it is shown in this paper, that such approaches provide improved predictions over that obtained with turbulence models. PMID:11460622

  1. New detections of radio minihalos in cool cores of galaxy clusters

    SciTech Connect

    Giacintucci, Simona; Markevitch, Maxim; Clarke, Tracy E.; Mazzotta, Pasquale

    2014-01-20

    Cool cores of some galaxy clusters exhibit faint radio 'minihalos'. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146, RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations. The radio luminosities of our minihalos and candidates are in the range of 10{sup 23-25} W Hz{sup –1} at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40-160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck. We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

  2. New Detections of Radio Minihalos in Cool Cores of Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Giacintucci, Simona; Markevitch, Maxim; Venturi, Tiziana; Clarke, Tracy E.; Cassano, Rossella; Mazzotta, Pasquale

    2013-01-01

    Cool cores of some galaxy clusters exhibit faint radio minihalos. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146,RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations.The radio luminosities of our minihalos and candidates are in the range of 102325 W Hz1 at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck.We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

  3. A 3.55 keV line from DM →a→γ: predictions for cool-core and non-cool-core clusters

    SciTech Connect

    Conlon, Joseph P.; Powell, Andrew J.

    2015-01-13

    We further study a scenario in which a 3.55 keV X-ray line arises from decay of dark matter to an axion-like particle (ALP), that subsequently converts to a photon in astrophysical magnetic fields. We perform numerical simulations of Gaussian random magnetic fields with radial scaling of the magnetic field magnitude with the electron density, for both cool-core 'Perseus' and non-cool-core 'Coma' electron density profiles. Using these, we quantitatively study the resulting signal strength and morphology for cool-core and non-cool-core clusters. Our study includes the effects of fields of view that cover only the central part of the cluster, the effects of offset pointings on the radial decline of signal strength and the effects of dividing clusters into annuli. We find good agreement with current data and make predictions for future analyses and observations.

  4. Passive cooling system for liquid metal cooled nuclear reactors with backup coolant flow path

    DOEpatents

    Hunsbedt, Anstein; Boardman, Charles E.

    1993-01-01

    A liquid metal cooled nuclear fission reactor plant having a passive auxiliary safety cooling system for removing residual heat resulting from fuel decay during reactor shutdown, or heat produced during a mishap. This reactor plant is enhanced by a backup or secondary passive safety cooling system which augments the primary passive auxiliary cooling system when in operation, and replaces the primary system when rendered inoperable.

  5. Modeling active galactic nucleus feedback in cool-core clusters: The formation of cold clumps

    SciTech Connect

    Li, Yuan; Bryan, Greg L.

    2014-07-10

    We perform high-resolution (15-30 pc) adaptive mesh simulations to study the impact of momentum-driven active galactic nucleus (AGN) feedback in cool-core clusters, focusing in this paper on the formation of cold clumps. The feedback is jet-driven with an energy determined by the amount of cold gas within 500 pc of the super-massive black hole. When the intracluster medium in the core of the cluster becomes marginally stable to radiative cooling, with the thermal instability to the free-fall timescale ratio t{sub TI}/t{sub ff} < 3-10, cold clumps of gas start to form along the propagation direction of the AGN jets. By tracing the particles in the simulations, we find that these cold clumps originate from low entropy (but still hot) gas that is accelerated by the jet to outward radial velocities of a few hundred km s{sup –1}. This gas is out of hydrostatic equilibrium and so can cool. The clumps then grow larger as they decelerate and fall toward the center of the cluster, eventually being accreted onto the super-massive black hole. The general morphology, spatial distribution, and estimated Hα morphology of the clumps are in reasonable agreement with observations, although we do not fully replicate the filamentary morphology of the clumps seen in the observations, probably due to missing physics.

  6. Modeling Active Galactic Nucleus Feedback in Cool-core Clusters: The Formation of Cold Clumps

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Bryan, Greg L.

    2014-07-01

    We perform high-resolution (15-30 pc) adaptive mesh simulations to study the impact of momentum-driven active galactic nucleus (AGN) feedback in cool-core clusters, focusing in this paper on the formation of cold clumps. The feedback is jet-driven with an energy determined by the amount of cold gas within 500 pc of the super-massive black hole. When the intracluster medium in the core of the cluster becomes marginally stable to radiative cooling, with the thermal instability to the free-fall timescale ratio t TI/t ff < 3-10, cold clumps of gas start to form along the propagation direction of the AGN jets. By tracing the particles in the simulations, we find that these cold clumps originate from low entropy (but still hot) gas that is accelerated by the jet to outward radial velocities of a few hundred km s-1. This gas is out of hydrostatic equilibrium and so can cool. The clumps then grow larger as they decelerate and fall toward the center of the cluster, eventually being accreted onto the super-massive black hole. The general morphology, spatial distribution, and estimated Hα morphology of the clumps are in reasonable agreement with observations, although we do not fully replicate the filamentary morphology of the clumps seen in the observations, probably due to missing physics.

  7. The regulation of star formation in cool-core clusters: imprints on the stellar populations of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Loubser, S. I.; Babul, A.; Hoekstra, H.; Mahdavi, A.; Donahue, M.; Bildfell, C.; Voit, G. M.

    2016-02-01

    A fraction of brightest cluster galaxies (BCGs) show bright emission in the ultraviolet and the blue part of the optical spectrum, which has been interpreted as evidence of recent star formation. Most of these results are based on the analysis of broad-band photometric data. Here, we study the optical spectra of a sample of 19 BCGs hosted by X-ray luminous galaxy clusters at 0.15 Cluster Comparison Project sample. We identify plausible star formation histories of the galaxies by fitting simple stellar populations as well as composite populations, consisting of a young stellar component superimposed on an intermediate/old stellar component, to accurately constrain their star formation histories. We detect prominent young (˜200 Myr) stellar populations in four of the 19 galaxies. Of the four, the BCG in Abell 1835 shows remarkable A-type stellar features indicating a relatively large population of young stars, which is extremely unusual even amongst star-forming BCGs. We constrain the mass contribution of these young components to the total stellar mass to be typically between 1 and 3 per cent, but rising to 7 per cent in Abell 1835. We find that the four of the BCGs with strong evidence for recent star formation (and only these four galaxies) are found within a projected distance of 5 kpc of their host cluster's X-ray peak, and the diffuse, X-ray gas surrounding the BCGs exhibits a ratio of the radiative cooling-to-free-fall time (tc/tff) of ≤10. These are also some of the clusters with the lowest central entropy. Our results are consistent with the predictions of the precipitation-driven star formation and active galactic nucleus feedback model, in which the radiatively cooling diffuse gas is subject to local thermal instabilities once the instability parameter tc/tff falls below ˜10, leading to the condensation and precipitation of cold gas. The number of galaxies in our sample where the host cluster satisfies all the

  8. Vibrational Relaxation of the Aqueous Proton in Acetonitrile: Ultrafast Cluster Cooling and Vibrational Predissociation.

    PubMed

    Ottosson, N; Liu, L; Bakker, H J

    2016-07-28

    We study the ultrafast O-H stretch vibrational relaxation dynamics of protonated water clusters embedded in a matrix of deuterated acetonitrile, using polarization-resolved mid-IR femtosecond spectroscopy. The clusters are produced by mixing triflic (trifluoromethanesulfonic) acid and H2O in molar ratios of 1:1, 1:2, and 1:3, thus varying the degree of hydration of the proton. At all hydration levels the excited O-H stretch vibration of the hydrated proton shows an ultrafast vibrational relaxation with a time constant T1 < 100 fs, leading to an ultrafast local heating of the protonated water cluster. This excess thermal energy, initially highly localized to the region of the excited proton, first re-distributes over the aqueous cluster and then dissipates into the surrounding acetonitrile matrix. For clusters with a triflic acid to H2O ratio of 1:3 these processes occur with time constants of 320 ± 20 fs and 1.4 ± 0.1 ps, respectively. The cooling of the clusters reveals a long-living, underlying transient absorption change with high anisotropy. We argue that this feature stems from the vibrational predissociation of a small fraction of the proton hydration structures, directly following the ultrafast infrared excitation. PMID:27333302

  9. Sloshing of the Magnetized Cool Gas in the Cores of Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    ZuHone, J. A.; Markevitch, M.; Lee, D.

    2011-01-01

    X-ray observations of many clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts". In relaxed clusters with cool cores, these edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. The smoothness of these edges has been interpreted as evidence for the stabilizing effect of magnetic fields "draped" around the front surfaces. To check this hypothesis, we perform high-resolution magnetohydrodynamics simulations of magnetized gas sloshing in galaxy clusters initiated by encounters with subclusters. We go beyond previous works on the simulation of cold fronts in a magnetized intracluster medium by simulating their formation in realistic, idealized mergers with high resolution ((Delta)x approx. 2 kpc). Our simulations sample a parameter space of plausible initial magnetic field strengths and field configurations. In the simulations, we observe strong velocity shears associated with the cold fronts amplifying the magnetic field along the cold front surfaces, increasing the magnetic field strength in these layers by up to an order of magnitude, and boosting the magnetic pressure up to near-equipartition with thermal pressure in some cases. In these layers, the magnetic field becomes strong enough to stabilize the cold fronts against Kelvin-Helmholtz instabilities, resulting in sharp, smooth fronts as those seen in observations of real clusters. These magnetic fields also result in strong suppression of mixing of high and low-entropy gas in the cluster, seen in our simulations of mergers in the absence of a magnetic field. As a result, the heating of the core due to sloshing is very modest and is unable to stave off a cooling catastrophe.

  10. Kinetic AGN feedback effects on cluster cool cores simulated using SPH

    NASA Astrophysics Data System (ADS)

    Barai, Paramita; Murante, Giuseppe; Borgani, Stefano; Gaspari, Massimo; Granato, Gian Luigi; Monaco, Pierluigi; Ragone-Figueroa, Cinthia

    2016-09-01

    We implement novel numerical models of AGN feedback in the SPH code GADGET-3, where the energy from a supermassive black hole (BH) is coupled to the surrounding gas in the kinetic form. Gas particles lying inside a bi-conical volume around the BH are imparted a one-time velocity (10 000 km s-1) increment. We perform hydrodynamical simulations of isolated cluster (total mass 1014 h-1 M⊙), which is initially evolved to form a dense cool core, having central T ≤ 106 K. A BH resides at the cluster centre, and ejects energy. The feedback-driven fast wind undergoes shock with the slower moving gas, which causes the imparted kinetic energy to be thermalized. Bipolar bubble-like outflows form propagating radially outward to a distance of a few 100 kpc. The radial profiles of median gas properties are influenced by BH feedback in the inner regions (r < 20-50 kpc). BH kinetic feedback, with a large value of the feedback efficiency, depletes the inner cool gas and reduces the hot gas content, such that the initial cool core of the cluster is heated up within a time 1.9 Gyr, whereby the core median temperature rises to above 107 K, and the central entropy flattens. Our implementation of BH thermal feedback (using the same efficiency as kinetic), within the star formation model, cannot do this heating, where the cool core remains. The inclusion of cold gas accretion in the simulations produces naturally a duty cycle of the AGN with a periodicity of 100 Myr.

  11. Intercooler cooling-air weight flow and pressure drop for minimum drag loss

    NASA Technical Reports Server (NTRS)

    Reuter, J George; Valerino, Michael F

    1944-01-01

    An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.

  12. Optimum design of bipolar plates for separate air flow cooling system of PEM fuel cells stacks

    NASA Astrophysics Data System (ADS)

    Franco, Alessandro

    2015-12-01

    The paper discusses about thermal management of PEM fuel cells. The objective is to define criteria and guidelines for the design of the air flow cooling system of fuel cells stacks for different combination of power density, bipolar plates material, air flow rate, operating temperature It is shown that the optimization of the geometry of the channel permits interesting margins for maintaining the use of separate air flow cooling systems for high power density PEM fuel cells.

  13. The cooling rates of pahoehoe flows: The importance of lava porosity

    NASA Technical Reports Server (NTRS)

    Jones, Alun C.

    1993-01-01

    Many theoretical models have been put forward to account for the cooling history of a lava flow; however, only limited detailed field data exist to validate these models. To accurately model the cooling of lava flows, data are required, not only on the heat loss mechanisms, but also on the surface skin development and the causes of differing cooling rates. This paper argues that the cause of such variations in the cooling rates are attributed, primarily, to the vesicle content and degassing history of the lava.

  14. Constraints on molecular gas in cooling flows and powerful radio galaxies

    NASA Technical Reports Server (NTRS)

    O'Dea, Christopher P.; Baum, Stefi A.; Maloney, Philip R.; Tacconi, Linda J.; Sparks, William B.

    1994-01-01

    We searched for molecular gas in a heterogeneous sample of five radio-loud galaxies (three of which are inferred to be in cooling flow clusters) using the Swedish-European Southern Observatory (Swedish-ESO) Submillimeter Telescope. We do not detect CO in emission in any of the cluster sources at a 3 sigma level of typically 15 mK. White et al. (1991) have suggested column densities of N(sub H) approximately 10(exp 21)/sq cm in these clusters with a spatial covering factor of order unity and a total mass of M approximately 10(exp 12) solar mass. Our limits are inconsistent with these column densities and spatial covering factor unless the molecular gas is very cold (kinetic temperature close to 2.7 K) or there only a few clouds along each line of sight. We estimate minimum temperatures in the range approximately 20-30 K. We find that clouds of atomic and molecular hydrogen require strict fine-tuning of parameter space in order to satisfy the requirements for the large column densities N(sub H) approximately 10(exp 21)/sq cm, unit covering factor, and a small number of clouds along the line of sight. Currently the only way molecular gas can be responsible for the X-ray absorption and still be consistent with our observations is if (1) there is of order one cloud along the line of sight and (2) the optical depth in C-12 1 to 0 is less than 10. In addition, we present a Very Large Array (VLA) image of NGC 4696 which suggests this object is a member of the class of 'amorphous cooling flow radio sources.' The C-12 1 to 0 line is detected in emission in PKS 0634-206, a classical double radio galaxy which is rich in extended optical emission line gas. The estimated molecular gas mass is M(sub mol) approximately 3 x 10(exp 9) solar mass and is much larger than that of the ionized component detected in hydrogen alpha suggesting that the emission-line nebula is radiation bounded.

  15. Abell 262 and RXJ0341: Two Brightest Cluster Galaxies with Line Emission Blanketing a Cool Core

    NASA Astrophysics Data System (ADS)

    Edwards, Louise O. V.; Heng, Renita

    2014-08-01

    Over the last decade, integral field (IFU) analysis of the brightest cluster galaxies (BCGs) in several cool core clusters has revealed the central regions of these massive old red galaxies to be far from dead. Bright line emission alongside extended X-ray emission links nearby galaxies, is superposed upon vast dust lanes and extends out in long thin filaments from the galaxy core. Yet, to date no unifying picture has come into focus, and the activity across systems is currently seen as a grab-bag of possibile emission line mechanisms. Our primary goal is to work toward a consistent picture for why the BCGs seem are undergoing a renewed level of activity. One problem is most of the current data remains focused on mapping the very core of the BCG, but neglects surrounding galaxies. We propose to discover the full extent of line emission in a complementary pair of BCGs. In Abell 262, an extensive dust patch screens large portions of an otherwise smooth central galaxy, whereas RXJ0341 appears to be a double-core dust free BCG. We will map the full extent of the line emission in order to deduce whether the line emission is a product of local interactions, or the large-scale cluster X-ray gas. The narrow band filter set and large FOV afforded by the the Mayall MOSAIC-1 (MOSA) imager allows us to concurrently conduct an emission line survey of both clusters, locating all line emitting members and beginning a search for the effect of the environment of the different regions (outskirts vs. cluster core) out to the virial radius. We will combine our results with publically available data from 2MASS to determine the upper limits on specific star formation in the BCG and other cluster galaxies within the cluster virial radius.

  16. Turbine systems and methods for using internal leakage flow for cooling

    DOEpatents

    Hernandez, Nestor; Gazzillo, Clement; Boss, Michael J.; Parry, William; Tyler, Karen J.

    2010-02-09

    A cooling system for a turbine with a first section and a second section. The first section may include a first line for diverting a first flow with a first temperature from the first section, a second line for diverting a second flow with a second temperature less than the first temperature from the first section, and a merged line for directing a merged flow of the first flow and the second flow to the second section.

  17. Constraining star formation rates in cool-core brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Mittal, Rupal; Whelan, John T.; Combes, Françoise

    2015-07-01

    We used broad-band imaging data for 10 cool-core brightest cluster galaxies (BCGs) and conducted a Bayesian analysis using stellar population synthesis to determine the likely properties of the constituent stellar populations. Determination of ongoing star formation rates (SFRs), in particular, has a direct impact on our understanding of the cooling of the intracluster medium (ICM), star formation and AGN-regulated feedback. Our model consists of an old stellar population and a series of young stellar components. We calculated marginalized posterior probability distributions for various model parameters and obtained 68 per cent plausible intervals from them. The 68 per cent plausible interval on the SFRs is broad, owing to a wide range of models that are capable of fitting the data, which also explains the wide dispersion in the SFRs available in the literature. The ranges of possible SFRs are robust and highlight the strength in such a Bayesian analysis. The SFRs are correlated with the X-ray mass deposition rates (the former are factors of 4-50 lower than the latter), implying a picture where the cooling of the ICM is a contributing factor to star formation in cool-core BCGs. We find that 9 out of 10 BCGs have been experiencing starbursts since 6 Gyr ago. While four out of nine BCGs seem to require continuous SFRs, five out of nine seem to require periodic star formation on intervals ranging from 20 to 200 Myr. This time-scale is similar to the cooling time of the ICM in the central (<5 kpc) regions.

  18. Active Control of Jets in Cross-Flow for Film Cooling Applications

    NASA Technical Reports Server (NTRS)

    Nikitopoulos, Dimitris E.

    2003-01-01

    Jets in cross-flow have applications in film cooling of gas turbine vanes, blades and combustor liners. Their cooling effectiveness depends on the extent to which the cool jet-fluid adheres to the cooled component surface. Lift-off of the cooling jet flow or other mechanisms promoting mixing, cause loss of cooling effectiveness as they allow the hot "free-stream" fluid to come in contact with the component surface. The premise of this project is that cooling effectiveness can be improved by actively controlling (e.9. forcing, pulsing) the jet flow. Active control can be applied to prevent/delay lift-off and suppress mixing. Furthermore, an actively controlled film-cooling system coupled with appropriate sensory input (e.g. temperature or heat flux) can adapt to spatial and temporal variations of the hot-gas path. Thus, it is conceivable that the efficiency of film-cooling systems can be improved, resulting in coolant fluid economy. It is envisioned that Micro Electro-Mechanical Systems (MEMS) will play a role in the realization of such systems. As a first step, a feasibility study will be conducted to evaluate the concept, identify actuation and sensory elements and develop a control strategy. Part of this study will be the design of a proof-of-concept experiment and collection of necessary data.

  19. Flow generated around particle clusters in a rotating ultrasonic waveguide.

    PubMed

    Whitworth, G

    1998-09-01

    A chamber cavity, which has a square cross section and pressure-release walls, is used to produce a well-defined, 160-kHz standing ultrasonic field. A suspension of latex microspheres in aqueous metrizamide fills the chamber. The chamber rotates about a horizontal axis producing the centripetal force necessary to contain the buoyant spheres in the axial region. At low particle concentrations, clusters of microspheres form at half-wavelength intervals near the axial positions of acoustic pressure amplitude (p0) minima, as expected because of rotational and acoustic radiation forces. At higher concentrations, additional particle distributions are often seen that suggest the presence of flow. When high concentrations of larger particles are used, small clusters also form at axial positions of p0 maxima. Theory for acoustic streaming in a rotating fluid predicts flow speeds that are too small to account for the observed flow. Reasonable agreement with observations is obtained using a theory for flow generated by the buoyant gravitational force acting on the clusters. PMID:9745732

  20. Numerical modelling of electrovortex and heat flows in dc electric arc furnace with cooling bottom electrode

    NASA Astrophysics Data System (ADS)

    Kazak, Oleg

    2014-05-01

    The article is devoted to the numerical modelling of electrovortex and convection flows in DC electric arc furnace with the cooling bottom electrode. The shear stress on the fettle area are offered as criteria for the estimation of vortex flows influence on the increased wearing of fettle. It is shown that cooling down the bottom electrode to the melting metal temperature leads to decrease of shear stress on the fettle area by 15 %.

  1. Efficient needle plasma actuators for flow control and surface cooling

    NASA Astrophysics Data System (ADS)

    Zhao, Pengfei; Portugal, Sherlie; Roy, Subrata

    2015-07-01

    We introduce a milliwatt class needle actuator suitable for plasma channels, vortex generation, and surface cooling. Electrode configurations tested for a channel configuration show 1400% and 300% increase in energy conversion efficiency as compared to conventional surface and channel corona actuators, respectively, generating up to 3.4 m/s air jet across the channel outlet. The positive polarity of the needle is shown to have a beneficial effect on actuator efficiency. Needle-plate configuration is demonstrated for improving cooling of a flat surface with a 57% increase in convective heat transfer coefficient. Vortex generation by selective input signal manipulation is also demonstrated.

  2. Skin cooling maintains cerebral blood flow velocity and orthostatic tolerance during tilting in heated humans

    NASA Technical Reports Server (NTRS)

    Wilson, Thad E.; Cui, Jian; Zhang, Rong; Witkowski, Sarah; Crandall, Craig G.

    2002-01-01

    Orthostatic tolerance is reduced in the heat-stressed human. The purpose of this project was to identify whether skin-surface cooling improves orthostatic tolerance. Nine subjects were exposed to 10 min of 60 degrees head-up tilting in each of four conditions: normothermia (NT-tilt), heat stress (HT-tilt), normothermia plus skin-surface cooling 1 min before and throughout tilting (NT-tilt(cool)), and heat stress plus skin-surface cooling 1 min before and throughout tilting (HT-tilt(cool)). Heating and cooling were accomplished by perfusing 46 and 15 degrees C water, respectively, though a tube-lined suit worn by each subject. During HT-tilt, four of nine subjects developed presyncopal symptoms resulting in the termination of the tilt test. In contrast, no subject experienced presyncopal symptoms during NT-tilt, NT-tilt(cool), or HT-tilt(cool). During the HT-tilt procedure, mean arterial blood pressure (MAP) and cerebral blood flow velocity (CBFV) decreased. However, during HT-tilt(cool), MAP, total peripheral resistance, and CBFV were significantly greater relative to HT-tilt (all P < 0.01). No differences were observed in calculated cerebral vascular resistance between the four conditions. These data suggest that skin-surface cooling prevents the fall in CBFV during upright tilting and improves orthostatic tolerance, presumably via maintenance of MAP. Hence, skin-surface cooling may be a potent countermeasure to protect against orthostatic intolerance observed in heat-stressed humans.

  3. A generalized one-dimensional computer code for turbomachinery cooling passage flow calculations

    NASA Technical Reports Server (NTRS)

    Kumar, Ganesh N.; Roelke, Richard J.; Meitner, Peter L.

    1989-01-01

    A generalized one-dimensional computer code for analyzing the flow and heat transfer in the turbomachinery cooling passages was developed. This code is capable of handling rotating cooling passages with turbulators, 180 degree turns, pin fins, finned passages, by-pass flows, tip cap impingement flows, and flow branching. The code is an extension of a one-dimensional code developed by P. Meitner. In the subject code, correlations for both heat transfer coefficient and pressure loss computations were developed to model each of the above mentioned type of coolant passages. The code has the capability of independently computing the friction factor and heat transfer coefficient on each side of a rectangular passage. Either the mass flow at the inlet to the channel or the exit plane pressure can be specified. For a specified inlet total temperature, inlet total pressure, and exit static pressure, the code computers the flow rates through the main branch and the subbranches, flow through tip cap for impingement cooling, in addition to computing the coolant pressure, temperature, and heat transfer coefficient distribution in each coolant flow branch. Predictions from the subject code for both nonrotating and rotating passages agree well with experimental data. The code was used to analyze the cooling passage of a research cooled radial rotor.

  4. Far-ultraviolet morphology of star-forming filaments in cool core brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Tremblay, G. R.; O'Dea, C. P.; Baum, S. A.; Mittal, R.; McDonald, M. A.; Combes, F.; Li, Y.; McNamara, B. R.; Bremer, M. N.; Clarke, T. E.; Donahue, M.; Edge, A. C.; Fabian, A. C.; Hamer, S. L.; Hogan, M. T.; Oonk, J. B. R.; Quillen, A. C.; Sanders, J. S.; Salomé, P.; Voit, G. M.

    2015-08-01

    We present a multiwavelength morphological analysis of star-forming clouds and filaments in the central (≲50 kpc) regions of 16 low-redshift (z < 0.3) cool core brightest cluster galaxies. New Hubble Space Telescope imaging of far-ultraviolet continuum emission from young (≲10 Myr), massive (≳5 M⊙) stars reveals filamentary and clumpy morphologies, which we quantify by means of structural indices. The FUV data are compared with X-ray, Lyα, narrow-band Hα, broad-band optical/IR, and radio maps, providing a high spatial resolution atlas of star formation locales relative to the ambient hot (˜107-8 K) and warm ionized (˜104 K) gas phases, as well as the old stellar population and radio-bright active galactic nucleus (AGN) outflows. Nearly half of the sample possesses kpc-scale filaments that, in projection, extend towards and around radio lobes and/or X-ray cavities. These filaments may have been uplifted by the propagating jet or buoyant X-ray bubble, or may have formed in situ by cloud collapse at the interface of a radio lobe or rapid cooling in a cavity's compressed shell. The morphological diversity of nearly the entire FUV sample is reproduced by recent hydrodynamical simulations in which the AGN powers a self-regulating rain of thermally unstable star-forming clouds that precipitate from the hot atmosphere. In this model, precipitation triggers where the cooling-to-free-fall time ratio is tcool/tff ˜ 10. This condition is roughly met at the maximal projected FUV radius for more than half of our sample, and clustering about this ratio is stronger for sources with higher star formation rates.

  5. Flow distribution analysis on the cooling tube network of ITER thermal shield

    NASA Astrophysics Data System (ADS)

    Nam, Kwanwoo; Chung, Wooho; Noh, Chang Hyun; Kang, Dong Kwon; Kang, Kyoung-O.; Ahn, Hee Jae; Lee, Hyeon Gon

    2014-01-01

    Thermal shield (TS) is to be installed between the vacuum vessel or the cryostat and the magnets in ITER tokamak to reduce the thermal radiation load to the magnets operating at 4.2K. The TS is cooled by pressurized helium gas at the inlet temperature of 80K. The cooling tube is welded on the TS panel surface and the composed flow network of the TS cooling tubes is complex. The flow rate in each panel should be matched to the thermal design value for effective radiation shielding. This paper presents one dimensional analysis on the flow distribution of cooling tube network for the ITER TS. The hydraulic cooling tube network is modeled by an electrical analogy. Only the cooling tube on the TS surface and its connecting pipe from the manifold are considered in the analysis model. Considering the frictional factor and the local loss in the cooling tube, the hydraulic resistance is expressed as a linear function with respect to mass flow rate. Sub-circuits in the TS are analyzed separately because each circuit is controlled by its own control valve independently. It is found that flow rates in some panels are insufficient compared with the design values. In order to improve the flow distribution, two kinds of design modifications are proposed. The first one is to connect the tubes of the adjacent panels. This will increase the resistance of the tube on the panel where the flow rate is excessive. The other design suggestion is that an orifice is installed at the exit of tube routing where the flow rate is to be reduced. The analysis for the design suggestions shows that the flow mal-distribution is improved significantly.

  6. Flow distribution analysis on the cooling tube network of ITER thermal shield

    SciTech Connect

    Nam, Kwanwoo; Chung, Wooho; Noh, Chang Hyun; Kang, Dong Kwon; Kang, Kyoung-O; Ahn, Hee Jae; Lee, Hyeon Gon

    2014-01-29

    Thermal shield (TS) is to be installed between the vacuum vessel or the cryostat and the magnets in ITER tokamak to reduce the thermal radiation load to the magnets operating at 4.2K. The TS is cooled by pressurized helium gas at the inlet temperature of 80K. The cooling tube is welded on the TS panel surface and the composed flow network of the TS cooling tubes is complex. The flow rate in each panel should be matched to the thermal design value for effective radiation shielding. This paper presents one dimensional analysis on the flow distribution of cooling tube network for the ITER TS. The hydraulic cooling tube network is modeled by an electrical analogy. Only the cooling tube on the TS surface and its connecting pipe from the manifold are considered in the analysis model. Considering the frictional factor and the local loss in the cooling tube, the hydraulic resistance is expressed as a linear function with respect to mass flow rate. Sub-circuits in the TS are analyzed separately because each circuit is controlled by its own control valve independently. It is found that flow rates in some panels are insufficient compared with the design values. In order to improve the flow distribution, two kinds of design modifications are proposed. The first one is to connect the tubes of the adjacent panels. This will increase the resistance of the tube on the panel where the flow rate is excessive. The other design suggestion is that an orifice is installed at the exit of tube routing where the flow rate is to be reduced. The analysis for the design suggestions shows that the flow mal-distribution is improved significantly.

  7. Flow Integrating Section for a Gas Turbine Engine in Which Turbine Blades are Cooled by Full Compressor Flow

    SciTech Connect

    Steward, W. Gene

    1999-11-14

    Routing of full compressor flow through hollow turbine blades achieves unusually effective blade cooling and allows a significant increase in turbine inlet gas temperature and, hence, engine efficiency. The invention, ''flow integrating section'' alleviates the turbine dissipation of kinetic energy of air jets leaving the hollow blades as they enter the compressor diffuser.

  8. Evaluation of water cooled supersonic temperature and pressure probes for application to 1366 K flows

    NASA Technical Reports Server (NTRS)

    Lagen, Nicholas; Seiner, John M.

    1990-01-01

    Water cooled supersonic probes are developed to investigate total pressure, static pressure, and total temperature in high-temperature jet plumes and thereby determine the mean flow properties. Two probe concepts, designed for operation at up to 1366 K in a Mach 2 flow, are tested on a water cooled nozzle. The two probe designs - the unsymmetric four-tube cooling configuration and the symmetric annular cooling design - take measurements at 755, 1089, and 1366 K of the three parameters. The cooled total and static pressure readings are found to agree with previous test results with uncooled configurations. The total-temperature probe, however, is affected by the introduction of water coolant, and effect which is explained by the increased heat transfer across the thermocouple-bead surface. Further investigation of the effect of coolant on the temperature probe is proposed to mitigate the effect and calculate more accurate temperatures in jet plumes.

  9. Concept of CFD model of natural draft wet-cooling tower flow

    NASA Astrophysics Data System (ADS)

    Hyhlík, T.

    2014-03-01

    The article deals with the development of CFD model of natural draft wet-cooling tower flow. The physical phenomena taking place within a natural draft wet cooling tower are described by the system of conservation law equations along with additional equations. The heat and mass transfer in the counterflow wet-cooling tower fill are described by model [1] which is based on the system of ordinary differential equations. Utilization of model [1] of the fill allows us to apply commonly measured fill characteristics as shown by [2].The boundary value problem resulting from the fill model is solved separately. The system of conservation law equations is interlinked with the system of ordinary differential equations describing the phenomena occurring in the counterflow wet-cooling tower fill via heat and mass sources and via boundary conditions. The concept of numerical solution is presented for the quasi one dimensional model of natural draft wet-cooling tower flow. The simulation results are shown.

  10. Thermal modeling in an engine cooling system to control coolant flow for fuel consumption improvement

    NASA Astrophysics Data System (ADS)

    Park, Sangki; Woo, Seungchul; Kim, Minho; Lee, Kihyung

    2016-09-01

    The design and evaluation of engine cooling and lubrication systems is generally based on real vehicle tests. Our goal here was to establish an engine heat balance model based on mathematical and interpretive analysis of each element of a passenger diesel engine cooling system using a 1-D numerical model. The purpose of this model is to determine ways of optimizing the cooling and lubrication components of an engine and then to apply these methods to actual cooling and lubrication systems of engines that will be developed in the future. Our model was operated under the New European Driving Cycle (NEDC) mode conditions, which represent the fuel economy evaluation mode in Europe. The flow rate of the cooling system was controlled using a control valve. Our results showed that the fuel efficiency was improved by as much as 1.23 %, cooling loss by 1.35 %, and friction loss by 2.21 % throughout NEDC modes by modification of control conditions.

  11. Experimental study on corrugated cross-flow air-cooled plate heat exchangers

    SciTech Connect

    Kim, Minsung; Baik, Young-Jin; Park, Seong-Ryong; Ra, Ho-Sang; Lim, Hyug

    2010-11-15

    Experimental study on cross-flow air-cooled plate heat exchangers (PHEs) was performed. The two prototype PHEs were manufactured in a stack of single-wave plates and double-wave plates in parallel. Cooling air flows through the PHEs in a crosswise direction against internal cooling water. The heat exchanger aims to substitute open-loop cooling towers with closed-loop water circulation, which guarantees cleanliness and compactness. In this study, the prototype PHEs were tested in a laboratory scale experiments. From the tests, double-wave PHE shows approximately 50% enhanced heat transfer performance compared to single-wave PHE. However, double-wave PHE costs 30% additional pressure drop. For commercialization, a wide channel design for air flow would be essential for reliable performance. (author)

  12. X-ray cavities and temperature jumps in the environment of the strong cool core cluster Abell 2390

    NASA Astrophysics Data System (ADS)

    Sonkamble, S. S.; Vagshette, N. D.; Pawar, P. K.; Patil, M. K.

    2015-10-01

    We present results based on the systematic analysis of high resolution 95 ks Chandra observations of the strong cool core cluster Abell 2390 at the redshift of z = 0.228 that hosts an energetic radio AGN. This analysis has enabled us to investigate five X-ray deficient cavities in the atmosphere of Abell 2390 within central 30''. Presence of these cavities have been confirmed through a variety of image processing techniques like, the surface brightness profiles, unsharp masked image, as well as 2D elliptical model subtracted residual map. Temperature profile as well as 2D temperature map revealed structures in the distribution of ICM, in the sense that ICM in the NW direction is cooler than that on the SE direction. Temperature jump in all directions is evident near 25'' (90.5 kpc) corresponding to the average Mach number 1.44± 0.05, while another jump from 7.47 keV to 9.10 keV at 68'' (246 kpc) in the north-west direction, corresponding to Mach number 1.22± 0.06 and these jumps are associated with the cold fronts. Tricolour map as well as hardness ratio map detects cool gas clumps in the central 30 kpc region of temperature 4.45_{-0.10}^{+0.16} keV. The entropy profile derived from the X-ray analysis is found to fall systematically inward in a power-law fashion and exhibits a floor near 12.20± 2.54 keV cm2 in the central region. This flattening of the entropy profile in the core region confirms the intermittent heating at the centre by AGN. The diffuse radio emission map at 1.4 GHz using VLA L-band data exhibits highly asymmetric morphology with an edge in the north-west direction coinciding with the X-ray edge seen in the unsharp mask image. The mechanical power injected by the AGN in the form of X-ray cavities is found to be 5.94× 10^{45} erg s^{-1} and is roughly an order of magnitude higher than the energy lost by the ICM in the form of X-ray emission, confirming that AGN feedback is capable enough to quench the cooling flow in this cluster.

  13. THE EFFECT OF ENVIRONMENT ON THE FORMATION OF H{alpha} FILAMENTS AND COOL CORES IN GALAXY GROUPS AND CLUSTERS

    SciTech Connect

    McDonald, Michael; Veilleux, Sylvain; Mushotzky, Richard E-mail: veilleux@astro.umd.edu

    2011-04-10

    We present the results of a combined X-ray and H{alpha} study of 10 galaxy groups and 17 galaxy clusters using the Chandra X-ray Observatory and the Maryland Magellan Tunable Filter. We find no difference in the morphology or detection frequency of H{alpha} filaments in groups versus clusters over the mass range 10{sup 13} < M{sub 500} < 10{sup 15} M{sub sun}. The detection frequency of H{alpha} emission is shown to be only weakly dependent on the total mass of the system at the 52% confidence level. In contrast, we find that the presence of H{alpha} filaments is strongly correlated with both the global (89% confidence level) and core (84%) intracluster medium (ICM) entropy, as well as the X-ray cooling rate (72%). The H{alpha} filaments are therefore an excellent proxy for the cooling ICM. The H{alpha} filaments are more strongly correlated with the cooling properties of the ICM than with the radio properties of the brightest cluster galaxy; this further supports the scenario where these filaments are directly associated with a thermally unstable, rapidly cooling ICM, rather than radio bubbles. The ICM cooling efficiency, defined as the X-ray cooling rate per unit gas mass, is shown to correlate with the total system mass, indicating that groups are more efficient at cooling than clusters. This result implies that, in systems with cool cores, active galactic nucleus feedback scales with the total mass of the system, in agreement with earlier suggestions.

  14. Central mass profiles of the nearby cool-core galaxy clusters Hydra A and A478

    NASA Astrophysics Data System (ADS)

    Okabe, N.; Umetsu, K.; Tamura, T.; Fujita, Y.; Takizawa, M.; Matsushita, K.; Fukazawa, Y.; Futamase, T.; Kawaharada, M.; Miyazaki, S.; Mochizuki, Y.; Nakazawa, K.; Ohashi, T.; Ota, N.; Sasaki, T.; Sato, K.; Tam, S. I.

    2016-03-01

    We perform a weak-lensing study of the nearby cool-core galaxy clusters, Hydra A (z = 0.0538) and A478 (z = 0.0881), of which the brightest cluster galaxies (BCGs) host the powerful activities of active galactic nuclei (AGNs). For each cluster, the observed tangential shear profile is described well by either a single Navarro-Frenk-White model or a two-component model including the BCG as an unresolved point mass. For A478, we determine the BCG and its host-halo masses from a joint fit to weak-lensing and stellar photometry measurements. We find that the choice of initial mass functions (IMFs) can introduce a factor of 2 uncertainty in the BCG mass, whereas the BCG host-halo mass is constrained well by data. We perform a joint analysis of the weak-lensing and stellar kinematics data available for the Hydra A cluster, which allows us to constrain the central mass profile without assuming specific IMFs. We find that the central mass profile (r < 300 kpc) determined from the joint analysis is in excellent agreement with those from independent measurements, including dynamical masses estimated from the cold gas disc component, X-ray hydrostatic total mass estimates, and the central stellar mass estimated with the Salpeter IMF. The observed dark matter fraction around the BCG for Hydra A is found to be smaller than those predicted by adiabatic contraction models, suggesting the importance of other physical processes, such as AGN feedback and/or dissipationless mergers.

  15. Infrared Cavity Ringdown Laser Absorption Spectroscopy of jet-cooled clusters

    NASA Astrophysics Data System (ADS)

    Provencal, Robert Allen

    Infrared Cavity Ringdown Laser Absorption Spectroscopy (IR-CRLAS) employing stimulated Raman scattering (SRS) of pulsed dye lasers as the tunable IR source has been developed. This technique allows highly sensitive (ca. 1 ppm fractional absorption) direct absorption measurements to be performed in the 2-8 μm spectral range with complete wavelength coverage. Basic CR-LAS principles and essential SRS theory are reviewed. IR- CRLAS spectrometers based on both a Raman shifted dye laser and a pulsed Alexandrite ring laser are described. The IR-CRLAS spectrometer has been used in a comparative study of the O-H-stretching vibrations of small alcohol clusters. Results indicate an increase in the hydrogen bond strength as the alcohol chain length increases. An IR-CRLAS investigation of the aromatic C-H stretches of benzene and berizene/methane mixtures, performed in an effort to provide experimental support for a theoretically proposed ``antihydrogen bond'', produced negative results. Similarly, negative results from a visible CRLAS search for water cluster absorptions in connection with the anomalous atmospheric absorption of solar radiation are presented. Infrared laser spectroscopic studies of the structures and bonding in jet-cooled carbon clusters are discussed. The measurement and analysis of a rovibrational band at 2074 cm-1, tentatively assigned to linear C10 is presented. The astrophysical significance of carbon clusters is also discussed in conjunction with the first detection of a non polar molecule (C3) in a cold interstellar dust forming region, performed using far-infrared heterodyne spectroscopy aboard the Kuiper Airborne Observatory.

  16. A spin-down clock for cool stars from observations of a 2.5-billion-year-old cluster.

    PubMed

    Meibom, Søren; Barnes, Sydney A; Platais, Imants; Gilliland, Ronald L; Latham, David W; Mathieu, Robert D

    2015-01-29

    The ages of the most common stars--low-mass (cool) stars like the Sun, and smaller--are difficult to derive because traditional dating methods use stellar properties that either change little as the stars age or are hard to measure. The rotation rates of all cool stars decrease substantially with time as the stars steadily lose their angular momenta. If properly calibrated, rotation therefore can act as a reliable determinant of their ages based on the method of gyrochronology. To calibrate gyrochronology, the relationship between rotation period and age must be determined for cool stars of different masses, which is best accomplished with rotation period measurements for stars in clusters with well-known ages. Hitherto, such measurements have been possible only in clusters with ages of less than about one billion years, and gyrochronology ages for older stars have been inferred from model predictions. Here we report rotation period measurements for 30 cool stars in the 2.5-billion-year-old cluster NGC 6819. The periods reveal a well-defined relationship between rotation period and stellar mass at the cluster age, suggesting that ages with a precision of order 10 per cent can be derived for large numbers of cool Galactic field stars.

  17. A method for measuring cooling air flow in base coolant passages of rotating turbine blades

    NASA Technical Reports Server (NTRS)

    Liebert, C. H.; Pollack, F. G.

    1975-01-01

    Method accurately determines actual coolant mass flow rate in cooling passages of rotating turbine blades. Total and static pressures are measured in blade base coolant passages. Mass flow rates are calculated from these measurements of pressure, measured temperature and known area.

  18. Numerical Modeling of Surface and Volumetric Cooling using Optimal T- and Y-shaped Flow Channels

    NASA Astrophysics Data System (ADS)

    Kosaraju, Srinivas

    2015-11-01

    The T- and Y-shaped flow channels can be optimized for reduced pressure drop and pumping power. The results of the optimization are in the form of geometric parameters such as length and diameter ratios of the stem and branch sections. While these flow channels are optimized for minimum pressure drop, they can also be used for surface and volumetric cooling applications such as heat exchangers, air conditioning and electronics cooling. In this paper, we studied the heat transfer characteristics of multiple T- and Y-shaped flow channel configurations using numerical simulations. All configurations are subjected to same pumping power and heat generation constraints and their heat transfer performance is studied.

  19. Water cooling system using a piezoelectrically actuated flow pump for a medical headlight system

    NASA Astrophysics Data System (ADS)

    Pires, Rogério F.; Vatanabe, Sandro L.; de Oliveira, Amaury R.; Nakasone, Paulo H.; Silva, Emílio C.

    2007-04-01

    The microchips inside modern electronic equipment generate heat and demand, each day, the use of more advanced cooling techniques as water cooling systems, for instance. These systems combined with piezoelectric flow pumps present some advantages such as higher thermal capacity, lower noise generation and miniaturization potential. The present work aims at the development of a water cooling system based on a piezoelectric flow pump for a head light system based on LEDs. The cooling system development consists in design, manufacturing and experimental characterization steps. In the design step, computational models of the pump, as well as the heat exchanger were built to perform sensitivity studies using ANSYS finite element software. This allowed us to achieve desired flow and heat exchange rates by varying the frequency and amplitude of the applied voltage. Other activities included the design of the heat exchanger and the dissipation module. The experimental tests of the cooling system consisted in measuring the temperature difference between the heat exchanger inlet and outlet to evaluate its thermal cooling capacity for different values of the flow rate. Comparisons between numerical and experimental results were also made.

  20. Modeling and simulation of mixing layer flows for rocket engine film cooling

    NASA Astrophysics Data System (ADS)

    Dellimore, Kiran Hamilton Jeffrey

    Film cooling has been selected for the thermal protection of the composite nozzle extension of the J-2X engine which is currently being developed for the second stage of NASA's next generation launch vehicle, the Ares I rocket. However, several challenges remain in order to achieve effective film cooling of the nozzle extension and to ensure its safe operation. The extreme complexity of the flow (three-dimensional wakes, lateral flows, vorticity, and flow separation) makes predicting film cooling performance difficult. There is also a dearth of useful supersonic film cooling data available for engineers to use in engine design and a lack of maturity of CFD tools to quantitatively match supersonic film cooling data. This dissertation advances the state of the art in film cooling by presenting semi-empirical analytical models which improve the basic physical understanding and prediction of the effects of pressure gradients, compressibility and density gradients on film cooling effectiveness. These models are shown to correlate most experimental data well and to resolve several conflicts in the open literature. The core-to-coolant stream velocity ratio, R, and the Kays acceleration parameter, KP, are identified as the critical parameters needed to understand how pressure gradients influence film cooling performance. The convective Mach number, MC, the total temperature ratio, theta0, and the Mach number of the high speed stream, MHS, are shown to be important when explaining the effects of compressibility and density gradient on film cooling effectiveness. An advance in the simulation of film cooling flows is also presented through the development of a computationally inexpensive RANS methodology capable of correctly predicting film cooling performance under turbulent, subsonic conditions. The subsonic simulation results suggest that it in order to obtain accurate predictions using RANS it is essential to thoroughly characterize the turbulent states at the inlet of

  1. Numerical and experimental investigation of a counter flow cooling system for the blown film extrusion

    NASA Astrophysics Data System (ADS)

    Janas, M.; Fehlberg, L.; Wortberg, J.

    2014-05-01

    Conventional cooling systems for the blown film extrusion govern the cooling airflow only in one direction. In contrast, a counter flow system uses two individual jet flows. One jet flow provides the air in draw up direction like used in conventional systems. The other one guides the airflow towards the die. It is possible to cool the film over a longer film surface intensively. In addition, the interaction of the jet flow and the ambient air can be reduced which is responsible for an unsteady heat transfer. In this paper, such a cooling system is investigated in detail, numerically as well as experimentally. The experimental work is done using a modular system for a laboratory blown film line. For the simulation, a process model is used which is able to compute a realistic blown film behavior depending on the actual cooling condition. Therefore, a CFD-analysis computes the temperature of the film and flow phenomena of the jets. A contour calculation model is used to predict the bubble shape. It is based on the framework from Pearson and Petrie and a modified Phan-Thien Tanner model for the rheological description of the tube formation zone. Both modules interact in a loop until a final quasi-stationary blown film contour is found. The aim of this investigation is to get a better understanding of the film cooling using a counter flow system for several different process states. In addition, this knowledge base can help to develop novel cooling approaches. Therefore, a process space is analyzed using a LDPE. To verify the simulation with the experimental results the film contour and frost line are measured.

  2. Emergency makeup flow model for the K-reactor cooling water basin

    SciTech Connect

    Barbour, K.L.

    1994-12-31

    The Savannah River site installed the K-reactor cooling tower in 1993 to replace river water supplied to a 25-million-gal cooling basin with cooling tower recirculation. The reactor accident safety analysis assumes that cooling water recirculation is lost during the accident and basin level will drop. Emergency river water supply makeup valves will be opened manually to restore basin makeup and level and maintain shutdown safety. A hydraulic model scopes out valve flow response as the valves are opened. Scoping objectives are (a) valve flow rate response, (b) volumetric makeup with time, and (c) total volumetric makeup effect on basin emergency operating operating procedures. Model results could influence basin emergency operating procedures development before actual field test data are obtained.

  3. Computation of Turbulent Recirculating Flow in Channels, and for Impingement Cooling

    NASA Technical Reports Server (NTRS)

    Chang, Byong Hoon

    1992-01-01

    Fully elliptic forms of the transport equations have been solved numerically for two flow configurations. The first is turbulent flow in a channel with transverse rectangular ribs, and the second is impingement cooling of a plane surface. Both flows are relevant to proposed designs for active cooling of hypersonic vehicles using supercritical hydrogen as the coolant. Flow downstream of an abrupt pipe expansion and of a backward-facing step were also solved with various near-wall turbulence models as benchmark problems. A simple form of periodicity boundary condition was used for the channel flow with transverse rectangular ribs. The effects of various parameters on heat transfer in channel flow with transverse ribs and in impingement cooling were investigated using the Yap modified Jones and Launder low Reynolds number k-epsilon turbulence model. For the channel flow, predictions were in adequate agreement with experiment for constant property flow, with the results for friction superior to those for heat transfer. For impingement cooling, the agreement with experiment was generally good, but the results suggest that improved modelling of the dissipation rate of turbulence kinetic energy is required in order to obtain improved heat transfer prediction, especially near the stagnation point. The k-epsilon turbulence model was used to predict the mean flow and heat transfer for constant and variable property flows. The effect of variable properties for channel flow was investigated using the same turbulence model, but comparison with experiment yielded no clear conclusions. Also, the wall function method was modified for use in the variable properties flow with a non-adiabatic surface, and an empirical model is suggested to correctly account for the behavior of the viscous sublayer with heating.

  4. Computation of turbulent recirculating flow in channels, and for impingement cooling

    SciTech Connect

    Chang, B.H.

    1992-01-01

    Fully elliptic forms of the transport equations have been solved numerically for two flow configurations. The first is turbulent flow in a channel with transverse rectangular ribs, and the second is impingement cooling of a plane surface. Both flows are relevant to proposed designs for active cooling of hypersonic vehicles using supercritical hydrogen as the coolant. Flow downstream of an abrupt pipe expansion and of a backward-facing step were also solved with various near-wall turbulence models as benchmark problems. A simple form of periodicity boundary condition was used for the channel flow with transverse rectangular ribs. The effects of various parameters on heat transfer in channel flow with transverse ribs and in impingement cooling were investigated using the Yap modified Jones and Launder low Reynolds number k-[epsilon] turbulence model. For the channel flow, predictions were in adequate agreement with experiment for constant property flow, with the results for friction superior to those for heat transfer. For impingement cooling, the agreement with experiment was generally good, but the results suggest that improvement modelling of the dissipation rate of turbulence kinetic energy is required in order to obtain improved heat transfer prediction, especially near the stagnation point. The k-[epsilon] turbulence model was used to predict the mean flow and heat transfer for constant and variable property flows. The effect of variable properties for channel flow was investigated using the same turbulence model, but comparison with experiment yielded no clear conclusions. Also, the wall function method was modified for use in the variable properties flow with a non-adiabatic surface, and an empirical model is suggested to correctly account for the behavior of the viscous sublayer with heating. The wall thermal boundary condition was found to have a significant effect on local heat transfer coefficients in the neighborhood of boundary layer separation.

  5. A simple counter-flow cooling system for a supersonic free-jet beam source assembly.

    PubMed

    Barr, M; Fahy, A; Martens, J; Dastoor, P C

    2016-05-01

    A simple design for an inexpensive, cooled, free-jet beam source is described. The source assembly features an integrated cooling system as supplied by a counter-flow of chilled nitrogen, and is composed primarily of off-the-shelf tube fittings. The design facilitates rapid implementation and eases subsequent alignment with respect to any downstream beamline aperture. The source assembly outlined cools the full length of the stagnation volume, offering temperature control down to 100 K and long-term temperature stability better than ±1 K. PMID:27250408

  6. A simple counter-flow cooling system for a supersonic free-jet beam source assembly

    NASA Astrophysics Data System (ADS)

    Barr, M.; Fahy, A.; Martens, J.; Dastoor, P. C.

    2016-05-01

    A simple design for an inexpensive, cooled, free-jet beam source is described. The source assembly features an integrated cooling system as supplied by a counter-flow of chilled nitrogen, and is composed primarily of off-the-shelf tube fittings. The design facilitates rapid implementation and eases subsequent alignment with respect to any downstream beamline aperture. The source assembly outlined cools the full length of the stagnation volume, offering temperature control down to 100 K and long-term temperature stability better than ±1 K.

  7. Options for Cryogenic Load Cooling with Forced Flow Helium Circulation

    SciTech Connect

    Peter Knudsen, Venkatarao Ganni, Roberto Than

    2012-06-01

    Cryogenic pumps designed to circulate super-critical helium are commonly deemed necessary in many super-conducting magnet and other cooling applications. Acknowledging that these pumps are often located at the coldest temperature levels, their use introduces risks associated with the reliability of additional rotating machinery and an additional load on the refrigeration system. However, as it has been successfully demonstrated, this objective can be accomplished without using these pumps by the refrigeration system, resulting in lower system input power and improved reliability to the overall cryogenic system operations. In this paper we examine some trade-offs between using these pumps vs. using the refrigeration system directly with examples of processes that have used these concepts successfully and eliminated using such pumps

  8. Effect of endwall cooling on secondary flows in turbine stator vanes

    NASA Technical Reports Server (NTRS)

    Goldman, L. J.; Mclallin, K. L.

    1977-01-01

    The effect of endwall cooling on the secondary flow behavior and the aerodynamic performance of a core turbine stator vane was determined. The investigation was conducted in a cold-air, full-annular cascade, where three-dimensional effects were obtained. Two endwall cooling configurations were tested. In the first configuration, the cooling holes were oriented so that the coolant was injected in line with the inviscid streamline direction. In the second configuration, the coolant was injected at an angle of 15 deg to the inviscid streamline direction and oriented towards the vane pressure stator. In both cases the stator vanes were solid and uncooled so that the effect of endwall cooling was obtained directly. Total-pressure surveys were taken downstream of the stator vanes over a range of cooling flows at the design, mean-radius, critical velocity ratio of 0.778. Changes in the total-pressure contours downstream of the vanes were used to obtain the effect of endwall cooling on the secondary flows in the stator.

  9. Cooling rate of an active Hawaiian lava flow from nighttime spectroradiometer measurements

    NASA Astrophysics Data System (ADS)

    Flynn, Luke P.; Mouginis-Mark, Peter J.

    1992-09-01

    A narrow-band spectroradiometer has been used to make nighttime measurements of the Phase 50 eruption of Pu'u O'o, on the East Rift Zone of Kilauea Volcano, Hawaii. On February 19, 1992, a GER spectroradiometer was used to determine the cooling rate of an active lava flow. This instrument collects 12-bit data between 0.35 to 3.0 microns at a spectral resolution of 1-5 nm. Thirteen spectra of a single area on a pahoehoe flow field were collected over a 59 minute period (21:27-22:26 HST) from which the cooling of the lava surface has been investigated. A two-component thermal mixing model (Flynn, 1992) applied to data for the flow immediately on emplacement gave a best-fit crustal temperature of 768 C, a hot component at 1150 C, and a hot radiating area of 3.6 percent of the total area. Over a 52-minute period (within the time interval between flow resurfacings) the lava flow crust cooled by 358 to 410 C at a rate that was as high as 15 C/min. The observations have significance both for satellite observations of active volcanoes and for numerical models of the cooling of lava flows during their emplacement.

  10. Cooling rate of an active Hawaiian lava flow from nighttime spectroradiometer measurements

    NASA Technical Reports Server (NTRS)

    Flynn, Luke P.; Mouginis-Mark, Peter J.

    1992-01-01

    A narrow-band spectroradiometer has been used to make nighttime measurements of the Phase 50 eruption of Pu'u O'o, on the East Rift Zone of Kilauea Volcano, Hawaii. On February 19, 1992, a GER spectroradiometer was used to determine the cooling rate of an active lava flow. This instrument collects 12-bit data between 0.35 to 3.0 microns at a spectral resolution of 1-5 nm. Thirteen spectra of a single area on a pahoehoe flow field were collected over a 59 minute period (21:27-22:26 HST) from which the cooling of the lava surface has been investigated. A two-component thermal mixing model (Flynn, 1992) applied to data for the flow immediately on emplacement gave a best-fit crustal temperature of 768 C, a hot component at 1150 C, and a hot radiating area of 3.6 percent of the total area. Over a 52-minute period (within the time interval between flow resurfacings) the lava flow crust cooled by 358 to 410 C at a rate that was as high as 15 C/min. The observations have significance both for satellite observations of active volcanoes and for numerical models of the cooling of lava flows during their emplacement.

  11. Flow tube used to cool solar-pumped laser

    NASA Technical Reports Server (NTRS)

    1968-01-01

    A flow tube has been designed and constructed to provide two major functions in the application of a laser beam for transmission of both sound and video. It maintains the YAG laser at the proper operating temperature of 300 degrees K under solar pumping conditions, and it serves as a pump cavity for the laser crystal.

  12. Testing the cooling flow model in the intermediate polar EX Hydrae

    NASA Astrophysics Data System (ADS)

    Luna, G. J. M.; Raymond, J. C.; Brickhouse, N. S.; Mauche, C. W.; Suleimanov, V.

    2015-06-01

    We use the best available X-ray data from the intermediate polar EX Hydrae to study the cooling-flow model often applied to interpret the X-ray spectra of these accreting magnetic white dwarf binaries. First, we resolve a long-standing discrepancy between the X-ray and optical determinations of the mass of the white dwarf in EX Hya by applying new models of the inner disk truncation radius. Our fits to the X-ray spectrum now agree with the white dwarf mass of 0.79 M⊙ determined using dynamical methods through spectroscopic observations of the secondary. We use a simple isobaric cooling flow model to derive the emission line fluxes, emission measure distribution, and H-like to He-like line ratios for comparison with the 496 ks Chandra High Energy Transmission Grating observation of EX Hydrae. We find that the H/He ratios are not well reproduced by this simple isobaric cooling flow model and show that while H-like line fluxes can be accurately predicted, fluxes of lower-Z He-like lines are significantly underestimated. This discrepancy suggests that an extra heating mechanism plays an important role at the base of the accretion column, where cooler ions form. We thus explored more complex cooling models, including the change of gravitational potential with height in the accretion column and a magnetic dipole geometry. None of these modifications to the standard cooling flow model are able to reproduce the observed line ratios. While a cooling flow model with subsolar (0.1 ⊙) abundances is able to reproduce the line ratios by reducing the cooling rate at temperatures lower than ~107.3 K, the predicted line-to-continuum ratios are much lower than observed. We discuss and discard mechanisms, such as photoionization, departures from constant pressure, resonant scattering, different electron-ion temperatures, and Compton cooling. Thermal conduction transfers energy from the region above 107 K, where the H-like lines are mostly formed, to the cooler regions where the

  13. Counter flow cooling drier with integrated heat recovery

    DOEpatents

    Shivvers, Steve D.

    2009-08-18

    A drier apparatus for removing water or other liquids from various materials includes a mixer, drying chamber, separator and regenerator and a method for use of the apparatus. The material to be dried is mixed with a heated media to form a mixture which then passes through the chamber. While passing through the chamber, a comparatively cool fluid is passed counter current through the mixture so that the mixture becomes cooler and drier and the fluid becomes hotter and more saturated with moisture. The mixture is then separated into drier material and media. The media is transferred to the regenerator and heated therein by the hot fluid from the chamber and supplemental heat is supplied to bring the media to a preselected temperature for mixing with the incoming material to be dried. In a closed loop embodiment of the apparatus, the fluid is also recycled from the regenerator to the chamber and a chiller is utilized to reduce the temperature of the fluid to a preselected temperature and dew point temperature.

  14. Film-cooling effectiveness with developing coolant flow through straight and curved tubular passages

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Wang, C. R.; Graham, R. W.

    1982-01-01

    The data were obtained with an apparatus designed to determine the influence of tubular coolant passage curvature on film-cooling performance while simulating the developing flow entrance conditions more representative of cooled turbine blade. Data comparisons were made between straight and curved single tubular passages embedded in the wall and discharging at 30 deg angle in line with the tunnel flow. The results showed an influence of curvature on film-cooling effectiveness that was inversely proportional to the blowing rate. At the lowest blowing rate of 0.18, curvature increased the effectiveness of film cooling by 35 percent; but at a blowing rate of 0.76, the improvement was only 10 percent. In addition, the increase in film-cooling area coverage ranged from 100 percent down to 25 percent over the same blowing rates. A data trend reversal at a blowing rate of 1.5 showed the straight tubular passage's film-cooling effectiveness to be 20 percent greater than that of the curved passage with about 80 percent more area coverage. An analysis of turbulence intensity detain the mixing layer in terms of the position of the mixing interface relative to the wall supported the concept that passage curvature tends to reduce the diffusion of the coolant jet into the main stream at blowing rates below about. Explanations for the film-cooling performance of both test sections were made in terms differences in turbulences structure and in secondary flow patterns within the coolant jets as influenced by flow passage geometry.

  15. The cool-core bias in X-ray galaxy cluster samples. I. Method and application to HIFLUGCS

    NASA Astrophysics Data System (ADS)

    Eckert, D.; Molendi, S.; Paltani, S.

    2011-02-01

    Aims: When selecting flux-limited cluster samples, the detection efficiency of X-ray instruments is not the same for centrally-peaked and flat objects, which introduces a bias in flux-limited cluster samples. We quantify this effect in the case of a well-known cluster sample, HIFLUGCS. Methods: We simulate a population of X-ray clusters with various surface-brightness profiles, and use the instrumental characteristics of the ROSAT All-Sky Survey (RASS) to select flux-limited samples similar to the HIFLUGCS sample and predict the expected bias. For comparison, we also estimate observationally the bias in the HIFLUGCS sample using XMM-Newton and ROSAT data. Results: We find that the selection of X-ray cluster samples is significantly biased (~29%) in favor of the peaked, cool-core (CC) objects, with respect to non-cool-core (NCC) systems. Interestingly, we find that the bias affects the low-mass, nearby objects (groups, poor clusters) much more than the more luminous objects (i.e massive clusters). We also note a moderate increase of the bias for the more distant systems. Conclusions: Observationally, we propose to select the objects according to their flux in a well-defined physical range excluding the cores, 0.2r500-r500, to get rid of the bias. From the fluxes in this range, we reject 13 clusters out of the 64 in the HIFLUGCS sample, none of which appears to be NCC. As a result, we estimate that less than half (35-37%) of the galaxy clusters in the local Universe are strong CC. In the paradigm where the CC objects trace relaxed clusters as opposed to unrelaxed, merging objects, this implies that to the present day the majority of the objects are not in a relaxed state. From this result, we estimate a rate of heating events of ~1/3 Gyr-1 per dark-matter halo.

  16. Kilauea 1991-2002: Insights into the Cooling, Crystallization, and Hardening of Pahoehoe Lava Flows

    NASA Astrophysics Data System (ADS)

    Keszthelyi, L.; Harris, A.; Sharma, K.

    2002-12-01

    The since 1986 (with the beginning of episode 48) activity at Kilauea has been dominated by pahoehoe lavas. The nearly continuous presence of active pahoehoe lava flows in the past decade has allowed for repeated field experiments to refine models for different aspects of the emplacement of pahoehoe lava flows. For example, in 1995 a simple field experiment was conducted to verify theoretical predictions for the cooling at the base of pahoehoe lava flows. The thermocouple temperatures from the base of pahoehoe lobes showed an unexpected increase in temperature a few minutes after the lobe was extruded. The proposed explanation was that the dynamics of crystallization led to a rapid release of latent after a few tens of degrees of super-cooling had developed. Field experiments in 1999 were conducted in which pahoehoe lobes were quenched at various points in their early cooling history, allowing the temporal progression of crystallization to be directly observed. The conclusions of this experiment will be presented. Another example is the comparison of different heat loss mechanisms determined by tuning a numerical model to match 1991-1995 radiometer and thermocouple data for the cooling of the top of pahoehoe lava flows. The results indicated that cooling by the wind was the dominant heat loss term, over the life of a pahoehoe lava flow. However, this term was extremely poorly constrained, requiring a new set of field measurements. While attempts to collect these field data started in 1995, the complexity of quantifying the turbulent airflow over active lava defeated us until 2002. The results from this series of field experiments will be presented. Theoretical and field studies of the rheology of pahoehoe flows have also been conducted. It had been suggested that a visco-elastic layer, close to the solidus temperature, controlled much of the behavior of pahoehoe lava flows. Field measurements from 1991 and 2002 on the rheological properties of the initial skin to

  17. Surface chemistry associated with the cooling and subaerial weathering of recent basalt flows

    USGS Publications Warehouse

    White, A.F.; Hochella, M.F.

    1992-01-01

    The surface chemistry of fresh and weathered historical basalt flows was characterized using surface-sensitive X-ray photoelectron spectroscopy (XPS). Surfaces of unweathered 1987-1990 flows from the Kilauea Volcano, Hawaii, exhibited variable enrichment in Al, Mg, Ca, and F due to the formation of refractory fluoride compounds and pronounced depletion in Si and Fe from the volatilization of SiF4 and FeF3 during cooling. These reactions, as predicted from shifts in thermodynamic equilibrium with temperature, are induced by diffusion of HF from the flow interiors to the cooling surface. The lack of Si loss and solid fluoride formation for recent basalts from the Krafla Volcano, Iceland, suggest HF degassing at higher temperatures. Subsequent short-term subaerial weathering reactions are strongly influenced by the initial surface composition of the flow and therefore its cooling history. Successive samples collected from the 1987 Kilauea flow demonstrated that the fluoridated flow surfaces leached to a predominantly SiO2 composition by natural weathering within one year. These chemically depleted surfaces were also observed on Hawaiian basalt flows dating back to 1801 AD. Solubility and kinetic models, based on thermodynamic and kinetic data for crystalline AlF3, MgF2, and CaF2, support observed elemental depletion rates due to chemical weathering. Additional loss of alkalis from the Hawaiian basalt occurs from incongruent dissolution of the basalt glass substrate during weathering. ?? 1992.

  18. Investigation of flow characteristics effects on heat transfer in water-cooled cylinder heads

    NASA Astrophysics Data System (ADS)

    Hassan, M. A. M.; Abd El-Hameed, H. M.; Mahmoud, Osama E.

    2016-08-01

    An experimental and theoretical study has been performed to investigate the effect of flow characteristics on heat-transfer in water impingement-cooled cylinder heads. Numerous investigations have been made using a three-dimensional model, which is designed and solved by FLUENT software using both realizable k-ɛ turbulent and heat transfer models. The simulation investigates a fully developed turbulent-water flow in asymmetric heated circular passage cooled by parallel flow or impingement of circular submerged confined liquid jet. The following parameters were investigated for both parallel flow and jet impingement flow: flow velocities (1, 2 and 3 m/s), bulk fluid temperatures (50, 70 and 90 °C), main duct diameters (6, 8, 10 and 12 mm). While the following parameters were investigated for jet impingement flow, jet diameter ratio (0.6, 0.8 and 1) and jet inclination angles as measured from horizontal (45°, 60° and 90°). Experimental results were used to verify the theoretical model. Results indicate that, the normal jet (90°) gives the maximum cooling effect in comparison to other angles while the maximum heat transfer coefficient is found at jet interface position.

  19. Experimental studies of transpiration cooling with shock interaction in hypersonic flow, part B

    NASA Technical Reports Server (NTRS)

    Holden, Michael S.

    1994-01-01

    This report describes the result of experimental studies conducted to examine the effects of the impingement of an oblique shock on the flowfield and surface characteristics of a transpiration-cooled wall in turbulent hypersonic flow. The principal objective of this work was to determine whether the interaction between the oblique shock and the low-momentum region of the transpiration-cooled boundary layer created a highly distorted flowfield and resulted in a significant reduction in the cooling effectiveness of the transpiration-cooled surface. As a part of this program, we also sought to determine the effectiveness of transpiration cooling with nitrogen and helium injectants for a wide range of blowing rates under constant-pressure conditions in the absence of shock interaction. This experimental program was conducted in the Calspan 48-Inch Shock Tunnel at nominal Mach numbers of 6 and 8, for a Reynolds number of 7.5 x 10(exp 6). For these test conditions, we obtained fully turbulent boundary layers upstream of the interaction regions over the transpiration-cooled segment of the flat plate. The experimental program was conducted in two phases. In the first phase, we examined the effects of mass-addition level and coolant properties on the cooling effectiveness of transpiration-cooled surfaces in the absence of shock interaction. In the second phase of the program, we examined the effects of oblique shock impingement on the flowfield and surface characteristics of a transpiration-cooled surface. The studies were conducted for a range of shock strengths with nitrogen and helium coolants to examine how the distribution of heat transfer and pressure and the characteristics of the flowfield in the interaction region varied with shock strength and the level of mass addition from the transpiration-cooled section of the model. The effects of the distribution of the blowing rate along the interaction regions were also examined for a range of blowing rates through the

  20. Evaluation of water cooled supersonic temperature and pressure probes for application to 2000 F flows

    NASA Technical Reports Server (NTRS)

    Lagen, Nicholas T.; Seiner, John M.

    1990-01-01

    The development of water cooled supersonic probes used to study high temperature jet plumes is addressed. These probes are: total pressure, static pressure, and total temperature. The motivation for these experiments is the determination of high temperature supersonic jet mean flow properties. A 3.54 inch exit diameter water cooled nozzle was used in the tests. It is designed for exit Mach 2 at 2000 F exit total temperature. Tests were conducted using water cooled probes capable of operating in Mach 2 flow, up to 2000 F total temperature. Of the two designs tested, an annular cooling method was chosen as superior. Data at the jet exit planes, and along the jet centerline, were obtained for total temperatures of 900 F, 1500 F, and 2000 F, for each of the probes. The data obtained from the total and static pressure probes are consistent with prior low temperature results. However, the data obtained from the total temperature probe was affected by the water coolant. The total temperature probe was tested up to 2000 F with, and without, the cooling system turned on to better understand the heat transfer process at the thermocouple bead. The rate of heat transfer across the thermocouple bead was greater when the coolant was turned on than when the coolant was turned off. This accounted for the lower temperature measurement by the cooled probe. The velocity and Mach number at the exit plane and centerline locations were determined from the Rayleigh-Pitot tube formula.

  1. Local cooling alters neural mechanisms producing changes in peripheral blood flow by spinal cord stimulation.

    PubMed

    Tanaka, Satoshi; Barron, Kirk W; Chandler, Margaret J; Linderoth, Bengt; Foreman, Robert D

    2003-03-28

    This study was performed to investigate the respective role of sensory afferent and sympathetic fibers in peripheral vasodilatation induced by spinal cord stimulation at different hindpaw skin temperatures. Cooling the skin was used as a strategy to enhance sympathetic activity [Am. J. Physiol.: Heart Circ. Physiol. 263 (1992) H1197]. Cutaneous blood flow in the footpad of anesthetized rats was recorded using laser Doppler flowmetry. Local cooling (<25 degrees C) or moderate local cooling (25-28 degrees C) of the hindpaw was produced with a cooling copper coil. Spinal cord stimulation delivered at clinically relevant parameters and with 30%, 60%, and 90% of motor threshold induced the early phase of vasodilatation in the cooled and the moderately cooled hindpaw. In addition, spinal cord stimulation at 90% of motor threshold produced the late phase of vasodilatation only in the cooled hindpaw, which was possible to block by the autonomic ganglion-blocking agent, hexamethonium. The early responses to spinal cord stimulation in the moderately cooled hindpaw were not affected by hexamethonium. In contrast, both the early and the late phase responses were eliminated by CGRP (8-37), an antagonist of the calcitonin gene-related peptide receptor. After dorsal rhizotomy, spinal cord stimulation at 90% of motor threshold elicited hexamethonium-sensitive vasodilatation in the cooled hindpaw (late phase). These results suggest that spinal cord stimulation-induced vasodilatation in the cooled hindpaw (<25 degrees C) is mediated via both the sensory afferent (early phase of vasodilatation) and via suppression of the sympathetic efferent activity (late phase) although the threshold for vasodilatation via the sympathetic efferent fibers is higher than that via sensory nerves. In contrast, vasodilatation via sensory afferent fibers may predominate with moderate temperatures (25-28 degrees C). Thus, two complementary mechanisms for spinal cord stimulation-induced vasodilatation may

  2. Changes in human colonic mucosal-submucosal blood flow after body surface cooling.

    PubMed Central

    Forrester, D W; Davison, J S; Spence, V A; Walker, W F

    1981-01-01

    Mucosal-submucosal blood flow in the human colostomy was measured by a radioisotopic washout technique. Changes in blood flow were recorded in 10 subjects after peripheral vasoconstriction evoked by surface cooling of the body. Accompanying the vasoconstriction was a rise in mucosal-submucosal blood flow of approximately 40%. An interpretation of the blood flow changes and the associated alterations in mean arterial blood pressure provide evidence for vasomotor and local regulatory control in the colostomy microcirculation. We believe, therefore that the colostomy is a suitable preparation for studying the human colonic microcirculation. PMID:7262624

  3. Scanning tunneling microscope with continuous flow cryostat sample cooling

    SciTech Connect

    Behler, S.; Rose, M.K.; Dunphy, J.C.; Ogletree, D.F.; Salmeron, M.; Chapelier, C.

    1997-06-01

    We have constructed an ultrahigh vacuum scanning tunneling microscope (STM) for operation in the temperature range 20{endash}300 K. The design consists of a vibration isolated sample holder mounted on a continuous flow cryostat. By rotation and linear motion of the cryostat, the sample can be positioned in front of various surface preparation and analysis instruments contained in a single vacuum chamber. A lightweight beetle-type STM head is lowered from the top onto the sample by a linear manipulator. To minimize helium convection in the cryostat, the entire vacuum system, including a liquid helium storage Dewar, can be tilted by a few degrees perpendicular to the cryostat axis, which improves the operation. The performance of the instrument is demonstrated by atomically resolved images of the Pd(111) surface and adsorbed CO molecules. {copyright} {ital 1997 American Institute of Physics.}

  4. Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade

    NASA Astrophysics Data System (ADS)

    Szwaba, Ryszard; Kaczynski, Piotr; Doerffer, Piotr; Telega, Janusz

    2016-08-01

    This paper presents the study of the flow structure and heat transfer, and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade. The investigations focus on heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillet, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.

  5. Energy efficiency enhancements for semiconductors, communications, sensors and software achieved in cool silicon cluster project

    NASA Astrophysics Data System (ADS)

    Ellinger, Frank; Mikolajick, Thomas; Fettweis, Gerhard; Hentschel, Dieter; Kolodinski, Sabine; Warnecke, Helmut; Reppe, Thomas; Tzschoppe, Christoph; Dohl, Jan; Carta, Corrado; Fritsche, David; Tretter, Gregor; Wiatr, Maciej; Detlef Kronholz, Stefan; Mikalo, Ricardo Pablo; Heinrich, Harald; Paulo, Robert; Wolf, Robert; Hübner, Johannes; Waltsgott, Johannes; Meißner, Klaus; Richter, Robert; Michler, Oliver; Bausinger, Markus; Mehlich, Heiko; Hahmann, Martin; Möller, Henning; Wiemer, Maik; Holland, Hans-Jürgen; Gärtner, Roberto; Schubert, Stefan; Richter, Alexander; Strobel, Axel; Fehske, Albrecht; Cech, Sebastian; Aßmann, Uwe; Pawlak, Andreas; Schröter, Michael; Finger, Wolfgang; Schumann, Stefan; Höppner, Sebastian; Walter, Dennis; Eisenreich, Holger; Schüffny, René

    2013-07-01

    An overview about the German cluster project Cool Silicon aiming at increasing the energy efficiency for semiconductors, communications, sensors and software is presented. Examples for achievements are: 1000 times reduced gate leakage in transistors using high-fc (HKMG) materials compared to conventional poly-gate (SiON) devices at the same technology node; 700 V transistors integrated in standard 0.35 μm CMOS; solar cell efficiencies above 19% at < 200 W/m2 irradiation; 0.99 power factor, 87% efficiency and 0.088 distortion factor for dc supplies; 1 ns synchronization resolution via Ethernet; database accelerators allowing 85% energy savings for servers; adaptive software yielding energy reduction of 73% for e-Commerce applications; processors and corresponding data links with 40% and 70% energy savings, respectively, by adaption of clock frequency and supply voltage in less than 20 ns; clock generator chip with tunable frequency from 83-666 MHz and 0.62-1.6 mW dc power; 90 Gb/s on-chip link over 6 mm and efficiency of 174 fJ/mm; dynamic biasing system doubling efficiency in power amplifiers; 60 GHz BiCMOS frontends with dc power to bandwidth ratio of 0.17 mW/MHz; driver assistance systems reducing energy consumption by 10% in cars Contribution to the Topical Issue “International Semiconductor Conference Dresden-Grenoble - ISCDG 2012”, Edited by Gérard Ghibaudo, Francis Balestra and Simon Deleonibus.

  6. X-ray observations of complex temperature structure in the cool-core cluster A85

    SciTech Connect

    Schenck, David E.; Datta, Abhirup; Burns, Jack O.; Skillman, Sam

    2014-07-01

    X-ray observations were used to examine the complex temperature structure of A85, a cool-core galaxy cluster. Temperature features can provide evidence of merging events which shock heat the intracluster gas. Temperature maps were made from both Chandra and XMM-Newton observations. The combination of a new, long-exposure XMM observation and an improved temperature map binning technique produced the highest fidelity temperature maps of A85 to date. Hot regions were detected near the subclusters to the south and southwest in both the Chandra and XMM temperature maps. The presence of these structures implies A85 is not relaxed. The hot regions may indicate the presence of shocks. The Mach numbers were estimated to be ∼1.9 at the locations of the hot spots. Observational effects will tend to systematically reduce temperature jumps, so the measured Mach numbers are likely underestimated. Neither temperature map showed evidence for a shock in the vicinity of the presumed radio relic near the southwest subcluster. However, the presence of a weak shock cannot be ruled out. There was tension between the temperatures measured by the two instruments.

  7. Pāhoehoe flow cooling, discharge, and coverage rates from thermal image chronometry

    USGS Publications Warehouse

    Dehn, Jonathan; Hamilton, Christopher M.; Harris, A. J. L.; Herd, Richard A.; James, M.R.; Lodato, Luigi; Steffke, Andrea

    2007-01-01

    Theoretically- and empirically-derived cooling rates for active pāhoehoe lava flows show that surface cooling is controlled by conductive heat loss through a crust that is thickening with the square root of time. The model is based on a linear relationship that links log(time) with surface cooling. This predictable cooling behavior can be used assess the age of recently emplaced sheet flows from their surface temperatures. Using a single thermal image, or image mosaic, this allows quantification of the variation in areal coverage rates and lava discharge rates over 48 hour periods prior to image capture. For pāhoehoe sheet flow at Kīlauea (Hawai`i) this gives coverage rates of 1–5 m2/min at discharge rates of 0.01–0.05 m3/s, increasing to ∼40 m2/min at 0.4–0.5 m3/s. Our thermal chronometry approach represents a quick and easy method of tracking flow advance over a three-day period using a single, thermal snap-shot.

  8. X-Ray Thermal Coronae of Galaxies in Hot Clusters: Ubiquity of Embedded Mini-Cooling Cores

    NASA Astrophysics Data System (ADS)

    Sun, M.; Jones, C.; Forman, W.; Vikhlinin, A.; Donahue, M.; Voit, M.

    2007-03-01

    We present a systematic investigation of X-ray thermal coronae in 157 early-type and 22 late-type galaxies from a survey of 25 hot (kT>3 keV), nearby (z<0.05) clusters, based on Chandra archival data. Cool galactic coronae (kT=0.5-1.1 keV generally) have been found to be common, >60% in LKs>2L* galaxies. These embedded coronae in hot clusters are generally smaller, less luminous, and less massive than coronae in poor environments, demonstrating the negative effects of hot cluster environments on galactic coronae. Nevertheless, these coronae still manage to survive ICM stripping, evaporation, rapid cooling, and powerful AGN outflows, making them a rich source of information about gas stripping, microscopic transport, and feedback processes in the cluster environment. Heat conduction across the boundary of the coronae has to be suppressed by a factor of >~100, which implies that the X-ray gas in early-type galaxies is magnetized and the magnetic field plays an important role in energy transfer. The luminous, embedded coronae, with high central density (0.1-0.4 cm-3), are miniversions of group and cluster cooling cores. As the prevalence of coronae of massive galaxies implies a long lifetime (>~several Gyr), there must be a heat source inside coronae to offset cooling. While we argue that AGN heating may not generally be the heat source, we conclude that SN heating can be enough as long as the kinetic energy of SNe can be efficiently dissipated. Diffuse thermal coronae have also been detected in at least 8 of 22 late-type galaxies in our sample. The fraction of luminous X-ray AGNs (>1041 ergs s-1) is not small (~5%) in our sample.

  9. RADIO AND DEEP CHANDRA OBSERVATIONS OF THE DISTURBED COOL CORE CLUSTER ABELL 133

    SciTech Connect

    Randall, S. W.; Nulsen, P. E. J.; Forman, W. R.; Murray, S. S.; Clarke, T. E.; Owers, M. S.; Sarazin, C. L.

    2010-10-10

    We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features. The plume is capped with a filamentary radio structure that has been previously classified as a radio relic. X-ray spectral fits in the region of the relic indicate the presence of either high-temperature gas or non-thermal emission, although the measured photon index is flatter than would be expected if the non-thermal emission is from inverse Compton scattering of the cosmic microwave background by the radio-emitting particles. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, which we show is consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic, and has properties consistent with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing spiral viewed edge-on. Results from spectral analysis of the wing-like features are inconsistent with the previous suggestion that the wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by displacement of X-ray gas by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their optical and UV counterparts, suggestive of a galaxy-galaxy merger event. On larger scales, there is evidence for cluster substructure in both optical observations and the X-ray temperature map. We suggest that the Abell 133 cluster has recently undergone a merger event with an interloping subgroup, initialing gas sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged appearance of the elliptical surface brightness edge. We show

  10. Petaflop hydrokinetic simulations of complex flows on massive GPU clusters

    NASA Astrophysics Data System (ADS)

    Bernaschi, M.; Bisson, M.; Fatica, M.; Melchionna, S.; Succi, S.

    2013-02-01

    We present recent extensions of the MUPHY computational framework for multi-scale simulation of complex bio-fluidic phenomena in real-life geometries. The new framework, which builds on concurrent advances of the computational modeling and parallelization techniques, is able to simulate suspensions with several hundreds of millions of finite-size bodies, interacting with each other and with the surrounding fluid, in geometries of realistic anatomic complexity. Blood flow through the human coronary arteries, at physiological hematocrit values, is simulated with a spatial resolution of 10 micrometers, comparable with the size of red blood cells. The simulation exhibits excellent parallel scalability on a cluster of 4000 M2050 Nvidia GPUs, with an aggregate performance close to 1 Petaflop/s.

  11. Flow and Thermal Performance of a Water-Cooled Periodic Transversal Elliptical Microchannel Heat Sink for Chip Cooling.

    PubMed

    Wei, Bo; Yang, Mo; Wang, Zhiyun; Xu, Hongtao; Zhang, Yuwen

    2015-04-01

    Flow and thermal performance of transversal elliptical microchannels were investigated as a passive scheme to enhance the heat transfer performance of laminar fluid flow. The periodic transversal elliptical micro-channel is designed and its pressure drop and heat transfer characteristics in laminar flow are numerically investigated. Based on the comparison with a conventional straight micro- channel having rectangular cross section, it is found that periodic transversal elliptical microchannel not only has great potential to reduce pressure drop but also dramatically enhances heat transfer performance. In addition, when the Reynolds number equals to 192, the pressure drop of the transversal elliptical channel is 36.5% lower than that of the straight channel, while the average Nusselt number is 72.8% higher; this indicates that the overall thermal performance of the periodic transversal elliptical microchannel is superior to the conventional straight microchannel. It is suggested that such transversal elliptical microchannel are attractive candidates for cooling future electronic chips effectively with much lower pressure drop. PMID:26353536

  12. Thermal characteristics of air flow cooling in the lithium ion batteries experimental chamber

    SciTech Connect

    Lukhanin A.; Rohatgi U.; Belyaev, A.; Fedorchenko, D.; Khazhmuradov, M.; Lukhanin, O; Rudychev, I.

    2012-07-08

    A battery pack prototype has been designed and built to evaluate various air cooling concepts for the thermal management of Li-ion batteries. The heat generation from the Li-Ion batteries was simulated with electrical heat generation devices with the same dimensions as the Li-Ion battery (200 mm x 150 mm x 12 mm). Each battery simulator generates up to 15W of heat. There are 20 temperature probes placed uniformly on the surface of the battery simulator, which can measure temperatures in the range from -40 C to +120 C. The prototype for the pack has up to 100 battery simulators and temperature probes are recorder using a PC based DAQ system. We can measure the average surface temperature of the simulator, temperature distribution on each surface and temperature distributions in the pack. The pack which holds the battery simulators is built as a crate, with adjustable gap (varies from 2mm to 5mm) between the simulators for air flow channel studies. The total system flow rate and the inlet flow temperature are controlled during the test. The cooling channel with various heat transfer enhancing devices can be installed between the simulators to investigate the cooling performance. The prototype was designed to configure the number of cooling channels from one to hundred Li-ion battery simulators. The pack is thermally isolated which prevents heat transfer from the pack to the surroundings. The flow device can provide the air flow rate in the gap of up to 5m/s velocity and air temperature in the range from -30 C to +50 C. Test results are compared with computational modeling of the test configurations. The present test set up will be used for future tests for developing and validating new cooling concepts such as surface conditions or heat pipes.

  13. Experimental study on heat transfer and flow resistance in improved latticework cooling channels

    NASA Astrophysics Data System (ADS)

    Deng, Hongwu; Wang, Kai; Zhu, Jianqin; Pan, Wenyan

    2013-06-01

    Characteristics of heat transfer and flow resistance of the latticework (vortex) cooling channel with ribs truncated at their two ends were theoretically and experimentally studied compared with regular and smooth channels of the same configuration. The results showed: the heat transfer efficiency of the latticework channel with two slots was better than those of regular and smooth channels of the same configuration, its flow resistance situation in the slotted channel becomes quite complex; The flow resistances of 2 mm- and 4 mm-slotted channels were obviously lower than that of the regular channel, but they are still much higher than that of the smooth channel; Compared with the regular channel, the total heat transfer efficiencies of the slotted channels were pretty improved, among them the 4-mm slotted channel has the biggest enhancement. From the experimental results, it is obvious that the latticework channel with proper slots has a great prospect in the design of the inner cooling channels of turbine blades.

  14. A Numerical Analysis on Freezing Behavior of Flowing Water inside a Pipe Cooled from Surroundings

    NASA Astrophysics Data System (ADS)

    Chiba, Ryoichi; Izumi, Masaaki

    A freezing phenomenon in forced convectional flow inside a pipe is investigated numerically in this paper .The numerical analysis is carried out to assess the transient freezing behavior of flowing water inside a pipe cooled from surroundings in consideration of pressure drop caused by the freezing. The finite element technique is applied to solve the equations of motion and energy transport for laminar flow. The numerical model attempts to capture the solid-fluid interface on a fixed computational grid. The correlations among cooling conditions of pipe, velocity and temperature of water at the inlet, and location at which the freezing starts are examined to show the critical velocity to avoid freezing. In addition, under the condition that pressure remains constant at the inlet, the period in which the pipe is not blockaded by ice is calculated. The period is illustrated with some dimensionless parameters to predict the conditions under which blockage occurs within a given time.

  15. Mitigation of Autoignition Due to Premixing in a Hypervelocity Flow Using Active Wall Cooling

    NASA Technical Reports Server (NTRS)

    Axdahl, Erik; Kumar, Ajay; Wilhite, Alan

    2013-01-01

    Preinjection of fuel on the forebody of an airbreathing vehicle is a proposed method to gain access to hypervelocity flight Mach numbers. However, this creates the possibility of autoignition either near the wall or in the core of the flow, thereby consuming fuel prematurely as well as increasing the amount of pressure drag on the vehicle. The computational fluid dynamics code VULCAN was used to conduct three dimensional simulations of the reacting flow in the vicinity of hydrogen injectors on a flat plate at conditions relevant to a Mach 12 notional flight vehicle forebody to determine the location where autoignition occurs. Active wall cooling strategies were formulated and simulated in response to regions of autoignition. It was found that tangential film cooling using hydrogen or helium were both able to nearly or completely eliminate wall autoignition in the flow domain of interest.

  16. Cooling, degassing and compaction of rhyolitic ash flow tuffs: a computational model

    USGS Publications Warehouse

    Riehle, J.R.; Miller, T.F.; Bailey, R.A.

    1995-01-01

    Previous models of degassing, cooling and compaction of rhyolitic ash flow deposits are combined in a single computational model that runs on a personal computer. The model applies to a broader range of initial and boundary conditions than Riehle's earlier model, which did not integrate heat and mass flux with compaction and which for compound units was limited to two deposits. Model temperatures and gas pressures compare well with simple measured examples. The results indicate that degassing of volatiles present at deposition occurs within days to a few weeks. Compaction occurs for weeks to two to three years unless halted by devitrification; near-emplacement temperatures can persist for tens of years in the interiors of thick deposits. Even modest rainfall significantly chills the upper parts of ash deposits, but compaction in simple cooling units ends before chilling by rainwater influences cooling of the interior of the sheet. Rainfall does, however, affect compaction at the boundaries of deposits in compound cooling units, because the influx of heat from the overlying unit is inadequate to overcome heat previously lost to vaporization of water. Three density profiles from the Matahina Ignimbrite, a compound cooling unit, are fairly well reproduced by the model despite complexities arising from numerous cooling breaks. Uncertainties in attempts to correlate in detail among the profiles may be the result of the non-uniform distribution of individual deposits. Regardless, it is inferred that model compaction is approximately valid. Thus the model should be of use in reconstructing the emplacement history of compound ash deposits, for inferring the depositional environments of ancient deposits and for assessing how long deposits of modern ash flows are capable of generating phreatic eruptions or secondary ash flows. ?? 1995 Springer-Verlag.

  17. HIGH-REDSHIFT COOL-CORE GALAXY CLUSTERS DETECTED VIA THE SUNYAEV-ZEL'DOVICH EFFECT IN THE SOUTH POLE TELESCOPE SURVEY

    SciTech Connect

    Semler, D. R.; Suhada, R.; Bazin, G.; Bocquet, S.; Desai, S.; Aird, K. A.; Ashby, M. L. N.; Bayliss, M.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Brodwin, M.; Cho, H. M.; Clocchiatti, A.; De Haan, T.; Dobbs, M. A.; and others

    2012-12-20

    We report the first investigation of cool-core properties of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect. We use 13 galaxy clusters uniformly selected from 178 deg{sup 2} observed with the South Pole Telescope (SPT) and followed up by the Chandra X-ray Observatory. They form an approximately mass-limited sample (>3 Multiplication-Sign 10{sup 14} M{sub Sun} h {sup -1}{sub 70}) spanning redshifts 0.3 < z < 1.1. Using previously published X-ray-selected cluster samples, we compare two proxies of cool-core strength: surface brightness concentration (c{sub SB}) and cuspiness ({alpha}). We find that c{sub SB} is better constrained. We measure c{sub SB} for the SPT sample and find several new z > 0.5 cool-core clusters, including two strong cool cores. This rules out the hypothesis that there are no z > 0.5 clusters that qualify as strong cool cores at the 5.4{sigma} level. The fraction of strong cool-core clusters in the SPT sample in this redshift regime is between 7% and 56% (95% confidence). Although the SPT selection function is significantly different from the X-ray samples, the high-z c{sub SB} distribution for the SPT sample is statistically consistent with that of X-ray-selected samples at both low and high redshifts. The cool-core strength is inversely correlated with the offset between the brightest cluster galaxy and the X-ray centroid, providing evidence that the dynamical state affects the cool-core strength of the cluster. Larger SZ-selected samples will be crucial in understanding the evolution of cluster cool cores over cosmic time.

  18. Low cryogen inventory, forced flow Ne cooling system with room temperature compression stage and heat recuperation

    NASA Astrophysics Data System (ADS)

    Shornikov, A.; Krantz, C.; Wolf, A.

    2014-01-01

    We present design and commissioning results of a forced flow cooling system utilizing neon at 30 K. The cryogen is pumped through the system by a room-temperature compression stage. To decouple the cold zone from the compression stage a recuperating counterflow tube-in-tube heat exchanger is used. Commissioning demonstrated successful condensation of neon and transfer of up to 30 W cooling power to the load at 30 K using only 30 g of the cryogen circulating in the system at pressures below 170 kPa.

  19. AGN-driven perturbations in the intracluster medium of the cool-core cluster ZwCl 2701

    NASA Astrophysics Data System (ADS)

    Vagshette, Nilkanth D.; Sonkamble, Satish S.; Naik, Sachindra; Patil, Madhav K.

    2016-09-01

    We present the results obtained from a total of 123 ks X-ray (Chandra) and 8 h of 1.4 GHz radio (Giant Metrewave Radio Telescope - GMRT) observations of the cool-core cluster ZwCl 2701 (z = 0.214). These observations of ZwCl 2701 showed the presence of an extensive pair of ellipsoidal cavities along the east and west directions within the central region < 20 kpc. Detection of bright rims around the cavities suggested that the radio lobes displaced X-ray-emitting hot gas forming shell-like structures. The total cavity power (mechanical power) that directly heated the surrounding gas and cooling luminosity of the cluster were estimated to be ˜2.27 × 1045 erg s-1 and 3.5 × 1044 erg s-1 , respectively. Comparable values of cavity power and cooling luminosity of ZwCl 2701 suggested that the mechanical power of the active galactic nuclei (AGN) outburst is large enough to balance the radiative cooling in the system. The star formation rate derived from the Hα luminosity was found to be ˜0.60 M⊙ yr-1, which is about three orders of magnitude lower than the cooling rate of ˜196 M⊙ yr-1. Detection of the floor in entropy profile of ZwCl 2701 suggested the presence of an alternative heating mechanism at the centre of the cluster. Lower value of the ratio (˜10-2) between black hole mass accretion rate and Eddington mass accretion rate suggested that launching of jet from the super massive black hole is efficient in ZwCl 2701. However, higher value of ratio (˜103) between black hole mass accretion rate and Bondi accretion rate indicated that the accretion rate required to create cavities is well above the Bondi accretion rate.

  20. Measurements of Heat Transfer, Flow, and Pressures in a Simulated Turbine Blade Internal Cooling Passage

    NASA Technical Reports Server (NTRS)

    Russell, Louis M.; Thurman, Douglas R.; Poinsatte, Philip E.; Hippensteele, Steven A.

    1998-01-01

    An experimental study was made to obtain quantitative information on heat transfer, flow, and pressure distribution in a branched duct test section that had several significant features of an internal cooling passage of a turbine blade. The objective of this study was to generate a set of experimental data that could be used for validation of computer codes that would be used to model internal cooling. Surface heat transfer coefficients and entrance flow conditions were measured at nominal entrance Reynolds numbers of 45,000, 335,000, and 726,000. Heat transfer data were obtained by using a steady-state technique in which an Inconel heater sheet is attached to the surface and coated with liquid crystals. Visual and quantitative flow-field data from particle image velocimetry measurements for a plane at midchannel height for a Reynolds number of 45,000 were also obtained. The flow was seeded with polystyrene particles and illuminated by a laser light sheet. Pressure distribution measurements were made both on the surface with discrete holes and in the flow field with a total pressure probe. The flow-field measurements yielded flow-field velocities at selected locations. A relatively new method, pressure sensitive paint, was also used to measure surface pressure distribution. The pressure paint data obtained at Reynolds numbers of 335,000 and 726,000 compared well with the more standard method of measuring pressures by using discrete holes.

  1. Galaxy Cluster Bulk Flows and Collision Velocities in QUMOND

    NASA Astrophysics Data System (ADS)

    Katz, Harley; McGaugh, Stacy; Teuben, Peter; Angus, G. W.

    2013-07-01

    We examine the formation of clusters of galaxies in numerical simulations of a QUMOND cosmogony with massive sterile neutrinos. Clusters formed in these exploratory simulations develop higher velocities than those found in ΛCDM simulations. The bulk motions of clusters attain ~1000 km s-1 by low redshift, comparable to observations whereas ΛCDM simulated clusters tend to fall short. Similarly, high pairwise velocities are common in cluster-cluster collisions like the Bullet Cluster. There is also a propensity for the most massive clusters to be larger in QUMOND and to appear earlier than in ΛCDM, potentially providing an explanation for "pink elephants" like El Gordo. However, it is not obvious that the cluster mass function can be recovered.

  2. GALAXY CLUSTER BULK FLOWS AND COLLISION VELOCITIES IN QUMOND

    SciTech Connect

    Katz, Harley; McGaugh, Stacy; Teuben, Peter; Angus, G. W. E-mail: stacy.mcgaugh@case.edu E-mail: angus.gz@gmail.com

    2013-07-20

    We examine the formation of clusters of galaxies in numerical simulations of a QUMOND cosmogony with massive sterile neutrinos. Clusters formed in these exploratory simulations develop higher velocities than those found in {Lambda}CDM simulations. The bulk motions of clusters attain {approx}1000 km s{sup -1} by low redshift, comparable to observations whereas {Lambda}CDM simulated clusters tend to fall short. Similarly, high pairwise velocities are common in cluster-cluster collisions like the Bullet Cluster. There is also a propensity for the most massive clusters to be larger in QUMOND and to appear earlier than in {Lambda}CDM, potentially providing an explanation for ''pink elephants'' like El Gordo. However, it is not obvious that the cluster mass function can be recovered.

  3. Experimental investigation of film cooling flow induced by shaped holes on a turbine blade.

    PubMed

    Barthet, S; Bario, F

    2001-05-01

    The present study is the second half of a piece of work carried out in collaboration with SNECMA. It investigates shaped hole film cooling, numerically and experimentally. The aim of this paper is the experimental analysis of shaped hole film cooling on a large scale turbine blade (1.4 m chord). The test section is a large scale turbine inlet guide vane cascade. The test airfoil is equipped with a row of nine 50 degrees sloped shaped holes. They are located on the suction side at 20% of the curvilinear length of the blade from the stagnation point. The inlet film cooling hole diameter is 12 mm. The jet flow is heated to 55 degrees C above the crossflow temperature. Velocity and temperature field measurements have been done to obtain mean and fluctuating values. The results are compared to those obtained by Béral on the same experimental apparatus and in the same test conditions, for a row of cylindrical holes.

  4. Exploring Inflated Pahohoe Lava Flow Morphologies and the Effects of Cooling Using a New Simulation Approach

    NASA Technical Reports Server (NTRS)

    Glaze, L. S.; Baloga, S. M.

    2014-01-01

    Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth (e.g., Figure 1) indicate that the emplacement process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. Thus, interpretation of emplacement conditions for pahoehoe lava flows on Mars requires fundamentally different models. A new model that implements a simulation approach has recently been developed that allows exploration of a variety of key influences on pahoehoe lobe emplacement (e.g., source shape, confinement, slope). One important factor that has an impact on the final topographic shape and morphology of a pahoehoe lobe is the volumetric flow rate of lava, where cooling of lava on the lobe surface influences the likelihood of subsequent breakouts.

  5. Flow and heat transfer measurements in a pseudo-shock region with surface cooling

    NASA Technical Reports Server (NTRS)

    Cuffel, R. F.; Back, L. H.

    1976-01-01

    An experimental investigation was conducted to acquire information on the flow structure, mean flowfield, and temperature distributions in a pseudo-shock region in a supersonic diffuser with surface cooling. The Mach number upstream was 2.9, and the wall to stagnation temperature ratio was 0.44. A Mach-disk-like shock wave emanated from the thin separated flow region near the beginning of the compression region, and reattachment occurred one diameter downstream so that the flow was not separated over most of the pseudo-shock region. The flow compression was a shock-free, predominantly viscous process. Along the pseudo-shock region the measured heat-transfer coefficient increased approximately as the 0.8 power of the measured wall static pressure. The estimated wall shear stress increased downstream of flow attachment, but was still considerably less than the upstream value.

  6. Turbine endwall film cooling with combustor-turbine interface gap leakage flow: Effect of incidence angle

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Yuan, Xin

    2013-04-01

    This paper is focused on the film cooling performance of combustor-turbine leakage flow at off-design condition. The influence of incidence angle on film cooling effectiveness on first-stage vane endwall with combustor-turbine interface slot is studied. A baseline slot configuration is tested in a low speed four-blade cascade comprising a large-scale model of the GE-E3Nozzle Guide Vane (NGV). The slot has a forward expansion angle of 30 deg. to the endwall surface. The Reynolds number based on the axial chord and inlet velocity of the free-stream flow is 3.5 × 105 and the testing is done in a four-blade cascade with low Mach number condition (0.1 at the inlet). The blowing ratio of the coolant through the interface gap varies from M = 0.1 to M = 0.3, while the blowing ratio varies from M = 0.7 to M = 1.3 for the endwall film cooling holes. The film-cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique. The results show that with an increasing blowing ratio the film-cooling effectiveness increases on the endwall. As the incidence angle varies from i = +10 deg. to i = -10 deg., at low blowing ratio, the averaged film-cooling effectiveness changes slightly near the leading edge suction side area. The case of i = +10 deg. has better film-cooling performance at the downstream part of this region where the axial chord is between 0.15 and 0.25. However, the disadvantage of positive incidence appears when the blowing ratio increases, especially at the upstream part of near suction side region where the axial chord is between 0 and 0.15. On the main passage endwall surface, as the incidence angle changes from i = +10 deg. to i = -10 deg., the averaged film-cooling effectiveness changes slightly and the negative incidence appears to be more effective for the downstream part film cooling of the endwall surface where the axial chord is between 0.6 and 0.8.

  7. Heat/mass transfer and flow characteristics of pin fin cooling channels in turbine blades

    NASA Astrophysics Data System (ADS)

    Lau, S. C.; Saxena, A.

    Experiments studied the local heat/mass transfer distributions and pressure drops in pin fin channels that modeled internal cooling passages in gas turbine blades. Heat/mass transfer distributions were determined for a straight flow through a pin fin channel (H/D = 1.0, X/D = S/D = 2.5) and a flow through the pin fin channel with trailing edge flow ejection. The overall friction factor and local pressure drop results were obtained for various configurations and lengths of the trailing edge ejection holes. The results show that, when there is trailing edge flow ejection, the main flow stream turns toward the trailing edge ejection holes. The wake regions downstream of the pins and the regions affected by secondary flow shift toward the ejection holes. The local channel wall heat/mass transfer is generally high immediately upstream of a pin, in the wake region downstream of a pin, and in the regions affected by secondary flow. In the case with trailing edge flow ejection, the heat/mass transfer generally decreases in the radial direction as a result of the reducing radial mass flow rate. The overall friction is higher when the trailing edge ejection holes are longer and when they are configured such that more flow is forced further downstream in the pin fin channel before exiting through the ejection holes.

  8. CONNECTING STAR FORMATION QUENCHING WITH GALAXY STRUCTURE AND SUPERMASSIVE BLACK HOLES THROUGH GRAVITATIONAL HEATING OF COOLING FLOWS

    SciTech Connect

    Guo, Fulai

    2014-12-20

    Recent observations suggested that star formation quenching in galaxies is related to galaxy structure. Here we propose a new mechanism to explain the physical origin of this correlation. We assume that while quenching is maintained in quiescent galaxies by a feedback mechanism, cooling flows in the hot halo gas can still develop intermittently. We study cooling flows in a large suite of around 90 hydrodynamic simulations of an isolated galaxy group, and find that the flow development depends significantly on the gravitational potential well in the central galaxy. If the galaxy's gravity is not strong enough, cooling flows result in a central cooling catastrophe, supplying cold gas and feeding star formation to galactic bulges. When the bulge grows prominent enough, compressional heating starts to offset radiative cooling and maintains cooling flows in a long-term hot mode without producing a cooling catastrophe. Our model thus describes a self-limited growth channel for galaxy bulges and naturally explains the connection between quenching and bulge prominence. In particular, we explicitly demonstrate that M{sub ∗}/R{sub eff}{sup 1.5} is a good structural predictor of quenching. We further find that the gravity from the central supermassive black hole also affects the bimodal fate of cooling flows, and we predict a more general quenching predictor to be M{sub bh}{sup 1.6}M{sub ∗}/R{sub eff}{sup 1.5}, which may be tested in future observational studies.

  9. Observations of the effect of wind on the cooling of active lava flows

    USGS Publications Warehouse

    Keszthelyi, L.; Harris, A.J.L.; Dehn, J.

    2003-01-01

    We present the first direct observations of the cooling of active lava flows by the wind. We confirm that atmospheric convective cooling processes (i.e., the wind) dominate heat loss over the lifetime of a typical pahochoe lava flow. In fact, the heat extracted by convection is greater than predicted, especially at wind speeds less than 5 m/s and surface temperatures less than 400??C. We currently estimate that the atmospheric heat transfer coefficient is about 45-50 W m-2 K-1 for a 10 m/s wind and a surface temperature ???500??C. Further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds.

  10. The inviscid stability of supersonic flow past heated or cooled axisymmetric bodies

    NASA Technical Reports Server (NTRS)

    Shaw, Stephen J.; Duck, Peter W.

    1992-01-01

    The inviscid, linear, nonaxisymmetric, temporal stability of the boundary layer associated with the supersonic flow past axisymmetric bodies (with particular emphasis on long thin, straight circular cylinders), subject to heated or cooled wall conditions is investigated. The eigenvalue problem is computed in some detail for a particular Mach number or 3.8, revealing that the effect of curvature and the choice of wall conditions both have a significant effect on the stability of the flow. Both the asymptotic, large azimuthal wavenumber solution and the asymptotic, far downstream solution are obtained for the stability analysis and compared with numerical results. Additionally, asymptotic analyses valid for large radii of curvature with cooled/heated wall conditions are presented. In general, important differences were found to exist between the wall temperature conditions imposed and the adiabatic wall conditions considered previously.

  11. The inviscid stability of supersonic flow past heated or cooled axisymmetric bodies

    NASA Technical Reports Server (NTRS)

    Shaw, Stephen J.; Duck, Peter W.

    1990-01-01

    The inviscid, linear, nonaxisymmetric, temporal stability of the boundary layer associated with the supersonic flow past axisymmetric bodies (with particular emphasis on long thin, straight circular cylinders), subject to heated or cooled wall conditions is investigated. The eigenvalue problem is computed in some detail for a particular Mach number or 3.8, revealing that the effect of curvature and the choice of wall conditions both have a significant effect on the stability of the flow. Both the asymptotic, large azimuthal wavenumber solution and the asymptotic, far downstream solution are obtained for the stability analysis and compared with numerical results. Additionally, asymptotic analyses valid for large radii of curvature with cooled/heated wall conditions, are presented. In general, important differences were found to exist between the wall temperature conditions imposed and the adiabatic wall conditions considered previously.

  12. High Temperature Ceramic Guide Vane Temperature and Pressure Distribution Calculation for Flow with Cooling Jets

    NASA Technical Reports Server (NTRS)

    Srivastava, Rakesh

    2004-01-01

    A ceramic guide vane has been designed and tested for operation under high temperature. Previous efforts have suggested that some cooling flow may be required to alleviate the high temperatures observed near the trailing edge region. The present report describes briefly a three-dimensional viscous analysis carried out to calculate the temperature and pressure distribution on the blade surface and in the flow path with a jet of cooling air exiting from the suction surface near the trailing edge region. The data for analysis was obtained from Dr. Craig Robinson. The surface temperature and pressure distribution along with a flowfield distribution is shown in the results. The surface distribution is also given in a tabular form at the end of the document.

  13. Determination of cooling air mass flow for a horizontally-opposed aircraft engine installation

    NASA Technical Reports Server (NTRS)

    Miley, S. J.; Cross, E. J., Jr.; Ghomi, N. A.; Bridges, P. D.

    1979-01-01

    The relationship between the amount of cooling air flow and the corresponding flow pressure difference across an aircraft engine was investigated in flight and on the ground. The flight test results were consistent with theory, but indicated a significant installation leakage problem. A ground test blower system was used to identify and reduce the leakage. The correlation between ground test cell determined engine orifice characteristics and flight measurements showed good agreement if the engine pressure difference was based on total pressure rather than static pressure.

  14. Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling.

    PubMed

    Rogiers, Suzy Y; Clarke, Simon J

    2013-01-01

    Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled.

  15. Effects of turbulent flow field on wavefront aberration in liquid-convection-cooled disk laser oscillator

    NASA Astrophysics Data System (ADS)

    Li, Peilin; Fu, Xing; Liu, Qiang; Gong, Mali

    2015-05-01

    A liquid-convection-cooled Nd:YAG disk laser oscillator with an output power of 30.7 W and a slope efficiency of 14.1 % is built. By using large-eddy simulation model, the wavefront aberration induced by the turbulent flow is numerically calculated. In the experiment, a Shack-Hartmann wavefront sensor is used to measure the wavefront aberration and the laser intensity distribution. The RMS values and PV values of the beam wavefront and the phase stability of three feature points have been investigated. The experimental results prove that the turbulent flow with high flow velocity and high turbulent intensity can reduce the aberration of the flow field.

  16. Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

    NASA Technical Reports Server (NTRS)

    Braman, K. E.; Ruf, J. H.

    2015-01-01

    Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated using RANS and URANS for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and for four approximations of the supersonic film injection geometry, each of which was created with a different simplification of the test article geometry. The results show that although a reasonable match to experiment can be obtained with varying levels of geometric fidelity, the modeling choices made do not fully represent the physics of flow separation in a TIC nozzle with film cooling.

  17. Mapping the particle acceleration in the cool core of the galaxy cluster RX J1720.1+2638

    SciTech Connect

    Giacintucci, S.; Markevitch, M.; Brunetti, G.; Venturi, T.; ZuHone, J. A.

    2014-11-01

    We present new deep, high-resolution radio images of the diffuse minihalo in the cool core of the galaxy cluster RX J1720.1+2638. The images have been obtained with the Giant Metrewave Radio Telescope at 317, 617, and 1280 MHz and with the Very Large Array at 1.5, 4.9, and 8.4 GHz, with angular resolutions ranging from 1'' to 10''. This represents the best radio spectral and imaging data set for any minihalo. Most of the radio flux of the minihalo arises from a bright central component with a maximum radius of ∼80 kpc. A fainter tail of emission extends out from the central component to form a spiral-shaped structure with a length of ∼230 kpc, seen at frequencies 1.5 GHz and below. We find indication of a possible steepening of the total radio spectrum of the minihalo at high frequencies. Furthermore, a spectral index image shows that the spectrum of the diffuse emission steepens with increasing distance along the tail. A striking spatial correlation is observed between the minihalo emission and two cold fronts visible in the Chandra X-ray image of this cool core. These cold fronts confine the minihalo, as also seen in numerical simulations of minihalo formation by sloshing-induced turbulence. All these observations favor the hypothesis that the radio-emitting electrons in cluster cool cores are produced by turbulent re-acceleration.

  18. Formation of Globular Clusters in Atomic-cooling Halos Via Rapid Gas Condensation and Fragmentation during the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Kimm, Taysun; Cen, Renyue; Rosdahl, Joakim; Yi, Sukyoung K.

    2016-05-01

    We investigate the formation of metal-poor globular clusters (GCs) at the center of two dark matter halos with {M}{{halo}}˜ 4× {10}7 {M}⊙ at z\\gt 10 using cosmological radiation-hydrodynamics simulations. We find that very compact (≲1 pc) and massive (˜ 6× {10}5 {M}⊙ ) clusters form rapidly when pristine gas collapses isothermally with the aid of efficient Lyα emission during the transition from molecular-cooling halos to atomic-cooling halos. Because the local free-fall time of dense star-forming gas is very short (\\ll 1 {{Myr}}), a large fraction of the collapsed gas is turned into stars before stellar feedback processes blow out the gas and shut down star formation. Although the early stage of star formation is limited to a small region of the central star-forming disk, we find that the disk quickly fragments due to metal enrichment from supernovae. Sub-clusters formed in the fragmented clouds eventually merge with the main cluster at the center. The simulated clusters closely resemble the local GCs in mass and size but show a metallicity spread that is much wider than found in the local GCs. We discuss a role of pre-enrichment by Pop III and II stars as a potential solution to the latter issue. Although not without shortcomings, it is encouraging that a naive blind (not tuned) cosmological simulation presents a possible channel for the formation of at least some massive GCs.

  19. FORMATION OF COMPACT STELLAR CLUSTERS BY HIGH-REDSHIFT GALAXY OUTFLOWS. II. EFFECT OF TURBULENCE AND METAL-LINE COOLING

    SciTech Connect

    Gray, William J.; Scannapieco, Evan

    2011-06-01

    In the primordial universe, low-mass structures with virial temperatures less than 10{sup 4} K were unable to cool by atomic line transitions, leading to a strong suppression of star formation. On the other hand, these 'minihalos' were highly prone to triggered star formation by interactions from nearby galaxy outflows. In Gray and Scannapieco, we explored the impact of nonequilibrium chemistry on these interactions. Here we turn our attention to the role of metals, carrying out a series of high-resolution three-dimensional adaptive mesh refinement simulations that include both metal cooling and a subgrid turbulent mixing model. Despite the presence of an additional coolant, we again find that outflow-minihalo interactions produce a distribution of dense, massive stellar clusters. We also find that these clusters are evenly enriched with metals to a final abundance of Z {approx} 10{sup -2} Z{sub sun}. As in our previous simulations, all of these properties suggest that these interactions may have given rise to present-day halo globular clusters.

  20. Incorporation of cooling-induced crystallization into a 2-dimensional axisymmetric conduit heat flow model

    NASA Astrophysics Data System (ADS)

    Heptinstall, David; Bouvet de Maisonneuve, Caroline; Neuberg, Jurgen; Taisne, Benoit; Collinson, Amy

    2016-04-01

    Heat flow models can bring new insights into the thermal and rheological evolution of volcanic 3 systems. We shall investigate the thermal processes and timescales in a crystallizing, static 4 magma column, with a heat flow model of Soufriere Hills Volcano (SHV), Montserrat. The latent heat of crystallization is initially computed with MELTS, as a function of pressure and temperature for an andesitic melt (SHV groundmass starting composition). Three fractional crystallization simulations are performed; two with initial pressures of 34MPa (runs 1 & 2) and one of 25MPa (run 3). Decompression rate was varied between 0.1MPa/° C (runs 1 & 3) and 0.2MPa/° C (run 2). Natural and experimental matrix glass compositions are accurately reproduced by all MELTS runs. The cumulative latent heat released for runs 1, 2 and 3 differs by less than 9% (8.69E5 J/kg*K, 9.32E5 J/kg*K, and 9.49E5 J/kg*K respectively). The 2D axisymmetric conductive cooling simulations consider a 30m-diameter conduit that extends from the surface to a depth of 1500m (34MPa). The temporal evolution of temperature is closely tracked at depths of 10m, 750m and 1400m in the centre of the conduit, at the conduit walls, and 20m from the walls into the host rock. Following initial cooling by 7-15oC at 10m depth inside the conduit, the magma temperature rebounds through latent heat release by 32-35oC over 85-123 days to a maximum temperature of 1002-1005oC. At 10m depth, it takes 4.1-9.2 years for the magma column to cool by 108-131oC and crystallize to 75wt%, at which point it cannot be easily remobilized. It takes 11-31.5 years to reach the same crystallinity at 750-1400m depth. We find a wide range in cooling timescales, particularly at depths of 750m or greater, attributed to the initial run pressure and the dominant latent heat producing crystallizing phase, Albite-rich Plagioclase Feldspar. Run 1 is shown to cool fastest and run 3 cool the slowest, with surface emissivity having the strongest cooling

  1. Effect of Coolant Temperature and Mass Flow on Film Cooling of Turbine Blades

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.; Gaugler, Raymond E.

    1997-01-01

    A three-dimensional Navier Stokes code has been used to study the effect of coolant temperature, and coolant to mainstream mass flow ratio on the adiabatic effectiveness of a film-cooled turbine blade. The blade chosen is the VKI rotor with six rows of cooling holes including three rows on the shower head. The mainstream is akin to that under real engine conditions with stagnation temperature = 1900 K and stagnation pressure = 3 MPa. Generally, the adiabatic effectiveness is lower for a higher coolant temperature due to nonlinear effects via the compressibility of air. However, over the suction side of shower-head holes, the effectiveness is higher for a higher coolant temperature than that for a lower coolant temperature when the coolant to mainstream mass flow ratio is 5% or more. For a fixed coolant temperature, the effectiveness passes through a minima on the suction side of shower-head holes as the coolant to mainstream mass flow, ratio increases, while on the pressure side of shower-head holes, the effectiveness decreases with increase in coolant mass flow due to coolant jet lift-off. In all cases, the adiabatic effectiveness is highly three-dimensional.

  2. Experimental and Analytical Investigation of the Coolant Flow Characteristics in Cooled Turbine Airfoils

    NASA Technical Reports Server (NTRS)

    Damerow, W. P.; Murtaugh, J. P.; Burggraf, F.

    1972-01-01

    The flow characteristics of turbine airfoil cooling system components were experimentally investigated. Flow models representative of leading edge impingement, impingement with crossflow (midchord cooling), pin fins, feeder supply tube, and a composite model of a complete airfoil flow system were tested. Test conditions were set by varying pressure level to cover the Mach number and Reynolds number range of interest in advanced turbine applications. Selected geometrical variations were studied on each component model to determine these effects. Results of these tests were correlated and compared with data available in the literature. Orifice flow was correlated in terms of discharge coefficients. For the leading edge model this was found to be a weak function of hole Mach number and orifice-to-impinged wall spacing. In the impingement with crossflow tests, the discharge coefficient was found to be constant and thus independent of orifice Mach number, Reynolds number, crossflow rate, and impingement geometry. Crossflow channel pressure drop showed reasonable agreement with a simple one-dimensional momentum balance. Feeder tube orifice discharge coefficients correlated as a function of orifice Mach number and the ratio of the orifice-to-approach velocity heads. Pin fin data was correlated in terms of equivalent friction factor, which was found to be a function of Reynolds number and pin spacing but independent of pin height in the range tested.

  3. Hot flow anomaly formation and evolution: Cluster observations

    NASA Astrophysics Data System (ADS)

    Wang, Shan; Zong, Qiugang; Zhang, Hui

    2013-07-01

    In this study, we have examined the formation and evolution of 513 hot flow anomalies (HFAs) from 2003 to 2009 observed by the Cluster spacecraft. Our results show that an original upstream discontinuity in the vicinity of an HFAs and/or at least one side of the HFA with the convective electric field pointing toward the discontinuity may help an HFA growing, but it is not a necessary condition to generate an HFA. It is shown that a significant part of the thermal energy inside HFAs is converted from the kinetic energy of the solar wind, although additional heating process(es) is required to heat the plasma inside an HFA. In order to learn the evolution of an HFA, we have examined the electron spectrum and ion velocity distribution function (VDF) inside young and mature HFAs. It is found that the particle spectra are good indicators of a young or mature HFA. Inside young HFAs, electron spectra can be fitted by a single drift-κ distribution, while inside mature HFAs it can be fitted by the combination of a drift-Maxwellian distribution with the peak energy below ˜10 eV and a heated electron distribution. On the other hand, ion VDF inside mature HFAs shows a single distribution, whereas the VDF inside young HFAs shows two clear ion populations—one original solar wind and a reflected ion population. It is found that the reflected ion population inside young HFAs can be scattered to more than 180° in the Vpara-Vperp1 plane, where Vperp1 is in the V-B plane but perpendicular to B, which is similar to the foreshock distribution. This indicates that the reflected ion population could be diffusive from all directions rather than the unidirectional beam when an HFA is forming.

  4. Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

    PubMed Central

    2011-01-01

    This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration. PMID:21827644

  5. Compact counter-flow cooling system with subcooled gravity-fed circulating liquid nitrogen

    NASA Astrophysics Data System (ADS)

    Ivanov, Yu.; Radovinsky, A.; Zhukovsky, A.; Sasaki, A.; Watanabe, H.; Kawahara, T.; Hamabe, M.; Yamaguchi, S.

    2010-11-01

    A liquid nitrogen (LN2) is usually used to keep the high-temperature superconducting (HTS) cable low temperature. A pump is utilized to circulate LN2 inside the cryopipes. In order to minimize heat leakage, a thermal siphon circulation scheme can be realized instead. Here, we discuss the effectiveness of thermal siphon with counter-flow circulation loop composed of cryogen flow channel and inner cable channel. The main feature of the system is the existence of essential parasitic heat exchange between upwards and downwards flows. Feasibility of the proposed scheme for cable up to 500 m in length has been investigated numerically. Calculated profiles of temperature and pressure show small differences of T and p in the inner and the outer flows at the same elevation, which allows not worrying about mechanical stability of the cable. In the case under consideration the thermal insulating properties of a conventional electrical insulating material (polypropylene laminated paper, PPLP) appear to be sufficient. Two interesting effects were disclosed due to analysis of subcooling of LN2. In case of highly inclined siphon subcooling causes significant increase of temperature maximum that can breakup of superconductivity. In case of slightly inclined siphon high heat flux from outer flow to inner flow causes condensation of nitrogen gas in outer channel. It leads to circulation loss. Results of numerical analyses indicate that counter-flow thermosiphon cooling system is a promising way to increase performance of short-length power transmission (PT) lines, but conventional subcooling technique should be applied carefully.

  6. AN HST/WFC3-UVIS VIEW OF THE STARBURST IN THE COOL CORE OF THE PHOENIX CLUSTER

    SciTech Connect

    McDonald, Michael; Bautz, Marshall W.; Benson, Bradford; Veilleux, Sylvain; Reichardt, Christian L.

    2013-03-10

    We present Hubble Space Telescope Wide Field Camera 3 observations of the core of the Phoenix cluster (SPT-CLJ2344-4243) in five broadband filters spanning rest-frame 1000-5500 A. These observations reveal complex, filamentary blue emission, extending for >40 kpc from the brightest cluster galaxy. We observe an underlying, diffuse population of old stars, following an r {sup 1/4} distribution, confirming that this system is somewhat relaxed. The spectral energy distribution in the inner part of the galaxy, as well as along the extended filaments, is a smooth continuum and is consistent with that of a star-forming galaxy, suggesting that the extended, filamentary emission is not due to the central active galactic nucleus, either from a large-scale ionized outflow or scattered polarized UV emission, but rather a massive population of young stars. We estimate an extinction-corrected star formation rate of 798 {+-} 42 M{sub Sun} yr{sup -1}, consistent with our earlier work based on low spatial resolution ultraviolet, optical, and infrared imaging. The lack of tidal features and multiple bulges, combine with the need for an exceptionally massive (>10{sup 11} M{sub Sun }) cold gas reservoir, suggest that this star formation is not the result of a merger of gas-rich galaxies. Instead, we propose that the high X-ray cooling rate of {approx}2700 M{sub Sun} yr{sup -1} is the origin of the cold gas reservoir. The combination of such a high cooling rate and the relatively weak radio source in the cluster core suggests that feedback has been unable to halt cooling in this system, leading to this tremendous burst of star formation.

  7. Computer program for generating input for analysis of impingement-cooled, axial-flow turbine blade

    NASA Astrophysics Data System (ADS)

    Rosenbaum, D.

    1980-01-01

    A computer program, TACTGRID, was developed to generate the geometrical input for the TACTI program, a program that calculates transient and steady state temperatures, pressures, and cooling flows in an impingement cooled turbine blade. Using spline curves, the TACTGRID program constructs the blade internal geometry from the previously designed external blade surface and newly selected wall and channel thicknesses. The TACTGRID program generates the TACTI calculational grid, calculates arc length between grid points required by TACTI as input, and prepares the namelist input data set used by TACTI for the blade geometry. In addition, TACTGRID produces a scaled computer plot of each blade slice, detailing the grid and calculational stations, and thus eliminates the need for intermediate drafting.

  8. Numerical investigation of transient heat transfer to hydromagnetic channel flow with radiative heat and convective cooling

    NASA Astrophysics Data System (ADS)

    Makinde, O. D.; Chinyoka, T.

    2010-12-01

    This present study consists of a numerical investigation of transient heat transfer in channel flow of an electrically conducting variable viscosity Boussinesq fluid in the presence of a magnetic field and thermal radiation. The temperature dependent nature of viscosity is assumed to follow an exponentially model and the system exchanges heat with the ambient following Newton's law of cooling. The governing nonlinear equations of momentum and energy transport are solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, fluid temperature, skin friction and heat transfer rate for various parametric values. Our results reveal that combined effect of thermal radiation, magnetic field, viscosity variation and convective cooling have significant impact in controlling the rate of heat transfer in the boundary layer region.

  9. Flow visualization of discrete hole film cooling for gas turbine applications

    NASA Technical Reports Server (NTRS)

    Colladay, R. S.; Russell, L. M.

    1975-01-01

    Film injection from discrete holes in a three row staggered array with 5-diameter spacing is studied. The boundary layer thickness-to-hole diameter ratio and Reynolds number are typical of gas turbine film cooling applications. Two different injection locations are studied to evaluate the effect of boundary layer thickness on film penetration and mixing. Detailed streaklines showing the turbulent motion of the injected air are obtained by photographing neutrally buoyant helium filled soap bubbles which follow the flow field. The bubble streaklines passing downstream injection locations are clearly identifiable and can be traced back to their origin. Visualization of surface temperature patterns obtained from infrared photographs of a similar film cooled surface are also included.

  10. Development of a Water Based, Critical Flow, Non-Vapor Compression cooling Cycle

    SciTech Connect

    Hosni, Mohammad H.

    2014-03-30

    Expansion of a high-pressure liquid refrigerant through the use of a thermostatic expansion valve or other device is commonplace in vapor-compression cycles to regulate the quality and flow rate of the refrigerant entering the evaporator. In vapor-compression systems, as the condensed refrigerant undergoes this expansion, its pressure and temperature drop, and part of the liquid evaporates. We (researchers at Kansas State University) are developing a cooling cycle that instead pumps a high-pressure refrigerant through a supersonic converging-diverging nozzle. As the liquid refrigerant passes through the nozzle, its velocity reaches supersonic (or critical-flow) conditions, substantially decreasing the refrigerant’s pressure. This sharp pressure change vaporizes some of the refrigerant and absorbs heat from the surrounding conditions during this phase change. Due to the design of the nozzle, a shockwave trips the supersonic two-phase refrigerant back to the starting conditions, condensing the remaining vapor. The critical-flow refrigeration cycle would provide space cooling, similar to a chiller, by running a secondary fluid such as water or glycol over one or more nozzles. Rather than utilizing a compressor to raise the pressure of the refrigerant, as in a vapor-cycle system, the critical-flow cycle utilizes a high-pressure pump to drive refrigerant liquid through the cooling cycle. Additionally, the design of the nozzle can be tailored for a given refrigerant, such that environmentally benign substances can act as the working fluid. This refrigeration cycle is still in early-stage development with prototype development several years away. The complex multi-phase flow at supersonic conditions presents numerous challenges to fully understanding and modeling the cycle. With the support of DOE and venture-capital investors, initial research was conducted at PAX Streamline, and later, at Caitin. We (researchers at Kansas State University) have continued development

  11. Bolometric correction and spectral energy distribution of cool stars in Galactic clusters

    NASA Astrophysics Data System (ADS)

    Buzzoni, A.; Patelli, L.; Bellazzini, M.; Pecci, F. Fusi; Oliva, E.

    2010-04-01

    We have investigated the relevant trend of the bolometric correction (BC) at the cool-temperature regime of red giant stars and its possible dependence on stellar metallicity. Our analysis relies on a wide sample of optical-infrared spectroscopic observations, along the 3500 Å ==> 2.5μm wavelength range, for a grid of 92 red giant stars in five (three globular + two open) Galactic clusters, along the full metallicity range covered by the bulk of the stars, -2.2 <= [Fe/H] <= +0.4. Synthetic BVRCIC JHK photometry from the derived spectral energy distributions allowed us to obtain robust temperature (Teff) estimates for each star, within +/-100K or less. According to the appropriate temperature estimate, blackbody extrapolation of the observed spectral energy distribution allowed us to assess the unsampled flux beyond the wavelength limits of our survey. For the bulk of our red giants, this fraction amounted to 15 per cent of the total bolometric luminosity, a figure that raises up to 30 per cent for the coolest targets (Teff <~ 3500K). Overall, we obtain stellar Mbol values with an internal accuracy of a few percentages. Even neglecting any correction for lost luminosity etc., we would be overestimating Mbol by <~0.3mag, in the worst cases. Making use of our new data base, we provide a set of fitting functions for the V and K BC versus Teff and versus (B - V) and (V - K) broad-band colours, valid over the interval 3300 <= Teff <= 5000K, especially suited for red giants. The analysis of the BCV and BCK estimates along the wide range of metallicity spanned by our stellar sample shows no evident drift with [Fe/H]. Things may be different for the B-band correction, where the blanketing effects are more and more severe. A drift of Δ(B - V) versus [Fe/H] is in fact clearly evident from our data, with metal-poor stars displaying a `bluer' (B - V) with respect to the metal-rich sample, for fixed Teff. Our empirical bolometric corrections are in good overall agreement with

  12. Experimental and Numerical Investigations of Effects of Flow Control Devices Upon Flat-Plate Film Cooling Performance.

    PubMed

    Kawabata, Hirokazu; Funazaki, Ken-Ichi; Nakata, Ryota; Takahashi, Daichi

    2014-06-01

    This study deals with the experimental and numerical studies of the effect of flow control devices (FCDs) on the film cooling performance of a circular cooling hole on a flat plate. Two types of FCDs with different heights are examined in this study, where each of them is mounted to the flat plate upstream of the cooling hole by changing its lateral position with respect to the hole centerline. In order to measure the film effectiveness as well as heat transfer downstream of the cooling hole with upstream FCD, a transient method using a high-resolution infrared camera is adopted. The velocity field downstream of the cooling hole is captured by 3D laser Doppler velocimeter (LDV). Furthermore, the aerodynamic loss associated with the cooling hole with/without FCD is measured by a total pressure probe rake. The experiments are carried out at blowing ratios ranging from 0.5 to 1.0. In addition, numerical simulations are also made to have a better understanding of the flow field. LES approach is employed to solve the flow field and visualize the vortex structure around the cooling hole with FCD. When a taller FCD is mounted to the plate, the film effectiveness tends to increase due to the vortex structure generated by the FCD. As FCD is laterally shifted from the centerline, the film effectiveness increases, while the lift-off of cooling air is also promoted when FCD is put on the center line. PMID:25278646

  13. Coarse Grid Modeling of Turbine Film Cooling Flows Using Volumetric Source Terms

    NASA Technical Reports Server (NTRS)

    Heidmann, James D.; Hunter, Scott D.

    2001-01-01

    The recent trend in numerical modeling of turbine film cooling flows has been toward higher fidelity grids and more complex geometries. This trend has been enabled by the rapid increase in computing power available to researchers. However, the turbine design community requires fast turnaround time in its design computations, rendering these comprehensive simulations ineffective in the design cycle. The present study describes a methodology for implementing a volumetric source term distribution in a coarse grid calculation that can model the small-scale and three-dimensional effects present in turbine film cooling flows. This model could be implemented in turbine design codes or in multistage turbomachinery codes such as APNASA, where the computational grid size may be larger than the film hole size. Detailed computations of a single row of 35 deg round holes on a flat plate have been obtained for blowing ratios of 0.5, 0.8, and 1.0, and density ratios of 1.0 and 2.0 using a multiblock grid system to resolve the flows on both sides of the plate as well as inside the hole itself. These detailed flow fields were spatially averaged to generate a field of volumetric source terms for each conservative flow variable. Solutions were also obtained using three coarse grids having streamwise and spanwise grid spacings of 3d, 1d, and d/3. These coarse grid solutions used the integrated hole exit mass, momentum, energy, and turbulence quantities from the detailed solutions as volumetric source terms. It is shown that a uniform source term addition over a distance from the wall on the order of the hole diameter is able to predict adiabatic film effectiveness better than a near-wall source term model, while strictly enforcing correct values of integrated boundary layer quantities.

  14. Streakline flow visualization of discrete-hole film cooling with normal, slanted, and compound angle injection

    NASA Technical Reports Server (NTRS)

    Colladay, R. S.; Russell, L. M.

    1976-01-01

    Film injection from discrete holes in a three-row, staggered array with five-diameter spacing was studied for three hole angles: (1) normal, (2) slanted 30 deg to the surface in the direction of the main stream, and (3) slanted 30 deg to the surface and 45 deg laterally to the main stream. The ratio of the boundary layer thickness-to-hole diameter and Reynolds number were typical of gas-turbine film-cooling applications. Detailed streaklines showing the turbulent motion of the injected air were obtained by photographing very small neutrally buoyant, helium-filled soap bubbles which follow the flow field.

  15. OPTICAL SPECTROSCOPY OF H{alpha} FILAMENTS IN COOL CORE CLUSTERS: KINEMATICS, REDDENING, AND SOURCES OF IONIZATION

    SciTech Connect

    McDonald, Michael; Veilleux, Sylvain; Rupke, David S. N. E-mail: veilleux@astro.umd.edu

    2012-02-20

    We have obtained deep, high spatial and spectral resolution, long-slit spectra of the H{alpha} nebulae in the cool cores of nine galaxy clusters. This sample provides a wealth of information on the ionization state, kinematics, and reddening of the warm gas in the cool cores of galaxy clusters. We find evidence for only small amounts of reddening in the extended, line-emitting filaments, with the majority of filaments having E(B - V) < 0.2. We find, in agreement with previous works, that the optical emission in cool core clusters has elevated low-ionization line ratios. The combination of [O III]/H{beta}, [N II]/H{alpha}, [S II]/H{alpha}, and [O I]/H{alpha} allow us to rule out collisional ionization by cosmic rays, thermal conduction, and photoionization by intracluster medium (ICM) X-rays and active galactic nuclei as strong contributors to the ionization in the bulk of the optical line-emitting gas in both the nuclei and filaments. The data are adequately described by a composite model of slow shocks and star formation. This model is further supported by an observed correlation between the line widths and low-ionization line ratios which becomes stronger in systems with more modest star formation activity based on far-ultraviolet observations. We find that the more extended, narrow filaments tend to have shallower velocity gradients and narrower line widths than the compact filamentary complexes. We confirm that the widths of the emission lines decrease with radius, from FWHM {approx}600 km s{sup -1} in the nuclei to FWHM {approx}100 km s{sup -1} in the most extended filaments. The variation of line width with radius is vastly different than what is measured from stellar absorption lines in a typical giant elliptical galaxy, suggesting that the velocity width of the warm gas may in fact be linked to ICM turbulence and, thus, may provide a glimpse into the amount of turbulence in cool cores. In the central regions (r < 10 kpc) of several systems the warm gas

  16. Effect of solar radiation on the performance of cross flow wet cooling tower in hot climate of Iran

    NASA Astrophysics Data System (ADS)

    Banooni, Salem; Chitsazan, Ali

    2016-11-01

    In some cities such as Ahvaz-Iran, the solar radiation is very high and the annual-mean-daily of the global solar radiation is about 17.33 MJ m2 d-1. Solar radiation as an external heat source seems to affect the thermal performance of the cooling towers. Usually, in modeling cooling tower, the effects of solar radiation are ignored. To investigate the effect of sunshade on the performance and modeling of the cooling tower, the experiments were conducted in two different states, cooling towers with and without sunshade. In this study, the Merkel's approach and finite difference technique are used to predict the thermal behavior of cross flow wet cooling tower without sunshade and the results are compared with the data obtained from the cooling towers with and without sunshade. Results showed that the sunshade is very efficient and it reduced the outlet water temperature, the approach and the water exergy of the cooling tower up to 1.2 °C, 15 and 1.1 %, respectively and increased the range and the efficiency of the cooling tower up to 29 and 37 %, respectively. Also, the sunshade decreased the error between the experimental data of the cooling tower with sunshade and the modeling results of the cooling tower without sunshade 1.85 % in average.

  17. Effect of solar radiation on the performance of cross flow wet cooling tower in hot climate of Iran

    NASA Astrophysics Data System (ADS)

    Banooni, Salem; Chitsazan, Ali

    2016-01-01

    In some cities such as Ahvaz-Iran, the solar radiation is very high and the annual-mean-daily of the global solar radiation is about 17.33 MJ m2 d-1. Solar radiation as an external heat source seems to affect the thermal performance of the cooling towers. Usually, in modeling cooling tower, the effects of solar radiation are ignored. To investigate the effect of sunshade on the performance and modeling of the cooling tower, the experiments were conducted in two different states, cooling towers with and without sunshade. In this study, the Merkel's approach and finite difference technique are used to predict the thermal behavior of cross flow wet cooling tower without sunshade and the results are compared with the data obtained from the cooling towers with and without sunshade. Results showed that the sunshade is very efficient and it reduced the outlet water temperature, the approach and the water exergy of the cooling tower up to 1.2 °C, 15 and 1.1 %, respectively and increased the range and the efficiency of the cooling tower up to 29 and 37 %, respectively. Also, the sunshade decreased the error between the experimental data of the cooling tower with sunshade and the modeling results of the cooling tower without sunshade 1.85 % in average.

  18. Significance of flow clustering and sequencing on sediment transport: 1D sediment transport modelling

    NASA Astrophysics Data System (ADS)

    Hassan, Kazi; Allen, Deonie; Haynes, Heather

    2016-04-01

    This paper considers 1D hydraulic model data on the effect of high flow clusters and sequencing on sediment transport. Using observed flow gauge data from the River Caldew, England, a novel stochastic modelling approach was developed in order to create alternative 50 year flow sequences. Whilst the observed probability density of gauge data was preserved in all sequences, the order in which those flows occurred was varied using the output from a Hidden Markov Model (HMM) with generalised Pareto distribution (GP). In total, one hundred 50 year synthetic flow series were generated and used as the inflow boundary conditions for individual flow series model runs using the 1D sediment transport model HEC-RAS. The model routed graded sediment through the case study river reach to define the long-term morphological changes. Comparison of individual simulations provided a detailed understanding of the sensitivity of channel capacity to flow sequence. Specifically, each 50 year synthetic flow sequence was analysed using a 3-month, 6-month or 12-month rolling window approach and classified for clusters in peak discharge. As a cluster is described as a temporal grouping of flow events above a specified threshold, the threshold condition used herein is considered as a morphologically active channel forming discharge event. Thus, clusters were identified for peak discharges in excess of 10%, 20%, 50%, 100% and 150% of the 1 year Return Period (RP) event. The window of above-peak flows also required cluster definition and was tested for timeframes 1, 2, 10 and 30 days. Subsequently, clusters could be described in terms of the number of events, maximum peak flow discharge, cumulative flow discharge and skewness (i.e. a description of the flow sequence). The model output for each cluster was analysed for the cumulative flow volume and cumulative sediment transport (mass). This was then compared to the total sediment transport of a single flow event of equivalent flow volume

  19. A combined experiment/computational study of flow in turbine blade cooling passage

    NASA Astrophysics Data System (ADS)

    Tse, D. G. N.; Kreskovsky, J. P.; Shamroth, S. J.; McGrath, D. B.

    1994-05-01

    Laser velocimetry was utilized to map the velocity field in a serpentine turbine blade cooling passage at Reynolds and Rotation numbers of up to 25.000 and 0.48. These results were used to assess the combined influence of passage curvature and Coriolis force on the secondary velocity field generated. A Navier-Stokes code (NASTAR) was validated against incompressible test data and then used to simulate the effect of buoyancy. The measurements show a net convection from the low pressure surface to high pressure surface. The interaction of the secondary flows induced by the turns and rotation produces swirl at the turns, which persisted beyond 2 hydraulic diameters downstream of the turns. The incompressible flow field predictions agree well with the measured velocities. With radially outward flow, the buoyancy force causes a further increase in velocity on the high pressure surface and a reduction on the low pressure surface. The results were analyzed in relation to the heat transfer measurements of Wagner et al. (1991). Predicted heat transfer is enhanced on the high pressure surfaces and in turns. The incompressible flow simulation underpredicts heat transfer in these locations. Improvements observed in compressible flow simulation indicate that the buoyancy force may be important.

  20. A Combined Experimental/Computational Study of Flow in Turbine Blade Cooling Passage

    NASA Technical Reports Server (NTRS)

    Tse, D. G. N.; Kreskovsky, J. P.; Shamroth, S. J.; Mcgrath, D. B.

    1994-01-01

    Laser velocimetry was utilized to map the velocity field in a serpentine turbine blade cooling passage at Reynolds and Rotation numbers of up to 25.000 and 0.48. These results were used to assess the combined influence of passage curvature and Coriolis force on the secondary velocity field generated. A Navier-Stokes code (NASTAR) was validated against incompressible test data and then used to simulate the effect of buoyancy. The measurements show a net convection from the low pressure surface to high pressure surface. The interaction of the secondary flows induced by the turns and rotation produces swirl at the turns, which persisted beyond 2 hydraulic diameters downstream of the turns. The incompressible flow field predictions agree well with the measured velocities. With radially outward flow, the buoyancy force causes a further increase in velocity on the high pressure surface and a reduction on the low pressure surface. The results were analyzed in relation to the heat transfer measurements of Wagner et al. (1991). Predicted heat transfer is enhanced on the high pressure surfaces and in turns. The incompressible flow simulation underpredicts heat transfer in these locations. Improvements observed in compressible flow simulation indicate that the buoyancy force may be important.

  1. Peristaltic flow of a reactive viscous fluid through a porous saturated channel and convective cooling conditions

    NASA Astrophysics Data System (ADS)

    Asghar, S.; Hussain, Q.; Hayat, T.; Alsaedi, A.

    2015-07-01

    This article addresses the heat transfer in a peristaltic flow of a reactive combustible viscous fluid through a porous saturated medium. The flow here is induced because of travelling waves along the channel walls. It is assumed that exothermic chemical reactions take place within the channel under the Arrhenius kinetics and the convective heat exchange with the ambient medium at the surfaces of the channel walls follows Newton's law of cooling. The analysis is carried out in the presence of viscous dissipation and without consumption of the material. The governing equations are formulated by employing the long-wavelength approximation. Closed-form solutions for the stream function, axial velocity, and axial pressure gradient are obtained. It is found that the temperature decreases at high Biot numbers, and the Nusselt number increases with increasing reaction parameter. The Biot number and reaction parameter produce the opposite effects on the Nusselt number.

  2. Streakline flow visualization of discrete hole film cooling with holes inclined 30 deg to surface

    NASA Technical Reports Server (NTRS)

    Colladay, R. S.; Russell, L. M.; Lane, J. M.

    1976-01-01

    Film injection from three rows of discrete holes angled 30 deg to the surface in line with mainstream flow and spaced 5 diameters apart in a staggered array was visualized by using helium bubbles as tracer particles. Both the main stream and the film injectant were ambient air. Detailed streaklines showing the turbulent motion of the film mixing with the main stream were obtained by photographing small, neutrally buoyant helium-filled soap bubbles which followed the flow field. The ratio of boundary layer thickness to hole diameter and the Reynolds number were typical of gas turbine film cooling applications. The results showed the behavior of the film and its interaction with the main stream for a range of blowing rates and two initial boundary layer thicknesses.

  3. Channel flow modeling of impingement cooling of a rotating turbine blade

    NASA Technical Reports Server (NTRS)

    Koo, J. J.

    1984-01-01

    Local heat transfer distributions in impingement cooling have been measured by Kreatsoulas and Prieser for a range of conditions which model those in actual turbine blades, including the effects of rotation. These data were reported as local Nusselt numbers, but referred to coolant supply conditions. By means of a channel flow modeling of the flow in the supply and impingement passages, the same data are here presented in terms of local Nusselt number distributions such as are used in design. The results in this form are compared to the nonrotating impingement results of Chupp and to the rotating but nonimpingement results of Morris. Rotation reduces the mean Nusselt numbers from these found by Chupp by about 30 percent, and introduces important radial variations which are sensitive to rotation and to leading edge stagger angle.

  4. Long Hole Film Cooling Dataset for CFD Development - Flow and Film Effectiveness

    NASA Technical Reports Server (NTRS)

    Shyam, Vikram; Poinsatte, Phillip; Thurman, Douglas; Ameri, Ali

    2014-01-01

    An experiment investigating flow and heat transfer of long (length to diameter ratio of 18) cylindrical film cooling holes has been completed. In this paper, the thermal field in the flow and on the surface of the film cooled flat plate is presented for nominal freestream turbulence intensities of 1.5 and 8 percent. The holes are inclined at 30 deg above the downstream direction, injecting chilled air of density ratio 1.0 onto the surface of a flat plate. The diameter of the hole is 0.75 in. (approx. 0.02 m) with center to center spacing (pitch) of 3 hole diameters. Coolant was injected into the mainstream flow at nominal blowing ratios of 0.5, 1.0, 1.5, and 2.0. The Reynolds number of the freestream was approximately 11,000 based on hole diameter. Thermocouple surveys were used to characterize the thermal field. Infrared thermography was used to determine the adiabatic film effectiveness on the plate. Hotwire anemometry was used to provide flowfield physics and turbulence measurements. The results are compared to existing data in the literature. The aim of this work is to produce a benchmark dataset for Computational Fluid Dynamics (CFD) development to eliminate the effects of hole length to diameter ratio and to improve resolution in the near-hole region. In this report, a Time Filtered Navier Stokes (TFNS), also known as Partially Resolved Navier Stokes (PRNS), method that was implemented in the Glenn-HT code is used to model coolant-mainstream interaction. This method is a high fidelity unsteady method that aims to represent large scale flow features and mixing more accurately.

  5. Mapping the dark matter in the NGC 5044 group with ROSAT: Evidence for a nearly homogeneous cooling flow with a cooling wake

    NASA Technical Reports Server (NTRS)

    David, Laurence P.; Jones, Christine; Forman, William; Daines, Stuart

    1994-01-01

    The NGC 5044 group of galaxies was observed by the ROSAT Position Sensitive Proportional Counter (PSPC) for 30 ks during its reduced pointed phase (1991 July). Due to the relatively cool gas temperature in the group (kT = 0.98 +/- 0.02 keV) and the excellent photon statistics (65,000 net counts), we are able to determine precisely a number of fundamental properties of the group within 250 kpc of the central galaxy. In particular, we present model-independent measurements of the total gravitating mass, the temperature and abundance profiles of the gas, and the mass accretion rate. Between 60 and 250 kpc, the gas is nearly isothermal with T varies as r(exp (-0.13 +/- 0.03)). The total gravitating mass of the group can be unambiguously determined from the observed density and temperature profiles of the gas using the equation of hydrostatic equilibrium. Within 250 kpc, the gravitating mass is 1.6 x 10(exp 13) solar mass, yielding a mass-to-light ratio of 130 solar mass/solar luminosity. The baryons (gas and stars) comprise 12% of the total mass within this radius. At small radii, the temperature clearly increases outward and attains a maximum value at 60 kpc. The positive temperature gradient in the center of the group confirms the existence of a cooling flow. The cooling flow region extends well beyond the temperature maximum with a cooling radius between 100 and 150 kpc. There are two distinct regions in the cooling flow separated by the temperature maximum. In the outer region, the gas is nearly isothermal with a unifor m Fe abundance of approximately 80% solar, the flow is nearly homogeneous with dot-M= 20 to 25 solar mass/year, the X-ray contours are spherically symmetric, and rho(sub gas) varies as r(exp -1.6). In the inner region, the temperature profile has a positive gradient, the mass accretion rate decreases rapidly inward, the gas density profile is steeper, and the X-ray image shows some substrucutre. NGC 5044 is offset from the centroid of the outer X

  6. Effect of Some Factors on Critical Condition of Ice Formation for Flowing Supercooled Organic Water Solution in Cooled Circular Tube

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Miyahara, Satoshi; Takeya, Kengo

    Supercooling characteristics of three kinds of organic water solutions (D-Sorbitol, Glycerol, Glucose) in a forced flow were investigated experimentally. The critical condition of ice nucleation in a cooled circular tube was examined for concentration of water solution and cooling temperature under various Reynolds numbers. It was found that the flow velocity and cooling temperature conditions in a laminar flow region. However, in a turbulent flow region, the critical degree of supercooling was influenced by the flow velocity and cooling temperature. As a result, non-dimensional correlation equations for the critical condition of ice formation were derived in the laminar and turbulent flow region as a function of some non-dimensional parameters. While the ice making efficiency of D-Sorbitol water solution was measured under various Reynolds numbers and cooling temperature conditions on the stable supercooling condition. The ice making efficiency of supercooled organic water solution was influenced by the degree of the supercooling based on the mixed organic water solution temperature at the outlet of the inner tube.

  7. A simple and highly stable free-flow electrophoresis device with thermoelectric cooling system.

    PubMed

    Yan, Jian; Guo, Cheng-Gang; Liu, Xiao-Ping; Kong, Fan-Zhi; Shen, Qiao-Yi; Yang, Cheng-Zhang; Li, Jun; Cao, Cheng-Xi; Jin, Xin-Qiao

    2013-12-20

    Complex assembly, inconvenient operations, poor control of Joule heating and leakage of solution are still fundamental issues greatly hindering application of free-flow electrophoresis (FFE) for preparative purpose in bio-separation. To address these issues, a novel FFE device was developed based on our previous work. Firstly, a new mechanical structure was designed for compact assembly of separation chamber, fast removal of air bubble, and good anti-leakage performance. Secondly, a highly efficient thermoelectric cooling system was used for dispersing Joule heating for the first time. The systemic experiments revealed the three merits: (i) 3min assembly without any liquid leakage, 80 times faster than pervious FFE device designed by us or commercial device (4h); (ii) 5s removing of air bubble in chamber, 1000-fold faster than a normal one (2h or more) and (iii) good control of Joule heating by the cooling system. These merits endowed the device high stable thermo- and hydro-dynamic flow for long-term separation even under high electric field of 63V/cm. Finally, the developed device was used for up to 8h continuous separation of 5mg/mL fuchsin acid and purification of three model proteins of phycocyanin, myoglobin and cytochrome C, demonstrating the applicability of FFE. The developed FFE device has evident significance to the studies on stem cell, cell or organelle proteomics, and protein complex as well as micro- or nano-particles. PMID:24246174

  8. A simple and highly stable free-flow electrophoresis device with thermoelectric cooling system.

    PubMed

    Yan, Jian; Guo, Cheng-Gang; Liu, Xiao-Ping; Kong, Fan-Zhi; Shen, Qiao-Yi; Yang, Cheng-Zhang; Li, Jun; Cao, Cheng-Xi; Jin, Xin-Qiao

    2013-12-20

    Complex assembly, inconvenient operations, poor control of Joule heating and leakage of solution are still fundamental issues greatly hindering application of free-flow electrophoresis (FFE) for preparative purpose in bio-separation. To address these issues, a novel FFE device was developed based on our previous work. Firstly, a new mechanical structure was designed for compact assembly of separation chamber, fast removal of air bubble, and good anti-leakage performance. Secondly, a highly efficient thermoelectric cooling system was used for dispersing Joule heating for the first time. The systemic experiments revealed the three merits: (i) 3min assembly without any liquid leakage, 80 times faster than pervious FFE device designed by us or commercial device (4h); (ii) 5s removing of air bubble in chamber, 1000-fold faster than a normal one (2h or more) and (iii) good control of Joule heating by the cooling system. These merits endowed the device high stable thermo- and hydro-dynamic flow for long-term separation even under high electric field of 63V/cm. Finally, the developed device was used for up to 8h continuous separation of 5mg/mL fuchsin acid and purification of three model proteins of phycocyanin, myoglobin and cytochrome C, demonstrating the applicability of FFE. The developed FFE device has evident significance to the studies on stem cell, cell or organelle proteomics, and protein complex as well as micro- or nano-particles.

  9. Wind tunnel experiments of cooling-tower plumes in the presence of cross flow

    NASA Astrophysics Data System (ADS)

    Andreopoulos, J.

    Measurements of velocity and temperature field and flow visualization results are reported for an ideal case of a cooling-tower plume in the presence of cross flow for various velocity ratios, densimetric Froude numbers, and Reynolds numbers. Coherent structures in the form of jet-like, wake-like or mushroom type of vortices have been observed. The type of the structures depends primarily on the velocity ratio. As the Reynolds number increases turbulent structures appear which carry vorticity of the same sign as the partner vortices in the low Reynolds number case. The measurements showed that there is a strong interaction between the bending over plume or jet and the wake of the cooling tower which is basically responsible for the downwash effect, which generally is quite strong at low velocity ratios and high Reynolds numbers. High turbulence intensities are produced on the wake of the tower for about 6 to 8 diameters. The plume is diluted faster as the velocity ratio and buoyancy increase.

  10. Simulation of hydrogen adsorption systems adopting the flow through cooling concept

    SciTech Connect

    Corgnale, Claudio; Hardy, Bruce; Chahine, Richard; Cossement, Daniel; Tamburello, David; Anton, Donald

    2014-10-13

    Hydrogen storage systems based on adsorbent materials have the potential of achieving the U.S. Department of Energy (DOE) targets, especially in terms of gravimetric capacity. This paper deals with analysis of adsorption storage systems adopting the flow through cooling concept. By this approach the feeding hydrogen provides the needed cold to maintain the tank at low temperatures. Two adsorption systems have been examined and modeled adopting the Dubinin-Astakhov model, to see their performance under selected operating conditions. A first case has been analyzed, modeling a storage tank filled with carbon based material (namely MaxSorb®) and comparing the numerical outcomes with the available experimental results for a 2.5 L tank. Under selected operating conditions (minimum inlet hydrogen temperature of approximately 100 K and maximum pressure on the order of 8.5 MPa) and adopting the flow through cooling concept the material shows a gravimetric capacity of about 5.7 %. A second case has been modeled, examining the same tank filled with metal organic framework material (MOF5®) under approximately the same conditions. The model shows that the latter material can achieve a (material) gravimetric capacity on the order of 11%, making the system potentially able to achieve the DOE 2017 target.

  11. Simulation of hydrogen adsorption systems adopting the flow through cooling concept

    DOE PAGES

    Corgnale, Claudio; Hardy, Bruce; Chahine, Richard; Cossement, Daniel; Tamburello, David; Anton, Donald

    2014-10-13

    Hydrogen storage systems based on adsorbent materials have the potential of achieving the U.S. Department of Energy (DOE) targets, especially in terms of gravimetric capacity. This paper deals with analysis of adsorption storage systems adopting the flow through cooling concept. By this approach the feeding hydrogen provides the needed cold to maintain the tank at low temperatures. Two adsorption systems have been examined and modeled adopting the Dubinin-Astakhov model, to see their performance under selected operating conditions. A first case has been analyzed, modeling a storage tank filled with carbon based material (namely MaxSorb®) and comparing the numerical outcomes withmore » the available experimental results for a 2.5 L tank. Under selected operating conditions (minimum inlet hydrogen temperature of approximately 100 K and maximum pressure on the order of 8.5 MPa) and adopting the flow through cooling concept the material shows a gravimetric capacity of about 5.7 %. A second case has been modeled, examining the same tank filled with metal organic framework material (MOF5®) under approximately the same conditions. The model shows that the latter material can achieve a (material) gravimetric capacity on the order of 11%, making the system potentially able to achieve the DOE 2017 target.« less

  12. Measurement of Turbulent Flow Phenomena for the Lower Plenum of a Prismatic Gas-Cooled Reactor

    SciTech Connect

    Hugh M. McIlroy Jr.; Donald M. McEligot; Robert J. Pink; Keith G. Condie; Glenn E. McCreery

    2007-09-01

    Mean velocity field and turbulence data are presented for flow phenomena in a lower plenum of a typical prismatic gas-cooled reactor (GCR), such as in a Very High Temperature Reactor (VHTR) concept. In preparation for design, safety analyses and licensing, research has begun on readying the computational tools that will be needed to predict the thermal-hydraulics behavior of the reactor design. Fluid dynamics experiments have been designed and built to develop benchmark databases for the assessment of computational fluid dynamics (CFD) codes and their turbulence models for a typical VHTR plenum geometry in the limiting case of negligible buoyancy and constant fluid properties. This experiment has been proposed as a “Standard Problem” for assessing advanced reactor (CFD) analysis tools. Present results concentrate on the region of the plenum near its far reflector wall (away from the outlet duct). The flow in the lower plenum can locally be considered as multiple jets into a confined cross flow - with obstructions. A model of the lower plenum has been fabricated and scaled to the geometric dimensions of the Next Generation Nuclear Plant (NGNP) Point Design. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to induce flow features somewhat comparable to those expected from the staggered parallel rows of posts in the reactor design. Posts, side walls and end walls are fabricated from clear, fused quartz to match the refractive-index of the working fluid so that optical techniques may be employed for the measurements. The experiments were conducted in the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Laboratory (INL). The benefit of the MIR technique is that it permits optical measurements to determine complex flow characteristics in passages and around objects to be obtained without locating a disturbing transducer in the flow field and without distortion of the optical paths. The

  13. Measurement of Flow Phenomena in a Lower Plenum Model of a Prismatic Gas-Cooled Reactor

    SciTech Connect

    Hugh M. McIlroy, Jr.; Donald M. McEligot; Robert J. Pink

    2008-05-01

    Mean-velocity-field and turbulence data are presented that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor (GCR) similar to a General Atomics Gas-Turbine-Modular Helium Reactor (GTMHR) design. The data were obtained in the Matched-Index-of-Refraction (MIR) facility at Idaho National Laboratory (INL) and are offered for assessing computational fluid dynamics (CFD) software. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. This paper reviews the experimental apparatus and procedures, presents a sample of the data set, and reviews the INL Standard Problem. Results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). The flow in the lower plenum consists of multiple jets injected into a confined cross flow - with obstructions. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to approximate flow scaled to that expected from the staggered parallel rows of posts in the reactor design. The model is fabricated from clear, fused quartz to match the refractive-index of the mineral oil working fluid so that optical techniques may be employed for the measurements. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages in and around objects to be obtained without locating intrusive transducers that will disturb the flow field and without distortion of the optical paths. An advantage of the INL system is its large size, leading to improved spatial and temporal resolution compared to similar facilities at smaller scales. A three-dimensional (3-D) Particle Image Velocimetry (PIV) system was used to collect the data. Inlet jet Reynolds numbers (based on the jet diameter and the time-mean average flow rate) are approximately 4,300 and 12

  14. Measurement of Turbulent Flow Phenomena for the Lower Plenum of a Prismatic Gas-Cooled Reactor

    SciTech Connect

    Hugh M. McIlroy, Jr.; Donald M. McEligot; Robert J. Pink

    2010-02-01

    Mean velocity field and turbulence data are presented that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor (GCR) similar to a General Atomics design (Gas-Turbine-Modular Helium Reactor). The datawere obtained in the Matched-Index-of-Refraction (MIR) facility at Idaho National Laboratory (INL) and are offered as a benchmark for assessing computational fluid dynamics (CFD) software. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. The primary objective of this paper is to document the experiment and present a sample of the data set that has been established for this standard problem. Present results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). The flowin the lower plenum consists of multiple jets injected into a confined crossflow—with obstructions. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to approximate flow scaled to that expected from the staggered parallel rows of posts in the reactor design. Posts, side walls and end walls are fabricated from clear, fused quartz to match the refractive index of the mineral oil working fluid so that optical techniques may be employed for the measurements. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages and around objects to be obtained without locating intrusive transducers that will disturb the flow field and without distortion of the optical paths. An advantage of the INL system is its large size, leading to improved spatial and temporal resolution compared to similar facilities at smaller scales. A three-dimensional (3D) particle image velocimetry (PIV) system was used to collect the data. Inlet-jet Reynolds numbers (based on the hydraulic diameter of the jet

  15. Flow visualization study in high aspect ratio cooling channels for rocket engines

    NASA Astrophysics Data System (ADS)

    Meyer, Michael L.; Giuliani, James E.

    1993-11-01

    The structural integrity of high pressure liquid propellant rocket engine thrust chambers is typically maintained through regenerative cooling. The coolant flows through passages formed either by constructing the chamber liner from tubes or by milling channels in a solid liner. Recently, Carlile and Quentmeyer showed life extending advantages (by lowering hot gas wall temperatures) of milling channels with larger height to width aspect ratios (AR is greater than 4) than the traditional, approximately square cross section, passages. Further, the total coolant pressure drop in the thrust chamber could also be reduced, resulting in lower turbomachinery power requirements. High aspect ratio cooling channels could offer many benefits to designers developing new high performance engines, such as the European Vulcain engine (which uses an aspect ratio up to 9). With platelet manufacturing technology, channel aspect ratios up to 15 could be formed offering potentially greater benefits. Some issues still exist with the high aspect ratio coolant channels. In a coolant passage of circular or square cross section, strong secondary vortices develop as the fluid passes through the curved throat region. These vortices mix the fluid and bring lower temperature coolant to the hot wall. Typically, the circulation enhances the heat transfer at the hot gas wall by about 40 percent over a straight channel. The effect that increasing channel aspect ratio has on the curvature heat transfer enhancement has not been sufficiently studied. If the increase in aspect ratio degrades the secondary flow, the fluid mixing will be reduced. Analysis has shown that reduced coolant mixing will result in significantly higher wall temperatures, due to thermal stratification in the coolant, thus decreasing the benefits of the high aspect ratio geometry. A better understanding of the fundamental flow phenomena in high aspect ratio channels with curvature is needed to fully evaluate the benefits of this

  16. Flow visualization study in high aspect ratio cooling channels for rocket engines

    NASA Technical Reports Server (NTRS)

    Meyer, Michael L.; Giuliani, James E.

    1993-01-01

    The structural integrity of high pressure liquid propellant rocket engine thrust chambers is typically maintained through regenerative cooling. The coolant flows through passages formed either by constructing the chamber liner from tubes or by milling channels in a solid liner. Recently, Carlile and Quentmeyer showed life extending advantages (by lowering hot gas wall temperatures) of milling channels with larger height to width aspect ratios (AR is greater than 4) than the traditional, approximately square cross section, passages. Further, the total coolant pressure drop in the thrust chamber could also be reduced, resulting in lower turbomachinery power requirements. High aspect ratio cooling channels could offer many benefits to designers developing new high performance engines, such as the European Vulcain engine (which uses an aspect ratio up to 9). With platelet manufacturing technology, channel aspect ratios up to 15 could be formed offering potentially greater benefits. Some issues still exist with the high aspect ratio coolant channels. In a coolant passage of circular or square cross section, strong secondary vortices develop as the fluid passes through the curved throat region. These vortices mix the fluid and bring lower temperature coolant to the hot wall. Typically, the circulation enhances the heat transfer at the hot gas wall by about 40 percent over a straight channel. The effect that increasing channel aspect ratio has on the curvature heat transfer enhancement has not been sufficiently studied. If the increase in aspect ratio degrades the secondary flow, the fluid mixing will be reduced. Analysis has shown that reduced coolant mixing will result in significantly higher wall temperatures, due to thermal stratification in the coolant, thus decreasing the benefits of the high aspect ratio geometry. A better understanding of the fundamental flow phenomena in high aspect ratio channels with curvature is needed to fully evaluate the benefits of this

  17. Effect of wall cooling on the stability of compressible subsonic flows over smooth humps and backward-facing steps

    NASA Technical Reports Server (NTRS)

    Al-Maaitah, Ayman A.; Nayfeh, Ali H.; Ragab, Saad A.

    1990-01-01

    The effect of wall cooling on the two-dimensional linear stability of subsonic flows over two-dimensional surface imperfections is investigated. Results are presented for flows over smooth humps and backward-facing steps with Mach numbers up to 0.8. The results show that, whereas cooling decreases the viscous instability, it increases the shear-layer instability and hence it increases the growth rates in the separation region. The coexistence of more than one instability mechanism makes a certain degree of wall cooling most effective. For the Mach numbers 0.5 and 0.8, the optimum wall temperatures are about 80 pct and 60 pct of the adiabatic wall temperature, respectively. Increasing the Mach number decreases the effectiveness of cooling slightly and reduces the optimum wall temperature.

  18. Effect of wall cooling on the stability of compressible subsonic flows over smooth humps and backward-facing steps

    NASA Technical Reports Server (NTRS)

    Al-Maaitah, Ayman A.; Nayfeh, Ali, H.; Ragab, Saad A.

    1989-01-01

    The effect of wall cooling on the two-dimensional linear stability of subsonic flows over two-dimensional surface imperfections is investigated. Results are presented for flows over smooth humps and backward-facing steps with Mach numbers up to 0.8. The results show that, whereas cooling decreases the viscous instability, it increases the shear-layer instability and hence it increases the growth rates in the separation region. The coexistence of more than one instability mechanism makes a certain degree of wall cooling most effective. For the Mach numbers 0.5 and 0.8, the optimum wall temperatures are about 80 pct and 60 pct of the adiabatic wall temperature, respectively. Increasing the Mach number decreases the effectiveness of cooling slightly and reduces the optimum wall temperature.

  19. Pressure-loss and flow coefficients inside a chordwise-finned, impingement, convection, and film air-cooled turbine vane

    NASA Technical Reports Server (NTRS)

    Hippensteele, S. A.

    1974-01-01

    Total-pressure-loss coefficients, flow discharge coefficients, and friction factors were determined experimentally for the various area and geometry changes and flow passages within an air-cooled turbine vane. The results are compared with those of others obtained on similar configurations, both actual and large models, of vane passages. The supply and exit air pressures were controlled and varied. The investigation was conducted with essentially ambient-temperature air and without external flow of air over the vane.

  20. Experimental results for film cooling in 2-D supersonic flow including coolant delivery pressure, geometry, and incident shock effects

    NASA Technical Reports Server (NTRS)

    Olsen, George C.; Nowak, Robert J.; Holden, Michael S.; Baker, N. R.

    1990-01-01

    An experimental program was conducted to establish some design parameters important to a supersonic film cooling system in a scramjet engine. A simple non-combusting two-dimensional flow configuration was used to isolate the film cooling phenomena. Parameters investigated include coolant delivery pressure, slot height and lip thickness, and incident shock location and strength. Design guidelines for use in engineering and trade studies are presented.

  1. Thermal and flow analysis of a convection air-cooled ceramic coated porous metal concept for turbine vanes

    NASA Technical Reports Server (NTRS)

    Stepka, F. S.

    1981-01-01

    The heat transfer and pressure drop through turbine vanes made of a sintered, porous metal coated with a thin layer of ceramic and convection cooled by spanwise flow of cooling air were analyzed. The analysis was made to determine the feasibility of using this concept for cooling very small turbines, primarily for short duration applications such as in missile engines. The analysis was made for gas conditions of approximately 10 and 40 atm and 1644 K and with turbine vanes made of felt type porous metals with relative densities from 0.2 to 0.6 and ceramic coating thicknesses of 0.076 to 0.254 mm.

  2. Flow visualization of discrete hole film cooling for gas turbine applications

    NASA Technical Reports Server (NTRS)

    Colladay, R. S.; Russell, L. M.

    1975-01-01

    Film injection from discrete holes in a three row staggered array with 5-diameter spacing is studied for three different hole angles: (1) normal, (2) slanted 30 deg to the surface in the direction of the mainstream, and (3) slanted 30 deg to the surface and 45 deg laterally to the mainstream. The boundary layer thickness-to-hole diameter ratio and Reynolds number are typical of gas turbine film cooling applications. Two different injection locations are studied to evaluate the effect of boundary layer thickness on film penetration and mixing. Detailed streaklines showing the turbulent motion of the injected air are obtained by photographing very small neutrally buoyant helium filled 'soap' bubbles which follow the flow field. Unlike smoke, which diffuses rapidly in the high turbulent mixing region associated with discrete hole blowing, the bubble streaklines passing downstream injection locations are clearly identifiable and can be traced back to their origin. Visualization of surface temperature patterns obtained from infrared photographs of a similar film cooled surface are also included.

  3. A study on fluid flow simulation in the cooling systems of machine tools

    NASA Astrophysics Data System (ADS)

    Olaru, I.

    2016-08-01

    This paper aims analysing the type of coolants and the correct choice of that as well as the dispensation in the processing area to control the temperature resulted from the cutting operation and the choose of the cutting operating modes. A high temperature in the working area over a certain amount can be harmful in terms of the quality of resulting surface and that could have some influences on the life of the cutting tool. The coolant chosen can be a combination of different cooling fluids in order to achieve a better cooling of the cutting area at the same time for carrying out the proper lubrication of that area. The fluid flow parameters of coolant can be influenced by the nature of the fluid or fluids used, the geometry of the nozzle used which generally has a convergent-divergent geometry in order to achieve a better dispersion of the coolant / lubricant on the area to be processed. A smaller amount of fluid is important in terms of the economy lubricant, because they are quite expensive. A minimal amount of lubricant may have a better impact on the environment and the health of the operator because the coolants in contact with overheated machined surface may develop a substantial amount of these gases that are not always beneficial to health.

  4. Measurement of Flow Phenomena in a Lower Plenum Model of a Prismatic Gas-Cooled Reactor

    SciTech Connect

    Hugh M. McIlroy, Jr.; Doanld M. McEligot; Robert J. Pink

    2010-02-01

    Mean-velocity-field and turbulence data are presented that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor (GCR) similar to a General Atomics Gas-Turbine-Modular Helium Reactor (GTMHR) design. The data were obtained in the Matched-Index-of-Refraction (MIR) facility at Idaho National Laboratory (INL) and are offered for assessing computational fluid dynamics (CFD) software. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. Results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). The flow in the lower plenum consists of multiple jets injected into a confined cross flow - with obstructions. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to approximate geometry scaled to that expected from the staggered parallel rows of posts in the reactor design. The model is fabricated from clear, fused quartz to match the refractive-index of the working fluid so that optical techniques may be employed for the measurements. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages in and around objects to be obtained without locating intrusive transducers that will disturb the flow field and without distortion of the optical paths. An advantage of the INL system is its large size, leading to improved spatial and temporal resolution compared to similar facilities at smaller scales. A three-dimensional (3-D) Particle Image Velocimetry (PIV) system was used to collect the data. Inlet jet Reynolds numbers (based on the jet diameter and the time-mean bulk velocity) are approximately 4,300 and 12,400. Uncertainty analyses and a discussion of the standard problem are included. The measurements reveal developing, non-uniform, turbulent flow in the

  5. Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

    NASA Astrophysics Data System (ADS)

    Afshari, Ebrahim; Ziaei-Rad, Masoud; Jahantigh, Nabi

    2016-06-01

    In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

  6. Modeling of skin cooling, blood flow, and optical properties in wounds created by electrical shock

    NASA Astrophysics Data System (ADS)

    Nguyen, Thu T. A.; Shupp, Jeffrey W.; Moffatt, Lauren T.; Jordan, Marion H.; Jeng, James C.; Ramella-Roman, Jessica C.

    2012-02-01

    High voltage electrical injuries may lead to irreversible tissue damage or even death. Research on tissue injury following high voltage shock is needed and may yield stage-appropriate therapy to reduce amputation rate. One of the mechanisms by which electricity damages tissue is through Joule heating, with subsequent protein denaturation. Previous studies have shown that blood flow had a significant effect on the cooling rate of heated subcutaneous tissue. To assess the thermal damage in tissue, this study focused on monitoring changes of temperature and optical properties of skin next to high voltage wounds. The burns were created between left fore limb and right hind limb extremities of adult male Sprague-Dawley rats by a 1000VDC delivery shock system. A thermal camera was utilized to record temperature variation during the exposure. The experimental results were then validated using a thermal-electric finite element model (FEM).

  7. Unscrambling the Omlette: a New Bubble and Crystal Clustering Mechanism in Chaotically Mixed Magma Flows

    NASA Astrophysics Data System (ADS)

    Robertson, J.; Metcalfe, G.; Wang, S.; Barnes, S. J.

    2014-12-01

    The concentration of bubbles, crystals or droplets into small volumes of magma is a key trigger for many interesting magmatic processes. For example, gas slugs driving Strombolian eruptions form from the coalesence of exsolved bubbles within a volcanic conduit, while Ni-Cu-PGE magmatic sulfide deposits require a concentration of dense sulfide droplets from a large volume of magma to form a massive ore body. However the physical mechanism for this clustering remains unresolved - especially since small particles in active magma flows are expected to mostly track flow streamlines rather than clustering. We have uncovered a previously unreported clustering mechanism which is applicable to magmatic flows. This mechanism involves the interaction of particles with two kinds of chaotic flow structure: (a) high-strain regions within the well-mixed chaotic zones of the flow, and (b) unmixed islands of stability within the chaotic flow, known as Kolmogorov-Arnold-Moser (KAM) regions. The first figure shows the difference between chaotic and KAM regions in a chaotic laminar pipe flow. Trapping occurs when particles are scattered from high-strain regions in the chaotic zones and become trapped in the KAM regions, leading to a rapid concentration of particles relative to their original distribution (shown in the second series of figures). Using a combination of these analogue experiments and theoretical analysis we outline the conditions under which this clustering process can occur. We examine the onset of secondary density-related instabilities and the effects of increased particle-particle interaction within the clustered particles, and highlight the impact of particle clustering on the dynamics of magma ascent and emplacement.

  8. Jet-Cooled High Resolution Infrared Spectroscopy of Small Van Der Waals SF_6 Clusters

    NASA Astrophysics Data System (ADS)

    Asselin, Pierre; Boudon, Vincent; Potapov, Alexey; Bruel, Laurent; Gaveau, Marc-André; Mons, Michel

    2016-06-01

    Using a pulsed slit nozzle multipass absorption spectrometer with a tunable quantum cascade laser we investigated van der Waals clusters involving sulfur hexafluoride in the spectral range near the νb{3} stretching vibration. Different sized homo-complexes were generated in a planar supersonic expansion with typically 0,5 % SF_6 diluted in 6 bar He. Firstly, several rotationally resolved parallel and perpendicular bands of (SF_6)_2, at 934,0 and 956,1 wn (#1 structure) in agreement with Takami et al. but also one band at 933,6 wn (#2 structure) never observed previously, were analyzed in light of a recent theoretical study predicting three nearly isoenergetic isomers of D2d, C2h and C_2 symmetry for the dimer. Furthermore, some broader bands were detected around 938 and 964 wn and assigned to (SF_6)_3 and (SF_6)_4 clusters on the grounds of concentration effects and/or ab initio calculations. Lastly, with 0,5 % rare gas Rg (Rg = Ne, Ar, Kr and Xe) added to the SF_6:He gas mixture, a series of van der Waals (SF_6)_2-Rg hetero-trimers were observed, which display a remarkable linear dependence of the vibrational shift with the polarizability of the rare gas atom provided that the initial SF_6 dimer structure is #2 . In the same time no transitions belonging to the binary complexes SF_6-Rg were found near the νb{3} monomer band. This result suggests a complex thermodynamics within the pulsed supersonic expansion leading to the preponderance of (SF_6)_2-Rg clusters over SF_6-Rg binary systems. R. D. Urban and M. Takami, J. Chem. Phys. 103, 9132 (1995). T. Vazhappily, A. Marjolin and K. D. Jordan, J. Phys. Chem. B, DOI: 10.1021/acs.jpcb.5b09419 (2015).

  9. THE X-RAY SPECTRUM OF THE COOLING-FLOW QUASAR H1821+643: A MASSIVE BLACK HOLE FEEDING OFF THE INTRACLUSTER MEDIUM

    SciTech Connect

    Reynolds, Christopher S.; Lohfink, Anne M.; Babul, Arif; Fabian, Andrew C.; Russell, Helen R.; Walker, Stephen A.; Hlavacek-Larrondo, Julie

    2014-09-10

    We present a deep Suzaku observation of H1821+643, an extremely rare example of a powerful quasar hosted by the central massive galaxy of a rich cooling-core cluster of galaxies. Informed by previous Chandra studies of the cluster, we achieve a spectral separation of emission from the active galactic nucleus (AGN) and the intracluster medium (ICM). With a high degree of confidence, we identify the signatures of X-ray reflection/reprocessing by cold and slowly moving material in the AGN's immediate environment. The iron abundance of this matter is found to be significantly sub-solar (Z ≈ 0.4 Z {sub ☉}), an unusual finding for powerful AGN but in line with the idea that this quasar is feeding from the ICM via a Compton-induced cooling flow. We also find a subtle soft excess that can be described phenomenologically (with an additional blackbody component) or as ionized X-ray reflection from the inner regions of a high inclination (i ≈ 57°) accretion disk around a spinning (a > 0.4) black hole. We describe how the ionization state of the accretion disk can be used to constrain the Eddington fraction of the source. Applying these arguments to our spectrum implies an Eddington fraction of 0.25-0.5, with an associated black hole mass of 3--6×10{sup 9} M{sub ⊙}.

  10. Some Aspects of Forecasting Severe Thunderstorms during Cool-Season Return-Flow Episodes.

    NASA Astrophysics Data System (ADS)

    Weiss, Steven J.

    1992-08-01

    Historically, the Gulf of Mexico has been considered a primary source of water vapor that influences the weather for much of the United States east of the Rocky Mountains. Although severe thunderstorms and tornadoes occur most frequently during the spring and summer months, the periodic transport of Gulf moisture inland ahead of traveling baroclinic waves can result in significant severe-weather episodes during the cool season.To gain insight into the short-range skill in forecasting surface synoptic patterns associated with moisture return from the Gulf, operational numerical weather prediction models from the National Meteorological Center were examined. Sea level pressure fields from the Limited-Area Fine-Mesh Model (LFM), Nested Grid Model (NGM), and the aviation (AVN) run of the Global Spectral Model, valid 48 h after initial data time, were evaluated for three cool-season cases that preceded severe local storm outbreaks. The NGM and AVN provided useful guidance in forecasting the onset of return flow along the Gulf coast. There was a slight tendency for these models to be slightly slow in the development of return flow. In contrast the LFM typically overforecasts the occurrence of return flow and tends to `open the Gulf' from west to east too quickly.Although the low-level synoptic pattern may be forecast correctly, the overall prediction process is hampered by a data void over the Gulf. It is hypothesized that when the return-flow moisture is located over the Gulf, model forecasts of stability and the resultant operational severe local storm forecasts are less skillful compared to situations when the moisture has spread inland already. This hypothesis is tested by examining the performance of the initial second-day (day 2) severe thunderstorm outlook issued by the National Severe Storms Forecast Center during the Gulf of Mexico Experiment (GUFMEX) in early 1988.It has been found that characteristically different air masses were present along the Gulf coast

  11. Blood Flow Clustering and Applications in Virtual Stenting of Intracranial Aneurysms.

    PubMed

    Oeltze, Steffen; Lehmann, Dirk J; Kuhn, Alexander; Janiga, Gabor; Theisel, Holger; Preim, Bernhard

    2014-05-01

    Understanding the hemodynamics of blood flow in vascular pathologies such as intracranial aneurysms is essential for both their diagnosis and treatment. Computational fluid dynamics (CFD) simulations of blood flow based on patient-individual data are performed to better understand aneurysm initiation and progression and more recently, for predicting treatment success. In virtual stenting, a flow-diverting mesh tube (stent) is modeled inside the reconstructed vasculature and integrated in the simulation. We focus on steady-state simulation and the resulting complex multiparameter data. The blood flow pattern captured therein is assumed to be related to the success of stenting. It is often visualized by a dense and cluttered set of streamlines.We present a fully automatic approach for reducing visual clutter and exposing characteristic flow structures by clustering streamlines and computing cluster representatives. While individual clustering techniques have been applied before to streamlines in 3D flow fields, we contribute a general quantitative and a domain-specific qualitative evaluation of three state-of-the-art techniques. We show that clustering based on streamline geometry as well as on domain-specific streamline attributes contributes to comparing and evaluating different virtual stenting strategies. With our work, we aim at supporting CFD engineers and interventional neuroradiologists.

  12. Clustering and flow around a sphere moving into a grain cloud.

    PubMed

    Seguin, A; Lefebvre-Lepot, A; Faure, S; Gondret, P

    2016-06-01

    A bidimensional simulation of a sphere moving at constant velocity into a cloud of smaller spherical grains far from any boundaries and without gravity is presented with a non-smooth contact dynamics method. A dense granular "cluster" zone builds progressively around the moving sphere until a stationary regime appears with a constant upstream cluster size. The key point is that the upstream cluster size increases with the initial solid fraction [Formula: see text] but the cluster packing fraction takes an about constant value independent of [Formula: see text]. Although the upstream cluster size around the moving sphere diverges when [Formula: see text] approaches a critical value, the drag force exerted by the grains on the sphere does not. The detailed analysis of the local strain rate and local stress fields made in the non-parallel granular flow inside the cluster allows us to extract the local invariants of the two tensors: dilation rate, shear rate, pressure and shear stress. Despite different spatial variations of these invariants, the local friction coefficient μ appears to depend only on the local inertial number I as well as the local solid fraction, which means that a local rheology does exist in the present non-parallel flow. The key point is that the spatial variations of I inside the cluster do not depend on the sphere velocity and explore only a small range around the value one. PMID:27339702

  13. Experimental investigation of secondary flow vortices in a rod cluster

    NASA Astrophysics Data System (ADS)

    Vonka, V.; Hoornstra, J.; Boersma, P.

    1985-12-01

    Secondary flow vortices were measured in 2 regular subchannels of a triangularly arranged bare rod bundle with pitch-to-diameter ratio = 1.3 at Reynolds numbers Re = 60,000 and 175,000. A laser Doppler anemometer measured total time average velocity vectors in the central subchannels of a four rod bundle. Results show that half the momentum transport in the circumferential direction is due to the secondary flow vortex convection. In nonisothermal situations the secondary vortices contribute to heat transport in radial and circumferential directions. In radial direction, the contribution can improve the heat transfer coefficient and contribute to better economy of heat transfer installations. In circumferential direction, the contribution helps to smooth out circumferential temperature differences, improves the heat removal from heated surfaces thus decreasing the maximum surface temperature, and contributes to passive safety of heat transfer installations.

  14. Flow Quantification from 2D Phase Contrast MRI in Renal Arteries Using Clustering

    NASA Astrophysics Data System (ADS)

    Zöllner, Frank G.; Monnsen, Jan Ankar; Lundervold, Arvid; Rørvik, Jarle

    We present an approach based on clustering to segment renal arteries from 2D PC Cine MR images to measure blood velocity and flow. Such information are important in grading renal artery stenosis and support the decision on surgical interventions like percutan transluminal angioplasty. Results show that the renal arteries could be extracted automatically and the corresponding velocity profiles could be calculated. Furthermore, the clustering could detect possible phase wrap effects automatically as well as differences in the blood flow patterns within the vessel.

  15. Simulation of supercritical flows in rocket-motor engines: application to cooling channel and injection system

    NASA Astrophysics Data System (ADS)

    Ribert, G.; Taieb, D.; Petit, X.; Lartigue, G.; Domingo, P.

    2013-03-01

    To address physical modeling of supercritical multicomponent fluid flows, ideal-gas law must be changed to real-gas equation of state (EoS), thermodynamic and transport properties have to incorporate dense fluid corrections, and turbulence modeling has to be reconsidered compared to classical approaches. Real-gas thermodynamic is presently investigated with validation by NIST (National Institute of Standards and Technology) data. Two major issues of Liquid Rocket Engines (LRE) are also presented. The first one is the supercritical fluid flow inside small cooling channels. In a context of LRE, a strong heat flux coming from the combustion chamber (locally Φ ≈ 80 MW/m2) may lead to very steep density gradients close to the wall. These gradients have to be thermodynamically and numerically captured to properly reproduce in the simulation the mechanism of heat transfer from the wall to the fluid. This is done with a shock-capturing weighted essentially nonoscillatory (WENO) numerical discretization scheme. The second issue is a supercritical fluid injection following experimental conditions [1] in which a trans- or supercritical nitrogen is injected into warm nitrogen. The two-dimensional results show vortex structures with high fluid density detaching from the main jet and persisting in the low-speed region with low fluid density.

  16. 3-Dimensional numerical study of cooling performance of a heat sink with air-water flow through mini-channel

    NASA Astrophysics Data System (ADS)

    Majumder, Sambit; Majumder, Abhik; Bhaumik, Swapan

    2016-07-01

    The present microelectronics market demands devices with high power dissipation capabilities having enhanced cooling per unit area. The drive for miniaturizing the devices to even micro level dimensions is shooting up the applied heat flux on such devices, resulting in complexity in heat transfer and cooling management. In this paper, a method of CPU processor cooling is introduced where active and passive cooling techniques are incorporated simultaneously. A heat sink consisting of fins is designed, where water flows internally through the mini-channel fins and air flows externally. Three dimensional numerical simulations are performed for large set of Reynolds number in laminar region using finite volume method for both developing flows. The dimensions of mini-channel fins are varied for several aspect ratios such as 1, 1.33, 2 and 4. Constant temperature (T) boundary condition is applied at heat sink base. Channel fluid temperature, pressure drop are analyzed to obtain best cooling option in the present study. It has been observed that as the aspect ratio of the channel decreases Nusselt number decreases while pressure drop increases. However, Nusselt number increases with increase in Reynolds number.

  17. Vortex-generating coolant-flow-passage design for increased film-cooling effectiveness and surface coverage

    NASA Technical Reports Server (NTRS)

    Papell, S. S.

    1984-01-01

    The thermal film-cooling footprints observed by infrared imagery for three coolant-passage configurations embedded in adiabatic-test plates are discussed. The configurations included a standard round-hole cross section and two orientations of a vortex-generating flow passage. Both orientations showed up to factors of four increases in both film-cooling effectiveness and surface coverage over that obtained with the round coolant passage. The crossflow data covered a range of tunnel velocities from 15.5 to 45 m/sec with blowing rates from 0.20 to 2.05. A photographic streakline flow visualization technique supported the concept of the counterrotating apability of the flow passage design and gave visual credence to its role in inhibiting flow separation.

  18. The relationship between the formation of clusters containing tetrahedral molecules and the dynamic and thermodynamic anomalies of cooled TIP4P/2005 water

    NASA Astrophysics Data System (ADS)

    Van Sang, Le

    2016-07-01

    Molecular dynamics simulations have been used to cool the simple liquid TPI4P/2005 water at 350 K to 100 K. We find that structural changes of the system cause dynamic and thermodynamic anomalies. A strong increase in the number of tetrahedral oxygen atoms and combinations of these atoms lead to water's a phase transition from a simple liquid form into a supercooled one or ice at T I = 200 K. In the initial stage, small patches containing tetrahedral oxygen atoms connect together to yield large clusters. The rapid drop in the number of clusters and the speedy growth in the size of the largest cluster lead to water's exhibiting anomalously dynamic behaviors at temperatures around 279 K. Our results also show that water is very stable in its supercooled or ice state, exhibiting no change in the mean squared displacement, light oscillation in the number of the clusters and in the size of the largest cluster.

  19. A Preliminary Heat Flow Model for Cooling a Batholith near Ica, Peru

    NASA Astrophysics Data System (ADS)

    Gonzalez, L. U.; Clausen, B. L.; Molano, J. C.; Martinez, A. M.; Poma, O.

    2014-12-01

    This research models the cooling of a suite in the Linga Super-unit located at the north end of the Arequipa segment in the Cretaceous Peruvian Coastal Batholith. The monzogabbro to granite Linga suite is approximately 50 km long and 15 km wide, with an estimated vertical extent of about 5 km originally intruded to a depth of 3 km. The emplacement was in andesitic volcanics on the west and the Pampahuasi diorite Super-unit on the east and has incorporated earlier gabbroic bodies. The Linga suite is thought to be the result of a sequence of three pulses: an elongate unit to the west then two elliptical units to the northeast and southeast. The data for modeling comes from field observations on internal and external contacts, some well-defined magma chamber walls and roof, pendant and stoped blocks, magma chamber zoning, the nature and distribution of enclaves and xenoliths, magmatic fabric, evidences of magma mingling, rock porosity, mineralogical associations in metamorphic aureoles, extensive mineralization and brecciated conduits, and the types of hydrothermal alteration varying with distance from contacts. More than forty hand samples, thin sections, and geochemical analyses were used to estimate water content, magma and country rock temperature, liquid density, and viscosity. Further data will come from: zircon U-Pb ages for country rock and magma batch timeframes, fluid inclusions for magma pressure and temperature, and δ18O data for source of hydrothermal fluids. Simple heat conduction calculations using MATLAB and HEAT 3D for a single tabular intrusion estimated a cooling time to solidus of about 300 k.y. More complex modeling includes magma convection and multiple intrusions. Extensive veining and pervasive alteration suggested the use of HYDROTHERM to model possible additional heat flow effects from hydrothermal fluids. Extensive propylitic and significant potassic alteration were observed and, with TerraSpec infrared spectroscopy to identify

  20. One-heater flow-through polymerase chain reaction device by heat pipes cooling

    PubMed Central

    Chen, Jyh Jian; Liao, Ming Huei; Li, Kun Tze; Shen, Chia Ming

    2015-01-01

    the cooling module that has been designed for a PCR device. The unique architecture utilized in this flow-through PCR device is well applied to a low-cost PCR system. PMID:25713689

  1. Bayesian clustering of flow cytometry data for the diagnosis of B-chronic lymphocytic leukemia.

    PubMed

    Lakoumentas, John; Drakos, John; Karakantza, Marina; Nikiforidis, George C; Sakellaropoulos, George C

    2009-04-01

    In the rapidly advancing field of flow cytometry, methodologies facilitating automated clinical decision support are increasingly needed. In the case of B-chronic lymphocytic leukemia (B-CLL), discrimination of the various subpopulations of blood cells is an important task. In this work, our objective is to provide a useful paradigm of computer-based assistance in the domain of flow-cytometric data analysis by proposing a Bayesian methodology for flow cytometry clustering. Using Bayesian clustering, we replicate a series of (unsupervised) data clustering tasks, usually performed manually by the expert. The proposed methodology is able to incorporate the expert's knowledge, as prior information to data-driven statistical learning methods, in a simple and efficient way. We observe almost optimal clustering results, with respect to the expert's gold standard. The model is flexible enough to identify correctly non canonical clustering structures, despite the presence of various abnormalities and heterogeneities in data; it offers an advantage over other types of approaches that apply hierarchical or distance-based concepts.

  2. A numerical investigation of cluster fall velocity in vertical particle-laden turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Capecelatro, Jesse; Desjardins, Olivier; National Renewable Energy Lab Collaboration

    2012-11-01

    Particle clusters are known to play a key role in the multiphase dynamics as well as secondary processes such as heat transfer and catalytic conversion within vertical pipe flows. For example, vertical risers in circulating fluidized bed reactors consists of a dilute suspension of particles that ascend in the core of the flow, then condense into clusters and descend at the walls. In this work, an Euler-Lagrange strategy is used to study particle cluster dynamics in turbulent risers for a range of Archimedes numbers and density ratios. The simulations are conducted in the framework of NGA, a high-order fully conservative code tailored for turbulent flows. The particles are solved in a Lagrangian framework and the two phases are coupled using a two-step filtering process to ensure conservation, as well as convergence during mesh refinement. Normal and tangential collisions are computed via a soft-sphere model. A conservative immersed boundary method is used to represent the 3D cylindrical geometry on a Cartesian mesh. Simulation results are compared with experimental correlations in terms of cluster fall velocity and size. The role of the carrier fluid on the cluster behavior is also studied.

  3. Influence of bubble clusters over the turbulent structure in upward bubbly channel flows

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Yoshito; Zhang, Wenhao; Nakanishi, Hiroaki; Sakakibara, Jun; Takagi, Shu

    2015-11-01

    We conducted the PIV measurement of upward, turbulent bubbly channel flows. In our experiment, bubbles do not coalesce and become mono-dispersed 1 mm spherical shape due to surfactants in the liquid phase. Adding the surfactant in some specific conditions, these bubbles are attracted toward the wall by the shear induced lift force and form bubble clusters. While they flow near wall, the Reynolds stress of the liquid phase near wall comes close to zero. This suggests that the turbulent structure change dramatically due to bubble clusters. For the further investigation of the turbulent structure, we constructed the measurement system of Scanning Stereoscopic PIV (SSPIV) which can visualize the three-dimensional velocity field. Using this system, we acquire the velocity field and extracted the large scale vortices which dominate the turbulent structure. Also, we constructed another measurement system for tracking the bubble cluster's flow. Through the simultaneous measurement of vortices and bubble cluster, we analyze the influence of bubble cluster over the turbulent structure. The results will be discussed in the presentation.

  4. Automated gating of flow cytometry data via robust model-based clustering.

    PubMed

    Lo, Kenneth; Brinkman, Ryan Remy; Gottardo, Raphael

    2008-04-01

    The capability of flow cytometry to offer rapid quantification of multidimensional characteristics for millions of cells has made this technology indispensable for health research, medical diagnosis, and treatment. However, the lack of statistical and bioinformatics tools to parallel recent high-throughput technological advancements has hindered this technology from reaching its full potential. We propose a flexible statistical model-based clustering approach for identifying cell populations in flow cytometry data based on t-mixture models with a Box-Cox transformation. This approach generalizes the popular Gaussian mixture models to account for outliers and allow for nonelliptical clusters. We describe an Expectation-Maximization (EM) algorithm to simultaneously handle parameter estimation and transformation selection. Using two publicly available datasets, we demonstrate that our proposed methodology provides enough flexibility and robustness to mimic manual gating results performed by an expert researcher. In addition, we present results from a simulation study, which show that this new clustering framework gives better results in terms of robustness to model misspecification and estimation of the number of clusters, compared to the popular mixture models. The proposed clustering methodology is well adapted to automated analysis of flow cytometry data. It tends to give more reproducible results, and helps reduce the significant subjectivity and human time cost encountered in manual gating analysis.

  5. Analysis of metal temperature and coolant flow with a thermal-barrier coating on a full-coverage-film-cooled turbine vane

    NASA Technical Reports Server (NTRS)

    Meitner, P. L.

    1978-01-01

    The potential benefits of combining full-coverage film cooling with a thermal-barrier coating were investigated analytically for sections on the suction and pressure sides a high-temperature, high-pressure turbine vane. Metal and ceramic coating temperatures were calculated as a function of coating thickness and coolant flow. With a thermal-barrier coating, the coolant flows required for the chosen sections were half those of an uncoated design, and the metal outer temperatures were simultaneously reduced by over 111 K (200 F). For comparison, transpiration cooling was also investigated. Full-coverage film cooling of a coated vane required more coolant flow than did transpiration cooling.

  6. Conceptual design of a 20-kA current lead using forced-flow cooling and Ag-alloy-sheathed Bi-2223 high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Heller, Reinhard; Hull, John R.

    High-temperature superconductors (HTS's), consisting of Bi-2223 HTS tapes sheathed with Ag alloys are proposed for a 20-kA current lead for the planned stellarator WENDELSTEIN 7-X. Forced-flow He cooling is used, and 4-K He cooling of the whole lead as well as 60-K He cooling of the copper part of the lead, is discussed. Power consumption and behavior in case of loss of He flow are given.

  7. Core flows and heat transfer induced by inhomogeneous cooling with sub- and supercritical convection

    NASA Astrophysics Data System (ADS)

    Dietrich, W.; Hori, K.; Wicht, J.

    2016-02-01

    The amount and spatial pattern of heat extracted from cores of terrestrial planets is ultimately controlled by the thermal structure of the lower rocky mantle. Using the most common model to tackle this problem, a rapidly rotating and differentially cooled spherical shell containing an incompressible and viscous liquid is numerically investigated. To gain the physical basics, we consider a simple, equatorial symmetric perturbation of the CMB heat flux shaped as a spherical harmonic Y11 . The thermodynamic properties of the induced flows mainly depend on the degree of nonlinearity parametrised by a horizontal Rayleigh number Rah =q∗ Ra , where q∗ is the relative CMB heat flux anomaly amplitude and Ra is the Rayleigh number which controls radial buoyancy-driven convection. Depending on Rah we identify and characterise three distinctive flow regimes through their spatial patterns, heat transport and flow speed scalings: in the linear conductive regime the radial inward flow is found to be phase shifted 90° eastwards from the maximal heat flux as predicted by a linear quasi-geostrophic model for rapidly rotating spherical systems. The advective regime is characterised by an increased Rah where nonlinearities become significant, but is still subcritical to radial convection. There the upwelling is dispersed and the downwelling is compressed by the thermal advection into a spiralling jet-like structure. As Rah becomes large enough for the radial convection to set in, the jet remains identifiable on time-average and significantly alters the global heat budget in the convective regime. Our results suggest, that the boundary forcing not only introduces a net horizontal heat transport but also suppresses the convection locally to such an extent, that the net Nusselt number is reduced by up to 50%, even though the mean CMB heat flux is conserved. This also implies that a planetary core will remain hotter under a non-homogeneous CMB heat flux and is less well mixed. A

  8. Fearsome Flashes: A Study Of The Evolution Of Flaring Rates In Cool Stars Using Kepler Cluster Data

    NASA Astrophysics Data System (ADS)

    Saar, Steven

    Strong solar flares can damage power grids, satellites, interrupt communications and GPS information, and threaten astronauts and high latitude air travelers. Despite the potential cost, their frequency is poorly determined. Beyond purely current terrestrial concerns, how the rate of large flares (and associated coronal mass ejections [CMEs], high-energy particle fluxes and far UV emission) varies over the stellar lifetime holds considerable astrophysical interest. These include: the contributions of flares to coronal energy budgets; the importance of flares and CMEs to terrestrial and exoplanet atmospheric and biological evolution; and importance of CME mass loss for angular momentum evolution. We will explore the rate of strong flares and its variation with stellar age, mass and rotation by studying Kepler data of cool stars in two open clusters NGC 6811 (age ~ 1 Gyr) and NGC 6819 (~2.5 Gyr). We will use two flare analysis methods to build white-light flare distributions for cluster stars. One subtracts a low-pass filtered version of the data and analyzes the residue for positive flux deviations, the other does a statistical analysis of the flux deviations vs. time lags compared with a model. For near- solar stars, a known solar relation can then be used to estimate X-ray production by the white-light flares. For stars much hotter or cooler or with significantly different chromospheric density, we will use particle code flare models including bombardment effects to estimate how the X-ray to white light scaling changes. With the X-ray values, we can estimate far UV fluxes and CME rates, building a picture of the flare effects; with the two cluster ages, we can make a first estimate of the solar rate (by projecting to the Sun's age) and begin to build up an understanding of flare rate evolution with mass and age. Our proposal falls squarely in the "Stellar Astrophysics and Exoplanets" research area, and is relevant to NASA astrophysics goals in promoting better

  9. The influence of cooling on the advance of lava flows: insights from analogue experiments on the feedbacks between flow dynamics and thermal structure

    NASA Astrophysics Data System (ADS)

    Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

    2012-12-01

    During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. The spreading of a lava flow, seen as a gravity current, depends on its "effective rheology" and the eruptive mass flux. These two parameters are not known a priori during an eruption and a key question is how to evaluate them in near real-time (rather than afterwards.) There is no generic macroscopic model for the rheology of an advancing lava flow, and analogue modelling is a precious tool to empirically estimate the rheology of a complex flow. We investigate through laboratory experiments the simultaneous spreading and cooling of horizontal currents fed at constant rate from a point source. The materials used are silicone oil (isoviscous), and poly-ethylene glycol (PEG) wax injected in liquid state and solidiying during its advance. In the isoviscous case, the temperature field is a passive tracer of the flow dynamics, whereas in the PEG experiments there is a feedback between the cooling of the flow and its effective rheology. We focus on the evolution of the current area and of the surface thermal structure, imaged with an infrared camera, to assess how the thermal structure can be related to the flow rate. The flow advance is continuous in the viscous case, and follows the predictions of Huppert (1982); in that case the surface temperature become steady after a transient time and the radiated heat flux is shown to be proportional to the input rate. For the PEG experiments, the spreading occurs through an alternation of stagnation and overflow phases, with a mean spreading rate decreasing as the experiment goes on. As in the case of lava flows, these experiments can exhibit a compound flow field, solid levees, thermal erosion, liquid overflows and channelization. A key observation is that the effective rheology of the solifying PEG material depends on the input flow rate, with high input rates yielding a rheology closer to the

  10. Hot accretion flow with radiative cooling: state transitions in black hole X-ray binaries

    NASA Astrophysics Data System (ADS)

    Wu, Mao-Chun; Xie, Fu-Guo; Yuan, Ye-Fei; Gan, Zhaoming

    2016-06-01

    We investigate state transitions in black hole X-ray binaries through different parameters by using two-dimensional axisymmetric hydrodynamical simulation method. For radiative cooling in hot accretion flow, we take into account the bremsstrahlung, synchrotron and synchrotron self-Comptonization self-consistently in the dynamics. Our main result is that the state transitions occur when the accretion rate reaches a critical value dot{M} ˜ 3α dot{M}_Edd, above which cold and dense clumpy/filamentary structures are formed, embedded within the hot gas. We argued this mode likely corresponds to the proposed two-phase accretion model, which may be responsible for the intermediate state of black hole X-ray binaries. When the accretion rate becomes sufficiently high, the clumpy/filamentary structures gradually merge and settle down on to the mid-plane. Eventually the accretion geometry transforms to a disc-corona configuration. In summary, our results are consistent with the truncated accretion scenario for the state transition.

  11. Experimental investigation of the flow, oxidation, cooling, and thermal-fatigue characteristics of a laminated porous sheet material

    NASA Technical Reports Server (NTRS)

    Hickel, R. O.; Warren, E. L.; Kaufman, A.

    1972-01-01

    The basic flow and oxidation characteristics of a laminated porous material (Lamilloy) are presented. The oxidation characteristics of Lamilloy are compared to a wireform-type porous material for the case when both materials are made from Hastelloy-X alloy. The cooling performance of an air cooled vane made from Lamilloy, as determined from cascade tests made at gas temperatures ranging from 1388 to 1741 C (2350 to 3165 F) is also discussed, as well as of a cascade-type thermal fatigue test of the Lamilloy vane.

  12. The Distances to Open Clusters from Main-sequence Fitting. V. Extension of Color Calibration and Test Using Cool and Metal-rich Stars in NGC 6791

    NASA Astrophysics Data System (ADS)

    An, Deokkeun; Terndrup, Donald M.; Pinsonneault, Marc H.; Lee, Jae-Woo

    2015-09-01

    We extend our effort to calibrate stellar isochrones in the Johnson-Cousins ({{BVI}}C) and the 2MASS ({{JHK}}s) filter systems based on observations of well-studied open clusters. Using cool main-sequence (MS) stars in Praesepe, we define empirical corrections to the Lejeune et al. color-effective temperature ({T}{eff}) relations down to {T}{eff}˜ 3600 {{K}}, complementing our previous work based on the Hyades and the Pleiades. We apply empirically corrected isochrones to existing optical and near-infrared photometry of cool ({T}{eff}≲ 5500 {{K}}) and metal-rich ([{Fe}/{{H}}]= +0.37) MS stars in NGC 6791. The current methodology relies on an assumption that color-{T}{eff} corrections are independent of metallicity, but we find that estimates of color excess and distance from color-magnitude diagrams with different color indices converge on each other at the precisely known metallicity of the cluster. Along with a satisfactory agreement with eclipsing binary data in the cluster, we view the improved internal consistency as a validation of our calibrated isochrones at super-solar metallicities. For very cool stars ({T}{eff}≲ 4800 {{K}}), however, we find that B - V colors of our models are systematically redder than the cluster photometry by ˜0.02 mag. We use color-{T}{eff} transformations from the infrared flux method and alternative photometry to examine a potential color-scale error in the input cluster photometry. After excluding B - V photometry of these cool MS stars, we derive E(B\\-\\V)=0.105+/- 0.014, [M/H]\\=\\+0.42+/- 0.07, {(m\\-\\M)}0=13.04+/- 0.08, and the age of 9.5 ± 0.3 Gyr for NGC 6791.

  13. Suzaku X-ray Observations of the Nearest Non-Cool Core Cluster, Antlia: Dynamically Young but with Remarkably Relaxed Outskirts

    NASA Astrophysics Data System (ADS)

    Wong, Ka-Wah; Irwin, Jimmy A.; Wik, Daniel R.; Sun, Ming; Sarazin, Craig L.; Fujita, Yutaka; Reiprich, Thomas H.

    2016-09-01

    We present the results of seven Suzaku mosaic observations (>200 ks in total) of the nearest non-cool core cluster, the Antlia Cluster (or Group), beyond its degree-scale virial radius in its eastern direction. The temperature is consistent with the scaled profiles of many other clusters. Its pressure follows the universal profile. The density slope in its outskirts is significantly steeper than that of the nearest cool core cluster (Virgo) with a similar temperature as Antlia, but shallower than those of the massive clusters. The entropy increases all the way out to R 200, which is consistent in value with the baseline model predicted by a gravity heating-only mechanism in the outskirts. Antlia is quite relaxed in this direction. However, the entropy inside ˜R 500 is significantly higher than the baseline model, which is similar to many other nearby low mass clusters or groups. The enclosed gas-mass fraction does not exceed the cosmic value out to 1.3{R}200. Thus, there is no evidence of significant gas clumping, electron-ion non-equipartition, or departure from the hydrostatic equilibrium approximation that are suggested to explain the entropy and gas fraction anomalies found in the outskirts of some massive clusters. We also present scaling relations for the gas fraction ({f}{{gas,200}}), entropy (K 200), and temperature (T 500) using 22 groups and clusters with published data in the literature. The enclosed baryon fraction at R 200 is broadly consistent with the cosmic value. The power law slope of the K 200-T 500 relation is 0.638 ± 0.205. The entropy deficit at R 200 cannot be fully accounted for by the bias or deviation in the gas fraction.

  14. Performance of a 10-kJ SMES model cooled by liquid hydrogen thermo-siphon flow for ASPCS study

    NASA Astrophysics Data System (ADS)

    Makida, Y.; Shintomi, T.; Hamajima, T.; Ota, N.; Katsura, M.; Ando, K.; Takao, T.; Tsuda, M.; Miyagi, D.; Tsujigami, H.; Fujikawa, S.; Hirose, J.; Iwaki, K.; Komagome, T.

    2015-12-01

    We propose a new electrical power storage and stabilization system, called an Advanced Superconducting Power Conditioning System (ASPCS), which consists of superconducting magnetic energy storage (SMES) and hydrogen energy storage, converged on a liquid hydrogen station for fuel cell vehicles. A small 10- kJ SMES system, in which a BSCCO coil cooled by liquid hydrogen was installed, was developed to create an experimental model of an ASPCS. The SMES coil is conductively cooled by liquid hydrogen flow through a thermo-siphon line under a liquid hydrogen buffer tank. After fabrication of the system, cooldown tests were carried out using liquid hydrogen. The SMES coil was successfully charged up to a nominal current of 200 A. An eddy current loss, which was mainly induced in pure aluminum plates pasted onto each pancake coils for conduction cooling, was also measured.

  15. A study of optimum cowl shapes and flow port locations for minimum drag with effective engine cooling, volume 2

    NASA Technical Reports Server (NTRS)

    Fox, S. R.; Smetana, F. O.

    1980-01-01

    The listings, user's instructions, sample inputs, and sample outputs of two computer programs which are especially useful in obtaining an approximate solution of the viscous flow over an arbitrary nonlifting three dimensional body are provided. The first program performs a potential flow solution by a well known panel method and readjusts this initial solution to account for the effects of the boundary layer displacement thickness, a nonuniform but unidirectional onset flow field, and the presence of air intakes and exhausts. The second program is effectually a geometry package which allows the user to change or refine the shape of a body to satisfy particular needs without a significant amount of human intervention. An effort to reduce the cruise drag of light aircraft through an analytical study of the contributions to the drag arising from the engine cowl shape and the foward fuselage area and also that resulting from the cooling air mass flowing through intake and exhaust sites on the nacelle is presented. The programs may be effectively used to determine the appropriate body modifications or flow port locations to reduce the cruise drag as well as to provide sufficient air flow for cooling the engine.

  16. Metal temperatures and coolant flow in a wire cloth transpiration cooled turbine vane

    NASA Technical Reports Server (NTRS)

    Gladden, H. J.

    1975-01-01

    An experimental heat transfer investigation was conducted on an air-cooled turbine vane made from wire-wound cloth material and supported by a central strut. Vane temperature data obtained are compared with temperature data from two full-coverage film-cooled vanes made of different laminated construction. Measured porous-airfoil temperatures are compared with predicted temperatures.

  17. FORTRAN program for calculating coolant flow and metal temperatures of a full-coverage-film-cooled vane or blade

    NASA Technical Reports Server (NTRS)

    Meitner, P. L.

    1978-01-01

    A computer program that calculates the coolant flow and the metal temperatures of a full-coverage-film-cooled vane or blade was developed. The analysis was based on compressible, one-dimensional fluid flow and on one-dimensional heat transfer and treats the vane or blade shell as a porous wall. The calculated temperatures are average values for the shell outer-surface area associated with each film-cooling hole row. A thermal-barrier coating may be specified on the shell outer surface, and centrifugal effects can be included for blade calculations. The program is written in FORTRAN 4 and is operational on a UNIVAC 1100/42 computer. The method of analysis, the program input, the program output, and two sample problems are provided.

  18. AGN-selected clusters as revealed by weak lensing

    NASA Technical Reports Server (NTRS)

    Wold, M.; Lacy, M.; Dahle, H.; Lilje, P. B.; Ridgway, S. E.

    2002-01-01

    We discuss the results in light of the cooling flow and the merger/interaction scenarios for triggering and fuelling AGN in clusters, but find that the data do not point unambiguously to neither of the two.

  19. AN X-RAY COOLING-CORE CLUSTER SURROUNDING A LOW-POWER COMPACT STEEP SPECTRUM RADIO SOURCE 1321+045

    SciTech Connect

    Kunert-Bajraszewska, M.; Siemiginowska, A.; Labiano, A.

    2013-07-20

    We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z = 0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low-luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium dominated by active galactic nucleus photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radioactivity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1 {+-} 8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3{sigma} level out to {approx}60'' (240 kpc). We obtain the best-fit beta model parameters of the surface brightness profile of {beta} = 0.58 {+-} 0.2 and a core radius of 9.4{sup +1.1}{sub -0.9} arcsec. The average temperature of the cluster is equal to kT = 4.4{sup +0.5}{sub -0.3} keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L{sub (0.5-2{sub keV)}} = 3 Multiplication-Sign 10{sup 44} erg s{sup -1} and mass 1.5 Multiplication-Sign 10{sup 14} M{sub Sun}.

  20. Silicon Carbide Clusters Found in the Canyon Diablo Meteorite: Implications of Cooling Histories for Group IAB Meteorites

    NASA Astrophysics Data System (ADS)

    Leung, I. S.; Winston, R.

    2009-12-01

    The Canyon Diablo Meteorite fell in the Arizona desert 50,000 years ago. Meteoritic irons tranported to humid areas often oxidize rapidly. One of our samples was a carbon nodule in a rusty Ni-Fe matrix. Another nodule we studied, retrieved by cutting open a fresh iron sample with a diamond-impregnated blade, was about 1 cm in diameter, with rdiating black veins. A hammer and carbide chisels were used to break up the nodules. Micron-sized grains in a Petri dish were hand-picked under a microscope.We found 8 individual silicon carbide (SiC) crystals which are either light blue, deep blue, light green, or deep green, and they are 80-120 microns in size. We also found 14 clusters of acicular or mosaic aggregates, 50-150 microns in size. A green mosaic contains more than 20 grains having black carbon rims. An X-ray study revealed that the individual crystals have well-ordered 3C, 6H, and 15R polytype structures. We interpret this as an indication of slow growth for a rather long period of time. On the other hand, the SiC aggregates seem to have nucleated rapidly in a chemically oversaturated environment, perhaps during a disturbance at a relatively recent time. Further work might help elucidate cooling, evolution and complex histories of IAB iron meteorites. It should be cautioned that if dissolution methods using strong acids to separate SiC would have destroyed the delicate aggregates, and disaggregated grains might have been classified as nanno-carbides, thus, an important aspect of history might have been obliterated.

  1. OPTICAL LINE EMISSION IN BRIGHTEST CLUSTER GALAXIES AT 0 < z < 0.6: EVIDENCE FOR A LACK OF STRONG COOL CORES 3.5 Gyr AGO?

    SciTech Connect

    McDonald, Michael

    2011-12-15

    In recent years the number of known galaxy clusters beyond z {approx}> 0.2 has increased drastically with the release of multiple catalogs containing >30,000 optically detected galaxy clusters over the range 0 < z < 0.6. Combining these catalogs with the availability of optical spectroscopy of the brightest cluster galaxy (BCG) from the Sloan Digital Sky Survey allows for the evolution of optical emission-line nebulae in cluster cores to be quantified. For the first time, the continuous evolution of optical line emission in BCGs over the range 0 < z < 0.6 is determined. A minimum in the fraction of BCGs with optical line emission is found at z {approx} 0.3, suggesting that complex, filamentary emission in systems such as Perseus A is a recent phenomenon. Evidence for an upturn in the number of strongly emitting systems is reported beyond z > 0.3, hinting at an earlier epoch of strong cooling. We compare the evolution of emission-line nebulae to the X-ray-derived cool core (CC) fraction from the literature over the same redshift range and find overall agreement, with the exception that an upturn in the strong CC fraction is not observed at z > 0.3. The overall agreement between the evolution of CCs and optical line emission at low redshift suggests that emission-line surveys of galaxy clusters may provide an efficient method of indirectly probing the evolution of CCs and thus provide insights into the balance of heating and cooling processes at early cosmic times.

  2. Cold-flow performance of several variations of a ram-air-cooled plug nozzle for supersonic-cruise aircraft

    NASA Technical Reports Server (NTRS)

    Harrington, D. E.; Nosek, S. M.; Straight, D. M.

    1974-01-01

    Experimental data were obtained with a 21.59 cm (8.5 in.) diameter cold-flow model in a static altitude facility to determine the thrust and pumping characteristics of several variations of a ram-air-cooled plug nozzle. Tests were conducted over a range of nozzle pressure ratios simulating supersonic cruise and takeoff conditions. Primary throat area was also varied to simulate afterburner on and off. Effect of plug size, outer shroud length, primary nozzle geometry, and varying amounts of secondary flow were investigated. At a supersonic cruise pressure ratio of 27, nozzle efficiencies were 99.7 percent for the best configurations.

  3. Flow-induced clustering and alignment of vesicles and red blood cells in microcapillaries

    PubMed Central

    McWhirter, J. Liam; Noguchi, Hiroshi; Gompper, Gerhard

    2009-01-01

    The recent development of microfluidic devices allows the investigation and manipulation of individual liquid microdroplets, capsules, and cells. The collective behavior of several red blood cells (RBCs) or microcapsules in narrow capillaries determines their flow-induced morphology, arrangement, and effective viscosity. Of fundamental interest here is the relation between the flow behavior and the elasticity and deformability of these objects, their long-range hydrodynamic interactions in microchannels, and thermal membrane undulations. We study these mechanisms in an in silico model, which combines a particle-based mesoscale simulation technique for the fluid hydrodynamics with a triangulated-membrane model. The 2 essential control parameters are the volume fraction of RBCs (the tube hematocrit, HT), and the flow velocity. Our simulations show that already at very low HT, the deformability of RBCs implies a flow-induced cluster formation above a threshold flow velocity. At higher HT values, we predict 3 distinct phases: one consisting of disordered biconcave-disk-shaped RBCs, another with parachute-shaped RBCs aligned in a single file, and a third with slipper-shaped RBCs arranged as 2 parallel interdigitated rows. The deformation-mediated clustering and the arrangements of RBCs and microcapsules are relevant for many potential applications in physics, biology, and medicine, such as blood diagnosis and cell sorting in microfluidic devices. PMID:19369212

  4. Measurements and computational analysis of heat transfer and flow in a simulated turbine blade internal cooling passage

    NASA Technical Reports Server (NTRS)

    Russell, Louis M.; Thurman, Douglas R.; Simonyi, Patricia S.; Hippensteele, Steven A.; Poinsatte, Philip E.

    1993-01-01

    Visual and quantitative information was obtained on heat transfer and flow in a branched-duct test section that had several significant features of an internal cooling passage of a turbine blade. The objective of this study was to generate a set of experimental data that could be used to validate computer codes for internal cooling systems. Surface heat transfer coefficients and entrance flow conditions were measured at entrance Reynolds numbers of 45,000, 335,000, and 726,000. The heat transfer data were obtained using an Inconel heater sheet attached to the surface and coated with liquid crystals. Visual and quantitative flow field results using particle image velocimetry were also obtained for a plane at mid channel height for a Reynolds number of 45,000. The flow was seeded with polystyrene particles and illuminated by a laser light sheet. Computational results were determined for the same configurations and at matching Reynolds numbers; these surface heat transfer coefficients and flow velocities were computed with a commercially available code. The experimental and computational results were compared. Although some general trends did agree, there were inconsistencies in the temperature patterns as well as in the numerical results. These inconsistencies strongly suggest the need for further computational studies on complicated geometries such as the one studied.

  5. Deformation band clusters on Mars and implications for subsurface fluid flow

    USGS Publications Warehouse

    Okubo, C.H.; Schultz, R.A.; Chan, M.A.; Komatsu, G.

    2009-01-01

    High-resolution imagery reveals unprecedented lines of evidence for the presence of deformation band clusters in layered sedimentary deposits in the equatorial region of Mars. Deformation bands are a class of geologic structural discontinuity that is a precursor to faults in clastic rocks and soils. Clusters of deformation bands, consisting of many hundreds of individual subparallel bands, can act as important structural controls on subsurface fluid flow in terrestrial reservoirs, and evidence of diagenetic processes is often preserved along them. Deformation band clusters are identified on Mars based on characteristic meter-scale architectures and geologic context as observed in data from the High-Resolution Imaging Science Experiment (HiRISE) camera. The identification of deformation band clusters on Mars is a key to investigating the migration of fluids between surface and subsurface reservoirs in the planet's vast sedimentary deposits. Similar to terrestrial examples, evidence of diagenesis in the form of light- and dark-toned discoloration and wall-rock induration is recorded along many of the deformation band clusters on Mars. Therefore, these structures are important sites for future exploration and investigations into the geologic history of water and water-related processes on Mars. ?? 2008 Geological Society of America.

  6. Development of high-performance cooling devices for space application by using flow boiling in narrow channels.

    PubMed

    Miura, Shinichi; Inada, Yukihiro; Shinmoto, Yasuhisa; Ohta, Haruhiko

    2009-04-01

    Heat generation density from semiconductor devices has been increasing with the rapid development of electronic technology. The cooling system using boiling two-phase phenomena has attracted much attention because of its high heat removal potential. To develop compact and high-performance cooling systems, we conducted experiments on the increase of critical heat flux (CHF) for flow boiling in narrow channels by improved liquid supply. A large surface of 150 mm in heated length and 30 mm in width with grooves of an apex angle of 90 degrees , 0.5-mm depth, and 1 mm in pitch was employed. A structure of narrow heated channel between parallel plates with an unheated auxiliary channel was devised and tested by using water for different combinations of gap sizes and volumetric flow rates, where inlet of the main heated channel and the outlet of auxiliary unheated channel were closed to prevent the flow instability observed frequently at low flow rate for parallel two channels. For the total volumetric flow rate more than 4.5 x 10(-5) m(3)/s, higher values of CHF large than 2 x 10(6) W/m(2) were obtained for gap size of 2 mm. For gap sizes of 2 mm and 5 mm at high volumetric flow rate larger than 6.0 x 10(-5) m(3)/s, or mass velocity based on the cross section are of main heated channel 958.1 kg/m(2)s and 383.2 kg/m(2) s, respectively, the extension of dry patches was observed at the upstream location of the main heated channel resulting in burnout not at the downstream but at the upstream. By the increase in total volumetric flow rate, the pressure drop increased because of increasing in the flow rate passing through the sintered metal porous plates connecting both channels. The values of pressure drop for gap size of 2 mm were higher than that for gap size of 5 mm. When the performance of the cooling system was evaluated on the basis of pump power, ignoring its variation in the efficiency with volumetric flow rate, that is, the power defined as the product of the

  7. Very high temperature laminar flow of a gas through the entrance region of a cooled tube - Numerical calculations and experimental results.

    NASA Technical Reports Server (NTRS)

    Back, L. H.

    1972-01-01

    The laminar flow equations in differential form are solved numerically on a digital computer for flow of a very high temperature gas through the entrance region of an externally cooled tube. The solution method is described and calculations are carried out in conjunction with experimental measurements. The agreement with experiment is good, with the result indicating relatively large energy and momentum losses in the highly cooled flows considered where the pressure is nearly uniform along the flow and the core flow becomes non-adiabatic a few diameters downstream of the inlet. The effects of a large range of Reynolds number and Mach number (viscous dissipation) are also investigated.

  8. Anisotropic stress accumulation in cooling lava flows and resulting fracture patterns: Insights from starch-water desiccation experiments

    NASA Astrophysics Data System (ADS)

    Lodge, Robert W. D.; Lescinsky, David T.

    2009-09-01

    Desiccation of starch-water slurries is a useful analog for the production of polygonal fractures/columnar joints in cooling lava flows. When left to dry completely, a simple mixture of 1:1 starch and water will produce columns that appear remarkably similar to natural columnar joints formed in cooled lava flows. Columns form when the accumulation of isotropic stress exceeds the tensile strength of a material, at which point a fracture forms and advances through the material perpendicular to the desiccating surface. Individual fractures will initially form orthogonal to the desiccation surface but will quickly evolve into a hexagonal fracture network that advances incrementally through the material. However, some fracture patterns found within natural lava flows are not hexagonal ( Lodge and Lescinsky, 2009-this issue), but rather have fracture lengths that are much longer than the distance to adjacent fractures. These fractures are commonly found at lava flows that have interacted with glacial ice during emplacement. The purpose of this study is to utilize starch analog experiments to better understand the formation of these fractures and the stress regimes responsible for their non-hexagonal patterns. To simulate anisotropic conditions during cooling, the starch slurry was poured into a container with a movable wall that was attached to a screw-type jack. The jack was then set to slowly extend or retract while the slurry desiccated. This resulted in either a decrease or increase in the chamber cross-sectional area thus creating compressional or extensional regimes. Decreasing chamber area (DCA) experiments resulted in fractures with larger lengths parallel to the direction of wall movement (also direction of compression). It also caused localized thrust faulting and curved column development. Increasing chamber area (ICA) experiments produced a zone of horizontal column development along the expanding margin (produced when the wall detached from the sample

  9. Economic and technical assessment of the desiccant wheel effect on the thermal performance of cross flow cooling towers in variable wet bulb temperature

    NASA Astrophysics Data System (ADS)

    Banooni, Salem; Chitsazan, Ali

    2014-05-01

    Performance improvements of cross flow cooling towers in variable wet bulb temperature were performed. A conventional mathematical model is used to predict desiccant wheel effect on the performance of cooling tower. It is found that by using optimum parameters of desiccant wheel, the inlet air wet bulb temperature into the cooling tower would decrease more than 6 °C and outlet water temperature would decrease more than 4 °C.

  10. Heat transfer process under a film-cooled surface with presence of weak swirling flow in the mainstream

    SciTech Connect

    Yang, C.S.; Kung, T.L.; Gau, C.

    2007-11-15

    Experiments have been performed in a relatively large circular pipe to study and obtain the heat transfer data over a film-cooled surface, with the presence of weak swirling flow in the mainstream. The swirling flow is generated by a flat-vaned swirler situated upstream. A cooling film is injected from an annular slot formed by the pipe wall and the circular cover plate. The radial temperature distribution measurements at several axial locations were used to infer the film jet structure and the rate of mixing of the film jet with the swirling flow. The nondimensional parameters governing the heat transfer process under the film are derived from the system of governing equations. Experiments demonstrate that the swirl number, increasing with turbulence intensity and swirl velocity in the mainstream, can rapidly destroy the film jet structure and enhance the heat transfer process. During the course of the experiments, the blowing parameter ranged from 0.5 to 2 and the swirl number ranged from 0 to 0.6. Correlations for the Nusselt number which account for the effect of swirling flow are presented. (author)

  11. Mathematical Model of Two Phase Flow in Natural Draft Wet-Cooling Tower Including Flue Gas Injection

    NASA Astrophysics Data System (ADS)

    Hyhlík, Tomáš

    2016-03-01

    The previously developed model of natural draft wet-cooling tower flow, heat and mass transfer is extended to be able to take into account the flow of supersaturated moist air. The two phase flow model is based on void fraction of gas phase which is included in the governing equations. Homogeneous equilibrium model, where the two phases are well mixed and have the same velocity, is used. The effect of flue gas injection is included into the developed mathematical model by using source terms in governing equations and by using momentum flux coefficient and kinetic energy flux coefficient. Heat and mass transfer in the fill zone is described by the system of ordinary differential equations, where the mass transfer is represented by measured fill Merkel number and heat transfer is calculated using prescribed Lewis factor.

  12. Clustering criterion for inertial particles in two-dimensional time-periodic and three-dimensional steady flows.

    PubMed

    Sapsis, Themistoklis; Haller, George

    2010-03-01

    We derive an analytic condition that predicts the exact location of inertial particle clustering in three-dimensional steady or two-dimensional time-periodic flows. The particles turn out to cluster on attracting inertial Lagrangian coherent structures that are smooth deformations of invariant tori. We illustrate our results on three-dimensional steady flows, including the Hill's spherical vortex and the Arnold-Beltrami-Childress flow, as well as on a two-dimensional time and space periodic flow that models a meandering jet in a channel.

  13. Cold air performance of a 12.766-centimeter-tip-diameter axial-flow cooled turbine. 2: Effect of air ejection on turbine performance

    NASA Technical Reports Server (NTRS)

    Haas, J. E.; Kofskey, M. G.

    1977-01-01

    An air cooled version of a single-stage, axial-flow turbine was investigated to determine aerodynamic performance with and without air ejection from the stator and rotor blades surfaces to simulate the effect of cooling air discharge. Air ejection rate was varied from 0 to 10 percent of turbine mass flow for both the stator and the rotor. A primary-to-air ejection temperature ratio of about 1 was maintained.

  14. Cluster analysis of Northern Hemisphere wintertime 500-hPa flow regimes during 1920-2014

    NASA Astrophysics Data System (ADS)

    Bao, Ming; Wallace, John

    2016-04-01

    Clusters in the Northern Hemisphere wintertime, 10-day low-pass-filtered 500-hPa height field are identified using the method of self-organizing maps (SOMs). Results are based on 1) a 57-winter record of ERA and 2) a 93-winter record of the NOAA Twentieth-Century Reanalysis (20CR). The clusters derived from SOMs appear to be more robust and more linearly independent than their counterparts derived from Ward's method, and clusters with comparable numbers of member days are more distinctive in terms of the standardized Euclidean distances of their centroids from the centroid of the dataset. The reproducible SOM clusters in the hemispheric domain are 1) the negative polarity of the North Atlantic Oscillation (NAO), 2) a pattern suggestive of Alaska blocking with a downstream wave train extending over North America and the North Atlantic, 3) an enhancement of the climatological-mean stationary wave pattern in theWestern Hemisphere that projects positively upon the Pacific-North America (PNA) pattern, and 4) a pattern that projects upon the negative polarity of the PNA pattern. The first three patterns have important impacts on the wintertime climate in North America and Europe. In particular, they are helpful in interpreting prevailing flow patterns during the exceptional winters of 1930-31, 2009-10, and 2013-14.

  15. Steady State Transportation Cooling in Porous Media Under Local, Non-Thermal Equilibrium Fluid Flow

    NASA Technical Reports Server (NTRS)

    Rodriquez, Alvaro Che

    2002-01-01

    An analytical solution to the steady-state fluid temperature for 1-D (one dimensional) transpiration cooling has been derived. Transpiration cooling has potential use in the aerospace industry for protection against high heating environments for re-entry vehicles. Literature for analytical treatments of transpiration cooling has been largely confined to the assumption of thermal equilibrium between the porous matrix and fluid. In the present analysis, the fundamental fluid and matrix equations are coupled through a volumetric heat transfer coefficient and investigated in non-thermal equilibrium. The effects of varying the thermal conductivity of the solid matrix and the heat transfer coefficient are investigated. The results are also compared to existing experimental data.

  16. Numerical model for swirl flow cooling in high-heat-flux particle beam targets and the design of a swirl-flow-based plasma limiter

    SciTech Connect

    Milora, S.L.; Combs, S.K.; Foster, C.A.

    1984-11-01

    An unsteady, two-dimensional heat conduction code has been used to study the performance of swirl-flow-based neutral particle beam targets. The model includes the effects of two-phase heat transfer and asymmetric heating of tubular elements. The calorimeter installed in the Medium Energy Test Facility, which has been subjected to 30-s neutral beam pulses with incident heat flux intensities of greater than or equal to 5 kW/cm/sup 2/, has been modeled. The numerical results indicate that local heat fluxes in excess of 7 kW/cm/sup 2/ occur at the water-cooled surface on the side exposed to the beam. This exceeds critical heat flux limits for uniformly heated tubes wih straight flow by approximately a factor of 5. The design of a plasma limiter based on swirl flow heat transfer is presented.

  17. Study of hot flow anomalies using Cluster multi-spacecraft measurements

    NASA Astrophysics Data System (ADS)

    Facskó, G.; Trotignon, J. G.; Dandouras, I.; Lucek, E. A.; Daly, P. W.

    2010-02-01

    Hot flow anomalies (HFAs) were first discovered in the early 1980s at the bow shock of the Earth. In the 1990s these features were studied, observed and simulated very intensively and many new missions (Cluster, THEMIS, Cassini and Venus Express) focused the attention to this phenomenon again. Many basic features and the HFA formation mechanism were clarified observationally and using hybrid simulation techniques. We described previous observational, theoretical and simulation results in the research field of HFAs. We introduced HFA observations performed at the Earth, Mars, Venus and Saturn in this paper. We share different observation results of space mission to give an overview to the reader. Cluster multi-spacecraft measurements gave us more observed HFA events and finer, more sophisticated methods to understand them better. In this study, HFAs were studied using observations of the Cluster magnetometer and the Cluster plasma detector aboard the four Cluster spacecraft. Energetic particle measurements (28.2-68.9 keV) were also used to detect and select HFAs. We studied several specific features of tangential discontinuities generating HFAs on the basis of Cluster measurements in the period February-April 2003, December 2005-April 2006 and January-April, 2007, when the separation of spacecraft was large and the Cluster fleet reached the bow shock. We have confirmed the condition for forming HFAs, that the solar wind speed is higher than the average. This condition was also confirmed by simultaneous ACE magnetic field and solar wind plasma observations at the L1 point 1.4 million km upstream of the Earth. The measured and calculated features of HFA events were compared with the results of different previous hybrid simulations. During the whole spring season of 2003, the solar wind speed was higher than the average. Here we checked whether the higher solar wind speed is a real condition of HFA formation also in 2006 and 2007. At the end we gave an outlook and

  18. Particle image velocimetry measurements in a representative gas-cooled prismatic reactor core model for the estimation of bypass flow

    NASA Astrophysics Data System (ADS)

    Conder, Thomas E.

    Core bypass flow is considered one of the largest contributors to uncertainty in fuel temperature within the Modular High Temperature Gas-cooled Reactor (MHTGR). It refers to the coolant that navigates through the interstitial regions between the graphite fuel blocks instead of traveling through the designated coolant channels. These flows are of concern because they reduce the desired flow rates in the coolant channels, and thereby have significant influence on the maximum fuel element and coolant exit temperatures. Thus, accurate prediction of the bypass flow is important because it directly impacts core temperature, influencing the life and efficiency of the reactor. An experiment was conducted at Idaho National Laboratory to quantify the flow in the coolant channels in relation to the interstitial gaps between fuel blocks in a representative MHTGR core. Particle Image Velocimetry (PIV) was used to measure the flow fields within a simplified model, which comprised of a stacked junction of six partial fuel blocks with nine coolant tubes, separated by a 6mm gap width. The model had three sections: The upper plenum, upper block, and lower block. Model components were fabricated from clear, fused quartz where optical access was needed for the PIV measurements. Measurements were taken in three streamwise locations: in the upper plenum and in the midsection of the large and small fuel blocks. A laser light sheet was oriented parallel to the flow, while velocity fields were measured at millimeter intervals across the width of the model, totaling 3,276 PIV measurement locations. Inlet conditions were varied to incorporate laminar, transition, and turbulent flows in the coolant channels---all which produced laminar flow in the gap and non-uniform, turbulent flow in the upper plenum. The images were analyzed to create vector maps, and the data was exported for processing and compilation. The bypass flow was estimated by calculating the flow rates through the coolant

  19. Magnetic self-assembly of microparticle clusters in an aqueous two-phase microfluidic cross-flow

    NASA Astrophysics Data System (ADS)

    Abbasi, Niki; Jones, Steven G.; Moon, Byeong-Ui; Tsai, Scott S. H.

    2015-11-01

    We present a technique that self-assembles paramagnetic microparticles on the interface of aqueous two-phase system (ATPS) fluids in a microfluidic cross-flow. A co-flow of the ATPS is formed in the microfluidic cross channel as the flows of a dilute dextran (DEX) phase, along with a flow-focused particle suspension, converges with a dilute polyethylene glycol (PEG) phase. The microparticles arrive at the liquid-liquid interface and self-assemble into particle clusters due to forces on the particles from an applied external magnetic field gradient, and the interfacial tension of the ATPS. The microparticles form clusters at the interface, and once the cluster size grows to a critical value, the cluster passes through the interface. We control the size of the self-assembled clusters, as they pass through the interface, by varying the strength of the applied magnetic field gradient and the ATPS interfacial tension. We observe rich assembly dynamics, from the formation of Pickering emulsions to clusters that are completely encapsulated inside DEX phase droplets. We anticipate that this microparticle self-assembly method may have important biotechnological applications that require the controlled assembly of cells into clusters.

  20. Liquid metal cooled nuclear reactors with passive cooling system

    DOEpatents

    Hunsbedt, Anstein; Fanning, Alan W.

    1991-01-01

    A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting from fuel decay during reactor shutdown. The passive cooling system comprises a plurality of cooling medium flow circuits which cooperate to remove and carry heat away from the fuel core upon loss of the normal cooling flow circuit to areas external thereto.

  1. Effect of sintering columns on the heat transfer and flow characteristics of the liquid cooling vapor chambers

    NASA Astrophysics Data System (ADS)

    Naphon, Paisarn; Wiriyasart, Songkran

    2016-09-01

    The results of the heat and flow characteristics of working fluid inside the vapor chamber with different sintering columns of 20, 81, 225 are presented. The vapor chambers with one inlet port and four outlet ports are tested by using water as coolant. Parametric studies including different heat fluxes, number and size of wick columns, and flow rate of coolants on the cooling performance are considered. A three-dimensional heat and mass transfer model for vapor chamber with wick and without sintering plate and sintering columns are developed. The numerical simulation results show the velocity and pressure distribution of liquid and vapor phases of the working fluid inside the vapor chamber. It is found that the number of wick column have an important influence to the velocity and pressure phenomena of working fluid which results in thermal performance of vapor chamber. Reasonable agreement is obtained from the comparison between the measured data and the predicted results.

  2. Quasi One-Dimensional Model of Natural Draft Wet-Cooling Tower Flow, Heat and Mass Transfer

    NASA Astrophysics Data System (ADS)

    Hyhlík, Tomáš

    2015-05-01

    The article deals with the development of CFD (Computational Fluid Dynamics) model of natural draft wet-cooling tower flow, heat and mass transfer. The moist air flow is described by the system of conservation laws along with additional equations. Moist air is assumed to be homogeneous mixture of dry air and water vapour. Liquid phase in the fill zone is described by the system of ordinary differential equations. Boundary value problem for the system of conservation laws is discretized in space using Kurganov-Tadmor central scheme and in time using strong stability preserving Runge-Kutta scheme. Initial value problems in the fill zone is solved by using standard fourth order Runge-Kutta scheme. The interaction between liquid water and moist air is done by source terms in governing equations.

  3. The flow-chart loop: temperature, density, and cooling observables supporting nanoflare coronal heating models

    SciTech Connect

    Schmelz, J. T.; Pathak, S.; Dhaliwal, R. S.; Christian, G. M.; Fair, C. B.

    2014-11-10

    We have tested three controversial properties for a target loop observed with the Atmospheric Imaging Assembly: (1) overdense loops; (2) long-lifetime loops; and (3) multithermal loops. Our loop is overdense by a factor of about 10 compared to results expected from steady uniform heating models. If this were the only inconsistency, our loop could still be modeled as a single strand, but the density mismatch would imply that the heating must be impulsive. Moving on to the second observable, however, we find that the loop lifetime is at least an order of magnitude greater than the predicted cooling time. This implies that the loop cannot be composed of a single flux tube, even if the heating were dynamic, and must be multi-stranded. Finally, differential emission measure analysis shows that the cross-field temperature of the target loop is multithermal in the early and middle phases of its lifetime, but effectively isothermal before it fades from view. If these multithermal cooling results are found to be widespread, our results could resolve the original coronal loop controversy of 'isothermal' versus 'multithermal' cross-field temperatures. That is, the cross-field temperature is not always 'multithermal' nor is it always 'isothermal', but might change as the loop cools. We find that the existence and evolution of this loop is consistent with predictions of nanoflare heating.

  4. Computational Fluid Dynamic (CFD) analysis of axisymmetric plume and base flow of film/dump cooled rocket nozzle

    NASA Technical Reports Server (NTRS)

    Tucker, P. K.; Warsi, S. A.

    1993-01-01

    Film/dump cooling a rocket nozzle with fuel rich gas, as in the National Launch System (NLS) Space Transportation Main Engine (STME), adds potential complexities for integrating the engine with the vehicle. The chief concern is that once the film coolant is exhausted from the nozzle, conditions may exist during flight for the fuel-rich film gases to be recirculated to the vehicle base region. The result could be significantly higher base temperatures than would be expected from a regeneratively cooled nozzle. CFD analyses were conduced to augment classical scaling techniques for vehicle base environments. The FDNS code with finite rate chemistry was used to simulate a single, axisymmetric STME plume and the NLS base area. Parallel calculations were made of the Saturn V S-1 C/F1 plume base area flows. The objective was to characterize the plume/freestream shear layer for both vehicles as inputs for scaling the S-C/F1 flight data to NLS/STME conditions. The code was validated on high speed flows with relevant physics. This paper contains the calculations for the NLS/STME plume for the baseline nozzle and a modified nozzle. The modified nozzle was intended to reduce the fuel available for recirculation to the vehicle base region. Plumes for both nozzles were calculated at 10kFT and 50kFT.

  5. A Computational Study for the Utilization of Jet Pulsations in Gas Turbine Film Cooling and Flow Control

    NASA Technical Reports Server (NTRS)

    Kartuzova, Olga V.

    2012-01-01

    This report is the second part of a three-part final report of research performed under an NRA cooperative Agreement contract. The first part is NASA/CR-2012-217415. The third part is NASA/CR-2012-217417. Jets have been utilized in various turbomachinery applications in order to improve gas turbines performance. Jet pulsation is a promising technique because of the reduction in the amount of air removed from compressor. In this work two areas of pulsed jets applications were computationally investigated using the commercial code Fluent (ANSYS, Inc.); the first one is film cooling of High Pressure Turbine (HPT) blades and second one is flow separation control over Low Pressure Turbine (LPT) airfoil using Vortex Generator Jets (VGJ). Using pulsed jets for film cooling purposes can help to improve the effectiveness and thus allow higher turbine inlet temperature. Effects of the film hole geometry, blowing ratio and density ratio of the jet, pulsation frequency and duty cycle of blowing on the film cooling effectiveness were investigated. As for the low-pressure turbine (LPT) stages, the boundary layer separation on the suction side of airfoils can occur due to strong adverse pressure gradients. The problem is exacerbated as airfoil loading is increased. Active flow control could provide a means for minimizing separation under conditions where it is most severe (low Reynolds number), without causing additional losses under other conditions (high Reynolds number). The effects of the jet geometry, blowing ratio, density ratio, pulsation frequency and duty cycle on the size of the separated region were examined in this work. The results from Reynolds Averaged Navier-Stokes and Large Eddy Simulation computational approaches were compared with the experimental data.

  6. Critical flow and clustering in a model of granular transport: the interplay between drift and antidiffusion.

    PubMed

    Kanellopoulos, Giorgos; van der Weele, Ko

    2012-06-01

    We study the transport of granular matter through a staircaselike array of K vertically vibrated compartments. Given a constant inflow rate Qflow establishes itself along the entire length of the system. However, as soon as Q grows beyond the critical value Q{cr}(K) the particles form a cluster and the flow comes to a halt. Interestingly, this clustering is preceded by a subcritical warning signal: for Q values just below Q{cr}(K) the density profile along the conveyor belt spontaneously develops a pattern in which the compartments are alternatingly densely and sparsely populated. In a previous paper [Kanellopoulos and van der Weele, Int. J. Bifurcation Chaos 21, 2305 (2011)] this pattern was shown to be the result of a period-doubling bifurcation. The present paper aims at unravelling the physical mechanism that lies at the basis of the pattern formation. To this end we study the continuum version of the same system, replacing the compartment number k=1,...,K by a continuous variable x. The dynamics of the system is now described (instead of by K coupled ordinary differential equations) by a single partial differential equation of the Fokker-Planck type, with a drift and a diffusive term that both depend on the density. The drift term turns out to be responsible for the subcritical density oscillations, thereby paving the way for the eventual clustering which sets in when the diffusion coefficient becomes negative. The observed sequence of events in the granular transport system is thus explained as an interplay between drift and (anti)diffusion. PMID:23005082

  7. Estimating {Omega} from galaxy redshifts: Linear flow distortions and nonlinear clustering

    SciTech Connect

    Bromley, B.C. |; Warren, M.S.; Zurek, W.H.

    1997-02-01

    We propose a method to determine the cosmic mass density {Omega} from redshift-space distortions induced by large-scale flows in the presence of nonlinear clustering. Nonlinear structures in redshift space, such as fingers of God, can contaminate distortions from linear flows on scales as large as several times the small-scale pairwise velocity dispersion {sigma}{sub {nu}}. Following Peacock & Dodds, we work in the Fourier domain and propose a model to describe the anisotropy in the redshift-space power spectrum; tests with high-resolution numerical data demonstrate that the model is robust for both mass and biased galaxy halos on translinear scales and above. On the basis of this model, we propose an estimator of the linear growth parameter {beta}={Omega}{sup 0.6}/b, where b measures bias, derived from sampling functions that are tuned to eliminate distortions from nonlinear clustering. The measure is tested on the numerical data and found to recover the true value of {beta} to within {approximately}10{percent}. An analysis of {ital IRAS} 1.2 Jy galaxies yields {beta}=0.8{sub {minus}0.3}{sup +0.4} at a scale of 1000kms{sup {minus}1}, which is close to optimal given the shot noise and finite size of the survey. This measurement is consistent with dynamical estimates of {beta} derived from both real-space and redshift-space information. The importance of the method presented here is that nonlinear clustering effects are removed to enable linear correlation anisotropy measurements on scales approaching the translinear regime. We discuss implications for analyses of forthcoming optical redshift surveys in which the dispersion is more than a factor of 2 greater than in the {ital IRAS} data. {copyright} {ital 1997} {ital The American Astronomical Society}

  8. Critical flow and clustering in a model of granular transport: The interplay between drift and antidiffusion

    NASA Astrophysics Data System (ADS)

    Kanellopoulos, Giorgos; van der Weele, Ko

    2012-06-01

    We study the transport of granular matter through a staircaselike array of K vertically vibrated compartments. Given a constant inflow rate Qflow establishes itself along the entire length of the system. However, as soon as Q grows beyond the critical value Qcr(K) the particles form a cluster and the flow comes to a halt. Interestingly, this clustering is preceded by a subcritical warning signal: for Q values just below Qcr(K) the density profile along the conveyor belt spontaneously develops a pattern in which the compartments are alternatingly densely and sparsely populated. In a previous paper [Kanellopoulos and van der Weele, Int. J. Bifurcation ChaosIJBEE40218-127410.1142/S021812741102980X 21, 2305 (2011)] this pattern was shown to be the result of a period-doubling bifurcation. The present paper aims at unravelling the physical mechanism that lies at the basis of the pattern formation. To this end we study the continuum version of the same system, replacing the compartment number k=1,...,K by a continuous variable x. The dynamics of the system is now described (instead of by K coupled ordinary differential equations) by a single partial differential equation of the Fokker-Planck type, with a drift and a diffusive term that both depend on the density. The drift term turns out to be responsible for the subcritical density oscillations, thereby paving the way for the eventual clustering which sets in when the diffusion coefficient becomes negative. The observed sequence of events in the granular transport system is thus explained as an interplay between drift and (anti)diffusion.

  9. Is cooling still cool?

    PubMed

    Subramaniam, Ashwin; Tiruvoipati, Ravindranath; Botha, John

    2015-03-01

    Therapeutic hypothermia (TH), where patients are cooled to between 32°C and 36°C for a period of 12-24 hours and then gradually rewarmed, may reduce the risk of ischemic injury to cerebral tissue following a period of insufficient blood flow. This strategy of TH could improve mortality and neurological function in patients who have experienced out-of-hospital cardiac arrest (OOHCA). The necessity of TH in OOHCA was challenged in late 2013 by a fascinating and potentially practice changing publication, which found that targeting a temperature of 36°C had similar outcomes to cooling patients to 33°C. This article reviews the current literature and summarizes the uncertainties and questions raised when considering cooling of patients at risk of hypoxic brain injury. Irrespective of whether TH or targeted temperature management is deployed in patients at risk of hypoxic brain injury, it would seem that avoiding hyperpyrexia is important and that a more rigorous approach to neurological evaluation is mandated. PMID:25423577

  10. Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

    NASA Technical Reports Server (NTRS)

    Braman, Kalen; Ruf, Joseph

    2015-01-01

    Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and with four different versions of the TIC nozzle model geometry, each of which was created with a different simplification to the test article geometry.

  11. Passive containment cooling system

    DOEpatents

    Conway, Lawrence E.; Stewart, William A.

    1991-01-01

    A containment cooling system utilizes a naturally induced air flow and a gravity flow of water over the containment shell which encloses a reactor core to cool reactor core decay heat in two stages. When core decay heat is greatest, the water and air flow combine to provide adequate evaporative cooling as heat from within the containment is transferred to the water flowing over the same. The water is heated by heat transfer and then evaporated and removed by the air flow. After an initial period of about three to four days when core decay heat is greatest, air flow alone is sufficient to cool the containment.

  12. Magnetic grain-size variations through an ash flow sheet: Influence on magnetic properties and implications for cooling history

    SciTech Connect

    Rosenbaum, J.G.

    1993-07-10

    Rock magnetic studies of tuffs are essential to the interpretation of paleomagnetic data derived from such rocks, provide a basis for interpretation of aeromagnetic data over volcanic terranes, and yield insights into the depositional and cooling histories of ash flow sheets. A rhyolitic ash flow sheet, the Miocene-aged Tiva Canyon Member of the Paintbrush Tuff, contains both titanomagnetite phenocrysts, present in the magma prior to eruption, and cubic Fe-oxide microcrystals that grew after emplacement. Systematic variations in the quantity and magnetic grain size of the microcrystals produce large variations in magnetic properties through a section of the ash flow sheet penetrated in a borehole on the Nevada Test Site. Natural remanent magnetization varies from less than 1 x 10{sup {minus}4} to more than 8 x 10{sup {minus}4} A m{sup 3} kg{sup {minus}1}, and in-phase magnetic susceptibility varies from less than 1 x 10{sup {minus}6} to more than 10 x 10{sup {minus}6} m{sup 3} kg{sup {minus}1}. The microcrystals, which include both magnetite and maghemite, have Curie points and maximum unblocking temperatures between 580{degrees}C and 640{degrees}C. Rock magnetic data, including in-phase and quadrature magnetic susceptibilities as well as hysteresis parameters, demonstrate that these microcrystals are of superparamagnetic and single-domain sizes. Titanomagnetite phenocrysts are the dominant remanence carriers in the central 50 m of the section, whereas microcrystals are important contributors to remanent magnetization and magnetic susceptibility in two 15-m-thick zones at the top and bottom. Within these zones the size of microcrystals decreases both toward the quenched margins and toward the interior of the sheet. The decrease in microcrystal size toward the interior of the sheet is interpreted to indicate the presence of a cooling break; possibly represented by a concentration of pumice. 32 refs., 11 figs.

  13. Simulation of cooling and pressure effects on inflated pahoehoe lava flows

    NASA Astrophysics Data System (ADS)

    Glaze, Lori S.; Baloga, Stephen M.

    2016-01-01

    Pahoehoe lobes are often emplaced by the advance of discrete toes accompanied by inflation of the lobe surface. Many random effects complicate modeling lobe emplacement, such as the location and orientation of toe breakouts, their dimensions, mechanical strength of the crust, microtopography, and a host of other factors. Models that treat the movement of lava parcels as a random walk have explained some of the overall features of emplacement. However, cooling of the surface and internal pressurization of the fluid interior have not been modeled. This work reports lobe simulations that explicitly incorporate (1) cooling of surface lava parcels, (2) the propensity of breakouts to occur at warmer margins that are mechanically weaker than cooler ones, and (3) the influence of internal pressurization associated with inflation. The surface temperature is interpreted as a surrogate for the mechanic strength of the crust at each location and is used to determine the probability of a lava parcel transfer from that location. When only surface temperature is considered, the morphology and dimensions of simulated lobes are indistinguishable from equiprobable simulations. However, inflation within a lobe transmits pressure to all connected fluid locations with the warmer margins being most susceptible to breakouts and expansion. Simulations accounting for internal pressurization feature morphologies and dimensions that are dramatically different from the equiprobable and temperature-dependent models. Even on flat subsurfaces the pressure-dependent model produces elongate lobes with distinct directionality. Observables such as topographic profiles, aspect ratios, and maximum extents should be readily distinguishable in the field.

  14. Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean

    PubMed Central

    Horikawa, Keiji; Martin, Ellen E.; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

    2015-01-01

    Warming of high northern latitudes in the Pliocene (5.33–2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling. PMID:26119338

  15. Spectrally-resolved forbidden emission lines: new EXES constraints on accelerating flows from cool evolved stars

    NASA Astrophysics Data System (ADS)

    Harper, Graham

    2015-10-01

    Mass loss from cool evolved stars is important for both stellar evolution and galactic chemical evolution, but it still remains poorly understood. Early-M supergiants are important for mass loss studies because they have little dust and molecules in their winds and yet still are able to drive high mass-loss rates like their dusty cousins of later spectral-types. We propose to use SOFIA-EXES to spectrally-resolve with R=50,000 two 25 micron forbidden emission lines from the ground terms of [Fe II] and [S I] in order to trace the wind acceleration and turbulence in the outflows of cool evolved M stars. For early-M supergiants these species will be the dominant ionization stages and trace the outflow mass, and the emission diagnostics can be used to test theoretical models in the crucial wind acceleration region. We also seek to refine the intrinsic wavelength of the [S I] 25.249 micron line so that it can be used as a new astrophysical velocity diagnostic.

  16. Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean.

    PubMed

    Horikawa, Keiji; Martin, Ellen E; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

    2015-01-01

    Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling. PMID:26119338

  17. Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Horikawa, Keiji; Martin, Ellen E.; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

    2015-06-01

    Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling.

  18. Additions to compact heat exchanger technology: Jet impingement cooling & flow & heat transfer in metal foam-fins

    NASA Astrophysics Data System (ADS)

    Onstad, Andrew J.

    Compact heat exchangers have been designed following the same basic methodology for over fifty years. However, with the present emphasis on energy efficiency and light weight of prime movers there is increasing demand for completely new heat exchangers. Moreover, new materials and mesoscale fabrication technologies offer the possibility of significantly improving heat exchanger performance over conventional designs. This work involves fundamental flow and heat transfer experimentation to explore two new heat exchange systems: in Part I, large arrays of impinging jets with local extraction and in Part II, metal foams used as fins. Jet impingement cooling is widely used in applications ranging from paper manufacturing to the cooling of gas turbine blades because of the very high local heat transfer coefficients that are possible. While the use of single jet impingement results in non-uniform cooling, increased and more uniform mean heat transfer coefficients may be attained by dividing the total cooling flow among an array of smaller jets. Unfortunately, when the spent fluid from the array's central jets interact with the outer jets, the overall mean heat transfer coefficient is reduced. This problem can be alleviated by locally extracting the spent fluid before it is able to interact with the surrounding jets. An experimental investigation was carried out on a compact impingement array (Xn/Djet = 2.34) utilizing local extraction of the spent fluid (Aspent/Ajet = 2.23) from the jet exit plane. Spatially resolved measurements of the mean velocity field within the array were carried out at jet Reynolds numbers of 2300 and 5300 by magnetic resonance velocimetry, MRV. The geometry provided for a smooth transition from the jet to the target surface and out through the extraction holes without obvious flow recirculation. Mean Nusselt number measurements were also carried out for a Reynolds number range of 2000 to 10,000. The Nusselt number was found to increase with the

  19. Characteristics of steam flow in the case of shock wave heating and cooling in supersonic nozzles

    NASA Astrophysics Data System (ADS)

    Britan, A. B.; Testov, V. G.; Khmelevskii, A. N.

    1992-08-01

    A study is made of the effect of steam condensation on the walls of a shock tube on the formation of flow parameters in the wake of shock waves in a nozzle. In particular, attention is given to the effect of an absorbing condensate film on measurements of the absorption factor of H2O. The Reynolds number of the laminar-turbulent transition of the boundary layer behind an incident shock wave in the case of steam flow in a shock tube is determined experimentally.

  20. Modular jet impingement assemblies with passive and active flow control for electronics cooling

    DOEpatents

    Zhou, Feng; Dede, Ercan Mehmet; Joshi, Shailesh

    2016-09-13

    Power electronics modules having modular jet impingement assembly utilized to cool heat generating devices are disclosed. The modular jet impingement assemblies include a modular manifold having a distribution recess, one or more angled inlet connection tubes positioned at an inlet end of the modular manifold that fluidly couple the inlet tube to the distribution recess and one or more outlet connection tubes positioned at an outlet end of the modular manifold that fluidly coupling the outlet tube to the distribution recess. The modular jet impingement assemblies include a manifold insert removably positioned within the distribution recess and include one or more inlet branch channels each including an impinging slot and one or more outlet branch channels each including a collecting slot. Further a heat transfer plate coupled to the modular manifold, the heat transfer plate comprising an impingement surface including an array of fins that extend toward the manifold insert.

  1. Liquid-Cooled Garment

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A liquid-cooled bra, offshoot of Apollo moon suit technology, aids the cancer-detection technique known as infrared thermography. Water flowing through tubes in the bra cools the skin surface to improve resolution of thermograph image.

  2. Clustering and relative velocity of heavy particles under gravitational settling in isotropic turbulent flows

    NASA Astrophysics Data System (ADS)

    Jin, Guodong; He, Guo-Wei

    2015-11-01

    Clustering and intermittency in radial relative velocity (RRV) of heavy particles of same size settling in turbulent flows can be remarkably changed due to gravity. Clustering is monotonically reduced at Stokes number less than 1 under gravity due to the disability of the centrifugal mechanism, however it is non-monotonically enhanced at Stokes number greater than 1 due to the multiplicative amplification in the case that the proposed effective Kubo number is less than 1. Although gravity causes monotonical reduction in the rms of RRV of particles at a given Stokes number with decreasing Froude number, the variation tendency in the tails of standardized PDF of RRV versus Froude number is obviously different: the tails become narrower at a small Stokes number, while they become broader at a large Stokes number. The mechanism of this variation stems from the compromise between the following two competing factors. The mitigation of correlation of particle positions and the regions of high strain rate which are more intermittent reduces the intermittency in RRV at small Stokes numbers, while the significant reduction in the backward-in-time relative separations will make particle pairs see small-scale structures, leading to a higher intermittency in RRV at large Stokes numbers. NSAF of China (grant number U1230126); NSFC (grant numbers 11072247 and 11232011).

  3. Modular high-temperature gas-cooled reactor short-term thermal response to flow and reactivity transients

    SciTech Connect

    Cleveland, J.C. )

    1993-02-01

    The research reported here has been conducted at the Oak Ridge National Laboratory for the Nuclear Regulatory Commission's Division of Regulatory Applications of the Office of Nuclear Regulatory Research. The short-term thermal response of the Modular High-Temperature Gas-Cooled Reactor (MHTGR) is analyzed for a range of flow and reactivity transients. These transients include loss of forced circulation without scram, spurious withdrawal of a control rod group, moisture ingress, control rod and control rod group ejections, and a rapid core cooling event. For each event analyzed, an event description, a discussion of the analysis approach and assumptions, and results are presented. When possible, results of these analyses are compared with those presented by the designers in the MHTGR Preliminary Safety Information Document and in the MHTGR Probabilistic Risk Assessment. The importance of inherent safety features is illustrated, and conclusions are presented regarding the safety performance of the MHTGR. Recommendations are made for a more in-depth examination of MHTGR response for some of the analyzed transients. The coupled heat transfer-neutron kinetics model is described in detail in Appendix A.

  4. Influence of basal slip on the propagation and cooling of lava flows

    NASA Astrophysics Data System (ADS)

    Melnik, Oleg; Vedeneeva, Elena; Utkin, Ivan

    2015-04-01

    A thin layer approximation is used for studying of viscous gravity currents on the horizontal topography from a point source. The main difference from a self-similar solution obtained in Huppert (1982) is the account for partial slip of lava on the ground surface. We assume that the slip velocity is proportional to the tangential stress in some positive power. This condition is widely used in polymer science and for the flows on superhydrophobic surfaces. This condition is also applicable for lava flows because of a large roughness of volcanic terrains and the presence of unconsolidated material (ash, lapilli). The system of Stokes equations was reduced to a non-linear parabolic differential equation. Its solution was found both numerically and by a reduction to an ODE that describes similarity solution. In the latter case there is a dependence between lava mass growth rate and the power exponent in the friction law. It was shown that the presence of basal slip allows much faster propagation of lava flows in comparison with no-slip condition at the ground surface. Analytical solutions were proved by a good comparison with fully 2D axisymmetric finite volume simulations. Based on the velocity field obtained from a thin layer theory the heat budget of a lava flow was studied for the case of constant lava viscosity. Heat equation was solved in the lava domain with no flux condition at the bottom, radiative and convective fluxes at the free surface and the influx of a fresh magma from a point source. It was shown that due to a strong difference in the velocity profile the distribution of the temperature inside the lava flow is different in the cases of no-slip and partial slip conditions.

  5. Determination of cluster composition in heteroaggregation of binary particle systems by flow cytometry.

    PubMed

    Rollié, Sascha; Sundmacher, Kai

    2008-12-01

    Cluster composition in aggregation processes of multiple particle species can be dynamically determined by flow cytometry if particle populations are fluorescently labeled. By flow cytometric single particle analysis, aggregates can be characterized according to the exact amount of constituent particles, allowing the detailed and separate quantification of homo- and heteroaggregation. This contribution demonstrates the application of flow cytometry for the experimental detection of heteroaggregation in a binary particle mixture of oppositely charged polystyrene (PS) particles and Rhodamine-B labeled melamine-formaldehyde (MF-RhB) particles. Experiments with different particle concentration, temperature, mixing mode, ionic strength and particle mixing ratio are presented. Aggregation kinetics are enhanced with increasing particle concentration and temperature as well as by increased shear of mixing. These results represent well-known behavior published in previous investigations and validate the performance of flow cytometry for probing heteroaggregation processes. Physical insight with a novel level of detail is gained by the quantification of de- and restabilization phenomena. At low ionic strength, "raspberry"-type aggregates with PS cores are formed by primary heteroaggregation. At moderate particle number ratios, these aggregates are electrostatically destabilized and form more complex aggregates in a secondary heteroaggregation process. At high particle number ratios (> or =50:1), the raspberry-type aggregates are electrostatically restabilized and secondary heteroaggregation is prevented. The dynamic change of aggregate charge was verified by zeta-potential measurements. The elevation of salt concentration over several orders of magnitude retards aggregation dynamics, since attractive interparticle forces are diminished by an electrostatic double layer. This indicates that heteroaggregation induced by attractive interparticle forces is faster than aggregation

  6. Influence of flow velocity on biofilm growth in a tubular heat exchanger-condenser cooled by seawater.

    PubMed

    Trueba, Alfredo; García, Sergio; Otero, Félix M; Vega, Luis M; Madariaga, Ernesto

    2015-01-01

    The influence of flow velocity (FV) on the heat transfer process in tubes made from AISI 316L stainless steel in a heat exchanger-condenser cooled by seawater was evaluated based on the characteristics of the resulting biofilm that adhered to the internal surface of the tubes at velocities of 1, 1.2, 1.6, and 3 m s(-1). The results demonstrated that at a higher FV, despite being more compact and consistent, the biofilm was thinner with a lower concentration of solids, and smoother, which favoured the heat transfer process within the equipment. However, higher velocities increase the initial cost of the refrigerating water-pumping equipment and its energy consumption cost to compensate for the greater pressure drops produced in the tube. The velocity of 1.6 m s(-1) represented the equilibrium between the advantages and disadvantages of the variables analysed for the test conditions in this study.

  7. A Study on Bubble Departure and Bubble Lift-Off in Sub-Cooled Nucleate Boiling Flows

    SciTech Connect

    Wu, Wen; Chen, Peipei; Jones, Barclay G.; Newell, Ty A.

    2006-07-01

    This research examines bubble departure and bubble lift-off phenomena under subcooled nucleate boiling condition, using a high fidelity digital imaging apparatus. Refrigerant R- 134a is chosen as a simulant fluid due to its merits of having smaller surface tension, reduced latent heat, and lower boiling temperature than water. Images at frame rates up to 4000 frames/s were obtained with varying experimental parameters e.g. pressure, inlet sub-cooled level, and flow rate, etc., showing characteristics of bubble behavior under different conditions. Bubble size and position information was calculated via Canny's algorithm for edge detection and Fitzgibbon's algorithm for ellipse fitting. Bubble departure and lift-off radiuses were obtained and compared with existing bubble forces and detachment models proposed by Thorncroft et al., with good agreement observed. (authors)

  8. Influence of flow velocity on biofilm growth in a tubular heat exchanger-condenser cooled by seawater.

    PubMed

    Trueba, Alfredo; García, Sergio; Otero, Félix M; Vega, Luis M; Madariaga, Ernesto

    2015-01-01

    The influence of flow velocity (FV) on the heat transfer process in tubes made from AISI 316L stainless steel in a heat exchanger-condenser cooled by seawater was evaluated based on the characteristics of the resulting biofilm that adhered to the internal surface of the tubes at velocities of 1, 1.2, 1.6, and 3 m s(-1). The results demonstrated that at a higher FV, despite being more compact and consistent, the biofilm was thinner with a lower concentration of solids, and smoother, which favoured the heat transfer process within the equipment. However, higher velocities increase the initial cost of the refrigerating water-pumping equipment and its energy consumption cost to compensate for the greater pressure drops produced in the tube. The velocity of 1.6 m s(-1) represented the equilibrium between the advantages and disadvantages of the variables analysed for the test conditions in this study. PMID:26222187

  9. RX J1821.6+6827: A cool cluster at z = 0.81 from the ROSAT NEP survey

    NASA Astrophysics Data System (ADS)

    Gioia, I. M.; Wolter, A.; Mullis, C. R.; Henry, J. P.; Böhringer, H.; Briel, U. G.

    2004-12-01

    We present an analysis of the properties of the cluster of galaxies RX J1821.6+6827, or NEP 5281, at a redshift z= 0.816 ±0.001. RX J1821.6+6827 was discovered during the optical identification of the X-ray sources in the North Ecliptic Pole (NEP) region of the ROSAT All-Sky Survey and it is the highest redshift cluster of galaxies of the NEP survey. We have measured spectroscopic redshifts for twenty cluster galaxies using the Keck-I and the Canada-France-Hawai'i (CFH) telescopes. The value for the cluster velocity dispersion is σV=775+182-113 km s-1. The cluster was also observed by XMM-Newton. Both the optical and X-ray data are presented in this paper. The cluster has an unabsorbed X-ray flux in the 2-10 keV energy band of F2{-10 keV} = 1.24+0.16-0.23 ×10-13 erg cm-2 s-1 and a K-corrected luminosity in the same band of L2{-10 keV} = 6.32-0.73+0.76 ×1044 h-250 erg s-1 (90% confidence level). The cluster X-ray bolometric luminosity is LBOL,X = 1.35+0.08-0.21 ×1045 h50-2 erg s-1 (LBOL,X = 1.17+0.13-0.18 ×1045 h70-2 erg s-1 in the concordance cosmology). The data do not allow fitting both metal abundance and temperature at the same time. The abundance is unconstrained and can vary in the range 0.28-1.42 Z⊙ while the best fit X-ray temperature is T=4.7+1.2-0.7 keV. This emission weighted X-ray temperature is a little lower, barely within the uncertainties, than the predicted temperature, T= 6.34+0.13-0.35 keV, from the LX-TX relation of local clusters published in the literature. The optically measured velocity dispersion is consistent with the velocity dispersion expected from the &sigma/V-TX relationship. We also examine the point X-ray source RX J1821.9+6818, or NEP 5330, located to the south east of the cluster which was identified as a QSO at z= 1.692 ±0.008 in the ROSAT NEP survey. The X-ray source is well fitted by an absorbed power law model with NH=4.1-3.0+3.1×1020 atoms cm-2 and a photon index Γ=1.67±0.12 typical of an active galactic nucleus

  10. Data center cooling system

    DOEpatents

    Chainer, Timothy J; Dang, Hien P; Parida, Pritish R; Schultz, Mark D; Sharma, Arun

    2015-03-17

    A data center cooling system may include heat transfer equipment to cool a liquid coolant without vapor compression refrigeration, and the liquid coolant is used on a liquid cooled information technology equipment rack housed in the data center. The system may also include a controller-apparatus to regulate the liquid coolant flow to the liquid cooled information technology equipment rack through a range of liquid coolant flow values based upon information technology equipment temperature thresholds.

  11. Hybrid radiator cooling system

    DOEpatents

    France, David M.; Smith, David S.; Yu, Wenhua; Routbort, Jules L.

    2016-03-15

    A method and hybrid radiator-cooling apparatus for implementing enhanced radiator-cooling are provided. The hybrid radiator-cooling apparatus includes an air-side finned surface for air cooling; an elongated vertically extending surface extending outwardly from the air-side finned surface on a downstream air-side of the hybrid radiator; and a water supply for selectively providing evaporative cooling with water flow by gravity on the elongated vertically extending surface.

  12. An analytical study of the effect of coolant flow variables on the kinetic energy output of a cooled turbine blade flow

    NASA Technical Reports Server (NTRS)

    Prust, H. W., Jr.

    1971-01-01

    The results of an analytical study to determine the effect of changes in the amount, velocity, injection location, injection angle, and temperature of coolant flow on blade row performance are presented. The results show that the change in output of a cooled turbine blade row relative to the specific output of the uncooled blade row can be positive, negative, or zero. Comparisons between the analytical results and experimental results for four different cases of coolant discharge, all at a coolant temperature ratio of unity, show good agreement for three cases and rather poor agreement for the other. To further test the validity of the method, more experimental data is needed, particularly at different coolant temperature ratios.

  13. Cool Indonesian throughflow as a consequence of restricted surface layer flow.

    PubMed

    Gordon, Arnold L; Susanto, R Dwi; Vranes, Kevin

    2003-10-23

    Approximately 10 million m3 x s(-1) of water flow from the Pacific Ocean into the Indian Ocean through the Indonesian seas. Within the Makassar Strait, the primary pathway of the flow, the Indonesian throughflow is far cooler than estimated earlier, as pointed out recently on the basis of ocean current and temperature measurements. Here we analyse ocean current and stratification data along with satellite-derived wind measurements, and find that during the boreal winter monsoon, the wind drives buoyant, low-salinity Java Sea surface water into the southern Makassar Strait, creating a northward pressure gradient in the surface layer of the strait. This surface layer 'freshwater plug' inhibits the warm surface water from the Pacific Ocean from flowing southward into the Indian Ocean, leading to a cooler Indian Ocean sea surface, which in turn may weaken the Asian monsoon. The summer wind reversal eliminates the obstructing pressure gradient, by transferring more-saline Banda Sea surface water into the southern Makassar Strait. The coupling of the southeast Asian freshwater budget to the Pacific and Indian Ocean surface temperatures by the proposed mechanism may represent an important negative feedback within the climate system. PMID:14574409

  14. Study of heat transfer in a 7-element bundle cooled with the upward flow of supercritical Freon-12

    NASA Astrophysics Data System (ADS)

    Richards, Graham

    Experimental data on SuperCritical-Water (SCW) cooled bundles are very limited. Major problems with performing such experiments are: 1) small number of operating SCW experimental setups and 2) difficulties in testing and experimental costs at very high pressures, temperatures and heat fluxes. However, SuperCritical Water-cooled nuclear Reactor (SCWRs) designs cannot be finalized without such data. Therefore, as a preliminary approach experiments in SCW-cooled bare tubes and in bundles cooled with SC modeling fluids can be used. One of the SC modeling fluids typically used is Freon- 12 (R-12) where the critical pressure is 4.136 MPa and the critical temperature is 111.97ºC. These conditions correspond to a critical pressure of 22.064 MPa and critical temperature of 373.95ºC in water. A set of experimental data obtained in a Freon-12 cooled vertical bare bundle at the Institute of Physics and Power Engineering (IPPE, Obninsk, Russia) was analyzed. This set consisted of 20 cases of a vertically oriented 7-element bundle installed in a hexagonal flow channel. To secure the bundle in the flow channel 3 thin spacers were used. The dataset was obtained at equivalent parameters of the proposed SCWR concepts. Data was collected at pressures of about 4.65 MPa for several different combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. Heat fluxes ranged from 9 kW/m2 to 120 kW/m2 and mass fluxes ranged from 440 kg/m2s to 1320 kg/m2s. Also inlet temperatures ranged from 70ºC -- 120ºC. The test section consisted of fuel elements that were 9.5 mm in diameter with the total heated length of 1 m. Bulk-fluid and wall temperature profiles were recorded using a combination of 8 different thermocouples. The data was analyzed with respect to its temperature profile and heat transfer coefficient along the heated length of the test section. In a previous study it was confirmed that there is the existence of three distinct

  15. Tunable far-IR laser spectroscopy of jet-cooled carbon clusters: the nu 2 bending vibration of C3.

    PubMed

    Schmuttenmaer, C A; Cohen, R C; Pugliano, N; Heath, J R; Cooksy, A L; Busarow, K L; Saykally, R J

    1990-08-24

    Seven rovibrational transitions of the (01(1)0) <-- (00(0)0) fundamental bending band of C3 have been measured with high precision with the use of a tunable far-infrared laser spectrometer. The C3 molecules were produced by laser vaporization of a graphite rod and cooled in a supersonic expansion. The astrophysically important nu 2 fundamental frequency is determined to be 63.416529(40) cm-1. These measurements provide the basis for studies of C3 in the interstellar medium with far-infrared astronomy.

  16. The plasma protein fibrinogen stabilizes clusters of red blood cells in microcapillary flows

    NASA Astrophysics Data System (ADS)

    Brust, M.; Aouane, O.; Thiébaud, M.; Flormann, D.; Verdier, C.; Kaestner, L.; Laschke, M. W.; Selmi, H.; Benyoussef, A.; Podgorski, T.; Coupier, G.; Misbah, C.; Wagner, C.

    2014-03-01

    The supply of oxygen and nutrients and the disposal of metabolic waste in the organs depend strongly on how blood, especially red blood cells, flow through the microvascular network. Macromolecular plasma proteins such as fibrinogen cause red blood cells to form large aggregates, called rouleaux, which are usually assumed to be disaggregated in the circulation due to the shear forces present in bulk flow. This leads to the assumption that rouleaux formation is only relevant in the venule network and in arterioles at low shear rates or stasis. Thanks to an excellent agreement between combined experimental and numerical approaches, we show that despite the large shear rates present in microcapillaries, the presence of either fibrinogen or the synthetic polymer dextran leads to an enhanced formation of robust clusters of red blood cells, even at haematocrits as low as 1%. Robust aggregates are shown to exist in microcapillaries even for fibrinogen concentrations within the healthy physiological range. These persistent aggregates should strongly affect cell distribution and blood perfusion in the microvasculature, with putative implications for blood disorders even within apparently asymptomatic subjects.

  17. Distributions of suprathermal ions near hot flow anomalies observed by RAPID aboard Cluster

    NASA Astrophysics Data System (ADS)

    Kecskeméty, K.; Erdős, G.; Facskó, G.; Tátrallyay, M.; Dandouras, I.; Daly, P.; Kudela, K.

    2006-01-01

    A series of events having signatures of hot flow anomalies (HFA) observed by the magnetic field, plasma, and energetic particle instruments aboard the Cluster spacecraft upstream of the Earth's bow shock in February-April 2003 are investigated. During this period, the separation of the four satellites (up to about 10,000 km) allowed determining the velocity of moving interplanetary plasma structures, which intersect the bow shock. About 50 candidates for HFA events were found and some statistical aspects are discussed. Two HFA events are analyzed in detail: one on 16 February 2003 at 10:48 UT with marked energetic ion signature and another on 7 March 2003 at 10:15 UT with a smaller increase. Both occurred in the vicinity of the bow shock, the plasma speed decreased, its flow deflected, its temperature increased, whereas a magnetic structure with rapidly changing field direction passed by and finally reached the bow shock. Both electrons and ions are accelerated; elevated fluxes of 28-68 keV ions appeared before and lasted longer than the HFA event as observed by all four RAPID instruments. The directional and pitch angle distributions of low-energy ions transformed into the plasma frame are discussed.

  18. Propagation characteristics of young hot flow anomalies near the bow shock: Cluster observations

    NASA Astrophysics Data System (ADS)

    Xiao, T.; Zhang, H.; Shi, Q. Q.; Zong, Q.-G.; Fu, S. Y.; Tian, A. M.; Sun, W. J.; Wang, S.; Parks, G. K.; Yao, S. T.; Rème, H.; Dandouras, I.

    2015-06-01

    Based on Cluster observations, the propagation velocities and normal directions of hot flow anomaly (HFA) boundaries upstream the Earth's bow shock are calculated. Twenty-one young HFAs, which have clear leading and trailing boundaries, were selected, and multispacecraft timing method considering errors was employed for the investigation. According to the difference in the propagation velocity of the leading and trailing edges, we categorized these events into three groups, namely, contracting, expanding, and stable events. The contraction speed is a few tens of kilometers per second for the contracting HFAs, and the expansion speed is tens to more than hundred kilometers per second for expanding events. For the stable events, the leading and trailing edges propagate at almost the same speed within the error range. We have further investigated what causes them to contract, expand, or stay stable by carefully calculating the thermal pressure of the young HFAs which have two distinct ion populations (solar wind beam and reflected flow). It is found that the extreme value of the sum of the magnetic and thermal pressure inside the HFAs compared with that of the nearest point outside of the leading edges is higher for expanding events and lower for contracting events, and there is no significant difference for the stable events, and the total pressure (sum of thermal, magnetic, and dynamic pressure) variation has a significant effect on the evolution for most (70%) of the HFAs, which implies that the pressure plays an important role in the evolution of young HFAs.

  19. Rotor cavity flow and heat transfer with inlet swirl and radial outflow of cooling air

    NASA Astrophysics Data System (ADS)

    Staub, F. W.

    1992-06-01

    To enhance the reliability of turbine disk life prediction, experimental verification is necessary for analytical tools which calculate the heat transfer and flow field coefficients in turbine-stator cavities. A full-scale model of the forward cavity of a typical aircraft gas turbine is utilized employing a high-molecular-weight gas (Refrigerant-12) at ambient temperature and pressure conditions to match the dimensionless parameters at engine conditions. A first-order comparison is given of the velocity distribution and disk heat transfer coefficients calculated by the measured values and a CFD code.

  20. Numerical Investigation of the Flow Dynamics and Evaporative Cooling of Water Droplets Impinging onto Heated Surfaces: An Effective Approach To Identify Spray Cooling Mechanisms.

    PubMed

    Chen, Jian-Nan; Zhang, Zhen; Xu, Rui-Na; Ouyang, Xiao-Long; Jiang, Pei-Xue

    2016-09-13

    Numerical investigations of the dynamics and evaporative cooling of water droplets impinging onto heated surfaces can be used to identify spray cooling mechanisms. Droplet impingement dynamics and evaporation are simulated using the presented numerical model. Volume-of-fluid method is used in the model to track the free surface. The contact line dynamics was predicted from a dynamic contact angle model with the evaporation rate predicted by a kinetic theory model. A species transport equation was solved in the gas phase to describe the vapor convection and diffusion. The numerical model was validated by experimental data. The physical effects including the contact angle hysteresis and the thermocapillary effect are analyzed to offer guidance for future numerical models of droplet impingement cooling. The effects of various parameters including surface wettability, surface temperature, droplet velocity, droplet size, and droplet temperature were numerically studied from the standpoint of spray cooling. The numerical simulations offer profound analysis and deep insight into the spray cooling heat transfer mechanisms. PMID:27531256

  1. Effect of local cooling on skin temperature and blood flow of men in Antarctica

    NASA Astrophysics Data System (ADS)

    Naidu, M.; Sachdeva, U.

    1993-12-01

    Alterations to the finger skin temperature (Tsk) and blood flow (FBF) before and after cold immersion on exposure to an Antarctic environment for 8 weeks were studied in 64 subjects. There was a significant fall in Tsk and increase in finger blood flow after 1 week of Antarctic exposure. The Tsk did not further change even after 8 weeks of stay in Antarctica but a significant increase in FBF was obtained after 8 weeks. The cold immersion test was performed at non-Antarctic and Antarctic conditions by immersing the hand for 2 min in 0 4° C cold water. In the non-Antarctic environment the Tsk and FBF dropped significantly ( P < 0.001) indicating a vasoconstriction response. Interestingly after 8 weeks of stay in Antarctic conditions, the skin temperature dropped ( P < 0.001) but the cold induced fall in FBF was inhibited. Based on these observations it may be hypothesized that continuous cold exposure in Antarctica results in vasodilatation, which overrides the stronger vasoactive response of acute cold exposure and thus prevents cold injuries.

  2. Transient convective structures in a cooled water layer in the presence of a drift flow and a surfactant

    NASA Astrophysics Data System (ADS)

    Reutov, V. P.; Rybushkina, G. V.

    2016-02-01

    The paper is concerned with three-dimensional convective structures arising in a water layer cooled from above and covered by an adsorbed insoluble surfactant. The water is subjected to a laminar drift flow produced by tangential stresses on a free surface. The surface diffusion of the surfactant are taken into account within the approximation of a nondeformable flat surface. After appropriate reformulation of standard equations governing gravity-capillary convection and surfactant concentration, the problem is solved numerically using a pseudospectral method employed in our previous work. Development of the convective structures with increasing Reynolds number, surfactant film elasticity, and layer thickness is studied. The minimal layer thickness is chosen taking into account the results of relevant laboratory experiments. The cell-to-roll transition is revealed in the thin layer with increasing Reynolds number. The role of dissipation due to the surfactant film is elucidated by comparison with purely gravitational convection. The turbulent convection arising in a thicker layer subjected to a laminar shear flow is examined. Disordered streets containing elongated cells and swirl-like motions are revealed. Images of the surface temperature and the perturbed surfactant concentration are compared.

  3. Investigating the Synthesis of Ligated Metal Clusters in Solution Using a Flow Reactor and Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Olivares, Astrid M.; Laskin, Julia; Johnson, Grant E.

    2014-09-18

    The scalable synthesis of subnanometer metal clusters containing an exact number of atoms is of interest due to the highly size-dependent catalytic, electronic and optical properties of these species. While significant research has been conducted on the batch preparation of clusters through reduction synthesis in solution, the processes of metal complex reduction as well as cluster nucleation, growth and post-reduction etching are still not well understood. Herein, we demonstrate a temperature-controlled flow reactor for studying cluster formation in solution at well-defined conditions. Employing this technique methanol solutions of a chloro(triphenylphosphine)gold precursor, 1,4-bis(diphenylphosphino)butane capping ligand and borane-tert-butylamine reducing agent were combined in a mixing tee and introduced into a heated capillary with an adjustable length. In this manner, the temperature dependence of the relative abundance of different ionic reactants, intermediates and products synthesized in real time was characterized using online mass spectrometry. A wide distribution of doubly and triply charged cationic gold clusters was observed as well as smaller singly charged metal-ligand complexes. The results demonstrate that temperature plays a crucial role in determining the relative population of cationic gold clusters and, in general, that higher temperature promotes the formation of doubly charged clusters and singly charged metal-ligand complexes while hindering the growth of triply charged clusters. Moreover, the distribution of clusters observed at elevated temperatures is found to be consistent with that obtained at longer reaction times at room temperature, thereby demonstrating that heating may be used to access cluster distributions characteristic of different stages of reduction synthesis in solution.

  4. Binding inhibition of type 1 fimbriae to human granulocytes: a flow cytometric inhibition assay using trivalent cluster mannosides.

    PubMed

    Horst, A K; Kötter, S; Lindhorst, T K; Ludwig, A; Brandt, E; Wagener, C

    2001-12-01

    The binding of type 1 fimbriae from Escherichia coli to vital human neutrophilic granulocytes was inhibited by synthetic trivalent cluster mannosides. Binding of type 1 fimbriae was measured in a flow cytometric assay. Based on the molarity of mannosyl residues, the clusters exceed the inhibitory potency of methyl alpha-D-mannoside by a factor of more than 1,000 and the inhibitory potency of p-nitrophenyl alpha-D-mannoside by a factor of more than 10. The inhibition studies indicate that the trivalent cluster mannosides are very potent inhibitors of the binding of type 1 fimbriae to human neutrophilic granulocytes. Based on their defined structure, cluster mannosides are well suited for characterizing the molecular interactions of mannose-sensitive fimbriae with their cell membrane receptors.

  5. Simulator test to study hot-flow problems related to a gas cooled reactor

    NASA Technical Reports Server (NTRS)

    Poole, J. W.; Freeman, M. P.; Doak, K. W.; Thorpe, M. L.

    1973-01-01

    An advance study of materials, fuel injection, and hot flow problems related to the gas core nuclear rocket is reported. The first task was to test a previously constructed induction heated plasma GCNR simulator above 300 kW. A number of tests are reported operating in the range of 300 kW at 10,000 cps. A second simulator was designed but not constructed for cold-hot visualization studies using louvered walls. A third task was a paper investigation of practical uranium feed systems, including a detailed discussion of related problems. The last assignment resulted in two designs for plasma nozzle test devices that could be operated at 200 atm on hydrogen.

  6. On using splitter plates and flow guide-vanes for battery module cooling

    NASA Astrophysics Data System (ADS)

    Ismailov, Kairat; Adair, Desmond; Massalin, Yerzhan; Bakenov, Zhumabay

    2016-03-01

    Thermal management of lithium-ion battery modules needs to be an integral part of the design process to guarantee that temperatures remain within a narrow optimal range. Also it is important to minimize uneven distribution of temperature throughout a battery module so as to enhance the battery life cycle, and, charge and discharge performances. This paper explores by simulation, the benefits of attaching thin surfaces extended into the near-wake of cylindrical lithium-ion cells, here termed integral wake splitters, and, of placing flow guide-vane in the vicinity of the near wake, regarding thermal management. When using the integral splitters it is found that the local Nusselt numbers in the very near wake of a single cylindrical cell are depressed and the temperature distribution within the cell was found to be reasonably constant. Similar results were found when the cells are in formation. Use of guide-vanes also show promise in maintaining constant temperature distributions throughout the module.

  7. Star and cluster formation in NGC 1275

    NASA Technical Reports Server (NTRS)

    Richer, Harvey B.; Crabtree, Dennis R.; Fabian, A. C.; Lin, D. N. C.

    1993-01-01

    Luminous, blue, and unresolved objects have been found by imaging the nuclear region of the central galaxy in the Perseus Cluster, NGC 1275. Stellar formation in a cooling flow in which gas clouds confined by weak magnetic fields are allowed to remain at low densities is favored. Cloud-cloud collisions and coagulation in the high cloud density environment at the center of the galaxy then causes some clouds to become gravitationally unstable and to form globular clusters.

  8. Kinetic-theory predictions of clustering instabilities in granular flows: beyond the small-Knudsen-number regime

    SciTech Connect

    Mitrano, Peter P.; Zenk, John R.; Benyahia, Sofiane; Galvin, Janine E.; Dahl, Steven R.; Hrenya, Christine M.

    2013-12-04

    In this work we quantitatively assess, via instabilities, a Navier–Stokes-order (small- Knudsen-number) continuum model based on the kinetic theory analogy and applied to inelastic spheres in a homogeneous cooling system. Dissipative collisions are known to give rise to instabilities, namely velocity vortices and particle clusters, for sufficiently large domains. We compare predictions for the critical length scales required for particle clustering obtained from transient simulations using the continuum model with molecular dynamics (MD) simulations. The agreement between continuum simulations and MD simulations is excellent, particularly given the presence of well-developed velocity vortices at the onset of clustering. More specifically, spatial mapping of the local velocity-field Knudsen numbers (Knu) at the time of cluster detection reveals Knu » 1 due to the presence of large velocity gradients associated with vortices. Although kinetic-theory-based continuum models are based on a small- Kn (i.e. small-gradient) assumption, our findings suggest that, similar to molecular gases, Navier–Stokes-order (small-Kn) theories are surprisingly accurate outside their expected range of validity.

  9. XMM-Newton Observations of the Cluster of Galaxies Sersic 159-03

    NASA Technical Reports Server (NTRS)

    Kaastra, J. S.; Ferrigno, C.; Tamura, T.; Paerels, F. B. S.; Peterson, J. R.; Mittaz, J. P. D.

    2000-01-01

    The cluster of galaxies Sersic 159-03 was observed with the XMM-Newton X-ray observatory as part of the Guaranteed Time program. X-ray spectra taken with the EPIC and RGS instruments show no evidence for the strong cooling flow derived from previous X-ray observations. There is a significant lack of cool gas below 1.5 keV as compared to standard isobaric cooling flow models. While the oxygen is distributed more or less uniformly over the cluster, iron shows a strong concentration in the center of the cluster, slightly offset from the brightness center but within the central cD galaxy. This points to enhanced type Ia supernova activity in the center of the cluster. There is also an elongated iron-rich structure ex- tending to the east of the cluster, showing the inhomogeneity of the iron distribution. Finally, the temperature drops rapidly beyond 4' from the cluster center.

  10. Fundamental Study of a Jet-in-Cross-Flow Interacting with a Vortex Generator for Film Cooling Applications

    NASA Technical Reports Server (NTRS)

    Zaman, Khairul; Rigby, David; Heidmann, James

    2009-01-01

    Results of an experimental study are presented on the effectiveness of a vortex generator (VG) in preventing lift-off of a jet-in-cross-flow (JICF). The study is pertinent to film-cooling applications and its relevance to NASA programs is first briefly discussed. In the experiment, the jet issues into the boundary layer at an angle of 20deg to the free-stream. The effect of a triangular, ramp-shaped VG is studied while varying its geometry and location. Detailed flow-field properties are obtained for a case in which the height of the VG and the diameter of the orifice are comparable to the approach boundary layer thickness. The VG produces a streamwise vortex pair with vorticity magnitude three times larger (and of opposite sense) than that found in the JICF alone. Such a VG appears to be most effective in keeping the jet attached to the wall. The effect of parametric variation is studied mostly from surveys ten diameters downstream from the orifice. Results over a range of jet-to-freestream momentum flux ratio (1

  11. Data center cooling method

    DOEpatents

    Chainer, Timothy J.; Dang, Hien P.; Parida, Pritish R.; Schultz, Mark D.; Sharma, Arun

    2015-08-11

    A method aspect for removing heat from a data center may use liquid coolant cooled without vapor compression refrigeration on a liquid cooled information technology equipment rack. The method may also include regulating liquid coolant flow to the data center through a range of liquid coolant flow values with a controller-apparatus based upon information technology equipment temperature threshold of the data center.

  12. Clustering instability of the spatial distribution of inertial particles in turbulent flows.

    PubMed

    Elperin, Tov; Kleeorin, Nathan; L'vov, Victor S; Rogachevskii, Igor; Sokoloff, Dmitry

    2002-09-01

    A theory of clustering of inertial particles advected by a turbulent velocity field caused by an instability of their spatial distribution is suggested. The reason for the clustering instability is a combined effect of the particles inertia and a finite correlation time of the velocity field. The crucial parameter for the clustering instability is the size of the particles. The critical size is estimated for a strong clustering (with a finite fraction of particles in clusters) associated with the growth of the mean absolute value of the particles number density and for a weak clustering associated with the growth of the second and higher moments. A new concept of compressibility of the turbulent diffusion tensor caused by a finite correlation time of an incompressible velocity field is introduced. In this model of the velocity field, the field of Lagrangian trajectories is not divergence free. A mechanism of saturation of the clustering instability associated with the particles collisions in the clusters is suggested. Applications of the analyzed effects to the dynamics of droplets in the turbulent atmosphere are discussed. An estimated nonlinear level of the saturation of the droplets number density in clouds exceeds by the orders of magnitude their mean number density. The critical size of cloud droplets required for cluster formation is more than 20 microm.

  13. Massive molecular gas flows in the a1664 brightest cluster galaxy

    SciTech Connect

    Russell, H. R.; McNamara, B. R.; Main, R. A.; Vantyghem, A. N.; Edge, A. C.; Wilman, R. J.; Nulsen, P. E. J.; Combes, F.; Salomé, P.; Fabian, A. C.; Murray, N.; Baum, S. A.; O'Dea, C. P.; Donahue, M.; Voit, G. M.; Oonk, J. B. R.; Tremblay, G. R.

    2014-03-20

    We report ALMA Early Science CO(1-0) and CO(3-2) observations of the brightest cluster galaxy (BCG) in A1664. The BCG contains 1.1 × 10{sup 10} M {sub ☉} of molecular gas divided roughly equally between two distinct velocity systems: one from –250 to +250 km s{sup –1} centered on the BCG's systemic velocity and a high-velocity system blueshifted by 570 km s{sup –1} with respect to the systemic velocity. The BCG's systemic component shows a smooth velocity gradient across the BCG center, suggestive of rotation about the nucleus. However, the mass and velocity structure are highly asymmetric and there is little star formation coincident with a putative disk. It may be an inflow of gas that will settle into a disk over several 10{sup 8} yr. The high-velocity system consists of two gas clumps, each ∼2 kpc across, located to the north and southeast of the nucleus. Each has a line of sight velocity spread of 250-300 km s{sup –1}. The velocity of the gas in the high-velocity system increases toward the BCG center and may be a massive flow into the nucleus. However, the velocity gradient is not smooth. These structures are also coincident with low optical-ultraviolet surface brightness regions, which could indicate dust extinction associated with each clump. The structure is complex, making a clear interpretation difficult, but if the dusty, molecular gas lies predominantly in front of the BCG, the blueshifted velocities would indicate an outflow. Based on the energy requirements, such a massive outflow would most likely be driven by the active galactic nucleus. A merger origin is unlikely but cannot be ruled out.

  14. Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow-through reconnection

    NASA Astrophysics Data System (ADS)

    Maynard, Nelson C.; Farrugia, Charles J.; Burke, William J.; Ober, Daniel M.; Mozer, Forrest S.; Rème, Henri; Dunlop, Malcolm; Siebert, Keith D.

    2012-10-01

    Compared to the dayside, dynamics on the flanks of the magnetopause are poorly understood. To help bridge this knowledge gap we analyzed Cluster plasma and field measurements acquired during a 90-min period on 20 November 2003 when Cluster crossed the magnetopause four times in the vicinity of the sash. MHD simulations provide a context for Cluster observations. Crossings were between the magnetosheath and an S-shaped plasma sheet, rather than to the open-field lobes of the magnetotail. Cluster encountered two regions of MHD-breaking differences between perpendicular ion velocities and E × B convection. Ion adiabatic expansion parameter (δi) calculations show that ion gyrotropy was not broken during an episode of strong Alfvén wave activity in the magnetosheath. However, gyrotropy was broken (δi > 1) during the fourth magnetopause crossing. In the magnetosheath, ion guiding-center motion was maintained but inertial effects associated with temporally varying electric fields are probable sources of velocity differences. Regarding the magnetopause crossing, the generalized Ohm's law limits possible sources for breaking ion gyrotropy to inertial forces and/or electron pressure gradients associated with a nearby reconnection event. We suggest that Cluster witnessed effects of a temporally varying and spatially limited, flow-through reconnection event between open mantle field lines from the two polar caps adding new closed flux to the LLBL at the sash. Future modeling of flank dynamics must consider inertial forces as significant drivers at the magnetopause and in the adjacent magnetosheath.

  15. Cluster Regime—The New Regime Of Flowing Of Gas-Liquid Mixture In Vertical Columns (Based On Experimental Data)

    NASA Astrophysics Data System (ADS)

    Ozerov, A. Yu.

    2010-03-01

    For the revealing of the reasons of occurrence of discrete volcanic explosions of basalt magma the Complex Apparatus for Modeling Basaltic Eruptions (CAMBE) has been developed. It consists of two major systems—modeling and recording. The device is 18 meters high. During experiments gas-saturated model liquid acts from the saturator to the vertical transparent hose in which arising two-phase structures and its kinetics are studied. The experiments resulted in detecting and describing a new, never before known, mode of gas-liquid two-phase flow in a vertical column—defined here as cluster regime, which is characterized by regular alteration of dense gas bubble clusters separated from each other by the liquid not containing free gas phase. The mechanism of the cluster regime formation is conditioned by the processes of blocking of the hose working section by one big bubble or several smaller ones. It has been demonstrated that liquid, bubble, cluster and slug regime are regularly sequential and present polymorphic modifications of gas-saturated liquids migrating within vertically oriented conduits. Analysis of data on explosions at volcanoes, given the obtained experimental data on the mechanism of this process, allows concluding that realization of cluster or slug regimes in volcanic crater produces basaltic explosions.

  16. Method for Calculation of Laminar Heat Transfer in Air Flow Around Cylinders of Arbitrary Cross Section (including Large Temperature Differences and Transpiration Cooling)

    NASA Technical Reports Server (NTRS)

    Eckert, E R; Livingood, John N B

    1953-01-01

    The solution of heat-transfer problems has become vital for many aeronautical applications. The shapes of objects to be cooled can often be approximated by cylinders of various cross sections with flow normal to the axis as, for instance heat transfer on gas-turbine blades and on air foils heated for deicing purposes. A laminar region always exists near the stagnation point of such objects. A method previously presented by E. R. G. Eckert permits the calculation of local heat transfer around the periphery of cylinders of arbitrary cross section in the laminar region for flow of a fluid with constant property values with an accuracy sufficient for engineering purposes. The method is based on exact solutions of the boundary-layer equations for incompressible wedge-type flow and on the postulate that at any point on the cylinder the boundary-layer growth is the same as that on a wedge with comparable flow conditions. This method is extended herein to take into account the influence of large temperature differences between the cylinder wall and the flow as well as the influence of transpiration cooling when the same medium as the outside flow is used as coolant.

  17. A scaling study of the natural circulation flow of the ex-vessel core catcher cooling system of EU-APR1400 for designing a scale-down test facility for design verification

    SciTech Connect

    Rhee, B. W.; Ha, K. S.; Park, R. J.; Song, J. H.; Revankar, S. T.

    2012-07-01

    In this paper a scaling study on the steady state natural circulation flow along the flow path of the ex vessel core catcher cooling system of EU-APR1400 is described, and the scaling criteria for reproducing the same steady state thermalhydraulic characteristics of the natural circulation flow as a prototype core catcher cooling system in the scale-down test facility are derived in terms of the down-comer pipe diameter and orifice resistance. (authors)

  18. Two side liquid-cooled and passively Q-switched disk oscillator with nanosheets in flowing CCl4

    NASA Astrophysics Data System (ADS)

    Nie, Rongzhi; She, Jiangbo; Li, Dongdong; Li, Fuli; Peng, Bo

    2016-09-01

    A passively Q-switched and two side liquid-cooled Nd:YAG disk oscillator is demonstrated, which is operated at a pump pulse width of 300 μs and a pump repetition rate of 10 Hz. The coolant flows over the two large surfaces of the disk and will be passed through by laser beam, so it can also serve as a saturable absorber. For the unmodulated laser, the pure CCl4 was employed as coolant and a plane output mirror of 15 % transmission was employed. The maximum output energy of 795 mJ is realized corresponding to the optical-optical efficiency of 27.4 % and the slope efficiency of 30 %; for the graphene Q-switched laser, the CCl4 with graphene nanosheets was employed as coolant and a plane output mirror of 40 % transmission was employed. The maximum output energy of 376 mJ is realized corresponding to the optical-optical efficiency of 13 % and the slope efficiency of 18 %. The maximum average Q-switching repetition rate is 385 kHz, and the minimum average pulse width is 116 ns; for the MoS2 Q-switched laser, the CCl4 with MoS2 nanosheets was employed as coolant and a plane output mirror of 30 % transmission was employed. The maximum output energy of 486 mJ is realized corresponding to the optical-optical efficiency of 17 % and the slope efficiency of 22 %.The maximum average Q-switching repetition rate is 470 kHz, and the minimum average pulse width is 137 ns.

  19. Searching for 300, 000 Degree Gas in the Core of the Phoenix Cluster with HST-COS

    NASA Astrophysics Data System (ADS)

    McDonald, Michael

    2013-10-01

    The high central density of the intracluster medium in some galaxy clusters suggests that the hot 10,000,000K gas should cool completely in less than a Hubble time. In these clusters, simple cooling models predict 100-1000 solar masses per year of cooling gas should fuel massive starbursts in the central galaxy. The fact that the typical central cluster galaxy is a massive, "red and dead" elliptical galaxy, with little evidence for a cool ISM, has led to the realization of the "cooling flow problem". It is now thought that mechanical feedback from the central supermassive blackhole, in the form of radio-blown bubbles, is offsetting cooling, leading to an exceptionally precise {residuals of less than 10 percent} balance between cooling and feedback in nearly every galaxy cluster in the local Universe. In the recently-discovered Phoenix cluster, where z=0.596, we observe an 800 solar mass per year starburst within the central galaxy which accounts for about 30 percent of the classical cooling prediction for this system. We speculate that this may represent the first "true" cooling flow, with the factor of 3 difference between cooling and star formation being attributed to star formation efficiency, rather than a problem with cooling. In order to test these predictions, we propose far-UV spectroscopic observations of the OVI 1032A emission line, which probes 10^5.5K gas, in the central galaxy of the Phoenix cluster. If detected at the expected levels, this would provide compelling evidence that the starburst is, indeed, fueled by runaway cooling of the intracluster medium, confirming the presence of the first, bonafide cooling flow.

  20. Flow visualization of film cooling with spanwise injection from a small array of holes and compound-angle injection from a large array

    NASA Technical Reports Server (NTRS)

    Russell, L. M.

    1978-01-01

    Film injection from discrete holes in a smooth, flat plate was studied for two configurations: (1) spanwise injection through a four hole staggered array; and (2) compound angle injection through a 49 hole staggered array. The ratio of boundary layer thicknesses to hole diameter and the Reynolds number were typical of gas turbine film cooling applications. Streaklines showing the motion of the injected air were obtained by photographing small, neutrally buoyant, helium-filled soap bubbles that followed the flow field.

  1. Effect of grazing flow on the acoustic impedance of Helmholtz resonators consisting of single and clustered orifices

    NASA Technical Reports Server (NTRS)

    Hersch, A. S.; Walker, B.

    1979-01-01

    A semiempirical fluid mechanical model is derived for the acoustic behavior of thin-walled single orifice Helmholtz resonators in a grazing flow environment. The incident and cavity sound fields are connected in terms of an orifice discharge coefficient whose values are determined experimentally using the two-microphone method. Measurements show that at high grazing flow speeds, acoustical resistance is almost linearly proportional to the grazing flow speed and almost independent of incident sound pressure. The corresponding values of reactance are much smaller and tend towards zero. For thicker-walled orifice plates, resistance and reactance were observed to be less sensitive to grazing flow as the ratio of plate thickness to orifice diameter increased. Loud tones were observed to radiate from a single orifice Helmholtz resonator due to interaction between the grazing flow shear layer and the resonator cavity. Measurements showed that the tones radiated at a Strouhal number equal to 0.26. The effects of grazing flow on the impedance of Helmholtz resonators consisting of clusters of orifices was also studied. In general, both resistance and reaction were found to be virtually independent of orifice relative spacing and number. These findings are valid with and without grazing flow.

  2. A 1010 Solar Mass Flow of Molecular Gas in the A1835 Brightest Cluster Galaxy

    NASA Astrophysics Data System (ADS)

    McNamara, B. R.; Russell, H. R.; Nulsen, P. E. J.; Edge, A. C.; Murray, N. W.; Main, R. A.; Vantyghem, A. N.; Combes, F.; Fabian, A. C.; Salome, P.; Kirkpatrick, C. C.; Baum, S. A.; Bregman, J. N.; Donahue, M.; Egami, E.; Hamer, S.; O'Dea, C. P.; Oonk, J. B. R.; Tremblay, G.; Voit, G. M.

    2014-04-01

    We report ALMA Early Science observations of the A1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect 5 × 1010 M ⊙ of molecular gas within 10 kpc of the BCG. Its ensemble velocity profile width of ~130 km s-1 FWHM is too narrow for the molecular clouds to be supported in the galaxy by dynamic pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. Roughly 1010 M ⊙ of molecular gas is projected 3-10 kpc to the northwest and to the east of the nucleus with line-of-sight velocities lying between -250 km s-1 and +480 km s-1 with respect to the systemic velocity. The high-velocity gas may be either inflowing or outflowing. However, the absence of high-velocity gas toward the nucleus that would be expected in a steady inflow, and its bipolar distribution on either side of the nucleus, are more naturally explained as outflow. Star formation and radiation from the active galactic nucleus (AGN) are both incapable of driving an outflow of this magnitude. The location of the high-velocity gas projected behind buoyantly rising X-ray cavities and favorable energetics suggest an outflow driven by the radio AGN. If so, the molecular outflow may be associated with a hot outflow on larger scales reported by Kirkpatrick and colleagues. The molecular gas flow rate of approximately 200 M ⊙ yr-1 is comparable to the star formation rate of 100-180 M ⊙ yr-1 in the central disk. How radio bubbles would lift dense molecular gas in their updrafts, how much gas will be lost to the BCG, and how much will return to fuel future star formation and AGN activity are poorly understood. Our results imply that radio-mechanical (radio-mode) feedback not only heats hot atmospheres surrounding elliptical galaxies and BCGs, but it is able to sweep higher density molecular gas away from their centers.

  3. Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow

    NASA Technical Reports Server (NTRS)

    Holden, M. S.; Rodriguez, K. M.; Nowak, R. J.

    1991-01-01

    Experimental studies are conducted to examine the utilization of transpiration cooling to reduce the peak-heating loads in areas of shock/shock interaction. Smooth and transpiration-cooled nosetip models, 12 inches in diameter, were employed in these studies, which focused on defining the pressure distributions and heat transfer in type III and IV interaction areas. Transpiration cooling was determined to significantly increase the size of the shock layer and to move the peak-heating point around the body. A transpiration-cooling rate of more than 30 percent of the freestream maximum flux did not lower the peak-heating level more than 10 percent, but the integrated heating loads were reduced.

  4. Design of Cooling Channels of Preburners for Small Liquid Rocket Engines with Computational Flow and Heat Transfer Analysis

    NASA Astrophysics Data System (ADS)

    Moon, In-Sang; Lee, Seon-Mi; Moon, Il-Yoon; Yoo, Jae-Han; Lee, Soo-Yong

    2011-09-01

    A series of computational analyses was performed to predict the cooling process by the cooling channel of preburners used for kerosene-liquid oxygen staged combustion cycle rocket engines. As an oxygen-rich combustion occurs in the kerosene fueled preburner, it is of great importance to control the wall temperature so that it does not exceed the critical temperature. However, since the heat transfer is proportional to the speed of fluid running inside the channel, the high heat transfer leads to a trade-off of pressure loss. For this reason, it is necessary to establish a certain criteria between the pressure loss and the heat transfer or the wall surface temperature. The design factors of the cooling channel were determined by the computational research, and a test model was manufactured. The test model was used for the hot fire tests to prove the function of the cooling mechanism, among other purposes.

  5. Development and Evaluation of an Externally Air-Cooled Low-Flow torch and the Attenuation of Space Charge and Matrix Effects in Inductively Coupled Plasma Mass Spectrometry

    SciTech Connect

    Praphairaksit, N.

    2000-09-12

    An externally air-cooled low-flow torch has been constructed and successfully demonstrated for applications in inductively coupled plasma mass spectrometry (ICP-MS). The torch is cooled by pressurized air flowing at {approximately}70 L/min through a quartz air jacket onto the exterior of the outer tube. The outer gas flow rate and operating RF forward power are reduced considerably. Although plasmas can be sustained at the operating power as low as 400 W with a 2 L/min of outer gas flow, somewhat higher power and outer gas flows are advisable. A stable and analytical useful plasma can be obtained at 850 W with an outer gas flow rate of {approximately}4 L/min. Under these conditions, the air-cooled plasma produces comparable sensitivities, doubly charged ion ratios, matrix effects and other analytical merits as those produced by a conventional torch while using significantly less argon and power requirements. Metal oxide ion ratios are slightly higher with the air-cooled plasma but can be mitigated by reducing the aerosol gas flow rate slightly with only minor sacrifice in analyte sensitivity. A methodology to alleviate the space charge and matrix effects in ICP-MS has been developed. A supplemental electron source adapted from a conventional electron impact ionizer is added to the base of the skimmer. Electrons supplied from this source downstream of the skimmer with suitable amount and energy can neutralize the positive ions in the beam extracted from the plasma and diminish the space charge repulsion between them. As a result, the overall ion transmission efficiency and consequent analyte ion sensitivities are significantly improved while other important analytical aspects, such as metal oxide ion ratio, doubly charged ion ratio and background ions remain relatively unchanged with the operation of this electron source. This technique not only improves the ion transmission efficiency but also minimizes the matrix effects drastically. The matrix-induced suppression

  6. Minerals produced during cooling and hydrothermal alteration of ash flow tuff from Yellowstone drill hole Y-5

    USGS Publications Warehouse

    Keith, T.E.C.; Muffler, L.J.P.

    1978-01-01

    A rhyolitic ash-flow tuff in a hydrothermally active area within the Yellowstone caldera was drilled in 1967, and cores were studied to determine the nature and distribution of primary and secondary mineral phases. The rocks have undergone a complex history of crystallization and hydrothermal alteration since their emplacement 600,000 years ago. During cooling from magmatic temperatures, the glassy groundmass underwent either devitrification to alkali feldspar + ??-cristobalite ?? tridymite or granophyric crystallization to alkali feldspar + quartz. Associated with the zones of granophyric crystallization are prismatic quartz crystals in cavities similar to those termed miarolitic in plutonic rocks. Vapor-phase alkali feldspar, tridymite, magnetite, and sporadic ??-cristobalite were deposited in cavities and in void spaces of pumice fragments. Subsequently, some of the vapor-phase alkali feldspar crystals were replaced by microcrystalline quartz, and the vapor-phase minerals were frosted by a coating of saccharoidal quartz. Hydrothermal minerals occur primarily as linings and fillings of cavities and fractures and as altered mafic phenocrysts. Chalcedony is the dominant mineral related to the present hydrothermal regime and occurs as microcrystalline material mixed with various amounts of hematite and goethite. The chalcedony displays intricate layering and was apparently deposited as opal from silica-rich water. Hematite and goethite also replace both mafic phenocrysts and vapor-phase magnetite. Other conspicuous hydrothermal minerals include montmorillonite, pyrite, mordenite, calcite, and fluorite. Clinoptilolite, erionite, illite, kaolinite, and manganese oxides are sporadic. The hydrothermal minerals show little correlation with temperature, but bladed calcite is restricted to a zone of boiling in the tuff and clearly was deposited when CO2 was lost during boiling. Fractures and breccias filled with chalcedony are common throughout Y-5 and may have been

  7. Dynamic ionic clusters with flowing electron bubbles from warm to hot dense iron along the Hugoniot curve.

    PubMed

    Dai, Jiayu; Kang, Dongdong; Zhao, Zengxiu; Wu, Yanqun; Yuan, Jianmin

    2012-10-26

    Complex structures of warm and hot dense matter are essential to understanding the behavior of materials in high energy density processes and provide new features of matter constitutions. Here, around a new unified first-principles determined Hugoniot curve of iron from the normal condensed condition up to 1 Gbar, the novel structures characterized by the ionic clusters with electron bubbles are found using quantum Langevin molecular dynamics. Subsistence of complex clusters can persist in the time scale of 50 fs dynamically with quantum flowing bubbles, which are produced by the interplay of Fermi electron degeneracy, the ionic coupling, and the dynamical nature. With the inclusion of those complicated features in quantum Langevin molecular dynamics, the present equation of states could serve as a first-principles based database in a wide range of temperatures and densities.

  8. Classical trajectory simulation of the cluster-atom association reaction I-Arn+I --> I2+nAr. II. Diffusion of captured iodine and evaporative cooling of I2

    NASA Astrophysics Data System (ADS)

    Hu, Xiche; Martens, Craig C.

    1993-12-01

    This is Part II of a series of papers in which we address the role of microscopic solvation in the association reaction between a free iodine atom and an iodine doped van der Waals cluster: I+I(Ar)n→I2+nAr. The influence of microscopic solvation on the I+I to I2 reactivity, reaction mechanism, energetics, and product energy partitioning is the major focus of our study. The overall reaction for I+I(Ar)12→I2+12Ar can be characterized by three fundamental processes: (1) capture of the incident iodine atom by the I(Ar)12 cluster; (2) diffusive migration of the captured I atom on the surface or in the interior of the cluster, leading ultimately to an encounter with the other I atom to form a highly excited I*2 molecule; (3) vibrational relaxation of the nascent I*2 product, leading to evaporative cooling and decomposition of the cluster. Part I [J. Chem. Phys. 98, 8551 (1993)] dealt with the capture process. This article focuses on the chemical dynamics of the subsequent processes of diffusion, vibrational energy transfer, and evaporative cooling. The stabilization of the chemically activated I*2 molecule through evaporative cooling eliminate the need of a third body collision as required in isolation gas phase recombination. The overall distribution of final energies is nonstatistical for the chemically activated I*2Arn. The final vibrational energy of I2 exhibits a nonthermal structure even after all the argon atoms are evaporated. In addition to monoatomic sequential evaporation, a ``fissioning'' mechanism, leading to the formation of at least one multiatom fragment, is observed. The relationship between structure and dynamics is explored. The dynamics of vibrational relaxation, diffusion of the captured iodine, evaporation, and fragmentation pattern, final I2 energy partitioning are found to be strongly dependent upon structure and temperature of the doped cluster. A spectroscopic experimental verification of the above observations is also proposed.

  9. Evaporative Cooling Membrane Device

    NASA Technical Reports Server (NTRS)

    Lomax, Curtis (Inventor); Moskito, John (Inventor)

    1999-01-01

    An evaporative cooling membrane device is disclosed having a flat or pleated plate housing with an enclosed bottom and an exposed top that is covered with at least one sheet of hydrophobic porous material having a thin thickness so as to serve as a membrane. The hydrophobic porous material has pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to allow passage of the fluid in its vapor state, thereby, causing the evaporation of the fluid and the cooling of the remaining fluid. The fluid has a predetermined flow rate. The evaporative cooling membrane device has a channel which is sized in cooperation with the predetermined flow rate of the fluid so as to produce laminar flow therein. The evaporative cooling membrane device provides for the convenient control of the evaporation rates of the circulating fluid by adjusting the flow rates of the laminar flowing fluid.

  10. Investigation of heat transfer and flow using ribs within gas turbine blade cooling passage: Experimental and hybrid LES/RANS modeling

    NASA Astrophysics Data System (ADS)

    Kumar, Sourabh

    Gas turbines are extensively used for aircraft propulsion, land based power generation and various industrial applications. Developments in innovative gas turbine cooling technology enhance the efficiency and power output, with an increase in turbine rotor inlet temperatures. These advancements of turbine cooling have allowed engine design to exceed normal material temperature limits. For internal cooling design, techniques for heat extraction from the surfaces exposed to hot stream are based on the increase of heat transfer areas and on promotion of turbulence of the cooling flow. In this study, it is obtained by casting repeated continuous V and broken V shaped ribs on one side of the two pass square channel into the core of blade. Despite extensive research on ribs, only few papers have validated the numerical data with experimental results in two pass channel. In the present study, detailed experimental investigation is carried out for two pass square channels with 180° turn. Detailed heat transfer distribution occurring in the ribbed passage is reported for steady state experiment. Four different combinations of 60° and Broken 60° V ribs in channel are considered. Thermocouples are used to obtain the temperature on the channel surface and local heat transfer coefficients are obtained for various Reynolds numbers, within the turbulent flow regime. Area averaged data are calculated in order to compare the overall performance of the tested ribbed surface and to evaluate the degree of heat transfer enhancement induced by the ribs with. Flow within the channels is characterized by heat transfer enhancing ribs, bends, rotation and buoyancy effects. Computational Fluid Dynamics (CFD) simulations were carried out for the same geometries using different turbulence models such as k-o Shear stress transport (SST) and Reynolds stress model (RSM). These CFD simulations were based on advanced computing in order to improve the accuracy of three dimensional metal

  11. REACTOR COOLING

    DOEpatents

    Quackenbush, C.F.

    1959-09-29

    A nuclear reactor with provisions for selectively cooling the fuel elements is described. The reactor has a plurality of tubes extending throughout. Cylindrical fuel elements are disposed within the tubes and the coolant flows through the tubes and around the fuel elements. The fuel elements within the central portion of the reactor are provided with roughened surfaces of material. The fuel elements in the end portions of the tubes within the reactor are provlded with low conduction jackets and the fuel elements in the region between the central portion and the end portions are provided with smooth surfaces of high heat conduction material.

  12. Estimate of the Total Mechanical Feedback Energy from Galaxy Cluster-centered Black Holes: Implications for Black Hole Evolution, Cluster Gas Fraction, and Entropy

    NASA Astrophysics Data System (ADS)

    Mathews, William G.; Guo, Fulai

    2011-09-01

    The total feedback energy injected into hot gas in galaxy clusters by central black holes can be estimated by comparing the potential energy of observed cluster gas profiles with the potential energy of non-radiating, feedback-free hot gas atmospheres resulting from gravitational collapse in clusters of the same total mass. Feedback energy from cluster-centered black holes expands the cluster gas, lowering the gas-to-dark-matter mass ratio below the cosmic value. Feedback energy is unnecessarily delivered by radio-emitting jets to distant gas far beyond the cooling radius where the cooling time equals the cluster lifetime. For clusters of mass (4-11) × 1014 M sun, estimates of the total feedback energy, (1-3) × 1063 erg, far exceed feedback energies estimated from observations of X-ray cavities and shocks in the cluster gas, energies gained from supernovae, and energies lost from cluster gas by radiation. The time-averaged mean feedback luminosity is comparable to those of powerful quasars, implying that some significant fraction of this energy may arise from the spin of the black hole. The universal entropy profile in feedback-free gaseous atmospheres in Navarro-Frenk-White cluster halos can be recovered by multiplying the observed gas entropy profile of any relaxed cluster by a factor involving the gas fraction profile. While the feedback energy and associated mass outflow in the clusters we consider far exceed that necessary to stop cooling inflow, the time-averaged mass outflow at the cooling radius almost exactly balances the mass that cools within this radius, an essential condition to shut down cluster cooling flows.

  13. Regeneratively cooled transition duct with transversely buffered impingement nozzles

    SciTech Connect

    Morrison, Jay A; Lee, Ching-Pang; Crawford, Michael E

    2015-04-21

    A cooling arrangement (56) having: a duct (30) configured to receive hot gases (16) from a combustor; and a flow sleeve (50) surrounding the duct and defining a cooling plenum (52) there between, wherein the flow sleeve is configured to form impingement cooling jets (70) emanating from dimples (82) in the flow sleeve effective to predominately cool the duct in an impingement cooling zone (60), and wherein the flow sleeve defines a convection cooling zone (64) effective to cool the duct solely via a cross-flow (76), the cross-flow comprising cooling fluid (72) exhausting from the impingement cooling zone. In the impingement cooling zone an undimpled portion (84) of the flow sleeve tapers away from the duct as the undimpled portion nears the convection cooling zone. The flow sleeve is configured to effect a greater velocity of the cross-flow in the convection cooling zone than in the impingement cooling zone.

  14. Analysis of Regen Cooling in Rocket Combustors

    NASA Technical Reports Server (NTRS)

    Harper, Brent (Technical Monitor); Merkle, C. L.; Li, D.; Sankaran, V.

    2004-01-01

    The use of detailed CFD modeling for the description of cooling in rocket chambers is discussed. The overall analysis includes a complete three-dimensional analysis of the flow in the regenerative cooling passages, conjugate heat transfer in the combustor walls, and the effects of film cooling on the inside chamber. The results in the present paper omit the effects of film cooling and include only regen cooling and the companion conjugate heat transfer. The hot combustion gases are replaced by a constant temperature wall boundary condition. Load balancing for parallel cluster computations is ensured by using single-block unstructured grids for both fluids and solids, and by using a 'multiple physical zones' to account for differences in the number of equations. Validation of the method is achieved by comparing simple two-dimensional solutions with analytical results. Representative results for cooling passages are presents showing the effects of heat conduction in the copper walls with tube aspect ratios of 1.5:l.

  15. Turbine blade cooling

    DOEpatents

    Staub, F.W.; Willett, F.T.

    1999-07-20

    A turbine rotor blade comprises a shank portion, a tip portion and an airfoil. The airfoil has a pressure side wall and a suction side wall that are interconnected by a plurality of partition sidewalls, defining an internal cooling passageway within the airfoil. The internal cooling passageway includes at least one radial outflow passageway to direct a cooling medium flow from the shank portion towards the tip portion and at least one radial inflow passageway to direct a cooling medium flow from the tip portion towards the shank portion. A number of mixing ribs are disposed on the partition sidewalls within the radial outflow passageways so as to enhance the thermal mixing of the cooling medium flow, thereby producing improved heat transfer over a broad range of the Buoyancy number. 13 figs.

  16. Turbine blade cooling

    DOEpatents

    Staub, Fred Wolf; Willett, Fred Thomas

    2000-01-01

    A turbine rotor blade comprises a shank portion, a tip portion and an airfoil. The airfoil has a pressure side wall and a suction side wall that are interconnected by a plurality of partition sidewalls, defining an internal cooling passageway within the airfoil. The internal cooling passageway includes at least one radial outflow passageway to direct a cooling medium flow from the shank portion towards the tip portion and at least one radial inflow passageway to direct a cooling medium flow from the tip portion towards the shank portion. A number of mixing ribs are disposed on the partition sidewalls within the radial outflow passageways so as to enhance the thermal mixing of the cooling medium flow, thereby producing improved heat transfer over a broad range of the Buoyancy number.

  17. Turbine blade cooling

    DOEpatents

    Staub, Fred Wolf; Willett, Fred Thomas

    1999-07-20

    A turbine rotor blade comprises a shank portion, a tip portion and an airfoil. The airfoil has a pressure side wall and a suction side wall that are interconnected by a plurality of partition sidewalls, defining an internal cooling passageway within the airfoil. The internal cooling passageway includes at least one radial outflow passageway to direct a cooling medium flow from the shank portion towards the tip portion and at least one radial inflow passageway to direct a cooling medium flow from the tip portion towards the shank portion. A number of mixing ribs are disposed on the partition sidewalls within the radial outflow passageways so as to enhance the thermal mixing of the cooling medium flow, thereby producing improved heat transfer over a broad range of the Buoyancy number.

  18. A Giant Metrewave Radio Telescope/Chandra view of IRAS 09104+4109: a type 2 QSO in a cooling flow

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Ewan; Giacintucci, Simona; Babul, Arif; Raychaudhury, Somak; Venturi, Tiziana; Bildfell, Chris; Mahdavi, Andisheh; Oonk, J. B. R.; Murray, Norman; Hoekstra, Henk; Donahue, Megan

    2012-08-01

    IRAS 09104+4109 is a rare example of a dust enshrouded type 2 quasi-stellar object (QSO) in the centre of a cool-core galaxy cluster. Previous observations of this z = 0.44 system showed that, as well as powering the hyperluminous infrared emission of the cluster-central galaxy, the QSO is associated with a double-lobed radio source. However, the steep radio spectral index and misalignment between the jets and ionized optical emission suggested that the orientation of the QSO had recently changed. We use a combination of new, multiband Giant Metrewave Radio Telescope observations and archival radio data to confirm that the jets are no longer powered by the QSO, and estimate their age to be 120-160 Myr. This is in agreement with the ˜70-200 Myr age previously estimated for star formation in the galaxy. Previously unpublished Very Long Baseline Array data reveal a 200 pc scale double radio source in the galaxy core which is more closely aligned with the current QSO axis and may represent a more recent period of jet activity. These results suggest that the realignment of the QSO, the cessation of jet activity and the onset of rapid star formation may have been caused by a gas-rich galaxy merger. X-ray observations reveal a spiral structure in the intracluster medium (ICM) which suggests that the cluster is in the process of relaxation after a tidal encounter or merger with another system; such a merger could provide a mechanism for transporting a gas-rich galaxy into the cluster core without stripping its cold gas. A Chandra X-ray observation confirms the presence of cavities associated with the radio jets, and we estimate the energy required to inflate them to be ˜7.7 ×1060 erg. The mechanical power of the jets is sufficient to balance radiative cooling in the cluster, provided that they are efficiently coupled to the ICM. We find no evidence of direct radiative heating and conclude that the QSO either lacks the radiative luminosity to heat the ICM, or that it

  19. Properties of The Brightest Cluster Galaxy and Its Host Cluster

    NASA Astrophysics Data System (ADS)

    Katayama, H.; Hayashida, K.; Takahara, F.

    2001-09-01

    We investigate the relation between the brightest cluster galaxy (BCG) and its host cluster. A BCG is a bright and massive elliptical galaxy in a cluster of galaxies. The luminosity of a BCG is 10 times larger than that of normal field galaxy and the mass of a BCG is about 1013Msolar which corresponds to that of galaxy group. In order to explain the origin of BCGs, the following three models are proposed: (1) star formation from cooling flow. In this model, intracluster gas gradually condenses at the center of the cluster and forms the BCG. (2) ``Galactic cannibalism'' or the accretion of smaller galaxies. In this model, dynamical friction accounts for the formation of the BCG. These two models predict the BCG evolves with the evolution of cluster. (3) Galaxy merging in the early history of the formation of the cluster. In this model, the property of BCGs is determined no later than cluster collapse. In any model, the formation of BCGs is related to the collapse and formation of its host cluster. The relation between the BCG and its host cluster was studied by Edge (1991). Edge (1991) found that the optical luminosity of the BCG is positively correlated with the X-ray luminosity and temperature of its host cluster. Edge (1991) concludes that these correlations indicate that the BCG responds to the overall cluster properties. In order to investigate the other relation between the BCG and its host cluster, we analyzed ROSAT archival data and compared the displacement between the X-ray peak and the BCG with the Z parameter of the fundamental relation found by Fujita and Takahara (1999). It is found that the displacement is larger with decreasing Z. Furthermore, the large Z clusters tend to have a regular X-ray profile, which implies a relaxed system. The fundamental parameter Z depends mainly on the virial density ρvir, and is considered to be related to the formation epoch of the cluster, i.e., large Z clusters are old clusters and small Z clusters are young

  20. Investigation of Advanced Counterrotation Blade Configuration Concepts for High Speed Turboprop Systems. Task 8: Cooling Flow/heat Transfer Analysis

    NASA Technical Reports Server (NTRS)

    Hall, Edward J.; Topp, David A.; Heidegger, Nathan J.; Delaney, Robert A.

    1994-01-01

    The focus of this task was to validate the ADPAC code for heat transfer calculations. To accomplish this goal, the ADPAC code was modified to allow for a Cartesian coordinate system capability and to add boundary conditions to handle spanwise periodicity and transpiration boundaries. The primary validation case was the film cooled C3X vane. The cooling hole modeling included both a porous region and grid in each discrete hold. Predictions for these models as well as smooth wall compared well with the experimental data.

  1. Optimum Conditions for the Efficacy and Safety of Cryofiltration Apheresis: An Analysis of Circuit Temperatures Depending on Plasma Flow Rate and Cooling Coil Lengths/Turns.

    PubMed

    Nakajima, Hirofumi; Kaneko, Shuzo; Sato, Yukihiro; Takano, Tomoo; Hosino, Toshihisa

    2015-08-01

    A system providing both appropriate cooling and warming are needed for the efficacy and safety of cryofiltration (CF) plasmapheresis. We measured some points of CF circuit temperatures with varying plasma flow rates (QP  = 10-40 mL/min) and the numbers of connecting cooling coils (one or two) under the conditions of blood flow rate (QB ) 100 mL/min with 7700-mm coil length, 19 turns, and 50-mL priming volume. We measured the respective temperatures of each point of starting/returning for an extracorporeal circuit (TA /TV ), intracooling coil (TC ), and post-plasma fractionator (PF) (TPF ). The subtraction of TV from TA (ΔT) was used as an indicator of safe return. There were no significant differences in TC , TPF , or ΔT in accordance with each QP between that of one and two coils. All of the Tc values under the condition QP  ≤ 20 mL/min achieved <4°C. The TPF under the condition QP  ≥ 20 mL/min was not significantly different compared to that of QP 30 mL/min (the lowest condition). Although the ΔT increased depending on the QP increase, the ΔT under the condition QP  ≤ 15 mL/min was not significantly different from that of the control (one-way double-filtration plasmapheresis [DFPP]) group. We conclude that (i) one coil is enough for effective cooling in CF, and (ii) an ideal QP that fulfills the required conditions for both effective cooling and sufficient warming of returning fluid does not exist, but QP from 15 to 20 mL/min may be a relevant range.

  2. Idaho National Laboratory Experimental Program to Measure the Flow Phenomena in a Scaled Model of a Prismatic Gas-Cooled Reactor Lower Plenum for Validation of CFD Codes

    SciTech Connect

    Hugh M. McIlroy Jr.; Donald M. McEligot; Robert J. Pink

    2008-09-01

    The experimental program that is being conducted at the Matched Index-of-Refraction (MIR) Flow Facility at Idaho National Laboratory (INL) to obtain benchmark data on measurements of flow phenomena in a scaled model of a prismatic gas-cooled reactor lower plenum using 3-D Particle Image Velocimetry (PIV) is presented. A description of the scaling analysis, experimental facility, 3-D PIV system, measurement uncertainties and analysis, experimental procedures and samples of the data sets that have been obtained are included. Samples of the data set that will be presented include mean-velocity-field and turbulence data in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor (GCR) similar to a General Atomics Gas-Turbine-Modular Helium Reactor (GTMHR) design. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. The flow in the lower plenum consists of multiple jets injected into a confined cross flow - with obstructions. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to approximate flow scaled to that expected from the staggered parallel rows of posts in the reactor design. The model is fabricated from clear, fused quartz to match the refractive-index of the mineral oil working fluid. The benefit of the MIR technique is that it permits high-quality measurements to be obtained without locating intrusive transducers that disturb the flow field and without distortion of the optical paths. An advantage of the INL MIR system is its large size which allows improved spatial and temporal resolution compared to similar facilities at smaller scales. Results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). Inlet jet Reynolds numbers (based on the jet diameter and the time-mean average flow rate) are approximately 4,300 and 12,400. The measurements

  3. Instantaneous and time-averaged flow structures around a blunt double-cone with or without supersonic film cooling visualized via nano-tracer planar laser scattering

    NASA Astrophysics Data System (ADS)

    Zhu, Yang-Zhu; Yi, Shi-He; He, Lin; Tian, Li-Feng; Zhou, Yong-Wei

    2013-01-01

    In a Mach 3.8 wind tunnel, both instantaneous and time-averaged flow structures of different scales around a blunt double-cone with or without supersonic film cooling were visualized via nano-tracer planar laser scattering (NPLS), which has a high spatiotemporal resolution. Three experimental cases with different injection mass flux rates were carried out. Many typical flow structures were clearly shown, such as shock waves, expansion fans, shear layers, mixing layers, and turbulent boundary layers. The analysis of two NPLS images with an interval of 5 μs revealed the temporal evolution characteristics of flow structures. With matched pressures, the laminar length of the mixing layer was longer than that in the case with a larger mass flux rate, but the full covered region was shorter. Structures like K—H (Kelvin—Helmholtz) vortices were clearly seen in both flows. Without injection, the flow was similar to the supersonic flow over a backward-facing step, and the structures were relatively simpler, and there was a longer laminar region. Large scale structures such as hairpin vortices were visualized. In addition, the results were compared in part with the schlieren images captured by others under similar conditions.

  4. Experimental analysis and computer simulation on stability margin and quench behaviour in a NbTi forced-flow cooled winding pack

    NASA Astrophysics Data System (ADS)

    Balsamo, E. P.; Bottura, L.; Cicchelli, O.; Gislon, P.; Ricci, M.; Spadoni, M.

    1994-07-01

    A significant amount (over 70 runs) of experimental data on stability margin and quench behavior in a two-dimensional, forced-flow cooled NbTi winding pack has been collected. The measurements performed over a wide range of operating conditions (operating current, field, and temperature) have been used as the experimental data-base for the comparison with the results of the simulations done using the quench analysis code SARUMAN. Here we present the results of the experimental and validation activities, which show that SARUMAN can successfully predict stability margin and quench propagation in a 3-D winding.

  5. Reduced Fluorescence versus Forward Scatter Time-of-Flight and Increased Peak versus Integral Fluorescence Ratios Indicate Receptor Clustering in Flow Cytometry.

    PubMed

    Fürnrohr, Barbara G; Stein, Merle; Rhodes, Benjamin; Chana, Prabhjoat S; Schett, Georg; Vyse, Timothy J; Herrmann, Martin; Mielenz, Dirk

    2015-07-01

    Clustering of surface receptors is often required to initiate signal transduction, receptor internalization, and cellular activation. To study the kinetics of clustering, we developed an economic high-throughput method using flow cytometry. The quantification of receptor clustering by flow cytometry is based on the following two observations: first, the fluorescence signal length (FL time-of-flight [ToF]) decreases relative to the forward scatter signal length (FSc-ToF), and second, the peak FL (FL-peak) increases relative to the integral FL (FL-integral) upon clustering of FL-labeled surface receptors. Receptor macroclustering can therefore be quantified using the ratios FL-ToF/FSc-ToF (method ToF) or FL-peak/FL-integral (method Peak). We have used these methods to analyze clustering of two immune receptors known to undergo different conformational and oligomeric states: the BCR and the complement receptor 3 (CR3), on murine splenocytes, purified B cells, and human neutrophils. Engagement of both the BCR and CR3, on immortalized as well as primary murine B cells and human neutrophil, respectively, resulted in decreased FL-ToF/FSc-ToF and increased FL-peak/FL-integral ratios. Manipulation of the actin-myosin cytoskeleton altered BCR clustering which could be measured using the established parameters. To confirm clustering of CR3 on neutrophils, we applied imaging flow cytometry. Because receptor engagement is as a biological process dependent on cell viability, energy metabolism, and temperature, receptor clustering can only be quantified by gating on viable cells under physiological conditions. In summary, with this novel method, receptor clustering on nonadherent cells can easily be monitored by high-throughput conventional flow cytometry.

  6. A new Newton's law of cooling?

    PubMed

    Kleiber, M

    1972-12-22

    Several physiologists confuse Fourier's law of animal heat flow with Newton's law of cooling. A critique of this error in 1932 remained ineffective. In 1969 Molnar tested Newton's cooling law. In 1971 Strunk found Newtonian cooling unrealistic for animals. Unfortunately, he called the Fourier formulation of animal heat flow, requiring post-Newtonian observations, a "contemporary Newtonian law of cooling."

  7. Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow

    NASA Technical Reports Server (NTRS)

    Holden, Michael S.; Rodriguez, Kathleen M.

    1992-01-01

    A program of experimental research and analysis was conducted to examine the heat transfer and pressure distributions in regions of shock/shock interaction over smooth and transpiration-cooled hemispherical noseshapes. The objective of this investigation was to determine whether the large heat transfer generated in regions of shock/shock interaction can be reduced by transpiration cooling. The experimental program was conducted at Mach numbers of 12 to 16 in the Calspan 48-Inch Shock Tunnel. Type 3 and type 4 interaction regions were generated for a range of freestream unit Reynolds numbers to provide shear layer Reynolds numbers from 10 exp 4 to 10 exp 6 to enable laminar and turbulent interaction regions to be studied. Shock/shock interactions were investigated on a smooth hemispherical nosetip and a similar transpiration-cooled nosetip, with the latter configuration being examined for a range of surface blowing rates up to one-third of the freestream mass flux. While the heat transfer measurements on the smooth hemisphere without shock/shock interaction were in good agreement with Fay-Riddell predictions, those on the transpiration-cooled nosetip indicated that its intrinsic roughness caused heating-enhancement factors of over 1.5. In the shock/shock interaction studies on the smooth nosetip, detailed heat transfer and pressure measurements were obtained to map the variation of the distributions with shock-impingement position for a range of type 3 and type 4 interactions. Such sets of measurements were obtained for a range of unit Reynolds numbers and Mach numbers to obtain both laminar and turbulent interactions. The measurements indicated that shear layer transition has a significant influence on the heating rates for the type 4 interaction as well as the anticipated large effects on type 3 interaction heating. In the absence of blowing, the peak heating in the type 3 and type 4 interaction regions, over the transpiration-cooled model, did not appear to be

  8. Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow

    NASA Astrophysics Data System (ADS)

    Holden, Michael S.; Rodriguez, Kathleen M.

    1992-04-01

    A program of experimental research and analysis was conducted to examine the heat transfer and pressure distributions in regions of shock/shock interaction over smooth and transpiration-cooled hemispherical noseshapes. The objective of this investigation was to determine whether the large heat transfer generated in regions of shock/shock interaction can be reduced by transpiration cooling. The experimental program was conducted at Mach numbers of 12 to 16 in the Calspan 48-Inch Shock Tunnel. Type 3 and type 4 interaction regions were generated for a range of freestream unit Reynolds numbers to provide shear layer Reynolds numbers from 10 exp 4 to 10 exp 6 to enable laminar and turbulent interaction regions to be studied. Shock/shock interactions were investigated on a smooth hemispherical nosetip and a similar transpiration-cooled nosetip, with the latter configuration being examined for a range of surface blowing rates up to one-third of the freestream mass flux. While the heat transfer measurements on the smooth hemisphere without shock/shock interaction were in good agreement with Fay-Riddell predictions, those on the transpiration-cooled nosetip indicated that its intrinsic roughness caused heating-enhancement factors of over 1.5. In the shock/shock interaction studies on the smooth nosetip, detailed heat transfer and pressure measurements were obtained to map the variation of the distributions with shock-impingement position for a range of type 3 and type 4 interactions. Such sets of measurements were obtained for a range of unit Reynolds numbers and Mach numbers to obtain both laminar and turbulent interactions. The measurements indicated that shear layer transition has a significant influence on the heating rates for the type 4 interaction as well as the anticipated large effects on type 3 interaction heating. In the absence of blowing, the peak heating in the type 3 and type 4 interaction regions, over the transpiration-cooled model, did not appear to be

  9. Conceptual design of a forced-flow-cooled 20-kA current lead using Ag-alloy-sheathed Bi-2223 high-temperature superconductors

    SciTech Connect

    Heller, R.; Hull, J.R.

    1994-11-01

    The use of high-temperature superconductors in current leads to reduce refrigeration power has been investigated by many groups in the past. Most used YBCO and Bi-2212 bulk superconductors, although their critical current density is not very high. In this paper, BI-2223 HTSC tapes sheathed with Ag alloys are used in the design of a 20-kA current lead because of their higher critical current in medium magnetic fields. The lead current of 20 kA is related to the coil current of the planned stellarator WENDELSTEIN 7-X. Forced-now helium cooling has been used in the design, allowing position-independent and well-controlled operation. The design characteristics of the lead are presented and 4-K helium cooling of the whole lead, as well as 60-K helium cooling of the copper part of the lead, is discussed. The power consumption at zero current, and the lead`s behaviour in case of loss of coolant flow, are given, The results of the design allow extrapolation to current leads of the 50-kA range.

  10. Jet array impingement flow distributions and heat transfer characteristics. Effects of initial crossflow and nonuniform array geometry. [gas turbine engine component cooling

    NASA Technical Reports Server (NTRS)

    Florschuetz, L. W.; Metzger, D. E.; Su, C. C.; Isoda, Y.; Tseng, H. H.

    1982-01-01

    Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. The configurations considered are intended to model those of interest in current and contemplated gas turbine airfoil midchord cooling applications. The effects of an initial crossflow which approaches the array through an upstream extension of the channel are considered. Flow distributions as well as heat transfer coefficients and adiabatic wall temperatures resolved to one streamwise hole spacing were measured as a function of the initial crossflow rate and temperature relative to the jet flow rate and temperature. Both Nusselt number profiles and dimensionless adiabatic wall temperature (effectiveness) profiles are presented and discussed. Special test results which show a significant reduction of jet orifice discharge coefficients owing to the effect of a confined crossflow are also presented, along with a flow distribution model which incorporates those effects. A nonuniform array flow distribution model is developed and validated.

  11. Experimental heat transfer and flow results of a chordwise-finned turbine vane with impingement, film, and convection cooling

    NASA Technical Reports Server (NTRS)

    Gauntner, J. W.; Lane, J. M.; Dengler, R. P.; Hickel, R. O.

    1972-01-01

    Experimental heat transfer data are presented for a vane tested in a turbojet engine at turbine inlet gas temperatures to 1644 K (2500 F), coolant temperatures to 700 K (800 F), and coolant-to-gas flow ratios to 0.187. Methods are presented for correlating heat transfer data and obtaining coolant flow distribution through the vane. Calculated and measured coolant flow distributions and vane metal temperatures are compared.

  12. Power electronics cooling apparatus

    SciTech Connect

    Sanger, Philip Albert; Lindberg, Frank A.; Garcen, Walter

    2000-01-01

    A semiconductor cooling arrangement wherein a semiconductor is affixed to a thermally and electrically conducting carrier such as by brazing. The coefficient of thermal expansion of the semiconductor and carrier are closely matched to one another so that during operation they will not be overstressed mechanically due to thermal cycling. Electrical connection is made to the semiconductor and carrier, and a porous metal heat exchanger is thermally connected to the carrier. The heat exchanger is positioned within an electrically insulating cooling assembly having cooling oil flowing therethrough. The arrangement is particularly well adapted for the cooling of high power switching elements in a power bridge.

  13. CD33 monoclonal antibody conjugated Au cluster nano-bioprobe for targeted flow-cytometric detection of acute myeloid leukaemia

    NASA Astrophysics Data System (ADS)

    Retnakumari, Archana; Jayasimhan, Jasusri; Chandran, Parwathy; Menon, Deepthy; Nair, Shantikumar; Mony, Ullas; Koyakutty, Manzoor

    2011-07-01

    Protein stabilized gold nanoclusters (Au-NCs) are biocompatible, near-infrared (NIR) emitting nanosystems having a wide range of biomedical applications. Here, we report the development of a Au-NC based targeted fluorescent nano-bioprobe for the flow-cytometric detection of acute myeloid leukaemia (AML) cells. Au-NCs with ~ 25-28 atoms showing bright red-NIR fluorescence (600-750 nm) and average size of ~ 0.8 nm were prepared by bovine serum albumin assisted reduction-cum-stabilization in aqueous phase. The protein protected clusters were conjugated with monoclonal antibody against CD33 myeloid antigen, which is overexpressed in ~ 99.2% of the primitive population of AML cells, as confirmed by immunophenotyping using flow cytometry. Au-NC-CD33 conjugates having average size of ~ 12 nm retained bright fluorescence over an extended duration of ~ a year, as the albumin protein protects Au-NCs against degradation. Nanotoxicity studies revealed excellent biocompatibility of Au-NC conjugates, as they showed no adverse effect on the cell viability and inflammatory response. Target specificity of the conjugates for detecting CD33 expressing AML cells (KG1a) in flow cytometry showed specific staining of ~ 95.4% of leukaemia cells within 1-2 h compared to a non-specific uptake of ~ 8.2% in human peripheral blood cells (PBMCs) which are CD33low. The confocal imaging also demonstrated the targeted uptake of CD33 conjugated Au-NCs by leukaemia cells, thus confirming the flow cytometry results. This study demonstrates that novel nano-bioprobes can be developed using protein protected fluorescent nanoclusters of Au for the molecular receptor targeted flow cytometry based detection and imaging of cancer cells.

  14. Water cooled steam jet

    DOEpatents

    Wagner, Jr., Edward P.

    1999-01-01

    A water cooled steam jet for transferring fluid and preventing vapor lock, or vaporization of the fluid being transferred, has a venturi nozzle and a cooling jacket. The venturi nozzle produces a high velocity flow which creates a vacuum to draw fluid from a source of fluid. The venturi nozzle has a converging section connected to a source of steam, a diffuser section attached to an outlet and a throat portion disposed therebetween. The cooling jacket surrounds the venturi nozzle and a suction tube through which the fluid is being drawn into the venturi nozzle. Coolant flows through the cooling jacket. The cooling jacket dissipates heat generated by the venturi nozzle to prevent vapor lock.

  15. Water cooled steam jet

    DOEpatents

    Wagner, E.P. Jr.

    1999-01-12

    A water cooled steam jet for transferring fluid and preventing vapor lock, or vaporization of the fluid being transferred, has a venturi nozzle and a cooling jacket. The venturi nozzle produces a high velocity flow which creates a vacuum to draw fluid from a source of fluid. The venturi nozzle has a converging section connected to a source of steam, a diffuser section attached to an outlet and a throat portion disposed there between. The cooling jacket surrounds the venturi nozzle and a suction tube through which the fluid is being drawn into the venturi nozzle. Coolant flows through the cooling jacket. The cooling jacket dissipates heat generated by the venturi nozzle to prevent vapor lock. 2 figs.

  16. EFFECTS OF COMPTON COOLING ON OUTFLOW IN A TWO-COMPONENT ACCRETION FLOW AROUND A BLACK HOLE: RESULTS OF A COUPLED MONTE CARLO TOTAL VARIATION DIMINISHING SIMULATION

    SciTech Connect

    Garain, Sudip K.; Ghosh, Himadri; Chakrabarti, Sandip K. E-mail: himadri@bose.res.in

    2012-10-20

    We investigate the effects of cooling of the Compton cloud on the outflow formation rate in an accretion disk around a black hole. We carry out a time-dependent numerical simulation where both the hydrodynamics and the radiative transfer processes are coupled together. We consider a two-component accretion flow in which the Keplerian disk is immersed into an accreting low-angular momentum flow (halo) around a black hole. The soft photons which originate from the Keplerian disk are inverse-Comptonized by the electrons in the halo and the region between the centrifugal pressure supported shocks and the horizon. We run several cases by changing the rate of the Keplerian disk and see the effects on the shock location and properties of the outflow and the spectrum. We show that as a result of Comptonization of the Compton cloud, the cloud becomes cooler with the increase in the Keplerian disk rate. As the resultant thermal pressure is reduced, the post-shock region collapses and the outflow rate is also reduced. Since the hard radiation is produced from the post-shock region, and the spectral slope increases with the reduction of the electron temperature, the cooling produces softer spectrum. We thus find a direct correlation between the spectral states and the outflow rates of an accreting black hole.

  17. A study on the effect of various design parameters on the natural circulation flow rate of the ex-vessel core catcher cooling system of EU-APR1400

    SciTech Connect

    Rhee, B. W.; Ha, K. S.; Park, R. J.; Song, J. H.

    2012-07-01

    In this paper, a study on the effect of various design parameters such as the channel gap width, heat flux distribution, down-comer pipe size and two-phase flow slip ratio on the natural circulation flow rate is performed based on a physical model for a natural circulation flow along the flow path of the ex-vessel core catcher cooling system of an EU-APR1400, and these effects on the natural circulation flow rate are analyzed and compared with the minimum flow rate required for the safe operation of the system. (authors)

  18. Biophysical controls on cluster dynamics and architectural differentiation of microbial biofilms in contrasting flow environments.

    PubMed

    Hödl, Iris; Mari, Lorenzo; Bertuzzo, Enrico; Suweis, Samir; Besemer, Katharina; Rinaldo, Andrea; Battin, Tom J

    2014-03-01

    Ecology, with a traditional focus on plants and animals, seeks to understand the mechanisms underlying structure and dynamics of communities. In microbial ecology, the focus is changing from planktonic communities to attached biofilms that dominate microbial life in numerous systems. Therefore, interest in the structure and function of biofilms is on the rise. Biofilms can form reproducible physical structures (i.e. architecture) at the millimetre-scale, which are central to their functioning. However, the spatial dynamics of the clusters conferring physical structure to biofilms remains often elusive. By experimenting with complex microbial communities forming biofilms in contrasting hydrodynamic microenvironments in stream mesocosms, we show that morphogenesis results in 'ripple-like' and 'star-like' architectures--as they have also been reported from monospecies bacterial biofilms, for instance. To explore the potential contribution of demographic processes to these architectures, we propose a size-structured population model to simulate the dynamics of biofilm growth and cluster size distribution. Our findings establish that basic physical and demographic processes are key forces that shape apparently universal biofilm architectures as they occur in diverse microbial but also in single-species bacterial biofilms.

  19. Gas turbine cooling system

    SciTech Connect

    Bancalari, Eduardo E.

    2001-01-01

    A gas turbine engine (10) having a closed-loop cooling circuit (39) for transferring heat from the hot turbine section (16) to the compressed air (24) produced by the compressor section (12). The closed-loop cooling system (39) includes a heat exchanger (40) disposed in the flow path of the compressed air (24) between the outlet of the compressor section (12) and the inlet of the combustor (14). A cooling fluid (50) may be driven by a pump (52) located outside of the engine casing (53) or a pump (54) mounted on the rotor shaft (17). The cooling circuit (39) may include an orifice (60) for causing the cooling fluid (50) to change from a liquid state to a gaseous state, thereby increasing the heat transfer capacity of the cooling circuit (39).

  20. Heating and Chemical Enrichment in the Core of the Antlia Cluster

    NASA Astrophysics Data System (ADS)

    Hawley, William

    2011-08-01

    The dynamical processes responsible for heating and chemical enrichment of the ICM depend upon the environment and thus the cluster's evolutionary stage. These processes create distinct X-ray signatures in the hot cluster gas. We use a 53 ks XMM exposure of the core of the Antlia cluster, a galaxy cluster in an intermediate merger stage without a cool core, to study the transport of energy and metals throughout the ICM. We construct density, temperature, pressure, entropy and abundance maps to identify gas motions and heat flows, relate these motions to metal abundance ratios and gradients, and test simple models for chemical enrichment and heating of the Antlia cluster gas.

  1. Development of Mechanistic Modeling Capabilities for Local Neutronically-Coupled Flow-Induced Instabilities in Advanced Water-Cooled Reactors

    SciTech Connect

    Michael Podowski

    2009-11-30

    The major research objectives of this project included the formulation of flow and heat transfer modeling framework for the analysis of flow-induced instabilities in advanced light water nuclear reactors such as boiling water reactors. General multifield model of two-phase flow, including the necessary closure laws. Development of neurton kinetics models compatible with the proposed models of heated channel dynamics. Formulation and encoding of complete coupled neutronics/thermal-hydraulics models for the analysis of spatially-dependent local core instabilities. Computer simulations aimed at testing and validating the new models of reactor dynamics.

  2. Aqueous Iron-Sulfide Clusters in Variably Saturated Soil Systems: Implications for Iron Cycling and Fluid Flow

    NASA Astrophysics Data System (ADS)

    McGuire, J. T.; Hansen, D. J.; Mohanty, B. P.

    2008-12-01

    Iron and sulfur cycling is an important control on contaminant fate and transport, the availability of micronutrients and the physics of water flow. This study explores the effects of soil structure (i.e. layers, lenses, macropores, or fractures) on linked biogeochemical and hydrological processes involving Fe and S cycling in the vadose zone using packed soil columns. Three laboratory soil columns were constructed: a homogenized medium-grained sand, homogenized organic-rich loam, and a sand-over-loam layered column. Both upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events respectively. Water samples extracted by lysimeter were analyzed for reduced species (including total sulfide, Fe(II), and FeSaq) voltammetrically using a mercury drop electrode. In addition to other reduced species, aqueous FeS clusters (FeSaq) were observed in two of the columns, with the greatest concentrations of FeSaq occurring in close proximity to the soil interface in the layered column. To our knowledge, this is the first documentation of aqueous FeS clusters in partially saturated sediments. The aqueous nature of FeSaq allows it to be transported instead of precipitating and suggests that current conceptual models of iron-sulfur cycling may need to be adapted to account for an aqueous phase. The presence of iron-rich soil aggregates near the soil interface may indicate that FeS clusters played a critical role in the formation of soil aggregates that subsequently caused up to an order of magnitude decrease in hydraulic conductivity.

  3. Boulder Clusters as Flow Refugia for Juvenile Salmonids and Aquatic Invertebrates in Steep Mountain Streams, Klamath Mountains, Northern California

    NASA Astrophysics Data System (ADS)

    Cover, M. R.; May, C. L.; Dietrich, W. E.; Resh, V. H.

    2005-12-01

    The availability of flow refugia and cover is an important factor affecting habitat suitability for fish and invertebrates, especially in steep, turbulent streams. In some channels, crevices beneath and between large rocks may be the only available flow refugia that allow rainbow trout (Oncorhynchus mykiss) to conserve energy and escape from high velocity flow during large storm events. Many aquatic invertebrates, especially large or crawling taxa, require cover that is provided by unembedded crevice space underneath large stones. To investigate the influence of channel type on habitat availability, we performed intensive surveys of crevice habitat for salmonids and benthic invertebrates in 12 reaches in Walker Creek, a 25 square km basin in the Klamath Mountains of Northern California. We identified four reaches in each of three channel types: plane bed (3.1% - 3.7% slope), step-pool (5.4% - 6.5% slope), and cascade (6.3% - 8.5% slope). We used 4 realistic fish models (5, 10, 15, and 20 cm length) to assess the size of crevices and presence of flow refugia associated with all cobble (64 - 256 mm) and boulder (> 256 mm) grains within five 0.5 m-wide diagonal transects. The total abundance of crevices was similar among plane bed (6.3 +/- 1.1 m-2) (Mean +/- SD), step-pool (6.2 +/- 0.25 m-2), and cascade (6.7 +/- 1.2 m-2) reaches. Small (5 cm) crevices made up the majority of crevices in all three reach types. While the presence of 5 cm and 10 cm crevices was not significantly different between the three channel types, there were significantly more large (20 cm) crevices in cascade (0.73 +/- 0.33 m-2) and step-pool (0.68 +/- 0.1 m-2) reaches than in plane bed (0.26 +/- 0.14 m-2) reaches (AVOVA, p < 0.05). Moderately sized (15 cm) crevices were more common in step-pool reaches (0.91 +/- 0.13 m-2) than either cascade (0.54 +/- 0.15 m-2) or plane bed (0.42 +/- 0.13 m-2) reaches. Based on these results we conclude that step-pool reaches provide the most favorable habitat

  4. Electron cooling

    NASA Astrophysics Data System (ADS)

    Meshkov, I.; Sidorin, A.

    2004-10-01

    The brief review of the most significant and interesting achievements in electron cooling method, which took place during last two years, is presented. The description of the electron cooling facilities-storage rings and traps being in operation or under development-is given. The applications of the electron cooling method are considered. The following modern fields of the method development are discussed: crystalline beam formation, expansion into middle and high energy electron cooling (the Fermilab Recycler Electron Cooler, the BNL cooler-recuperator, cooling with circulating electron beam, the GSI project), electron cooling in traps, antihydrogen generation, electron cooling of positrons (the LEPTA project).

  5. Stochastic Cooling

    SciTech Connect

    Blaskiewicz, M.

    2011-01-01

    Stochastic Cooling was invented by Simon van der Meer and was demonstrated at the CERN ISR and ICE (Initial Cooling Experiment). Operational systems were developed at Fermilab and CERN. A complete theory of cooling of unbunched beams was developed, and was applied at CERN and Fermilab. Several new and existing rings employ coasting beam cooling. Bunched beam cooling was demonstrated in ICE and has been observed in several rings designed for coasting beam cooling. High energy bunched beams have proven more difficult. Signal suppression was achieved in the Tevatron, though operational cooling was not pursued at Fermilab. Longitudinal cooling was achieved in the RHIC collider. More recently a vertical cooling system in RHIC cooled both transverse dimensions via betatron coupling.

  6. Influence of temporal noise on the skin blood flow measurements performed by cooled thermal imaging camera: limit possibilities within each physiological frequency range

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Volkov, I. U.; Fomin, A. V.

    2016-04-01

    This paper describes limit possibilities of modern cooled thermal imaging cameras as a tool for estimation of blood flow oscillations at the surface of living body. Skin temperature oscillations, as we assumed, are a consequence of the blood flow oscillations. We considered the temperature sensitivity 0.01-0.02 °C as a typical for the most of modern cooled long wave thermal imaging cameras. Fourier filter used to investigate the temperature signal separately within endothelial, neurogenic, myogenic, respiratory and cardiac frequency ranges. The level of temporal noise has been estimated during measurements of no living body with stabilized temperature ~ 24°C. The level of temperature oscillations has been calculated for the group of healthy subjects within each frequency range. Thus, we were able to determine signal-to-noise ratio within frequency band [0.001, 1] Hz. As a result, we determine that skin temperature oscillations measured by thermal imaging camera with sensitivity 0.02°C have the upper frequency limit ~ 0.2 Hz. In other words, within the respiratory and cardiac frequency ranges of blood flow oscillations the noise level exceeds signal one, and temperature measurements at the skin surface are practically useless. The endothelial, neurogenic and myogenic components of the temperature oscillations contain ~98% of the total spectral power of the signal. We have plot the empirical extrapolated curve of sensitivity of thermal imaging camera vs. frequency of the temperature oscillations. The data analysis shows that measurements of skin temperature oscillations within respiratory and cardiac ranges require the temperature sensitivity at least ~ 0.01°C and 0.001°C, respectively.

  7. An experimental study on sub-cooled flow boiling CHF of R134a at low pressure condition with atmospheric pressure (AP) plasma assisted surface modification

    SciTech Connect

    Kim, Seung Jun; Zou, Ling; Jones, Barclay G.

    2015-02-01

    In this study, sub-cooled flow boiling critical heat flux tests at low pressure were conducted in a rectangular flow channel with one uniformly heated surface, using simulant fluid R-134a as coolant. The experiments were conducted under the following conditions: (1) inlet pressure (P) of 400-800 kPa, (2) mass flux (G) of 124-248 kg/m2s, (3) inlet sub-cooling enthalpy (ΔHi) of 12~ 26 kJ/kg. Parametric trends of macroscopic system parameters (G, P, Hi) were examined by changing inlet conditions. Those trends were found to be generally consistent with previous understandings of CHF behavior at low pressure condition (i.e. reduced pressure less than 0.2). A fluid-to-fluid scaling model was utilized to convert the test data obtained with the simulant fluid (R-134a) into the prototypical fluid (water). The comparison between the converted CHF of equivalent water and CHF look-up table with same operation conditions were conducted, which showed good agreement. Furthermore, the effect of surface wettability on CHF was also investigated by applying atmospheric pressure plasma (AP-Plasma) treatment to modify the surface characteristic. With AP-Plasma treatment, the change of microscopic surface characteristic was measured in terms of static contact angle. The static contact angle was reduced from 80° on original non-treated surface to 15° on treated surface. An enhancement of 18% on CHF values under flow boiling conditions were observed on AP-Plasma treated surfaces compared to those on non-treated heating surfaces.

  8. On the flow and water quality in the Tokyo Bay including effect of cooling water for the Power Generating Plant

    NASA Astrophysics Data System (ADS)

    Kitahara, Kouichi; Wada, Akira; Uehara, Yoshikazu; Fukuoka, Ippei; Kawanaga, Mitsuhito; Takano, Tairyu

    Driving forces of seawater current in the Tokyo Bay have several factors including the tide, the density structure, the river inflow and others. On the other hand, many power plants of total output of 185.4 MW (as of 1995) are located along the coast of the bay, together with a large number of factors which load the sea area with cooling water and heat. Although these facilities might be considered to affect water current in the bay, few studies have been made on the effects which these artificial inputs may exert on water current. The present study reports computation results, using a 3-dimentional current model on effects of water intake and effluent by a possibly increasing number of power plants on the current in the bay. It was concluded that an additional power plant output of 103.1 MW (corresponding to increase of cooling water by 30% and of heat load by 20% from the present levels) might bring about only slight changes except for altered water current and temperature in the vicinities of power plants of which power output were increased. Average temperature rise of 0.1 °C was also predicted in the surface water throughout the bay.

  9. Direct cooled power electronics substrate

    DOEpatents

    Wiles, Randy H [Powell, TN; Wereszczak, Andrew A [Oak Ridge, TN; Ayers, Curtis W [Kingston, TN; Lowe, Kirk T [Knoxville, TN

    2010-09-14

    The disclosure describes directly cooling a three-dimensional, direct metallization (DM) layer in a power electronics device. To enable sufficient cooling, coolant flow channels are formed within the ceramic substrate. The direct metallization layer (typically copper) may be bonded to the ceramic substrate, and semiconductor chips (such as IGBT and diodes) may be soldered or sintered onto the direct metallization layer to form a power electronics module. Multiple modules may be attached to cooling headers that provide in-flow and out-flow of coolant through the channels in the ceramic substrate. The modules and cooling header assembly are preferably sized to fit inside the core of a toroidal shaped capacitor.

  10. The global monsoon division combining the k-means clustering method and low-level cross-equatorial flow

    NASA Astrophysics Data System (ADS)

    Jiang, Ning; Qian, Weihong; Leung, Jeremy Cheuk-Hin

    2016-10-01

    The global monsoon domain has been recently determined utilizing two criteria: difference of local maximum and minimum pentad-mean precipitation rates exceeding 4 mm day-1, and wind reversal of low-level cross-equatorial flow. In this paper, 22 major dry-wet alteration regions under six categories were first derived through the k-means clustering method from the climatological evolution of global precipitation. Considering the seasonal influences of the low-level cross-equatorial flow in these major dry-wet alternation regions, the global monsoon was objectively divided into 16 major regions under five climatological precipitation categories. Nine monsoon regions are distributed between Asia and Australia while four regions are from Africa to the Southwest Indian Ocean and three regions in Americas. Precipitation trends during rainy seasons of 1981-2010 were examined in the 16 monsoon regions. Four regions with decreasing trends of precipitation are located in Africa and the Southwest Indian Ocean while three regions with increasing trends are situated in Americas. Six regions of increasing precipitation trends are concentrated in Asia and the biggest increasing trend is found in south China.

  11. Dynamics of the poor clusters MKW 4 and AWM 4

    NASA Astrophysics Data System (ADS)

    Malumuth, E. M.; Kriss, G. A.

    1986-09-01

    The authors have obtained redshifts and CCD photometry of nearly complete samples of galaxies within 1 Mpc of the centers of the Morgan poor clusters MKW 4 and AWM 4. These data are used to study the luminosity functions and the mass distributions of the clusters. For MKW 4 the authors have obtained a sufficient number of galaxy velocities (32) to construct a dynamical model for the cluster. Using the derived potential, they match the observed X-ray surface brightness profile if they allow for a weak cooling flow in the hot gas and if they take the mass distribution of the central galaxy into account. For AWM 4 no well-constrained models of the mass distribution could be obtained, but the best fitting models also give good agreement with X-ray data if a weak cooling flow in the hot gas is assumed.

  12. Turbomachine rotor with improved cooling

    DOEpatents

    Hultgren, Kent Goran; McLaurin, Leroy Dixon; Bertsch, Oran Leroy; Lowe, Perry Eugene

    1998-01-01

    A gas turbine rotor has an essentially closed loop cooling air scheme in which cooling air drawn from the compressor discharge air that is supplied to the combustion chamber is further compressed, cooled, and then directed to the aft end of the turbine rotor. Downstream seal rings attached to the downstream face of each rotor disc direct the cooling air over the downstream disc face, thereby cooling it, and then to cooling air passages formed in the rotating blades. Upstream seal rings attached to the upstream face of each disc direct the heated cooling air away from the blade root while keeping the disc thermally isolated from the heated cooling air. From each upstream seal ring, the heated cooling air flows through passages in the upstream discs and is then combined and returned to the combustion chamber from which it was drawn.

  13. Turbomachine rotor with improved cooling

    DOEpatents

    Hultgren, K.G.; McLaurin, L.D.; Bertsch, O.L.; Lowe, P.E.

    1998-05-26

    A gas turbine rotor has an essentially closed loop cooling air scheme in which cooling air drawn from the compressor discharge air that is supplied to the combustion chamber is further compressed, cooled, and then directed to the aft end of the turbine rotor. Downstream seal rings attached to the downstream face of each rotor disc direct the cooling air over the downstream disc face, thereby cooling it, and then to cooling air passages formed in the rotating blades. Upstream seal rings attached to the upstream face of each disc direct the heated cooling air away from the blade root while keeping the disc thermally isolated from the heated cooling air. From each upstream seal ring, the heated cooling air flows through passages in the upstream discs and is then combined and returned to the combustion chamber from which it was drawn. 5 figs.

  14. Flow and heat transfer in an L-shaped cooling passage with ribs and pin fins for the trailing edge of a gas-turbine vane and blade

    NASA Astrophysics Data System (ADS)

    Pardeshi, Irsha

    Efficient and effective cooling of the trailing edges of gas-turbine vanes and blades is challenging because there is very little space to work with. In this study, CFD simulations based on steady RANS closed by the shear-stress transport turbulence model were performed to study the flow and heat transfer in an L-shaped duct for the trailing edge under two operating conditions. One operating condition, referred to as the laboratory condition, where experimental measurements were made, has a Reynolds number at the duct inlet of ReD = 15,000, coolant inlet temperature of Tinlet = 300 K, wall temperature of Twall = 335 K, a back pressure of Pb = 1 atm. When rotating, the angular speed was O = 1,000 rpm. The other condition, referred to as the engine-relevant condition, has Re D = 150,000 at the duct inlet, Tinlet = 673 K, Twall = 1,173 K, and Pb = 25 atm. When rotating, O was 3,600 rpm. The objective is to understand the nature of the flow and heat transfer in an L-shaped cooling passage for the trailing edge that has a combination of ribs and pin fins under rotating and non-rotating conditions with focus on how pin fins and ribs distribute the flow throughout the passage and to understand what features of the flow and heat transfer can or cannot be extrapolated from the laboratory to the engine-relevant operating conditions. When there is no rotation, results obtained show that for both operating conditions, the pin fins minimized the size of the separation bubble when the flow exits the inlet duct into the expanded portion of the L-shaped duct. The size of the separation bubble at the tip of the L-shaped duct created by the adverse pressure gradient is quite large for the laboratory condition and relatively small for the engine condition. Each rib was found to create two sets of recirculating flows, one just upstream of the rib because of the adverse pressure gradient induced by the rib and one just downstream of the rib because of flow separation from a sharp edge

  15. Compton cooling and its effects on spectral and hydrodynamic properties of an accretion flow around a black hole: results of a coupled monte carlo TVD simulation

    NASA Astrophysics Data System (ADS)

    Ghosh, H.; Garain, S. K.; Chakrabarti, S. K.

    We investigate the effects of cooling of the Compton cloud on the outflow formation rate in an accretion disk around a black hole using a time-dependent coupled hydrodynamics - radiative transfer sumulation. We show that as a result of inverse-Comptonization of the soft photons, originating from the Keplerian disk immersed into an accreting sub-Keplerian flow (halo), by the hot Compton cloud, the cloud becomes cooler with the increase in the disk rate. As the resultant thermal pressure is reduced, the post-shock region collapses and the outflow rate is also reduced. We also find a direct correlation between the spectral states and the outflow rates of an accreting black hole.

  16. Large Eddy Simulation of a Film Cooling Flow Injected from an Inclined Discrete Cylindrical Hole into a Crossflow with Zero-Pressure Gradient Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Johnson, Perry L.; Shyam, Vikram

    2012-01-01

    A Large Eddy Simulation (LES) is performed of a high blowing ratio (M = 1.7) film cooling flow with density ratio of unity. Mean results are compared with experimental data to show the degree of fidelity achieved in the simulation. While the trends in the LES prediction are a noticeable improvement over Reynolds-Averaged Navier-Stokes (RANS) predictions, there is still a lack a spreading on the underside of the lifted jet. This is likely due to the inability of the LES to capture the full range of influential eddies on the underside of the jet due to their smaller structure. The unsteady structures in the turbulent coolant jet are also explored and related to turbulent mixing characteristics

  17. Plug cluster module demonstration

    NASA Technical Reports Server (NTRS)

    Rousar, D. C.

    1978-01-01

    The low pressure, film cooled rocket engine design concept developed during two previous ALRC programs was re-evaluated for application as a module for a plug cluster engine capable of performing space shuttle OTV missions. The nominal engine mixture ratio was 5.5 and the engine life requirements were 1200 thermal cycles and 10 hours total operating life. The program consisted of pretest analysis; engine tests, performed using residual components; and posttest analysis. The pretest analysis indicated that operation of the operation of the film cooled engine at O/F = 5.5 was feasible. During the engine tests, steady state wall temperature and performance measurement were obtained over a range of film cooling flow rates, and the durability of the engine was demonstrated by firing the test engine 1220 times at a nominal performance ranging from 430 - 432 seconds. The performance of the test engine was limited by film coolant sleeve damage which had occurred during previous testing. The post-test analyses indicated that the nominal performance level can be increased to 436 seconds.

  18. AGN Feedback And Evolution of Radio Sources: Discovery of An X-Ray Cluster Associated With Z=1 Quasar

    SciTech Connect

    Siemiginowska, Aneta; Cheung, C.C.; LaMassa, S.; Burke, D.; Aldcroft, T.L.; Bechtold, J.; Elvis, M.; Worrall, D.M.; /Bristol U.

    2006-01-11

    We report the first significant detection of an X-ray cluster associated with a powerful (L{sub bol} {approx} 10{sup 47} erg sec{sup -1}) radio-loud quasar at high redshift (z=1.06). Diffuse X-ray emission is detected out to {approx} 120 kpc from the CSS quasar 3C 186. A strong Fe-line emission at the z{sub rest} = 1.06 confirms its thermal nature. We find that the CSS radio source is highly overpressured with respect to the thermal cluster medium by 2-3 orders of magnitude. This provides direct observational evidence that the radio source is not thermally confined as posited in the ''frustrated'' scenario for CSS sources. Instead, the radio source may be young and at an early stage of its evolution. This source provides the first detection of the AGN in outburst in the center of a cooling flow cluster. Powerful radio sources are thought to be triggered by the cooling flows. The evidence for the AGN activity and intermittent outbursts comes from the X-ray morphology of low redshift clusters, which usually do not harbour quasars. 3C186 is a young active radio source which can supply the energy into the cluster and potentially prevent its cooling. We discuss energetics related to the quasar activity and the cluster cooling flow, and possible feedback between the evolving radio source and the cluster.

  19. Angularis oculi vein blood flow modulates the magnitude but not the control of selective brain cooling in sheep.

    PubMed

    Fuller, Andrea; Hetem, Robyn S; Meyer, Leith C R; Maloney, Shane K

    2011-06-01

    To investigate the role of the angularis oculi vein (AOV) in selective brain cooling (SBC), we measured brain and carotid blood temperatures in six adult female Dorper sheep. Halfway through the study, a section of the AOV, just caudal to its junction with the dorsal nasal vein, was extirpated on both sides. Before and after AOV surgery, the sheep were housed outdoors at 21-22°C and were exposed in a climatic chamber to daytime heat (40°C) and water deprivation for 5 days. In sheep outdoors, SBC was significantly lower after the AOV had been cut, with its 24-h mean reduced from 0.25 to 0.01°C (t(5) = 3.06, P = 0.03). Carotid blood temperature also was lower (by 0.28°C) at all times of day (t(5) = 3.68, P = 0.01), but the pattern of brain temperature was unchanged. The mean threshold temperature for SBC was not different before (38.85 ± 0.28°C) and after (38.85 ± 0.39°C) AOV surgery (t(5) =0.00, P = 1.00), but above the threshold, SBC magnitude was about twofold less after surgery. SBC after AOV surgery also was less during heat exposure and water deprivation. However, SBC increased progressively by the same magnitude (0.4°C) over the period of water deprivation, and return of drinking water led to rapid cessation of SBC in sheep before and after AOV surgery. We conclude that the AOV is not the only conduit for venous drainage contributing to SBC in sheep and that, contrary to widely held opinion, control of SBC does not involve changes in the vasomotor state of the AOV.

  20. Pressure drop, heat transfer, critical heat flux, and flow stability of two-phase flow boiling of water and ethylene glycol/water mixtures - final report for project "Efficent cooling in engines with nucleate boiling."

    SciTech Connect

    Yu, W.; France, D. M.; Routbort, J. L.

    2011-01-19

    Because of its order-of-magnitude higher heat transfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and to eliminate potential hot spots in engines. However, the fundamental understanding of flow boiling mechanisms of a 50/50 ethylene glycol/water mixture under engineering application conditions is still limited. In addition, it is impractical to precisely maintain the volume concentration ratio of the ethylene glycol/water mixture coolant at 50/50. Therefore, any investigation into engine coolant characteristics should include a range of volume concentration ratios around the nominal 50/50 mark. In this study, the forced convective boiling heat transfer of distilled water and ethylene glycol/water mixtures with volume concentration ratios of 40/60, 50/50, and 60/40 in a 2.98-mm-inner-diameter circular tube has been investigated in both the horizontal flow and the vertical flow. The two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux of the test fluids were determined experimentally over a range of the mass flux, the vapor mass quality, and the inlet subcooling through a new boiling data reduction procedure that allowed the analytical calculation of the fluid boiling temperatures along the experimental test section by applying the ideal mixture assumption and the equilibrium assumption along with Raoult's law. Based on the experimental data, predictive methods for the two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux under engine application conditions were developed. The results summarized in this final project report provide the necessary information for designing and implementing nucleate-boiling vehicular cooling systems.

  1. Design and experimental analysis of counter-flow heat and mass exchanger incorporating (M-cycle) for evaporative cooling

    NASA Astrophysics Data System (ADS)

    Khalid, Omar; Butt, Zubair; Tanveer, Waqas; Rao, Hasan Iqbal

    2016-09-01

    In this paper, the functioning of dew-point cooler is improved in terms of its thermal effectiveness. For this reason, a heat and mass exchanger has been designed by using a counter-flow pattern incorporating Maisotsenko cycle (M-cycle) having effective absorbing material called Kraft paper on wet channel side and improved width to height ratio. Experimentation has been performed under various inlet air working parameters such as humidity, velocity and temperature in addition with changing feed water temperature. The results from the experiments specify that the dew-point and the wet-bulb effectiveness is achieved between 67-87 % and 104-120 % respectively. Analysis is performed with temperature variation between 25 and 45 °C at different absolute humidity levels ranging from 14.4 to 18 g/kg, while the inlet air velocity is varied between 0.88 and 1.50 m/s. Thus, the working ability of the improved design has been found 5 % more effective in terms of wet bulb effectiveness as compared to previous counter-flow designs.

  2. Measuring flow and pressure of lithium coolant under developmental testing of a high-temperature cooling system of a space nuclear power plant

    NASA Astrophysics Data System (ADS)

    Sobolev, V. Ya.; Sinyavsky, V. V.

    2014-12-01

    Sub-megawatt space NPP use lithium as a coolant and niobium alloy as a structural material. In order to refine the lithium-niobium technology of the material and design engineering, lithium-niobium loops were worked out in RSC Energia, and they were tested at a working temperature of lithium equal to 1070-1300 K. In order to measure the lithium flow and pressure, special gauges were developed, which made possible the calibration and checkout of the loops without their dismantling. The paper describes the architecture of the electromagnetic flowmeter and the electromagnetic vibrating-wire pressure transducer (gauge) for lithium coolant in the nuclear power plant cooling systems. The operating principles of these meters are presented. Flowmeters have been developed for channel diameters ranging from 10 to 100 mm, which are capable of measuring lithium flows in the range of 0.1 to 30 L/s with the error of 3% for design calibration and 1% for volume graduation. The temperature error of the pressure transducers does not exceed 0.4% per 100 K; the nonlinearity and hysteresis of the calibration curve do not exceed 0.3 and 0.4%, respectively. The transducer applications are illustrated by the examples of results obtained from tests on the NPP module mockup and heat pipes of a radiation cooler.

  3. Compressor bleed cooling fluid feed system

    DOEpatents

    Donahoo, Eric E; Ross, Christopher W

    2014-11-25

    A compressor bleed cooling fluid feed system for a turbine engine for directing cooling fluids from a compressor to a turbine airfoil cooling system to supply cooling fluids to one or more airfoils of a rotor assembly is disclosed. The compressor bleed cooling fluid feed system may enable cooling fluids to be exhausted from a compressor exhaust plenum through a downstream compressor bleed collection chamber and into the turbine airfoil cooling system. As such, the suction created in the compressor exhaust plenum mitigates boundary layer growth along the inner surface while providing flow of cooling fluids to the turbine airfoils.

  4. Hot outflows in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, C. C.; McNamara, B. R.

    2015-10-01

    The gas-phase metallicity distribution has been analysed for the hot atmospheres of 29 galaxy clusters using Chandra X-ray Observatory observations. All host brightest cluster galaxies (BCGs) with X-ray cavity systems produced by radio AGN. We find high elemental abundances projected preferentially along the cavities of 16 clusters. The metal-rich plasma was apparently lifted out of the BCGs with the rising X-ray cavities (bubbles) to altitudes between twenty and several hundred kiloparsecs. A relationship between the maximum projected altitude of the uplifted gas (the `iron radius') and jet power is found with the form R_Fe ∝ P_jet^{0.45}. The estimated outflow rates are typically tens of solar masses per year but exceed 100 M⊙ yr- 1 in the most powerful AGN. The outflow rates are 10-20 per cent of the cooling rates, and thus alone are unable to offset a cooling inflow. Nevertheless, hot outflows effectively redistribute the cooling gas and may play a significant role at regulating star formation and AGN activity in BCGs and presumably in giant elliptical galaxies. The metallicity distribution overall can be complex, perhaps due to metal-rich gas returning in circulation flows or being blown around in the hot atmospheres. Roughly 15 per cent of the work done by the cavities is expended lifting the metal-enriched gas, implying their nuclear black holes have increased in mass by at least ˜107-109 M⊙. Finally, we show that hot outflows can account for the broad, gas-phase metallicity distribution compared to the stellar light profiles of BCGs, and we consider a possible connection between hot outflows and cold molecular gas flows discovered in recent Atacama Large Millimeter Array observations.

  5. The computational-and-experimental investigation into the head-flow characteristic of the two-stage ejector for the emergency core cooling system of the NPP with a water-moderated water-cooled power reactor

    NASA Astrophysics Data System (ADS)

    Parfenov, Yu. V.

    2013-09-01

    The results of the computational-and-experimental investigation into the two-stage ejector for the emergency cooling system of the core of the water-moderated water-cooled power reactor. The results of experimental investigations performed for the ejector model at the JSC "EREC" and the result of calculations performed using the REMIX CFD code are presented.

  6. Snapshots of Proton Accommodation at a Microscopic Water Surface: Understanding the Vibrational Spectral Signatures of the Charge Defect in Cryogenically Cooled H(+)(H2O)(n=2-28) Clusters.

    PubMed

    Fournier, Joseph A; Wolke, Conrad T; Johnson, Mark A; Odbadrakh, Tuguldur T; Jordan, Kenneth D; Kathmann, Shawn M; Xantheas, Sotiris S

    2015-09-10

    We review the role that gas-phase, size-selected protonated water clusters, H(+)(H2O)n, have played in unraveling the microscopic mechanics responsible for the spectroscopic behavior of the excess proton in bulk water. Because the larger (n ≥ 10) assemblies are formed with three-dimensional cage morphologies that more closely mimic the bulk environment, we report the spectra of cryogenically cooled (10 K) clusters over the size range 2 ≤ n ≤ 28, over which the structures evolve from two-dimensional arrangements to cages at around n = 10. The clusters that feature a complete second solvation shell around a surface-embedded hydronium ion yield spectral signatures of the proton defect similar to those observed in dilute acids. The origins of the large observed shifts in the proton vibrational signature upon cluster growth were explored with two types of theoretical analyses. First, we calculate the cubic and semidiagonal quartic force constants and use these in vibrational perturbation theory calculations to establish the couplings responsible for the large anharmonic red shifts. We then investigate how the extended electronic wave functions that are responsible for the shapes of the potential surfaces depend on the nature of the H-bonded networks surrounding the charge defect. These considerations indicate that, in addition to the sizable anharmonic couplings, the position of the OH stretch most associated with the excess proton can be traced to large increases in the electric fields exerted on the embedded hydronium ion upon formation of the first and second solvation shells. The correlation between the underlying local structure and the observed spectral features is quantified using a model based on Badger's rule as well as via the examination of the electric fields obtained from electronic structure calculations. PMID:26158593

  7. Snapshots of Proton Accommodation at a Microscopic Water Surface: Understanding the Vibrational Spectral Signatures of the Charge Defect in Cryogenically Cooled H(+)(H2O)(n=2-28) Clusters.

    PubMed

    Fournier, Joseph A; Wolke, Conrad T; Johnson, Mark A; Odbadrakh, Tuguldur T; Jordan, Kenneth D; Kathmann, Shawn M; Xantheas, Sotiris S

    2015-09-10

    We review the role that gas-phase, size-selected protonated water clusters, H(+)(H2O)n, have played in unraveling the microscopic mechanics responsible for the spectroscopic behavior of the excess proton in bulk water. Because the larger (n ≥ 10) assemblies are formed with three-dimensional cage morphologies that more closely mimic the bulk environment, we report the spectra of cryogenically cooled (10 K) clusters over the size range 2 ≤ n ≤ 28, over which the structures evolve from two-dimensional arrangements to cages at around n = 10. The clusters that feature a complete second solvation shell around a surface-embedded hydronium ion yield spectral signatures of the proton defect similar to those observed in dilute acids. The origins of the large observed shifts in the proton vibrational signature upon cluster growth were explored with two types of theoretical analyses. First, we calculate the cubic and semidiagonal quartic force constants and use these in vibrational perturbation theory calculations to establish the couplings responsible for the large anharmonic red shifts. We then investigate how the extended electronic wave functions that are responsible for the shapes of the potential surfaces depend on the nature of the H-bonded networks surrounding the charge defect. These considerations indicate that, in addition to the sizable anharmonic couplings, the position of the OH stretch most associated with the excess proton can be traced to large increases in the electric fields exerted on the embedded hydronium ion upon formation of the first and second solvation shells. The correlation between the underlying local structure and the observed spectral features is quantified using a model based on Badger's rule as well as via the examination of the electric fields obtained from electronic structure calculations.

  8. Analysis of LAC Observations of Clusters of Galaxies and Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Hughes, J.

    1996-01-01

    The following publications are included and serve as the final report: The X-ray Spectrum of Abell 665; Clusters of Galaxies; Ginga Observation of an Oxygen-rich Supernova Remnant; Ginga Observations of the Coma Cluster and Studies of the Spatial Distribution of Iron; A Measurement of the Hubble Constant from the X-ray Properties and the Sunyaev-Zel'dovich Effect of Abell 2218; Non-polytropic Model for the Coma Cluster; and Abundance Gradients in Cooling Flow Clusters: Ginga LAC (Large Area Counter) and Einstein SSS (Solid State Spectrometer) Spectra of A496, A1795, A2142, and A2199.

  9. Electronic and vibrational spectroscopic studies of jet-cooled 5-cyanoindole and its water clusters, 5CI-(H2O)n, (n = 0-2)

    NASA Astrophysics Data System (ADS)

    Min, Ahreum; Moon, Cheol Joo; Ahn, Ahreum; Lee, Ji Hoon; Kim, Seong Keun; Choi, Myong Yong

    2016-08-01

    Mass-selected resonant two-photon ionization (R2PI) and UV-UV hole-burning, and infrared-dip spectra of 5-cyanoindole (5CI) and its water clusters, 5CI-(H2O)n (n = 1 and 2) were measured. Although, the structures of 5CI-(H2O)1-2 are similar to those of 3CI-(H2O)1-2, the photofragmentation behaviors of the two systems are quite different due to the La-Lb state energy lowering and higher binding energies of 5CI-(H2O)1-2 compared to those of 3CI-(H2O)1-2. Especially for the case of 5CI-(H2O)2 cluster, shortening excited-state lifetime of 5CI-(H2O)2 causes the broad background in the R2PI spectrum of 5CI-(H2O)2.

  10. Thickness distribution of a cooling pyroclastic flow deposit: Optimization using InSAR, FEMs, and an adaptive mesh algorithm

    NASA Astrophysics Data System (ADS)

    Masterlark, T.; Lu, Z.; Rykhus, R.

    2003-12-01

    We construct finite element models (FEMs) of a pyroclastic flow deposit (PFD) emplaced during the 1986 eruption of Augustine volcano, Alaska. Interferometric synthetic aperture radar (InSAR) imagery documents the consistent contraction of the PFD during 1992-2000. Three-dimensional problem domains of the FEMs include an elastic substrate overlain by a thermoelastic material representing the PFD. The geometry of the substrate is determined from a digital elevation model (DEM) and bathymetry data. The thickness of the PFD is initially determined from the difference between post- and pre-eruptive DEMs. Systematic prediction errors suggest the PFD thickness distribution, estimated from the DEM difference, is inaccurate. We combine InSAR images, FEMs, and an adaptive mesh algorithm to re-estimate the geometry of the PFD and optimize the thickness distribution for the PFD. Prediction errors from the FEM that includes an optimized PFD geometry are reduced by 20% with respect to those from an FEM that includes a PFD geometry derived from the DEM difference.

  11. NightCool: A Nocturnal Radiation Cooling Concept

    SciTech Connect

    Parker, Danny S.; Sherwin, John R.; Hermelink, Andreas H.

    2008-08-26

    This report describes an experimental evaluation that was conducted on a night sky cooling system designed to substantially reduce space cooling needs in homes in North American climates. The system uses a sealed attic covered by a highly conductive metal roof (a roof integrated radiator) which is selectively linked by air flow to the main zone with the attic zone to provide cooling - largely during nighttime hours.

  12. Cooling wall

    SciTech Connect

    Nosenko, V.I.

    1995-07-01

    Protecting the shells of blast furnaces is being resolved by installing cast iron cooling plates. The cooling plates become non-operational in three to five years. The problem is that defects occur in manufacturing the cooling plates. With increased volume and intensity of work placed on blast furnaces, heat on the cast iron cooling plates reduces their reliability that limits the interim repair period of blast furnaces. Scientists and engineers from the Ukraine studied this problem for several years, developing a new method of cooling the blast furnace shaft called the cooling wall. Traditional cast iron plates were replaced by a screen of steel tubes, with the area between the tubes filled with fireproof concrete. Before placing the newly developed furnace shaft into operation, considerable work was completed such as theoretical calculations, design, research of temperature fields and tension. Continual testing over many years confirms the value of this research in operating blast furnaces. The cooling wall works with water cooling as well as vapor cooling and is operating in 14 blast furnaces in the Ukraine and two in Russia, and has operated for as long as 14 years.

  13. Efficient Synthesis of Ir-Polyoxometalate Cluster Using a Continuous Flow Apparatus and STM Investigation of Its Coassembly Behavior on HOPG Surface.

    PubMed

    Zhang, Junyong; Chang, Shaoqing; Suryanto, Bryan H R; Gong, Chunhua; Zeng, Xianghua; Zhao, Chuan; Zeng, Qingdao; Xie, Jingli

    2016-06-01

    Taking advantage of a continuous-flow apparatus, the iridium(III)-containing polytungstate cluster K12Na2H2[Ir2Cl8P2W20O72]·37H2O (1) was obtained in a reasonable yield (13% based on IrCl3·H2O). Compound 1 was characterized by Fourier transform IR, UV-visible, (31)P NMR, electrospray ionization mass spectrometry (ESI-MS), and thermogravimetric analysis measurements. (31)P NMR, ESI-MS, and elemental analysis all indicated 1 was a new polytungstate cluster compared with the reported K14[(IrCl4)KP2W20O72] compound. Intriguingly, the successful isolation of 1 relied on the custom-built flow apparatus, demonstrating the uniqueness of continuous-flow chemistry to achieve crystalline materials. The catalytic properties of 1 were assessed by investigating the activity on catalyzing the electro-oxidation of ruthenium tris-2,2'-bipyridine [Ru(bpy)3](2+/3+). The voltammetric behavior suggested a coupled catalytic behavior between [Ru(bpy)3](3+/2+) and 1. Furthermore, on the highly oriented pyrolytic graphite surface, 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) was used as the two-dimensional host network to coassemble cluster 1; the surface morphology was observed by scanning tunneling microscope technique. "S"-shape of 1 was observed, indicating that the cluster could be accommodated in the cavity formed by two TCDB host molecules, leading to a TCDB/cluster binary structure.

  14. Efficient Synthesis of Ir-Polyoxometalate Cluster Using a Continuous Flow Apparatus and STM Investigation of Its Coassembly Behavior on HOPG Surface.

    PubMed

    Zhang, Junyong; Chang, Shaoqing; Suryanto, Bryan H R; Gong, Chunhua; Zeng, Xianghua; Zhao, Chuan; Zeng, Qingdao; Xie, Jingli

    2016-06-01

    Taking advantage of a continuous-flow apparatus, the iridium(III)-containing polytungstate cluster K12Na2H2[Ir2Cl8P2W20O72]·37H2O (1) was obtained in a reasonable yield (13% based on IrCl3·H2O). Compound 1 was characterized by Fourier transform IR, UV-visible, (31)P NMR, electrospray ionization mass spectrometry (ESI-MS), and thermogravimetric analysis measurements. (31)P NMR, ESI-MS, and elemental analysis all indicated 1 was a new polytungstate cluster compared with the reported K14[(IrCl4)KP2W20O72] compound. Intriguingly, the successful isolation of 1 relied on the custom-built flow apparatus, demonstrating the uniqueness of continuous-flow chemistry to achieve crystalline materials. The catalytic properties of 1 were assessed by investigating the activity on catalyzing the electro-oxidation of ruthenium tris-2,2'-bipyridine [Ru(bpy)3](2+/3+). The voltammetric behavior suggested a coupled catalytic behavior between [Ru(bpy)3](3+/2+) and 1. Furthermore, on the highly oriented pyrolytic graphite surface, 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) was used as the two-dimensional host network to coassemble cluster 1; the surface morphology was observed by scanning tunneling microscope technique. "S"-shape of 1 was observed, indicating that the cluster could be accommodated in the cavity formed by two TCDB host molecules, leading to a TCDB/cluster binary structure. PMID:27163481

  15. Partitioning Between Plume and Diffuse Flow at the Grotto Vent Cluster, Main Endeavour Vent Field, Juan de Fuca Ridge: Past and Present

    NASA Astrophysics Data System (ADS)

    Rona, P. A.; Bemis, K. G.; Jones, C.; Jackson, D. R.; Mitsuzawa, K.; Palmer, D. R.

    2010-12-01

    Seafloor hydrothermal systems discharge as plumes from discrete vents and as diffuse flow from surrounding areas that transfer heat and chemicals from the lithosphere into the ocean in quantitatively significant amounts. Our VIP (Vent Imaging Pacific) July 2000 experiment was designed to acoustically image and quantify these flows at vent clusters in the Main Endeavour field using a sonar system (Simrad SM 2000) mounted on ROV Jason from fixed positions on the seafloor using three methods that we developed. Buoyant plumes are reconstructed applying visualization techniques to volume backscatter from suspended particulates and density discontinuities in plumes. A Doppler algorithm is used to measure mean vertical velocity through plume cross sections and to calculate volume flux at different altitudes in a plume. Acoustic Scintillation Thermography (AST) is used to image irregular areas of diffuse flow. Results from a sulfide edifice (north tower of Grotto Vent cluster; height 12 m; diameter 10 m; sonar range 12 m) supplemented by additional AST measurements and in situ measurements of flow rate and temperature are tabulatd below: The higher diffuse than plume heat flux is consistent with prior studies at other sites. However, the ratio of diffuse to plume heat flux (range 23-353) is exceptionally large suggesting an overestimation of diffuse flow area at the high end and/or underestimation of plume flux. We are scheduled this fall to connect our next generation sonar system (COVIS=Cable Operated Vent Imaging Sonar) to the NEPTUNE Canada cabled observatory at the Grotto vent cluster. COVIS is designed to image plume and diffuse flow in space and in time, which will contribute to interpreting our past observations and to provide new insights on how partitioning may vary with time.

  16. Passive containment cooling system

    DOEpatents

    Billig, Paul F.; Cooke, Franklin E.; Fitch, James R.

    1994-01-01

    A passive containment cooling system includes a containment vessel surrounding a reactor pressure vessel and defining a drywell therein containing a non-condensable gas. An enclosed wetwell pool is disposed inside the containment vessel, and a gravity driven cooling system (GDCS) pool is disposed above the wetwell pool in the containment vessel and is vented to the drywell. An isolation pool is disposed above the GDCS pool and includes an isolation condenser therein. The condenser has an inlet line disposed in flow communication with the drywell for receiving the non-condensable gas along with any steam released therein following a loss-of-coolant accident (LOCA). The condenser also has an outlet line disposed in flow communication with the drywell for returning to the drywell both liquid condensate produced upon cooling of the steam and the non-condensable gas for reducing pressure within the containment vessel following the LOCA.

  17. Passive containment cooling system

    DOEpatents

    Billig, P.F.; Cooke, F.E.; Fitch, J.R.

    1994-01-25

    A passive containment cooling system includes a containment vessel surrounding a reactor pressure vessel and defining a drywell therein containing a non-condensable gas. An enclosed wetwell pool is disposed inside the containment vessel, and a gravity driven cooling system (GDCS) pool is disposed above the wetwell pool in the containment vessel and is vented to the drywell. An isolation pool is disposed above the GDCS pool and includes an isolation condenser therein. The condenser has an inlet line disposed in flow communication with the drywell for receiving the non-condensable gas along with any steam released therein following a loss-of-coolant accident (LOCA). The condenser also has an outlet line disposed in flow communication with the drywell for returning to the drywell both liquid condensate produced upon cooling of the steam and the non-condensable gas for reducing pressure within the containment vessel following the LOCA. 1 figure.

  18. Changes in the Metastability of the Midlatitude Southern Hemisphere Circulation and the Utility of Nonstationary Cluster Analysis and Split-Flow Blocking Indices as Diagnostic Tools

    NASA Astrophysics Data System (ADS)

    O'Kane, Terence; Risbey, James; Franzke, Christian; Horenko, Illia; Monselesan, Didier

    2013-04-01

    The authors examine changes in the metastability of the Southern Hemisphere 500-hPa circulation using both cluster analysis techniques and split-flow blocking indices. The cluster methodology is a purely datadriven approach for parameterization whereby a multiscale approximation to nonstationary dynamical processes is achieved through optimal sequences of locally stationary fast vector autoregressive factor (VARX) processes and some slow (or persistent) hidden process switching between them. Comparison is made with blocking indices commonly used in weather forecasting and climate analysis to identify dynamically relevant metastable regimes in the 500-hPa circulation in both reanalysis and Atmospheric Model Intercomparison Project (AMIP) model datasets. The analysis characterizes the metastable regime in both reanalysis and model datasets prior to 1978 as positive and negative phases of a hemispheric midlatitude blocking state with the southern annular mode (SAM) associated with a transition state. Post 1978, the SAM emerges as a true metastable state replacing the negative phase of the hemispheric blocking pattern. The hidden state frequency of occurrences exhibits strong trends. The blocking pattern dominates in the early 1980s then gradually decreases. There is a corresponding increase in the SAM frequency of occurrence. This trend is largely evident in the reanalysis summer and spring but was not evident in the AMIP dataset. Further comparison with the split-flow blocking indices reveals a superficial correspondence between the cluster hidden state frequency of occurrences and split-flow indices. Examination of composite states shows that the blocking indices capture splitting of the zonal flow whereas the cluster composites reflect coherent block AU1 formation. Differences in blocking climatologies from the respective methods are discussed.

  19. Variable area fuel cell cooling

    DOEpatents

    Kothmann, Richard E.

    1982-01-01

    A fuel cell arrangement having cooling fluid flow passages which vary in surface area from the inlet to the outlet of the passages. A smaller surface area is provided at the passage inlet, which increases toward the passage outlet, so as to provide more uniform cooling of the entire fuel cell. The cooling passages can also be spaced from one another in an uneven fashion.

  20. Heat exchanger with auxiliary cooling system

    DOEpatents

    Coleman, John H.

    1980-01-01

    A heat exchanger with an auxiliary cooling system capable of cooling a nuclear reactor should the normal cooling mechanism become inoperable. A cooling coil is disposed around vertical heat transfer tubes that carry secondary coolant therethrough and is located in a downward flow of primary coolant that passes in heat transfer relationship with both the cooling coil and the vertical heat transfer tubes. A third coolant is pumped through the cooling coil which absorbs heat from the primary coolant which increases the downward flow of the primary coolant thereby increasing the natural circulation of the primary coolant through the nuclear reactor.

  1. The problem of cooling an air-cooled cylinder on an aircraft engine

    NASA Technical Reports Server (NTRS)

    Brevoort, M J; Joyner, U T

    1941-01-01

    An analysis of the cooling problem has been to show by what means the cooling of an air-cooled aircraft engine may be improved. Each means of improving cooling is analyzed on the basis of effectiveness in cooling with respect to power for cooling. The altitude problem is analyzed for both supercharged and unsupercharged engines. The case of ground cooling is also discussed. The heat-transfer process from the hot gases to the cylinder wall is discussed on the basis of the fundamentals of heat transfer and thermodynamics. Adiabatic air-temperature rise at a stagnation point in compressible flow is shown to depend only on the velocity of flow.

  2. DEEP CHANDRA OBSERVATIONS OF A2199: THE INTERPLAY BETWEEN MERGER-INDUCED GAS MOTIONS AND NUCLEAR OUTBURSTS IN A COOL CORE CLUSTER

    SciTech Connect

    Nulsen, Paul E. J.; Li, Zhiyuan; Forman, William R.; Kraft, Ralph P.; Lal, Dharam V.; Jones, Christine; Murray, Stephen S.; Zhuravleva, Irina; Churazov, Eugene; Sanders, Jeremy S.; Fabian, Andrew C.; Johnson, Ryan E.

    2013-10-01

    We present new Chandra observations of A2199 that show evidence of gas sloshing due to a minor merger, as well as impacts of the radio source, 3C 338, hosted by the central galaxy, NGC 6166, on the intracluster gas. The new data are consistent with previous evidence of a Mach ≅ 1.46 shock 100'' from the cluster center, although there is still no convincing evidence for the expected temperature jump. Other interpretations of this feature are possible, but none is fully satisfactory. Large scale asymmetries, including enhanced X-ray emission 200'' southwest of the cluster center and a plume of low entropy, enriched gas reaching 50'' to the north of the center, are signatures of gas sloshing induced by core passage of a merging subcluster about 400 Myr ago. An association between the unusual radio ridge and low entropy gas are consistent with this feature being the remnant of a former radio jet that was swept away from the active galactic nucleus by gas sloshing. A large discrepancy between the energy required to produce the 100'' shock and the enthalpy of the outer radio lobes of 3C 338 suggests that the lobes were formed by a more recent, less powerful radio outburst. The lack of evidence for shocks in the central 10'' indicates that the power of the jet now is some two orders of magnitude smaller than when the 100'' shock was formed.

  3. Flow-Induced Vibration of a Reed in a Channel: Effect of Reed Shape on Convective Heat Transfer with Application to Electronic Cooling

    NASA Astrophysics Data System (ADS)

    Rips, Aaron; Shoele, Kourosh; Glezer, Ari; Mittal, Rajat

    2015-11-01

    Flow-induced vibration of a reed (a thin plate or flag) in a channel can improve heat transfer efficiency in forced convection applications, allowing for more heat transfer for the same fan power. Such systems have wide ranging applications in electronic and power cooling. We investigate the effect of 3D reed shape on heat transfer enhancement. To study 3D effects, we first use 2D fluid-structure interaction (FSI) simulations of an optimized reed (in terms of mass and stiffness) to generate a prescribed reed motion. We then apply that motion to a pseudo 3D reed (i.e. infinitely stiff in the spanwise direction) and study the heat transfer enhancement in a 3D channel. This method allows us to explore a large parameter space exhaustively, and using this method, we examine the effect of several parameters, such as reed planform and spanwise gap, on the heat transfer enhancements for forced convection in a channel. Simulations indicate that these geometrical feature have a significant effect on the vortex dynamics in the wake as well as the heat transfer efficiency. This work was supported by grants from AFOSR, EPRI and NSF.

  4. Final Report for Project DE-SC0006958: "An Investigation of the Effects of magnetic Fields and Collisionality on Shock Formation in Radiatively Cooled Plasma Flows"

    SciTech Connect

    Bott-Suzuki, Simon

    2014-11-05

    We have developed a new experimental platform to study bow-shock formation in plasma flows generated using an inverse wire array z-pinch. We have made significant progress on the analysis of both hydrodynamic and magnetized shocks using this system. The hydrodynamic experiments show formation of a well-defined Mach cone, and highly localized shock strong associated with radiative losses and rapidly cooling over the shock. Magnetized shocks show that the balance of magnetic and ram pressures dominate the evolution of the shock region, generating a low plasma beta void around the target. Manuscripts are in preparation for publication on both these topics. We have also published the development of a novel diagnostic method which allow recovery of interferometry and self-emission data along the same line of sight. Finally, we have carried out work to integrate a kinetic routine with the 3D MHD code Gorgon, however it remains to complete this process. Both undergraduate and graduate students have been involved in both the experimental work and publications.

  5. Cool Shelter

    ERIC Educational Resources Information Center

    Praeger, Charles E.

    2005-01-01

    Amid climbing energy costs and tightening budgets, administrators at school districts, colleges and universities are looking for all avenues of potential savings while promoting sustainable communities. Cool metal roofing can save schools money and promote sustainable design at the same time. Cool metal roofing keeps the sun's heat from collecting…

  6. Microtextured Surfaces for Turbine Blade Impingement Cooling

    NASA Technical Reports Server (NTRS)

    Fryer, Jack

    2014-01-01

    Gas turbine engine technology is constantly challenged to operate at higher combustor outlet temperatures. In a modern gas turbine engine, these temperatures can exceed the blade and disk material limits by 600 F or more, necessitating both internal and film cooling schemes in addition to the use of thermal barrier coatings. Internal convective cooling is inadequate in many blade locations, and both internal and film cooling approaches can lead to significant performance penalties in the engine. Micro Cooling Concepts, Inc., has developed a turbine blade cooling concept that provides enhanced internal impingement cooling effectiveness via the use of microstructured impingement surfaces. These surfaces significantly increase the cooling capability of the impinging flow, as compared to a conventional untextured surface. This approach can be combined with microchannel cooling and external film cooling to tailor the cooling capability per the external heating profile. The cooling system then can be optimized to minimize impact on engine performance.

  7. Effects of 'Cooled' Cooling Air on Pre-Swirl Nozzle Design

    NASA Technical Reports Server (NTRS)

    Scricca, J. A.; Moore, K. D.

    2006-01-01

    It is common practice to use Pre-Swirl Nozzles to facilitate getting the turbine blade cooling air onboard the rotating disk with minimum pressure loss and reduced temperature. Higher engine OPR's and expanded aircraft operating envelopes have pushed cooling air temperatures to the limits of current disk materials and are stressing the capability to cool the blade with practical levels of cooling air flow. Providing 'Cooled' Cooling Air is one approach being considered to overcome these limitations. This presentation looks at how the introduction of 'Cooled' Cooling Air impacts the design of the Pre-Swirl Nozzles, specifically in relation to the radial location of the nozzles.

  8. AVERAGE HEATING RATE OF HOT ATMOSPHERES IN DISTANT CLUSTERS BY RADIO ACTIVE GALACTIC NUCLEUS: EVIDENCE FOR CONTINUOUS ACTIVE GALACTIC NUCLEUS HEATING

    SciTech Connect

    Ma, C.-J.; McNamara, B. R.; Schaffer, R.; Nulsen, P. E. J.; Vikhlinin, A.

    2011-10-20

    We examine atmospheric heating by radio active galactic nuclei (AGNs) in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree (400SD) X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within a projected radius of 250 kpc. The radio emission is presumably associated with the brightest cluster galaxy. The mechanical jet power for each radio source was determined using scaling relations between radio power and cavity (mechanical) power determined for nearby clusters, groups, and galaxies with hot atmospheres containing X-ray cavities. The average jet power of central radio AGNs is approximately 2 x 10{sup 44} erg s{sup -1}. We find no significant correlation between radio power, and hence mechanical jet power, and the X-ray luminosities of clusters in the redshift range 0.1-0.6. This implies that the mechanical heating rate per particle is higher in lower mass, lower X-ray luminosity clusters. The jet power averaged over the sample corresponds to an atmospheric heating of approximately 0.2 keV per particle within R{sub 500}. Assuming the current AGN heating rate does not evolve but remains constant to redshifts of 2, the heating rate per particle would rise by a factor of two. We find that the energy injected from radio AGNs contribute substantially to the excess entropy in hot atmospheres needed to break self-similarity in cluster scaling relations. The detection frequency of radio AGNs is inconsistent with the presence of strong cooling flows in 400SD clusters, but does not exclude weak cooling flows. It is unclear whether central AGNs in 400SD clusters are maintained by feedback at the base of a cooling flow. Atmospheric heating by radio AGNs may retard the development of strong cooling flows at early epochs.

  9. ISOTROPIC HEATING OF GALAXY CLUSTER CORES VIA RAPIDLY REORIENTING ACTIVE GALACTIC NUCLEUS JETS

    SciTech Connect

    Babul, Arif; Sharma, Prateek; Reynolds, Christopher S.

    2013-05-01

    Active galactic nucleus (AGN) jets carry more than sufficient energy to stave off catastrophic cooling of the intracluster medium (ICM) in the cores of cool-core clusters. However, in order to prevent catastrophic cooling, the ICM must be heated in a near-isotropic fashion and narrow bipolar jets with P{sub jet} = 10{sup 44-45} erg s{sup -1}, typical of radio AGNs at cluster centers, are inefficient in heating the gas in the transverse direction to the jets. We argue that due to existent conditions in cluster cores, the supermassive black holes (SMBHs) will, in addition to accreting gas via radiatively inefficient flows, experience short stochastic episodes of enhanced accretion via thin disks. In general, the orientation of these accretion disks will be misaligned with the spin axis of the black holes (BHs) and the ensuing torques will cause the BH's spin axis (and therefore the jet axis) to slew and rapidly change direction. This model not only explains recent observations showing successive generations of jet-lobes-bubbles in individual cool-core clusters that are offset from each other in the angular direction with respect to the cluster center, but also shows that AGN jets can heat the cluster core nearly isotropically on the gas cooling timescale. Our model does require that the SMBHs at the centers of cool-core clusters be spinning relatively slowly. Torques from individual misaligned disks are ineffective at tilting rapidly spinning BHs by more than a few degrees. Additionally, since SMBHs that host thin accretion disks will manifest as quasars, we predict that roughly 1-2 rich clusters within z < 0.5 should have quasars at their centers.

  10. Film cooling for a closed loop cooled airfoil

    DOEpatents

    Burdgick, Steven Sebastian; Yu, Yufeng Phillip; Itzel, Gary Michael

    2003-01-01

    Turbine stator vane segments have radially inner and outer walls with vanes extending therebetween. The inner and outer walls are compartmentalized and have impingement plates. Steam flowing into the outer wall plenum passes through the impingement plate for impingement cooling of the outer wall upper surface. The spent impingement steam flows into cavities of the vane having inserts for impingement cooling the walls of the vane. The steam passes into the inner wall and through the impingement plate for impingement cooling of the inner wall surface and for return through return cavities having inserts for impingement cooling of the vane surfaces. At least one film cooling hole is defined through a wall of at least one of the cavities for flow communication between an interior of the cavity and an exterior of the vane. The film cooling hole(s) are defined adjacent a potential low LCF life region, so that cooling medium that bleeds out through the film cooling hole(s) reduces a thermal gradient in a vicinity thereof, thereby the increase the LCF life of that region.

  11. Cooled railplug

    DOEpatents

    Weldon, William F.

    1996-01-01

    The railplug is a plasma ignitor capable of injecting a high energy plasma jet into a combustion chamber of an internal combustion engine or continuous combustion system. An improved railplug is provided which has dual coaxial chambers (either internal or external to the center electrode) that provide for forced convective cooling of the electrodes using the normal pressure changes occurring in an internal combustion engine. This convective cooling reduces the temperature of the hot spot associated with the plasma initiation point, particularly in coaxial railplug configurations, and extends the useful life of the railplug. The convective cooling technique may also be employed in a railplug having parallel dual rails using dual, coaxial chambers.

  12. A 10{sup 10} solar mass flow of molecular gas in the A1835 brightest cluster galaxy

    SciTech Connect

    McNamara, B. R.; Russell, H. R.; Main, R. A.; Vantyghem, A. N.; Kirkpatrick, C. C.; Nulsen, P. E. J.; Edge, A. C.; Murray, N. W.; Hamer, S.; Combes, F.; Salome, P.; Fabian, A. C.; Baum, S. A.; O'Dea, C. P.; Bregman, J. N.; Donahue, M.; Voit, G. M.; Egami, E.; Oonk, J. B. R.; Tremblay, G.

    2014-04-10

    We report ALMA Early Science observations of the A1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect 5 × 10{sup 10} M {sub ☉} of molecular gas within 10 kpc of the BCG. Its ensemble velocity profile width of ∼130 km s{sup –1} FWHM is too narrow for the molecular clouds to be supported in the galaxy by dynamic pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. Roughly 10{sup 10} M {sub ☉} of molecular gas is projected 3-10 kpc to the northwest and to the east of the nucleus with line-of-sight velocities lying between –250 km s{sup –1} and +480 km s{sup –1} with respect to the systemic velocity. The high-velocity gas may be either inflowing or outflowing. However, the absence of high-velocity gas toward the nucleus that would be expected in a steady inflow, and its bipolar distribution on either side of the nucleus, are more naturally explained as outflow. Star formation and radiation from the active galactic nucleus (AGN) are both incapable of driving an outflow of this magnitude. The location of the high-velocity gas projected behind buoyantly rising X-ray cavities and favorable energetics suggest an outflow driven by the radio AGN. If so, the molecular outflow may be associated with a hot outflow on larger scales reported by Kirkpatrick and colleagues. The molecular gas flow rate of approximately 200 M {sub ☉} yr{sup –1} is comparable to the star formation rate of 100-180 M {sub ☉} yr{sup –1} in the central disk. How radio bubbles would lift dense molecular gas in their updrafts, how much gas will be lost to the BCG, and how much will return to fuel future star formation and AGN activity are poorly understood. Our results imply that radio-mechanical (radio-mode) feedback not only heats hot atmospheres surrounding elliptical galaxies and BCGs, but it is able to sweep higher density molecular gas away from their centers.

  13. Combustor liner cooling system

    DOEpatents

    Lacy, Benjamin Paul; Berkman, Mert Enis

    2013-08-06

    A combustor liner is disclosed. The combustor liner includes an upstream portion, a downstream end portion extending from the upstream portion along a generally longitudinal axis, and a cover layer associated with an inner surface of the downstream end portion. The downstream end portion includes the inner surface and an outer surface, the inner surface defining a plurality of microchannels. The downstream end portion further defines a plurality of passages extending between the inner surface and the outer surface. The plurality of microchannels are fluidly connected to the plurality of passages, and are configured to flow a cooling medium therethrough, cooling the combustor liner.

  14. Cool Vest

    NASA Technical Reports Server (NTRS)

    1982-01-01

    ILC, Dover Division's lightweight cooling garment, called Cool Vest was designed to eliminate the harmful effects of heat stress; increases tolerance time in hot environments by almost 300 percent. Made of urethane-coated nylon used in Apollo, it works to keep the body cool, circulating chilled water throughout the lining by means of a small battery-powered pump. A pocket houses the pump, battery and the coolant which can be ice or a frozen gel, a valve control allows temperature regulation. One version is self-contained and portable for unrestrained movement, another has an umbilical line attached to an external source of coolant, such as standard tap water, when extended mobility is not required. It is reported from customers that the Cool Vest pays for itself in increased productivity in very high temperatures.

  15. Cool School.

    ERIC Educational Resources Information Center

    Stephens, Suzanne

    1980-01-01

    The design for Floyd Elementary School in Miami (Florida) seeks to harness solar energy to provide at least 70 percent of the annual energy for cooling needs and 90 percent for hot water. (Author/MLF)

  16. The Radio Properties of Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Hogan, M. T.

    2014-09-01

    Energetic feedback from the Active Galactic Nucleus (AGN) of the Brightest Cluster Galaxy (BCG) is required to prevent catastrophic cooling of the intra-cluster medium (ICM) in galaxy clusters. Evidence for this is seen through the inflation of cavities in the ICM by AGN-launched, radio-emitting jets, and understanding this process is an active area of research. Radio observations play an integral role in this, as they trace the active stages of the feedback cycle. Understanding the radio properties of BCGs is therefore paramount for understanding both galaxy clusters and AGN feedback processes globally. Within this thesis, the BCGs in a large (>700) sample of X-ray selected clusters are studied. We observe these BCGs with a wide variety of facilities, building a census of their radio properties across a range of frequencies, timescales and angular resolutions. Radio spectral energy distributions (SEDs) are built for over 200 BCGs, and then decomposed into two components; a core, attributable to ongoing nuclear activity, and a non-core, attributable to historical accretion. Both components are not only more common, but also significantly more powerful in cool-core (CC) clusters than non-cool core (NCC) clusters. However, it is the presence of an active core that shows BCGs in CC clusters are constantly `on' - explaining how they regulate their environments over gigayear timescales. We observe 35 currently active BCGs at high (15-353 GHz) radio frequencies, and monitor their variability. Self-absorbed, active components are found to be common at high frequency. Little variability is seen on < year timescales, although longer term variation of ~10% annually over few-decade timescales is observed. Evidence is presented for a hitherto unseen component in BCG spectra that may be attributable to a naked Advection Dominated Accretion Flow (ADAF). The milli-arcsecond scale radio properties of 59 sources are studied, with a large range of morphologies recovered although no

  17. Turbine stator vane segment having internal cooling circuits

    DOEpatents

    Jones, Raymond Joseph; Burns, James Lee; Bojappa, Parvangada Ganapathy; Jones, Schotsch Margaret

    2003-01-01

    A turbine stator vane includes outer and inner walls each having outer and inner chambers and a vane extending between the outer and inner walls. The vane includes first, second, third, fourth and fifth cavities for flowing a cooling medium. The cooling medium enters the outer chamber of the outer wall, flows through an impingement plate for impingement cooling of the outer band wall defining in part the hot gas path and through openings in the first, second and fourth cavities for flow radially inwardly, cooling the vane. The spent cooling medium flows into the inner wall and inner chamber for flow through an impingement plate radially outwardly to cool the inner wall. The spent cooling medium flows through the third cavity for egress from the turbine vane segment from the outer wall. The first, second or third cavities contain inserts having impingement openings for impingement cooling of the vane walls. The fifth cavity provides air cooling for the trailing edge.

  18. Observations of Distant Clusters

    NASA Technical Reports Server (NTRS)

    Donahue, Megan

    2004-01-01

    The is the proceedings and papers supported by the LTSA grant: Homer, D. J.\\& Donahue, M. 2003, in "The Emergence of Cosmic Structure": 13'h Astrophysics Conference Proceedings, Vol. 666,3 1 1-3 14, (AIP). Baumgartner, W. H., Loewenstein, M., Horner, D. J., Mushotzky, R. F. 2003, HEAD- AAS, 35.3503. Homer, D. J. , Donahue, M., Voit G. M. 2003, HEAD-AAS, 35.1309. Nowak, M. A., Smith, B., Donahue, M., Stocke, J. 2003, HEAD-AAS, 35.1316. Scott, D., Borys, C., Chapman, S. C., Donahue, M., Fahlman, G. G., Halpem, M. Newbury, P. 2002, AAS, 128.01. Jones, L. R. et al. 2002, A new era in cosmology, ASP Conference Proceedings, Vol. 283, p. 223 Donahue, M., Daly, R. A., Homer, D. J. 2003, ApJ, 584, 643, Constraints on the Cluster Environments and Hotspot magnetic field strengths for radio sources 3280 and 3254. Donahue, M., et al. 2003, ApJ, 598, 190. The mass, baryonic fraction, and x-ray temperature of the luminous, high-redshift cluster of galaxies MS045 1.6-0305 Perlman, E. S. et al. 2002, ApJS, 140, 256. Smith, B. J., Nowak, M., Donahue, M., Stocke, J. 2003, AJ, 126, 1763. Chandra Observations of the Interacting NGC44 10 Group of Galaxies. Postman, M., Lauer, T. R., Oegerle, W., Donahue, M. 2002, ApJ, 579, 93. The KPNO/deep-range cluster survey I. The catalog and space density of intermediate-redshift clusters. Molnar, S. M., Hughes, J. P., Donahue, M., Joy, M. 2002, ApJ, 573, L91, Chandra Observations of Unresolved X-Ray Sources around Two Clusters of Galaxies. Donahue, M., Mack, J., 2002 NewAR, 46, 155, HST NIcmos and WFPC2 observations of molecular hydrogen and dust around cooling flows. Koekemoer, A. M. et al. 2002 NewAR, 46, 149, Interactions between the A2597 central radio source and dense gas host galaxy. Donahue, M. et al. 2002 ApJ, 569,689, Distant cluster hunting II.

  19. Hydrogen film/conductive cooling

    NASA Technical Reports Server (NTRS)

    Ewen, R. L.

    1972-01-01

    Small scale nozzle tests using heated nitrogen were run to obtain effectiveness and wall heat transfer data with hydrogen film cooling. Effectiveness data are compared with an entrainment model developed from planar, unaccelerated flow data. Results indicate significant effects due to flow turning and acceleration. With injection velocity effects accounted for explicitly, heat transfer correlation coefficients were found to be the same with and without film cooling when properties are evaluated at an appropriate reference temperature for the local gas composition defined by the coolant effectiveness. A design study for an O2/H2 application with 300 psia (207 N/sq cm) chamber pressure and 1500 lbs (6670 N) thrust indicates an adiabatic wall design requires 4 to 5 percent of the total flow as hydrogen film cooling. Internal regenerative cooling designs were found to offer no reduction in coolant requirements.

  20. When clusters collide - A numerical Hydro/N-body simulation of merging galaxy clusters

    NASA Technical Reports Server (NTRS)

    Roettiger, Kurt; Burns, Jack; Loken, Chris

    1993-01-01

    A 3D numerical simulation of two merging clusters of galaxies, using a hybrid Hydro/N-body code, is presented. The hydrodynamics of the code is solved by an Eulerian finite difference method. Initial results disclose that the X-ray emission of the dominant cluster becomes elongated and broadened; heating occurs at the core of the dominant cluster as a result of multiple shocks, and high velocity gas motions within the intracluster medium. It is predicted that clusters which have undergone recent mergers and do not have cooling flows will have high peculiar gas velocities and that the shocks and turbulence generated during the merger may power cluster-wide radio halos. Prolonged high-velocity gas motions through the dominant cluster core possibly play a major role in the formation and shaping of wide-angle tailed radio sources associated with central dominant galaxies. The N-body component of the simulation reveals the subcluster to be dispersed as it passes through the dominant cluster.

  1. Film cooling air pocket in a closed loop cooled airfoil

    DOEpatents

    Yu, Yufeng Phillip; Itzel, Gary Michael; Osgood, Sarah Jane; Bagepalli, Radhakrishna; Webbon, Waylon Willard; Burdgick, Steven Sebastian

    2002-01-01

    Turbine stator vane segments have radially inner and outer walls with vanes extending between them. The inner and outer walls are compartmentalized and have impingement plates. Steam flowing into the outer wall plenum passes through the impingement plate for impingement cooling of the outer wall upper surface. The spent impingement steam flows into cavities of the vane having inserts for impingement cooling the walls of the vane. The steam passes into the inner wall and through the impingement plate for impingement cooling of the inner wall surface and for return through return cavities having inserts for impingement cooling of the vane surfaces. To provide for air film cooing of select portions of the airfoil outer surface, at least one air pocket is defined on a wall of at least one of the cavities. Each air pocket is substantially closed with respect to the cooling medium in the cavity and cooling air pumped to the air pocket flows through outlet apertures in the wall of the airfoil to cool the same.

  2. Forced flow He vapor cooled critical current testing facility for measurements of superconductors in a wide temperature and magnetic field range

    NASA Astrophysics Data System (ADS)

    Baskys, Algirdas; Hopkins, Simon C.; Bader, Jakob; Glowacki, Bartek A.

    2016-10-01

    As superconducting materials find their way into applications, there is increasing need to verify their performance at operating conditions. Testing of critical current with respect to temperature and magnetic field is of particular importance. However, testing facilities covering a range of temperatures and magnetic fields can be costly, especially when considering the cooling power required in the cryogenic system in the temperature range below 65 K (inaccessible for LN2). Critical currents in excess of 500 A are common for commercial samples, making the testing of such samples difficult in setups cooled via a cryocooler, moreover it often does not represent the actual cooling conditions that the sample will experience in service. This work reports the design and operation of a low-cost critical current testing facility, capable of testing samples in a temperature range of 10-65 K, with magnetic field up to 1.6 T and measuring critical currents up to 900 A with variable cooling power.

  3. Cooling Vest

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Because quadriplegics are unable to perspire below the level of spinal injury, they cannot tolerate heat stress. A cooling vest developed by Ames Research Center and Upjohn Company allows them to participate in outdoor activities. The vest is an adaptation of Ames technology for thermal control garments used to remove excess body heat of astronauts. The vest consists of a series of corrugated channels through which cooled water circulates. Its two outer layers are urethane coated nylon, and there is an inner layer which incorporates the corrugated channels. It can be worn as a backpack or affixed to a wheelchair. The unit includes a rechargeable battery, mini-pump, two quart reservoir and heat sink to cool the water.

  4. Cooled railplug

    DOEpatents

    Weldon, W.F.

    1996-05-07

    The railplug is a plasma ignitor capable of injecting a high energy plasma jet into a combustion chamber of an internal combustion engine or continuous combustion system. An improved railplug is provided which has dual coaxial chambers (either internal or external to the center electrode) that provide for forced convective cooling of the electrodes using the normal pressure changes occurring in an internal combustion engine. This convective cooling reduces the temperature of the hot spot associated with the plasma initiation point, particularly in coaxial railplug configurations, and extends the useful life of the railplug. The convective cooling technique may also be employed in a railplug having parallel dual rails using dual, coaxial chambers. 10 figs.

  5. Transpiration And Regenerative Cooling Of Rocket Engine

    NASA Technical Reports Server (NTRS)

    Obrien, Charles J.

    1989-01-01

    Transpiration cooling extends limits of performance. Addition of transpiration cooling to regeneratively-cooled rocket-engine combustion chamber proposed. Modification improves performance of engine by allowing use of higher chamber pressure. Throat section of combustion-chamber wall cooled by transpiration, while chamber and nozzle sections cooled by fluid flowing in closed channels. Concept applicable to advanced, high-performance terrestrial engines or some kinds of industrial combustion chambers. With proper design, cooling scheme makes possible to achieve higher chamber pressure and higher overall performance in smaller engine.

  6. Multi-pass cooling for turbine airfoils

    DOEpatents

    Liang, George

    2011-06-28

    An airfoil for a turbine vane of a gas turbine engine. The airfoil includes an outer wall having pressure and suction sides, and a radially extending cooling cavity located between the pressure and suction sides. A plurality of partitions extend radially through the cooling cavity to define a plurality of interconnected cooling channels located at successive chordal locations through the cooling cavity. The cooling channels define a serpentine flow path extending in the chordal direction. Further, the cooling channels include a plurality of interconnected chambers and the chambers define a serpentine path extending in the radial direction within the serpentine path extending in the chordal direction.

  7. Keeping Cool.

    ERIC Educational Resources Information Center

    Kehrer, James

    2000-01-01

    Explores roofing options that can help control energy costs through use of highly reflective roofing materials. Additionally discussed is the "Urban Heat Island" phenomenon created when several super-heated buildings are clustered in a small area. (GR)

  8. Chemical Enrichment in the Third Closest Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    Million, Evan

    2011-10-01

    We propose a 180 ks XMM-Newton observation of the Antlia Cluster, the third closest galaxy cluster in the sky. We will determine the central temperature, Si and Fe abundance structure of the cluster to constrain detailed chemical enrichment processes in the nearest cluster without a strong cool core. The detailed abundance structure of the cluster will be resolved at the best physical resolution of any non-cool core cluster to date.

  9. Advanced liner-cooling techniques for gas turbine combustors

    NASA Technical Reports Server (NTRS)

    Norgren, C. T.; Riddlebaugh, S. M.

    1985-01-01

    Component research for advanced small gas turbine engines is currently underway at the NASA Lewis Research Center. As part of this program, a basic reverse-flow combustor geometry was being maintained while different advanced liner wall cooling techniques were investigated. Performance and liner cooling effectiveness of the experimental combustor configuration featuring counter-flow film-cooled panels is presented and compared with two previously reported combustors featuring: splash film-cooled liner walls; and transpiration cooled liner walls (Lamilloy).

  10. Superconducting magnet cooling system

    DOEpatents

    Vander Arend, Peter C.; Fowler, William B.

    1977-01-01

    A device is provided for cooling a conductor to the superconducting state. The conductor is positioned within an inner conduit through which is flowing a supercooled liquid coolant in physical contact with the conductor. The inner conduit is positioned within an outer conduit so that an annular open space is formed therebetween. Through the annular space is flowing coolant in the boiling liquid state. Heat generated by the conductor is transferred by convection within the supercooled liquid coolant to the inner wall of the inner conduit and then is removed by the boiling liquid coolant, making the heat removal from the conductor relatively independent of conductor length.

  11. Compact photomultiplier housing with controlled cooling.

    NASA Technical Reports Server (NTRS)

    SHARDANAND

    1972-01-01

    Description of a compact photomultiplier housing which can provide controlled cooling to the photomultiplier tube down to -90 C. The cooling is accomplished by flowing liquid nitrogen cooled helium gas through a series of coils which envelop the photocathode portion of the tube. The temperature is controlled by controlling the flow of the gas with a fine adjustable needle valve. The temperature is measured near the photocathode of the photomultiplier by a calibrated thermistor.

  12. IONIZED GAS KINEMATICS AT HIGH RESOLUTION. V. [Ne ii], MULTIPLE CLUSTERS, HIGH EFFICIENCY STAR FORMATION, AND BLUE FLOWS IN HE 2–10

    SciTech Connect

    Beck, Sara; Turner, Jean; Lacy, John; Greathouse, Thomas

    2015-11-20

    We measured the 12.8 μm [Ne ii] line in the dwarf starburst galaxy He 2–10 with the high-resolution spectrometer TEXES on the NASA IRTF. The data cube has a diffraction-limited spatial resolution of ∼1″ and a total velocity resolution, including thermal broadening, of ∼5 km s{sup −1}. This makes it possible to compare the kinematics of individual star-forming clumps and molecular clouds in the three dimensions of space and velocity, and allows us to determine star formation efficiencies. The kinematics of the ionized gas confirm that the starburst contains multiple dense clusters. From the M/R of the clusters and the ≃30%–40% star formation efficiencies, the clusters are likely to be bound and long lived, like globulars. Non-gravitational features in the line profiles show how the ionized gas flows through the ambient molecular material, as well as a narrow velocity feature, which we identify with the interface of the H ii region and a cold dense clump. These data offer an unprecedented view of the interaction of embedded H ii regions with their environment.

  13. IDAHO NATIONAL LABORATORY PROGRAM TO OBTAIN BENCHMARK DATA ON THE FLOW PHENOMENA IN A SCALED MODEL OF A PRISMATIC GAS-COOLED REACTOR LOWER PLENUM FOR THE VALIDATION OF CFD CODES

    SciTech Connect

    Hugh M. McIlroy Jr.; Donald M. McEligot; Robert J. Pink

    2008-09-01