Very High Density of Chinese Hamster Ovary Cells in Perfusion by Alternating Tangential Flow or Tangential Flow Filtration in WAVE Bioreactor™—Part II: Applications for Antibody Production and Cryopreservation

PubMed Central

Clincke, Marie-Françoise; Mölleryd, Carin; Samani, Puneeth K; Lindskog, Eva; Fäldt, Eric; Walsh, Kieron; Chotteau, Véronique

2013-01-01

A high cell density perfusion process of monoclonal antibody (MAb) producing Chinese hamster ovary (CHO) cells was developed in disposable WAVE Bioreactor™ using external hollow fiber (HF) filter as cell separation device. Tangential flow filtration (TFF) and alternating tangential flow (ATF) systems were compared and process applications of high cell density perfusion were studied here: MAb production and cryopreservation. Operations by perfusion using microfiltration (MF) or ultrafiltration (UF) with ATF or TFF and by fed-batch were compared. Cell densities higher than 108 cells/mL were obtained using UF TFF or UF ATF. The cells produced comparable amounts of MAb in perfusion by ATF or TFF, MF or UF. MAbs were partially retained by the MF using ATF or TFF but more severely using TFF. Consequently, MAbs were lost when cell broth was discarded from the bioreactor in the daily bleeds. The MAb cell-specific productivity was comparable at cell densities up to 1.3 × 108 cells/mL in perfusion and was comparable or lower in fed-batch. After 12 days, six times more MAbs were harvested using perfusion by ATF or TFF with MF or UF, compared to fed-batch and 28× more in a 1-month perfusion at 108 cells/mL density. Pumping at a recirculation rate up to 2.75 L/min did not damage the cells with the present TFF settings with HF short circuited. Cell cryopreservation at 0.5 × 108 and 108 cells/mL was performed using cells from a perfusion run at 108 cells/mL density. Cell resuscitation was very successful, showing that this system was a reliable process for cell bank manufacturing. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:768–777, 2013 PMID:23436783

Three Dimensional Solution of Pneumatic Active Control of Forebody Vortex Asymmetry

NASA Technical Reports Server (NTRS)

Kandil, Osama A.; SharafEl-Din, Hazem H.; Liu, C. H.

1995-01-01

Pneumatic active control of asymmetric vortical flows around a slender pointed forebody is investigated using the three dimensional solution for the compressible thin-layer Navier-Stokes equation. The computational applications cover the normal and tangential injection control of asymmetric flows around a 5 degree semi-apex angle cone at a 40 degree angle of attack, 1.4 freestream Mach number and 6 x 10(exp 6) freestream Reynolds number (based on the cone length). The effective tangential angle range of 67.5 approaches minus 67.5 degrees is used for both normal and tangential ports of injection. The effective axial length of injection is varied from 0.03 to 0.05. The computational solver uses the implicit, upwind, flux difference splitting finite volume scheme, and the grid consists of 161 x 55 x 65 points in the wrap around, normal and axial directions, respectively. The results show that tangential injection is more effective than normal injection.

Microalgae fractionation using steam explosion, dynamic and tangential cross-flow membrane filtration.

PubMed

Lorente, E; Hapońska, M; Clavero, E; Torras, C; Salvadó, J

2017-08-01

In this study, the microalga Nannochloropsis gaditana was subjected to acid catalysed steam explosion treatment and the resulting exploded material was subsequently fractionated to separate the different fractions (lipids, sugars and solids). Conventional and vibrational membrane setups were used with several polymeric commercial membranes. Two different routes were followed: 1) filtration+lipid solvent extraction and 2) lipid solvent extraction+filtration. Route 1 revealed to be much better since the used membrane for filtration was able to permeate the sugar aqueous phase and retained the fraction containing lipids; after this, an extraction required a much lower amount of solvent and a better recovering yield. Filtration allowed complete lipid rejection. Dynamic filtration improved permeability compared to the tangential cross-flow filtration. Best membrane performance was achieved using a 5000Da membrane with the dynamic system, obtaining a permeability of 6L/h/m 2 /bar. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tangential-flow ultrafiltration with integrated inhibition detection for recovery of surrogates and human pathogens from large-volume source water and finished drinking water.

PubMed

Gibson, Kristen E; Schwab, Kellogg J

2011-01-01

Tangential-flow ultrafiltration was optimized for the recovery of Escherichia coli, Enterococcus faecalis, Clostridium perfringens spores, bacteriophages MS2 and PRD1, murine norovirus, and poliovirus seeded into 100-liter surface water (SW) and drinking water (DW) samples. SW and DW collected from two drinking water treatment plants were then evaluated for human enteric viruses.

Reciprocal Inhibitory Connections Within a Neural Network for Rotational Optic-Flow Processing

PubMed Central

Haag, Juergen; Borst, Alexander

2007-01-01

Neurons in the visual system of the blowfly have large receptive fields that are selective for specific optic flow fields. Here, we studied the neural mechanisms underlying flow–field selectivity in proximal Vertical System (VS)-cells, a particular subset of tangential cells in the fly. These cells have local preferred directions that are distributed such as to match the flow field occurring during a rotation of the fly. However, the neural circuitry leading to this selectivity is not fully understood. Through dual intracellular recordings from proximal VS cells and other tangential cells, we characterized the specific wiring between VS cells themselves and between proximal VS cells and horizontal sensitive tangential cells. We discovered a spiking neuron (Vi) involved in this circuitry that has not been described before. This neuron turned out to be connected to proximal VS cells via gap junctions and, in addition, it was found to be inhibitory onto VS1. PMID:18982122

An experimental and numerical study of endwall heat transfer in a turbine blade cascade including tangential heat conduction analysis

NASA Astrophysics Data System (ADS)

Ratto, Luca; Satta, Francesca; Tanda, Giovanni

2018-06-01

This paper presents an experimental and numerical investigation of heat transfer in the endwall region of a large scale turbine cascade. The steady-state liquid crystal technique has been used to obtain the map of the heat transfer coefficient for a constant heat flux boundary condition. In the presence of two- and three-dimensional flows with significant spatial variations of the heat transfer coefficient, tangential heat conduction could lead to error in the heat transfer coefficient determination, since local heat fluxes at the wall-to-fluid interface tend to differ from point to point and surface temperatures to be smoothed out, thus making the uniform-heat-flux boundary condition difficult to be perfectly achieved. For this reason, numerical simulations of flow and heat transfer in the cascade including the effect of tangential heat conduction inside the endwall have been performed. The major objective of numerical simulations was to investigate the influence of wall heat conduction on the convective heat transfer coefficient determined during a nominal iso-flux heat transfer experiment and to interpret possible differences between numerical and experimental heat transfer results. Results were presented and discussed in terms of local Nusselt number and a convenient wall heat flux function for two values of the Reynolds number (270,000 and 960,000).

Purged window apparatus utilizing heated purge gas

DOEpatents

Ballard, Evan O.

1984-01-01

A purged window apparatus utilizing tangentially injected heated purge gases in the vicinity of electromagnetic radiation transmitting windows, and a tapered external mounting tube to accelerate these gases to provide a vortex flow on the window surface and a turbulent flow throughout the mounting tube. Use of this apparatus prevents backstreaming of gases under investigation which are flowing past the mouth of the mounting tube which would otherwise deposit on the windows. Lengthy spectroscopic investigations and analyses can thereby be performed without the necessity of interrupting the procedures in order to clean or replace contaminated windows.

Flow-Based Assembly of Layer-by-Layer Capsules through Tangential Flow Filtration.

PubMed

Björnmalm, Mattias; Roozmand, Ali; Noi, Ka Fung; Guo, Junling; Cui, Jiwei; Richardson, Joseph J; Caruso, Frank

2015-08-25

Layer-by-layer (LbL) assembly on nano- and microparticles is of interest for a range of applications, including catalysis, optics, sensors, and drug delivery. One current limitation is the standard use of manual, centrifugation-based (pellet/resuspension) methods to perform the layering steps, which can make scalable, highly controllable, and automatable production difficult to achieve. Here, we develop a fully flow-based technique using tangential flow filtration (TFF) for LbL assembly on particles. We demonstrate that multilayered particles and capsules with different sizes (from micrometers to submicrometers in diameter) can be assembled on different templates (e.g., silica and calcium carbonate) using several polymers (e.g., poly(allylamine hydrochloride), poly(styrenesulfonate), and poly(diallyldimethylammonium chloride)). The full system only contains fluidic components routinely used (and automated) in industry, such as pumps, tanks, valves, and tubing in addition to the TFF filter modules. Using the TFF LbL system, we also demonstrate the centrifugation-free assembly, including core dissolution, of drug-loaded capsules. The well-controlled, integrated, and automatable nature of the TFF LbL system provides scientific, engineering, and practical processing benefits, making it valuable for research environments and potentially useful for translating LbL assembled particles into diverse applications.

Numerical analysis of MHD Casson Navier's slip nanofluid flow yield by rigid rotating disk

NASA Astrophysics Data System (ADS)

Rehman, Khalil Ur; Malik, M. Y.; Zahri, Mostafa; Tahir, M.

2018-03-01

An exertion is perform to report analysis on Casson liquid equipped above the rigid disk for z bar > 0 as a semi-infinite region. The flow of Casson liquid is achieve through rotation of rigid disk with constant angular frequency Ω bar . Magnetic interaction is consider by applying uniform magnetic field normal to the axial direction. The nanosized particles are suspended in the Casson liquid and rotation of disk is manifested with Navier's slip condition, heat generation/absorption and chemical reaction effects. The obtain flow narrating differential equations subject to MHD Casson nanofluid are transformed into ordinary differential system. For this purpose the Von Karman way of scheme is executed. To achieve accurate trends a computational algorithm is develop rather than to go on with usual build-in scheme. The effects logs of involved parameters, namely magnetic field parameter, Casson fluid parameter, slip parameter, thermophoresis and Brownian motion parameters on radial, tangential velocities, temperature, nanoparticles concentration, Nusselt and Sherwood numbers are provided by means of graphical and tabular structures. It is observed that both tangential and radial velocities are decreasing function of Casson fluid parameter.

Slipping and tangential discontinuity instabilities in quasi-one-dimensional planar and cylindrical flows

NASA Astrophysics Data System (ADS)

Kuzelev, M. V.

2017-09-01

An analytical linear theory of instability of an electron beam with a nonuniform directional velocity (slipping instability) against perturbations with wavelengths exceeding the transverse beam size is offered. An analogy with hydrodynamic instabilities of tangential discontinuity of an incompressible liquid flow is drawn. The instability growth rates are calculated for particular cases and in a general form in planar and cylindrical geometries. The stabilizing effect of the external magnetic field is analyzed.

Assessment of Geometry and In-Flow Effects on Contra-Rotating Open Rotor Broadband Noise Predictions

NASA Technical Reports Server (NTRS)

Zawodny, Nikolas S.; Nark, Douglas M.; Boyd, D. Douglas, Jr.

2015-01-01

Application of previously formulated semi-analytical models for the prediction of broadband noise due to turbulent rotor wake interactions and rotor blade trailing edges is performed on the historical baseline F31/A31 contra-rotating open rotor configuration. Simplified two-dimensional blade element analysis is performed on cambered NACA 4-digit airfoil profiles, which are meant to serve as substitutes for the actual rotor blade sectional geometries. Rotor in-flow effects such as induced axial and tangential velocities are incorporated into the noise prediction models based on supporting computational fluid dynamics (CFD) results and simplified in-flow velocity models. Emphasis is placed on the development of simplified rotor in-flow models for the purpose of performing accurate noise predictions independent of CFD information. The broadband predictions are found to compare favorably with experimental acoustic results.

Cyclone reactor with internal separation and axial recirculation

DOEpatents

Becker, F.E.; Smolensky, L.A.

1988-07-19

A cyclone combustor apparatus contains a circular partition plate containing a central circular aperture is described. The partition plate divides the apparatus into a cylindrical precombustor chamber and a combustor chamber. A coal-water slurry is passed axially into the inlet end of the precombustor chamber, and primary air is passed tangentially into said chamber to establish a cyclonic air flow. Combustion products pass through the partition plate aperture and into the combustor chamber. Secondary air may also be passed tangentially into the combustor chamber adjacent the partition plate to maintain the cyclonic flow. Flue gas is passed axially out of the combustor chamber at the outlet end and ash is withdrawn tangentially from the combustor chamber at the outlet end. A first mixture of flue gas and ash may be tangentially withdrawn from the combustor chamber at the outlet end and recirculated to the axial inlet of the precombustor chamber with the coal-water slurry. A second mixture may be tangentially withdrawn from the outlet end and passed to a heat exchanger for cooling. Cooled second mixture is then recirculated to the axial inlet of the precombustor chamber. In another embodiment a single cyclone combustor chamber is provided with both the recirculation streams of the first mixture and the second mixture. 10 figs.

Cyclone reactor with internal separation and axial recirculation

DOEpatents

Becker, Frederick E.; Smolensky, Leo A.

1989-01-01

A cyclone combustor apparatus contains a circular partition plate containing a central circular aperture. The partition plate divides the apparatus into a cylindrical precombustor chamber and a combustor chamber. A coal-water slurry is passed axially into the inlet end of the precombustor chamber, and primary air is passed tangentially into said chamber to establish a cyclonic air flow. Combustion products pass through the partition plate aperture and into the combustor chamber. Secondary air may also be passed tangentially into the combustor chamber adjacent the partition plate to maintain the cyclonic flow. Flue gas is passed axially out of the combustor chamber at the outlet end and ash is withdrawn tangentially from the combuston chamber at the outlet end. A first mixture of flue gas and ash may be tangentially withdrawn from the combustor chamber at the outlet end and recirculated to the axial inlet of the precombustor chamber with the coal-water slurry. A second mixture of flue gas and ash may be tangentially withdrawn from the outlet end of the combustor chamber and passed to a heat exchanger for cooling. Cooled second mixture is then recirculated to the axial inlet of the precombustor chamber. In another embodiment a single cyclone combustor chamber is provided with both the recirculation streams of the first mixture and the second mixture.

Nonlinear interaction of a fast magnetogasdynamic shock with a tangential discontinuity

NASA Technical Reports Server (NTRS)

Neubauer, F. M.

1973-01-01

A basic problem, which is of considerable interest in geoastrophysical applications of magnetogasdynamics, is the nonlinear interaction of a fast shock (S sub f) with a tangential discontinuity (T). The problem is treated for an arbitrary S sub f interacting with an arbitrary T under the assumption that in the frame of reference in which S sub f and T are at rest, the flow is superfast on both sides of T, and that a steady flow develops. As a result of the nonlinear analysis a flow pattern is obtained consisting of the incident discontinuities S sub f 1 and T2 and a transmitted fast shock S sub f 3, the modified tangential discontinuity T4 and a reflected fast shock S sub f 5 or fast rarefaction wave R sub f 5. The results are discussed in terms of seven significant similarity parameters. In addition special cases like changes in magnetic field direction only, changes in desnity or velocity shear only etc. are discussed.

Energy harvesting through gas dynamics in the free molecular flow regime between structured surfaces at different temperatures

NASA Astrophysics Data System (ADS)

Baier, Tobias; Dölger, Julia; Hardt, Steffen

2014-05-01

For a gas confined between surfaces held at different temperatures the velocity distribution shows a significant deviation from the Maxwell distribution when the mean free path of the molecules is comparable to or larger than the channel dimensions. If one of the surfaces is suitably structured, this nonequilibrium distribution can be exploited for momentum transfer in a tangential direction between the two surfaces. This opens up the possibility to extract work from the system which operates as a heat engine. Since both surfaces are held at constant temperatures, the mode of momentum transfer is different from the thermal creep flow that has gained more attention so far. This situation is studied in the limit of free-molecular flow for the case that an unstructured surface is allowed to move tangentially with respect to a structured surface. Parameter studies are conducted, and configurations with maximum thermodynamic efficiency are identified. Overall, it is shown that significant efficiencies can be obtained by tangential momentum transfer between structured surfaces.

Energy harvesting through gas dynamics in the free molecular flow regime between structured surfaces at different temperatures.

PubMed

Baier, Tobias; Dölger, Julia; Hardt, Steffen

2014-05-01

For a gas confined between surfaces held at different temperatures the velocity distribution shows a significant deviation from the Maxwell distribution when the mean free path of the molecules is comparable to or larger than the channel dimensions. If one of the surfaces is suitably structured, this nonequilibrium distribution can be exploited for momentum transfer in a tangential direction between the two surfaces. This opens up the possibility to extract work from the system which operates as a heat engine. Since both surfaces are held at constant temperatures, the mode of momentum transfer is different from the thermal creep flow that has gained more attention so far. This situation is studied in the limit of free-molecular flow for the case that an unstructured surface is allowed to move tangentially with respect to a structured surface. Parameter studies are conducted, and configurations with maximum thermodynamic efficiency are identified. Overall, it is shown that significant efficiencies can be obtained by tangential momentum transfer between structured surfaces.

Effect of initial tangential velocity distribution on the mean evolution of a swirling turbulent free jet

NASA Technical Reports Server (NTRS)

Farokhi, S.; Taghavi, R.; Rice, E. J.

1988-01-01

An existing cold jet facility at NASA-Lewis was modified to produce swirling flows with controllable initial tangential velocity distribution. Distinctly different swirl velocity profiles were produced, and their effects on jet mixing characteristics were measured downstream of an 11.43 cm diameter convergent nozzle. It was experimentally shown that in the near field of a swirling turbulent jet, the mean velocity field strongly depends on the initial swirl profile. Two extreme tangential velocity distributions were produced. The two jets shared approximately the same initial mass flow rate of 5.9 kg/s, mass averaged axial Mach number and swirl number. Mean centerline velocity decay characteristics of the solid body rotation jet flow exhibited classical decay features of a swirling jet with S = 0.48 reported in the literature. It is concluded that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field.

A preliminary theoretical study of double blade two-dimensional aerodynamics for applications to vertical axis wind turbines

NASA Astrophysics Data System (ADS)

Weibust, E.

1981-04-01

A NASA model for computing the subsonic, viscous, attached flow around multielement airfoils was used to determine the amount of energy lost when using double blades rather than single ones. The resulting tangential force for the double or single blade configuration used as a criterion is found. Radial spacing, toe-in toe-out angle and tangential displacement (stagger) were varied to see how tagential force is affected. The greatest tangential force values are found to be achieved for maximum allowable radial spacing, which is determined by structural considerations, and is assumed to be on the order of 1.5 c. At this rather large distance, stagger as well as toe-in toe-out angle only gives slight improvements as long as the flow separation effects (stall region) are not considered. A large part of the energy is captured at relatively high wind speeds when the flow on the blades is partly separated (stalled).

Can the starpatch on Xi Bootis A be explained by using tangential flows?

NASA Technical Reports Server (NTRS)

Toner, Clifford G.; Labonte, Barry J.

1991-01-01

It is demonstrated that a modification of the starpatch model of Toner and Gray (1988), using tangential flows instead of an enhanced granulation velocity dispersion within the patch, is very successful at reproducing both the observed line asymmetry and the line broadening variations observed in the G8 dwarf Xi Boo A. Areal coverage of 10 percent + or - 3 percent of the visible disk, latitude 30 deg + or - 4 deg, mean brightness 0.85 + or - 0.05 relative to the 'quiet' photosphere, mean tangential flow velocities of 8.0 + or - 1.5 km/s, and dispersions about the mean of 8/0 + or - 2.0 km/s are inferred for the patch. A feature at a latitude of about 30 deg is inferred which covers about 10 percent of the visible disk and is 10-20 percent fainter than the rest of the photosphere. It is inferred that 70-80 percent of the patch is penumbra.

Acoustic streaming in simplified liquid rocket engines with transverse mode oscillations

NASA Astrophysics Data System (ADS)

Fischbach, Sean R.; Flandro, Gary A.; Majdalani, Joseph

2010-06-01

This study considers a simplified model of a liquid rocket engine in which uniform injection is imposed at the faceplate. The corresponding cylindrical chamber has a small length-to-diameter ratio with respect to solid and hybrid rockets. Given their low chamber aspect ratios, liquid thrust engines are known to experience severe tangential and radial oscillation modes more often than longitudinal ones. In order to model this behavior, tangential and radial waves are superimposed onto a basic mean-flow model that consists of a steady, uniform axial velocity throughout the chamber. Using perturbation tools, both potential and viscous flow equations are then linearized in the pressure wave amplitude and solved to the second order. The effects of the headwall Mach number are leveraged as well. While the potential flow analysis does not predict any acoustic streaming effects, the viscous solution carried out to the second order gives rise to steady secondary flow patterns near the headwall. These axisymmetric, steady contributions to the tangential and radial traveling waves are induced by the convective flow motion through interactions with inertial and viscous forces. We find that suppressing either the convective terms or viscosity at the headwall leads to spurious solutions that are free from streaming. In our problem, streaming is initiated at the headwall, within the boundary layer, and then extends throughout the chamber. We find that nonlinear streaming effects of tangential and radial waves act to alter the outer solution inside a cylinder with headwall injection. As a result of streaming, the radial wave velocities are intensified in one-half of the domain and reduced in the opposite half at any instant of time. Similarly, the tangential waves are either enhanced or weakened in two opposing sectors that are at 90° angle to the radial velocity counterparts. The second-order viscous solution that we obtain clearly displays both an oscillating and a steady flow component. The steady part can be an important contributor to wave steepening, a mechanism that is often observed during the onset of acoustic instability.

Hydrodynamic impeller stiffness, damping, and inertia in the rotordynamics of centrifugal flow pumps

NASA Technical Reports Server (NTRS)

Jery, S.; Acosta, A. J.; Brennen, C. E.; Caughey, T. K.

1984-01-01

The lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries were measured. The lateral forces were decomposed into: (1) time averaged lateral forces and (2) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. It is found that these force matrices essentially consist of equal diagonal terms and skew symmetric off diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; it is shown that there exists a region of positive reduced whirl frequencies, within which the hydrodynamic forces can be destablizing with respect to whirl.

A unified view of energetic efficiency in active drag reduction, thrust generation and self-propulsion through a loss coefficient with some applications

NASA Astrophysics Data System (ADS)

Arakeri, Jaywant H.; Shukla, Ratnesh K.

2013-08-01

An analysis of the energy budget for the general case of a body translating in a stationary fluid under the action of an external force is used to define a power loss coefficient. This universal definition of power loss coefficient gives a measure of the energy lost in the wake of the translating body and, in general, is applicable to a variety of flow configurations including active drag reduction, self-propulsion and thrust generation. The utility of the power loss coefficient is demonstrated on a model bluff body flow problem concerning a two-dimensional elliptical cylinder in a uniform cross-flow. The upper and lower boundaries of the elliptic cylinder undergo continuous motion due to a prescribed reflectionally symmetric constant tangential surface velocity. It is shown that a decrease in drag resulting from an increase in the strength of tangential surface velocity leads to an initial reduction and eventual rise in the power loss coefficient. A maximum in energetic efficiency is attained for a drag reducing tangential surface velocity which minimizes the power loss coefficient. The effect of the tangential surface velocity on drag reduction and self-propulsion of both bluff and streamlined bodies is explored through a variation in the thickness ratio (ratio of the minor and major axes) of the elliptical cylinders.

Drag reduction and thrust generation by tangential surface motion in flow past a cylinder

NASA Astrophysics Data System (ADS)

Mao, Xuerui; Pearson, Emily

2018-03-01

Sensitivity of drag to tangential surface motion is calculated in flow past a circular cylinder in both two- and three-dimensional conditions at Reynolds number Re ≤ 1000 . The magnitude of the sensitivity maximises in the region slightly upstream of the separation points where the contour lines of spanwise vorticity are normal to the cylinder surface. A control to reduce drag can be obtained by (negatively) scaling the sensitivity. The high correlation of sensitivities of controlled and uncontrolled flow indicates that the scaled sensitivity is a good approximation of the nonlinear optimal control. It is validated through direct numerical simulations that the linear range of the steady control is much higher than the unsteady control, which synchronises the vortex shedding and induces lock-in effects. The steady control injects angular momentum into the separating boundary layer, stabilises the flow and increases the base pressure significantly. At Re=100 , when the maximum tangential motion reaches 50% of the free-stream velocity, the vortex shedding, boundary-layer separation and recirculation bubbles are eliminated and 32% of the drag is reduced. When the maximum tangential motion reaches 2.5 times of the free-stream velocity, thrust is generated and the power savings ratio, defined as the ratio of the reduced drag power to the control input power, reaches 19.6. The mechanism of drag reduction is attributed to the change of the radial gradient of spanwise vorticity (partial r \\hat{ζ } ) and the subsequent accelerated pressure recovery from the uncontrolled separation points to the rear stagnation point.

Flow friction of the turbulent coolant flow in cryogenic porous cables

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Yeroshenko, V. M.; Zaichik, L. I.; Yanovsky, L. S.

1979-01-01

Considered are cryogenic power transmission cables with porous cores. Calculations of the turbulent coolant flow with injection or suction through the porous wall are presented within the framework of a two-layer model. Universal velocity profiles were obtained for the viscous sublayer and flow core. Integrating the velocity profile, the law of flow friction in the pipe with injection has been derived for the case when there is a tangential injection velocity component. The effect of tangential velocity on the relative law of flow friction is analyzed. The applicability of the Prandtl model to the problem under study is discussed. It is shown that the error due to the acceptance of the model increases with the injection parameter and at lower Reynolds numbers; under these circumstances, the influence of convective terms in the turbulent energy equation on the mechanism of turbulent transport should be taken into account.

Surface representations of two- and three-dimensional fluid flow topology

NASA Technical Reports Server (NTRS)

Helman, James L.; Hesselink, Lambertus

1990-01-01

We discuss our work using critical point analysis to generate representations of the vector field topology of numerical flow data sets. Critical points are located and characterized in a two-dimensional domain, which may be either a two-dimensional flow field or the tangential velocity field near a three-dimensional body. Tangent curves are then integrated out along the principal directions of certain classes of critical points. The points and curves are linked to form a skeleton representing the two-dimensional vector field topology. When generated from the tangential velocity field near a body in a three-dimensional flow, the skeleton includes the critical points and curves which provide a basis for analyzing the three-dimensional structure of the flow separation. The points along the separation curves in the skeleton are used to start tangent curve integrations to generate surfaces representing the topology of the associated flow separations.

A generalized quasi-geostrophic core flow formalism

NASA Astrophysics Data System (ADS)

Amit, H.; Coutelier, M.

2016-12-01

The quasi-geostrophic formalism provides a theoretical coupling between toroidal and poloidal core flows. By enforcing impermeable core-mantle boundary, conservation of mass and a linear variation of the axial flow along an axial column, this coupling can be written as div_h · u_h = c tan θ/R u_θ where u_h is the tangential velocity at the top of the core, θ is co-latitude, R is the core radius and c=2 (Amit and Olson, 2004; Amit and Pais, 2013). We extend this theory and develop this expression for different profiles of the axial flow. Our results show that the same expression holds but the value of c may vary depending on the profile of the axial flow, including c=1 as in the tangential geostrophy formalism. These results may therefore provide new constraints on quasi-geostrophic core flow inversions from geomagnetic SV.

NLS clutching bearing cavity flow analysis

NASA Technical Reports Server (NTRS)

Tran, Ken; Chan, Daniel C.; Darian, Armen

1992-01-01

A flow model of the NLS clutching bearing cavity was built for 2-D axisymmetric viscous analysis. From the computational fluid dynamics (CFD) approach, the tangential force exerted on the surfaces of the inner race was integrated to calculate the dividing torque which, in conjunction with the resistance torque, was used to predict the operating speed of the inner race. In order to further reduce the inner race rotation, the swirling flow at the cavity inlet was partially redirected to generate an opposing torque. Thirty six slanted slots were incorporated into the anti-vortex rib to achieve this goal. A 3-D flow analysis performed on this configuration indicates a drastic reduction of the driving torque and inner race RPM.

In-cylinder air-flow characteristics of different intake port geometries using tomographic PIV

NASA Astrophysics Data System (ADS)

Agarwal, Avinash Kumar; Gadekar, Suresh; Singh, Akhilendra Pratap

2017-09-01

For improving the in-cylinder flow characteristics of intake air/charge and for strengthening the turbulence intensity, specific intake port geometries have shown significant potential in compression ignition engines. In this experimental study, effects of intake port geometries on air-flow characteristics were investigated using tomographic particle imaging velocimetry (TPIV). Experiments were performed using three experimental conditions, namely, swirl port open (SPO), tangential port open (TPO), and both port open (BPO) configurations in a single cylinder optical research engine. Flow investigations were carried out in a volumetric section located in the middle of the intake and exhaust valves. Particle imaging velocimetry (PIV) images were captured using two high speed cameras at a crank angle resolution of 2° in the intake and compression strokes. The captured PIV images were then pre-processed and post-processed to obtain the final air-flow-field. Effects of these two intake ports on flow-field are presented for air velocity, vorticity, average absolute velocity, and turbulent kinetic energy. Analysis of these flow-fields suggests the dominating nature of the swirl port over the tangential port for the BPO configuration and higher rate of flow energy dissipation for the TPO configuration compared to the SPO and BPO configurations. These findings of TPIV investigations were experimentally verified by combustion and particulate characteristics of the test engine in thermal cylinder head configuration. Combustion results showed that the SPO configuration resulted in superior combustion amongst all three port configurations. Particulate characteristics showed that the TPO configuration resulted in higher particulate compared to other port configurations.

Exact solution for the layered convection of a viscous incompressible fluid at specified temperature gradients and tangential forces on the free boundary

NASA Astrophysics Data System (ADS)

Burmasheva, N. V.; Prosviryakov, E. Yu.

2017-12-01

A new exact analytical solution of a system of thermal convection equations in the Boussinesq approximation describing layered flows in an incompressible viscous fluid is obtained. A fluid flow in an infinite layer is considered. Convection in the fluid is induced by tangential stresses specified on the upper non-deformable boundary. At the fixed lower boundary, the no-slip condition is satisfied. Temperature corrections are given on the both boundaries of the fluid layer. The possibility of physical field stratification is investigated.

Injector Element which Maintains a Constant Mean Spray Angle and Optimum Pressure Drop During Throttling by Varying the Geometry of Tangential Inlets

NASA Technical Reports Server (NTRS)

Trinh, Huu P. (Inventor); Myers, William Neill (Inventor)

2014-01-01

A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The tangential inlet area for each throttleable stage is calculated. The correlation between the tangential inlet areas and delta pressure values is used to calculate the spring displacement and variable inlet geometry. An injector designed using the method includes a plurality of geometrically calculated tangential inlets in an injection tube; an injection tube cap with a plurality of inlet slots slidably engages the injection tube. A pressure differential across the injector element causes the cap to slide along the injection tube and variably align the inlet slots with the tangential inlets.

Computational analysis of forebody tangential slot blowing

NASA Technical Reports Server (NTRS)

Gee, Ken; Agosta-Greenman, Roxana M.; Rizk, Yehia M.; Schiff, Lewis B.; Cummings, Russell M.

1994-01-01

An overview of the computational effort to analyze forebody tangential slot blowing is presented. Tangential slot blowing generates side force and yawing moment which may be used to control an aircraft flying at high-angle-of-attack. Two different geometries are used in the analysis: (1) The High Alpha Research Vehicle; and (2) a generic chined forebody. Computations using the isolated F/A-18 forebody are obtained at full-scale wind tunnel test conditions for direct comparison with available experimental data. The effects of over- and under-blowing on force and moment production are analyzed. Time-accurate solutions using the isolated forebody are obtained to study the force onset timelag of tangential slot blowing. Computations using the generic chined forebody are obtained at experimental wind tunnel conditions, and the results compared with available experimental data. This computational analysis compliments the experimental results and provides a detailed understanding of the effects of tangential slot blowing on the flow field about simple and complex geometries.

Experimental Study on Effects of Ground Roughness on Flow Characteristics of Tornado-Like Vortices

NASA Astrophysics Data System (ADS)

Wang, Jin; Cao, Shuyang; Pang, Weichiang; Cao, Jinxin

2017-02-01

The three-dimensional wind velocity and dynamic pressure for stationary tornado-like vortices that developed over ground of different roughness categories were investigated to clarify the effects of ground roughness. Measurements were performed for various roughness categories and two swirl ratios. Variations of the vertical and horizontal distributions of velocity and pressure with roughness are presented, with the results showing that the tangential, radial, and axial velocity components increase inside the vortex core near the ground under rough surface conditions. Meanwhile, clearly decreased tangential components are found outside the core radius at low elevations. The high axial velocity inside the vortex core over rough ground surface indicates that roughness produces an effect similar to a reduced swirl ratio. In addition, the pressure drop accompanying a tornado is more significant at elevations closer to the ground under rough compared with smooth surface conditions. We show that the variations of the flow characteristics with roughness are dependent on the vortex-generating mechanism, indicating the need for appropriate modelling of tornado-like vortices.

The effect of forward skewed rotor blades on aerodynamic and aeroacoustic performance of axial-flow fan

NASA Astrophysics Data System (ADS)

Wei, Jun; Zhong, Fangyuan

Based on comparative experiment, this paper deals with using tangentially skewed rotor blades in axial-flow fan. It is seen from the comparison of the overall performance of the fan with skewed bladed rotor and radial bladed rotor that the skewed blades operate more efficiently than the radial blades, especially at low volume flows. Meanwhile, decrease in pressure rise and flow rate of axial-flow fan with skewed rotor blades is found. The rotor-stator interaction noise and broadband noise of axial-flow fan are reduced with skewed rotor blades. Forward skewed blades tend to reduce the accumulation of the blade boundary layer in the tip region resulting from the effect of centrifugal forces. The turning of streamlines from the outer radius region into inner radius region in blade passages due to the radial component of blade forces of skewed blades is the main reason for the decrease in pressure rise and flow rate.

Cylindrical Couette flow of a rarefied gas: Effect of a boundary condition on the inverted velocity profile.

PubMed

Kosuge, Shingo

2015-07-01

The cylindrical Couette flow of a rarefied gas between a rotating inner cylinder and a stationary outer cylinder is investigated under the following two kinds of kinetic boundary conditions. One is the modified Maxwell-type boundary condition proposed by Dadzie and Méolans [J. Math. Phys. 45, 1804 (2004)] and the other is the Cercignani-Lampis condition, both of which have separate accommodation coefficients associated with the molecular velocity component normal to the boundary and with the tangential component. An asymptotic analysis of the Boltzmann equation for small Knudsen numbers and a numerical analysis of the Bhatnagar-Gross-Krook model equation for a wide range of the Knudsen number are performed to clarify the effect of each accommodation coefficient as well as of the boundary condition itself on the behavior of the gas, especially on the flow-velocity profile. As a result, the velocity-slip and temperature-jump conditions corresponding to the above kinetic boundary conditions are derived, which are necessary for the fluid-dynamic description of the problem for small Knudsen numbers. The parameter range for the onset of the velocity inversion phenomenon, which is related mainly to the decrease in the tangential momentum accommodation, is also obtained.

Two-dimensional Cascade Investigation of the Maximum Exit Tangential Velocity Component and Other Flow Conditions at the Exit of Several Turbine Blade Designs at Supercritical Pressure Ratios

NASA Technical Reports Server (NTRS)

Hauser, Cavour H; Plohr, Henry W

1951-01-01

The nature of the flow at the exit of a row of turbine blades for the range of conditions represented by four different blade configurations was evaluated by the conservation-of-momentum principle using static-pressure surveys and by analysis of Schlieren photographs of the flow. It was found that for blades of the type investigated, the maximum exit tangential-velocity component is a function of the blade geometry only and can be accurately predicted by the method of characteristics. A maximum value of exit velocity coefficient is obtained at a pressure ratio immediately below that required for maximum blade loading followed by a sharp drop after maximum blade loading occurs.

Turbulence measurements of high shear flow fields in a turbomachine seal configuration

NASA Technical Reports Server (NTRS)

Morrison, Gerald L.; Deotte, Robert E., Jr.; Thames, H. Davis, III.

1992-01-01

The mean velocity and Reynolds stress tensor throughout a whirling annular seal are presented. The data was collected with a three dimensional laser Doppler velocimeter using phase averaging. Two axial flow conditions (Re = 12,000 and 24,000) were studied at one shaft speed (Ta = 6,600). The eccentricity and whirl ratios were 50 and 100 percent, respectively. There is a region of high axial momentum in this region is higher in the low Reynolds number case due to an axial recirculation zone that occurs on the suction side of the rotor at the inlet. The recirculation zone does not occur in the high Reynolds number case. At both Reynolds numbers, there is a recirculation zone on the rotor surface in the pressure side of the inlet. This recirculation zone extends from 20 to 200 degrees rotor zenith in the tangential direction, and is one third of a clearance wide radially. The high Reynolds number recirculation zone is 1.5 mean clearances long, while the low Reynolds number zone extends 2 mean clearances downstream. When compared to previous studies, it is apparent that the tangential momentum is no greater for a seal with whirl than for one without if other parameters are constant. Areas of high tangential momentum occur in the clearance where the axial momentum is low. Average exit plane tangential velocities in the high Reynolds number case are 1.5 times greater than those in the other flow case. These results are in general agreement with predictions made by other investigators.

Large-scale bedforms induced by supercritical flows and wave-wave interference in the intertidal zone (Cap Ferret, France)

NASA Astrophysics Data System (ADS)

Vaucher, Romain; Pittet, Bernard; Humbert, Thomas; Ferry, Serge

2017-11-01

The Cap Ferret sand spit is situated along the wave-dominated, tidally modulated Atlantic coast of western France, characterized by a semidiurnal macrotidal range. It displays peculiar dome-like bedforms that can be observed at low tide across the intertidal zone. These bedforms exhibit a wavelength of ca. 1.2 m and an elevation of ca. 30 cm. They occur only when the incident wave heights reach 1.5-2 m. The internal stratifications are characterized by swaley-like, sub-planar, oblique-tangential, oblique-tabular, as well as hummocky-like stratifications. The tabular and tangential stratifications comprise prograding oblique sets (defined as foresets and backsets) that almost always show variations in their steepness. Downcutting into the bottomsets of the oblique-tangential stratifications is common. The sets of laminae observed in the bedforms share common characteristics with those formed by supercritical flows in flume experiments of earlier studies. These peculiar bedforms are observed at the surf-swash transition zone where the backwash flow reaches supercritical conditions. This type of flow can explain their internal architecture but not their general dome-like (three-dimensional) morphology. Wave-wave interference induced by the geomorphology (i.e. tidal channel) of the coastal environment is proposed as explanation for the localized formation of such bedforms. This study highlights that the combination of supercritical flows occurring in the surf-swash transition zone and wave-wave interferences can generate dome-like bedforms in intertidal zones.

Large-scale bedforms induced by supercritical flows and wave-wave interference in the intertidal zone (Cap Ferret, France)

NASA Astrophysics Data System (ADS)

Vaucher, Romain; Pittet, Bernard; Humbert, Thomas; Ferry, Serge

2018-06-01

The Cap Ferret sand spit is situated along the wave-dominated, tidally modulated Atlantic coast of western France, characterized by a semidiurnal macrotidal range. It displays peculiar dome-like bedforms that can be observed at low tide across the intertidal zone. These bedforms exhibit a wavelength of ca. 1.2 m and an elevation of ca. 30 cm. They occur only when the incident wave heights reach 1.5-2 m. The internal stratifications are characterized by swaley-like, sub-planar, oblique-tangential, oblique-tabular, as well as hummocky-like stratifications. The tabular and tangential stratifications comprise prograding oblique sets (defined as foresets and backsets) that almost always show variations in their steepness. Downcutting into the bottomsets of the oblique-tangential stratifications is common. The sets of laminae observed in the bedforms share common characteristics with those formed by supercritical flows in flume experiments of earlier studies. These peculiar bedforms are observed at the surf-swash transition zone where the backwash flow reaches supercritical conditions. This type of flow can explain their internal architecture but not their general dome-like (three-dimensional) morphology. Wave-wave interference induced by the geomorphology (i.e. tidal channel) of the coastal environment is proposed as explanation for the localized formation of such bedforms. This study highlights that the combination of supercritical flows occurring in the surf-swash transition zone and wave-wave interferences can generate dome-like bedforms in intertidal zones.

Ratchet flow of thin liquid films induced by a two-frequency tangential forcing

NASA Astrophysics Data System (ADS)

Sterman-Cohen, Elad; Bestehorn, Michael; Oron, Alexander

2018-02-01

A possibility of saturating Rayleigh-Taylor instability in a thin liquid film on the underside of a substrate in the gravity field by harmonic vibration of the substrate was recently investigated [E. Sterman-Cohen, M. Bestehorn, and A. Oron, Phys. Fluids 29, 052105 (2017); Erratum, Phys. Fluids 29, 109901 (2017)]. In the present work, we investigate the feasibility of creating a directional flow of the fluid in a film in the Rayleigh-Taylor configuration and controlling its flow rate by applying a two-frequency tangential forcing to the substrate. It is shown that in this situation, a ratchet flow develops, and the dependence of its flow rate on the vibration frequency, amplitude, its periodicity, and asymmetry level is investigated for water and silicone-oil films. A cause for the emergence of symmetry-breaking and an ensuing flow in a preferred direction is discussed. Some aspects of a ratchet flow in a liquid film placed on top of the substrate are discussed as well. A comparison with the case of a neglected fluid inertia is made, and the differences are explained.

Tornado type wind turbines

DOEpatents

Hsu, Cheng-Ting

1984-01-01

A tornado type wind turbine has a vertically disposed wind collecting tower with spaced apart inner and outer walls and a central bore. The upper end of the tower is open while the lower end of the structure is in communication with a wind intake chamber. An opening in the wind chamber is positioned over a turbine which is in driving communication with an electrical generator. An opening between the inner and outer walls at the lower end of the tower permits radially flowing air to enter the space between the inner and outer walls while a vertically disposed opening in the wind collecting tower permits tangentially flowing air to enter the central bore. A porous portion of the inner wall permits the radially flowing air to interact with the tangentially flowing air so as to create an intensified vortex flow which exits out of the top opening of the tower so as to create a low pressure core and thus draw air through the opening of the wind intake chamber so as to drive the turbine.

Performance of a Compression-ignition Engine with a Precombustion Chamber Having High-Velocity Air Flow

NASA Technical Reports Server (NTRS)

Spanogle, J A; Moore, C S

1931-01-01

Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.

Reverse-Tangent Injection in a Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

2007-01-01

Injection of working fluid into a centrifugal compressor in the reverse tangent direction has been invented as a way of preventing flow instabilities (stall and surge) or restoring stability when stall or surge has already commenced. The invention applies, in particular, to a centrifugal compressor, the diffuser of which contains vanes that divide the flow into channels oriented partly radially and partly tangentially. In reverse-tangent injection, a stream or jet of the working fluid (the fluid that is compressed) is injected into the vaneless annular region between the blades of the impeller and the vanes of the diffuser. As used here, "reverse" signifies that the injected flow opposes (and thereby reduces) the tangential component of the velocity of the impeller discharge. At the same time, the injected jet acts to increase the radial component of the velocity of the impeller discharge.

Streakline-based closed-loop control of a bluff body flow

NASA Astrophysics Data System (ADS)

Roca, Pablo; Cammilleri, Ada; Duriez, Thomas; Mathelin, Lionel; Artana, Guillermo

2014-04-01

A novel closed-loop control methodology is introduced to stabilize a cylinder wake flow based on images of streaklines. Passive scalar tracers are injected upstream the cylinder and their concentration is monitored downstream at certain image sectors of the wake. An AutoRegressive with eXogenous inputs mathematical model is built from these images and a Generalized Predictive Controller algorithm is used to compute the actuation required to stabilize the wake by adding momentum tangentially to the cylinder wall through plasma actuators. The methodology is new and has real-world applications. It is demonstrated on a numerical simulation and the provided results show that good performances are achieved.

Performance characteristics of LOX-H2, tangential-entry, swirl-coaxial, rocket injectors

NASA Technical Reports Server (NTRS)

Howell, Doug; Petersen, Eric; Clark, Jim

1993-01-01

Development of a high performing swirl-coaxial injector requires an understanding of fundamental performance characteristics. This paper addresses the findings of studies on cold flow atomic characterizations which provided information on the influence of fluid properties and element operating conditions on the produced droplet sprays. These findings are applied to actual rocket conditions. The performance characteristics of swirl-coaxial injection elements under multi-element hot-fire conditions were obtained by analysis of combustion performance data from three separate test series. The injection elements are described and test results are analyzed using multi-variable linear regression. A direct comparison of test results indicated that reduced fuel injection velocity improved injection element performance through improved propellant mixing.

Investigation of the ellipsoidal-statistical Bhatnagar-Gross-Krook kinetic model applied to gas-phase transport of heat and tangential momentum between parallel walls

NASA Astrophysics Data System (ADS)

Gallis, M. A.; Torczynski, J. R.

2011-03-01

The ellipsoidal-statistical Bhatnagar-Gross-Krook (ES-BGK) kinetic model is investigated for steady gas-phase transport of heat, tangential momentum, and mass between parallel walls (i.e., Fourier, Couette, and Fickian flows). This investigation extends the original study of Cercignani and Tironi, who first applied the ES-BGK model to heat transport (i.e., Fourier flow) shortly after this model was proposed by Holway. The ES-BGK model is implemented in a molecular-gas-dynamics code so that results from this model can be compared directly to results from the full Boltzmann collision term, as computed by the same code with the direct simulation Monte Carlo (DSMC) algorithm of Bird. A gas of monatomic molecules is considered. These molecules collide in a pairwise fashion according to either the Maxwell or the hard-sphere interaction and reflect from the walls according to the Cercignani-Lampis-Lord model with unity accommodation coefficients. Simulations are performed at pressures from near-free-molecular to near-continuum. Unlike the BGK model, the ES-BGK model produces heat-flux and shear-stress values that both agree closely with the DSMC values at all pressures. However, for both interactions, the ES-BGK model produces molecular-velocity-distribution functions that are qualitatively similar to those determined for the Maxwell interaction from Chapman-Enskog theory for small wall temperature differences and moment-hierarchy theory for large wall temperature differences. Moreover, the ES-BGK model does not produce accurate values of the mass self-diffusion coefficient for either interaction. Nevertheless, given its reasonable accuracy for heat and tangential-momentum transport, its sound theoretical foundation (it obeys the H-theorem), and its available extension to polyatomic molecules, the ES-BGK model may be a useful method for simulating certain classes of single-species noncontinuum gas flows, as Cercignani suggested.

Roll-Yaw control at high angle of attack by forebody tangential blowing

NASA Technical Reports Server (NTRS)

Pedreiro, N.; Rock, S. M.; Celik, Z. Z.; Roberts, L.

1995-01-01

The feasibility of using forebody tangential blowing to control the roll-yaw motion of a wind tunnel model is experimentally demonstrated. An unsteady model of the aerodynamics is developed based on the fundamental physics of the flow. Data from dynamic experiments is used to validate the aerodynamic model. A unique apparatus is designed and built that allows the wind tunnel model two degrees of freedom, roll and yaw. Dynamic experiments conducted at 45 degrees angle of attack reveal the system to be unstable. The natural motion is divergent. The aerodynamic model is incorporated into the equations of motion of the system and used for the design of closed loop control laws that make the system stable. These laws are proven through dynamic experiments in the wind tunnel using blowing as the only actuator. It is shown that asymmetric blowing is a highly non-linear effector that can be linearized by superimposing symmetric blowing. The effects of forebody tangential blowing and roll and yaw angles on the flow structure are determined through flow visualization experiments. The transient response of roll and yaw moments to a step input blowing are determined. Differences on the roll and yaw moment dependence on blowing are explained based on the physics of the phenomena.

Roll-yaw control at high angle of attack by forebody tangential blowing

NASA Technical Reports Server (NTRS)

Pedreiro, N.; Rock, S. M.; Celik, Z. Z.; Roberts, L.

1995-01-01

The feasibility of using forebody tangential blowing to control the roll-yaw motion of a wind tunnel model is experimentally demonstrated. An unsteady model of the aerodynamics is developed based on the fundamental physics of the flow. Data from dynamic experiments is used to validate the aerodynamic model. A unique apparatus is designed and built that allows the wind tunnel model two degrees of freedom, roll and yaw. Dynamic experiments conducted at 45 degrees angle of attack reveal the system to be unstable. The natural motion is divergent. The aerodynamic model is incorporated into the equations of motion of the system and used for the design of closed loop control laws that make the system stable. These laws are proven through dynamic experiments in the wind tunnel using blowing as the only actuator. It is shown that asymmetric blowing is a highly non-linear effector that can be linearized by superimposing symmetric blowing. The effects of forebody tangential blowing and roll and yaw angles on the flow structure are determined through flow visualization experiments. The transient response of roll and yaw moments to a step input blowing are determined. Differences on the roll and yaw moment dependence on blowing are explained based on the physics of the phenomena.

An experimental and theoretical study of the flow phenomena within a vortex sink rate sensor

NASA Technical Reports Server (NTRS)

Goglia, G. L.; Patel, D. K.

1974-01-01

Tests were conducted to obtain a description of the flow field within a vortex sink rate sensor and to observe the influence of viscous effects on its performance. The characteristics of the sensor are described. The method for conducting the test is reported. It was determined that for a specific mass flow rate and the geometry of the vortex chamber, the flow in the vortex chamber was only affected, locally, by the size of the sink tube diameter. Within the sink tube, all three velocity components were found to be higher for the small sink tube diameters. As the speed of rotation of the sensor was increased, the tangential velocities within the vortex chamber, as well as in the sink tube, increased in proportion to the speed of rotation.

The variety of MHD shock waves interactions in the solar wind flow

NASA Technical Reports Server (NTRS)

Grib, S. A.

1995-01-01

Different types of nonlinear shock wave interactions in some regions of the solar wind flow are considered. It is shown, that the solar flare or nonflare CME fast shock wave may disappear as the result of the collision with the rotational discontinuity. By the way the appearance of the slow shock waves as the consequence of the collision with other directional discontinuity namely tangential is indicated. Thus the nonlinear oblique and normal MHD shock waves interactions with different solar wind discontinuities (tangential, rotational, contact, shock and plasmoidal) both in the free flow and close to the gradient regions like the terrestrial magnetopause and the heliopause are described. The change of the plasma pressure across the solar wind fast shock waves is also evaluated. The sketch of the classification of the MHD discontinuities interactions, connected with the solar wind evolution is given.

Fluid signatures of rotational discontinuities at Earth's magnetopause

NASA Technical Reports Server (NTRS)

Scudder, J. D.

1983-01-01

Fluid signatures in the MHD approximation at rotational discontinuities (RD) of finite width called rotational shear layers (RSL) are examined for general flow and magnetic geometries. Analytical and geometrical arguments illustrate that the fluid speed can either go up or down across an RSL for a fixed normal mass flux. The speed profile may or may not be monotonic depending on the boundary conditions. The flow velocity may or may not be field aligned or ""jetting'' as a result of traversing the RSL. In general, significant ""convection'' is expected in the layer. The observable signatures of (MHD) RSL's depend on 7 (boundary condition) parameters are (1) the mass density, (2 to 5) the incident normal and transverse components of the magnetic field and fluid velocity, (6) the angle epsilon between the incident tangential flow velocity and tangential magnetic field, and (7) the size of the magnetic angular rotation implemented by the layer delta phi.

Computational analysis of forebody tangential slot blowing on the high alpha research vehicle

NASA Technical Reports Server (NTRS)

Gee, Ken

1994-01-01

Current and future fighter aircraft can maneuver in the high-angle-of-attack flight regime while flying at low subsonic and transonic freestream Mach numbers. However, at any flight speed, the ability of the vertical tails to generate yawing moment is limited in high-angle-of-attack flight. Thus, any system designed to provide the pilot with additional side force and yawing moment must work in both low subsonic and transonic flight. However, previous investigations of the effectiveness of forebody tangential slot blowing in generating the desired control forces and moments have been limited to the low subsonic freestream flow regime. In order to investigate the effectiveness of tangential slot blowing in transonic flight, a computational fluid dynamics analysis was carried out during the grant period. Computational solutions were obtained at three different freestream Mach numbers and at various jet mass flow ratios. All results were obtained using the isolated F/A-18 forebody grid geometry at 30.3 degrees angle of attack. One goal of the research was to determine the effect of freestream Mach number on the effectiveness of forebody tangential slot blowing in generating yawing moment. The second part of the research studied the force onset time lag associated with blowing. The time required for the yawing moment to reach a steady-state value from the onset of blowing may have an impact on the implementation of a pneumatic system on a flight vehicle.

Environmental surveillance of viruses by tangential flow filtration and metagenomic reconstruction.

PubMed

Furtak, Vyacheslav; Roivainen, Merja; Mirochnichenko, Olga; Zagorodnyaya, Tatiana; Laassri, Majid; Zaidi, Sohail Z; Rehman, Lubna; Alam, Muhammad M; Chizhikov, Vladimir; Chumakov, Konstantin

2016-04-14

An approach is proposed for environmental surveillance of poliovirus by concentrating sewage samples with tangential flow filtration (TFF) followed by deep sequencing of viral RNA. Subsequent to testing the method with samples from Finland, samples from Pakistan, a country endemic for poliovirus, were investigated. Genomic sequencing was either performed directly, for unbiased identification of viruses regardless of their ability to grow in cell cultures, or after virus enrichment by cell culture or immunoprecipitation. Bioinformatics enabled separation and determination of individual consensus sequences. Overall, deep sequencing of the entire viral population identified polioviruses, non-polio enteroviruses, and other viruses. In Pakistani sewage samples, adeno-associated virus, unable to replicate autonomously in cell cultures, was the most abundant human virus. The presence of recombinants of wild polioviruses of serotype 1 (WPV1) was also inferred, whereby currently circulating WPV1 of south-Asian (SOAS) lineage comprised two sub-lineages depending on their non-capsid region origin. Complete genome analyses additionally identified point mutants and intertypic recombinants between attenuated Sabin strains in the Pakistani samples, and in one Finnish sample. The approach could allow rapid environmental surveillance of viruses causing human infections. It creates a permanent digital repository of the entire virome potentially useful for retrospective screening of future discovered viruses.

Understanding Vector Fields.

ERIC Educational Resources Information Center

Curjel, C. R.

1990-01-01

Presented are activities that help students understand the idea of a vector field. Included are definitions, flow lines, tangential and normal components along curves, flux and work, field conservation, and differential equations. (KR)

Radial vorticity constraint in core flow modeling

NASA Astrophysics Data System (ADS)

Asari, S.; Lesur, V.

2011-11-01

We present a new method for estimating core surface flows by relaxing the tangentially geostrophic (TG) constraint. Ageostrophic flows are allowed if they are consistent with the radial component of the vorticity equation under assumptions of the magnetostrophic force balance and an insulating mantle. We thus derive a tangentially magnetostrophic (TM) constraint for flows in the spherical harmonic domain and implement it in a least squares inversion of GRIMM-2, a recently proposed core field model, for temporally continuous core flow models (2000.0-2010.0). Comparing the flows calculated using the TG and TM constraints, we show that the number of degrees of freedom for the poloidal flows is notably increased by admitting ageostrophic flows compatible with the TM constraint. We find a significantly improved fit to the GRIMM-2 secular variation (SV) by including zonal poloidal flow in TM flow models. Correlations between the predicted and observed length-of-day variations are equally good under the TG and TM constraints. In addition, we estimate flow models by imposing the TM constraint together with other dynamical constraints: either purely toroidal (PT) flow or helical flow constraint. For the PT case we cannot find any flow which explains the observed SV, while for the helical case the SV can be fitted. The poor compatibility between the TM and PT constraints seems to arise from the absence of zonal poloidal flows. The PT flow assumption is likely to be negated when the radial magnetostrophic vorticity balance is taken into account, even if otherwise consistent with magnetic observations.

Fluid-Structure Interactions as Flow Propagates Tangentially Over a Flexible Plate with Application to Voiced Speech Production

NASA Astrophysics Data System (ADS)

Westervelt, Andrea; Erath, Byron

2013-11-01

Voiced speech is produced by fluid-structure interactions that drive vocal fold motion. Viscous flow features influence the pressure in the gap between the vocal folds (i.e. glottis), thereby altering vocal fold dynamics and the sound that is produced. During the closing phases of the phonatory cycle, vortices form as a result of flow separation as air passes through the divergent glottis. It is hypothesized that the reduced pressure within a vortex core will alter the pressure distribution along the vocal fold surface, thereby aiding in vocal fold closure. The objective of this study is to determine the impact of intraglottal vortices on the fluid-structure interactions of voiced speech by investigating how the dynamics of a flexible plate are influenced by a vortex ring passing tangentially over it. A flexible plate, which models the medial vocal fold surface, is placed in a water-filled tank and positioned parallel to the exit of a vortex generator. The physical parameters of plate stiffness and vortex circulation are scaled with physiological values. As vortices propagate over the plate, particle image velocimetry measurements are captured to analyze the energy exchange between the fluid and flexible plate. The investigations are performed over a range of vortex formation numbers, and lateral displacements of the plate from the centerline of the vortex trajectory. Observations show plate oscillations with displacements directly correlated with the vortex core location.

Magnetic Energy and Helicity in Two Emerging Active Regions in the Sun

NASA Technical Reports Server (NTRS)

Liu, Y.; Schuck, P. W.

2012-01-01

The magnetic energy and relative magnetic helicity in two emerging solar active regions, AR 11072 and AR 11158,are studied. They are computed by integrating over time the energy and relative helicity fluxes across the photosphere. The fluxes consist of two components: one from photospheric tangential flows that shear and braid field lines (shear term), the other from normal flows that advect magnetic flux into the corona (emergence term). For these active regions: (1) relative magnetic helicity in the active-region corona is mainly contributed by the shear term,(2) helicity fluxes from the emergence and the shear terms have the same sign, (3) magnetic energy in the corona (including both potential energy and free energy) is mainly contributed by the emergence term, and(4) energy fluxes from the emergence term and the shear term evolved consistently in phase during the entire flux emergence course.We also examine the apparent tangential velocity derived by tracking field-line footpoints using a simple tracking method. It is found that this velocity is more consistent with tangential plasma velocity than with the flux transport velocity, which agrees with the conclusion by Schuck.

Contact discontinuities in a cold collision-free two-beam plasma

NASA Technical Reports Server (NTRS)

Kirkland, K. B.; Sonnerup, B. U. O.

1982-01-01

The structure of contact discontinuities in a collision-free plasma is examined using a model of a plasma which consists of two oppositely directed cold ion beams and a background of cold massless electrons such that exact charge neutrality is maintained and that the electric field is zero. The basic equations describing self-consistent equilibria are obtained for the more general situation where a net flow across the layer takes place and where the magnetic field has two nonzero tangential components but where the electric field remains zero. These equations are then specialized to the case of no net plasma flow where one of the tangential components is zero, and four different classes of sheets are obtained, all having thickness the order of the ion inertial length. The first class is for layers separating two identical plasma and magnetic field regions, the second is for an infinite array of parallel layers producing an undulated magnetic field, the third is for layers containing trapped ions in closed orbits which separate two vacuum regions with uniform identical magnetic fields, and the fourth is for layers which reflect a single plasma beam, leaving a vacuum with a reversed and compressed tangential field on the other side.

Transition duct with late injection in turbine system

DOEpatents

LeBegue, Jeffrey Scott; Pentecost, Ronnie Ray; Flanagan, James Scott; Kim, Won -Wook; McMahan, Kevin Weston

2015-09-15

A system for supplying an injection fluid to a combustor is disclosed. The system includes a transition duct comprising an inlet, an outlet, and a passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The passage defines a combustion chamber. The system further includes a tube providing fluid communication for the injection fluid to flow through the transition duct and into the combustion chamber.

Weakly sheared active suspensions: hydrodynamics, stability, and rheology.

PubMed

Cui, Zhenlu

2011-03-01

We present a kinetic model for flowing active suspensions and analyze the behavior of a suspension subjected to a weak steady shear. Asymptotic solutions are sought in Deborah number expansions. At the leading order, we explore the steady states and perform their stability analysis. We predict the rheology of active systems including an activity thickening or thinning behavior of the apparent viscosity and a negative apparent viscosity depending on the particle type, flow alignment, and the anchoring conditions, which can be tested on bacterial suspensions. We find remarkable dualities that show that flow-aligning rodlike contractile (extensile) particles are dynamically and rheologically equivalent to flow-aligning discoid extensile (contractile) particles for both tangential and homeotropic anchoring conditions. Another key prediction of this work is the role of the concentration of active suspensions in controlling the rheological behavior: the apparent viscosity may decrease with the increase of the concentration.

Solution of transonic flows by an integro-differential equation method

NASA Technical Reports Server (NTRS)

Ogana, W.

1978-01-01

Solutions of steady transonic flow past a two-dimensional airfoil are obtained from a singular integro-differential equation which involves a tangential derivative of the perturbation velocity potential. Subcritical flows are solved by taking central differences everywhere. For supercritical flows with shocks, central differences are taken in subsonic flow regions and backward differences in supersonic flow regions. The method is applied to a nonlifting parabolic-arc airfoil and to a lifting NACA 0012 airfoil. Results compare favorably with those of finite-difference schemes.

Evaluation of Impinging Stream Vortex Chamber Concepts for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Bullard, Brad; Kopicz, Charles; Michaels, Scott; Turner, James (Technical Monitor)

2001-01-01

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concepts not only offer the system simplicity, but they also would enhance the combustion performance. The test results showed that the chamber performance was markedly high even at a low chamber length-to-diameter ratio (L/D). This incentive can be translated to a convenience in the thrust chamber packaging. Variations of the vortex chamber concepts have been introduced in the past few decades. These investigations include an ongoing work at Orbital Technologies Corporation (ORBITEC). By injecting the oxidizer tangentially at the chamber convergence and fuel axially at the chamber head end, Knuth et al. were able to keep the wall relatively cold. A recent investigation of the low L/D vortex chamber concept for gel propellants was conducted by Michaels. He used both triplet (two oxidizer and one fuel orifices) and unlike impinging schemes to inject propellants tangentially along the chamber wall. Michaels called the subject injection scheme as Impinging Stream Vortex Chamber (ISVC). His preliminary tests showed that high performance, with an Isp efficiency of 92%, can be obtained. MSFC and the U.S. Army are jointly investigating an application of the ISVC concept for the cryogenic oxygen/hydrocarbon propellant system. This vortex chamber concept is currently tested with gel propellants at AMCOM at Redstone Arsenal, Alabama. A version of this concept for the liquid oxygen (LOX)/hydrocarbon fuel (RPM) system has been derived from the one for the gel propellant.

The Analysis of a Vortex Type Magnetohydrodynamic Induction Generator

NASA Technical Reports Server (NTRS)

Lengyel, L. L.

1962-01-01

Consideration it is given to the performance to the characteristics of an AC magnetohydrodynamic power generator, A rotating magnetic field is imposed on the vortex flow of an electrically conducting fluid, which is injected tangentially into an annulus formed by two nonconducting concentric cylinders and two nonconducting end plates. A perturbation technique is used to determine the two dimensional velocity and three dimensional electromagnetic field and current distributions. Finally, the generated power, the ohmic losses, the effective power and the electrical efficiency of the converter system are calculated.

The influence of shrouded stator cavity flows on multistage compressor performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wellborn, S.R.; Okiishi, T.H.

1999-07-01

Experiments were performed on a low-speed multistage axial-flow compressor to assess the effects of shrouded stator cavity flows on aerodynamic performance. Five configurations, which involved systematic changes in seal-tooth leakage rates and/or elimination of the shrouded stator cavities, were tested. Rig data indicate increasing seal-tooth leakage substantially degraded compressor performance. For every 1 percent increase in seal-tooth clearance-to-span ratio, the decrease in pressure rise was 3 percent and the reduction in efficiency was 1 point. These observed performance penalties are comparable to those commonly reported for rotor and cantilevered stator tip clearance variations. The performance degradation observed with increased leakagemore » was brought about in two distinct ways. First, increasing seal-tooth leakage directly spoiled the near-hub performance of the stator row in which leakage occurred. Second, the altered stator exit flow conditions, caused by increased leakage, impaired the performance of the next downstream stage by decreasing the work input of the rotor and increasing total pressure loss of the stator. These trends caused the performance of downstream stages to deteriorate progressively. Numerical simulations of the test rig stator flow field were also conducted to help resolve important fluid mechanic details associated with the interaction between the primary and cavity flows. Simulation results show that fluid originating in the upstream cavity collected on the stator suction surface when the cavity tangential momentum was low and on the pressure side when it was high. The convection of cavity fluid to the suction surface was a mechanism that reduced stator performance when leakage increased.« less

Laser Anemometer Measurements of the Three-Dimensional Rotor Flow Field in the NASA Low-Speed Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Hathaway, Michael D.; Chriss, Randall M.; Strazisar, Anthony J.; Wood, Jerry R.

1995-01-01

A laser anemometer system was used to provide detailed surveys of the three-dimensional velocity field within the NASA low-speed centrifugal impeller operating with a vaneless diffuser. Both laser anemometer and aerodynamic performance data were acquired at the design flow rate and at a lower flow rate. Floor path coordinates, detailed blade geometry, and pneumatic probe survey results are presented in tabular form. The laser anemometer data are presented in the form of pitchwise distributions of axial, radial, and relative tangential velocity on blade-to-blade stream surfaces at 5-percent-of-span increments, starting at 95-percent-of-span from the hub. The laser anemometer data are also presented as contour and wire-frame plots of throughflow velocity and vector plots of secondary velocities at all measurement stations through the impeller.

Modeling Bottom Sediment Erosion Process by Swirling the Flow by Tangential Supply of Oil in the Tank

NASA Astrophysics Data System (ADS)

Nekrasov, V. O.

2016-10-01

The article carries out a statistical data processing of quantitative and territorial division of oil tanks operating in Tyumen region, intended for reception, storage and distribution of commercial oil through trunk pipelines. It describes the working principle of the new device of erosion and prevention of oil bottom sediment formation with tangential supply of oil pumped into reservoir. The most significant similarity criteria can be emphasized in modeling rotational flows exerting significant influence on the structure of the circulating flow of oil in tank when operation of the device described. The dependence of the distribution of the linear velocity of a point on the surface along the radius at the circular motion of the oil in the tank is characterized, and on the basis of this dependence, a formula of general kinetic energy of rotational motion of oil and asphalt-resin-paraffin deposits total volume in the oil reservoir is given.

Parallel momentum input by tangential neutral beam injections in stellarator and heliotron plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishimura, S., E-mail: nishimura.shin@lhd.nifs.ac.jp; Nakamura, Y.; Nishioka, K.

The configuration dependence of parallel momentum inputs to target plasma particle species by tangentially injected neutral beams is investigated in non-axisymmetric stellarator/heliotron model magnetic fields by assuming the existence of magnetic flux-surfaces. In parallel friction integrals of the full Rosenbluth-MacDonald-Judd collision operator in thermal particles' kinetic equations, numerically obtained eigenfunctions are used for excluding trapped fast ions that cannot contribute to the friction integrals. It is found that the momentum inputs to thermal ions strongly depend on magnetic field strength modulations on the flux-surfaces, while the input to electrons is insensitive to the modulation. In future plasma flow studies requiringmore » flow calculations of all particle species in more general non-symmetric toroidal configurations, the eigenfunction method investigated here will be useful.« less

CFD analysis of temperature imbalance in superheater/reheater region of tangentially coal-fired boiler

NASA Astrophysics Data System (ADS)

Zainudin, A. F.; Hasini, H.; Fadhil, S. S. A.

2017-10-01

This paper presents a CFD analysis of the flow, velocity and temperature distribution in a 700 MW tangentially coal-fired boiler operating in Malaysia. The main objective of the analysis is to gain insights on the occurrences in the boiler so as to understand the inherent steam temperature imbalance problem. The results show that the root cause of the problem comes from the residual swirl in the horizontal pass. The deflection of the residual swirl due to the sudden reduction and expansion of the flow cross-sectional area causes velocity deviation between the left and right side of the boiler. This consequently results in flue gas temperature imbalance which has often caused tube leaks in the superheater/reheater region. Therefore, eliminating the residual swirl or restraining it from being diverted might help to alleviate the problem.

Significant consequences of heat generation/absorption and homogeneous-heterogeneous reactions in second grade fluid due to rotating disk

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Qayyum, Sumaira; Alsaedi, Ahmed; Ahmad, Bashir

2018-03-01

Flow of second grade fluid by a rotating disk with heat and mass transfer is discussed. Additional effects of heat generation/absorption are also analyzed. Flow is also subjected to homogeneous-heterogeneous reactions. The convergence of computed solution is assured through appropriate choices of initial guesses and auxiliary parameters. Investigation is made for the effects of involved parameters on velocities (radial, axial, tangential), temperature and concentration. Skin friction and Nusselt number are also analyzed. Graphical results depict that an increase in viscoelastic parameter enhances the axial, radial and tangential velocities. Opposite behavior of temperature is observed for larger values of viscoelastic and heat generation/absorption parameters. Concentration profile is increasing function of Schmidt number, viscoelastic parameter and heterogeneous reaction parameter. Magnitude of skin friction and Nusselt number are enhanced for larger viscoelastic parameter.

Subsychronous vibration of multistage centrifugal compressors forced by rotating stall

NASA Technical Reports Server (NTRS)

Fulton, J. W.

1987-01-01

A multistage centrifugal compressor, in natural gas re-injection service on an offshore petroleum production platform, experienced subsynchronous vibrations which caused excessive bearing wear. Field performance testing correlated the subsynchronous amplitude with the discharge flow coefficient, demonstrating the excitation to be aerodynamic. Adding two impellers allowed an increase in the diffuser flow angle (with respect to tangential) to meet the diffuser stability criteria based on factory and field tests correlated using the theory of Senoo (for rotating stall in a vaneless diffuser). This modification eliminated all significant subsynchronous vibrations in field service, thus confirming the correctness of the solution. Other possible sources of aerodynamically induced vibrations were considered, but the judgment that those are unlikely has been confirmed by subsequent experience with other similar compressors.

Study of Nonlinear MHD Tribological Squeeze Film at Generalized Magnetic Reynolds Numbers Using DTM.

PubMed

Rashidi, Mohammad Mehdi; Freidoonimehr, Navid; Momoniat, Ebrahim; Rostami, Behnam

2015-01-01

In the current article, a combination of the differential transform method (DTM) and Padé approximation method are implemented to solve a system of nonlinear differential equations modelling the flow of a Newtonian magnetic lubricant squeeze film with magnetic induction effects incorporated. Solutions for the transformed radial and tangential momentum as well as solutions for the radial and tangential induced magnetic field conservation equations are determined. The DTM-Padé combined method is observed to demonstrate excellent convergence, stability and versatility in simulating the magnetic squeeze film problem. The effects of involved parameters, i.e. squeeze Reynolds number (N1), dimensionless axial magnetic force strength parameter (N2), dimensionless tangential magnetic force strength parameter (N3), and magnetic Reynolds number (Rem) are illustrated graphically and discussed in detail. Applications of the study include automotive magneto-rheological shock absorbers, novel aircraft landing gear systems and biological prosthetics.

Study of Nonlinear MHD Tribological Squeeze Film at Generalized Magnetic Reynolds Numbers Using DTM

PubMed Central

Rashidi, Mohammad Mehdi; Freidoonimehr, Navid; Momoniat, Ebrahim; Rostami, Behnam

2015-01-01

In the current article, a combination of the differential transform method (DTM) and Padé approximation method are implemented to solve a system of nonlinear differential equations modelling the flow of a Newtonian magnetic lubricant squeeze film with magnetic induction effects incorporated. Solutions for the transformed radial and tangential momentum as well as solutions for the radial and tangential induced magnetic field conservation equations are determined. The DTM-Padé combined method is observed to demonstrate excellent convergence, stability and versatility in simulating the magnetic squeeze film problem. The effects of involved parameters, i.e. squeeze Reynolds number (N 1), dimensionless axial magnetic force strength parameter (N 2), dimensionless tangential magnetic force strength parameter (N 3), and magnetic Reynolds number (Re m) are illustrated graphically and discussed in detail. Applications of the study include automotive magneto-rheological shock absorbers, novel aircraft landing gear systems and biological prosthetics. PMID:26267247

RAXBOD- INVISCID TRANSONIC FLOW OVER AXISYMMETRIC BODIES

NASA Technical Reports Server (NTRS)

Keller, J. D.

1994-01-01

The problem of axisymmetric transonic flow is of interest not only because of the practical application to missile and launch vehicle aerodynamics, but also because of its relation to fully three-dimensional flow in terms of the area rule. The RAXBOD computer program was developed for the analysis of steady, inviscid, irrotational, transonic flow over axisymmetric bodies in free air. RAXBOD uses a finite-difference relaxation method to numerically solve the exact formulation of the disturbance velocity potential with exact surface boundary conditions. Agreement with available experimental results has been good in cases where viscous effects and wind-tunnel wall interference are not important. The governing second-order partial differential equation describing the flow potential is replaced by a system of finite difference equations, including Jameson's "rotated" difference scheme at supersonic points. A stretching is applied to both the normal and tangential coordinates such that the infinite physical space is mapped onto a finite computational space. The boundary condition at infinity can be applied directly and there is no need for an asymptotic far-field solution. The system of finite difference equations is solved by a column relaxation method. In order to obtain both rapid convergence and any desired resolution, the relaxation is performed iteratively on successively refined grids. Input to RAXBOD consists of a description of the body geometry, the free stream conditions, and the desired resolution control parameters. Output from RAXBOD includes computed geometric parameters in the normal and tangential directions, iteration history information, drag coefficients, flow field data in the computational plane, and coordinates of the sonic line. This program is written in FORTRAN IV for batch execution and has been implemented on a CDC 6600 computer with an overlayed central memory requirement of approximately 40K (octal) of 60 bit words. Optional plotted output can be generated for the Calcomp plotting system. The RAXBOD program was developed in 1976.

Magnetic energy flow in the solar wind.

NASA Technical Reports Server (NTRS)

Modisette, J. L.

1972-01-01

Discussion of the effect of rotation (tangential flow) of the solar wind on the conclusions of Whang (1971) suggesting an increase in the solar wind velocity due to the conversion of magnetic energy to kinetic energy. It is shown that the effect of the rotation of the sun on the magnetic energy flow results in most of the magnetic energy being transported by magnetic shear stress near the sun.

Flagellar flows around bacterial swarms

NASA Astrophysics Data System (ADS)

Dauparas, Justas; Lauga, Eric

2016-08-01

Flagellated bacteria on nutrient-rich substrates can differentiate into a swarming state and move in dense swarms across surfaces. A recent experiment measured the flow in the fluid around an Escherichia coli swarm [Wu, Hosu, and Berg, Proc. Natl. Acad. Sci. USA 108, 4147 (2011)], 10.1073/pnas.1016693108. A systematic chiral flow was observed in the clockwise direction (when viewed from above) ahead of the swarm with flow speeds of about 10 μ m /s , about 3 times greater than the radial velocity at the edge of the swarm. The working hypothesis is that this flow is due to the action of cells stalled at the edge of a colony that extend their flagellar filaments outward, moving fluid over the virgin agar. In this work we quantitatively test this hypothesis. We first build an analytical model of the flow induced by a single flagellum in a thin film and then use the model, and its extension to multiple flagella, to compare with experimental measurements. The results we obtain are in agreement with the flagellar hypothesis. The model provides further quantitative insight into the flagella orientations and their spatial distributions as well as the tangential speed profile. In particular, the model suggests that flagella are on average pointing radially out of the swarm and are not wrapped tangentially.

Viscous slip coefficients for binary gas mixtures measured from mass flow rates through a single microtube

NASA Astrophysics Data System (ADS)

Yamaguchi, H.; Takamori, K.; Perrier, P.; Graur, I.; Matsuda, Y.; Niimi, T.

2016-09-01

The viscous slip coefficient for helium-argon binary gas mixture is extracted from the experimental values of the mass flow rate through a microtube. The mass flow rate is measured by the constant-volume method. The viscous slip coefficient was obtained by identifying the measured mass flow rate through a microtube with the corresponding analytical expression, which is a function of the Knudsen number. The measurements were carried out in the slip flow regime where the first-order slip boundary condition can be applied. The measured viscous slip coefficients of binary gas mixtures exhibit a concave function of the molar ratio of the mixture, showing a similar profile with numerical results. However, from the detailed comparison between the measured and numerical values with the complete and incomplete accommodation at a surface, it is inappropriate to estimate the viscous slip coefficient for the mixture numerically by employing separately measured tangential momentum accommodation coefficient for each component. The time variation of the molar ratio in the downstream chamber was measured by sampling the gas from the chamber using the quadrupole mass spectrometer. In our measurements, it is indicated that the volume flow rate of argon is larger than that of helium because of the difference in the tangential momentum accommodation coefficient.

Method for Determining Optimum Injector Inlet Geometry

NASA Technical Reports Server (NTRS)

Myers, W. Neill (Inventor); Trinh, Huu P. (Inventor)

2015-01-01

A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The method calculates the tangential inlet area for each throttleable stage. The method also uses correlation between the tangential inlet areas and delta pressure values to calculate the spring displacement and variable inlet geometry of a liquid rocket engine swirl injector.

Effect of Nozzle Nonlinearities upon Nonlinear Stability of Liquid Propellant Rocket Motors

NASA Technical Reports Server (NTRS)

Padmanabhan, M. S.; Powell, E. A.; Zinn, B. T.

1975-01-01

A three dimensional, nonlinear nozzle admittance relation is developed by solving the wave equation describing finite amplitude oscillatory flow inside the subsonic portion of a choked, slowly convergent axisymmetric nozzle. This nonlinear nozzle admittance relation is then used as a boundary condition in the analysis of nonlinear combustion instability in a cylindrical liquid rocket combustor. In both nozzle and chamber analyses solutions are obtained using the Galerkin method with a series expansion consisting of the first tangential, second tangential, and first radial modes. Using Crocco's time lag model to describe the distributed unsteady combustion process, combustion instability calculations are presented for different values of the following parameters: (1) time lag, (2) interaction index, (3) steady-state Mach number at the nozzle entrance, and (4) chamber length-to-diameter ratio. In each case, limit cycle pressure amplitudes and waveforms are shown for both linear and nonlinear nozzle admittance conditions. These results show that when the amplitudes of the second tangential and first radial modes are considerably smaller than the amplitude of the first tangential mode the inclusion of nozzle nonlinearities has no significant effect on the limiting amplitude and pressure waveforms.

CFD simulation of an unbaffled stirred tank reactor driven by a magnetic rod: assessment of turbulence models.

PubMed

Li, Jiajia; Deng, Baoqing; Zhang, Bing; Shen, Xiuzhong; Kim, Chang Nyung

2015-01-01

A simulation of an unbaffled stirred tank reactor driven by a magnetic stirring rod was carried out in a moving reference frame. The free surface of unbaffled stirred tank was captured by Euler-Euler model coupled with the volume of fluid (VOF) method. The re-normalization group (RNG) k-ɛ model, large eddy simulation (LES) model and detached eddy simulation (DES) model were evaluated for simulating the flow field in the stirred tank. All turbulence models can reproduce the tangential velocity in an unbaffled stirred tank with a rotational speed of 150 rpm, 250 rpm and 400 rpm, respectively. Radial velocity is underpredicted by the three models. LES model and RNG k-ɛ model predict the better tangential velocity and axial velocity, respectively. RNG k-ɛ model is recommended for the simulation of the flow in an unbaffled stirred tank with magnetic rod due to its computational effort.

DYNAMICS AND MAGNETIZATION IN GALAXY CLUSTER CORES TRACED BY X-RAY COLD FRONTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keshet, Uri; Markevitch, Maxim; Birnboim, Yuval

2010-08-10

Cold fronts (CFs)-density and temperature plasma discontinuities-are ubiquitous in cool cores of galaxy clusters, where they appear as X-ray brightness edges in the intracluster medium, nearly concentric with the cluster center. We analyze the thermodynamic profiles deprojected across core CFs found in the literature. While the pressure appears continuous across these CFs, we find that all of them require significant centripetal acceleration beneath the front. This is naturally explained by a tangential, nearly sonic bulk flow just below the CF, and a tangential shear flow involving a fair fraction of the plasma beneath the front. Such shear should generate near-equipartitionmore » magnetic fields on scales {approx}<50pc from the front and could magnetize the entire core. Such fields would explain the apparent stability of cool core CFs and the recently reported CF-radio minihalo association.« less

Flow through very porous screens

NASA Technical Reports Server (NTRS)

Durbin, P. A.; Muramoto, K. K.

1985-01-01

Flow through and around screens with small resistance coefficient were analyzed. Both steady and oscillatory flows are considered, however, the case of a screen normal to the flow is treated. At second order in the asymptotic expansion the steady flow normal to the screen is nonuniform along the screen, due to components induced by the wake and by tangential drag. The third order pressure drop is nonuniform and the wake contains distributed vorticity, in addition to the vortex sheet along its boundary. The unsteady drag coefficient is found as a function of frequency.

Heat-exchanger concepts for neutral-beam calorimeters

NASA Astrophysics Data System (ADS)

Thompson, C. C.; Polk, D. H.; McFarlin, D. J.; Stone, R.

1981-10-01

Advanced cooling concepts that permit the design of water cooled heat exchangers for use as calorimeters and beam dumps for advanced neutral beam injection systems were evaluated. Water cooling techniques ranging from pool boiling to high pressure, high velocity swirl flow were considered. Preliminary performance tests were carried out with copper, inconel and molybdenum tubes ranging in size from 0.19 to 0.50 in. diameter. Coolant flow configurations included: (1) smooth tube/straight flow; (2) smooth tube with swirl flow created by tangential injection of the coolant; and (3) axial flow in internally finned tubes. Additionally, the effect of tube L/D was evaluated. A CO2 laser was employed to irradiate a sector of the tube exterior wall; the laser power was incrementally increased until burnout occurred. Absorbed heat fluxes were calculated by dividing the measured coolant heat load by the area of the burn spot on the tube surface. Two six element thermopiles were used to accurately determine the coolant temperature rise. A maximum burnout heat flux near 14 kW/sq cm was obtained for the molybdenum tube swirl flow configuration.

Cavitation control on a 2D hydrofoil through a continuous tangential injection of liquid: Experimental study

NASA Astrophysics Data System (ADS)

Timoshevskiy, M. V.; Zapryagaev, I. I.; Pervunin, K. S.; Markovich, D. M.

2016-10-01

In the paper, the possibility of active control of a cavitating flow over a 2D hydrofoil that replicates a scaled-down model of high-pressure hydroturbine guide vane (GV) was tested. The flow manipulation was implemented by a continuous tangential liquid injection at different flow rates through a spanwise slot in the foil surface. In experiments, the hydrofoil was placed in the test channel at the attack angle of 9°. Different cavitation conditions were reached by varying the cavitation number and injection velocity. In order to study time dynamics and spatial patterns of partial cavities, high-speed imaging was employed. A PIV method was used to measure the mean and fluctuating velocity fields over the hydrofoil. Hydroacoustic measurements were carried out by means of a pressure transducer to identify spectral characteristics of the cavitating flow. It was found that the present control technique is able to modify the partial cavity pattern (or even totally suppress cavitation) in case of stable sheet cavitation and change the amplitude of pressure pulsations at unsteady regimes. The injection technique makes it also possible to significantly influence the spatial distributions of the mean velocity and its turbulent fluctuations over the GV section for non-cavitating flow and sheet cavitation.

Active Flow Control in an Aggressive Transonic Diffuser

NASA Astrophysics Data System (ADS)

Skinner, Ryan W.; Jansen, Kenneth E.

2017-11-01

A diffuser exchanges upstream kinetic energy for higher downstream static pressure by increasing duct cross-sectional area. The resulting stream-wise and span-wise pressure gradients promote extensive separation in many diffuser configurations. The present computational work evaluates active flow control strategies for separation control in an asymmetric, aggressive diffuser of rectangular cross-section at inlet Mach 0.7 and Re 2.19M. Corner suction is used to suppress secondary flows, and steady/unsteady tangential blowing controls separation on both the single ramped face and the opposite flat face. We explore results from both Spalart-Allmaras RANS and DDES turbulence modeling frameworks; the former is found to miss key physics of the flow control mechanisms. Simulated baseline, steady, and unsteady blowing performance is validated against experimental data. Funding was provided by Northrop Grumman Corporation, and this research used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357.

Comparative investigation of five nanoparticles in flow of viscous fluid with Joule heating and slip due to rotating disk

NASA Astrophysics Data System (ADS)

Qayyum, Sumaira; Khan, Muhammad Ijaz; Hayat, Tasawar; Alsaedi, Ahmed

2018-04-01

Present article addresses the comparative study for flow of five water based nanofluids. Flow in presence of Joule heating is generated by rotating disk with variable thickness. Nanofluids are suspension of Silver (Ag), Copper (Cu), Copper oxide (CuO), Aluminum oxide or Alumina (Al2O3), Titanium oxide or titania (TiO2) and water. Boundary layer approximation is applied to partial differential equations. Using Von Karman transformations the partial differential equations are converted to ordinary differential equations. Convergent series solutions are obtained. Graphical results are presented to examine the behaviors of axial, radial and tangential velocities, temperature, skin friction and Nusselt number. It is observed that radial, axial and tangential velocities decay for slip parameters. Axial velocity decays for larger nanoparticle volume fraction. Effect of nanofluids on velocities dominant than base material. Temperature rises for larger Eckert number and temperature of silver water nanofluid is more because of its higher thermal conductivity. Surface drag force reduces for higher slip parameters. Transfer of heat is more for larger disk thickness index.

Multimodal flow visualization and optimization of pneumatic blood pump for sorbent hemodialysis system.

PubMed

Shu, Fangjun; Parks, Robert; Maholtz, John; Ash, Steven; Antaki, James F

2009-04-01

Renal Solutions Allient Sorbent Hemodialysis System utilizes a two-chambered pneumatic pump (Pulsar Blood Pump, Renal Solutions, Inc., Warrendale, PA, USA) to avoid limitations associated with peristaltic pumping systems. Single-needle access is enabled by counter-pulsing the two pump chambers, thereby obviating compliance chambers or blood reservoirs. Each chamber propels 20 cc per pulse of 3 s (dual access) or 6 s (single access) duration, corresponding to a peak Reynolds number of approximately 8000 (based on inlet velocity and chamber diameter). A multimodal series of flow visualization studies (tracer particle, dye washout, and dye erosion) was conducted on a sequence of pump designs with varying port locations and diaphragms to improve the geometry with respect to risk of thrombogenesis. Experiments were conducted in a simplified flow loop using occluders to simulate flow resistance induced by tubing and dialyzer. Tracer visualization revealed flow patterns and qualitatively indicated turbulence intensity. Dye washout identified dwell volume and areas of flow stagnation for each design. Dye erosion results indicated the effectiveness and homogeneity of surface washing. Compared to a centered inlet which resulted in a fluid jet that produced two counter-rotating vortices, a tangential inlet introduced a single vortex, and kept the flow laminar. It also provided better surface washing on the pump inner surface. However, a tangential outlet did not present as much benefit as expected. On the contrary, it created a sharp defection to the flow when transiting from filling to ejection.

Drying of pulverized material with heated condensible vapor

DOEpatents

Carlson, Larry W.

1986-01-01

Apparatus for drying pulverized material utilizes a high enthalpy condensable vapor such as steam for removing moisture from the individual particles of the pulverized material. The initially wet particulate material is tangentially delivered by a carrier vapor flow to an upper portion of a generally vertical cylindrical separation drum. The lateral wall of the separation drum is provided with a plurality of flow guides for directing the vapor tangentially therein in the direction of particulate material flow. Positioned concentrically within the separation drum and along the longitudinal axis thereof is a water-cooled condensation cylinder which is provided with a plurality of collection plates, or fins, on the outer lateral surface thereof. The cooled collection fins are aligned counter to the flow of the pulverized material and high enthalpy vapor mixture to maximize water vapor condensation thereon. The condensed liquid which includes moisture removed from the pulverized material then flows downward along the outer surface of the coolant cylinder and is collected and removed. The particles travel in a shallow helix due to respective centrifugal and vertical acceleration forces applied thereto. The individual particles of the pulverized material are directed outwardly by the vortex flow where they contact the inner cylindrical surface of the separation drum and are then deposited at the bottom thereof for easy collection and removal. The pulverized material drying apparatus is particularly adapted for drying coal fines and facilitates the recovery of the pulverized coal.

Two stage turbine for rockets

NASA Technical Reports Server (NTRS)

Veres, Joseph P.

1993-01-01

The aerodynamic design and rig test evaluation of a small counter-rotating turbine system is described. The advanced turbine airfoils were designed and tested by Pratt & Whitney. The technology represented by this turbine is being developed for a turbopump to be used in an advanced upper stage rocket engine. The advanced engine will use a hydrogen expander cycle and achieve high performance through efficient combustion of hydrogen/oxygen propellants, high combustion pressure, and high area ratio exhaust nozzle expansion. Engine performance goals require that the turbopump drive turbines achieve high efficiency at low gas flow rates. The low mass flow rates and high operating pressures result in very small airfoil heights and diameters. The high efficiency and small size requirements present a challenging turbine design problem. The shrouded axial turbine blades are 50 percent reaction with a maximum thickness to chord ratio near 1. At 6 deg from the tangential direction, the nozzle and blade exit flow angles are well below the traditional design minimum limits. The blade turning angle of 160 deg also exceeds the maximum limits used in traditional turbine designs.

L.D.V. measurements of unsteady flow fields in radial turbine

NASA Astrophysics Data System (ADS)

Tabakoff, W.; Pasin, M.

1992-07-01

Detailed measurements of an unsteady flow field within the inlet guide vanes (IGV) and the rotor of a radial inflow turbine were performed using a three component Laser Doppler Velocimeter (LDV) system together with a rotary encoder. The mean velocity, the flow angle and the turbulence contours for IGV passages are presented at four blade-to-blade planes for different rotor positions to give three dimensional, unsteady behavior of the IGV flow field. These results are compared with the measurements obtained in the same passage in the absence of the rotor. The flow field of the IGV passage was found to be affected by the presence of the rotor. The ratio of the tangential normal stresses to the radial normal stresses at the exit of the IGV was found to be more than doubled when compared to the case without the rotor. The rotor flow field measurements are presented as relative mean velocity and turbulence stress contours at various cross section planes throughout the rotor. The cross flow and turbulence stress levels were found to be influenced by the incidence angle. Transportation of the high turbulence fluid by the cross flow was observed downstream in the rotor blade passages.

Shrouded inducer pump

DOEpatents

Meng, S.Y.

1989-08-08

An improvement in a pump is described including a shrouded inducer, the improvement comprising first and second sealing means which cooperate with a first vortex cell and a series of secondary vortex cells to remove any tangential velocity components from the recirculation flow. 3 figs.

Shrouded inducer pump

DOEpatents

Meng, Sen Y.

1989-01-01

An improvement in a pump including a shrouded inducer, the improvement comprising first and second sealing means 32,36 which cooperate with a first vortex cell 38 and a series of secondary vortex cells 40 to remove any tangential velocity components from the recirculation flow.

Exit blade geometry and part-load performance of small axial flow propeller turbines: An experimental investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Punit; Nestmann, Franz

2010-09-15

A detailed experimental investigation of the effects of exit blade geometry on the part-load performance of low-head, axial flow propeller turbines is presented. Even as these turbines find important applications in small-scale energy generation using micro-hydro, the relationship between the layout of blade profile, geometry and turbine performance continues to be poorly characterized. The experimental results presented here help understand the relationship between exit tip angle, discharge through the turbine, shaft power, and efficiency. The modification was implemented on two different propeller runners and it was found that the power and efficiency gains from decreasing the exit tip angle couldmore » be explained by a theoretical model presented here based on classical theory of turbomachines. In particular, the focus is on the behaviour of internal parameters like the runner loss coefficient, relative flow angle at exit, mean axial flow velocity and net tangential flow velocity. The study concluded that the effects of exit tip modification were significant. The introspective discussion on the theoretical model's limitation and test facility suggests wider and continued experimentation pertaining to the internal parameters like inlet vortex profile and exit swirl profile. It also recommends thorough validation of the model and its improvement so that it can be made capable for accurate characterization of blade geometric effects. (author)« less

Analytical and numerical performance models of a Heisenberg Vortex Tube

NASA Astrophysics Data System (ADS)

Bunge, C. D.; Cavender, K. A.; Matveev, K. I.; Leachman, J. W.

2017-12-01

Analytical and numerical investigations of a Heisenberg Vortex Tube (HVT) are performed to estimate the cooling potential with cryogenic hydrogen. The Ranque-Hilsch Vortex Tube (RHVT) is a device that tangentially injects a compressed fluid stream into a cylindrical geometry to promote enthalpy streaming and temperature separation between inner and outer flows. The HVT is the result of lining the inside of a RHVT with a hydrogen catalyst. This is the first concept to utilize the endothermic heat of para-orthohydrogen conversion to aid primary cooling. A review of 1st order vortex tube models available in the literature is presented and adapted to accommodate cryogenic hydrogen properties. These first order model predictions are compared with 2-D axisymmetric Computational Fluid Dynamics (CFD) simulations.

Purged window apparatus. [On-line spectroscopic analysis of gas flow systems

DOEpatents

Ballard, E.O.

1982-04-05

A purged window apparatus is described which utilizes tangentially injected heated purge gases in the vicinity of electromagnetic radiation transmitting windows and a tapered external mounting tube to accelerate these gases to provide a vortex flow on the window surface and a turbulent flow throughout the mounting tube thereby preventing backstreaming of flowing gases under investigation in a chamber to which a plurality of similar purged apparatus is attached with the consequent result that spectroscopic analyses can be undertaken for lengthy periods without the necessity of interrupting the flow for cleaning or replacing the windows due to contamination.

A statistical study of magnetopause structures: Tangential versus rotational discontinuities

NASA Astrophysics Data System (ADS)

Chou, Y.-C.; Hau, L.-N.

2012-08-01

A statistical study of the structure of Earth's magnetopause is carried out by analyzing two-year AMPTE/IRM plasma and magnetic field data. The analyses are based on the minimum variance analysis (MVA), the deHoffmann-Teller (HT) frame analysis and the Walén relation. A total of 328 magnetopause crossings are identified and error estimates associated with MVA and HT frame analyses are performed for each case. In 142 out of 328 events both MVA and HT frame analyses yield high quality results which are classified as either tangential-discontinuity (TD) or rotational-discontinuity (RD) structures based only on the Walén relation: Events withSWA ≤ 0.4 (SWA ≥ 0.5) are classified as TD (RD), and rest (with 0.4 < SWA < 0.5) is classified as "uncertain," where SWA refers to the Walén slope. With this criterion, 84% of 142 events are TDs, 12% are RDs, and 4% are uncertain events. There are a large portion of TD events which exhibit a finite normal magnetic field component Bnbut have insignificant flow as compared to the Alfvén velocity in the HT frame. Two-dimensional Grad-Shafranov reconstruction of forty selected TD and RD events show that single or multiple X-line accompanied with magnetic islands are common feature of magnetopause current. A survey plot of the HT velocity associated with TD structures projected onto the magnetopause shows that the flow is diverted at the subsolar point and accelerated toward the dawn and dusk flanks.

Manipulation of near-wall turbulence by surface slip and permeability

NASA Astrophysics Data System (ADS)

Gómez-de-Segura, G.; Fairhall, C. T.; MacDonald, M.; Chung, D.; García-Mayoral, R.

2018-04-01

We study the effect on near-wall turbulence of tangential slip and wall-normal transpiration, typically produced by textured surfaces and other surface manipulations. For this, we conduct direct numerical simulations (DNSs) with different virtual origins for the different velocity components. The different origins result in a relative wall-normal displacement of the near-wall, quasi-streamwise vortices with respect to the mean flow, which in turn produces a change in drag. The objective of this work is to extend the existing understanding on how these virtual origins affect the flow. In the literature, the virtual origins for the tangential velocities are typically characterised by slip boundary conditions, while the wall-normal velocity is assumed to be zero at the boundary plane. Here we explore different techniques to define and implement the three virtual origins, with special emphasis on the wall-normal one. We investigate impedance conditions relating the wall-normal velocity to the pressure, and linear relations between the velocity components and their wall-normal gradients, as is typically done to impose slip conditions. These models are first tested to represent a smooth wall below the boundary plane, with all virtual origins equal, and later for different tangential and wall-normal origins. Our results confirm that the change in drag is determined by the offset between the origins perceived by mean flow and the quasi-streamwise vortices or, more generally, the near-wall turbulent cycle. The origin for the latter, however, is not set by the spanwise virtual origin alone, as previously proposed, but by a combination of the spanwise and wall-normal origins, and mainly determined by the shallowest of the two. These observations allow us to extend the existing expression to predict the change in drag, accounting for the wall-normal effect when the transpiration is not negligible.

Wind Tunnel Results of Pneumatic Forebody Vortex Control Using Rectangular Slots a Chined Forebody

NASA Technical Reports Server (NTRS)

Alexander, Michael; Meyn, Larry A.

1994-01-01

A subsonic wind tunnel investigation of pneumatic vortex flow control on a chined forebody using slots was accomplished at a dynamic pressure of 50 psf resulting in a R(n)/ft of 1.3 x 10(exp 6). Data were acquired from angles of attack ranging from -4deg to +34deg at side slips of +0.4deg and +10.4deg. The test article used in this study was the 10% scale Fighter Lift and Control (FLAC) advanced diamond winged, vee-tailed fighter configuration. Three different slot blowing concepts were evaluated; outward, downward, and tangential with ail blowing accomplished asymmetrically. The results of three different mass flows (0.067, 0.13, and 0.26 lbm/s; C(sub mu)'s of less than or equal to 0.006, 0.011. and 0.022 respectively) were analyzed and reported. Test data are presented on the effects of mass flows, slot lengths and positions and blowing concepts on yawing moment and side force generation. Results from this study indicate that the outward and downward blowing slots developed yawing moment and side force increments in the direction opposite of the blowing side while the tangential blowing slots generated yawing moment and side force increments in the direction towards the blowing side. The outward and downward blowing slots typically produced positive pitching moment increments while the tangential blowing slots typically generated negative pitching moment increments. The slot blowing nearest the forebody apex was most effective at generating the largest increments and as the slot was moved aft or increased in length, its effectiveness at generating forces and moments diminished.

Boundary Layer Studies on a Spinning Tangent-Ogive-Cylinder Model

DTIC Science & Technology

1975-07-01

ca) An experimental investigation of the Magnus effect on a seven caliber tangent-I ;’ ogive- cylinder model in supersonic flow is reported. The...necessary and Identify by block number) Three-Dimiensional Boundary Layer Compressible Flow Body of Revolution Magnus Effects Boundary Layer...factors have resulted in renewed interest in the study of the Magnus effect . This report describes an experimental study of the effects of spin on

Downstream influence of swept slot injection in hypersonic turbulent flow

NASA Technical Reports Server (NTRS)

Hefner, J. N.; Cary, A. M., Jr.; Bushnell, D. B.

1977-01-01

Results of an experimental and numerical investigation of tangential swept slot injection into a thick turbulent boundary layer at Mach 6 are presented. Film cooling effectiveness, skin friction, and flow structure downstream of the swept slot injection were investigated. The data were compared with that for unswept slots, and it was found that cooling effectiveness and skin friction reductions are not significantly affected by sweeping the slot.

Vibrotactile Compliance Feedback for Tangential Force Interaction.

PubMed

Heo, Seongkook; Lee, Geehyuk

2017-01-01

This paper presents a method to generate a haptic illusion of compliance using a vibrotactile actuator when a tangential force is applied to a rigid surface. The novel method builds on a conceptual compliance model where a physical object moves on a textured surface in response to a tangential force. The method plays vibration patterns simulating friction-induced vibrations as an applied tangential force changes. We built a prototype consisting of a two-dimensional tangential force sensor and a surface transducer to test the effectiveness of the model. Participants in user experiments with the prototype perceived the rigid surface of the prototype as a moving, rubber-like plate. The main findings of the experiments are: 1) the perceived stiffness of a simulated material can be controlled by controlling the force-playback transfer function, 2) its perceptual properties such as softness and pleasantness can be controlled by changing friction grain parameters, and 3) the use of the vibrotactile compliance feedback reduces participants' workload including physical demand and frustration while performing a force repetition task.

Contributions of the secondary jet to the maximum tangential velocity and to the collection efficiency of the fixed guide vane type axial flow cyclone dust collector

NASA Astrophysics Data System (ADS)

Ogawa, Akira; Anzou, Hideki; Yamamoto, So; Shimagaki, Mituru

2015-11-01

In order to control the maximum tangential velocity Vθm(m/s) of the turbulent rotational air flow and the collection efficiency ηc (%) using the fly ash of the mean diameter XR50=5.57 µm, two secondary jet nozzles were installed to the body of the axial flow cyclone dust collector with the body diameter D1=99mm. Then in order to estimate Vθm (m/s), the conservation theory of the angular momentum flux with Ogawa combined vortex model was applied. The comparisons of the estimated results of Vθm(m/s) with the measured results by the cylindrical Pitot-tube were shown in good agreement. And also the estimated collection efficiencies ηcth (%) basing upon the cut-size Xc (µm) which was calculated by using the estimated Vθ m(m/s) and also the particle size distribution R(Xp) were shown a little higher values than the experimental results due to the re-entrainment of the collected dust. The best method for adjustment of ηc (%) related to the contribution of the secondary jet flow is principally to apply the centrifugal effect Φc (1). Above stated results are described in detail.

Axial-Flow Turbine Rotor Discharge-Flow Overexpansion and Limit-Loading Condition, Part I: Computational Fluid Dynamics (CFD) Investigation

NASA Technical Reports Server (NTRS)

Chen, Shu-Cheng S.

2017-01-01

A Computational Fluid Dynamic (CFD) investigation is conducted over a two-dimensional axial-flow turbine rotor blade row to study the phenomena of turbine rotor discharge flow overexpansion at subcritical, critical, and supercritical conditions. Quantitative data of the mean-flow Mach numbers, mean-flow angles, the tangential blade pressure forces, the mean-flow mass flux, and the flow-path total pressure loss coefficients, averaged or integrated across the two-dimensional computational domain encompassing two blade-passages, are obtained over a series of 14 inlet-total to exit-static pressure ratios, from 1.5 (un-choked; subcritical condition) to 10.0 (supercritical with excessively high pressure ratio.) Detailed flow features over the full domain-of-computation, such as the streamline patterns, Mach contours, pressure contours, blade surface pressure distributions, etc. are collected and displayed in this paper. A formal, quantitative definition of the limit loading condition based on the channel flow theory is proposed and explained. Contrary to the comments made in the historical works performed on this subject, about the deficiency of the theoretical methods applied in analyzing this phenomena, using modern CFD method for the study of this subject appears to be quite adequate and successful. This paper describes the CFD work and its findings.

Coandă configured aircraft: A preliminary analytical assessment

NASA Astrophysics Data System (ADS)

Hamid, M. F. Abdul; Gires, E.; Harithuddin, A. S. M.; Abu Talib, A. R.; Rafie, A. S. M.; Romli, F. I.; Harmin, M. Y.

2017-12-01

The interest in the use of flow control for enhanced aerodynamic performance has grown, particularly in the use of jets (continuous, synthetic, pulsed, etc.), compliant surface, vortex-cell, and others. It has been widely documented that these active control concepts can dramatically alter the behaviour of aerodynamic components like airfoils, wings and bodies. In this conjunction, with the present demands of low-cost and efficient flights, the use of Coandă effect as a lift enhancer has attracted a lot of interest. Tangential jets that take advantage of the Coandă effect to closely follow the contours of the body have been considered to be simple and particularly effective. For this case, a large mass of surrounding air can be entrained, hence amplifying the circulation. In an effort to optimize the aerodynamic performance of an aircraft, such effect will be critically reviewed by taking advantage of recent progress. For this purpose, in this study, the design of a Coandă-configured aircraft wing will be mathematically idealized and modelled as a two-dimensional flow problem.

Firing of pulverized solvent refined coal

DOEpatents

Lennon, Dennis R.; Snedden, Richard B.; Foster, Edward P.; Bellas, George T.

1990-05-15

A burner for the firing of pulverized solvent refined coal is constructed and operated such that the solvent refined coal can be fired successfully without any performance limitations and without the coking of the solvent refined coal on the burner components. The burner is provided with a tangential inlet of primary air and pulverized fuel, a vaned diffusion swirler for the mixture of primary air and fuel, a center water-cooled conical diffuser shielding the incoming fuel from the heat radiation from the flame and deflecting the primary air and fuel steam into the secondary air, and a watercooled annulus located between the primary air and secondary air flows.

Scripps Ocean Modeling and Remote Sensing (SOMARS)

DTIC Science & Technology

1990-04-10

1990: Satellite derived estimates of the normal and tangential components of near-surface flow. Internat. J. Rem. Sens., submitted. Mr. Timothy ... Gallaudet - M.S,. in Oceanography/Applied Ocean Sciences (Naval student; not a terminal M.S. degree) Thesis Advisor: Topic will relate to AVIIRR analyses of

Determination of wind tunnel constraint effects by a unified pressure signature method. Part 1: Applications to winged configurations

NASA Technical Reports Server (NTRS)

Hackett, J. E.; Sampath, S.; Phillips, C. G.

1981-01-01

A new, fast, non-iterative version of the "Wall Pressure Signature Method" is described and used to determine blockage and angle-of-attack wind tunnel corrections for highly-powered jet-flap models. The correction method is complemented by the application of tangential blowing at the tunnel floor to suppress flow breakdown there, using feedback from measured floor pressures. This tangential blowing technique was substantiated by subsequent flow investigations using an LV. The basic tests on an unswept, knee-blown, jet flapped wing were supplemented to include the effects of slat-removal, sweep and the addition of unflapped tips. C sub mu values were varied from 0 to 10 free-air C sub l's in excess of 18 were measured in some cases. Application of the new methods yielded corrected data which agreed with corresponding large tunnel "free air" resuls to within the limits of experimental accuracy in almost all cases. A program listing is provided, with sample cases.

Concentration of infectious hematopoietic necrosis virus from water samples by tangential flow filtration and polyethylene glycol precipitation

USGS Publications Warehouse

Batts, W.N.; Winton, J.R.

1989-01-01

Infectious hematopoietic necrosis virus (IHNV) was concentrated from water samples by polyethylene glycol (PEG) precipitation, tangential flow filtration (TFF), and by a combination of TFF followed by PEG precipitation of the retentate. Used alone, PEG increased virus titers more than 200-fold, and the efficiency of recovery was as great as 100%. Used alone, TFF concentrated IHNV more than 20-fold, and average recovery was 70%. When the two techniques were combined, 10-L water samples were reduced to about 300 mL by TFF and the virus was precipitated with PEG into a 1 to 2 g pellet; total recovery was as great as 100%. The combined techniques were used to isolate IHNV from water samples taken from a river containing adult sockeye salmon (Oncorhynchus nerka) and from a hatchery pond containing adult spring chinook salmon (O. tshawytscha). The combination of these methods was effective in concentrating and detecting IHNV from water containing only three infectious particles per 10-L sample.

Evaluation of surface deformability of lipid nanocapsules by drop tensiometer technique, and its experimental assessment by dialysis and tangential flow filtration.

PubMed

Hirsjärvi, Samuli; Bastiat, Guillaume; Saulnier, Patrick; Benoît, Jean-Pierre

2012-09-15

Deformability of nanoparticles might affect their behaviour at biological interfaces. Lipid nanocapsules (LNCs) are semi-solid particles resembling a hybrid of polymer nanoparticles and liposomes. Deformability of LNCs of different sizes was modelled by drop tensiometer technique. Two purification methods, dialysis and tangential flow filtration (TFF), were applied to study experimental behaviour and deformability of LNCs in order to evaluate if these properties contributed to membrane passing. Rheological parameters obtained from the drop tensiometer analysis suggested decreasing surface deformability of LNCs with increase in diameter. Dialysis results showed that up to 10% of LNCs can be lost during the process (e.g. membrane accumulation) but no clear evidence of the membrane passing was observed. Instead, LNCs with initial size and size distribution could be found in the TFF filtrate although molecular weight cut-off (MWCO) of the membrane used was smaller than the LNC diameter. Copyright © 2012 Elsevier B.V. All rights reserved.

Accounting for magnetic diffusion in core flow inversions from geomagnetic secular variation

NASA Astrophysics Data System (ADS)

Amit, Hagay; Christensen, Ulrich R.

2008-12-01

We use numerical dynamos to investigate the possible role of magnetic diffusion at the top of the core. We find that the contribution of radial magnetic diffusion to the secular variation is correlated with that of tangential magnetic diffusion for a wide range of control parameters. The correlation between the two diffusive terms is interpreted in terms of the variation in the strength of poloidal flow along a columnar flow tube. The amplitude ratio of the two diffusive terms is used to estimate the probable contribution of radial magnetic diffusion to the secular variation at Earth-like conditions. We then apply a model where radial magnetic diffusion is proportional to tangential diffusion to core flow inversions of geomagnetic secular variation data. We find that including magnetic diffusion does not change dramatically the global flow but some significant local variations appear. In the non frozen-flux core flow models (termed `diffusive'), the hemispherical dichotomy between the active Atlantic and quiet Pacific is weaker, a cyclonic vortex below North America emerges and the vortex below Asia is stronger. Our results have several important geophysical implications. First, our diffusive flow models contain some flow activity at low latitudes in the Pacific, suggesting a local balance between magnetic field advection and diffusion in that region. Second, the cyclone below North America in our diffusive flows reconciles the difference between mantle-driven thermal wind predictions and frozen-flux core flow models, and is consistent with the prominent intense magnetic flux patch below North America in geomagnetic field models. Finally, we hypothesize that magnetic diffusion near the core surface plays a larger role in the geomagnetic secular variation than usually assumed.

Drying of pulverized material with heated condensible vapor

DOEpatents

Carlson, L.W.

1984-08-16

Apparatus for drying pulverized material utilizes a high enthalpy condensable vapor such as steam for removing moisture from the individual particles of the pulverized material. The initially wet particulate material is tangentially delivered by a carrier vapor flow to an upper portion of a generally vertical cylindrical separation drum. The lateral wall of the separation drum is provided with a plurality of flow guides for directing the vapor tangentially therein in the direction of particulate material flow. Positioned concentrically within the separation drum and along the longitudinal axis thereof is a water-cooled condensation cylinder which is provided with a plurality of collection plates, or fines, on the outer lateral surface thereof. The cooled collection fines are aligned counter to the flow of the pulverized material and high enthalpy vapor mixture to maximize water vapor condensation thereon. The condensed liquid which includes moisture removed from the pulverized materials then flows downward along the outer surface of the coolant cylinder and is collected and removed. The particles travel in a shallow helix due to respective centrifugal and vertical acceleration forces applied thereto. The individual particles of the pulverized material are directed outwardly by the vortex flow where they contact the inner cylindrical surface of the separation drum and are then deposited at the bottom thereof for easy collection and removal. The pulverized material drying apparatus is particularly adapted for drying coal fines and facilitates the recovery of the pulverized coal. 2 figs.

Swirl ratio effects on tornado-like vortices

NASA Astrophysics Data System (ADS)

Hashemi-Tari, Pooyan; Gurka, Roi; Hangen, Horia

2007-11-01

The effect of swirl ratio on the flow field for a tornado-like vortex simulator (TVS) is investigated. Different swirl ratios are obtained by changing the geometry and tangential velocity which determine the vortex evolution. Flow visualizations, surface pressure and Particle Image Velocimetry (PIV) measurements are performed in a small TVS for swirl ratios S between 0 and 1. The PIV data was acquired for two orthogonal planes: normal and parallel to the solid boundary at several height locations. The ratio between the angular momentum and the radial momentum which characterize the swirl ratio is investigated. Statistical analysis to the turbulent field is performed by mean and rms profiles of the velocity, stresses and vorticity are presented. A Proper Orthogonal Decomposition (POD) is performed on the vorticity field. The results are used to: (i) provide a relation between these 3 sets of qualitative and quantitative measurements and the swirl ratio in an attempt to relate the fluid dynamics parameters to the forensic, Fujita scale, and (ii) understand the spatio-temporal distribution of the most energetic POD modes in a tornado-like vortex.

Performance of a low-power subsonic-arc-attachment arcjet thruster

NASA Technical Reports Server (NTRS)

Sankovic, John M.; Berns, Darren H.

1993-01-01

A subsonic-arc-attachment thruster design was scaled from a 30 kW 1960's vintage thruster to operate at nominally 3 kW. Performance measurements were obtained over a 1-4 kW power range using hydrogen as the propellant. Several modes of operation were identified and were characterized by varying degrees of voltage instability. A stability map was developed showing that the voltage oscillations were brought upon by elevated current or propellant levels. At a given specific energy level the specific impulse increased asymptotically with increased flow rates. Comparisons of performance were made between radial and tangential propellant injection. When the vortex flow was eliminated using radial injection, the operating voltages were lower at a given current, and the specific impulse and efficiency decreased. Tests were also conducted to determine the effects of background pressure on operation, and performance data were obtained at pressures of 0.047 Pa and 18 Pa. For a given specific energy level, the performance increased with a decrease in facility background pressure. Lowering the background pressure also caused a dramatic change in the voltage-current characteristic and the voltage stability, a phenomenon not previously reported with conventional supersonic-arc-attachment thrusters.

Low NOx combustion and SCR flow field optimization in a low volatile coal fired boiler.

PubMed

Liu, Xing; Tan, Houzhang; Wang, Yibin; Yang, Fuxin; Mikulčić, Hrvoje; Vujanović, Milan; Duić, Neven

2018-08-15

Low NO x burner redesign and deep air staging have been carried out to optimize the poor ignition and reduce the NO x emissions in a low volatile coal fired 330 MW e boiler. Residual swirling flow in the tangentially-fired furnace caused flue gas velocity deviations at furnace exit, leading to flow field unevenness in the SCR (selective catalytic reduction) system and poor denitrification efficiency. Numerical simulations on the velocity field in the SCR system were carried out to determine the optimal flow deflector arrangement to improve flow field uniformity of SCR system. Full-scale experiment was performed to investigate the effect of low NO x combustion and SCR flow field optimization. Compared with the results before the optimization, the NO x emissions at furnace exit decreased from 550 to 650 mg/Nm³ to 330-430 mg/Nm³. The sample standard deviation of the NO x emissions at the outlet section of SCR decreased from 34.8 mg/Nm³ to 7.8 mg/Nm³. The consumption of liquid ammonia reduced from 150 to 200 kg/h to 100-150 kg/h after optimization. Copyright © 2018. Published by Elsevier Ltd.

Method of analysis for compressible flow through mixed-flow centrifugal impellers of arbitrary design

NASA Technical Reports Server (NTRS)

Hamrick, Joseph T; Ginsburg, Ambrose; Osborn, Walter M

1952-01-01

A method is presented for analysis of the compressible flow between the hub and the shroud of mixed-flow impellers of arbitrary design. Axial symmetry was assumed, but the forces in the meridional (hub to shroud) plane, which are derived from tangential pressure gradients, were taken into account. The method was applied to an experimental mixed-flow impeller. The analysis of the flow in the meridional plane of the impeller showed that the rotational forces, the blade curvature, and the hub-shroud profile can introduce severe velocity gradients along the hub and the shroud surfaces. Choked flow at the impeller inlet as determined by the analysis was verified by experimental results.

Time-dependent flow model of a generalized Burgers' fluid with fractional derivatives through a cylindrical domain: An exact and numerical approach

NASA Astrophysics Data System (ADS)

Safdar, Rabia; Imran, M.; Khalique, Chaudry Masood

2018-06-01

Exact solutions for velocity field and tangential stress for rotational flow of a generalized Burgers' fluid within an infinite circular pipe are derived by using the methods of Laplace and finite Hankel transformations. Firstly we take the position of fluid at rest and then the fluid flow due to the rotation of the pipe around the axis of flow having time dependant angular velocity. The exact solutions are presented in terms of the generalized Ga,b,c (., t) -functions. The corresponding results can be freely specified for the same results of Burgers', Oldroyd B, Maxwell, second grade and Newtonian fluids (performing the same motion) as particular cases of the results obtained earlier. The impact of the different parameters, individually and in comparison, are represented by graphical demonstrations. Secondly the numerical solutions for velocity and stress are also obtained with the help of Laplace transformation, Gaver Stehfest's algorithm and MATHCAD. Finally a comparison of both methods for the same problem is done and shows the consistency of results.

Numerical performance analysis of acoustic Doppler velocity profilers in the wake of an axial-flow marine hydrokinetic turbine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richmond, Marshall C.; Harding, Samuel F.; Romero Gomez, Pedro DJ

The use of acoustic Doppler current profilers (ADCPs) for the characterization of flow conditions in the vicinity of both experimental and full scale marine hydrokinetic (MHK) turbines is becoming increasingly prevalent. The computation of a three dimensional velocity measurement from divergent acoustic beams requires the assumption that the flow conditions are homogeneous between all beams at a particular axial distance from the instrument. In the near wake of MHK devices, the mean fluid motion is observed to be highly spatially dependent as a result of torque generation and energy extraction. This paper examines the performance of ADCP measurements in suchmore » scenarios through the modelling of a virtual ADCP (VADCP) instrument in the velocity field in the wake of an MHK turbine resolved using unsteady computational fluid dynamics (CFD). This is achieved by sampling the CFD velocity field at equivalent locations to the sample bins of an ADCP and performing the coordinate transformation from beam coordinates to instrument coordinates and finally to global coordinates. The error in the mean velocity calculated by the VADCP relative to the reference velocity along the instrument axis is calculated for a range of instrument locations and orientations. The stream-wise velocity deficit and tangential swirl velocity caused by the rotor rotation lead to significant misrepresentation of the true flow velocity profiles by the VADCP, with the most significant errors in the transverse (cross-flow) velocity direction.« less

Impact of viscosity variation and micro rotation on oblique transport of Cu-water fluid.

PubMed

Tabassum, Rabil; Mehmood, R; Nadeem, S

2017-09-01

This study inspects the influence of temperature dependent viscosity on Oblique flow of micropolar nanofluid. Fluid viscosity is considered as an exponential function of temperature. Governing equations are converted into dimensionless forms with aid of suitable transformations. Outcomes of the study are shown in graphical form and discussed in detail. Results revealed that viscosity parameter has pronounced effects on velocity profiles, temperature distribution, micro-rotation, streamlines, shear stress and heat flux. It is found that viscosity parameter enhances the temperature distribution, tangential velocity profile, normal component of micro-rotation and shear stress at the wall while it has decreasing effect on tangential component of micro-rotation and local heat flux. Copyright © 2017 Elsevier Inc. All rights reserved.

The Influence of Swirl Brakes and a Tip Discharge Orifice on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps

NASA Technical Reports Server (NTRS)

Sivo, Joseph M.; Acosta, A. J.; Brennen, C. E.; Caughey, T. K.

1993-01-01

Recent experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have examined the effects of a tip leakage restriction and swirl brakes on the rotordynamic forces due to leakage flows on an impeller undergoing a prescribed circular whirl. The experiments simulate the leakage flow conditions and geometry of the Alternate Turbopump Design (ATD) of the Space Shuttle High Pressure Oxygen Turbopump and are critical to evaluating the pump's rotordynamic instability problems. Previous experimental and analytical results have shown that discharge-to-suction leakage flows in the annulus of a shrouded centrifugal pump contribute substantially to the fluid induced rotordynamic forces. Also, previous experiments have shown that leakage inlet (pump discharge) swirl can increase the cross-coupled stiffness coefficient and hence increase the range of positive whirl for which the tangential force is destabilizing. In recent experimental work, the present authors demonstrated that when the swirl velocity within the leakage path is reduced by the introduction of ribs or swirl brakes, then a substantial decrease in both the destabilizing normal and tangential forces could be achieved. Motivation for the present research is that previous experiments have shown that restrictions such as wear rings or orifices at pump inlets affect the leakage forces. Recent pump designs such as the Space Shuttle Alternate Turbopump Design (ATD) utilize tip orifices at discharge for the purpose of establishing axial thrust balance. The ATD has experienced rotordynamic instability problems and one may surmise that these tip discharge orifices may also have an important effect on the normal and tangential forces in the plane of impeller rotation. The present study determines if such tip leakage restrictions contribute to undesirable rotordynamic forces. Additional motivation for the present study is that the widening of the leakage path annular clearance and the installation of swirl brakes in the ATD has been proposed to solve its instability problems. The present study assesses the effect of such a design modification on the rotordynamic forces. The experimental apparatus consists of a solid or dummy impeller, a housing instrumented for pressure measurements, a rotating dynamometer and an eccentric whirl mechanism. The solid impeller is used so that leakage flow contributions to the forces are measured, but the main throughflow contributions are not experienced. The inner surface of the housing has been modified to accommodate meridional ribs or swirl brakes within the leakage annulus. In addition, the housing has been modified to accommodate a discharge orifice that qualitatively simulates one side of the balance piston orifice of the Space Shuttle ATD. Results indicate the detrimental effects of a discharge orifice and the beneficial effects of brakes. Plots of the tangential and normal forces versus whirl ratio show a substantial increase in these forces along with destabilizing resonances at some positive whirl ratios when a discharge orifice is added. When brakes are added, some of the detrimental effects of the orifice are reduced. For the tangential force, a plot versus whirl ratio shows a significant reduction and a destabilizing resonance appears to be eliminated. For the normal force, although the overall force is not reduced, again a destabilizing resonance appears to be eliminated.

Vertical mass transfer in open channel flow

USGS Publications Warehouse

Jobson, Harvey E.

1968-01-01

The vertical mass transfer coefficient and particle fall velocity were determined in an open channel shear flow. Three dispersants, dye, fine sand and medium sand, were used with each of three flow conditions. The dispersant was injected as a continuous line source across the channel and downstream concentration profiles were measured. From these profiles along with the measured velocity distribution both the vertical mass transfer coefficient and the local particle fall velocity were determined.The effects of secondary currents on the vertical mixing process were discussed. Data was taken and analyzed in such a way as to largely eliminate the effects of these currents on the measured values. A procedure was developed by which the local value of the fall velocity of sand sized particles could be determined in an open channel flow. The fall velocity of the particles in the turbulent flow was always greater than their fall velocity in quiescent water. Reynolds analogy between the transfer of momentum and marked fluid particles was further substantiated. The turbulent Schmidt number was shown to be approximately 1.03 for an open channel flow with a rough boundary. Eulerian turbulence measurements were not sufficient to predict the vertical transfer coefficient. Vertical mixing of sediment is due to three semi-independent processes. These processes are: secondary currents, diffusion due to tangential velocity fluctuations and diffusion due to the curvature of the fluid particle path lines. The diffusion coefficient due to tangential velocity fluctuations is approximately proportional to the transfer coefficient of marked fluid particles. The proportionality constant is less than or equal to 1.0 and decreases with increasing particle size. The diffusion coefficient due to the curvature of the fluid particle path lines is not related to the diffusion coefficient for marked fluid particles and increases with particle size, at least for sediment particles in the sand size range. The total sediment transfer coefficient is equal to the sum of the coefficient due to tangential velocity fluctuations and the coefficient due to the curvature of the fluid particle path lines. A numerical solution to the conservation of mass equation is given. The effects of the transfer coefficient, fall velocity and bed conditions on the predicted concentration profiles are illustrated.

Effects of inlet flow field conditions on the performance of centrifugal compressor diffusers: Part 1 -- Discrete-passage diffuser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filipenco, V.G.; Deniz, S.; Johnston, J.M.

2000-01-01

This is Part 1 of a two-part paper considering the performance of radial diffusers for use in a high-performance centrifugal compressor. Part 1 reports on discrete-passage diffusers, while Part 2 describes a test of a straight-channel diffuser designed for equivalent duty. Two builds of discrete-passage diffuser were tested, with 30 and 38 separate passages. Both the 30 and 38 passage diffusers investigated showed comparable range of unstalled operation and similar level of overall diffuser pressure recovery. The paper concentrates on the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages.more » The flow conditions examined include diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity. The investigation was carried out in a specially built test facility, designed to provide a controlled inlet flow field to the test diffusers. The facility can provide a wide range of diffuser inlet velocity profile distortion and skew with Mach numbers up to unity and flow angles of 63 to 75 deg from the radical direction. The consequences of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed. The overall diffuser pressure recovery coefficient, based on suitably averaged inlet total pressure, was found to correlate well with the momentum-averaged flow angle into the diffuser. It is shown that the generally accepted sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary layer blockage can be largely attributed to inappropriate quantification of the average dynamic pressure at diffuser inlet. Use of an inlet dynamic pressure based on availability or mass-averaging in combination with definition of inlet flow angle based on mass average of the radial and tangential velocity at diffuser inlet removes this sensitivity.« less

Enhanced capabilities and modified users manual for axial-flow compressor conceptual design code CSPAN

NASA Technical Reports Server (NTRS)

Glassman, Arthur J.; Lavelle, Thomas M.

1995-01-01

Modifications made to the axial-flow compressor conceptual design code CSPAN are documented in this report. Endwall blockage and stall margin predictions were added. The loss-coefficient model was upgraded. Default correlations for rotor and stator solidity and aspect-ratio inputs and for stator-exit tangential velocity inputs were included in the code along with defaults for aerodynamic design limits. A complete description of input and output along with sample cases are included.

Experimental investigation of lateral forces induced by flow through model labyrinth glands

NASA Technical Reports Server (NTRS)

Leong, Y. M. M. S.; Brown, R. D.

1984-01-01

The lateral forces induced by flow through model labyrinth glands were investigated. Circumferential pressure distributions, lateral forces and stiffness coefficients data obtained are discussed. The force system is represented as a negative spring and a tangential force orthogonal to eccentricity. The magnitude of these forces are dependent on eccentricity, entry swirl, rotor peripheral velocity and seal size. A pressure equalization chamber at midgland tests should in significantly reduced forces and stiffness coefficients.

Supersonic, subsonic and stationary filaments in the plasma focus

NASA Astrophysics Data System (ADS)

Nikulin, V. Ya; Startsev, S. A.; Tsybenko, S. P.

2017-10-01

Filaments in the plasma focus were investigated using a model of plasma with the London current. These structures involve a forward current that flows along the surface of a tangential discontinuity and reverse induction currents in the surrounding plasma, including those that flow over the surface of discontinuity, where the magnetic field reverses its direction. Supersonic filaments demonstrated the capture of plasma by the London current, and in subsonic and stationary filaments, the London current expelled the plasma.

Quantifying performance on an outdoor agility drill using foot-mounted inertial measurement units.

PubMed

Zaferiou, Antonia M; Ojeda, Lauro; Cain, Stephen M; Vitali, Rachel V; Davidson, Steven P; Stirling, Leia; Perkins, Noel C

2017-01-01

Running agility is required for many sports and other physical tasks that demand rapid changes in body direction. Quantifying agility skill remains a challenge because measuring rapid changes of direction and quantifying agility skill from those measurements are difficult to do in ways that replicate real task/game play situations. The objectives of this study were to define and to measure agility performance for a (five-cone) agility drill used within a military obstacle course using data harvested from two foot-mounted inertial measurement units (IMUs). Thirty-two recreational athletes ran an agility drill while wearing two IMUs secured to the tops of their athletic shoes. The recorded acceleration and angular rates yield estimates of the trajectories, velocities and accelerations of both feet as well as an estimate of the horizontal velocity of the body mass center. Four agility performance metrics were proposed and studied including: 1) agility drill time, 2) horizontal body speed, 3) foot trajectory turning radius, and 4) tangential body acceleration. Additionally, the average horizontal ground reaction during each footfall was estimated. We hypothesized that shorter agility drill performance time would be observed with small turning radii and large tangential acceleration ranges and body speeds. Kruskal-Wallis and mean rank post-hoc statistical analyses revealed that shorter agility drill performance times were observed with smaller turning radii and larger tangential acceleration ranges and body speeds, as hypothesized. Moreover, measurements revealed the strategies that distinguish high versus low performers. Relative to low performers, high performers used sharper turns, larger changes in body speed (larger tangential acceleration ranges), and shorter duration footfalls that generated larger horizontal ground reactions during the turn phases. Overall, this study advances the use of foot-mounted IMUs to quantify agility performance in contextually-relevant settings (e.g., field of play, training facilities, obstacle courses, etc.).

Preparative Purification of Recombinant Proteins: Current Status and Future Trends

PubMed Central

Saraswat, Mayank; Ravidá, Alessandra; Holthofer, Harry

2013-01-01

Advances in fermentation technologies have resulted in the production of increased yields of proteins of economic, biopharmaceutical, and medicinal importance. Consequently, there is an absolute requirement for the development of rapid, cost-effective methodologies which facilitate the purification of such products in the absence of contaminants, such as superfluous proteins and endotoxins. Here, we provide a comprehensive overview of a selection of key purification methodologies currently being applied in both academic and industrial settings and discuss how innovative and effective protocols such as aqueous two-phase partitioning, membrane chromatography, and high-performance tangential flow filtration may be applied independently of or in conjunction with more traditional protocols for downstream processing applications. PMID:24455685

Dynamics of fingertip contact during the onset of tangential slip

PubMed Central

Delhaye, Benoit; Lefèvre, Philippe; Thonnard, Jean-Louis

2014-01-01

Through highly precise perceptual and sensorimotor activities, the human tactile system continuously acquires information about the environment. Mechanical interactions between the skin at the point of contact and a touched surface serve as the source of this tactile information. Using a dedicated custom robotic platform, we imaged skin deformation at the contact area between the finger and a flat surface during the onset of tangential sliding movements in four different directions (proximal, distal, radial and ulnar) and with varying normal force and tangential speeds. This simple tactile event evidenced complex mechanics. We observed a reduction of the contact area while increasing the tangential force and proposed to explain this phenomenon by nonlinear stiffening of the skin. The deformation's shape and amplitude were highly dependent on stimulation direction. We conclude that the complex, but highly patterned and reproducible, deformations measured in this study are a potential source of information for the central nervous system and that further mechanical measurement are needed to better understand tactile perceptual and motor performances. PMID:25253033

EVALUATION OF UTILITY BOILER RADIANT FURNACE RESIDENCE TIME/TEMPERATURE CHARACTERISTICS: FIELD TESTS AND HEAT TRANSFER MODELING

EPA Science Inventory

The report describes an investigation of the adequacy of a modeling approach in predicting the thermal environment and flow field of pulverized-coal-fired utility boilers. Two 420 MWe coal-fired boilers were evaluated: a single-wall-fired unit and a tangentially fired unit, repre...

Effect of filtration rates on hollow fiber ultrafilter concentration of viruses and protozoans from large volumes of water

EPA Science Inventory

Aims: To describe the ability of tangential flow hollow-fiber ultrafiltration to recover viruses from large volumes of water when run either at high filtration rates or lower filtration rates and recover Cryptosporidium parvum at high filtration rates. Methods and Results: Wate...

Numerical analysis of finite Debye-length effects in induced-charge electro-osmosis.

PubMed

Gregersen, Misha Marie; Andersen, Mathias Baekbo; Soni, Gaurav; Meinhart, Carl; Bruus, Henrik

2009-06-01

For a microchamber filled with a binary electrolyte and containing a flat unbiased center electrode at one wall, we employ three numerical models to study the strength of the resulting induced-charge electro-osmotic (ICEO) flow rolls: (i) a full nonlinear continuum model resolving the double layer, (ii) a linear slip-velocity model not resolving the double layer and without tangential charge transport inside this layer, and (iii) a nonlinear slip-velocity model extending the linear model by including the tangential charge transport inside the double layer. We show that, compared to the full model, the slip-velocity models significantly overestimate the ICEO flow. This provides a partial explanation of the quantitative discrepancy between observed and calculated ICEO velocities reported in the literature. The discrepancy increases significantly for increasing Debye length relative to the electrode size, i.e., for nanofluidic systems. However, even for electrode dimensions in the micrometer range, the discrepancies in velocity due to the finite Debye length can be more than 10% for an electrode of zero height and more than 100% for electrode heights comparable to the Debye length.

Purification of infectious adenovirus in two hours by ultracentrifugation and tangential flow filtration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ugai, Hideyo; Yamasaki, Takahito; Hirose, Megumi

2005-06-17

Adenoviruses are excellent vectors for gene transfer and are used extensively for high-level expression of the products of transgenes in living cells. The development of simple and rapid methods for the purification of stable infectious recombinant adenoviruses (rAds) remains a challenge. We report here a method for the purification of infectious adenovirus type 5 (Ad5) that involves ultracentrifugation on a cesium chloride gradient at 604,000g for 15 min at 4 deg C and tangential flow filtration. The entire procedure requires less than two hours and infectious Ad5 can be recovered at levels higher than 64% of the number of plaque-formingmore » units (pfu) in the initial crude preparation of viruses. We have obtained titers of infectious purified Ad5 of 1.35 x 10{sup 10} pfu/ml and a ratio of particle titer to infectious titer of seven. The method described here allows the rapid purification of rAds for studies of gene function in vivo and in vitro, as well as the rapid purification of Ad5.« less

LES of stratified-wavy flows using novel near-interface treatment

NASA Astrophysics Data System (ADS)

Karnik, Aditya; Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Matar, Omar K.

2017-11-01

The pressure drop in horizontal stratified wavy flows is influenced by interfacial shear stress. The near-interface behavior of the lighter phase is akin to that near a moving wall. We employ a front-tracking code, Blue, to simulate and capture the near-interface behaviour of both phases. Blue uses a modified Smagorinsky LES model incorporating a novel near-interface treatment for the sub-grid viscosity, which is influenced by damping due to the wall-like interface, and enhancement of the turbulent kinetic energy (TKE) due to the interfacial waves. Simulations are carried out for both air-water and oil-water stratified configurations to demonstrate the applicability of the present method. The mean velocities and tangential Reynolds stresses are compared with experiments for both configurations. At the higher Re, the waves penetrate well into the buffer region of the boundary layer above the interface thus altering its dynamics. Previous attempts to capture the secondary structures associated with such flows using RANS or standard LES methodologies have been unsuccessful. The ability of the present method to reproduce these structures is due to the correct estimation of the near-interface TKE governing energy transfer from the normal to tangential directions. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM).

The combustion of different air distribution of foursquare tangential circle boiler by numerical simulation

NASA Astrophysics Data System (ADS)

Guo, Yue; Du, Lei; Jiang, Long; Li, Qing; Zhao, Zhenning

2017-01-01

In this paper, the combustion and NOx emission characteristics of a 300 MW tangential boiler are simulated, we obtain the flue gas velocity field in the hearth, component concentration distribution of temperature field and combustion products, and the speed, temperature, concentration of oxygen and NOx emissions compared with the test results in the waisting air distribution conditions, found the simulation values coincide well with the test value, to verify the rationality of the model. At the same time, the flow field in the furnace, the combustion and the influence of NOx emission characteristics are simulated by different conditions, including compared with primary zone secondary waisting air distribution, uniform air distribution and pagodas go down air distribution, the results show that, waisting air distribution is useful to reduce NOx emissions.

The numerical modelling of mixing phenomena of nanofluids in passive micromixers

NASA Astrophysics Data System (ADS)

Milotin, R.; Lelea, D.

2018-01-01

The paper deals with the rapid mixing phenomena in micro-mixing devices with four tangential injections and converging tube, considering nanoparticles and water as the base fluid. Several parameters like Reynolds number (Re = 6 - 284) or fluid temperature are considered in order to optimize the process and obtain fundamental insight in mixing phenomena. The set of partial differential equations is considered based on conservation of momentum and species. Commercial package software Ansys-Fluent is used for solution of differential equations, based on a finite volume method. The results reveal that mixing index and mixing process is strongly dependent both on Reynolds number and heat flux. Moreover there is a certain Reynolds number when flow instabilities are generated that intensify the mixing process due to the tangential injections of the fluids.

Kinetic theory for identical, frictional, nearly elastic disks

NASA Astrophysics Data System (ADS)

Yoon, David K.; Jenkins, James T.

2005-08-01

We develop kinetic theory for slightly frictional and nearly elastic disks. The tangential interaction is modeled by two parameters: a Coulomb friction coefficient and a tangential restitution coefficient. Assuming Maxwellian velocity distribution functions for both translational and rotational velocities, we derive exact expressions for the rates of dissipation of translational and rotational fluctuation energies per unit area. Setting the rotational dissipation rate to zero, as in a steady, homogeneous shearing flow, we find the ratio of the rotational temperature to the translational. In the case of small friction, this is used to determine an effective coefficient of normal restitution. In this way, the effects of small friction can be incorporated into the theory, thereby dispensing with the need to separately consider the complete balances for the momentum and the energy of the rotational motion.

SIMULATIONS OF THE KELVIN–HELMHOLTZ INSTABILITY DRIVEN BY CORONAL MASS EJECTIONS IN THE TURBULENT CORONA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gómez, Daniel O.; DeLuca, Edward E.; Mininni, Pablo D.

Recent high-resolution Atmospheric Imaging Assembly/Solar Dynamics Observatory images show evidence of the development of the Kelvin–Helmholtz (KH) instability, as coronal mass ejections (CMEs) expand in the ambient corona. A large-scale magnetic field mostly tangential to the interface is inferred, both on the CME and on the background sides. However, the magnetic field component along the shear flow is not strong enough to quench the instability. There is also observational evidence that the ambient corona is in a turbulent regime, and therefore the criteria for the development of the instability are a priori expected to differ from the laminar case. To studymore » the evolution of the KH instability with a turbulent background, we perform three-dimensional simulations of the incompressible magnetohydrodynamic equations. The instability is driven by a velocity profile tangential to the CME–corona interface, which we simulate through a hyperbolic tangent profile. The turbulent background is generated by the application of a stationary stirring force. We compute the instability growth rate for different values of the turbulence intensity, and find that the role of turbulence is to attenuate the growth. The fact that KH instability is observed sets an upper limit on the correlation length of the coronal background turbulence.« less

Grazing incidence toroidal mirror pairs in imaging and spectroscopic applications.

PubMed

Malvezzi, A M; Tondello, G

1983-08-15

The optical performance of pairs of toroidal mirrors in grazing incidence has been studied analytically and numerically. Two types of toroidal surface are possible: football and bicycle tire. In grazing incidence and for configurations that compensate up to second-order aberrations, there are significant differences in performance between the two types. For football-type tori the best configuration appears to be Z-shaped with tangential and sagittal foci at the middle point between the mirrors. For bicycle tire-type tori the best configuration is U-shaped with the tangential focus at the middle point and the sagittal at infinity.

A comprehensive cold gas performance study of the Pocket Rocket radiofrequency electrothermal microthruster

NASA Astrophysics Data System (ADS)

Ho, Teck Seng; Charles, Christine; Boswell, Roderick W.

2016-12-01

This paper presents computational fluid dynamics simulations of the cold gas operation of Pocket Rocket and Mini Pocket Rocket radiofrequency electrothermal microthrusters, replicating experiments performed in both sub-Torr and vacuum environments. This work takes advantage of flow velocity choking to circumvent the invalidity of modelling vacuum regions within a CFD simulation, while still preserving the accuracy of the desired results in the internal regions of the microthrusters. Simulated results of the plenum stagnation pressure is in precise agreement with experimental measurements when slip boundary conditions with the correct tangential momentum accommodation coefficients for each gas are used. Thrust and specific impulse is calculated by integrating the flow profiles at the exit of the microthrusters, and are in good agreement with experimental pendulum thrust balance measurements and theoretical expectations. For low thrust conditions where experimental instruments are not sufficiently sensitive, these cold gas simulations provide additional data points against which experimental results can be verified and extrapolated. The cold gas simulations presented in this paper will be used as a benchmark to compare with future plasma simulations of the Pocket Rocket microthruster.

Numerical study of delta wing leading edge blowing

NASA Technical Reports Server (NTRS)

Yeh, David; Tavella, Domingo; Roberts, Leonard

1988-01-01

Spanwise and tangential leading edge blowing as a means of controlling the position and strength of the leading edge vortices are studied by numerical solution of the three-dimensional Navier-Stokes equations. The leading edge jet is simulated by defining a permeable boundary, corresponding to the jet slot, where suitable boundary conditions are implemented. Numerical results are shown to compare favorably with experimental measurements. It is found that the use of spanwise leading edge blowing at moderate angle of attack magnifies the size and strength of the leading edge vortices, and moves the vortex cores outboard and upward. The increase in lift primarily comes from the greater nonlinear vortex lift. However, spanwise blowing causes earlier vortex breakdown, thus decreasing the stall angle. The effects of tangential blowing at low to moderate angles of attack tend to reduce the pressure peaks associated with leading edge vortices and to increase the suction peak around the leading edge, so that the integrated value of the surface pressure remains about the same. Tangential leading edge blowing in post-stall conditions is shown to re-establish vortical flow and delay vortex bursting, thus increasing C sub L sub max and stall angle.

Test results for rotordynamic coefficients of anti-swirl self-injection seals

NASA Technical Reports Server (NTRS)

Kim, C. H.; Lee, Y. B.

1994-01-01

Test results are presented for rotordynamic coefficients and leakage for three annular seals which use anti-swirl self-injection concept to yield significant improvement in whirl frequency ratios as compared to smooth and damper seals. A new anti-swirl self-inection mechanism is achieved by deliberately machining self-injection holes inside the seal stator mechanism which is used to achieve effective reduction of the tangential flow which is considered as a prime cause of rotor instability in high performance turbomachinery. Test results show that the self-injection mechanism significantly improves whirl frequency ratios; however, the leakage performance degrades due to the introduction of the self-injection mechanism. Through a series of the test program, an optimum anti-swirl self-injection seal which uses a labyrinth stator surface with anti-axial flow injections is selected to obtain a significant improvement in the whirl frequency ratio as compared to a damper seal, while showing moderate leakage performance. Best whirl frequency ratio is achieved by an anti-swirl self-injection seal of 12 holes anti-swirl and 6 degree anti-leakage injection with a labyrinth surface configuration. When compared to a damper seal, the optimum configuration outperforms the whirl frequency ratio by a factor of 2.

LDV survey of cavitation and resonance effect on the precessing vortex rope dynamics in the draft tube of Francis turbines

NASA Astrophysics Data System (ADS)

Favrel, A.; Müller, A.; Landry, C.; Yamamoto, K.; Avellan, F.

2016-11-01

The large-scale penetration of the electrical grid by intermittent renewable energy sources requires a continuous operating range extension of hydropower plants. This causes the formation of unfavourable flow patterns in the draft tube of turbines and pump-turbines. At partial load operation, a precessing cavitation vortex rope is formed at the Francis turbine runner outlet, acting as an excitation source for the hydraulic system. In case of resonance, the resulting high-amplitude pressure pulsations can put at risk the stability of the machine and of the electrical grid to which it is connected. It is therefore crucial to understand and accurately simulate the underlying physical mechanisms in such conditions. However, the exact impact of cavitation and hydro-acoustic resonance on the flow velocity fluctuations in the draft tube remains to be established. The flow discharge pulsations expected to occur in the draft tube in resonance conditions have for instance never been verified experimentally. In this study, two-component Laser Doppler Velocimetry is used to investigate the axial and tangential velocity fluctuations at the runner outlet of a reduced scale physical model of a Francis turbine. The investigation is performed for a discharge equal to 64 % of the nominal value and three different pressure levels in the draft tube, including resonance and cavitation-free conditions. Based on the convective pressure fluctuations induced by the vortex precession, the periodical velocity fluctuations over one typical precession period are recovered by phase averaging. The impact of cavitation and hydro-acoustic resonance on both axial and tangential velocity fluctuations in terms of amplitude and phase shift is highlighted for the first time. It is shown that the occurrence of resonance does not have significant effects on the draft tube velocity fields, suggesting that the synchronous axial velocity fluctuations are surprisingly negligible compared to the velocity fluctuations induced by the vortex precession.

Off-design flow measurements in a centrifugal compressor vaneless diffuser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinarbasi, A.; Johnson, M.W.

1995-10-01

Detailed measurements have been taken of the three-dimensional velocity field within the vaneless diffuser of a backswept low speed centrifugal compressor using hot-wire anemometry. A 16% below and an 11% above design flow rate were used in the present study. Results at both flow rates show how the blade wake mixes out more rapidly than the passage wake. Strong secondary flows inherited from the impeller at the higher flow rate delay the mixing out of the circumferential velocity variations, but at both flow rates these circumferential variations are negligible at the last measurement station. The measured tangential/radial flow angle ismore » used to recommend optimum values for the vaneless space and vane angle for design of a vaned diffuser.« less

Tangential migratory pathways of subpallial origin in the embryonic telencephalon of sharks: evolutionary implications.

PubMed

Quintana-Urzainqui, Idoia; Rodríguez-Moldes, Isabel; Mazan, Sylvie; Candal, Eva

2015-09-01

Tangential neuronal migration occurs along different axes from the axis demarcated by radial glia and it is thought to have evolved as a mechanism to increase the diversity of cell types in brain areas, which in turn resulted in increased complexity of functional networks. In the telencephalon of amniotes, different embryonic tangential pathways have been characterized. However, little is known about the exact routes of migrations in basal vertebrates. Cartilaginous fishes occupy a key phylogenetic position to assess the ancestral condition of vertebrate brain organization. In order to identify putative subpallial-derived tangential migratory pathways in the telencephalon of sharks, we performed a detailed analysis of the distribution pattern of GAD and Dlx2, two reliable markers of tangentially migrating interneurons of subpallial origin in the developing forebrain. We propose the existence of five tangential routes directed toward different telencephalic regions. We conclude that four of the five routes might have emerged in the common ancestor of jawed vertebrates. We have paid special attention to the characterization of the proposed migratory pathway directed towards the olfactory bulbs. Our results suggest that it may be equivalent to the "rostral migratory stream" of mammals and led us to propose a hypothesis about its evolution. The analysis of the final destinations of two other streams allowed us to identify the putative dorsal and medial pallium of sharks, the regions from which the neocortex and hippocampus might have, respectively, evolved. Derived features were also reported and served to explain some distinctive traits in the morphology of the telencephalon of cartilaginous fishes.

Is effective force application in handrim wheelchair propulsion also efficient?

PubMed

Bregman, D J J; van Drongelen, S; Veeger, H E J

2009-01-01

Efficiency in manual wheelchair propulsion is low, as is the fraction of the propulsion force that is attributed to the moment of propulsion of the wheelchair. In this study we tested the hypothesis that a tangential propulsion force direction leads to an increase in physiological cost, due to (1) the sub-optimal use of elbow flexors and extensors, and/or (2) the necessity of preventing of glenohumeral subluxation. Five able-bodied and 11 individuals with a spinal cord injury propelled a wheelchair while kinematics and kinetics were collected. The results were used to perform inverse dynamical simulations with input of (1) the experimentally obtained propulsion force, and (2) only the tangential component of that force. In the tangential force condition the physiological cost was over 30% higher, while the tangential propulsion force was only 75% of the total experimental force. According to model estimations, the tangential force condition led to more co-contraction around the elbow, and a higher power production around the shoulder joint. The tangential propulsion force led to a significant, but small 4% increase in necessity for the model to compensate for glenohumeral subluxation, which indicates that this is not a likely cause of the decrease in efficiency. The present findings support the hypothesis that the observed force direction in wheelchair propulsion is a compromise between efficiency and the constraints imposed by the wheelchair-user system. This implies that training should not be aimed at optimization of the propulsion force, because this may be less efficient and more straining for the musculoskeletal system.

Development of Semi-Span Model Test Techniques

NASA Technical Reports Server (NTRS)

Pulnam, L. Elwood (Technical Monitor); Milholen, William E., II; Chokani, Ndaona; McGhee, Robert J.

1996-01-01

A computational investigation was performed to support the development of a semi-span model test capability in the NASA Langley Research Center's National Transonic Facility. This capability is desirable for the testing of advanced subsonic transport aircraft at full-scale Reynolds numbers. A state-of-the-art three-dimensional Navier-Stokes solver was used to examine methods to improve the flow over a semi-span configuration. First, a parametric study is conducted to examine the influence of the stand-off height on the flow over the semi-span model. It is found that decreasing the stand-off height, below the maximum fuselage radius, improves the aerodynamic characteristics of the semi-span model. Next, active sidewall boundary layer control techniques are examined. Juncture region blowing jets, upstream tangential blowing, and sidewall suction are found to improve the flow over the aft portion of the semi-span model. Both upstream blowing and suction are found to reduce the sidewall boundary layer separation. The resulting near surface streamline patterns are improved, and found to be quite similar to the full-span results. Both techniques however adversely affect the pitching moment coefficient.

Development of Semi-Span Model Test Techniques

NASA Technical Reports Server (NTRS)

Milholen, William E., II; Chokani, Ndaona; McGhee, Robert J.

1996-01-01

A computational investigation was performed to support the development of a semispan model test capability in the NASA Langley Research Center's National Transonic Facility. This capability is desirable for the testing of advanced subsonic transport aircraft at full-scale Reynolds numbers. A state-of-the-art three-dimensional Navier-Stokes solver was used to examine methods to improve the flow over a semi-span configuration. First, a parametric study is conducted to examine the influence of the stand-off height on the flow over the semispan model. It is found that decreasing the stand-off height, below the maximum fuselage radius, improves the aerodynamic characteristics of the semi-span model. Next, active sidewall boundary layer control techniques are examined. Juncture region blowing jets, upstream tangential blowing, and sidewall suction are found to improve the flow over the aft portion of the semispan model. Both upstream blowing and suction are found to reduce the sidewall boundary layer separation. The resulting near surface streamline patterns are improved, and found to be quite similar to the full-span results. Both techniques however adversely affect the pitching moment coefficient.

Experiments in Aircraft Roll-Yaw Control using Forebody Tangential Blowing

NASA Technical Reports Server (NTRS)

Pedreiro, Nelson

1997-01-01

Advantages of flight at high angles of attack include increased maneuverability and lift capabilities. These are beneficial not only for fighter aircraft, but also for future supersonic and hypersonic transport aircraft during take-off and landing. At high angles of attack the aerodynamics of the vehicle are dominated by separation, vortex shedding and possibly vortex breakdown. These phenomena severely compromise the effectiveness of conventional control surfaces. As a result, controlled flight at high angles of attack is not feasible for current aircraft configurations. Alternate means to augment the control of the vehicle at these flight regimes are therefore necessary. The present work investigates the augmentation of an aircraft flight control system by the injection of a thin sheet of air tangentially to the forebody of the vehicle. This method, known as Forebody Tangential Blowing (FTB), has been proposed as an effective means of increasing the controllability of aircraft at high angles of attack. The idea is based on the fact that a small amount of air is sufficient to change the separation lines on the forebody. As a consequence, the strength and position of the vortices are altered causing a change on the aerodynamic loads. Although a very effective actuator, forebody tangential blowing is also highly non-linear which makes its use for aircraft control very difficult. In this work, the feasibility of using FTB to control the roll-yaw motion of a wind tunnel model was demonstrated both through simulations and experimentally. The wind tunnel model used in the experiments consists of a wing-body configuration incorporating a delta wing with 70-degree sweep angle and a cone-cylinder fuselage. The model is equipped with forebody slots through which blowing is applied. There are no movable control surfaces, therefore blowing is the only form of actuation. Experiments were conducted at a nominal angle of attack of 45 degrees. A unique apparatus that constrains the model to two degrees-of-freedom, roll and yaw, was designed and built. The apparatus was used to conduct dynamic experiments which showed that the system was unstable, its natural motion divergent. A model for the unsteady aerodynamic loads was developed based on the basic physics of the flow and results from flow visualization experiments. Parameters of the aerodynamic model were identified from experimental data. The model was validated using data from dynamic experiments. The aerodynamic model completes the equations of motion of the system which were used in the design of control laws using blowing as the only actuator. The unsteady aerodynamic model was implemented as part of the real-time vehicle control system. A control strategy using asymmetric blowing was demonstrated experimentally. A discrete vortex method was developed to help understand the main physics of the flow. The method correctly captures the interactions between forebody and wing vortices. Moreover, the trends in static loads and flow structure are correctly represented. Flow visualization results revealed the vortical structure of the flow to be asymmetric even for symmetric flight conditions. The effects of blowing, and roll and yaw angles on the flow structure were determined. It is shown that superimposing symmetric and asymmetric blowing has a linearizing effect on the actuator characteristics. Transient responses of roll and yaw moments to step input blowing were characterized, and their differences were explained based on the physical mechanisms through which these loads are generated.

Inductively coupled helium plasma torch

DOEpatents

Montaser, Akbar; Chan, Shi-Kit; Van Hoven, Raymond L.

1989-01-01

An inductively coupled plasma torch including a base member, a plasma tube and a threaded insert member within the plasma tube for directing the plasma gas in a tangential flow pattern. The design of the torch eliminates the need for a separate coolant gas tube. The torch can be readily assembled and disassembled with a high degree of alignment accuracy.

Computational domain discretization in numerical analysis of flow within granular materials

NASA Astrophysics Data System (ADS)

Sosnowski, Marcin

2018-06-01

The discretization of computational domain is a crucial step in Computational Fluid Dynamics (CFD) because it influences not only the numerical stability of the analysed model but also the agreement of obtained results and real data. Modelling flow in packed beds of granular materials is a very challenging task in terms of discretization due to the existence of narrow spaces between spherical granules contacting tangentially in a single point. Standard approach to this issue results in a low quality mesh and unreliable results in consequence. Therefore the common method is to reduce the diameter of the modelled granules in order to eliminate the single-point contact between the individual granules. The drawback of such method is the adulteration of flow and contact heat resistance among others. Therefore an innovative method is proposed in the paper: single-point contact is extended to a cylinder-shaped volume contact. Such approach eliminates the low quality mesh elements and simultaneously introduces only slight distortion to the flow as well as contact heat transfer. The performed analysis of numerous test cases prove the great potential of the proposed method of meshing the packed beds of granular materials.

Slip and accommodation coefficients from rarefaction and roughness in rotating microscale disk flows

NASA Astrophysics Data System (ADS)

Blanchard, Danny; Ligrani, Phil

2007-06-01

Accommodation coefficients are determined from experimental results and analysis based on the Navier-Stokes equations for rotation-induced flows in C-shaped fluid chamber passages formed between a rotating disk and a stationary surface. A first-order boundary condition is used to model the slip flow. The fluid chamber passage height ranges from 6.85to29.2μm to give Knudsen numbers from 0.0025 to 0.031 for air and helium. In all cases, roughness size is large compared to molecular mean free path. The unique method presented for deducing tangential momentum accommodation coefficients gives values with less uncertainty compared to procedures that rely on flows in stationary tubes and channels. When channel height is defined at the tops of the roughness elements, slip velocity magnitudes and associated accommodation coefficients are a result of rarefaction at solid-gas interfaces and shear at the gas-gas interfaces. With this arrangement, tangential accommodation coefficients obtained with this approach decrease, and slip velocity magnitudes increase, at a particular value of Knudsen number, as the level of surface roughness increases. At values of the mean roughness height greater than 500nm, accommodation coefficients then appear to be lower in air flows than in helium flows, when compared for a particular roughness configuration. When channel height is defined midway between the crests and troughs of the roughness elements, nondimensional pressure rise data show little or no dependence on the level of disk surface roughness and working fluid. With this arrangement, slip is largely independent of surface roughness magnitude and mostly due to rarefaction, provided the appropriate channel height is chosen to define the roughness height.

Bendable Focusing X-Ray Optics for the ALS and the LCLS/FEL: Design, Metrology, and Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yashchuk, V. V.; Yuan, S.; Baker, S.

2010-06-02

We review the recent development of bendable x-ray optics used for focusing of beams of soft and hard x-rays at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory and at the Linac Coherent Light Source (LCLS) x-ray free electron laser (FEL) at the Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory. For simultaneous focusing in the tangential and sagittal directions, two elliptically cylindrical reflecting elements, a Kirkpatrick-Baez (KB) pair, are used. Because fabrication of elliptical surfaces is complicated, the cost of directly fabricated tangential elliptical cylinders is often prohibitive. Moreover, such optics cannot be easily readjusted for usemore » in multiple, different experimental arrangements, e.g. at different focal distances. This is in contrast to flat optics that are simpler to manufacture and easier to measure by conventional interferometry. The tangential figure of a flat substrate is changed by placing torques (couples) at each end. Depending on the applied couples, one can tune the shape close to a desired tangential cylinder, ellipse or parabola. We review the nature of the bending, requirements and approaches to the mechanical design, describe original optical and at-wavelength techniques for optimal tuning of bendable optics and alignment on the beamline, and provide beamline performance of the bendable optics used for sub-micro and nano focusing of soft x-rays.« less

Bi-tangential hybrid IMRT for sparing the shoulder in whole breast irradiation.

PubMed

Farace, P; Deidda, M A; Iamundo de Cumis, I; Iamundo de Curtis, I; Deiana, E; Farigu, R; Lay, G; Porru, S

2013-11-01

A bi-tangential technique is proposed to reduce undesired doses to the shoulder produced by standard tangential irradiation. A total of 6 patients affected by shoulder pain and reduced functional capacity after whole-breast irradiation were retrospectively analysed. The standard tangential plan used for treatment was compared with (1) a single bi-tangential plan where, to spare the shoulder, the lateral open tangent was split into two half-beams at isocentre, with the superior portion rotated by 10-20° medially with respect to the standard lateral beam; (2) a double bi-tangential plan, where both the tangential open beams were split. The planning target volume (PTV) coverage and the dose to the portion of muscles and axilla included in the standard tangential beams were compared. PTV95 % of standard plan (91.9 ± 3.8) was not significantly different from single bi-tangential plan (91.8 ± 3.4); a small but significant (p < 0.01) decrease was observed with the double bi-tangential plan (90.1 ± 3.7). A marked dose reduction to the muscle was produced by the single bi-tangential plan around 30-40 Gy. The application of the double bi-tangential technique further reduced the volume receiving around 20 Gy, but did not markedly affect the higher doses. The dose to the axilla was reduced both in the single and the double bi-tangential plans. The single bi-tangential technique would have been able to reduce the dose to shoulder and axilla, without compromising target coverage. This simple technique is valuable for irradiation after axillary lymph node dissection or in patients without dissection due to negative or low-volume sentinel lymph node disease.

Performance of Several Combustion Chambers Designed for Aircraft Oil Engines

NASA Technical Reports Server (NTRS)

Joachim, William F; Kemper, Carlton

1928-01-01

Several investigations have been made on single-cylinder test engines to determine the performance characteristics of four types of combustion chambers designed for aircraft oil engines. Two of the combustion chambers studied were bulb-type precombustion chambers, the connecting orifice of one having been designed to produce high turbulence by tangential air flow in both the precombustion chamber and the cylinder. The other two were integral combustion chambers, one being dome-shaped and the other pent-roof shaped. The injection systems used included cam and eccentric driven fuel pumps, and diaphragm and spring-loaded fuel-injection valves. A diaphragm type maximum cylinder pressure indicator was used in part of these investigations with which the cylinder pressures were controlled to definite valves. The performance of the engines when equipped with each of the combustion chambers is discussed. The best performance for the tests reported was obtained with a bulb-type combustion chamber designed to give a high degree of turbulence within the bulb and cylinder. (author)

Spatially resolved vertical vorticity in solar supergranulation using helioseismology and local correlation tracking

NASA Astrophysics Data System (ADS)

Langfellner, J.; Gizon, L.; Birch, A. C.

2015-09-01

Flow vorticity is a fundamental property of turbulent convection in rotating systems. Solar supergranules exhibit a preferred sense of rotation, which depends on the hemisphere. This is due to the Coriolis force acting on the diverging horizontal flows. We aim to spatially resolve the vertical flow vorticity of the average supergranule at different latitudes, both for outflow and inflow regions. To measure the vertical vorticity, we use two independent techniques: time-distance helioseismology (TD) and local correlation tracking of granules in intensity images (LCT) using data from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Both maps are corrected for center-to-limb systematic errors. We find that 8 h TD and LCT maps of vertical vorticity are highly correlated at large spatial scales. Associated with the average supergranule outflow, we find tangential (vortical) flows that reach about 10 m s-1 in the clockwise direction at 40° latitude. In average inflow regions, the tangential flow reaches the same magnitude, but in the anticlockwise direction. These tangential velocities are much smaller than the radial (diverging) flow component (300 m s-1 for the average outflow and 200 m s-1 for the average inflow). The results for TD and LCT as measured from HMI are in excellent agreement for latitudes between -60° and 60°. From HMI LCT, we measure the vorticity peak of the average supergranule to have a full width at half maximum of about 13 Mm for outflows and 8 Mm for inflows. This is larger than the spatial resolution of the LCT measurements (about 3 Mm). On the other hand, the vorticity peak in outflows is about half the value measured at inflows (e.g., 4 × 10-6 s-1 clockwise compared to 8 × 10-6 s-1 anticlockwise at 40° latitude). Results from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) obtained in 2010 are biased compared to the HMI/SDO results for the same period. Appendices are available in electronic form at http://www.aanda.orgThe azimuthally averaged velocity components vr and vt for supergranular outflows and inflows at various latitudes are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A67

Performance tests with a 4.75 inch bore tapered-roller bearings at high speeds

NASA Technical Reports Server (NTRS)

Signer, H. R.; Pinel, S. I.

1977-01-01

The tapered-roller bearings were tested at speeds to 15,000 rpm which results in a cone-rib tangential velocity of 130 m/sec. (25,500 ft/min). Lubrication was applied either by jets or directly to the cone-rib, augmented with jets. Additional test parameters included thrust loads to 53,400 N (12,000 lbs), radial loads to 26,700 N (6,000 lbs), lubricant flow rates from 1.9 x 0.000 to 15.1 x 0.001 cubic meter/min. (0.5 to 4.0 gpm), and lubricant inlet temperatures of 350 K and 364 K (170 F and 195 F). Temperature distribution, separator speed, and drive-motor power demand were determined as functions of these test parameters.

Visuomotor Transformation in the Fly Gaze Stabilization System

PubMed Central

Huston, Stephen J; Krapp, Holger G

2008-01-01

For sensory signals to control an animal's behavior, they must first be transformed into a format appropriate for use by its motor systems. This fundamental problem is faced by all animals, including humans. Beyond simple reflexes, little is known about how such sensorimotor transformations take place. Here we describe how the outputs of a well-characterized population of fly visual interneurons, lobula plate tangential cells (LPTCs), are used by the animal's gaze-stabilizing neck motor system. The LPTCs respond to visual input arising from both self-rotations and translations of the fly. The neck motor system however is involved in gaze stabilization and thus mainly controls compensatory head rotations. We investigated how the neck motor system is able to selectively extract rotation information from the mixed responses of the LPTCs. We recorded extracellularly from fly neck motor neurons (NMNs) and mapped the directional preferences across their extended visual receptive fields. Our results suggest that—like the tangential cells—NMNs are tuned to panoramic retinal image shifts, or optic flow fields, which occur when the fly rotates about particular body axes. In many cases, tangential cells and motor neurons appear to be tuned to similar axes of rotation, resulting in a correlation between the coordinate systems the two neural populations employ. However, in contrast to the primarily monocular receptive fields of the tangential cells, most NMNs are sensitive to visual motion presented to either eye. This results in the NMNs being more selective for rotation than the LPTCs. Thus, the neck motor system increases its rotation selectivity by a comparatively simple mechanism: the integration of binocular visual motion information. PMID:18651791

Pulverized fuel-oxygen burner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, Curtis; Patterson, Brad; Perdue, Jayson

A burner assembly combines oxygen and fuel to produce a flame. The burner assembly includes an oxygen supply tube adapted to receive a stream of oxygen and a solid fuel conduit arranged to extend through the oxygen tube to convey a stream of fluidized, pulverized, solid fuel into a flame chamber. Oxygen flowing through the oxygen supply tube passes generally tangentially through a first set of oxygen-injection holes formed in the solid fuel conduit and off-tangentially from a second set of oxygen-injection holes formed in the solid fuel conduit and then mixes with fluidized, pulverized, solid fuel passing through themore » solid fuel conduit to create an oxygen-fuel mixture in a downstream portion of the solid fuel conduit. This mixture is discharged into a flame chamber and ignited in the flame chamber to produce a flame.« less

A computer program for performance prediction of tripropellant rocket engines with tangential slot injection

NASA Technical Reports Server (NTRS)

Dang, Anthony; Nickerson, Gary R.

1987-01-01

For the development of a Heavy Lift Launch Vehicle (HLLV) several engines with different operating cycles and using LOX/Hydrocarbon propellants are presently being examined. Some concepts utilize hydrogen for thrust chamber wall cooling followed by a gas generator turbine drive cycle with subsequent dumping of H2/O2 combustion products into the nozzle downstream of the throat. In the Space Transportation Booster Engine (STBE) selection process the specific impulse will be one of the optimization criteria; however, the current performance prediction programs do not have the capability to include a third propellant in this process, nor to account for the effect of dumping the gas-generator product tangentially inside the nozzle. The purpose is to describe a computer program for accurately predicting the performance of such an engine. The code consists of two modules; one for the inviscid performance, and the other for the viscous loss. For the first module, the two-dimensional kinetics program (TDK) was modified to account for tripropellant chemistry, and for the effect of tangential slot injection. For the viscous loss, the Mass Addition Boundary Layer program (MABL) was modified to include the effects of the boundary layer-shear layer interaction, and tripropellant chemistry. Calculations were made for a real engine and compared with available data.

Structure Optimization of a Grain Impact Piezoelectric Sensor and Its Application for Monitoring Separation Losses on Tangential-Axial Combine Harvesters

PubMed Central

Liang, Zhenwei; Li, Yaoming; Zhao, Zhan; Xu, Lizhang

2015-01-01

Grain separation losses is a key parameter to weigh the performance of combine harvesters, and also a dominant factor for automatically adjusting their major working parameters. The traditional separation losses monitoring method mainly rely on manual efforts, which require a high labor intensity. With recent advancements in sensor technology, electronics and computational processing power, this paper presents an indirect method for monitoring grain separation losses in tangential-axial combine harvesters in real-time. Firstly, we developed a mathematical monitoring model based on detailed comparative data analysis of different feeding quantities. Then, we developed a grain impact piezoelectric sensor utilizing a YT-5 piezoelectric ceramic as the sensing element, and a signal process circuit designed according to differences in voltage amplitude and rise time of collision signals. To improve the sensor performance, theoretical analysis was performed from a structural vibration point of view, and the optimal sensor structural has been selected. Grain collide experiments have shown that the sensor performance was greatly improved. Finally, we installed the sensor on a tangential-longitudinal axial combine harvester, and grain separation losses monitoring experiments were carried out in North China, which results have shown that the monitoring method was feasible, and the biggest measurement relative error was 4.63% when harvesting rice. PMID:25594592

Structure optimization of a grain impact piezoelectric sensor and its application for monitoring separation losses on tangential-axial combine harvesters.

PubMed

Liang, Zhenwei; Li, Yaoming; Zhao, Zhan; Xu, Lizhang

2015-01-14

Grain separation losses is a key parameter to weigh the performance of combine harvesters, and also a dominant factor for automatically adjusting their major working parameters. The traditional separation losses monitoring method mainly rely on manual efforts, which require a high labor intensity. With recent advancements in sensor technology, electronics and computational processing power, this paper presents an indirect method for monitoring grain separation losses in tangential-axial combine harvesters in real-time. Firstly, we developed a mathematical monitoring model based on detailed comparative data analysis of different feeding quantities. Then, we developed a grain impact piezoelectric sensor utilizing a YT-5 piezoelectric ceramic as the sensing element, and a signal process circuit designed according to differences in voltage amplitude and rise time of collision signals. To improve the sensor performance, theoretical analysis was performed from a structural vibration point of view, and the optimal sensor structural has been selected. Grain collide experiments have shown that the sensor performance was greatly improved. Finally, we installed the sensor on a tangential-longitudinal axial combine harvester, and grain separation losses monitoring experiments were carried out in North China, which results have shown that the monitoring method was feasible, and the biggest measurement relative error was 4.63% when harvesting rice.

Aerodynamic tip desensitization in axial flow turbines

NASA Astrophysics Data System (ADS)

Dey, Debashis

The leakage flow near the tip of unshrouded rotor blades in axial turbines imposes significant thermal loads on the blade. It is also responsible for up to a third of aerodynamic losses in a turbine stage. The leakage flow, mainly induced by the pressure differential across the rotor tip section, usually rolls into a stream-wise vertical structure near the suction side part of the blade tip. The current study uses several concepts to reduce the severity of losses introduced by the leakage vortex. Three tip desensitization techniques, both active and passive, are examined. Coolant flow from a tip trench is used to counter the momentum of the leakage jet. Next, a very short winglet obtained by slightly extending the tip platform in the tangential direction is investigated. Lastly, the widely used concept of squealer tip is studied. The current investigation is performed in the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University. Rotating frame five hole probe measurements as well as stationary frame phase averaged total pressure measurements downstream of a single stage turbine facility were taken. The study enables one to draw conclusions about the nature of the flowfield in the rotor tip region. It also shows that significant efficiency gains could be obtained by using some of these techniques.

Uranium droplet core nuclear rocket

NASA Technical Reports Server (NTRS)

Anghaie, Samim

1991-01-01

Uranium droplet nuclear rocket is conceptually designed to utilize the broad temperature range ofthe liquid phase of metallic uranium in droplet configuration which maximizes the energy transfer area per unit fuel volume. In a baseline system dissociated hydrogen at 100 bar is heated to 6000 K, providing 2000 second of Isp. Fission fragments and intense radian field enhance the dissociation of molecular hydrogen beyond the equilibrium thermodynamic level. Uranium droplets in the core are confined and separated by an axisymmetric vortex flow generated by high velocity tangential injection of hydrogen in the mid-core regions. Droplet uranium flow to the core is controlled and adjusted by a twin flow nozzle injection system.

A comparison of instrumental dewatering methods for the separation and concentration of suspended sediment for subsequent trace element analysis

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Hooper, R.C.

1989-01-01

The continuous-flow centrifuges can process whole water at an influent feed rate of 41 per minute; however, when suspended sediment concentrations are low (<30 mg l-1), when small volumes of whole water are to be processed (30 to 401), or when suspended sediment mean grain size is very fine (<10 ??m), influent feed rates of 21 per minute may be more efficient. Tangential-flow filtration can be used to process samples at the rate of 11 per minute. -from Authors

Measurements of farfield sound generation from a flow-excited cavity

NASA Technical Reports Server (NTRS)

Block, P. J. W.; Heller, H.

1975-01-01

Results of 1/3-octave-band spectral measurements of internal pressures and the external acoustic field of a tangentially blown rectangular cavity are compared. Proposed mechanisms for sound generation are reviewed, and spectra and directivity plots of cavity noise are presented. Directivity plots show a slightly modified monopole pattern. Frequencies of cavity response are calculated using existing predictions and are compared with those obtained experimentally. The effect of modifying the upstream boundary layer on the noise was investigated, and its effectiveness was found to be a function of cavity geometry and flow velocity.

Asymmetrical reverse vortex flow due to induced-charge electro-osmosis around carbon stacking structures.

PubMed

Sugioka, Hideyuki

2011-05-01

Broken symmetry of vortices due to induced-charge electro-osmosis (ICEO) around stacking structures is important for the generation of a large net flow in a microchannel. Following theoretical predictions in our previous study, we herein report experimental observations of asymmetrical reverse vortex flows around stacking structures of carbon posts with a large height (~110 μm) in water, prepared by the pyrolysis of a photoresist film in a reducing gas. Further, by the use of a coupled calculation method that considers boundary effects precisely, the experimental results, except for the problem of anomalous flow reversal, are successfully explained. That is, unlike previous predictions, the precise calculations here show that stacking structures accelerate a reverse flow rather than suppressing it for a microfluidic channel because of the deformation of electric fields near the stacking portions; these structures can also generate a large net flow theoretically in the direction opposite that of a previous prediction for a standard vortex flow. Furthermore, by solving the one-dimensional Poisson-Nernst-Plank (PNP) equations in the presence of ac electric fields, we find that the anomalous flow reversal occurs by the phase retardation between the induced diffuse charge and the tangential electric field. In addition, we successfully explain the nonlinearity of the flow velocity on the applied voltage by the PNP analysis. In the future, we expect to improve the pumping performance significantly by using stacking structures of conductive posts along with a low-cost process. © 2011 American Physical Society

Axial vane-type swirler performance characteristics. M.S. Thesis

NASA Technical Reports Server (NTRS)

Sander, G. F.

1983-01-01

The performance of an axial vane-type swirler was investigated to aid in computer modeling of gas turbine combustor flowfields and in evaluation of turbulence models for swirling confined jet flow. The swirler studied is annular with a hub-to-swirler diameter ratio of 0.25 and ten adjustable vanes of pitch-to-chord ratio 0.68. Measurements of time-mean axial, radial, and tangential velocities were made at the swirler exit plane using a five-hole pitot probe technique with computer data reduction. Nondimensionalized velocities from both radial and azimuthal traverses are tabulated and plotted for a range of swirl vane angles phi from 0 to 70 degrees. A study was done of idealized exit-plane velocity profiles relating the swirl numbers S and S' to the ratio of maximum swirl and axial velocities for each idealized case, and comparing the idealized swirl numbers with ones calculated from measured profiles.

Numerically Stable Fluid-Structure Interactions Between Compressible Flow and Solid Structures

DTIC Science & Technology

2011-01-28

normal component VrN = ~Vr · ~N and its tangential component ~ VrT = ~Vr − VrN ~N . In order to remain continuous with the effective velocity of the...the interface and thus we can use it directly, giving the final ghost cell velocity ~Vg = VgN ~N + ~ VrT . Once ghost cells are filled, explicit body

Boundary-layer effects in droplet splashing

NASA Astrophysics Data System (ADS)

Riboux, Guillaume; Gordillo, Jose Manuel

2017-11-01

A drop falling onto a solid substrate will disintegrate into smaller parts when its impact velocity exceeds the so called critical velocity for splashing. Under these circumstances, the very thin liquid sheet ejected tangentially to the solid after the drop touches the substrate, lifts off as a consequence of the aerodynamic forces exerted on it and finally breaks into smaller droplets, violently ejected radially outwards, provoking the splash. Here, the tangential deceleration experienced by the fluid entering the thin liquid sheet is investigated making use of boundary layer theory. The velocity component tangent to the solid, computed using potential flow theory provides the far field boundary condition as well as the pressure gradient for the boundary layer equations. The structure of the flow permits to find a self similar solution of the boundary layer equations. This solution is then used to calculate the boundary layer thickness at the root of the lamella as well as the shear stress at the wall. The splash model presented in, which is slightly modified to account for the results obtained from the boundary layer analysis, provides a very good agreement between the measurements and the predicted values of the critical velocity for the splash.

Adjoint-Baed Optimal Control on the Pitch Angle of a Single-Bladed Vertical-Axis Wind Turbine

NASA Astrophysics Data System (ADS)

Tsai, Hsieh-Chen; Colonius, Tim

2017-11-01

Optimal control on the pitch angle of a NACA0018 single-bladed vertical-axis wind turbine (VAWT) is numerically investigated at a low Reynolds number of 1500. With fixed tip-speed ratio, the input power is minimized and mean tangential force is maximized over a specific time horizon. The immersed boundary method is used to simulate the two-dimensional, incompressible flow around a horizontal cross section of the VAWT. The problem is formulated as a PDE constrained optimization problem and an iterative solution is obtained using adjoint-based conjugate gradient methods. By the end of the longest control horizon examined, two controls end up with time-invariant pitch angles of about the same magnitude but with the opposite signs. The results show that both cases lead to a reduction in the input power but not necessarily an enhancement in the mean tangential force. These reductions in input power are due to the removal of a power-damaging phenomenon that occurs when a vortex pair is captured by the blade in the upwind-half region of a cycle. This project was supported by Caltech FLOWE center/Gordon and Betty Moore Foundation.

Purification of Hemoglobin by Tangential Flow Filtration with Diafiltration

PubMed Central

Elmer, Jacob; Harris, David R.; Sun, Guoyong; Palmer, Andre F.

2009-01-01

A recent study by Palmer et al. (2009) demonstrated that tangential flow filtration (TFF) can be used to produce HPLC-grade bovine and human hemoglobin (Hb). In this current study, we assessed the quality of bovine Hb (bHb) purified by introducing a 10 L batch-mode diafiltration step to the previously mentioned TFF Hb purification process. bHb was purified from bovine red blood cells (RBCs) by filtering clarified RBC lysate through 50 nm (stage I) & 500 kDa (stage II) hollow fiber (HF) membranes. The filtrate was then passed through a 100 kDa (stage III) HF membrane with or without an additional 10 L diafiltration step to potentially remove additional small molecular weight impurities. Protein assays, SDS-PAGE, and LC-MS of the purified bHb (stage III retentate) reveal that addition of a diafiltration step has no effect on bHb purity or yield; however, it does increase the methemoglobin level and oxygen affinity of purified bHb. Therefore, we conclude that no additional benefit is gained from diafiltration at stage III and a three-stage TFF process is sufficient to produce HPLC-grade bHb. PMID:19621471

Highly Efficient Large-Scale Lentiviral Vector Concentration by Tandem Tangential Flow Filtration

PubMed Central

Cooper, Aaron R.; Patel, Sanjeet; Senadheera, Shantha; Plath, Kathrin; Kohn, Donald B.; Hollis, Roger P.

2014-01-01

Large-scale lentiviral vector (LV) concentration can be inefficient and time consuming, often involving multiple rounds of filtration and centrifugation. This report describes a simpler method using two tangential flow filtration (TFF) steps to concentrate liter-scale volumes of LV supernatant, achieving in excess of 2000-fold concentration in less than 3 hours with very high recovery (>97%). Large volumes of LV supernatant can be produced easily through the use of multi-layer flasks, each having 1720 cm2 surface area and producing ~560 mL of supernatant per flask. Combining the use of such flasks and TFF greatly simplifies large-scale production of LV. As a demonstration, the method is used to produce a very high titer LV (>1010 TU/mL) and transduce primary human CD34+ hematopoietic stem/progenitor cells at high final vector concentrations with no overt toxicity. A complex LV (STEMCCA) for induced pluripotent stem cell generation is also concentrated from low initial titer and used to transduce and reprogram primary human fibroblasts with no overt toxicity. Additionally, a generalized and simple multiplexed real- time PCR assay is described for lentiviral vector titer and copy number determination. PMID:21784103

Experimental study of oblique impact between dry spheres and liquid layers

NASA Astrophysics Data System (ADS)

Ma, Jiliang; Liu, Daoyin; Chen, Xiaoping

2013-09-01

Liquid addition is common in industrial fluidization-based processes. A detailed understanding of collision mechanics of particles with liquid layers is helpful to optimize these processes. The normal impact with liquid has been studied extensively; however, the studies on oblique impact with liquid are scarce. In this work, experiments are conducted to trace Al2O3 spheres obliquely impacting on a surface covered by liquid layers, in which the free-fall spheres are disturbed initially by a horizontal gas flow. The oblique impact exhibits different rebound behaviors from normal collision due to the occurrence of strong rotation. The normal and tangential restitution coefficients (en and et) and liquid bridge rupture time (trup) are analyzed. With increase in liquid layer thickness and viscosity, en and et decline, and trup increases. With increase in tangential velocity, et decreases first and then increases, whereas en remains nearly unchanged, and trup decreases constantly. A modified Stokes number is proposed to further explore the relation between restitution coefficients and the impact parameters. Finally, an analysis of energy dissipation shows that the contact deformation and liquid phase are the two main sources of total energy dissipation. Unexpectedly, the dissipative energy caused by the liquid phase is independent of tangential velocity.

Effect of Boundary Conditions on Numerically Simulated Tornado-like Vortices.

NASA Astrophysics Data System (ADS)

Smith, David R.

1987-02-01

The boundary conditions for Rotunno's numerical model which simulates tornado-like vortices are examined. In particular, the lateral boundary condition for tangential velocity and the upper boundary condition for radial and tangential velocities are considered to determine if they have any significant impact on vortex development.The choice of the lateral boundary condition did not appear to have any real effect on the development of the vortex over the range of swirl ratios studied (0.87-2.61).The upper boundary conditions attempt to simulate both the presence and absence of the flow-straightening baffle. The boundary condition corresponding to the baffle in place produced a distinct boundary layer in the u and v field and very strong upflow and downflow within the vortex core. When this condition is removed, there is both radial and tangential motion throughout the domain and a reduction of the vertical velocity. At small swirl ratio (S = 0.87) this boundary condition has a profound impact on the narrow vortex, producing changes in the pressure field that intensifies the vortex. At higher swirl ratio the vortex is apparently broad enough to better adjust to the changes of the upper boundary condition and, thus, experiences little change in the development of the vortex.

Flow structure generated by perpendicular blade-vortex interaction and implications for helicopter noise prediction. Volume 1: Measurements

NASA Technical Reports Server (NTRS)

Wittmer, Kenneth S.; Devenport, William J.

1996-01-01

The perpendicular interaction of a streamwise vortex with an infinite span helicopter blade was modeled experimentally in incompressible flow. Three-component velocity and turbulence measurements were made using a sub-miniature four sensor hot-wire probe. Vortex core parameters (radius, peak tangential velocity, circulation, and centerline axial velocity deficit) were determined as functions of blade-vortex separation, streamwise position, blade angle of attack, vortex strength, and vortex size. The downstream development of the flow shows that the interaction of the vortex with the blade wake is the primary cause of the changes in the core parameters. The blade sheds negative vorticity into its wake as a result of the induced angle of attack generated by the passing vortex. Instability in the vortex core due to its interaction with this negative vorticity region appears to be the catalyst for the magnification of the size and intensity of the turbulent flowfield downstream of the interaction. In general, the core radius increases while peak tangential velocity decreases with the effect being greater for smaller separations. These effects are largely independent of blade angle of attack; and if these parameters are normalized on their undisturbed values, then the effects of the vortex strength appear much weaker. Two theoretical models were developed to aid in extending the results to other flow conditions. An empirical model was developed for core parameter prediction which has some rudimentary physical basis, implying usefulness beyond a simple curve fit. An inviscid flow model was also created to estimate the vorticity shed by the interaction blade, and to predict the early stages of its incorporation into the interacting vortex.

Turbulent swirling jets with excitation

NASA Technical Reports Server (NTRS)

Taghavi, Rahmat; Farokhi, Saeed

1988-01-01

An existing cold-jet facility at NASA Lewis Research Center was modified to produce swirling flows with controllable initial tangential velocity distribution. Two extreme swirl profiles, i.e., one with solid-body rotation and the other predominated by a free-vortex distribution, were produced at identical swirl number of 0.48. Mean centerline velocity decay characteristics of the solid-body rotation jet flow exhibited classical decay features of a swirling jet with S - 0.48 reported in the literature. However, the predominantly free-vortex distribution case was on the verge of vortex breakdown, a phenomenon associated with the rotating flows of significantly higher swirl numbers, i.e., S sub crit greater than or equal to 0.06. This remarkable result leads to the conclusion that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field. The relative size (i.e., diameter) of the vortex core emerging from the nozzle and the corresponding tangential velocity distribution are also controlling factors. Excitability of swirling jets is also investigated by exciting a flow with a swirl number of 0.35 by plane acoustic waves at a constant sound pressure level and at various frequencies. It is observed that the cold swirling jet is excitable by plane waves, and that the instability waves grow about 50 percent less in peak r.m.s. amplitude and saturate further upstream compared to corresponding waves in a jet without swirl having the same axial mass flux. The preferred Strouhal number based on the mass-averaged axial velocity and nozzle exit diameter for both swirling and nonswirling flows is 0.4.

Effects of simulated artificial gravity on human performance

NASA Technical Reports Server (NTRS)

Green, J. A.; Peacock, J. L.

1972-01-01

The ability of test subjects to perform operational type tasks was evaluated at rotational rates to 6 rpm and radii to 78 ft (24 m). The tasks included fine motor activity, mental operations, postural equilibrium, cargo handling, radial and tangential locomotion. Performance data indicate that 6 rpm presents a physiological limit at radii to 75 ft (23 m). Radial locomotion was not found to produce excessive adverse stimuli, and tangential locomotion was readily accomplished at walking rates of 2 of 4.8 ft/s (.6 to 1.4 m/s). The absence of vision dramatically reduced an individual's postural equilibrium during rotation. The use of selected anti-motion pharmaceuticals had, generally, a positive effect upon psychomotor performance at 6 rpm, but did not prove to be a panacea for the adverse effects of rotation at this rate.

Quasi-steady vortical structures in vertically vibrating soap films

NASA Astrophysics Data System (ADS)

Vega, José M.; Higuera, F. J.; Weidman, P. D.

1998-10-01

An analysis of the quasi-steady streaming of the liquid in a vertically vibrated horizontal soap film is reported. The air around the soap film is seen to play a variety of roles: it transmits normal and tangential oscillatory stresses to the film, damps out Marangoni waves, and forces non-oscillatory deflection of the film and tangential motion of the liquid. Non-oscillatory volume forcing originating inside the liquid is also analysed. This forcing dominates the quasi-steady streaming when the excitation frequency is close to the eigenfrequency of a Marangoni mode of the soap film, while both volume forcing in the liquid and surface forcing of the gas on the liquid are important when no Marangoni mode resonates. Different manners by which the combined forcings can induce quasi-steady streaming motion are discussed and some numerical simulations of the quasi-steady liquid flow are presented.

Development of a defect stream function, law of the wall/wake method for compressible turbulent boundary layers. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Wahls, Richard A.

1990-01-01

The method presented is designed to improve the accuracy and computational efficiency of existing numerical methods for the solution of flows with compressible turbulent boundary layers. A compressible defect stream function formulation of the governing equations assuming an arbitrary turbulence model is derived. This formulation is advantageous because it has a constrained zero-order approximation with respect to the wall shear stress and the tangential momentum equation has a first integral. Previous problems with this type of formulation near the wall are eliminated by using empirically based analytic expressions to define the flow near the wall. The van Driest law of the wall for velocity and the modified Crocco temperature-velocity relationship are used. The associated compressible law of the wake is determined and it extends the valid range of the analytical expressions beyond the logarithmic region of the boundary layer. The need for an inner-region eddy viscosity model is completely avoided. The near-wall analytic expressions are patched to numerically computed outer region solutions at a point determined during the computation. A new boundary condition on the normal derivative of the tangential velocity at the surface is presented; this condition replaces the no-slip condition and enables numerical integration to the surface with a relatively coarse grid using only an outer region turbulence model. The method was evaluated for incompressible and compressible equilibrium flows and was implemented into an existing Navier-Stokes code using the assumption of local equilibrium flow with respect to the patching. The method has proven to be accurate and efficient.

Navier-Stokes flowfield computation of wing/rotor interaction for a tilt rotor aircraft in hover

NASA Technical Reports Server (NTRS)

Fejtek, Ian G.

1993-01-01

The download on the wing produced by the rotor-induced downwash of a tilt rotor aircraft in hover is of major concern because of its severe impact on payload-carrying capability. A method has been developed to help gain a better understanding of the fundamental fluid dynamics that causes this download, and to help find ways to reduce it. In particular, the method is employed in this work to analyze the effect of a tangential leading edge circulation-control jet on download reduction. Because of the complexities associated with modeling the complete configuration, this work focuses specifically on the wing/rotor interaction of a tilt rotor aircraft in hover. The three-dimensional, unsteady, thin-layer compressible Navier-Stokes equations are solved using a time-accurate, implicit, finite difference scheme that employs LU-ADI factorization. The rotor is modeled as an actuator disk which imparts both a radical and an azimuthal distribution of pressure rise and swirl to the flowfield. A momentum theory blade element analysis of the rotor is incorporated into the Navier-Stokes solution method. Solution blanking at interior points of the mesh has been shown here to be an effective technique in introducing the effects of the rotor and tangential leading edge jet. Results are presented both for a rotor alone and for wing/rotor interaction. The overall mean characteristics of the rotor flowfield are computed including the flow acceleration through the rotor disk, the axial and swirl velocities in the rotor downwash, and the slipstream contraction. Many of the complex tilt rotor flow features are captured including the highly three-dimensional flow over the wing, the recirculation fountain at the plane of symmetry, wing leading and trailing edge separation, and the large region of separated flow beneath the wing. Mean wing surface pressures compare fairly well with available experimental data, but the time-averaged download/thrust ratio is 20-30 percent higher than the measured value. The discrepancy is due to a combination of factors that are discussed. Leading edge tangential blowing, of constant strength along the wing span, is shown to be effective in reducing download. The jet serves primarily to reduce the pressure on the wing upper surface. The computation clearly shows that, because of the three-dimensionality of the flowfield, optimum blowing would involve a spanwise variation in blowing strength.

Inverse design of centrifugal compressor vaned diffusers in inlet shear flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zangeneh, M.

1996-04-01

A three-dimensional inverse design method in which the blade (or vane) geometry is designed for specified distributions of circulation and blade thickness is applied to the design of centrifugal compressor vaned diffusers. Two generic diffusers are designed, one with uniform inlet flow (equivalent to a conventional design) and the other with a sheared inlet flow. The inlet shear flow effects are modeled in the design method by using the so-called ``Secondary Flow Approximation`` in which the Bernoulli surfaces are convected by the tangentially mean inviscid flow field. The difference between the vane geometry of the uniform inlet flow and nonuniformmore » inlet flow diffusers is found to be most significant from 50 percent chord to the trailing edge region. The flows through both diffusers are computed by using Denton`s three-dimensional inviscid Euler solver and Dawes` three-dimensional Navier-Stokes solver under sheared in-flow conditions. The predictions indicate improved pressure recovery and internal flow field for the diffuser designed for shear inlet flow conditions.« less

Nature of Fluctuations on Directional Discontinuities Inside a Solar Ejection: Wind and IMP 8 Observations

NASA Technical Reports Server (NTRS)

Vasquez, Bernard J.; Farrugia, Charles J.; Markovskii, Sergei A.; Hollweg, Joseph V.; Richardson, Ian G.; Ogilvie, Keith W.; Lepping, Ronald P.; Lin, Robert P.; Larson, Davin; White, Nicholas E. (Technical Monitor)

2001-01-01

A solar ejection passed the Wind spacecraft between December 23 and 26, 1996. On closer examination, we find a sequence of ejecta material, as identified by abnormally low proton temperatures, separated by plasmas with typical solar wind temperatures at 1 AU. Large and abrupt changes in field and plasma properties occurred near the separation boundaries of these regions. At the one boundary we examine here, a series of directional discontinuities was observed. We argue that Alfvenic fluctuations in the immediate vicinity of these discontinuities distort minimum variance normals, introducing uncertainty into the identification of the discontinuities as either rotational or tangential. Carrying out a series of tests on plasma and field data including minimum variance, velocity and magnetic field correlations, and jump conditions, we conclude that the discontinuities are tangential. Furthermore, we find waves superposed on these tangential discontinuities (TDs). The presence of discontinuities allows the existence of both surface waves and ducted body waves. Both probably form in the solar atmosphere where many transverse nonuniformities exist and where theoretically they have been expected. We add to prior speculation that waves on discontinuities may in fact be a common occurrence. In the solar wind, these waves can attain large amplitudes and low frequencies. We argue that such waves can generate dynamical changes at TDs through advection or forced reconnection. The dynamics might so extensively alter the internal structure that the discontinuity would no longer be identified as tangential. Such processes could help explain why the occurrence frequency of TDs observed throughout the solar wind falls off with increasing heliocentric distance. The presence of waves may also alter the nature of the interactions of TDs with the Earth's bow shock in so-called hot flow anomalies.

Angled injection: Hybrid fluid film bearings for cryogenic applications

NASA Technical Reports Server (NTRS)

SanAndres, Luis

1995-01-01

A computational bulk-flow analysis for prediction of the force coefficients of hybrid fluid film bearings with angled orifice injection is presented. Past measurements on water-lubricated hybrid bearings with angle orifice injection have demonstrated improved rotordynamic performance with virtual elimination of cross-coupled stiffness coefficients and nul or negative whirl frequency ratios. A simple analysis reveals that the fluid momentum exchange at the orifice discharge produces a pressure rise in the recess which retards the shear flow induced by journal rotation, and consequently, reduces cross-coupling forces. The predictions from the model correlate well with experimental measurements from a radial and 45 deg angled orifice injection, five recess water hybrid bearings (C = 125 microns) operating at 10.2, 17.4, and 24.6 krpm and with nominal supply pressures equal to 4, 5.5, and 7 MPa. An application example for a liquid oxygen six recess/pad hybrid journal bearing shows the advantages of tangential orifice injection on the rotordynamic force coefficients and stability indicator for forward whirl motions and without performance degradation on direct stiffness and damping coefficients. The computer program generated, 'hydrojet,' extends and complements previously developed codes.

Automation and Intensity Modulated Radiation Therapy for Individualized High-Quality Tangent Breast Treatment Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purdie, Thomas G., E-mail: Tom.Purdie@rmp.uhn.on.ca; Department of Radiation Oncology, University of Toronto, Toronto, Ontario; Techna Institute, University Health Network, Toronto, Ontario

Purpose: To demonstrate the large-scale clinical implementation and performance of an automated treatment planning methodology for tangential breast intensity modulated radiation therapy (IMRT). Methods and Materials: Automated planning was used to prospectively plan tangential breast IMRT treatment for 1661 patients between June 2009 and November 2012. The automated planning method emulates the manual steps performed by the user during treatment planning, including anatomical segmentation, beam placement, optimization, dose calculation, and plan documentation. The user specifies clinical requirements of the plan to be generated through a user interface embedded in the planning system. The automated method uses heuristic algorithms to definemore » and simplify the technical aspects of the treatment planning process. Results: Automated planning was used in 1661 of 1708 patients receiving tangential breast IMRT during the time interval studied. Therefore, automated planning was applicable in greater than 97% of cases. The time for treatment planning using the automated process is routinely 5 to 6 minutes on standard commercially available planning hardware. We have shown a consistent reduction in plan rejections from plan reviews through the standard quality control process or weekly quality review multidisciplinary breast rounds as we have automated the planning process for tangential breast IMRT. Clinical plan acceptance increased from 97.3% using our previous semiautomated inverse method to 98.9% using the fully automated method. Conclusions: Automation has become the routine standard method for treatment planning of tangential breast IMRT at our institution and is clinically feasible on a large scale. The method has wide clinical applicability and can add tremendous efficiency, standardization, and quality to the current treatment planning process. The use of automated methods can allow centers to more rapidly adopt IMRT and enhance access to the documented improvements in care for breast cancer patients, using technologies that are widely available and already in clinical use.« less

Automation and intensity modulated radiation therapy for individualized high-quality tangent breast treatment plans.

PubMed

Purdie, Thomas G; Dinniwell, Robert E; Fyles, Anthony; Sharpe, Michael B

2014-11-01

To demonstrate the large-scale clinical implementation and performance of an automated treatment planning methodology for tangential breast intensity modulated radiation therapy (IMRT). Automated planning was used to prospectively plan tangential breast IMRT treatment for 1661 patients between June 2009 and November 2012. The automated planning method emulates the manual steps performed by the user during treatment planning, including anatomical segmentation, beam placement, optimization, dose calculation, and plan documentation. The user specifies clinical requirements of the plan to be generated through a user interface embedded in the planning system. The automated method uses heuristic algorithms to define and simplify the technical aspects of the treatment planning process. Automated planning was used in 1661 of 1708 patients receiving tangential breast IMRT during the time interval studied. Therefore, automated planning was applicable in greater than 97% of cases. The time for treatment planning using the automated process is routinely 5 to 6 minutes on standard commercially available planning hardware. We have shown a consistent reduction in plan rejections from plan reviews through the standard quality control process or weekly quality review multidisciplinary breast rounds as we have automated the planning process for tangential breast IMRT. Clinical plan acceptance increased from 97.3% using our previous semiautomated inverse method to 98.9% using the fully automated method. Automation has become the routine standard method for treatment planning of tangential breast IMRT at our institution and is clinically feasible on a large scale. The method has wide clinical applicability and can add tremendous efficiency, standardization, and quality to the current treatment planning process. The use of automated methods can allow centers to more rapidly adopt IMRT and enhance access to the documented improvements in care for breast cancer patients, using technologies that are widely available and already in clinical use. Copyright © 2014 Elsevier Inc. All rights reserved.

DESIGN ANALYSIS OF RADIAL INFLOW TURBINES

NASA Technical Reports Server (NTRS)

Glassman, A. J.

1994-01-01

This program performs a velocity-diagram analysis required for determining geometry and estimating performance for radial-inflow turbines. Input design requirements are power, mass flow rate, inlet temperature and pressure, and rotative rate. The design variables include stator-exit angle, rotor-exit-tip to rotor-inlet radius ratio, rotor-exit-hub to tip radius ratio, and the magnitude and radial distribution of rotor-exit tangential velocity. The program output includes diameters, total and static efficiences, all absolute and relative temperatures, pressures, and velocities, and flow angles at stator inlet, stator exit, rotor inlet, and rotor exit. Losses accounted for in this program by the internal loss model are three-dimensional (profile plus end wall) viscous losses in the stator and the rotor, the disk-friction loss on the back side of the rotor, the loss due to the clearance between the rotor tip and the outer casing, and the exit velocity loss. The flow analysis is one-dimensional at the stator inlet, stator exit, and rotor inlet, each of these calculation stations being at a constant radius. At the rotor exit where there is a variation in flow-field radius, an axisymmetric two-dimensional analysis is made using constant height sectors. Simple radial equilibrium is used to establish the static pressure gradient at the rotor exit. This program is written in FORTRAN V and has been implemented on a UNIVAC 1100 series computer with a memory requirement of approximately 22K of 36 bit words.

CFD study of some factors affecting performance of HAWT with swept blades

NASA Astrophysics Data System (ADS)

Khalafallah, M. G.; Ahmed, A. M.; Emam, M. K.

2017-05-01

Most modern high-power wind turbines are horizontal axis type with straight twisted blades. Upgrading power and performance of these turbines is considered a challenge. A recent trend towards improving the horizontal axis wind turbine (HAWT) performance is to use swept blades or sweep twist adaptive blades. In the present work, the effect of blade curvature, sweep starting point and sweep direction on the wind turbine performance was investigated. The CFD simulation method was validated against available experimental data of a 0.9 m diameter HAWT. The wind turbine power and thrust coefficients at different tip speed ratios were calculated. Flow field, pressure distribution and local tangential and streamwise forces were also analysed. The results show that the downstream swept blade has the highest Cp value at design point as compared with the straight blade profile. However, the improvement in power coefficient is accompanied by a thrust increase. Results also show that the best performance is obtained when the starting blade sweeps at 25% of blade radius for different directions of sweep.

The Production, Purification and Properties of the Biopolymer Levan Produced by the Bacterium Erwinia Herbicola

DTIC Science & Technology

1989-08-01

standard and an inulin standard provided by Dr. Elwin Reese of this laboratory and a sample of levan from a different bacterium provided by the USDA.23 A...polymyxa 24 Levan standard Continuous culture Tangential Flow purified levan (this study) >■• <-■-’•«■ i-I-» r Inulin standard tu 25 Figure 5. NMR

Exact solutions for layered thermocapillary convection of a viscous incompressible fluid with specified stresses on the bottom

NASA Astrophysics Data System (ADS)

Prosviryakov, E. Yu.; Spevak, L. F.

2017-12-01

A new exact solution of the Oberbeck-Boussinesq system is found. The Marangoni thermocapillary convection in an infinite fluid layer is described. It is demonstrated that the specification of tangential stresses at both boundaries of the layered velocity field is nonstationary. Velocities describe a superposition of unidirectional flows with an intermediate time interval when there are counterflows.

Comparison of the Effect of Horizontal Vibrations on Interfacial Waves in a Two-Layer System of Inviscid Liquids to Effective Gravity Inversion

NASA Astrophysics Data System (ADS)

Pimenova, Anastasiya V.; Goldobin, Denis S.; Lyubimova, Tatyana P.

2018-02-01

We study the waves at the interface between two thin horizontal layers of immiscible liquids subject to high-frequency tangential vibrations. Nonlinear governing equations are derived for the cases of two- and three-dimensional flows and arbitrary ratio of layer thicknesses. The derivation is performed within the framework of the long-wavelength approximation, which is relevant as the linear instability of a thin-layers system is long-wavelength. The dynamics of equations is integrable and the equations themselves can be compared to the Boussinesq equation for the gravity waves in shallow water, which allows one to compare the action of the vibrational field to the action of the gravity and its possible effective inversion.

Size distribution of absorbing and fluorescing DOM in Beaufort Sea, Canada Basin

NASA Astrophysics Data System (ADS)

Gao, Zhiyuan; Guéguen, Céline

2017-03-01

The molecular weight (MW) of dissolved organic matter (DOM) is considered as an important factor affecting the bioavailability of organic matter and associated chemical species. Colored DOM (CDOM) MW distribution was determined, for the first time, in the Beaufort Sea (Canada Basin) by asymmetrical flow field-flow fractionation (AF4) coupled with online diode array ultra violet-visible photometer and offline fluorescence detectors. The apparent MW ranged from 1.07 to 1.45 kDa, congruent with previous studies using high performance size exclusion chromatography and tangential flow filtration. Interestingly, a minimum in MW was associated with the Pacific Summer Waters (PSW), while higher MW was associated with the Pacific Winter Waters (PWW). The Arctic Intermediate Waters (AIW) did not show any significant change in MW and fluorescence intensities distribution between stations, suggesting homogeneous DOM composition in deep waters. Three fluorescence components including two humic-like components and one protein-like component were PARAFAC-validated. With the increase of MW, protein-like fluorescence component became more dominant while the majority remained as marine/microbially derived humic-like components. Overall, it is concluded that water mass origin influenced DOM MW distribution in the Arctic Ocean.

Spin State Equilibria of Asteroids due to YORP Effects

NASA Astrophysics Data System (ADS)

Golubov, Oleksiy; Scheeres, Daniel J.; Lipatova, Veronika

2016-05-01

Spins of small asteroids are controlled by the Yarkovsky--O'Keefe--Radzievskii--Paddack (YORP) effect. The normal version of this effect has two components: the axial component alters the rotation rate, while the obliquity component alters the obliquity. Under this model the rotation state of an asteroid can be described in a phase plane with the rotation rate along the polar radius and the obliquity as the polar angle. The YORP effect induces a phase flow in this plane, which determines the distribution of asteroid rotation rates and obliquities.We study the properties of this phase flow for several typical cases. Some phase flows have stable attractors, while in others all trajectories go to very small or large rotation rates. In the simplest case of zero thermal inertia approximate analytical solutions to dynamics equations are possible. Including thermal inertia and the Tangential YORP effect makes the possible evolutionary scenarios much more diverse. We study possible evolution paths and classify the most general trends. Also we discuss possible implications for the distribution of asteroid rotation rates and obliquities.A special emphasis is put on asteroid (25143) Itokawa, whose shape model is well determined, but who's measured YORP acceleration does not agree with the predictions of normal YORP. We show that Itokawa's rotational state can be explained by the presence of tangential YORP and that it may be in or close to a stable spin state equilibrium. The implications of such states will be discussed.

Aerodynamic control of NASP-type vehicles through Vortex manipulation. Volume 1: Static water tunnel tests

NASA Technical Reports Server (NTRS)

Suarez, Carlos J.; Ng, T. Terry; Ong, Lih-Yenn; Malcolm, Gerald N.

1993-01-01

Water tunnel tests were conducted on a NASP-type configuration to evaluate different pneumatic Forebody Vortex Control (FVC) methods. Flow visualization and yawing moment measurements were performed at angles of attack from 0 deg to 30 deg. The pneumatic techniques tested included jet and slot blowing. In general, blowing can be used efficiently to manipulate the forebody vortices at angles of attack greater than 20 deg. These vortices are naturally symmetric up to alpha = 25 deg and asymmetric between 25 deg and 30 deg angle of attack. Results indicate that tangential aft jet blowing is the most promising method for this configuration. Aft jet blowing produces a yawing moment towards the blowing side and the trends with blowing rate are well behaved. The size of the nozzle is not the dominant factor in the blowing process; the change in the blowing 'momentum,' i.e., the product of the mass flow rate and the velocity of the jet, appears to be the important parameter in the water tunnel (incompressible and unchoked flow at the nozzle exit). Forward jet blowing is very unpredictable and sensitive to mass flow rate changes. Slot blowing (with the exception of very low blowing rates) acts as a flow 'separator'; it promotes early separation on the blow side, producing a yawing moment toward the non-blowing side for the C(sub mu) range investigated.

Numerical study of nonequilibrium gas flow in a microchannel with a ratchet surface.

PubMed

Zhu, Lianhua; Guo, Zhaoli

2017-02-01

The nonequilibrium gas flow in a two-dimensional microchannel with a ratchet surface and a moving wall is investigated numerically with a kinetic method [Guo et al., Phys. Rev. E 91, 033313 (2015)]PLEEE81539-375510.1103/PhysRevE.91.033313. The presence of periodic asymmetrical ratchet structures on the bottom wall of the channel and the temperature difference between the walls of the channel result in a thermally induced flow, and hence a tangential propelling force on the wall. Such thermally induced propelling mechanism can be utilized as a model heat engine. In this article, the relations between the propelling force and the top wall moving velocity are obtained by solving the Boltzmann equation with the Shakhov model deterministically in a wide range of Knudsen numbers. The flow fields at both the static wall state and the critical state at which the thermally induced force cancels the drag force due to the active motion of the top wall are analyzed. A counterintuitive relation between the flow direction and the shear force is observed in the highly rarefied condition. The output power and thermal efficiency of the system working as a model heat engine are analyzed based on the momentum and energy transfer between the walls. The effects of Knudsen number, temperature difference, and geometric configurations are investigated. Guidance for improving the mechanical performance is discussed.

Local time asymmetry of Saturn's magnetosheath flows

NASA Astrophysics Data System (ADS)

Burkholder, B.; Delamere, P. A.; Ma, X.; Thomsen, M. F.; Wilson, R. J.; Bagenal, F.

2017-06-01

Using gross averages of the azimuthal component of flow in Saturn's magnetosheath, we find that flows in the prenoon sector reach a maximum value of roughly half that of the postnoon side. Corotational magnetodisc plasma creates a much larger flow shear with solar wind plasma prenoon than postnoon. Maxwell stress tensor analysis shows that momentum can be transferred out of the magnetosphere along tangential field lines if a normal component to the boundary is present, i.e., field lines which pierce the magnetopause. A Kelvin-Helmholtz unstable flow gives rise to precisely this situation, as intermittent reconnection allows the magnetic field to thread the boundary. We interpret the Kelvin-Helmholtz instability acting along the magnetopause as a tangetial drag, facilitating two-way transport of momentum through the boundary. We use reduced magnetosheath flows in the dawn sector as evidence of the importance of this interaction in Saturn's magnetosphere.

Design and Experimental Study on Spinning Solid Rocket Motor

NASA Astrophysics Data System (ADS)

Xue, Heng; Jiang, Chunlan; Wang, Zaicheng

The study on spinning solid rocket motor (SRM) which used as power plant of twice throwing structure of aerial submunition was introduced. This kind of SRM which with the structure of tangential multi-nozzle consists of a combustion chamber, propellant charge, 4 tangential nozzles, ignition device, etc. Grain design, structure design and prediction of interior ballistic performance were described, and problem which need mainly considered in design were analyzed comprehensively. Finally, in order to research working performance of the SRM, measure pressure-time curve and its speed, static test and dynamic test were conducted respectively. And then calculated values and experimental data were compared and analyzed. The results indicate that the designed motor operates normally, and the stable performance of interior ballistic meet demands. And experimental results have the guidance meaning for the pre-research design of SRM.

Flow fields behind a variable-area nozzle for radial turbines

NASA Astrophysics Data System (ADS)

Hayami, Hiroshi; Hyun, Yong-Ik; Senoo, Yasutoshi; Yamaguchi, Michiteru

The flow fields behind a variable-area nozzle for radial turbines were measured in detail using a three-hole cobra probe in 15 cases, which are a combination of three nozzle throat areas (0.8, 1.0, and 1.4 times the rated area) and five values of the tip-clearance to blade-height ratio (between 0.0 to 0.099). The flow fields at different tip clearances are presented in contour maps, and the pitch mean values are discussed as spanwise distributions of total pressure loss, flow angle, and radial and tangential velocity components. It is shown that the intensity of swirl behind the nozzle is decreased and the pressure loss is increased with the tip clearance, and the effect is magnified as the blade loading is higher.

Detailed flow measurements in a centrifugal compressor vaneless diffuser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinarbasi, A.; Johnson, M.W.

1994-07-01

Hot-wire anemometer measurements have been made in the vaneless diffuser of a 1-m-dia low-speed backswept centrifugal compressor using a phase lock loop technique. Radial, tangential, and axial velocity measurements have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wake flow pattern and the blade wakes. The passage wake is located on the shroud side of the diffuser and mixes out slowly as the flow moves through the diffuser. The blade wakes, on the other hand, distort and mix out rapidly in the diffuser. Contours of turbulent kinetic energymore » are also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced.« less

On chemical reaction and porous medium effect in the MHD flow due to a rotating disk with variable thickness

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Nazar, Hira; Imtiaz, Maria; Alsaedi, Ahmed

2017-06-01

The present analysis describes the magnetohydrodynamic (MHD) axisymmetric flow of a viscous fluid due to a rotating disk with variable thickness. An electrically conducting fluid fills the porous space. The first-order chemical reaction is considered. The equations of the present problem representing the flow of a fluid are reduced into nonlinear ordinary differential equations. Convergent series solutions are obtained. The impacts of the various involved dimensionless parameters on fluid flow, temperature, concentration, skin frction coefficient and Nusselt number are examined. The radial, tangential and axial components of velocity are affected in a similar manner on changing the thickness coefficient of the disk. Similar effects of the disk thickness coefficient are observed for both the temperature and concentration profile.

Properties of Tangential and Cyclic Polygons: An Application of Circulant Matrices

ERIC Educational Resources Information Center

Leung, Allen; Lopez-Real, Francis

2003-01-01

In this paper, the properties of tangential and cyclic polygons proposed by Lopez-Real are proved rigorously using the theory of circulant matrices. In particular, the concepts of slippable tangential polygons and conformable cyclic polygons are defined. It is shown that an n-sided tangential (or cyclic) polygon P[subscript n] with n even is…

Unstable force analysis for induction motor eccentricity

NASA Astrophysics Data System (ADS)

Han, Xu; Palazzolo, Alan

2016-05-01

The increasing popularity of motors in machinery trains has led to an intensified interest in the forces they produce that may influence machinery vibration. Motor design typically assumes a uniform air gap, however in practice all motors operate with the rotor slightly displaced from the motor centerline in what is referred to as an eccentric position. Rotor center eccentricity can cause a radially unbalanced magnetic field when the motor is operating. This will results in both a radial force pulling the motor further away from the center, and a tangential force which can induce a vibration stability problem. In this paper, a magnetic equivalent circuit MEC modeling method is proposed to calculate both the radial and tangential motor eccentric force. The treatment of tangential force determination is rarely addressed, but it is very important for rotordynamic vibration stability evaluation. The proposed model is also coupled with the motor electric circuit model to provide capability for transient vibration simulations. FEM is used to verify the MEC model. A parametric study is performed on the motor radial and tangential eccentric forces. Also a Jeffcott rotor model is used to study the influence of the motor eccentric force on mechanical vibration stability and nonlinear behavior. Furthermore, a stability criteria for the bearing damping is provided. The motor radial and tangential eccentric forces are both curved fitted to include their nonlinearity in time domain transient simulation for both a Jeffcott rotor model and a geared machinery train with coupled torsional-lateral motion. Nonlinear motions are observed, including limit cycles and bifurcation induced vibration amplitude jumps.

Comparison of 2 ultrafiltration systems for the concentration of seeded viruses from environmental waters.

PubMed

Olszewski, John; Winona, Linda; Oshima, Kevin H

2005-04-01

The use of ultrafiltration as a concentration method to recover viruses from environmental waters was investigated. Two ultrafiltration systems (hollow fiber and tangential flow) in a large- (100 L) and small-scale (2 L) configuration were able to recover greater than 50% of multiple viruses (bacteriophage PP7 and T1 and poliovirus type 2) from varying water turbidities (10-157 nephelometric turbidity units (NTU)) simultaneously. Mean recoveries (n = 3) in ground and surface water by the large-scale hollow fiber ultrafiltration system (100 L) were comparable to recoveries observed in the small-scale system (2 L). Recovery of seeded viruses in highly turbid waters from small-scale tangential flow (2 L) (screen and open channel) and hollow fiber ultrafilters (2 L) (small pilot) were greater than 70%. Clogging occurred in the hollow fiber pencil module and when particulate concentrations exceeded 1.6 g/L and 5.5 g/L (dry mass) in the screen and open channel filters, respectively. The small pilot module was able to filter all concentrates without clogging. The small pilot hollow fiber ultrafilter was used to test recovery of seeded viruses from surface waters from different geographical regions in 10-L volumes. Recoveries >70% were observed from all locations.

High-pressure size exclusion chromatography analysis of dissolved organic matter isolated by tangential-flow ultra filtration

USGS Publications Warehouse

Everett, C.R.; Chin, Y.-P.; Aiken, G.R.

1999-01-01

A 1,000-Dalton tangential-flow ultrafiltration (TFUF) membrane was used to isolate dissolved organic matter (DOM) from several freshwater environments. The TFUF unit used in this study was able to completely retain a polystyrene sulfonate 1,800-Dalton standard. Unaltered and TFUF-fractionated DOM molecular weights were assayed by high-pressure size exclusion chromatography (HPSEC). The weight-averaged molecular weights of the retentates were larger than those of the raw water samples, whereas the filtrates were all significantly smaller and approximately the same size or smaller than the manufacturer-specified pore size of the membrane. Moreover, at 280 nm the molar absorptivity of the DOM retained by the ultrafilter is significantly larger than the material in the filtrate. This observation suggests that most of the chromophoric components are associated with the higher molecular weight fraction of the DOM pool. Multivalent metals in the aqueous matrix also affected the molecular weights of the DOM molecules. Typically, proton-exchanged DOM retentates were smaller than untreated samples. This TFUF system appears to be an effective means of isolating aquatic DOM by size, but the ultimate size of the retentates may be affected by the presence of metals and by configurational properties unique to the DOM phase.

Aerodynamic and torque characteristics of enclosed Co/counter rotating disks

NASA Astrophysics Data System (ADS)

Daniels, W. A.; Johnson, B. V.; Graber, D. J.

1989-06-01

Experiments were conducted to determine the aerodynamic and torque characteristics of adjacent rotating disks enclosed in a shroud, in order to obtain an extended data base for advanced turbine designs such as the counterrotating turbine. Torque measurements were obtained on both disks in the rotating frame of reference for corotating, counterrotating and one-rotating/one-static disk conditions. The disk models used in the experiments included disks with typical smooth turbine geometry, disks with bolts, disks with bolts and partial bolt covers, and flat disks. A windage diaphragm was installed at mid-cavity for some experiments. The experiments were conducted with various amounts of coolant throughflow injected into the disk cavity from the disk hub or from the disk OD with swirl. The experiments were conducted at disk tangential Reynolds number up to 1.6 x 10 to the 7th with air as the working fluid. The results of this investigation indicated that the static shroud contributes a significant amount to the total friction within the disk system; the torque on counterrotating disks is essentially independent of coolant flow total rate, flow direction, and tangential Reynolds number over the range of conditions tested; and a static windage diaphragm reduces disk friction in counterrotating disk systems.

Experimental investigation of the hydrodynamic forces on the shroud of a centrifugal pump impeller. Thesis

NASA Technical Reports Server (NTRS)

Zhuang, Fei

1989-01-01

Fluid-induced forces acting on a rotating impeller are known to cause rotor-dynamic problems in turbomachines. The forces generated by leakage flow along the front shroud surface of a centrifugal turbomachine impeller play an important role among these fluid-induced forces. The present research was aimed to gain a better understanding of these shroud forces. An experimental apparatus was designed and constructed to simulate the impeller shroud leakage flow. Hydrodynamic forces and steady and unsteady pressure distributions on the rotating shroud were measured as functions of eccentricity, width of shroud clearance, face seal clearance and shaft rotating speed. The forces measured from the dynamometer and manometers agreed well. The hydrodynamic force matrices were found skew-symmetric and statically unstable. This is qualitatively similar to the result of previous hydrodynamic volute force measurements. Nondimensionalized normal and tangential forces decrease slightly as Reynolds number increases. As the width of the shroud clearance decreases and/or the eccentricity increases, the hydrodynamic forces increase nonlinearly. There was some evidence found that increased front seal clearance could reduce the radial shroud forces and the relative magnitude of the destabilizing tangential force. Subharmonic pressure fluctuations were also observed which may adversely affect the behavior of the rotor system.

Single pass tangential flow filtration to debottleneck downstream processing for therapeutic antibody production.

PubMed

Dizon-Maspat, Jemelle; Bourret, Justin; D'Agostini, Anna; Li, Feng

2012-04-01

As the therapeutic monoclonal antibody (mAb) market continues to grow, optimizing production processes is becoming more critical in improving efficiencies and reducing cost-of-goods in large-scale production. With the recent trends of increasing cell culture titers from upstream process improvements, downstream capacity has become the bottleneck in many existing manufacturing facilities. Single Pass Tangential Flow Filtration (SPTFF) is an emerging technology, which is potentially useful in debottlenecking downstream capacity, especially when the pool tank size is a limiting factor. It can be integrated as part of an existing purification process, after a column chromatography step or a filtration step, without introducing a new unit operation. In this study, SPTFF technology was systematically evaluated for reducing process intermediate volumes from 2× to 10× with multiple mAbs and the impact of SPTFF on product quality, and process yield was analyzed. Finally, the potential fit into the typical 3-column industry platform antibody purification process and its implementation in a commercial scale manufacturing facility were also evaluated. Our data indicate that using SPTFF to concentrate protein pools is a simple, flexible, and robust operation, which can be implemented at various scales to improve antibody purification process capacity. Copyright © 2011 Wiley Periodicals, Inc.

Purification of monoclonal antibodies from clarified cell culture fluid using Protein A capture continuous countercurrent tangential chromatography

PubMed Central

Dutta, Amit K.; Tran, Travis; Napadensky, Boris; Teella, Achyuta; Brookhart, Gary; Ropp, Philip A.; Zhang, Ada W.; Tustian, Andrew D.; Zydney, Andrew L.; Shinkazh, Oleg

2015-01-01

Recent studies using simple model systems have demonstrated that Continuous Countercurrent Tangential Chromatography (CCTC) has the potential to overcome many of the limitations of conventional Protein A chromatography using packed columns. The objective of this work was to optimize and implement a CCTC system for monoclonal antibody purification from clarified Chinese Hamster Ovary (CHO) cell culture fluid using a commercial Protein A resin. Several improvements were introduced to the previous CCTC system including the use of retentate pumps to maintain stable resin concentrations in the flowing slurry, the elimination of a slurry holding tank to improve productivity, and the introduction of an “after binder” to the binding step to increase antibody recovery. A kinetic binding model was developed to estimate the required residence times in the multi-stage binding step to optimize yield and productivity. Data were obtained by purifying two commercial antibodies from two different manufactures, one with low titer (~0.67 g/L) and one with high titer (~6.9 g/L), demonstrating the versatility of the CCTC system. Host cell protein removal, antibody yields and purities were similar to that obtained with conventional column chromatography; however, the CCTC system showed much higher productivity. These results clearly demonstrate the capabilities of continuous countercurrent tangential chromatography for the commercial purification of monoclonal antibody products. PMID:25747172

Purification of monoclonal antibodies from clarified cell culture fluid using Protein A capture continuous countercurrent tangential chromatography.

PubMed

Dutta, Amit K; Tran, Travis; Napadensky, Boris; Teella, Achyuta; Brookhart, Gary; Ropp, Philip A; Zhang, Ada W; Tustian, Andrew D; Zydney, Andrew L; Shinkazh, Oleg

2015-11-10

Recent studies using simple model systems have demonstrated that continuous countercurrent tangential chromatography (CCTC) has the potential to overcome many of the limitations of conventional Protein A chromatography using packed columns. The objective of this work was to optimize and implement a CCTC system for monoclonal antibody purification from clarified Chinese Hamster Ovary (CHO) cell culture fluid using a commercial Protein A resin. Several improvements were introduced to the previous CCTC system including the use of retentate pumps to maintain stable resin concentrations in the flowing slurry, the elimination of a slurry holding tank to improve productivity, and the introduction of an "after binder" to the binding step to increase antibody recovery. A kinetic binding model was developed to estimate the required residence times in the multi-stage binding step to optimize yield and productivity. Data were obtained by purifying two commercial antibodies from two different manufactures, one with low titer (∼ 0.67 g/L) and one with high titer (∼ 6.9 g/L), demonstrating the versatility of the CCTC system. Host cell protein removal, antibody yields and purities were similar to those obtained with conventional column chromatography; however, the CCTC system showed much higher productivity. These results clearly demonstrate the capabilities of continuous countercurrent tangential chromatography for the commercial purification of monoclonal antibody products. Copyright © 2015 Elsevier B.V. All rights reserved.

Rheological Characteristics of Cement Grout and its Effect on Mechanical Properties of a Rock Fracture

NASA Astrophysics Data System (ADS)

Liu, Quansheng; Lei, Guangfeng; Peng, Xingxin; Lu, Chaobo; Wei, Lai

2018-02-01

Grouting reinforcement, which has an obvious strengthening effect on fractured rock mass, has been widely used in various fields in geotechnical engineering. The rheological properties of grout will greatly affect its diffusion radius in rock fractures, and the water-cement ratio is an important factor in determining the grouting flow patterns. The relationship between shear stress and shear rate which could reflect the grout rheological properties, the effects of water-cement ratio, and temperature on the rheological properties of grouting was studied in the laboratory. Besides, a new method for producing fractured rock specimens was proposed and solved the problem of producing natural fractured rock specimens. To investigate the influences of grouting on mechanical properties of a rock fracture, the fractured rock specimens made using the new method were reinforced by grouting on the independent designed grouting platform, and then normal and tangential mechanical tests were carried out on fractured rock specimens. The results showed that the mechanical properties of fractured rock mass are significantly improved by grouting, the peak shear strength and residual strength of rock fractures are greatly improved, and the resistance to deformation is enhanced after grouting. Normal forces affect the tangential behavior of the rock fracture, and the tangential stress strength increases with normal forces. The strength and stability of fractured rock mass are increased by grouting reinforcement.

Curvature and tangential deflection of discrete arcs: a theory based on the commutator of scatter matrix pairs and its application to vertex detection in planar shape data.

PubMed

Anderson, I M; Bezdek, J C

1984-01-01

This paper introduces a new theory for the tangential deflection and curvature of plane discrete curves. Our theory applies to discrete data in either rectangular boundary coordinate or chain coded formats: its rationale is drawn from the statistical and geometric properties associated with the eigenvalue-eigenvector structure of sample covariance matrices. Specifically, we prove that the nonzero entry of the commutator of a piar of scatter matrices constructed from discrete arcs is related to the angle between their eigenspaces. And further, we show that this entry is-in certain limiting cases-also proportional to the analytical curvature of the plane curve from which the discrete data are drawn. These results lend a sound theoretical basis to the notions of discrete curvature and tangential deflection; and moreover, they provide a means for computationally efficient implementation of algorithms which use these ideas in various image processing contexts. As a concrete example, we develop the commutator vertex detection (CVD) algorithm, which identifies the location of vertices in shape data based on excessive cummulative tangential deflection; and we compare its performance to several well established corner detectors that utilize the alternative strategy of finding (approximate) curvature extrema.

Characterization of centrifugally-loaded flame migration for ultra-compact combustors

NASA Astrophysics Data System (ADS)

LeBay, Kenneth D.

The Air Force Research Laboratory (AFRL) has designed a centrifugally-loaded Ultra-Compact Combustor (UCC) showing viable merit for reducing gas turbine combustor length by as much as 66%. The overarching goal of this research was to characterize the migration of centrifugally-loaded flames in a sectional model of the UCC to enable scaling of the design from 15 cm to the 50--75 cm diameter of most engines. Two-line Planar Laser-Induced Fluorescence thermometry (PLIF) of OH, time-resolved Particle Image Velocimetry (PIV), and high-speed video data were collected. Using a sectional UCC model, the flame migration angle was determined to be a function of the UCC/core velocity ratio (VR) while both the VR and the centrifugal or "g-load" affected the migration quantity. Higher g-loads and lower VRs yielding higher migration but lower VRs had lower core flow temperatures due to higher core air mass flow. A comparison of the straight and curved UCC sections showed the centrifugal load increased the flame migration but increased unsteadiness. The flame migration into the core was estimated using pressure and temperature measurements upstream, and PIV measurements downstream of the core flow interface with constant density and velocity profile assumptions. The flame migration quantity was used to estimate the core flow temperature which was in relatively good agreement with the measured PLIF values. The migration quantity scaled relatively linearly with the UCC tangential velocity, which corresponds to the g-load value, with the slope determined by the VR. A simple analytical model resulted for the dependence of the migration quantity on the tangential velocity and VR. The quantitative relationships determined in this research provided a detailed description of the migration of centrifugally-loaded flames in a sectional UCC.

Wood anatomical analysis of Alnus incana and Betula pendula injured by a debris-flow event.

PubMed

Arbellay, Estelle; Stoffel, Markus; Bollschweiler, Michelle

2010-10-01

Vessel chronologies in ring-porous species have been successfully employed in the past to extract the climate signal from tree rings. Environmental signals recorded in vessels of ring-porous species have also been used in previous studies to reconstruct discrete events of drought, flooding and insect defoliation. However, very little is known about the ability of diffuse-porous species to record environmental signals in their xylem cells. Moreover, time series of wood anatomical features have only rarely been used to reconstruct former geomorphic events. This study was therefore undertaken to characterize the wood anatomical response of diffuse-porous Alnus incana (L.) Moench and Betula pendula Roth to debris-flow-induced wounding. Tree microscopic response to wounding was assessed through the analysis of wood anatomical differences between injured rings formed in the debris-flow event year and uninjured rings formed in the previous year. The two ring types were examined close and opposite to the injury in order to determine whether wound effects on xylem cells decrease with increasing tangential distance from the injury. Image analysis was used to measure vessel parameters as well as fiber and parenchyma cell (FPC) parameters. The results of this study indicate that injured rings are characterized by smaller vessels as compared with uninjured rings. By contrast, FPC parameters were not found to significantly differ between injured and uninjured rings. Vessel and FPC parameters mainly remained constant with increasing tangential distance from the injury, except for a higher proportion of vessel lumen area opposite to the injury within A. incana. This study highlights the existence of anatomical tree-ring signatures-in the form of smaller vessels-related to past debris-flow activity and addresses a new methodological approach to date injuries inflicted on trees by geomorphic processes.

Study of Unsteady Flows with Concave Wall Effect

NASA Technical Reports Server (NTRS)

Wang, Chi R.

2003-01-01

This paper presents computational fluid dynamic studies of the inlet turbulence and wall curvature effects on the flow steadiness at near wall surface locations in boundary layer flows. The time-stepping RANS numerical solver of the NASA Glenn-HT RANS code and a one-equation turbulence model, with a uniform inlet turbulence modeling level of the order of 10 percent of molecular viscosity, were used to perform the numerical computations. The approach was first calibrated for its predictabilities of friction factor, velocity, and temperature at near surface locations within a transitional boundary layer over concave wall. The approach was then used to predict the velocity and friction factor variations in a boundary layer recovering from concave curvature. As time iteration proceeded in the computations, the computed friction factors converged to their values from existing experiments. The computed friction factors, velocity, and static temperatures at near wall surface locations oscillated periodically in terms of time iteration steps and physical locations along the span-wise direction. At the upstream stations, the relationship among the normal and tangential velocities showed vortices effects on the velocity variations. Coherent vortices effect on the velocity components broke down at downstream stations. The computations also predicted the vortices effects on the velocity variations within a boundary layer flow developed along a concave wall surface with a downstream recovery flat wall surface. It was concluded that the computational approach might have the potential to analyze the flow steadiness in a turbine blade flow.

Mean electromotive force generated by asymmetric fluid flow near the surface of earth's outer core

NASA Astrophysics Data System (ADS)

Bhattacharyya, Archana

1992-10-01

The phi component of the mean electromotive force, (ETF) generated by asymmetric flow of fluid just beneath the core-mantle boundary (CMB), is obtained using a geomagnetic field model. This analysis is based on the supposition that the axisymmetric part of fluid flow beneath the CMB is tangentially geostrophic and toroidal. For all the epochs studied, the computed phi component is stronger in the Southern Hemisphere than that in the Northern Hemisphere. Assuming a linear relationship between (ETF) and the azimuthally averaged magnetic field (AAMF), the only nonzero off-diagonal components of the pseudotensor relating ETF to AAMF, are estimated as functions of colatitude, and the physical implications of the results are discussed.

Impact of chemical reaction in fully developed radiated mixed convective flow between two rotating disk

NASA Astrophysics Data System (ADS)

Hayat, T.; Khan, M. Waleed Ahmed; Khan, M. Ijaz; Waqas, M.; Alsaedi, A.

2018-06-01

Flow of magnetohydrodynamic (MHD) viscous fluid between two rotating disks is modeled. Angular velocities of two disks are different. Flow is investigated for nonlinear mixed convection. Heat transfer is analyzed for nonlinear thermal radiation and heat generation/absorption. Chemical reaction is also implemented. Convective conditions of heat and mass transfer are studied. Transformations used lead to reduction of PDEs into the ODEs. The impacts of important physical variables like Prandtl number, Reynold number, Hartman number, mixed convection parameter, chemical reaction and Schmidt number on velocities, temperature and concentration are elaborated. In addition velocity and temperature gradients are physically interpreted. Our obtained results indicate that radial, axial and tangential velocities decrease for higher estimation of Hartman number.

Comparison of histologic margin status in low-grade cutaneous and subcutaneous canine mast cell tumours examined by radial and tangential sections.

PubMed

Dores, C B; Milovancev, M; Russell, D S

2018-03-01

Radial sections are widely used to estimate adequacy of excision in canine cutaneous mast cell tumours (MCTs); however, this sectioning technique estimates only a small fraction of total margin circumference. This study aimed to compare histologic margin status in grade II/low grade MCTs sectioned using both radial and tangential sectioning techniques. A total of 43 circumferential margins were evaluated from 21 different tumours. Margins were first sectioned radially, followed by tangential sections. Tissues were examined by routine histopathology. Tangential margin status differed in 10 of 43 (23.3%) margins compared with their initial status on radial section. Of 39 margins, 9 (23.1%) categorized as histologic tumour-free margin (HTFM) >0 mm were positive on tangential sectioning. Tangential sections detected a significantly higher proportion of positive margins relative to radial sections (exact 2-tailed P-value = .0215). The HTFM was significantly longer in negative tangential margins than positive tangential margins (mean 10.1 vs 3.2 mm; P = .0008). A receiver operating characteristic curve comparing HTFM and tangentially negative margins found an area under the curve of 0.83 (95% confidence interval: 0.71-0.96). Although correct classification peaked at the sixth cut-point of HTFM ≥1 mm, radial sections still incorrectly classified 50% of margins as lacking tumour cells. Radial sections had 100% specificity for predicting negative tangential margins at a cut-point of 10.9 mm. These data indicate that for low grade MCTs, HTFMs >0 mm should not be considered completely excised, particularly when HTFM is <10.9 mm. This will inform future studies that use HTFM and overall excisional status as dependent variables in multivariable prognostic models. © 2017 John Wiley & Sons Ltd.

Turbine exhaust diffuser with a gas jet producing a coanda effect flow control

DOEpatents

Orosa, John; Montgomery, Matthew

2014-02-11

An exhaust diffuser system and method for a turbine engine includes an inner boundary and an outer boundary with a flow path defined therebetween. The inner boundary is defined at least in part by a hub structure that has an upstream end and a downstream end. The outer boundary may include a region in which the outer boundary extends radially inward toward the hub structure and may direct at least a portion of an exhaust flow in the diffuser toward the hub structure. The hub structure includes at least one jet exit located on the hub structure adjacent to the upstream end of the tail cone. The jet exit discharges a flow of gas substantially tangential to an outer surface of the tail cone to produce a Coanda effect and direct a portion of the exhaust flow in the diffuser toward the inner boundary.

Conserved pattern of tangential neuronal migration during forebrain development.

PubMed

Métin, Christine; Alvarez, Chantal; Moudoux, David; Vitalis, Tania; Pieau, Claude; Molnár, Zoltán

2007-08-01

Origin, timing and direction of neuronal migration during brain development determine the distinct organization of adult structures. Changes in these processes might have driven the evolution of the forebrain in vertebrates. GABAergic neurons originate from the ganglionic eminence in mammals and migrate tangentially to the cortex. We are interested in differences and similarities in tangential migration patterns across corresponding telencephalic territories in mammals and reptiles. Using morphological criteria and expression patterns of Darpp-32, Tbr1, Nkx2.1 and Pax6 genes, we show in slice cultures of turtle embryos that early cohorts of tangentially migrating cells are released from the medial ganglionic eminence between stages 14 and 18. Additional populations migrate tangentially from the dorsal subpallium. Large cohorts of tangentially migrating neurons originate ventral to the dorsal ventricular ridge at stage 14 and from the lateral ganglionic eminence from stage 15. Release of GABAergic cells from these regions was investigated further in explant cultures. Tangential migration in turtle proceeds in a fashion similar to mammals. In chimeric slice culture and in ovo graft experiments, the tangentially migrating cells behaved according to the host environment - turtle cells responded to the available cues in mouse slices and mouse cells assumed characteristic migratory routes in turtle brains, indicating highly conserved embryonic signals between these distant species. Our study contributes to the evaluation of theories on the origin of the dorsal cortex and indicates that tangential migration is universal in mammals and sauropsids.

Direct Simulation Monte Carlo Investigation of Noncontinuum Couette Flow

NASA Astrophysics Data System (ADS)

Torczynski, J. R.; Gallis, M. A.

2009-11-01

The Direct Simulation Monte Carlo (DSMC) method of molecular gas dynamics is used to study noncontinuum effects in Couette flow. The walls have equal temperatures and equal accommodation coefficients but unequal tangential velocities. Simulations are performed for near-free-molecular to near-continuum gas pressures with accommodation coefficients of 0.25, 0.5, and 1. Ten gases are examined: argon, helium, nitrogen, sea-level air, and six Inverse-Power-Law (IPL) gases with viscosity temperature exponents of 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0, as represented by the Variable Soft Sphere (VSS) interaction. In all cases, the wall shear stress is proportional to the slip velocity. The momentum transfer coefficient relating these two quantities can be accurately correlated in terms of the Knudsen number based on the wall separation. The two dimensionless parameters in the correlation are similar for all gases examined. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Interior and exterior sound field control using general two-dimensional first-order sources.

PubMed

Poletti, M A; Abhayapala, T D

2011-01-01

Reproduction of a given sound field interior to a circular loudspeaker array without producing an undesirable exterior sound field is an unsolved problem over a broadband of frequencies. At low frequencies, by implementing the Kirchhoff-Helmholtz integral using a circular discrete array of line-source loudspeakers, a sound field can be recreated within the array and produce no exterior sound field, provided that the loudspeakers have azimuthal polar responses with variable first-order responses which are a combination of a two-dimensional (2D) monopole and a radially oriented 2D dipole. This paper examines the performance of circular discrete arrays of line-source loudspeakers which also include a tangential dipole, providing general variable-directivity responses in azimuth. It is shown that at low frequencies, the tangential dipoles are not required, but that near and above the Nyquist frequency, the tangential dipoles can both improve the interior accuracy and reduce the exterior sound field. The additional dipoles extend the useful range of the array by around an octave.

Travelling waves above the canopy of aquatic vegetation

NASA Astrophysics Data System (ADS)

Lyubimov, D.; Lyubimova, T.; Baidina, D.

2012-04-01

When fluid moves over a saturated porous medium with high permeability and porosity, the flow partially involves the fluid in porous medium, however, because of the great resistance force there arises sharp drop of tangential velocity. This leads to the development of instability similar to the Kelvin-Helmholtz instability on discontinuity surface of the tangential velocities of homogeneous fluids. Analogy becomes even more complete if we take into account the deformability of porous medium under the influence of pressure changes. Intensive vortices above the canopy of aquatic vegetation can lead to the coherent oscillations of vegetation, such traveling waves are called monami [1]. In the present paper we investigate stability of steady flow over a saturated porous medium. The importance of this problem is related to the applications to the dynamics of pollutants in the bottom layer of vegetation: the accumulation at low flow and salvo emissions with increasing velocity. We consider a two-layer system consisting of a layer of a viscous incompressible fluid and porous layer saturated with the same fluid located underneath. The lower boundary of the system is assumed to be rigid, the upper boundary - free and non-deformable. Weak slope of the river is taken into account. The problem is solved within the framework of single approach in which a two-layer system is described by a single system of equations for saturated porous medium and the presence of two layers is modeled by introducing variable permeability and porosity, depending on vertical coordinate. The flow in a saturated porous medium is described by the Brinkman model. Solution of the problem for steady flow shows that the velocity profile has two inflection points, which leads to the instability. The neutral curves are obtained for different values of the ratio d of porous layer thickness to full thickness. It is found that the dependence of critical Reynolds number on d is non-monotonic and the wave number of most dangerous perturbations increases monotonically with d. The effect of the deformability of porous medium on linear stability conditions is also investigated. Non-linear flow regimes are studied numerically by finite difference method. The calculations are performed for the rectangular domains whose length is taken to be equal to the wavelength of most dangerous perturbations according to linear stability theory. The calculations show that for low values of Reynolds number the stationary uni-directional flow is realized. Starting from a certain Reynolds number, the stationary oscillations are established with amplitude and frequency depending on the parameters. Analysis of the velocity fields corresponding to different phases of the oscillation period, shows that the observed waves travel in the direction of the basic flow. The work was made under financial support of Russian Foundation for Basic Research. 1. Ghisalberti, M., Nepf, H.M., 2002, Mixing layers and coherent structures in vegetated aquatic flows, J. of Geophysical Research. 107, C2.

[Effects of unified surgical scheme for wounds on the treatment outcome of patients with extensive deep burn].

PubMed

Tang, Wenbin; Li, Xiaojian; Deng, Zhongyuan; Zhang, Zhi; Zhang, Xuhui; Zhang, Tao; Zhong, Xiaomin; Chen, Bin; Liu, Changling

2015-08-01

To investigate the effects of unified surgical scheme for wounds on the outcome of patients with extensive deep partial-thickness to full-thickness (briefly referred to as deep) burn. One hundred and thirty-seven patients with extensive deep burn hospitalized from July 2007 to November 2012 underwent unified surgery according to area of deep wound (unified scheme group, US). Among them, 57 patients with deep wound area less than 51% TBSA received escharectomy or tangential excision by stages followed by autologous mesh skin grafting; 52 patients with deep wound area from 51% to 80% TBSA underwent escharectomy or tangential excision by stages followed by autologous mesh skin grafting and/or small skin grafting, or escharectomy or tangential excision followed by large sheet of allogeneic skin covering plus autologous mesh skin grafting and/or small skin grafting after the removal of allogeneic skin; 28 patients with deep wound area larger than 80% TBSA received escharectomy or tangential excision by stages followed by autologous microskin grafting plus coverage of large sheet of allogeneic skin, or escharectomy or tangential excision followed by small autologous skin grafting and/or intermingled grafting with small autologous and/or allogeneic skin. Another 120 patients with extensive deep burn hospitalized from January 2002 to June 2007 who did not receive unified surgical scheme were included as control group (C). Except for the surgical methods in group US, in 53 patients with deep wound area less than 51% TBSA in group C escharectomy or tangential excision was performed followed by autologous small skin grafting; in 40 patients with deep wound area from 51% to 80% TBSA in group C escharectomy or tangential excision was performed followed by autologous microskin grafting plus large sheet of allogeneic skin covering, or escharectomy or tangential excision followed by large sheet of allogeneic skin embedded with stamp-like autologous skin; in 27 patients with deep wound area larger than 80% TBSA in group C escharectomy or tangential excision was performed followed by covering with large sheet of allogeneic skin embedded with stamp-like autologous skin without intermingled grafting with small autologous and allogeneic skin in group US. In group US, escharectomy of full-thickness wound in extremities was performed with the use of tourniquet in every patient; saline containing adrenaline was subcutaneously injected when performing escharectomy or tangential excision over the trunk and skin excision; normal skin and healed superficial-thickness wound were used as donor sites for several times of skin excision. The baseline condition of patients and their treatment in the aspects of fluid resuscitation, nutrition support, anti-inflammation, and organ function support were similar between the two groups. The mortality and incidence of complications of all patients and wound healing time and times of surgery of healed patients were compared between the two groups. Data were processed with independent sample t test, Mann-Whitney U test, and Fisher's exact test. (1) Both the mortality and the incidence of complications of patients with deep wound area less than 51% TBSA in group US were 0, which were close to those of group C (with P values above 0.05). The number of times of surgery of healed patients with deep wound area less than 51% TBSA in group US was 2.4 ± 0.9, which was obviously fewer than that of group C (3.5 ± 1.8, U=-5.085, P<0.001), but with wound healing time close to that of group C (U=-1.480, P>0.05). (2) Both the mortality and the incidence of complications of patients with deep wound area from 51% to 80% TBSA in group US were 0, which were significantly lower than those of group C [both as 20.0% (8/40), with P values below 0.01]. The number of times of surgery and wound healing time of healed patients with deep wound area from 51% to 80% TBSA in group US were respectively 3.0 ± 1.0 and (43 ± 13) d, which were obviously fewer or shorter than those in group C [4.2 ± 2.3 and (61 ± 34) d, with U values respectively -2.491 and -2.186, P values below 0.05]. (3) Both the mortality and the incidence of complications of patients with deep wound area larger than 80% TBSA in group US were 25.0% (7/28), which were close to those of group C [both as 25.9% (7/27), with P values above 0.05]. The number of times of surgery and wound healing time of healed patients with deep wound area larger than 80% TBSA in group US were close to those of group C (with U values respectively -0.276 and -0.369, P values above 0.05). Unified surgical scheme can indirectly decrease the mortality and the incidence of complications of burn patients with deep wound area from 51% to 80% TBSA; it can reduce times of surgery of healed patients of this type and shorten their wound healing time.

Valve and dash-pot assembly

DOEpatents

Chang, Shih-Chih

1986-01-01

A dash-pot valve comprising a cylinder submerged in the fluid of a housing and having a piston attached to a plunger projecting into the path of closing movement of a pivotal valve member. A vortex chamber in said cylinder is provided with tangentially directed inlets to generate vortex flow upon retraction of said plunger and effect increasing resistance against said piston to progressively retard the closing rate of said valve member toward its seat.

U.S. Army Medical Research Institute of Infectious Disease Annual Progress Report, Fiscal Year 1985

DTIC Science & Technology

1985-10-01

response. 25. (U) 8410-8509-Tangential flow filtration was developed as a safer method of harvesting the 50-L anthrax fermenter cultures...yearly boosters. Efforts over several years have sought to improve this chemical vaccine through optimization of fermenter and recovery techniques so...A collaborative effort with WLAIR led to production of candidate human hybridomas to PA. Progrses: The 50-liter fermenter continues to be used

Ascl1 promotes tangential migration and confines migratory routes by induction of Ephb2 in the telencephalon

PubMed Central

Liu, Yuan-Hsuan; Tsai, Jin-Wu; Chen, Jia-Long; Yang, Wan-Shan; Chang, Pei-Ching; Cheng, Pei-Lin; Turner, David L.; Yanagawa, Yuchio; Wang, Tsu-Wei; Yu, Jenn-Yah

2017-01-01

During development, cortical interneurons generated from the ventral telencephalon migrate tangentially into the dorsal telencephalon. Although Achaete-scute family bHLH transcription factor 1 (Ascl1) plays important roles in the developing telencephalon, whether Ascl1 regulates tangential migration remains unclear. Here, we found that Ascl1 promoted tangential migration along the ventricular zone/subventricular zone (VZ/SVZ) and intermediate zone (IZ) of the dorsal telencephalon. Distal-less homeobox 2 (Dlx2) acted downstream of Ascl1 in promoting tangential migration along the VZ/SVZ but not IZ. We further identified Eph receptor B2 (Ephb2) as a direct target of Ascl1. Knockdown of EphB2 disrupted the separation of the VZ/SVZ and IZ migratory routes. Ephrin-A5, a ligand of EphB2, was sufficient to repel both Ascl1-expressing cells in vitro and tangentially migrating cortical interneurons in vivo. Together, our results demonstrate that Ascl1 induces expression of Dlx2 and Ephb2 to maintain distinct tangential migratory routes in the dorsal telencephalon. PMID:28276447

Numerical simulation and experiment on split tungsten carbide cylinder of high pressure apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yunfei; Li, Mingzhe, E-mail: limz@jlu.edu.cn; Wang, Bolong

2015-12-15

A new high pressure device with a split cylinder was investigated on the basis of the belt-type apparatus. The belt-type die is subjected to excessive tangential tensile stress and the tungsten carbide cylinder is easily damaged in the running process. Taking into account the operating conditions and material properties of the tungsten carbide cylinder, it is divided into 6 blocks to eliminate the tangential tensile stress. We studied two forms of the split type: radial split and tangential split. Simulation results indicate that the split cylinder has more uniform stress distribution and smaller equivalent stress compared with the belt-type cylinder.more » The inner wall of the tangential split cylinder is in the situation that compressive stress is distributed in the axial, radial, and tangential directions. It is similar to the condition of hydrostatic pressure, and it is the best condition for tungsten carbide materials. The experimental results also verify that the tangential split die can bear the highest chamber pressure. Therefore, the tangential split structure can increase the pressure bearing capacity significantly.« less

CFD study of leakage flows in shroud cavities of a compressor impeller

NASA Astrophysics Data System (ADS)

Soldatova, K.

2017-08-01

The flow character in a gap between shroud disc of an impeller and a stator surface (shroud cavity) influences disc friction loss, labyrinth seal loss (parasitic losses) and thrust force. Flow calculations inside the shroud cavity of a model of centrifugal compressor stage and its labyrinth seal in a range of flow rates and axial width and radial gap are presented. The results are presented in terms of non-dimensional coefficients of flow, disc friction and seal leakage losses coefficients and pressure coefficient. The distributions meridional and tangential flow velocities correspond to the continuity and equilibrium equations - flow radial circulation exists in wide cavity and is absent in narrow cavities. The radial pressure distributions as measured and calculated are not fully comparable. The possible reason is that CFD-calculated leakage coefficient is less than calculated by A.Stodola formula. The influence of a cavity width on the losses and the thrust force requires a balanced design.

Role of friction in vertically oscillated granular materials

NASA Astrophysics Data System (ADS)

Moon, Sung Joon; Swift, J. B.; Swinney, Harry L.

2002-11-01

We use a previously validated molecular dynamics simulation of vertically oscillated granular layers to study how the contact friction affects standing wave patterns. Our collision model follows Walton(O. R. Walton, in Particulate Two-Phase Flow), edited by M. C. Roco (Butterworth-Heinemann, Boston, 1993), p. 884.: Dissipation in the normal component of colliding velocity is characterized by the normal coefficient of restitution e (0<= e < 1), and interaction in the tangential component by the tangential coefficient of restitution β = β(μ,e,Φ), where -1<= β <= β_0, μ is the static coefficient of friction on the surface of grains, Φ is the collision angle, and β0 corresponds to the crossover between static and sliding friction. We varied the above parameters independently for the grain-grain collisions and for the grain-wall collisions. The grain-grain friction changes the phase diagram of patterns significantly, and the patterns become fuzzy as the friction is decreased. The grain-wall friction is necessary to stabilize the patterns.

Factors influencing perceived angular velocity.

PubMed

Kaiser, M K; Calderone, J B

1991-11-01

The assumption that humans are able to perceive and process angular kinematics is critical to many structure-from-motion and optical flow models. The current studies investigate this sensitivity, and examine several factors likely to influence angular velocity perception. In particular, three factors are considered: (1) the extent to which perceived angular velocity is determined by edge transitions of surface elements, (2) the extent to which angular velocity estimates are influenced by instantaneous linear velocities of surface elements, and (3) whether element-velocity effects are related to three-dimensional (3-D) tangential velocities or to two-dimensional (2-D) image velocities. Edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities influenced perceived angular velocity; this bias was related to 2-D image velocity rather than 3-D tangential velocity. Despite these biases, however, judgments were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter was surprisingly good, for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).

Liquid fuel injection elements for rocket engines

NASA Technical Reports Server (NTRS)

Cox, George B., Jr. (Inventor)

1993-01-01

Thrust chambers for liquid propellant rocket engines include three principal components. One of these components is an injector which contains a plurality of injection elements to meter the flow of propellants at a predetermined rate, and fuel to oxidizer mixture ratio, to introduce the mixture into the combustion chamber, and to cause them to be atomized within the combustion chamber so that even combustion takes place. Evolving from these injectors are tube injectors. These tube injectors have injection elements for injecting the oxidizer into the combustion chamber. The oxidizer and fuel must be metered at predetermined rates and mixture ratios in order to mix them within the combustion chamber so that combustion takes place smoothly and completely. Hence tube injectors are subject to improvement. An injection element for a liquid propellant rocket engine of the bipropellant type is provided which includes tangential fuel metering orifices, and a plurality of oxidizer tube injection elements whose injection tubes are also provided with tangential oxidizer entry slots and internal reed valves.

Windage Heating in a Shrouded Rotor-Stator System.

PubMed

Tao, Zhi; Zhang, Da; Luo, Xiang; Xu, Guoqiang; Han, Jianqiao

2014-06-01

This paper has experimentally and numerically studied the windage heating in a shrouded rotor-stator disk system with superimposed flow. Temperature rise in the radius direction on the rotating disk is linked to the viscous heating process when cooling air flows through the rotating component. A test rig has been developed to investigate the effect of flow parameters and the gap ratio on the windage heating, respectively. Experimental results were obtained from a 0.45 m diameter disk rotating at up to 12,000 rpm with gap ratio varying from 0.02 to 0.18 and a stator of the same diameter. Infrared temperature measurement technology has been proposed to measure the temperature rise on the rotor surface directly. The PIV technique was adapted to allow for tangential velocity measurements. The tangential velocity data along the radial direction in the cavity was compared with the results obtained by CFD simulation. The comparison between the free disk temperature rise data and an associated theoretical analysis for the windage heating indicates that the adiabatic disk temperature can be measured by infrared method accurately. For the small value of turbulence parameter, the gap ratio has limited influence on the temperature rise distribution along the radius. As turbulence parameter increases, the temperature rise difference is independent of the gap ratio, leaving that as a function of rotational Reynolds number and throughflow Reynolds number only. The PIV results show that the swirl ratio of the rotating core between the rotor and the stator has a key influence on the windage heating.

Poiseuille, thermal transpiration and Couette flows of a rarefied gas between plane parallel walls with nonuniform surface properties in the transverse direction and their reciprocity relations

NASA Astrophysics Data System (ADS)

Doi, Toshiyuki

2018-04-01

Slow flows of a rarefied gas between two plane parallel walls with nonuniform surface properties are studied based on kinetic theory. It is assumed that one wall is a diffuse reflection boundary and the other wall is a Maxwell-type boundary whose accommodation coefficient varies periodically in the direction perpendicular to the flow. The time-independent Poiseuille, thermal transpiration and Couette flows are considered. The flow behavior is numerically studied based on the linearized Bhatnagar-Gross-Krook-Welander model of the Boltzmann equation. The flow field, the mass and heat flow rates in the gas, and the tangential force acting on the wall surface are studied over a wide range of the gas rarefaction degree and the parameters characterizing the distribution of the accommodation coefficient. The locally convex velocity distribution is observed in Couette flow of a highly rarefied gas, similarly to Poiseuille flow and thermal transpiration. The reciprocity relations are numerically confirmed over a wide range of the flow parameters.

A Study on Rotordynamic Characteristics of Swirl Brakes for Three Types of Seals

NASA Astrophysics Data System (ADS)

Xu, Wanjun; Yang, Jiangang

2017-03-01

In order to understand swirl brakes mechanisms and their influence on rotordynamic characteristics for different types of seals, a three-dimensional flow numerical simulation was presented. Three typical seals including labyrinth seal, fully partitioned damper seal and hole-pattern seal were compared under three inlet conditions of no preswirl, preswirl and preswirl with swirl brakes. FAN boundary condition was used to provide inlet preswirl. A modified identification method of effective damping was proposed. Feasibility of the swirl brakes on improving performance of damper seals was discussed. The results show that the swirl brakes influence the seal stability characteristics with whirl frequency. For the labyrinth seal the swirl brakes reverse the sign of effective damping at low frequency and improve the seal stability performance in a wide frequency range. The swirl brakes also improve the damper seals’ stability performance by increasing the low frequency effective damping and reducing their crossover frequency. Further results indicate the swirl brakes affect the rotational direction of the maximum (minimum) pressure positions and enhance the stability of the seals by reducing tangential force in each cavity.

Numerical analysis of combustion characteristics of hybrid rocket motor with multi-section swirl injection

NASA Astrophysics Data System (ADS)

Li, Chengen; Cai, Guobiao; Tian, Hui

2016-06-01

This paper is aimed to analyse the combustion characteristics of hybrid rocket motor with multi-section swirl injection by simulating the combustion flow field. Numerical combustion flow field and combustion performance parameters are obtained through three-dimensional numerical simulations based on a steady numerical model proposed in this paper. The hybrid rocket motor adopts 98% hydrogen peroxide and polyethylene as the propellants. Multiple injection sections are set along the axis of the solid fuel grain, and the oxidizer enters the combustion chamber by means of tangential injection via the injector ports in the injection sections. Simulation results indicate that the combustion flow field structure of the hybrid rocket motor could be improved by multi-section swirl injection method. The transformation of the combustion flow field can greatly increase the fuel regression rate and the combustion efficiency. The average fuel regression rate of the motor with multi-section swirl injection is improved by 8.37 times compared with that of the motor with conventional head-end irrotational injection. The combustion efficiency is increased to 95.73%. Besides, the simulation results also indicate that (1) the additional injection sections can increase the fuel regression rate and the combustion efficiency; (2) the upstream offset of the injection sections reduces the combustion efficiency; and (3) the fuel regression rate and the combustion efficiency decrease with the reduction of the number of injector ports in each injection section.

Effects of finite-size particles on the turbulent flows in a square duct

NASA Astrophysics Data System (ADS)

Yu, Zhaosheng; Lin, Zhaowu; Shao, Xueming; Wang, Lian-Ping

2015-11-01

Fully resolved numerical simulations of the particle-laden turbulent flows in a square duct are performed with a direct-forcing fictitious domain method. The effects of the finite-size particles on the mean and root-mean-square (RMS) velocities are investigated at the friction Reynolds number of 150 (based on the friction velocity and half duct width) and the particle volume fractions ranging from 0.78% to 7.07%. For the neutrally buoyant case, our results show that the mean secondary flow is enhanced and its circulation center shifts closer to the center of the duct cross-section when the particles are added. The reason for the particle effect on the mean secondary flow is analyzed by examining the terms in the mean streamwise vorticity equation. The particles enhance the wall-tangential component of the RMS velocity (i.e. Reynolds normal stress) more than its wall-normal component in the near-wall region near the corners, resulting in the enhancement in the gradients of the normal stress difference, which we think is mainly responsible for the enhancement in the mean secondary flow. The particles accumulate preferentially in the near-corner region in the neutrally buoyant case. In addition, the effects of particle sedimentation are examined at different Shields numbers. The work was supported by the National Natural Science Foundation of China (11372275) and Research Fund for the Doctoral Program of Higher Education of China (20130101110035).

Surfactant Effect on the Average Flow Generation Near Curved Interface

NASA Astrophysics Data System (ADS)

Klimenko, Lyudmila; Lyubimov, Dmitry

2018-02-01

The present work is devoted to the average flow generation near curved interface with a surfactant adsorbed on the surface layer. The investigation was carried out for a liquid drop embedded in a viscous liquid with a different density. The liquid flows inside and outside the drop are generated by small amplitude and high frequency vibrations. Surfactant exchange between the drop surface and the surrounding liquid is limited by the process of adsorption-desorption. It was assumed that the surfactant is soluble in the surrounding liquid, but not soluble in the liquid drop. Surrounding liquid and the liquid in the drop are considered incompressible. Normal and shear viscous stresses balance at the interface is performed under the condition that the film thickness of the adsorbed surfactant is negligible. The problem is solved under assumption that the shape of the drop in the presence of adsorbed surfactant remains spherical symmetry. The effective boundary conditions for the tangential velocity jump and shear stress jump, describing the above generation have been obtained by matched asymptotic expansions method. The conditions under which the drop surface can be considered as a quasi-solid are determined. It is shown that in the case of the significant effect of surfactant on the surface tension, the dominant mechanism for the generation is the Schlichting mechanisms under vibrations.

Experimental and numerical investigation of hydro power generator ventilation

NASA Astrophysics Data System (ADS)

Jamshidi, H.; Nilsson, H.; Chernoray, V.

2014-03-01

Improvements in ventilation and cooling offer means to run hydro power generators at higher power output and at varying operating conditions. The electromagnetic, frictional and windage losses generate heat. The heat is removed by an air flow that is driven by fans and/or the rotor itself. The air flow goes through ventilation channels in the stator, to limit the electrical insulation temperatures. The temperature should be kept limited and uniform in both time and space, avoiding thermal stresses and hot-spots. For that purpose it is important that the flow of cooling air is distributed uniformly, and that flow separation and recirculation are minimized. Improvements of the air flow properties also lead to an improvement of the overall efficiency of the machine. A significant part of the windage losses occurs at the entrance of the stator ventilation channels, where the air flow turns abruptly from tangential to radial. The present work focuses exclusively on the air flow inside a generator model, and in particular on the flow inside the stator channels. The generator model design of the present work is based on a real generator that was previously studied. The model is manufactured taking into consideration the needs of both the experimental and numerical methodologies. Computational Fluid Dynamics (CFD) results have been used in the process of designing the experimental setup. The rotor and stator are manufactured using rapid-prototyping and plexi-glass, yielding a high geometrical accuracy, and optical experimental access. A special inlet section is designed for accurate air flow rate and inlet velocity profile measurements. The experimental measurements include Particle Image Velocimetry (PIV) and total pressure measurements inside the generator. The CFD simulations are performed based on the OpenFOAM CFD toolbox, and the steady-state frozen rotor approach. Specific studies are performed, on the effect of adding "pick-up" to spacers, and the effects of the inlet fan blades on the flow rate through the model. The CFD results capture the experimental flow details to a reasonable level of accuracy.

Tangential Flow Ultrafiltration Allows Purification and Concentration of Lauric Acid-/Albumin-Coated Particles for Improved Magnetic Treatment.

PubMed

Zaloga, Jan; Stapf, Marcus; Nowak, Johannes; Pöttler, Marina; Friedrich, Ralf P; Tietze, Rainer; Lyer, Stefan; Lee, Geoffrey; Odenbach, Stefan; Hilger, Ingrid; Alexiou, Christoph

2015-08-14

Superparamagnetic iron oxide nanoparticles (SPIONs) are frequently used for drug targeting, hyperthermia and other biomedical purposes. Recently, we have reported the synthesis of lauric acid-/albumin-coated iron oxide nanoparticles SEON(LA-BSA), which were synthesized using excess albumin. For optimization of magnetic treatment applications, SPION suspensions need to be purified of excess surfactant and concentrated. Conventional methods for the purification and concentration of such ferrofluids often involve high shear stress and low purification rates for macromolecules, like albumin. In this work, removal of albumin by low shear stress tangential ultrafiltration and its influence on SEON(LA-BSA) particles was studied. Hydrodynamic size, surface properties and, consequently, colloidal stability of the nanoparticles remained unchanged by filtration or concentration up to four-fold (v/v). Thereby, the saturation magnetization of the suspension can be increased from 446.5 A/m up to 1667.9 A/m. In vitro analysis revealed that cellular uptake of SEON(LA-BSA) changed only marginally. The specific absorption rate (SAR) was not greatly affected by concentration. In contrast, the maximum temperature Tmax in magnetic hyperthermia is greatly enhanced from 44.4 °C up to 64.9 °C by the concentration of the particles up to 16.9 mg/mL total iron. Taken together, tangential ultrafiltration is feasible for purifying and concentrating complex hybrid coated SPION suspensions without negatively influencing specific particle characteristics. This enhances their potential for magnetic treatment.

Suppressing Taylor vortices in a Taylor-Couette flow system with free surface

NASA Astrophysics Data System (ADS)

Bouabdallah, A.; Oualli, H.; Mekadem, M.; Gad-El-Hak, M.

2016-11-01

Taylor-Couette flows have been extensively investigated due to their many industrial applications, such as catalytic reactors, electrochemistry, photochemistry, biochemistry, and polymerization. Mass transfer applications include extraction, tangential filtration, crystallization, and dialysis. A 3D study is carried out to simulate a Taylor-Couette flow with a rotating and pulsating inner cylinder. We utilize FLUENT to simulate the incompressible flow with a free surface. The study reveals that flow structuring is initiated with the development of an Ekman vortex at low Taylor number, Ta = 0 . 01 . For all encountered flow regimes, the Taylor vortices are systematically inhibited by the pulsatile motion of the inner cylinder. A spectral analysis shows that this pulsatile motion causes a rapid decay of the free surface oscillations, from a periodic wavy movement to a chaotic one, then to a fully turbulent motion. This degenerative free surface behavior is interpreted as the underlying mechanism responsible for the inhibition of the Taylor vortices.

Power of performance of the thumb adductor muscles: effect of laterality and gender.

PubMed

Gutnik, Boris; Nash, Derek; Ricacho, Norberto; Hudson, Grant; Skirius, Jonas

2006-01-01

The aim of this work was to originally measure mechanical power output of the thumb adductor muscles during fast adduction of the thumb in the horizontal plane. This information will contribute to biomechanical guidelines to help clinicians, sport medicine and rehabilitation specialists in the objective functional evaluation of abnormalities of thumb adductors. Participants performed 20 fast adductions in response to audio signals. Maximum and average angular velocity and angular acceleration were measured. Tangential components of these parameters were then derived. The force of adduction was obtained from the tangential acceleration and the mass of the rotational system. The power was then calculated as the product of the force of adduction and average tangential velocity during the acceleration phase of adduction. All young and untrained males and females were strictly right handed. There was no significant difference in power between dominant and nondominant muscles for either males or females, but males developed significantly more power than females. Because adduction was performed at maximal speed, these data may be explained by the influence of parallel and series elastic elements in the muscle, as well as by influence of fast twitch fibers. Power may be used as a clinical index of the effectiveness of muscle contraction. The similarity of power outputs from dominant and nondominant thumb adductor muscles of right-handers can suggest a classical Bernstein approach. This theoretical approach purports that peripheral factors can distort central commands projected to dominant and nondominant extremities.

Gas separating

DOEpatents

Gollan, Arye Z.

1990-12-25

Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing.

Equilibrium Wall Model Implementation in a Nodal Finite Element Flow Solver JENRE for Large Eddy Simulations

DTIC Science & Technology

2017-11-13

condition is applied to the inviscid and viscous fluxes on the wall to satisfy the surface physical condition, but a non -zero surface tangential...velocity profiles and turbulence quantities predicted by the current wall-model implementation agree well with available experimental data and...implementations. The volume and surface integrals based on the non -zero surface velocity in a cell adjacent to the wall show a good agreement with those

Gas separating

DOEpatents

Gollan, A.

1988-03-29

Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing. 3 figs.

A Solution for Laminar Flow Past a Rotating Cylinder in Crossflow

DTIC Science & Technology

1975-08-01

UMlarl\\ good agreement with experiment was obtained for ratios equal lo > r less tluin O.l.S. The calculated drag coefficients varied at...study, the lift and drag coefficients are calculated as a function of the ratio of the cylinder’s tangential velocity to the velocity of the free streaa ...ahead of separation was in good agree- ment with experimental measurements. These results suggested the 22. H. S. Bluston and B, W. Paulson, nA

Gas separating

DOEpatents

Gollan, Arye

1988-01-01

Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing.

Gas separating

DOEpatents

Gollan, A.Z.

1990-12-25

Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing. 3 figs.

Oblate Field-Reversed Configuration Experiments with Neutral Beam Injection

NASA Astrophysics Data System (ADS)

T., II; Gi, K.; Umezawa, T.; Inomoto, M.; Ono, Y.

2011-11-01

The effect of energetic beam ions on oblate Field-Reversed Configurations (FRCs) has been studied experimentally in the TS-4 plasma merging device. In order to examine its kinetic effects, we developed an economical pulsed Neutral Beam Injection (NBI) system by using a washer gun plasma source and finally attained the beam power of 0.6 MW (15 kV, 40 A) for its pulse length of 0.5 ms, longer than the FRC lifetime in TS-4. The Monte Carlo simulation indicates that the tangential NB ions of 15 keV are trapped between the magnetic axis and the separatrix. We found that two merging high-s (s is plasma size normalized by ion gyroradius) hydrogen spheromaks with opposite helicities relaxed into the large scale FRC with poloidal flux as high as 15 mWb under the assistance of the NBI. Without the assistance of NBI, however, they did not relax to an FRC but to another spheromak. These facts suggest some ion kinetic effects such as toroidal ion flow are essential to FRC stability. Recently, two new NB sources with acceleration voltage and current of 15 kV and 20 A were installed on the TS-4 device on the midplane for tangential injection, increasing the beam power over 1 MW. We will start the upgraded FRC experiments using the 1 MW NBI for ion flow control.

Finite-Difference Solutions of the Alternate Turbopump Development High-Pressure Oxidizer Turbopump Pump-End Ball-Bearing Cavity Flows

NASA Technical Reports Server (NTRS)

Benjamin, Theodore G.; Garcia, Roberto; Mcconnaughey, Paul K.; Wang, Ten-See; Vu, Bruce T.; Dakhoul, Youssef

1993-01-01

These analyses were undertaken to aid in the understanding of flow phenomena in the Alternate Turbopump Development (ATD) High-pressure Oxidizer Turbopump (HPOTP) Pump-end ball bearing (PEBB) cavities and their roles in turbopump vibration initiation and bearing distress. This effort was being performed to provide timely support to the program in a decision as to whether or not the program should be continued. In the first case, it was determined that a change in bearing through flow had no significant effect on axial preload. This was a follow-on to a previous study which had resulted in a redesign of the bearing exit cavity which virtually eliminated bearing axial loading. In the second case, a three-dimensional analysis of the inner-race-guided cage configuration was performed so as to determine the pressure distribution on the outer race when the shaft is 0.0002 inches off-center. The results indicate that there is virtually no circumferential pressure difference caused by the offset to contribute to bearing tilt. In the third case, axisymmetric analyses were performed on an outer-race guided cage configuration to determine the magnitude of tangential flow entering the bearing. The removed-shoulder case was analyzed as was the static diverter case. A third analysis where the preload spring was shielded by a sheet of metal for the baseline case was also performed. It was determined that the swirl entering the bearing was acceptable and the project decided to use the outer-race-guided cage configuration. In the fourth case, more bearing configurations were analyzed. These analyses included thermal modeling so as to determine the added benefit of injecting colder fluid directly onto the bearing inner-race contact area. The results of these analyses contributed to a programmatic decision to include coolant injection in the design.

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.

The Seductive Details Effect in Technology-Delivered Instruction

ERIC Educational Resources Information Center

Towler, Annette; Kraiger, Kurt; Sitzmann, Traci; Van Overberghe, Courtney; Cruz, Jaime; Ronen, Eyal; Stewart, David

2008-01-01

Seductive details are highly interesting information tangential to course objectives. The inclusion of seductive details generally harms performance on recall tests, but few studies have used multimedia training or investigated effects on performance on recognition tests or transfer tasks. We conducted two studies using computer-based training,…

Active Control of Flow Separation Over an Airfoil

NASA Technical Reports Server (NTRS)

Ravindran, S. S.

1999-01-01

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing on airfoils. The unsteady suction and blowing is introduced at the leading edge of the airfoil in the form of tangential jet. Numerical solutions are obtained using Reynolds-Averaged viscous compressible Navier-Stokes equations. Unsteady suction and blowing is investigated as a means of separation control to obtain lift on airfoils. The effect of blowing coefficients on lift and drag is investigated. The numerical simulations are compared with experiments from the Tel-Aviv University (TAU). These results indicate that unsteady suction and blowing can be used as a means of separation control to generate lift on airfoils.

Analytical correlation of centrifugal compressor design geometry for maximum efficiency with specific speed

NASA Technical Reports Server (NTRS)

Galvas, M. R.

1972-01-01

Centrifugal compressor performance was examined analytically to determine optimum geometry for various applications as characterized by specific speed. Seven specific losses were calculated for various combinations of inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, blade exit backsweep, and inlet-tip absolute tangential velocity for solid body prewhirl. The losses considered were inlet guide vane loss, blade loading loss, skin friction loss, recirculation loss, disk friction loss, vaneless diffuser loss, and vaned diffuser loss. Maximum total efficiencies ranged from 0.497 to 0.868 for a specific speed range of 0.257 to 1.346. Curves of rotor exit absolute flow angle, inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, head coefficient and blade exit backsweep are presented over a range of specific speeds for various inducer tip speeds to permit rapid selection of optimum compressor size and shape for a variety of applications.

Supersonic compressor

DOEpatents

Lawlor, Shawn P [Bellevue, WA; Novaresi, Mark A [San Diego, CA; Cornelius, Charles C [Kirkland, WA

2008-02-26

A gas compressor based on the use of a driven rotor having an axially oriented compression ramp traveling at a local supersonic inlet velocity (based on the combination of inlet gas velocity and tangential speed of the ramp) which forms a supersonic shockwave axially, between adjacent strakes. In using this method to compress inlet gas, the supersonic compressor efficiently achieves high compression ratios while utilizing a compact, stabilized gasdynamic flow path. Operated at supersonic speeds, the inlet stabilizes an oblique/normal shock system in the gasdyanamic flow path formed between the gas compression ramp on a strake, the shock capture lip on the adjacent strake, and captures the resultant pressure within the stationary external housing while providing a diffuser downstream of the compression ramp.

Computer program for design analysis of radial-inflow turbines

NASA Technical Reports Server (NTRS)

Glassman, A. J.

1976-01-01

A computer program written in FORTRAN that may be used for the design analysis of radial-inflow turbines was documented. The following information is included: loss model (estimation of losses), the analysis equations, a description of the input and output data, the FORTRAN program listing and list of variables, and sample cases. The input design requirements include the power, mass flow rate, inlet temperature and pressure, and rotational speed. The program output data includes various diameters, efficiencies, temperatures, pressures, velocities, and flow angles for the appropriate calculation stations. The design variables include the stator-exit angle, rotor radius ratios, and rotor-exit tangential velocity distribution. The losses are determined by an internal loss model.

Effects of magnetic drift tangential to magnetic surfaces on neoclassical transport in non-axisymmetric plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuoka, Seikichi, E-mail: matsuoka@rist.or.jp; Satake, Shinsuke; Kanno, Ryutaro

2015-07-15

In evaluating neoclassical transport by radially local simulations, the magnetic drift tangential to a flux surface is usually ignored in order to keep the phase-space volume conservation. In this paper, effect of the tangential magnetic drift on the local neoclassical transport is investigated. To retain the effect of the tangential magnetic drift in the local treatment of neoclassical transport, a new local formulation for the drift kinetic simulation is developed. The compressibility of the phase-space volume caused by the tangential magnetic drift is regarded as a source term for the drift kinetic equation, which is solved by using a two-weightmore » δf Monte Carlo method for non-Hamiltonian system [G. Hu and J. A. Krommes, Phys. Plasmas 1, 863 (1994)]. It is demonstrated that the effect of the drift is negligible for the neoclassical transport in tokamaks. In non-axisymmetric systems, however, the tangential magnetic drift substantially changes the dependence of the neoclassical transport on the radial electric field E{sub r}. The peaked behavior of the neoclassical radial fluxes around E{sub r }={sub  }0 observed in conventional local neoclassical transport simulations is removed by taking the tangential magnetic drift into account.« less

Evaluation of viscous drag reduction schemes for subsonic transports

NASA Technical Reports Server (NTRS)

Marino, A.; Economos, C.; Howard, F. G.

1975-01-01

The results are described of a theoretical study of viscous drag reduction schemes for potential application to the fuselage of a long-haul subsonic transport aircraft. The schemes which were examined included tangential slot injection on the fuselage and various synergetic combinations of tangential slot injection and distributed suction applied to wing and fuselage surfaces. Both passive and mechanical (utilizing turbo-machinery) systems were examined. Overall performance of the selected systems was determined at a fixed subsonic cruise condition corresponding to a flight Mach number of free stream M = 0.8 and an altitude of 11,000 m. The nominal aircraft to which most of the performance data was referenced was a wide-body transport of the Boeing 747 category. Some of the performance results obtained with wing suction are referenced to a Lockheed C-141 Star Lifter wing section. Alternate designs investigated involved combinations of boundary layer suction on the wing surfaces and injection on the fuselage, and suction and injection combinations applied to the fuselage only.

AERODYNAMIC AND BLADING DESIGN OF MULTISTAGE AXIAL FLOW COMPRESSORS

NASA Technical Reports Server (NTRS)

Crouse, J. E.

1994-01-01

The axial-flow compressor is used for aircraft engines because it has distinct configuration and performance advantages over other compressor types. However, good potential performance is not easily obtained. The designer must be able to model the actual flows well enough to adequately predict aerodynamic performance. This computer program has been developed for computing the aerodynamic design of a multistage axial-flow compressor and, if desired, the associated blading geometry input for internal flow analysis. The aerodynamic solution gives velocity diagrams on selected streamlines of revolution at the blade row edges. The program yields aerodynamic and blading design results that can be directly used by flow and mechanical analysis codes. Two such codes are TSONIC, a blade-to-blade channel flow analysis code (COSMIC program LEW-10977), and MERIDL, a more detailed hub-to-shroud flow analysis code (COSMIC program LEW-12966). The aerodynamic and blading design program can reduce the time and effort required to obtain acceptable multistage axial-flow compressor configurations by generating good initial solutions and by being compatible with available analysis codes. The aerodynamic solution assumes steady, axisymmetric flow so that the problem is reduced to solving the two-dimensional flow field in the meridional plane. The streamline curvature method is used for the iterative aerodynamic solution at stations outside of the blade rows. If a blade design is desired, the blade elements are defined and stacked within the aerodynamic solution iteration. The blade element inlet and outlet angles are established by empirical incidence and deviation angles to the relative flow angles of the velocity diagrams. The blade element centerline is composed of two segments tangentially joined at a transition point. The local blade angle variation of each element can be specified as a fourth-degree polynomial function of path distance. Blade element thickness can also be specified with fourth-degree polynomial functions of path distance from the maximum thickness point. Input to the aerodynamic and blading design program includes the annulus profile, the overall compressor mass flow, the pressure ratio, and the rotative speed. A number of input parameters are also used to specify and control the blade row aerodynamics and geometry. The output from the aerodynamic solution has an overall blade row and compressor performance summary followed by blade element parameters for the individual blade rows. If desired, the blade coordinates in the streamwise direction for internal flow analysis codes and the coordinates on plane sections through blades for fabrication drawings may be stored and printed. The aerodynamic and blading design program for multistage axial-flow compressors is written in FORTRAN IV for batch execution and has been implemented on an IBM 360 series computer with a central memory requirement of approximately 470K of 8 bit bytes. This program was developed in 1981.

Understanding and Modeling Vortical Flows to Improve the Technology Readiness Level for Military Aircraft (Comprehension et Modelisation des Flux de Vortex Pour Ameliorer le Niveau de Maturite Technologique au Profit des Avions Militaires)

DTIC Science & Technology

2009-10-01

636.7 115,418 0 2500 5000 7500 10000 12500 iterations -5 -4 -3 -2 -1 0 lo g( dρ /d t) SA EARSM EARSM + CC Hellsten EARSM Hellsten EARSM + CC DRSM...VORTEX BREAKDOWN RTO-TR-AVT-113 29 - 13 θU URo axial= (1) As a vortex passes through a normal shock, the tangential velocity is

Prediction of Aerodynamic Characteristics of Fighter Wings at High Angles of Attack.

DTIC Science & Technology

1984-03-01

potential distribution throughout the network of four points on a body surface great- ly facilitates the flow analysis procedure. Tangential velocity...expensive of computer time. For example, as quoted by McLean, using this coarsest grid network , each 0 surface of the 727-200 wing required 10 minutes of...1980. 19. Le Balleur, J.C. and Neron , M., "Calcul D’Ecoulements3 Visqueux Decolles sur Profils D’Ailes par une Approche de Couplage", AGARn CP-291

Complex large-scale convection of a viscous incompressible fluid with heat exchange according to Newton's law

NASA Astrophysics Data System (ADS)

Gorshkov, A. V.; Prosviryakov, E. Yu.

2017-12-01

The paper considers the construction of analytical solutions to the Oberbeck-Boussinesq system. This system describes layered Bénard-Marangoni convective flows of an incompressible viscous fluid. The third-kind boundary condition, i. e. Newton's heat transfer law, is used on the boundaries of a fluid layer. The obtained solution is analyzed. It is demonstrated that there is a fluid layer thickness with tangential stresses vanishing simultaneously, this being equivalent to the existence of tensile and compressive stresses.

A theoretical formulation of wave-vortex interactions

NASA Technical Reports Server (NTRS)

Wu, J. Z.; Wu, J. M.

1989-01-01

A unified theoretical formulation for wave-vortex interaction, designated the '(omega, Pi) framework,' is presented. Based on the orthogonal decomposition of fluid dynamic interactions, the formulation can be used to study a variety of problems, including the interaction of a longitudinal (acoustic) wave and/or transverse (vortical) wave with a main vortex flow. Moreover, the formulation permits a unified treatment of wave-vortex interaction at various approximate levels, where the normal 'piston' process and tangential 'rubbing' process can be approximated dfferently.

Simulations of Turbulent Flow Over Complex Terrain Using an Immersed-Boundary Method

NASA Astrophysics Data System (ADS)

DeLeon, Rey; Sandusky, Micah; Senocak, Inanc

2018-02-01

We present an immersed-boundary method to simulate high-Reynolds-number turbulent flow over the complex terrain of Askervein and Bolund Hills under neutrally-stratified conditions. We reconstruct both the velocity and the eddy-viscosity fields in the terrain-normal direction to produce turbulent stresses as would be expected from the application of a surface-parametrization scheme based on Monin-Obukhov similarity theory. We find that it is essential to be consistent in the underlying assumptions for the velocity reconstruction and the eddy-viscosity relation to produce good results. To this end, we reconstruct the tangential component of the velocity field using a logarithmic velocity profile and adopt the mixing-length model in the near-surface turbulence model. We use a linear interpolation to reconstruct the normal component of the velocity to enforce the impermeability condition. Our approach works well for both the Askervein and Bolund Hills when the flow is attached to the surface, but shows slight disagreement in regions of flow recirculation, despite capturing the flow reversal.

Simulations of Turbulent Flow Over Complex Terrain Using an Immersed-Boundary Method

NASA Astrophysics Data System (ADS)

DeLeon, Rey; Sandusky, Micah; Senocak, Inanc

2018-06-01

We present an immersed-boundary method to simulate high-Reynolds-number turbulent flow over the complex terrain of Askervein and Bolund Hills under neutrally-stratified conditions. We reconstruct both the velocity and the eddy-viscosity fields in the terrain-normal direction to produce turbulent stresses as would be expected from the application of a surface-parametrization scheme based on Monin-Obukhov similarity theory. We find that it is essential to be consistent in the underlying assumptions for the velocity reconstruction and the eddy-viscosity relation to produce good results. To this end, we reconstruct the tangential component of the velocity field using a logarithmic velocity profile and adopt the mixing-length model in the near-surface turbulence model. We use a linear interpolation to reconstruct the normal component of the velocity to enforce the impermeability condition. Our approach works well for both the Askervein and Bolund Hills when the flow is attached to the surface, but shows slight disagreement in regions of flow recirculation, despite capturing the flow reversal.

Effects of Tangential Edge Constraints on the Postbuckling Behavior of Flat and Curved Panels Subjected to Thermal and Mechanical Loads

NASA Technical Reports Server (NTRS)

Lin, W.; Librescu, L.; Nemeth, M. P.; Starnes, J. H. , Jr.

1994-01-01

A parametric study of the effects of tangential edge constraints on the postbuckling response of flat and shallow curved panels subjected to thermal and mechanical loads is presented. The mechanical loads investigated are uniform compressive edge loads and transverse lateral pressure. The temperature fields considered are associated with spatially nonuniform heating over the panels, and a linear through-the-thickness temperature gradient. The structural model is based on a higher-order transverse-shear-deformation theory of shallow shells that incorporates the effects of geometric nonlinearities, initial geometric imperfections, and tangential edge motion constraints. Results are presented for three-layer sandwich panels made from transversely isotropic materials. Simply supported panels are considered in which the tangential motion of the unloaded edges is either unrestrained, partially restrained, or fully restrained. These results focus on the effects of the tangential edge restraint on the postbuckling response. The results of this study indicate that tangentially restraining the edges of a curved panel can make the panel insensitive to initial geometric imperfections in some cases.

Inertial Particle Migration in the Presence of a Permeate Flow

NASA Astrophysics Data System (ADS)

Garcia, Mike; Singelton, Amanda; Pennathur, Sumita

2016-11-01

Tangential Flow Filtration (TFF) is a rapid and efficient method for the filtration and separation of suspensions of particles such as viruses, bacteria or cellular material. Enhancing the efficacy of TFF not only requires a detailed understanding of particle transport mechanisms, but also the interactions between these mechanisms and a porous wall. In this work, we numerically and experimentally explore the mechanisms of inertial particle migration in the presence of a permeate flow through the porous walls of a microchannel. Numerically, we develop a force balance model to understand the competition between permeate and inertial forces and the resultant consequences on the particle equilibrium location. Experimentally, we fabricated MEMS TFF devices to study the migration of 5, 10 and 15 µm fluorescent polystyrene beads in straight channels with perpendicular permeate flow rates up to 90% of the inlet flow rate. We find that the permeate flow directly influences the inertial focusing position of the particles, both as a function of downstream channel position and ratio of inlet to outlet flow rate. Comparing experiments to our model, we can identify inertial, viscous and a co-dominant regimes.

Detailed Validation Assessment of Turbine Stage Disc Cavity Rotating Flows

NASA Astrophysics Data System (ADS)

Kanjiyani, Shezan

The subject of this thesis is concerned with the amount of cooling air assigned to seal high pressure turbine rim cavities which is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disc life. Excessive purge air, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor-stator forward disc cavity were performed at Arizona State University. The turbine rig has 22 vanes and 28 blades, while the rim cavity is composed of a single-tooth rim lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the rim cavity between the lab seal and the overlap. The data from the experiments were compared to an 360-degree unsteady RANS (URANS) CFD simulations. Although not able to match the time-averaged test data satisfactorily, the CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. To interrogate the validity of URANS simulations in capturing complex rotating flow physics, the scope of this work also included to validating the CFD tool by comparing its predictions against experimental LDV data in a closed rotor-stator cavity. The enclosed cavity has a stationary shroud, a rotating hub, and mass flow does not enter or exit the system. A full 360 degree numerical simulation was performed comparing Fluent LES, with URANS turbulence models. Results from these investigations point to URANS state of art under-predicting closed cavity tangential velocity by 32% to 43%, and open rim cavity effectiveness by 50% compared to test data. The goal of this thesis is to assess the validity of URANS turbulence models in more complex rotating flows, compare accuracy with LES simulations, suggest CFD settings to better simulate turbine stage mainstream/disc cavity interaction with ingestion, and recommend experimentation techniques.

Investigation of the tip clearance flow inside and at the exit of a compressor rotor passage

NASA Technical Reports Server (NTRS)

Pandya, A.; Lakshminarayana, B.

1982-01-01

The nature of the tip clearance flow in a moderately loaded compressor rotor is studied. The measurements were taken inside the clearance between the annulus-wall casing and the rotor blade tip. These measurements were obtained using a stationary two-sensor hot-wire probe in combination with an ensemble averaging technique. The flowfield was surveyed at various radial locations and at ten axial locations, four of which were inside the blade passage in the clearance region and the remaining six outside the passage. Variations of the mean flow properties in the tangential and the radial directions at various axial locations were derived from the data. Variation of the leakage velocity at different axial stations and the annulus-wall boundary layer profiles from passage-averaged mean velocities were also estimated.

Gasdynamic simulations of the solar wind interaction with Venus - Boundary layer formation

NASA Astrophysics Data System (ADS)

McGary, J. E.

1993-05-01

A 2D gasdynamic simulation of the mass-loaded solar wind flow around the dayside of Venus is presented. For average ionopause conditions near 300 km, the simulations show that mass loading from the pickup of oxygen ions produces a boundary layer of finite thickness along the ionopause. Within this layer and toward the ionopause, the temperature decreases and the total mass density increases significantly. Furthermore, there is a shear in the bulk flow velocity across the boundary layer, such that the tangential flow decreases in speed as the ionopause is approached and remains low along the ionopause which is consistent with Pioneer Venus observations. Numerical simulations are carried out for various mass addition rates and demonstrate that the boundary layer develops when oxygen ion production exceeds approximately 2 x 10 exp 5/cu m per s.

Surface Collisions Involving Particles and Moisture (SCIP'M)

NASA Technical Reports Server (NTRS)

Davis, Robert H.

2005-01-01

Experiments were performed on the collision of a solid sphere with a nearly horizontal flat surface covered with a thin layer of viscous liquid. High-speed collisions were obtained by dropping the ball onto the surface from various heights, using gravitational acceleration. Low-speed collisions were obtained using pendulums with long strings or by launching the balls at low velocities in the reduced-gravity environment of parabolic flight. The sphere bounces only when the impact velocity exceeds a critical value. The coefficient of restitution (ratio of rebound velocity to impact velocity) increases with increasing impact velocity above the critical value, indicating the increasing relative importance of elastic deformation to viscous dissipation. The critical impact velocity increases, and the coefficient of restitution decreases, with increasing viscosity or thickness of the liquid layer and with decreasing density or size of the sphere. The ratio of the wet and dry coefficients is expressed as a function of the Stokes number (ratio of particle inertia and viscous forces), showing good agreement between theory and experiment. Similar experiments were performed with the flat surface inclined at various angles to the approaching sphere. A modified Stokes number, which is a measure of the ratio of inertia of the sphere in the normal direction to the viscous forces exerted by the fluid layer, was used for the analysis of oblique collisions. Even for these oblique collisions, it was found that no rebound of the ball was observed below a certain critical Stokes number. The coefficient of normal restitution, defined as a ratio of normal rebound velocity to normal approach velocity, was found to increase beyond the critical Stokes number and even out as it approaches the value for dry restitution at high Stokes numbers. It was also found that, for smooth spheres like steel, the normal restitution at the same modified Stokes number is independent of the angle of impact. The tangential coefficient of restitution, defined as the ratio of tangential rebound velocity to tangential approach velocity, is found to be nearly unity, except for very low approach velocities. Thus, as a first approximation, the theories that predict the coefficient of restitution for head-on wet collisions can be extended to predict the coefficient of normal restitution for oblique wet collisions. Additional experiments were performed with soft surfaces in which a porous cloth or sponge layer was placed over the hard, flat surface. In these experiments, the coefficient of restitution was found to decrease with increasing impact velocity, due to inelastic losses in the soft material. A model combining inelastic deformation and flow through porous media was developed to describe these findings.

Variation in aluminum, iron, and particle concentrations in oxic groundwater samples collected by use of tangential-flow ultrafiltration with low-flow sampling

NASA Astrophysics Data System (ADS)

Szabo, Zoltan; Oden, Jeannette H.; Gibs, Jacob; Rice, Donald E.; Ding, Yuan

2002-02-01

Particulates that move with ground water and those that are artificially mobilized during well purging could be incorporated into water samples during collection and could cause trace-element concentrations to vary in unfiltered samples, and possibly in filtered samples (typically 0.45-um (micron) pore size) as well, depending on the particle-size fractions present. Therefore, measured concentrations may not be representative of those in the aquifer. Ground water may contain particles of various sizes and shapes that are broadly classified as colloids, which do not settle from water, and particulates, which do. In order to investigate variations in trace-element concentrations in ground-water samples as a function of particle concentrations and particle-size fractions, the U.S. Geological Survey, in cooperation with the U.S. Air Force, collected samples from five wells completed in the unconfined, oxic Kirkwood-Cohansey aquifer system of the New Jersey Coastal Plain. Samples were collected by purging with a portable pump at low flow (0.2-0.5 liters per minute and minimal drawdown, ideally less than 0.5 foot). Unfiltered samples were collected in the following sequence: (1) within the first few minutes of pumping, (2) after initial turbidity declined and about one to two casing volumes of water had been purged, and (3) after turbidity values had stabilized at less than 1 to 5 Nephelometric Turbidity Units. Filtered samples were split concurrently through (1) a 0.45-um pore size capsule filter, (2) a 0.45-um pore size capsule filter and a 0.0029-um pore size tangential-flow filter in sequence, and (3), in selected cases, a 0.45-um and a 0.05-um pore size capsule filter in sequence. Filtered samples were collected concurrently with the unfiltered sample that was collected when turbidity values stabilized. Quality-assurance samples consisted of sequential duplicates (about 25 percent) and equipment blanks. Concentrations of particles were determined by light scattering.

Mixing of the Interstellar and Solar Plasmas at the Heliospheric Interface

DOE PAGES

Pogorelov, N. V.; Borovikov, S. N.

2015-10-12

From the ideal MHD perspective, the heliopause is a tangential discontinuity that separates the solar wind plasma from the local interstellar medium plasma. There are physical processes, however, that make the heliopause permeable. They can be subdivided into kinetic and MHD categories. Kinetic processes occur on small length and time scales, and cannot be resolved with MHD equations. On the other hand, MHD instabilities of the heliopause have much larger scales and can be easily observed by spacecraft. The heliopause may also be a subject of magnetic reconnection. In this paper, we discuss mechanisms of plasma mixing at the heliopausemore » in the context of Voyager 1 observations. Numerical results are obtained with a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), which is a package of numerical codes capable of performing adaptive mesh refinement simulations of complex plasma flows in the presence of discontinuities and charge exchange between ions and neutral atoms. The flow of the ionized component is described with the ideal MHD equations, while the transport of atoms is governed either by the Boltzmann equation or multiple Euler gas dynamics equations. The code can also treat nonthermal ions and turbulence produced by them.« less

Method for the prediction of the installation aerodynamics of a propfan at subsonic speeds: User manual

NASA Technical Reports Server (NTRS)

Chandrasekaran, B.

1986-01-01

This document is the user's guide for the method developed earlier for predicting the slipstream wing interaction at subsonic speeds. The analysis involves a subsonic panel code (HESS code) modified to handle the propeller onset flow. The propfan slipstream effects are superimposed on the normal flow boundary condition and are applied over the surface washed by the slipstream. The effects of the propeller slipstream are to increase the axial induced velocity, tangential velocity, and a total pressure rise in the wake of the propeller. Principles based on blade performance theory, momentum theory, and vortex theory were used to evaluate the slipstream effects. The code can be applied to any arbitrary three dimensional geometry, expressed in the form of HESS input format. The code can handle a propeller alone configuration or a propeller/nacelle/airframe configuration, operating up to high subcritical Mach numbers over a range of angles of attack. Inclusion of a viscous modelling is briefly outlined. Wind tunnel results/theory comparisons are included as examples for the application of the code to a generic supercritical wing/overwing Nacelle with a powered propfan. A sample input/output listing is provided.

Planning hybrid intensity modulated radiation therapy for whole-breast irradiation.

PubMed

Farace, Paolo; Zucca, Sergio; Solla, Ignazio; Fadda, Giuseppina; Durzu, Silvia; Porru, Sergio; Meleddu, Gianfranco; Deidda, Maria Assunta; Possanzini, Marco; Orrù, Sivia; Lay, Giancarlo

2012-09-01

To test tangential and not-tangential hybrid intensity modulated radiation therapy (IMRT) for whole-breast irradiation. Seventy-eight (36 right-, 42 left-) breast patients were randomly selected. Hybrid IMRT was performed by direct aperture optimization. A semiautomated method for planning hybrid IMRT was implemented using Pinnacle scripts. A plan optimization volume (POV), defined as the portion of the planning target volume covered by the open beams, was used as the target objective during inverse planning. Treatment goals were to prescribe a minimum dose of 47.5 Gy to greater than 90% of the POV and to minimize the POV and/or normal tissue receiving a dose greater than 107%. When treatment goals were not achieved by using a 4-field technique (2 conventional open plus 2 IMRT tangents), a 6-field technique was applied, adding 2 non tangential (anterior-oblique) IMRT beams. Using scripts, manual procedures were minimized (choice of optimal beam angle, setting monitor units for open tangentials, and POV definition). Treatment goals were achieved by using the 4-field technique in 61 of 78 (78%) patients. The 6-field technique was applied in the remaining 17 of 78 (22%) patients, allowing for significantly better achievement of goals, at the expense of an increase of low-dose (∼5 Gy) distribution in the contralateral tissue, heart, and lungs but with no significant increase of higher doses (∼20 Gy) in heart and lungs. The mean monitor unit contribution to IMRT beams was significantly greater (18.7% vs 9.9%) in the group of patients who required 6-field procedure. Because hybrid IMRT can be performed semiautomatically, it can be planned for a large number of patients with little impact on human or departmental resources, promoting it as the standard practice for whole-breast irradiation. Copyright © 2012 Elsevier Inc. All rights reserved.

Computational analysis of forebody tangential slot blowing on the high alpha research vehicle

NASA Technical Reports Server (NTRS)

Gee, Ken

1995-01-01

A numerical analysis of forebody tangential slot blowing as a means of generating side force and yawing moment is conducted using an aircraft geometry. The Reynolds-averaged, thin-layer, Navier-Stokes equations are solved using a partially flux-split, approximately-factored algorithm. An algebraic turbulence model is used to determine the turbulent eddy viscosity values. Solutions are obtained using both patched and overset grid systems. In the patched grid model, and actuator plane is used to introduce jet variables into the flow field. The overset grid model is used to model the physical slot geometry and facilitate modeling of the full aircraft configuration. A slot optimization study indicates that a short slot located close to the nose of the aircraft provided the most side force and yawing moment per unit blowing coefficient. Comparison of computed surface pressure with that obtained in full-scale wind tunnel tests produce good agreement, indicating the numerical method and grid system used in the study are valid. Full aircraft computations resolve the changes in vortex burst point due to blowing. A time-accurate full-aircraft solution shows the effect of blowing on the changes in the frequency of the aerodynamic loads over the vertical tails. A study of the effects of freestream Mach number and various jet parameters indicates blowing remains effective through the transonic Mach range. An investigation of the force onset time lag associated with forebody blowing shows the lag to be minimal. The knowledge obtained in this study may be applied to the design of a forebody tangential slot blowing system for use on flight aircraft.

Recovery Act: Oxy-Combustion Techology Development for Industrial-Scale Boiler Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levasseur, Armand

2014-04-30

Alstom Power Inc. (Alstom), under U.S. DOE/NETL Cooperative Agreement No. DE-NT0005290, is conducting a development program to generate detailed technical information needed for application of oxy-combustion technology. The program is designed to provide the necessary information and understanding for the next step of large-scale commercial demonstration of oxy combustion in tangentially fired boilers and to accelerate the commercialization of this technology. The main project objectives include: • Design and develop an innovative oxyfuel system for existing tangentially-fired boiler units that minimizes overall capital investment and operating costs. • Evaluate performance of oxyfuel tangentially fired boiler systems in pilot scale testsmore » at Alstom’s 15 MWth tangentially fired Boiler Simulation Facility (BSF). • Address technical gaps for the design of oxyfuel commercial utility boilers by focused testing and improvement of engineering and simulation tools. • Develop the design, performance and costs for a demonstration scale oxyfuel boiler and auxiliary systems. • Develop the design and costs for both industrial and utility commercial scale reference oxyfuel boilers and auxiliary systems that are optimized for overall plant performance and cost. • Define key design considerations and develop general guidelines for application of results to utility and different industrial applications. The project was initiated in October 2008 and the scope extended in 2010 under an ARRA award. The project completion date was April 30, 2014. Central to the project is 15 MWth testing in the BSF, which provided in-depth understanding of oxy-combustion under boiler conditions, detailed data for improvement of design tools, and key information for application to commercial scale oxy-fired boiler design. Eight comprehensive 15 MWth oxy-fired test campaigns were performed with different coals, providing detailed data on combustion, emissions, and thermal behavior over a matrix of fuels, oxyprocess variables and boiler design parameters. Significant improvement of CFD modeling tools and validation against 15 MWth experimental data has been completed. Oxy-boiler demonstration and large reference designs have been developed, supported with the information and knowledge gained from the 15 MWth testing. The results from the 15 MWth testing in the BSF and complimentary bench-scale testing are addressed in this volume (Volume II) of the final report. The results of the modeling efforts (Volume III) and the oxy boiler design efforts (Volume IV) are reported in separate volumes.« less

Accuracy of State-of-the-Art Actuator-Line Modeling for Wind Turbine Wakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jha, Pankaj; Churchfield, Matthew; Moriarty, Patrick

The current actuator line method (ALM) within an OpenFOAM computational fluid dynamics (CFD) solver was used to perform simulations of the NREL Phase VI rotor under rotating and parked conditions, two fixed-wing designs both with an elliptic spanwise loading, and the NREL 5-MW turbine. The objective of this work is to assess and improve the accuracy of the state-of-the-art ALM in predicting rotor blade loads, particularly by focusing on the method used to project the actuator forces onto the flow field as body forces. Results obtained for sectional normal and tangential force coefficients were compared to available experimental data andmore » to the in-house performance code XTurb-PSU. It was observed that the ALM results agree well with measured data and results obtained from XTurb-PSU except in the root and tip regions if a three-dimensional Gaussian of width, ε, constant along the blade span is used to project the actuator force onto the flow field. A new method is proposed where the Gaussian width, ε, varies along the blade span following an elliptic distribution. A general criterion is derived that applies to any planform shape. It is found that the new criterion for ε leads to improved prediction of blade tip loads for a variety of blade planforms and rotor conditions considered.« less

Analysis of Tangential Slot Blowing on F/A-18 Isolated Forebody

NASA Technical Reports Server (NTRS)

Gee, Ken; Rizk, Yehia M.; Schiff, Lewis B.

1995-01-01

The generation of significant side forces and yawing moments on an F/A-18 fuselage through tangential slot blowing is analyzed using computational fluid dynamics. The effects of freestream Mach number, jet exit conditions, jet length, and jet location are studied. The effects of over- and underblowing on force and moment production are analyzed. Non-time-accurate solutions are obtained to determine the steady-state side forces, yawing moments, and surface pressure distributions generated by tangential slot blowing. Time-accurate solutions are obtained to study the force onset time lag of tangential slot blowing. Comparison with available experimental data from full-scale wind-tunnel and subscale wind-tunnel tests are made. This computational analysis complements the experimental results and provides a detailed understanding of the effects of tangential slot blowing on the flowfield about the isolated F/A-18 forebody. Additionally, it extends the slot-blowing database to transonic maneuvering Mach numbers.

Preparation of Pd-Loaded Hierarchical FAU Membranes and Testing in Acetophenone Hydrogenation.

PubMed

Molinari, Raffaele; Lavorato, Cristina; Mastropietro, Teresa F; Argurio, Pietro; Drioli, Enrico; Poerio, Teresa

2016-03-22

Pd-loaded hierarchical FAU (Pd-FAU) membranes, containing an intrinsic secondary non-zeolitic (meso)porosity, were prepared and tested in the catalytic transfer hydrogenation of acetophenone (AP) to produce phenylethanol (PE), an industrially relevant product. The best operating conditions were preliminarily identified by testing different solvents and organic hydrogen donors in a batch hydrogenation process where micron-sized FAU seeds were employed as catalyst support. Water as solvent and formic acid as hydrogen source resulted to be the best choice in terms of conversion for the catalytic hydrogenation of AP, providing the basis for the design of a green and sustainable process. The best experimental conditions were selected and applied to the Pd-loaded FAU membrane finding enhanced catalytic performance such as a five-fold higher productivity than with the unsupported Pd-FAU crystals (11.0 vs. 2.2 mgproduct gcat(-1)·h(-1)). The catalytic performance of the membrane on the alumina support was also tested in a tangential flow system obtaining a productivity higher than that of the batch system (22.0 vs. 11.0 mgproduct gcat(-1)·h(-1)).

Comparison of doses and NTCP to risk organs with enhanced inspiration gating and free breathing for left-sided breast cancer radiotherapy using the AAA algorithm.

PubMed

Edvardsson, Anneli; Nilsson, Martin P; Amptoulach, Sousana; Ceberg, Sofie

2015-04-10

The purpose of this study was to investigate the potential dose reduction to the heart, left anterior descending (LAD) coronary artery and the ipsilateral lung for patients treated with tangential and locoregional radiotherapy for left-sided breast cancer with enhanced inspiration gating (EIG) compared to free breathing (FB) using the AAA algorithm. The radiobiological implication of such dose sparing was also investigated. Thirty-two patients, who received tangential or locoregional adjuvant radiotherapy with EIG for left-sided breast cancer, were retrospectively enrolled in this study. Each patient was CT-scanned during FB and EIG. Similar treatment plans, with comparable target coverage, were created in the two CT-sets using the AAA algorithm. Further, the probability of radiation induced cardiac mortality and pneumonitis were calculated using NTCP models. For tangential treatment, the median V25Gy for the heart and LAD was decreased for EIG from 2.2% to 0.2% and 40.2% to 0.1% (p < 0.001), respectively, whereas there was no significant difference in V20Gy for the ipsilateral lung (p = 0.109). For locoregional treatment, the median V25Gy for the heart and LAD was decreased for EIG from 3.3% to 0.2% and 51.4% to 5.1% (p < 0.001), respectively, and the median ipsilateral lung V20Gy decreased from 27.0% for FB to 21.5% (p = 0.020) for EIG. The median excess cardiac mortality probability decreased from 0.49% for FB to 0.02% for EIG (p < 0.001) for tangential treatment and from 0.75% to 0.02% (p < 0.001) for locoregional treatment. There was no significant difference in risk of radiation pneumonitis for tangential treatment (p = 0.179) whereas it decreased for locoregional treatment from 6.82% for FB to 3.17% for EIG (p = 0.004). In this study the AAA algorithm was used for dose calculation to the heart, LAD and left lung when comparing the EIG and FB techniques for tangential and locoregional radiotherapy of breast cancer patients. The results support the dose and NTCP reductions reported in previous studies where dose calculations were performed using the pencil beam algorithm.

Simulation of a tangential soft x-ray imaging system.

PubMed

Battaglia, D J; Shafer, M W; Unterberg, E A; Bell, R E; Hillis, D L; LeBlanc, B P; Maingi, R; Sabbagh, S; Stratton, B C

2010-10-01

Tangentially viewing soft x-ray (SXR) cameras are capable of detecting nonaxisymmetric plasma structures in magnetically confined plasmas. They are particularly useful for studying stationary perturbations or phenomenon that occur on a timescale faster than the plasma rotation period. Tangential SXR camera diagnostics are planned for the DIII-D and NSTX tokamaks to elucidate the static edge magnetic structure during the application of 3D perturbations. To support the design of the proposed diagnostics, a synthetic diagnostic model was developed using the CHIANTI database to estimate the SXR emission. The model is shown to be in good agreement with the measurements from an existing tangential SXR camera diagnostic on NSTX.

Laminar boundary layer near the rotating end wall of a confined vortex

NASA Astrophysics Data System (ADS)

Shakespeare, W. J.; Levy, E. K.

1982-06-01

The results of an experimental and theoretical investigation of the fluid mechanics in a confined vortex are discussed with particular emphasis on behavior away from the axis of symmetry and near the end walls. The vortex is generated in a rotating cylindrical chamber with an exit opening in one end. Both end walls rotate. For the range of flow rates and swirl ratios (S between 1 and 5) of interest here, the flow field far from the end walls behaves as inviscid and irrotational; and the end wall boundary layers are thin and laminar. Measurements and calculations of tangential and radial velocity in the end wall region show the development of a secondary flow resulting in a strong velocity 'overshoot' in the radial component. Results illustrating the nature of the velocity variations on the end walls are presented; and it is shown that the mass flow rate through the end wall boundary layers, while only a small fraction of the total flow, increases with increasing swirl and with decreasing total flow rate through the chamber.

Wake Vortex Tangential Velocity Adaptive Spectral (TVAS) algorithm for pulsed Lidar systems.

DOT National Transportation Integrated Search

2011-06-20

In 2008 the FAA tasked the Volpe Center with the development of a government owned processing package capable of performing wake detection, characterization and tracking. : The current paper presents the background, progress, and capabilities to date...

Modeling of Supersonic Film Cooling on the J-2X Nozzle Extension

NASA Technical Reports Server (NTRS)

Ruf, Joseph H.; Morris, Christopher I.

2011-01-01

Supersonic film cooling (SSFC) of nozzles has been used in several liquid rocket engine designs, and is being applied to the nozzle extension (NE) of the J-2X upper stage engine currently under development. Turbine exhaust gas (TEG) is injected tangentially from a manifold along the NE, and provides a thermal barrier from the core nozzle flow for the NE. As the TEG stream mixes with the nozzle flow, the effectiveness of the thermal barrier is reduced. This paper documents computational fluid dynamics (CFD) analysis work performed by NASA Marshall Space Flight Center (MSFC) to model the flow of the TEG through the manifold, into the nozzle, and the subsequent mixing of the TEG stream with the core flow. The geometry and grid of the TEG manifold, structural support ribs, and the NE wall will be shown, and the CFD boundary conditions described. The Loci-CHEM CFD code used in this work will also be briefly described. A unique approach to modeling the combined TEG manifold/thrust chamber assembly (TCA) was employed, as it was not practical to model the entire 360 circumferential range in one simulation. Prior CFD validation work modeling Calspan SSFC experiments in the early 1990s, documented in a previous AIAA paper, will also be briefly discussed. The fluid dynamics of the TEG flow through the manifold, into and between the structural support ribs, and into the nozzlette that feeds the TCA will be described. Significant swirl and non-uniformities are present, which along with the wakes from the ribs, act to degrade the film cooling effectiveness compared to idealized injection of TEG gas. The effect of these flow characteristics on the adiabatic wall temperature profile on the NE will be discussed.

Computer program for definition of transonic axial-flow compressor blade rows. [computer program for fabrication and aeroelastic analysis

NASA Technical Reports Server (NTRS)

Crouse, J. E.

1974-01-01

A method is presented for designing axial-flow compressor blading from blade elements defined on cones which pass through the blade-edge streamline locations. Each blade-element centerline is composed of two segments which are tangent to each other. The centerline and surfaces of each segment have constant change of angle with path distance. The stacking line for the blade elements can be leaned in both the axial and tangential directions. The output of the computer program gives coordinates for fabrication and properties for aeroelastic analysis for planar blade sections. These coordinates and properties are obtained by interpolation across conical blade elements. The program is structured to be coupled with an aerodynamic design program.

On the consequences of strong stable stratification at the top of earth's outer core

NASA Technical Reports Server (NTRS)

Bloxham, Jeremy

1990-01-01

The consequences of strong stable stratification at the top of the earth's fluid outer core are considered, concentrating on the generation of the geomagnetic secular variation. It is assumed that the core near the core-mantle boundary is both strongly stably stratified and free of Lorentz forces: it is found that this set of assumptions severely limits the class of possible motions, none of which is compatible with the geomagnetic secular variation. Relaxing either assumption is adequate: tangentially geostrophic flows are consistent with the secular variation if the assumption that the core is strongly stably stratified is relaxed (while retaining the assumption that Lorentz forces are negligible); purely toroidal flows may explain the secular variation if Lorentz forces are included.

Visualization of vortex structures and analysis of frequency of PVC

NASA Astrophysics Data System (ADS)

Gesheva, E. S.; Shtork, S. I.; Alekseenko, S. V.

2018-03-01

The paper presents the results of the study of large-scale vortex structures in a model chamber. Methods of forming quasi-stationary vortices of various shapes by changing the geometric parameters of the chamber have been proposed. In the model chamber with a tangential swirl of the flow, a rectilinear vortex, single helical and double helical vortices were obtained. The double helical structure of the vortex is unique due to its immovability around the axis of the chamber. The resulting structures slowly oscillate around their own axes, which is called the vortex core precession; while the oscillation frequency depends linearly on the liquid flow rate. The use of stationary vortex structures in power plants will increase the efficiency of combustion chambers and reduce slagging.

Wave Augmented Diffuser for Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Skoch, Gary J. (Inventor); Paxson, Daniel E. (Inventor)

2001-01-01

A wave augmented diffuser for a centrifugal compressor surrounds the outlet of an impeller that rotates on a drive shaft having an axis of rotation. The impeller brings flow in in an axial direction and imparts kinetic energy to the flow discharging it in radial and tangential directions. The flow is discharged into a plurality of circumferentially disposed wave chambers. The wave chambers are periodically opened and closed by a rotary valve such that the flow through the diffuser is unsteady. The valve includes a plurality of valve openings that are periodically brought into and out of fluid communication with the wave chambers. When the wave chambers are closed, a reflected compression wave moves upstream towards the diffuser bringing the flow into the wave chamber to rest. This action recovers the kinetic energy from the flow and limits any boundary layer growth. The flow is then discharged in an axial direction through an opening in the valve plate when the valve plate is rotated to an open position. The diffuser thus efficiently raises the static pressure of the fluid and discharges an axially directed flow at a radius that is predominantly below the maximum radius of the diffuser.

Discrete Boltzmann Method with Maxwell-Type Boundary Condition for Slip Flow

NASA Astrophysics Data System (ADS)

Zhang, Yu-Dong; Xu, Ai-Guo; Zhang, Guang-Cai; Chen, Zhi-Hua

2018-01-01

The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model (DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation. It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model. Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model. To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified. Support of National Natural Science Foundation of China under Grant Nos. 11475028, 11772064, and 11502117 Science Challenge Project under Grant Nos. JCKY2016212A501 and TZ2016002

Experimental investigations of the time and flow-direction responses of shear-stress-sensitive liquid crystal coatings

NASA Technical Reports Server (NTRS)

Reda, Daniel C.; Muratore, Joseph J., Jr.; Heineck, James T.

1993-01-01

Time and flow-direction responses of shearstress-sensitive liquid crystal coatings were explored experimentally. For the time-response experiments, coatings were exposed to transient, compressible flows created during the startup and off-design operation of an injector-driven supersonic wind tunnel. Flow transients were visualized with a focusing Schlieren system and recorded with a 1000 frame/sec color video camera. Liquid crystal responses to these changing-shear environments were then recorded with the same video system, documenting color-play response times equal to, or faster than, the time interval between sequential frames (i.e., 1 millisecond). For the flow-direction experiments, a planar test surface was exposed to equal-magnitude and known-direction surface shear stresses generated by both normal and tangential subsonic jet-impingement flows. Under shear, the sense of the angular displacement of the liquid crystal dispersed (reflected) spectrum was found to be a function of the instantaneous direction of the applied shear. This technique thus renders dynamic flow reversals or flow divergences visible over entire test surfaces at image recording rates up to 1 KHz. Extensions of the technique to visualize relatively small changes in surface shear stress direction appear feasible.

Converging flow joint insert system at an intersection between adjacent transitions extending between a combustor and a turbine assembly in a gas turbine engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, Robert T.

A transition duct system (100) for routing a gas flow from a combustor (102) to the first stage (104) of a turbine section (106) in a combustion turbine engine (108), wherein the transition duct system (100) includes one or more converging flow joint inserts (120) forming a trailing edge (122) at an intersection (124) between adjacent transition ducts (126, 128) is disclosed. The transition duct system (100) may include a transition duct (126, 128) having an internal passage (130) extending between an inlet (132, 184) to an outlet (134, 186) and may expel gases into the first stage turbine (104)more » with a tangential component. The converging flow joint insert (120) may be contained within a converging flow joint insert receiver (136) and disconnected from the transition duct bodies (126, 128) by which the converging flow joint insert (120) is positioned. Being disconnected eliminates stress formation within the converging flow joint insert (120), thereby enhancing the life of the insert. The converging flow joint insert (120) may be removable such that the insert (120) can be replaced once worn beyond design limits.« less

Estimation of Power Consumption in the Circular Sawing of Stone Based on Tangential Force Distribution

NASA Astrophysics Data System (ADS)

Huang, Guoqin; Zhang, Meiqin; Huang, Hui; Guo, Hua; Xu, Xipeng

2018-04-01

Circular sawing is an important method for the processing of natural stone. The ability to predict sawing power is important in the optimisation, monitoring and control of the sawing process. In this paper, a predictive model (PFD) of sawing power, which is based on the tangential force distribution at the sawing contact zone, was proposed, experimentally validated and modified. With regard to the influence of sawing speed on tangential force distribution, the modified PFD (MPFD) performed with high predictive accuracy across a wide range of sawing parameters, including sawing speed. The mean maximum absolute error rate was within 6.78%, and the maximum absolute error rate was within 11.7%. The practicability of predicting sawing power by the MPFD with few initial experimental samples was proved in case studies. On the premise of high sample measurement accuracy, only two samples are required for a fixed sawing speed. The feasibility of applying the MPFD to optimise sawing parameters while lowering the energy consumption of the sawing system was validated. The case study shows that energy use was reduced 28% by optimising the sawing parameters. The MPFD model can be used to predict sawing power, optimise sawing parameters and control energy.

Surface Based Analysis of Diffusion Orientation for Identifying Architectonic Domains in the In Vivo Human Cortex

PubMed Central

McNab, Jennifer A.; Polimeni, Jonathan R.; Wang, Ruopeng; Augustinack, Jean C.; Fujimoto, Kyoko; Player, Allison; Janssens, Thomas; Farivar, Reza; Folkerth, Rebecca D.; Vanduffel, Wim; Wald, Lawrence L.

2012-01-01

Diffusion tensor MRI is sensitive to the coherent structure of brain tissue and is commonly used to study large-scale white matter structure. Diffusion in grey matter is more isotropic, however, several groups have observed coherent patterns of diffusion anisotropy within the cerebral cortical grey matter. We extend the study of cortical diffusion anisotropy by relating it to the local coordinate system of the folded cerebral cortex. We use 1mm and sub-millimeter isotropic resolution diffusion imaging to perform a laminar analysis of the principal diffusion orientation, fractional anisotropy, mean diffusivity and partial volume effects. Data from 6 in vivo human subjects, a fixed human brain specimen and an anesthetized macaque were examined. Large regions of cortex show a radial diffusion orientation. In vivo human and macaque data displayed a sharp transition from radial to tangential diffusion orientation at the border between primary motor and somatosensory cortex, and some evidence of tangential diffusion in secondary somatosensory cortex and primary auditory cortex. Ex vivo diffusion imaging in a human tissue sample showed some tangential diffusion orientation in S1 but mostly radial diffusion orientations in both M1 and S1. PMID:23247190

Structure and formation of convection of secondary rainbands in a simulated typhoon Jangmi (2008)

NASA Astrophysics Data System (ADS)

Xiao, Jing; Tan, Zhe-Min; Chow, Kim-Chiu

2018-04-01

Secondary rainbands in tropical cyclone are relatively transient compared with the quasi-stationary principle rainbands. To have a better understanding on their convective structure, a cloud-resolving scale numerical simulation of the super typhoon Jangmi (2008) was performed. The results suggest that the convections in secondary rainbands have some distinctive features that may not be seen in other types of rainbands in tropical cyclone. First, they have a front-like structure and are triggered to form above the boundary layer by the convergence of the above-boundary outflow from the inner side (warmer) and the descending inflow (colder) from the outer side. These elevated convections can be further confirmed by the three-dimensional backward trajectory calculations. Second, due to the release in baroclinic energy, the lower portion of the mid-level inflow from outside may penetrate into the bottom of the convection tower and may help accelerate the boundary layer inflow in the inner side. Third, the local maximum tangential wind is concentrated in the updraft region, with a lower portion which is dipping inward. Tangential wind budget analysis also suggests that the maxima are mainly contributed by the updraft advection, and can be advected cyclonically downstream by the tangential advection.

Influence of non-integer-order derivatives on unsteady unidirectional motions of an Oldroyd-B fluid with generalized boundary conditions

NASA Astrophysics Data System (ADS)

Zafar, A. A.; Riaz, M. B.; Shah, N. A.; Imran, M. A.

2018-03-01

The objective of this article is to study some unsteady Couette flows of an Oldroyd-B fluid with non-integer derivatives. The fluid fills an annular region of two infinite co-axial circular cylinders. Flows are due to the motion of the outer cylinder, that rotates about its axis with an arbitrary time-dependent velocity while the inner cylinder is held fixed. Closed form solutions of dimensionless velocity field and tangential tension are obtained by means of the finite Hankel transform and the theory of Laplace transform for fractional calculus. Several results in the literature including the rotational flows through an infinite cylinder can be obtained as limiting cases of our general solutions. Finally, the control of the fractional framework on the dynamics of fluid is analyzed by numerical simulations and graphical illustrations.

Numerical study of unsteady MHD oblique stagnation point flow and heat transfer due to an oscillating stream

NASA Astrophysics Data System (ADS)

Javed, T.; Ghaffari, A.; Ahmad, H.

2016-05-01

The unsteady stagnation point flow impinging obliquely on a flat plate in presence of a uniform applied magnetic field due to an oscillating stream has been studied. The governing partial differential equations are transformed into dimensionless form and the stream function is expressed in terms of Hiemenz and tangential components. The dimensionless partial differential equations are solved numerically by using well-known implicit finite difference scheme named as Keller-box method. The obtained results are compared with those available in the literature. It is observed that the results are in excellent agreement with the previous studies. The effects of pertinent parameters involved in the problem namely magnetic parameter, Prandtl number and impinging angle on flow and heat transfer characteristics are illustrated through graphs. It is observed that the influence of magnetic field strength increases the fluid velocity and by the increase of obliqueness parameter, the skin friction increases.

Mean velocity and decay characteristics of the guidevane and stator blade wake of an axial flow compressor

NASA Technical Reports Server (NTRS)

Lakshminarayana, B.; Davino, R.

1979-01-01

Pure tone noise, blade row vibrations, and aerodynamic losses are phenomena which are influenced by stator and IGV (inlet guide vane) blade wake production, decay, and interaction in an axial-flow compressor. The objective of this investigation is to develop a better understanding of the nature of stator and IGV blade wakes that are influenced by the presence of centrifugal forces due to flow curvature. A single sensor hot wire probe was employed to determine the three mean velocity components of stator and IGV wakes of a single stage compressor. These wake profiles indicated a varying decay rate of the tangential and axial wake velocity components and a wake profile similarity. An analysis, which predicts this trend, has been developed. The radial velocities are found to be appreciable in both IGV and the stator wakes.

Investigation of spiral blood flow in a model of arterial stenosis.

PubMed

Paul, Manosh C; Larman, Arkaitz

2009-11-01

The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system [Stonebridge PA, Brophy CM. Spiral laminar flow in arteries? Lancet 1991; 338: 1360-1]. We investigate the effects of the spiral blood flow in a model of three-dimensional arterial stenosis with a 75% cross-sectional area reduction at the centre by means of computational fluid dynamics (CFD) techniques. The standard k-omega model is employed for simulation of the blood flow for the Reynolds number of 500 and 1000. We find that for Re=500 the spiral component of the blood flow increases both the total pressure and velocity of the blood, and some significant differences are found between the wall shear stresses of the spiral and non-spiral induced flow downstream of the stenosis. The turbulent kinetic energy is reduced by the spiral flow as it induces the rotational stabilities in the forward flow. For Re=1000 the tangential component of the blood velocity is most influenced by the spiral speed, but the effect of the spiral flow on the centreline turbulent kinetic energy and shear stress is mild. The results of the effects of the spiral flow are discussed in the paper along with the relevant pathological issues.

A proposed through-flow inverse method for the design of mixed-flow pumps

NASA Technical Reports Server (NTRS)

Borges, Joao Eduardo

1991-01-01

A through-flow (hub-to-shroud) truly inverse method is proposed and described. It uses an imposition of mean swirl, i.e., radius times mean tangential velocity, given throughout the meridional section of the turbomachine as an initial design specification. In the present implementation, it is assumed that the fluid is inviscid, incompressible, and irrotational at inlet and that the blades are supposed to have zero thickness. Only blade rows that impart to the fluid a constant work along the space are considered. An application of this procedure to design the rotor of a mixed-flow pump is described in detail. The strategy used to find a suitable mean swirl distribution and the other design inputs is also described. The final blade shape and pressure distributions on the blade surface are presented, showing that it is possible to obtain feasible designs using this technique. Another advantage of this technique is the fact that it does not require large amounts of CPU time.

Fuel injection device and method

DOEpatents

Carlson, L.W.

1983-12-21

A fuel injection system and method provide for shaping a combustion plume within a combustion chamber to effectively recirculate hot combustion gases for stable combustion conditions while providing symmetrical combustion conditions. Char and molten slag are passed to the outer boundary layer to complete combustion of char while permitting initial substoichiometric combustion in a reductive atmosphere for reducing discharge of nitrogen oxides. Shaping of the plume is accomplished by an axially adjustable pintle which permits apportionment of driving pressure between elements which contribute tangential and those which contribute radial directional components to oxidant flow entering the combustion chamber.

Fuel injection device and method

DOEpatents

Carlson, Larry W.

1986-01-01

A fuel injection system and method provide for shaping a combustion plume within a combustion chamber to effectively recirculate hot combustion gases for stable combustion conditions while providing symmetrical combustion conditions. Char and molten slag are passed to the outer boundary layer to complete combustion of char while permitting initial substoichiometric combustion in a reductive atmosphere for reducing discharge of nitrogen oxides. Shaping of the plume is accomplished by an axially adjustable pintle which permits apportionment of driving pressure between elements which contribute tangential and those which contribute radial directional components to oxidant flow entering the combustion chamber.

Fuel injection device and method

DOEpatents

Carlson, Larry W.

1986-02-04

A fuel injection system and method provide for shaping a combustion plume within a combustion chamber to effectively recirculate hot combustion gases for stable combustion conditions while providing symmetrical combustion conditions. Char and molten slag are passed to the outer boundary layer to complete combustion of char while permitting initial substoichiometric combustion in a reductive atmosphere for reducing discharge of nitrogen oxides. Shaping of the plume is accomplished by an axially adjustable pintle which permits apportionment of driving pressure between elements which contribute tangential and those which contribute radial directional components to oxidant flow entering the combustion chamber.

Spheromak plasma flow injection into a torus chamber and the HIST plasmas

NASA Astrophysics Data System (ADS)

Hatuzaki, Akinori

2005-10-01

The importance of plasma flow or two-fluid effect is recognized in understanding the relaxed states of high-beta torus plasmas, start-up and current drive by non-coaxial helicity injection, magnetic reconnection and plasma dynamo in fusion, laboratory and space plasmas. As a new approach to create a flowing two-fluid plasma equilibrium, we have tried to inject tangentially the plasma flow with spheromak-type magnetic configurations into a torus vacuum chamber with an external toroidal magnetic field (TF) coil. In the initial experiments, the RFP-like configuration with helical magnetic structures was realized in the torus vessel. The ion flow measurement with Mach probes showed that the ion flow keeps the same direction despite the reversal of the toroidal current and the axial electric field. The ion fluid comes to flow in the opposite direction to the electron fluid by the reversal of TF. This result suggests that not only electron but also ion flow contributes significantly on the reversed toroidal current. In this case, the ratio of ui to the electron flow velocity ue is estimated as ui/ue ˜ 1/2. We also will inject the spheromak flow into the HIST spherical torus plasmas to examine the possibilities to embedding the two-fluid effect in the ST plasmas.

Three dimensional mean flow and turbulence characteristics of the near wake of a compressor rotor blade

NASA Technical Reports Server (NTRS)

Ravindranath, A.; Lakshminarayana, B.

1980-01-01

The investigation was carried out using the rotating hot wire technique. Measurements were taken inside the end wall boundary layer to discern the effect of annulus and hub wall boundary layer, secondary flow, and tip leakage on the wake structure. Static pressure gradients across the wake were measured using a static stagnation pressure probe insensitive to flow direction changes. The axial and the tangential velocity defects, the radial component of velocity, and turbulence intensities were found to be very large as compared to the near and far wake regions. The radial velocities in the trailing edge region exhibited characteristics prevalent in a trailing vortex system. Flow near the blade tips found to be highly complex due to interaction of the end wall boundary layers, secondary flows, and tip leakage flow with the wake. The streamwise curvature was found to be appreciable near the blade trailing edge. Flow properties in the trailing edge region are quite different compared to that in the near and far wake regions with respect to their decay characteristics, similarity, etc. Fourier decomposition of the rotor wake revealed that for a normalized wake only the first three coefficients are dominant.

Oscillatory slip flow past a spherical inclusion embedded in a Brinkman medium

NASA Astrophysics Data System (ADS)

Palaniappan, D.

2016-11-01

Non-steady flow past an impermeable sphere embedded in a porous medium is investigated based on Brinkman model with Navier slip conditions. Exact analytic solution for the stream-function - involving modified Bessel function of the second kind - describing the slow oscillatory flow around a rigid spherical inclusion is obtained in the limit of low-Reynolds-number. The key parameters such as the frequency of oscillation λ, the permeability constant δ, and the slip coefficient ξ control the flow fields and physical quantities in the entire flow domain. Local streamlines for fixed times demonstrate the variations in flow patterns. Closed form expressions for the tangential velocity profile, wall shear stress, and the force acting on the sphere are computed and compared with the existing results. It is noted that the slip parameter in the range 0 <= ξ <= 0 . 5 has a significant effect in reducing the stress and force. The steady-state velocity overshoot behavior in the vicinity of the sphere is re-iterated. In the limit of large permeability, Darcy (potential) flow is recovered outside a boundary layer. The results are of some interest in predicting maximum wall stress and pressure drop associated with biological models in fibrous media.

Design of tangential viewing phase contrast imaging for turbulence measurements in JT-60SA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, K., E-mail: ktanaka@nifs.ac.jp; Department of Advanced Energy Engineering, Kyushu University, Kasuga, Fukuoka 816-8580; Coda, S.

2016-11-15

A tangential viewing phase contrast imaging system is being designed for the JT-60SA tokamak to investigate microturbulence. In order to obtain localized information on the turbulence, a spatial-filtering technique is applied, based on magnetic shearing. The tangential viewing geometry enhances the radial localization. The probing laser beam is injected tangentially and traverses the entire plasma region including both low and high field sides. The spatial resolution for an Internal Transport Barrier discharge is estimated at 30%–70% of the minor radius at k = 5 cm{sup −1}, which is the typical expected wave number of ion scale turbulence such as ionmore » temperature gradient/trapped electron mode.« less

Vibrating membrane filtration as improved technology for microalgae dewatering.

PubMed

Nurra, Claudia; Clavero, Ester; Salvadó, Joan; Torras, Carles

2014-04-01

The effect of shear-enhanced filtration by vibratory process in microalgae dewatering is presented in this paper. The aim of this research was to investigate the technical performance and improvement of vibrating membrane filtration compared with conventional tangential cross-flow filtration in microalgae concentration. An industrial-scale available commercial set-up was used. Several membrane materials as polyethersulfone, polyacrylonitrile, etc., and mean pore sizes (from 7000Da to 0.2μm) were tested and compared in both filtration set-ups. Experiments were carried-out with Nannochloropsis gaditana and Phaeodactylum tricornutum microalgae. It has been demonstrated that, even if the choice of the membrane depends on its cut-off, its material and the type of microalgae filtrated, dynamic filtration is always the best technology over a conventional one. If with conventional filtration permeability values were in the vicinity of 10L/h/m(2)/bar in steady state phase, with dynamic filtration these values increased to 30L/h/m(2)/bar or more. Copyright © 2014 Elsevier Ltd. All rights reserved.

Nonequilibrium thermodynamics and boundary conditions for reaction and transport in heterogeneous media

NASA Astrophysics Data System (ADS)

Gaspard, Pierre; Kapral, Raymond

2018-05-01

Nonequilibrium interfacial thermodynamics is formulated in the presence of surface reactions for the study of diffusiophoresis in isothermal systems. As a consequence of microreversibility and Onsager-Casimir reciprocal relations, diffusiophoresis, i.e., the coupling of the tangential components of the pressure tensor to the concentration gradients of solute species, has a reciprocal effect where the interfacial currents of solutes are coupled to the slip velocity. The presence of surface reactions is shown to modify the diffusiophoretic and reciprocal effects at the fluid-solid interface. The thin-layer approximation is used to describe the solution flowing near a reactive solid interface. Analytic formulas describing the diffusiophoretic and reciprocal effects are deduced in the thin-layer approximation and tested numerically for the Poiseuille flow of a solution between catalytic planar surfaces.

Combustion synthesis continuous flow reactor

DOEpatents

Maupin, G.D.; Chick, L.A.; Kurosky, R.P.

1998-01-06

The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor. 10 figs.

Combustion synthesis continuous flow reactor

DOEpatents

Maupin, Gary D.; Chick, Lawrence A.; Kurosky, Randal P.

1998-01-01

The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor.

The Consequences of Including Seductive Details during Lecture

ERIC Educational Resources Information Center

Harp, Shannon F.; Maslich, Amy A.

2005-01-01

When text passages include seductive details (i.e., interesting, tangentially related adjuncts that are irrelevant to the lesson), students perform worse on recall (Garner, Gillingham, & White, 1989) and problem-solving tests (Harp & Mayer, 1997, 1998) than students reading the same material without seductive details. To determine whether…

The Intersectional Workings of Whiteness: A Representative Anecdote

ERIC Educational Resources Information Center

Zingsheim, Jason; Goltz, Dustin Bradley

2011-01-01

In this article, the authors engage critical performance pedagogy scholarship on whiteness to both question and extend two persistent trends in the literature. Although intersectionality is commonly referenced in the literature, the larger impulse underscoring Crenshaw's (1991) concept is often footnoted, tangentially marked, or given mere surface…

Full particle-in-cell simulations of kinetic equilibria and the role of the initial current sheet on steady asymmetric magnetic reconnection

NASA Astrophysics Data System (ADS)

Dargent, J.; Aunai, N.; Belmont, G.; Dorville, N.; Lavraud, B.; Hesse, M.

2016-06-01

> Tangential current sheets are ubiquitous in space plasmas and yet hard to describe with a kinetic equilibrium. In this paper, we use a semi-analytical model, the BAS model, which provides a steady ion distribution function for a tangential asymmetric current sheet and we prove that an ion kinetic equilibrium produced by this model remains steady in a fully kinetic particle-in-cell simulation even if the electron distribution function does not satisfy the time independent Vlasov equation. We then apply this equilibrium to look at the dependence of magnetic reconnection simulations on their initial conditions. We show that, as the current sheet evolves from a symmetric to an asymmetric upstream plasma, the reconnection rate is impacted and the X line and the electron flow stagnation point separate from one another and start to drift. For the simulated systems, we investigate the overall evolution of the reconnection process via the classical signatures discussed in the literature and searched in the Magnetospheric MultiScale data. We show that they seem robust and do not depend on the specific details of the internal structure of the initial current sheet.

Purification of diverse hemoglobins by metal salt precipitation.

PubMed

Zimmerman, Devon; Dienes, Jack; Abdulmalik, Osheiza; Elmer, Jacob J

2016-09-01

Although donated blood is the preferred material for transfusion, its limited availability and stringent storage requirements have motivated the development of blood substitutes. The giant extracellular hemoglobin (aka erythrocruorin) of the earthworm Lumbricus terrestris (LtEc) has shown promise as a blood substitute, but an efficient purification method for LtEc must be developed to meet the potential large demand for blood substitutes. In this work, an optimized purification process that uses divalent and trivalent metal salts to selectively precipitate human, earthworm, and bloodworm hemoglobin (HbA, LtEc, and GdHb, respectively) from crude solutions was developed. Although several metal ions were able to selectively precipitate LtEc, Zn(2+) and Ni(2+) provided the lowest heme oxidation and highest overall yield of LtEc. In contrast, Zn(2+) was the only metal ion that completely precipitated HbA and GdHb. Polyacrylamide gel electrophoresis (PAGE) analysis shows that metal precipitation removes several impurities to provide highly pure hemoglobin samples. Heme oxidation levels were relatively low for Zn(2+)-purified HbA and LtEc (2.4±1.3% and 5.3±2.1%, respectively), but slightly higher for Ni(2+)-purified LtEc (8.4±1.2%). The oxygen affinity and cooperativity of the precipitated samples are also identical to samples purified with tangential flow filtration (TFF) alone, indicating the metal precipitation does not significantly affect the function of the hemoglobins. Overall, these results show that hemoglobins from several different species can be highly purified using a combination of metal (Zn(2+)) precipitation and tangential flow filtration. Copyright © 2015 Elsevier Inc. All rights reserved.

Tangential gunshot wound with MagSafe ammunition.

PubMed

Rapkiewicz, Amy V; Tamburri, Robert; Basoa, Mark E; Catanese, Charles A

2005-09-01

MagSafe ammunition is a type of unconventional prefragmented ammunition. A fatal tangential gunshot wound involving MagSafe ammunition is presented. The ammunition and wound characteristics are discussed.

Obliquity dependence of the tangential YORP

NASA Astrophysics Data System (ADS)

Ševeček, P.; Golubov, O.; Scheeres, D. J.; Krugly, Yu. N.

2016-08-01

Context. The tangential Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is a thermophysical effect that can alter the rotation rate of asteroids and is distinct from the so-called normal YORP effect, but to date has only been studied for asteroids with zero obliquity. Aims: We aim to study the tangential YORP force produced by spherical boulders on the surface of an asteroid with an arbitrary obliquity. Methods: A finite element method is used to simulate heat conductivity inside a boulder, to find the recoil force experienced by it. Then an ellipsoidal asteroid uniformly covered by these types of boulders is considered and the torque is numerically integrated over its surface. Results: Tangential YORP is found to operate on non-zero obliquities and decreases by a factor of two for increasing obliquity.

F/A-18 forebody vortex control. Volume 2: Rotary-balance tests

NASA Technical Reports Server (NTRS)

Kramer, Brian R.; Suarez, Carlos J.; Malcolm, Gerald N.; Ayers, Bert F.

1994-01-01

A rotary-balance wind tunnel test was conducted on a six percent model of the F/A-18 at the NASA Ames 7 X 10-Foot Low Speed Wind Tunnel. The data reduction was specially written for the test in National Instruments' LabVIEW. The data acquisition, reduction and analysis was performed with a Macintosh computer. The primary objective of the test was to evaluate the effectiveness of several forebody vortex control configurations in a rotary flow field. The devices that were found to be the most effective during the static tests (Volume 1) were investigated and included both mechanical and pneumatic configurations. The mechanical systems evaluated were small, single and dual, rotating nose tip strakes and a vertical nose strake. The jet blowing configuration used nozzles canted inboard 60 degrees. A two segment tangential slot was also evaluated. The different techniques were evaluated at angles of attack of 30 degrees, 45 degrees, 51 degrees, and 60 degrees. Sideslip and Reynolds number were varied for some of the configurations. All of the techniques proved to be effective in the rotating flow field. The vertical nose strake had the largest 'envelope' of effectiveness. Forebody vortex control provides large, robust yawing moments at medium to high angles of attack, even during combat maneuvers such as loaded roll.

On the extraction of pressure fields from PIV velocity measurements in turbines

NASA Astrophysics Data System (ADS)

Villegas, Arturo; Diez, Fancisco J.

2012-11-01

In this study, the pressure field for a water turbine is derived from particle image velocimetry (PIV) measurements. Measurements are performed in a recirculating water channel facility. The PIV measurements include calculating the tangential and axial forces applied to the turbine by solving the integral momentum equation around the airfoil. The results are compared with the forces obtained from the Blade Element Momentum theory (BEMT). Forces are calculated by using three different methods. In the first method, the pressure fields are obtained from PIV velocity fields by solving the Poisson equation. The boundary conditions are obtained from the Navier-Stokes momentum equations. In the second method, the pressure at the boundaries is determined by spatial integration of the pressure gradients along the boundaries. In the third method, applicable only to incompressible, inviscid, irrotational, and steady flow, the pressure is calculated using the Bernoulli equation. This approximated pressure is known to be accurate far from the airfoil and outside of the wake for steady flows. Additionally, the pressure is used to solve for the force from the integral momentum equation on the blade. From the three methods proposed to solve for pressure and forces from PIV measurements, the first one, which is solved by using the Poisson equation, provides the best match to the BEM theory calculations.

Micromechanics of Ultrafine Particle Adhesion—Contact Models

NASA Astrophysics Data System (ADS)

Tomas, Jürgen

2009-06-01

Ultrafine, dry, cohesive and compressible powders (particle diameter d<10 μm) show a wide variety of flow problems that cause insufficient apparatus and system reliability of processing plants. Thus, the understanding of the micromechanics of particle adhesion is essential to assess the product quality and to improve the process performance in particle technology. Comprehensive models are shown that describe the elastic-plastic force-displacement and frictional moment-angle behavior of adhesive contacts of isotropic smooth spheres. By the model stiff particles with soft contacts, a sphere-sphere interaction of van der Waals forces without any contact deformation describes the stiff attractive term. But, the soft micro-contact response generates a flattened contact, i.e. plate-plate interaction, and increasing adhesion. These increasing adhesion forces between particles directly depend on this frozen irreversible deformation. Thus, the adhesion force is found to be load dependent. It contributes to the tangential forces in an elastic-plastic frictional contact with partially sticking and micro-slip within the contact plane. The load dependent rolling resistance and torque of mobilized frictional contact rotation (spin around its principal axis) are also shown. This reasonable combination of particle contact micromechanics and powder continuum mechanics is used to model analytically the macroscopic friction limits of incipient powder consolidation, yield and cohesive steady-state shear flow on physical basis.

Dielectrophoretic levitation in the presence of shear flow: implications for colloidal fouling of filtration membranes.

PubMed

Molla, Shahnawaz; Bhattacharjee, Subir

2007-10-09

The ability of dielectrophoretic (DEP) forces created using a microelectrode array to levitate particles in a colloidal suspension is studied experimentally and theoretically. The experimental system employs microfabricated electrode arrays on a glass substrate to apply repulsive DEP forces on polystyrene latex particles suspended in an aqueous medium. A numerical model based on the convection-diffusion-migration equation is presented to calculate the concentration distribution of colloidal particles in shear flow under the influence of a repulsive DEP force field. The results obtained from the numerical simulations are compared against trajectory analysis results and experimental data. The results indicate that by incorporating ac electric field-induced DEP forces in a shear flow, particle accumulation and deposition on the flow channel surfaces can be significantly reduced or even completely averted. The mathematical model is then used to indicate how the deposition behavior is modified in the presence of a permeable substrate, representative of tangential flow membrane filtration operations. The results indicate that the repulsive dielectrophoretic (DEP) forces imparted to the particles suspended in the feed can be employed to mitigate membrane fouling in a cross-flow filtration process.

Research on energy conversion mechanism of rotodynamic pump and design of non-overload centrifugal pump

NASA Astrophysics Data System (ADS)

Zhang, X. L.; Hu, S. B.; Shen, Z. Z.; Wu, S. P.; Li, K.

2016-05-01

In this paper, an attempt has been made for the calculation of an expression for the intrinsic law of input power which has not yet been given by current theory of Rotodynamic pump. By adequate recognition of the characteristics of non-inertial system within the rotating impeller, it is concluded that the input power consists of two power components, the first power component, whose magnitude increases with the increase of the flow rate, corresponds to radial velocity component, and the second power component, whose magnitude decreases with the increase of the flow rate, corresponds to tangential velocity component, therefore, the law of rise, basic levelness and drop of input power curves of centrifugal pump, mixed-flow pump and axial-flow pump can be explained reasonably. Through further analysis, the main ways for realizing non-overload of centrifugal pump are obtained, and its equivalent design factor is found out, the factor correlates with the outlet angle of leading face and back face of the blade, wrap angle, number of blades, outlet width, area ratio, and the ratio of operating flow rate to specified flow rate and so on. These are verified with actual example.

Millimeter-wave detection using resonant tunnelling diodes

NASA Technical Reports Server (NTRS)

Mehdi, I.; Kidner, C.; East, J. R.; Haddad, G. I.

1990-01-01

A lattice-matched InGaAs/InAlAs resonant tunnelling diode is studied as a video detector in the millimeter-wave range. Tangential signal sensitivity and video resistance measurements are made as a function of bias and frequency. A tangential signal sensitivity of -37 dBm (1 MHz amplifier bandwidth) with a corresponding video resistance of 350 ohms at 40 GHz has been measured. These results appear to be the first millimeter-wave tangential signal sensitivity and video resistance results for a resonant tunnelling diode.

Lattice Boltzmann simulation of nonequilibrium effects in oscillatory gas flow.

PubMed

Tang, G H; Gu, X J; Barber, R W; Emerson, D R; Zhang, Y H

2008-08-01

Accurate evaluation of damping in laterally oscillating microstructures is challenging due to the complex flow behavior. In addition, device fabrication techniques and surface properties will have an important effect on the flow characteristics. Although kinetic approaches such as the direct simulation Monte Carlo (DSMC) method and directly solving the Boltzmann equation can address these challenges, they are beyond the reach of current computer technology for large scale simulation. As the continuum Navier-Stokes equations become invalid for nonequilibrium flows, we take advantage of the computationally efficient lattice Boltzmann method to investigate nonequilibrium oscillating flows. We have analyzed the effects of the Stokes number, Knudsen number, and tangential momentum accommodation coefficient for oscillating Couette flow and Stokes' second problem. Our results are in excellent agreement with DSMC data for Knudsen numbers up to Kn=O(1) and show good agreement for Knudsen numbers as large as 2.5. In addition to increasing the Stokes number, we demonstrate that increasing the Knudsen number or decreasing the accommodation coefficient can also expedite the breakdown of symmetry for oscillating Couette flow. This results in an earlier transition from quasisteady to unsteady flow. Our paper also highlights the deviation in velocity slip between Stokes' second problem and the confined Couette case.

A Modified EPA Method 1623 that Uses Tangential Flow Hollow-fiber Ultrafiltration and Heat Dissociation Steps to Detect Waterborne Cryptosporidium and Giardia spp.

PubMed Central

Rhodes, Eric R.; Villegas, Leah Fohl; Shaw, Nancy J.; Miller, Carrie; Villegas, Eric N.

2012-01-01

Cryptosporidium and Giardia species are two of the most prevalent protozoa that cause waterborne diarrheal disease outbreaks worldwide. To better characterize the prevalence of these pathogens, EPA Method 1623 was developed and used to monitor levels of these organisms in US drinking water supplies 12. The method has three main parts; the first is the sample concentration in which at least 10 L of raw surface water is filtered. The organisms and trapped debris are then eluted from the filter and centrifuged to further concentrate the sample. The second part of the method uses an immunomagnetic separation procedure where the concentrated water sample is applied to immunomagnetic beads that specifically bind to the Cryptosporidium oocysts and Giardia cysts allowing for specific removal of the parasites from the concentrated debris. These (oo)cysts are then detached from the magnetic beads by an acid dissociation procedure. The final part of the method is the immunofluorescence staining and enumeration where (oo)cysts are applied to a slide, stained, and enumerated by microscopy. Method 1623 has four listed sample concentration systems to capture Cryptosporidium oocysts and Giardia cysts in water: Envirochek filters (Pall Corporation, Ann Arbor, MI), Envirochek HV filters (Pall Corporation), Filta-Max filters (IDEXX, Westbrook, MA), or Continuous Flow Centrifugation (Haemonetics, Braintree, MA). However, Cryptosporidium and Giardia (oo)cyst recoveries have varied greatly depending on the source water matrix and filters used1,14. A new tangential flow hollow-fiber ultrafiltration (HFUF) system has recently been shown to be more efficient and more robust at recovering Cryptosporidium oocystsand Giardia cysts from various water matrices; moreover, it is less expensive than other capsule filter options and can concentrate multiple pathogens simultaneously1-3,5-8,10,11. In addition, previous studies by Hill and colleagues demonstrated that the HFUF significantly improved Cryptosporidium oocysts recoveries when directly compared with the Envirochek HV filters4. Additional modifications to the current methods have also been reported to improve method performance. Replacing the acid dissociation procedure with heat dissociation was shown to be more effective at separating Cryptosporidium from the magnetic beads in some matrices9,13 . This protocol describes a modified Method 1623 that uses the new HFUF filtration system with the heat dissociation step. The use of HFUF with this modified Method is a less expensive alternative to current EPA Method 1623 filtration options and provides more flexibility by allowing the concentration of multiple organisms. PMID:22805201

Design and Fabrication of Oxygen/RP-2 Multi-Element Oxidizer-Rich Staged Combustion Thrust Chamber Injectors

NASA Technical Reports Server (NTRS)

Garcia, C. P.; Medina, C. R.; Protz, C. S.; Kenny, R. J.; Kelly, G. W.; Casiano, M. J.; Hulka, J. R.; Richardson, B. R.

2016-01-01

As part of the Combustion Stability Tool Development project funded by the Air Force Space and Missile Systems Center, the NASA Marshall Space Flight Center was contracted to assemble and hot-fire test a multi-element integrated test article demonstrating combustion characteristics of an oxygen/hydrocarbon propellant oxidizer-rich staged-combustion engine thrust chamber. Such a test article simulates flow through the main injectors of oxygen/kerosene oxidizer-rich staged combustion engines such as the Russian RD-180 or NK-33 engines, or future U.S.-built engine systems such as the Aerojet-Rocketdyne AR-1 engine or the Hydrocarbon Boost program demonstration engine. On the current project, several configurations of new main injectors were considered for the thrust chamber assembly of the integrated test article. All the injector elements were of the gas-centered swirl coaxial type, similar to those used on the Russian oxidizer-rich staged-combustion rocket engines. In such elements, oxidizer-rich combustion products from the preburner/turbine exhaust flow through a straight tube, and fuel exiting from the combustion chamber and nozzle regenerative cooling circuits is injected near the exit of the oxidizer tube through tangentially oriented orifices that impart a swirl motion such that the fuel flows along the wall of the oxidizer tube in a thin film. In some elements there is an orifice at the inlet to the oxidizer tube, and in some elements there is a sleeve or "shield" inside the oxidizer tube where the fuel enters. In the current project, several variations of element geometries were created, including element size (i.e., number of elements or pattern density), the distance from the exit of the sleeve to the injector face, the width of the gap between the oxidizer tube inner wall and the outer wall of the sleeve, and excluding the sleeve entirely. This paper discusses the design rationale for each of these element variations, including hydraulic, structural, thermal, combustion performance, and combustion stability considerations. This paper also discusses the fabrication and assembly of the injector components, including the injector body/interpropellant plate, the additive manufactured GRCop-84 faceplate, and the pieces that make up the injector elements including the oxidizer tube, an inlet to the oxidizer tube, and a facenut that includes the fuel tangential inlets and forms the initial recessed volume where oxidizer and fuel first interact. Hot-fire test results of these main injector designs in an integrated test article that includes an oxidizer-rich preburner are described in companion papers at this JANNAF meeting.

Surfactant effects on interfacial flow and thermal transport processes during phase change in film boiling

NASA Astrophysics Data System (ADS)

Premnath, Kannan N.; Hajabdollahi, Farzaneh; Welch, Samuel W. J.

2018-04-01

The presence of surfactants in two-phase flows results in the transport and adsorption of surfactants to the interface, and the resulting local interfacial concentration significantly influences the surface tension between the liquid and vapor phases in a fluid undergoing phase change. This computational study is aimed at understanding and elucidating the mechanisms of enhanced flows and thermal transport processes in film boiling due to the addition of surfactants. A change in surface tension results in a change in the critical Rayleigh-Taylor wavelength leading to different bubble release patterns and a change in the overall heat transfer rates. Due to the presence of surfactants, an additional transport mechanism of the Marangoni convection arises from the resulting tangential gradients in the surfactant concentration along the phase interface. Our computational approach to study such phenomena consists of representing the interfacial motion by means of the coupled level set-volume-of-fluid method, the fluid motion via the classical marker-and-cell approach, as well as representations for the bulk transport of energy and surfactants, in conjunction with a phase change model and an interfacial surfactant model. Using such an approach, we perform numerical simulations of surfactant-laden single mode as well as multiple mode film boiling and study the effect of surfactants on the transport processes in film boiling, including bubble release patterns, vapor generation rates, and heat transfer rates at different surfactant concentrations. The details of the underlying mechanisms will be investigated and interpreted.

Three-Dimensional Unsteady Simulation of Aerodynamics and Heat Transfer in a Modern High Pressure Turbine Stage

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Ameri, Ali

2009-01-01

Unsteady 3-D RANS simulations have been performed on a highly loaded transonic turbine stage and results are compared to steady calculations as well as to experiment. A low Reynolds number k-epsilon turbulence model is employed to provide closure for the RANS system. A phase-lag boundary condition is used in the tangential direction. This allows the unsteady simulation to be performed by using only one blade from each of the two rows. The objective of this work is to study the effect of unsteadiness on rotor heat transfer and to glean any insight into unsteady flow physics. The role of the stator wake passing on the pressure distribution at the leading edge is also studied. The simulated heat transfer and pressure results agreed favorably with experiment. The time-averaged heat transfer predicted by the unsteady simulation is higher than the heat transfer predicted by the steady simulation everywhere except at the leading edge. The shock structure formed due to stator-rotor interaction was analyzed. Heat transfer and pressure at the hub and casing were also studied. Thermal segregation was observed that leads to the heat transfer patterns predicted by steady and unsteady simulations to be different.

Tangential migration of glutamatergic neurons and cortical patterning during development: Lessons from Cajal-Retzius cells.

PubMed

Barber, Melissa; Pierani, Alessandra

2016-08-01

Tangential migration is a mode of cell movement, which in the developing cerebral cortex, is defined by displacement parallel to the ventricular surface and orthogonal to the radial glial fibers. This mode of long-range migration is a strategy by which distinct neuronal classes generated from spatially and molecularly distinct origins can integrate to form appropriate neural circuits within the cortical plate. While it was previously believed that only GABAergic cortical interneurons migrate tangentially from their origins in the subpallial ganglionic eminences to integrate in the cortical plate, it is now known that transient populations of glutamatergic neurons also adopt this mode of migration. These include Cajal-Retzius cells (CRs), subplate neurons (SPs), and cortical plate transient neurons (CPTs), which have crucial roles in orchestrating the radial and tangential development of the embryonic cerebral cortex in a noncell-autonomous manner. While CRs have been extensively studied, it is only in the last decade that the molecular mechanisms governing their tangential migration have begun to be elucidated. To date, the mechanisms of SPs and CPTs tangential migration remain unknown. We therefore review the known signaling pathways, which regulate parameters of CRs migration including their motility, contact-redistribution and adhesion to the pial surface, and discuss this in the context of how CR migration may regulate their signaling activity in a spatial and temporal manner. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 847-881, 2016. © 2015 Wiley Periodicals, Inc.

Great Bend tornadoes of August 30, 1974

NASA Technical Reports Server (NTRS)

Umenhofer, T. A.; Fujita, T. T.; Dundas, R.

1977-01-01

Photogrammetric analyses of movies and still pictures taken of the Great Bend, Kansas Tornado series have been used to develop design specifications for nuclear power plants and facilities. A maximum tangential velocity of 57 m/sec and a maximum vertical velocity of 27 m/sec are determined for one suction vortex having a translational velocity of 32 m/sec. Three suction vortices with radii in the 20 to 30 m range are noted in the flow field of one tornado; these suction vortices apparently form a local convergence of inflow air inside the outer portion of the tornado core.

Wall boundary layer development near the tip region of an IGV of an axial flow compressor

NASA Technical Reports Server (NTRS)

Lakshminarayana, B.; Sitaram, N.

1983-01-01

The annulus wall boundary layer inside the blade passage of the inlet guide vane (IGV) passage of a low-speed axial compressor stage was measured with a miniature five-hole probe. The three-dimensional velocity and pressure fields were measured at various axial and tangential locations. Limiting streamline angles and static pressures were also measured on the casing of the IGV passage. Strong secondary vorticity was developed. The data were analyzed and correlated with the existing velocity profile correlations. The end wall losses were also derived from these data.

Step Bunching: Influence of Impurities and Solution Flow

NASA Technical Reports Server (NTRS)

Chernov, A. A.; Vekilov, P. G.; Coriell, S. R.; Murray, B. T.; McFadden, G. B.

1999-01-01

Step bunching results in striations even at relatively early stages of its development and in inclusions of mother liquor at the later stages. Therefore, eliminating step bunching is crucial for high crystal perfection. At least 5 major effects causing and influencing step bunching are known: (1) Basic morphological instability of stepped interfaces. It is caused by concentration gradient in the solution normal to the face and by the redistribution of solute tangentially to the interface which redistribution enhances occasional perturbations in step density due to various types of noise; (2) Aggravation of the above basic instability by solution flowing tangentially to the face in the same directions as the steps or stabilization of equidistant step train if these flows are antiparallel; (3) Enhanced bunching at supersaturation where step velocity v increases with relative supersaturation s much faster than linear. This v(s) dependence is believed to be associated with impurities. The impurities of which adsorption time is comparable with the time needed to deposit one lattice layer may also be responsible for bunching; (4) Very intensive solution flow stabilizes growing interface even at parallel solution and step flows; (5) Macrosteps were observed to nucleate at crystal corners and edges. Numerical simulation, assuming step-step interactions via surface diffusion also show that step bunching may be induced by random step nucleation at the facet edge and by discontinuity in the step density (a ridge) somewhere in the middle of a face. The corresponding bunching patterns produce the ones observed in experiment. The nature of step bunching generated at the corners and edges and by dislocation step sources, as well as the also relative importance and interrelations between mechanisms 1-5 is not clear, both from experimental and theoretical standpoints. Furthermore, several laws controlling the evolution of existing step bunches have been suggested, though unambiguous conclusions are still missing. Addressing these issues is the major goal of the present project. The theory addressing the above problem, experimental methods, several figures which include: (1) the spatial wave numbers at which the system is neutrally stable as a function of growth velocity for linear kinetics and supersaturation for nonlinear kinetics; (2) a schematic of the experiment of lysozyme crystal growing under conditions of natural convection; (3) fluctuations in time, t, of the normal growth rate, R(t), vicinal slope, p(t) and Fourier Spectra of R(t), discussions and conclusions are presented.

Turbulence characteristics of swirling flowfields. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Jackson, T. W.; Lilley, D. G.

1985-01-01

The time mean and turbulence properties of a confined swirling jet using the six orientation, single hot wire technique were obtained. The effect of swirl on a confined, expanding jet is to reduce the size of the corner recirculation zone and generate a central recirculation zone followed by a precessing vortex core. The effect of introducing a contraction nozzle of area ratio four, located two test section diameters downstream of the inlet, is to dramatically reduce the size and shape of the central recirculation zone for the swirling flows considered. The shear stresses are found to increase by an order of magnitude in the region of the contraction nozzle because of large radial gradients of axial velocity. Reduction of the expansion ratio to D/o = 1 causes the time mean flow field to be homogeneous throughout the entire test section with the tangential velocity dominating in the swirling cases. No recirculation zones were observed for these particular flows. Turbulence levels and dissipation rates were found to be low except in the entrance regions and in areas of acceleration in the swirling flow cases.

Eigenmodes of Ducted Flows With Radially-Dependent Axial and Swirl Velocity Components

NASA Technical Reports Server (NTRS)

Kousen, Kenneth A.

1999-01-01

This report characterizes the sets of small disturbances possible in cylindrical and annular ducts with mean flow whose axial and tangential components vary arbitrarily with radius. The linearized equations of motion are presented and discussed, and then exponential forms for the axial, circumferential, and time dependencies of any unsteady disturbances are assumed. The resultant equations form a generalized eigenvalue problem, the solution of which yields the axial wavenumbers and radial mode shapes of the unsteady disturbances. Two numerical discretizations are applied to the system of equations: (1) a spectral collocation technique based on Chebyshev polynomial expansions on the Gauss-Lobatto points, and (2) second and fourth order finite differences on uniform grids. The discretized equations are solved using a standard eigensystem package employing the QR algorithm. The eigenvalues fall into two primary categories: a discrete set (analogous to the acoustic modes found in uniform mean flows) and a continuous band (analogous to convected disturbances in uniform mean flows) where the phase velocities of the disturbances correspond to the local mean flow velocities. Sample mode shapes and eigensystem distributions are presented for both sheared axial and swirling flows. The physics of swirling flows is examined with reference to hydrodynamic stability and completeness of the eigensystem expansions. The effect of assuming exponential dependence in the axial direction is discussed.

Combined effects of magnetic field and partial slip on obliquely striking rheological fluid over a stretching surface

NASA Astrophysics Data System (ADS)

Nadeem, S.; Mehmood, Rashid; Akbar, Noreen Sher

2015-03-01

This study explores the collective effects of partial slip and transverse magnetic field on an oblique stagnation point flow of a rheological fluid. The prevailing momentum equations are designed by manipulating Casson fluid model. By applying the suitable similarity transformations, the governing system of equations is being transformed into coupled nonlinear ordinary differential equations. The resulting system is handled numerically through midpoint integration scheme together with Richardson's extrapolation. It is found that both normal and tangential velocity profiles decreases with an increase in magnetic field as well as slip parameter. Streamlines pattern are presented to study the actual impact of slip mechanism and magnetic field on the oblique flow. A suitable comparison with the previous literature is also provided to confirm the accuracy of present results for the limiting case.

Manufacturing of Proteins and Antibodies: Chapter Downstream Processing Technologies : Harvest Operations.

PubMed

Turner, Richard; Joseph, Adrian; Titchener-Hooker, Nigel; Bender, Jean

2017-08-04

Cell harvesting is the separation or retention of cells and cellular debris from the supernatant containing the target molecule Selection of harvest method strongly depends on the type of cells, mode of bioreactor operation, process scale, and characteristics of the product and cell culture fluid. Most traditional harvesting methods use some form of filtration, centrifugation, or a combination of both for cell separation and/or retention. Filtration methods include normal flow depth filtration and tangential flow microfiltration. The ability to scale down predictably the selected harvest method helps to ensure successful production and is critical for conducting small-scale characterization studies for confirming parameter targets and ranges. In this chapter we describe centrifugation and depth filtration harvesting methods, share strategies for harvest optimization, present recent developments in centrifugation scale-down models, and review alternative harvesting technologies.

Calculation of symmetric and asymmetric vortex seperation on cones and tangent ogives based on discrete vortex models

NASA Technical Reports Server (NTRS)

Chin, S.; Lan, C. Edward

1988-01-01

An inviscid discrete vortex model, with newly derived expressions for the tangential velocity imposed at the separation points, is used to investigate the symmetric and asymmetric vortex separation on cones and tangent ogives. The circumferential locations of separation are taken from experimental data. Based on a slender body theory, the resulting simultaneous nonlinear algebraic equations in a cross-flow plane are solved with Broyden's modified Newton-Raphson method. Total force coefficients are obtained through momentum principle with new expressions for nonconical flow. It is shown through the method of function deflation that multiple solutions exist at large enough angles of attack, even with symmetric separation points. These additional solutions are asymmetric in vortex separation and produce side force coefficients which agree well with data for cones and tangent ogives.

Comment on "Heat transfer and fluid flow in microchannels and nanochannels at high Knudsen number using thermal lattice-Boltzmann method".

PubMed

Luo, Li-Shi

2011-10-01

In this Comment we reveal the falsehood of the claim that the lattice Bhatnagar-Gross-Krook (BGK) model "is capable of modeling shear-driven, pressure-driven, and mixed shear-pressure-driven rarified [sic] flows and heat transfer up to Kn=1 in the transitional regime" made in a recent paper [Ghazanfarian and Abbassi, Phys. Rev. E 82, 026307 (2010)]. In particular, we demonstrate that the so-called "Knudsen effects" described are merely numerical artifacts of the lattice BGK model and they are unphysical. Specifically, we show that the erroneous results for the pressure-driven flow in a microchannel imply the false and unphysical condition that 6σKn<-1, where Kn is the Knudsen number σ=(2-σ(v))/σ(v) and σ(v)∈(0,1] is the tangential momentum accommodation coefficient. We also show explicitly that the defects of the lattice BGK model can be completely removed by using the multiple-relaxation-time collision model.

Solutions for Reacting and Nonreacting Viscous Shock Layers with Multicomponent Diffusion and Mass Injection. Ph.D. Thesis - Virginia Polytechnic Inst. and State Univ.

NASA Technical Reports Server (NTRS)

Moss, J. N.

1971-01-01

Numerical solutions are presented for the viscous shocklayer equations where the chemistry is treated as being either frozen, equilibrium, or nonequilibrium. Also the effects of the diffusion model, surface catalyticity, and mass injection on surface transport and flow parameters are considered. The equilibrium calculations for air species using multicomponent: diffusion provide solutions previously unavailable. The viscous shock-layer equations are solved by using an implicit finite-difference scheme. The flow is treated as a mixture of inert and thermally perfect species. Also the flow is assumed to be in vibrational equilibrium. All calculations are for a 45 deg hyperboloid. The flight conditions are those for various altitudes and velocities in the earth's atmosphere. Data are presented showing the effects of the chemical models; diffusion models; surface catalyticity; and mass injection of air, water, and ablation products on heat transfer; skin friction; shock stand-off distance; wall pressure distribution; and tangential velocity, temperature, and species profiles.

Rheological State Diagrams for Rough Colloids in Shear Flow.

PubMed

Hsiao, Lilian C; Jamali, Safa; Glynos, Emmanouil; Green, Peter F; Larson, Ronald G; Solomon, Michael J

2017-10-13

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

Rheological State Diagrams for Rough Colloids in Shear Flow

NASA Astrophysics Data System (ADS)

Hsiao, Lilian C.; Jamali, Safa; Glynos, Emmanouil; Green, Peter F.; Larson, Ronald G.; Solomon, Michael J.

2017-10-01

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

Evaluation of Impinging Stream Vortex Chamber Concepts for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Bullard, Brad; Kopicz, Charles; Michaels, Scott

2002-01-01

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concepts not only offer system simplicity, but also enhance the combustion performance. Test results have shown that chamber performance is markedly high even at a low chamber length-to-diameter ratio (LD). This incentive can be translated to a convenience in the thrust chamber packaging. Variations of the vortex chamber concepts have been introduced in the past few decades. These investigations include an ongoing work at Orbital Technologies Corporation (ORBITEC). By injecting the oxidizer tangentially at the chamber convergence and fuel axially at the chamber head end, Knuth et al. were able to keep the wall relatively cold. A recent investigation of the low L/D vortex chamber concept for gel propellants was conducted by Michaels. He used both triplet (two oxidizer orifices and one fuel orifice) and unlike impinging schemes to inject propellants tangentially along the chamber wall. Michaels called the subject injection scheme an Impinging Stream Vortex Chamber (ISVC). His preliminary tests showed that high performance, with an Isp efficiency of 9295, can be obtained. MSFC and the U. S. Army are jointly investigating an application of the ISVC concept for the cryogenic oxygen/hydrocarbon propellant system. This vortex chamber concept is currently tested with gel propellants at AMCOM at Redstone Arsenal, Alabama. A version of this concept for the liquid oxygen (LOX) hydrocarbon fuel (RP-1) system has been derived from the one for the gel propellant. An unlike impinging injector was employed to deliver the propellants to the chamber. MSFC is also conducting an alternative injection scheme, called the chasing injector, associated with this vortex chamber concept. In this injection technique, both propellant jets and their impingement point are in the same chamber cross-sectional plane. Long duration tests (approximately up to 15 seconds) will be conducted on the ISVC to study the thermal effects. This paper will report the progress of the subject efforts at NASA Marshall Space Flight Center. Thrust chamber performance and thermal wall compatibility will be evaluated. The chamber pressures, wall temperatures, and thrust will be measured as appropriate. The test data will be used to validate CFD models, which, in turn, will be used to design the optimum vortex chambers. Measurements in the previous tests showed that the chamber pressures vary significantly with radius. This is due to the existence of the vortices in the chamber flow field. Hence, the combustion efficiency may not be easily determined from chamber pressure. For this project, measured thrust data will be collected. The performance comparison will be in terms of specific impulse efficiencies. In addition to the thrust measurements, several pressure and temperature readings at various locations on the chamber head faceplate and the chamber wall will be made. The first injector and chamber were designed and fabricated based on the available data and experience gained during gel propellant system tests by the U.S. Army. The alternate injector for the ISVC was also fabricated. Hot-fire tests of the vortex chamber are about to start and are expected to complete in February of 2003 at the TS115 facility of MSFC.

On the generation of tangential ground motion by underground explosions in jointed rocks

NASA Astrophysics Data System (ADS)

Vorobiev, Oleg; Ezzedine, Souheil; Antoun, Tarabay; Glenn, Lewis

2015-03-01

This paper describes computational studies of tangential ground motions generated by spherical explosions in a heavily jointed granite formation. Various factors affecting the shear wave generation are considered, including joint spacing, orientation and frictional properties. Simulations are performed both in 2-D for a single joint set to elucidate the basic response mechanisms, and in 3-D for multiple joint sets to realistically represent in situ conditions in a realistic geological setting. The joints are modelled explicitly using both contact elements and weakness planes in the material. Simulations are performed both deterministically and stochastically to quantify the effects of geological uncertainties on near field ground motions. The mechanical properties of the rock and the joints as well as the joint spacing and orientation are taken from experimental test data and geophysical logs corresponding to the Climax Stock granitic outcrop, which is the geological setting of the source physics experiment (SPE). Agreement between simulation results and near field wave motion data from SPE enables newfound understanding of the origin and extent of non-spherical motions associated with underground explosions in fractured geological media.

Linear ultrasonic motor for absolute gravimeter.

PubMed

Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

2017-05-01

Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters. Copyright © 2017 Elsevier B.V. All rights reserved.

Influences of rolling method on deformation force in cold roll-beating forming process

NASA Astrophysics Data System (ADS)

Su, Yongxiang; Cui, Fengkui; Liang, Xiaoming; Li, Yan

2018-03-01

In process, the research object, the gear rack was selected to study the influence law of rolling method on the deformation force. By the mean of the cold roll forming finite element simulation, the variation regularity of radial and tangential deformation was analysed under different rolling methods. The variation of deformation force of the complete forming racks and the single roll during the steady state under different rolling modes was analyzed. The results show: when upbeating and down beating, radial single point average force is similar, the tangential single point average force gap is bigger, the gap of tangential single point average force is relatively large. Add itionally, the tangential force at the time of direct beating is large, and the dire ction is opposite with down beating. With directly beating, deformation force loading fast and uninstall slow. Correspondingly, with down beating, deformat ion force loading slow and uninstall fast.

Forebody tangential blowing for control at high angles of attack

NASA Technical Reports Server (NTRS)

Kroo, I.; Rock, S.; Roberts, L.

1991-01-01

A feasibility study to determine if the use of tangential leading edge blowing over the forebody could produce effective and practical control of the F-18 HARV aircraft at high angles of attack was conducted. A simplified model of the F-18 configuration using a vortex-lattice model was developed to obtain a better understanding of basic aerodynamic coupling effects and the influence of forebody circulation on lifting surface behavior. The effect of tangential blowing was estimated using existing wind tunnel data on normal forebody blowing and analytical studies of tangential blowing over conical forebodies. Incorporation of forebody blowing into the flight control system was investigated by adding this additional yaw control and sideforce generating actuator into the existing F-18 HARV simulation model. A control law was synthesized using LQG design methods that would schedule blowing rates as a function of vehicle sideslip, angle of attack, and roll and yaw rates.

Measurement of terms and parameters in turbulent models

NASA Technical Reports Server (NTRS)

Sandborn, Virgil A.

1989-01-01

Experimental measurements of the mean and turbulent velocity field in a water flow, turn-around-duct is documented. The small radius of curvature duct experiments were made over a range of Reynolds numbers (based on a duct height of 10 cm) from 70,000 to 500,000. For this particular channel, the flow is dominated by the inertia forces. Use of the local bulk velocity to non-dimensionalize the local velocity was found to limit Reynolds number effects to the regions very close to the wall. Only secondary effects on the flow field were observed when the inlet or exit boundary conditions were altered. The flow over the central two-thirds of the channel was two-dimensional. Mean tangetial and radial velocities, streamlines, pressure distributions, surface shear stress; tangential, radial and lateral turbulent velocities and the Reynolds turbulent shear values are tabulated in other reports. It is evident from the experimental study that a complex numerical modeling technique must be developed to predict the flow in the turn-around-duct. The model must be able to predict relaminarization along the inner-convex-wall. It must also allow for the major increase in turbulence produced by the outer-concave-wall.

Three-dimensional flow visualization and vorticity dynamics in revolving wings

NASA Astrophysics Data System (ADS)

Cheng, Bo; Sane, Sanjay P.; Barbera, Giovanni; Troolin, Daniel R.; Strand, Tyson; Deng, Xinyan

2013-01-01

We investigated the three-dimensional vorticity dynamics of the flows generated by revolving wings using a volumetric 3-component velocimetry system. The three-dimensional velocity and vorticity fields were represented with respect to the base axes of rotating Cartesian reference frames, and the second invariant of the velocity gradient was evaluated and used as a criterion to identify two core vortex structures. The first structure was a composite of leading, trailing, and tip-edge vortices attached to the wing edges, whereas the second structure was a strong tip vortex tilted from leading-edge vortices and shed into the wake together with the vorticity generated at the tip edge. Using the fundamental vorticity equation, we evaluated the convection, stretching, and tilting of vorticity in the rotating wing frame to understand the generation and evolution of vorticity. Based on these data, we propose that the vorticity generated at the leading edge is carried away by strong tangential flow into the wake and travels downwards with the induced downwash. The convection by spanwise flow is comparatively negligible. The three-dimensional flow in the wake also exhibits considerable vortex tilting and stretching. Together these data underscore the complex and interconnected vortical structures and dynamics generated by revolving wings.

Injection Characteristics of Non-Swirling and Swirling Annular Liquid Sheets

NASA Technical Reports Server (NTRS)

Harper, Brent (Technical Monitor); Ibrahim, E. A.; McKinney, T. R.

2004-01-01

A simplified mathematical model, based on body-fitted coordinates, is formulated to study the evolution of non-swirling and swirling liquid sheet emanated from an annular nozzle in a quiescent surrounding medium. The model provides predictions of sheet trajectory, thickness and velocity at various liquid mass flow rates and liquid-swirler angles. It is found that a non-swirling annular sheet converges toward its centerline and assumes a bell shape as it moves downstream from the nozzle. The bell radius, and length are more pronounced at higher liquid mass flow rates. The thickness of the non-swirling annular sheet increases while its stream-wise velocity decreases with an increase in mass flow rate. The introduction of swirl results in the formation of a diverging hollow-cone sheet. The hollow-cone divergence from its centerline is enhanced by an increase in liquid mass flow rate or liquid-swirler angle. The hollow- cone sheet its radius, curvature and stream-wise velocity increase while its thickness and tangential velocity decrease as a result of increasing the mass flow rate or liquid-swirler angle. The present results are compared with previous studies and conclusions are drawn.

Integrated economic and experimental framework for screening of primary recovery technologies for high cell density CHO cultures

PubMed Central

Popova, Daria; Stonier, Adam; Pain, David; Titchener‐Hooker, Nigel J.

2016-01-01

Abstract Increases in mammalian cell culture titres and densities have placed significant demands on primary recovery operation performance. This article presents a methodology which aims to screen rapidly and evaluate primary recovery technologies for their scope for technically feasible and cost‐effective operation in the context of high cell density mammalian cell cultures. It was applied to assess the performance of current (centrifugation and depth filtration options) and alternative (tangential flow filtration (TFF)) primary recovery strategies. Cell culture test materials (CCTM) were generated to simulate the most demanding cell culture conditions selected as a screening challenge for the technologies. The performance of these technology options was assessed using lab scale and ultra scale‐down (USD) mimics requiring 25–110mL volumes for centrifugation and depth filtration and TFF screening experiments respectively. A centrifugation and depth filtration combination as well as both of the alternative technologies met the performance selection criteria. A detailed process economics evaluation was carried out at three scales of manufacturing (2,000L, 10,000L, 20,000L), where alternative primary recovery options were shown to potentially provide a more cost‐effective primary recovery process in the future. This assessment process and the study results can aid technology selection to identify the most effective option for a specific scenario. PMID:27067803

Differential Velocity between Solar Wind Protons and Alpha Particles in Pressure Balance Structures

NASA Technical Reports Server (NTRS)

Yamauchi, Yohei; Suess, Steven T.; Steinberg, John T.; Sakurai, Takashi

2004-01-01

Pressure balance structures (PBSs) are a common high-plasma beta feature in high-latitude, high-speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high-speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high-speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large-amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high-latitude, high-speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high-speed, high-latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

Differential Velocity Between Solar Wind Protons and Alpha Particles in Pressure Balance Structures

NASA Technical Reports Server (NTRS)

Yamauchi, Y.; Suess, S. T.; Steinberg, J. T.; Sakurai, T.

2003-01-01

Pressure balance structures (PBSs) are a common high plasma beta feature in high latitude, high speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high latitude, high speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high speed, high latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

Tangential flow ultrafiltration for detection of white spot syndrome virus (WSSV) in shrimp pond water.

PubMed

Alavandi, S V; Ananda Bharathi, R; Satheesh Kumar, S; Dineshkumar, N; Saravanakumar, C; Joseph Sahaya Rajan, J

2015-06-15

Water represents the most important component in the white spot syndrome virus (WSSV) transmission pathway in aquaculture, yet there is very little information. Detection of viruses in water is a challenge, since their counts will often be too low to be detected by available methods such as polymerase chain reaction (PCR). In order to overcome this difficulty, viruses in water have to be concentrated from large volumes of water prior to detection. In this study, a total of 19 water samples from aquaculture ecosystem comprising 3 creeks, 10 shrimp culture ponds, 3 shrimp broodstock tanks and 2 larval rearing tanks of shrimp hatcheries and a sample from a hatchery effluent treatment tank were subjected to concentration of viruses by ultrafiltration (UF) using tangential flow filtration (TFF). Twenty to 100l of water from these sources was concentrated to a final volume of 100mL (200-1000 fold). The efficiency of recovery of WSSV by TFF ranged from 7.5 to 89.61%. WSSV could be successfully detected by PCR in the viral concentrates obtained from water samples of three shrimp culture ponds, one each of the shrimp broodstock tank, larval rearing tank, and the shrimp hatchery effluent treatment tank with WSSV copy numbers ranging from 6 to 157mL(-1) by quantitative real time PCR. The ultrafiltration virus concentration technique enables efficient detection of shrimp viral pathogens in water from aquaculture facilities. It could be used as an important tool to understand the efficacy of biosecurity protocols adopted in the aquaculture facility and to carry out epidemiological investigations of aquatic viral pathogens. Copyright © 2015 Elsevier B.V. All rights reserved.

Tangential Flow Filtration of Hemoglobin

PubMed Central

Sun, Guoyong; Harris, David R.

2009-01-01

Bovine and human hemoglobin (bHb and hHb, respectively) was purified from bovine and human red blood cells (bRBCs and hRBCs, respectively) via tangential flow filtration (TFF) in four successive stages. TFF is a fast and simple method to purify Hb from RBCs using filtration through hollow fiber (HF) membranes. Most of the Hb was retained in stage III (100 kDa HF membrane) and displayed methemoglobin levels less than 1%, yielding final concentrations of 318 and 300 mg/mL for bHb and hHb, respectively. Purified Hb exhibited much lower endotoxin levels than their respective RBCs. The purity of Hb was initially assessed via SDS-PAGE, and showed tiny impurity bands for the stage III retentate. The oxygen affinity (P50), and cooperativity coefficient (n) were regressed from the measured oxygen-RBC/Hb equilibrium curves of RBCs and purified Hb. These results suggest that TFF yielded oxygen affinities of bHb and hHb that are comparable to values in the literature. LC-MS was used to measure the molecular weight of the alpha (α) and beta (β) globin chains of purified Hb. No impurity peaks were present in the HPLC chromatograms of purified Hb. The mass of the molecular ions corresponding to the α and β globin chains agreed well with the calculated theoretical mass of the α-and β-globin chains. Taken together, our results demonstrate that HPLC grade Hb can be generated via TFF. In general, this method can be more broadly applied to purify Hb from any source of RBCs. This work is significant, since it outlines a simple method for generating Hb for synthesis and/or formulation of Hb-based oxygen carriers (HBOCs). PMID:19224583

Bendable X-ray Optics at the ALS: Design, Tuning, Performance and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Advanced Light Source, Lawrence Berkeley National Laboratory; Yashchuk, Valeriy V.; Church, Matthew N.

2008-09-08

We review the development at the Advanced Light Source (ALS) of bendable x-ray optics widely used for focusing of beams of soft and hard x-rays. Typically, the focusing is divided in the tangential and sagittal directions into two elliptically cylindrical reflecting elements, the so-called Kirkpatrick-Baez (KB) pair [1]. Because fabrication of elliptical surfaces is complicated, the cost of directly fabricated tangential elliptical cylinders is often prohibitive. This is in contrast to flat optics, that are simpler to manufacture and easier to measure by conventional interferometry. The figure of a flat substrate can be changed by placing torques (couples) at eachmore » end. Equal couples form a tangential cylinder, and unequal couples can approximate a tangential ellipse or parabola. We review the nature of the bending, requirements and approaches to the mechanical design, and describe a technique developed at the ALS Optical Metrology Laboratory (OML) for optimal tuning of bendable mirrors before installation in the beamline [2]. The tuning technique adapts a method previously used to adjust bendable mirrors on synchrotron radiation beamlines [3]. However, in our case, optimal tuning of a bendable mirror is based on surface slope trace data obtained with a slope measuring instrument--in our case, the long trace profiler (LTP). We show that due to the near linearity of the bending problem, the minimal set of data, necessary for tuning of two benders, consists of only three slope traces measured before and after a single adjustment of each bending couple. We provide an algorithm that was used in dedicated software for finding optimal settings for the mirror benders. The algorithm is based on the method of regression analysis with experimentally found characteristic functions of the benders. The resulting approximation to the functional dependence of the desired slope shape provides nearly final settings for the benders. Moreover, the characteristic functions of the benders found in the course of tuning, can be used for retuning of the optics to a new desired shape without removing it from the beamline and re-measuring with the LTP. The result of practical use of the developed technique to precisely tune a KB mirror used at the ALS for micro-focusing is also presented. We also describe a simple ray trace using the profiler data which shows expected performance in the beamline and compare the simulation with experimental data. In summary, we also discuss the next steps in the systematic improvement of optical performance for the application of KB pairs in synchrotron beamlines at the ALS.« less

Dirac equation on a curved surface

NASA Astrophysics Data System (ADS)

Brandt, F. T.; Sánchez-Monroy, J. A.

2016-09-01

The dynamics of Dirac particles confined to a curved surface is examined employing the thin-layer method. We perform a perturbative expansion to first-order and split the Dirac field into normal and tangential components to the surface. In contrast to the known behavior of second order equations like Schrödinger, Maxwell and Klein-Gordon, we find that there is no geometric potential for the Dirac equation on a surface. This implies that the non-relativistic limit does not commute with the thin-layer method. Although this problem can be overcome when second-order terms are retained in the perturbative expansion, this would preclude the decoupling of the normal and tangential degrees of freedom. Therefore, we propose to introduce a first-order term which rescues the non-relativistic limit and also clarifies the effect of the intrinsic and extrinsic curvatures on the dynamics of the Dirac particles.

Review on pressure swirl injector in liquid rocket engine

NASA Astrophysics Data System (ADS)

Kang, Zhongtao; Wang, Zhen-guo; Li, Qinglian; Cheng, Peng

2018-04-01

The pressure swirl injector with tangential inlet ports is widely used in liquid rocket engine. Commonly, this type of pressure swirl injector consists of tangential inlet ports, a swirl chamber, a converging spin chamber, and a discharge orifice. The atomization of the liquid propellants includes the formation of liquid film, primary breakup and secondary atomization. And the back pressure and temperature in the combustion chamber could have great influence on the atomization of the injector. What's more, when the combustion instability occurs, the pressure oscillation could further affects the atomization process. This paper reviewed the primary atomization and the performance of the pressure swirl injector, which include the formation of the conical liquid film, the breakup and atomization characteristics of the conical liquid film, the effects of the rocket engine environment, and the response of the injector and atomization on the pressure oscillation.

Contact analysis and experimental investigation of a linear ultrasonic motor.

PubMed

Lv, Qibao; Yao, Zhiyuan; Li, Xiang

2017-11-01

The effects of surface roughness are not considered in the traditional motor model which fails to reflect the actual contact mechanism between the stator and slider. An analytical model for calculating the tangential force of linear ultrasonic motor is proposed in this article. The presented model differs from the previous spring contact model, the asperities in contact between stator and slider are considered. The influences of preload and exciting voltage on tangential force in moving direction are analyzed. An experiment is performed to verify the feasibility of this proposed model by comparing the simulation results with the measured data. Moreover, the proposed model and spring model are compared. The results reveal that the proposed model is more accurate than spring model. The discussion is helpful for designing and modeling of linear ultrasonic motors. Copyright © 2017 Elsevier B.V. All rights reserved.

Assessing Conifer Ray Parenchyma for Ecological Studies: Pitfalls and Guidelines.

PubMed

von Arx, Georg; Arzac, Alberto; Olano, José M; Fonti, Patrick

2015-01-01

Ray parenchyma is an essential tissue for tree functioning and survival. This living tissue plays a major role for storage and transport of water, nutrients, and non-structural carbohydrates (NSC), thus regulating xylem hydraulics and growth. However, despite the importance of rays for tree carbon and water relations, methodological challenges hamper knowledge about ray intra- and inter-tree variability and its ecological meaning. In this study we provide a methodological toolbox for soundly quantifying spatial and temporal variability of different ray features. Anatomical ray features were surveyed in different cutting planes (cross-sectional, tangential, and radial) using quantitative image analysis on stem-wood micro-sections sampled from 41 mature Scots pines (Pinus sylvestris). The percentage of ray surface (PERPAR), a proxy for ray volume, was compared among cutting planes and between early- and latewood to assess measurement-induced variability. Different tangential ray metrics were correlated to assess their similarities. The accuracy of cross-sectional and tangential measurements for PERPAR estimates as a function of number of samples and the measured wood surface was assessed using bootstrapping statistical technique. Tangential sections offered the best 3D insight of ray integration into the xylem and provided the most accurate estimates of PERPAR, with 10 samples of 4 mm(2) showing an estimate within ±6.0% of the true mean PERPAR (relative 95% confidence interval, CI95), and 20 samples of 4 mm(2) showing a CI95 of ±4.3%. Cross-sections were most efficient for establishment of time series, and facilitated comparisons with other widely used xylem anatomical features. Earlywood had significantly lower PERPAR (5.77 vs. 6.18%) and marginally fewer initiating rays than latewood. In comparison to tangential sections, PERPAR was systematically overestimated (6.50 vs. 4.92%) and required approximately twice the sample area for similar accuracy. Radial cuttings provided the least accurate PERPAR estimates. This evaluation of ray parenchyma in conifers and the presented guidelines regarding data accuracy as a function of measured wood surface and number of samples represent an important methodological reference for ray quantification, which will ultimately improve the understanding of the fundamental role of ray parenchyma tissue for the performance and survival of trees growing in stressed environments.

Assessing Conifer Ray Parenchyma for Ecological Studies: Pitfalls and Guidelines

PubMed Central

von Arx, Georg; Arzac, Alberto; Olano, José M.; Fonti, Patrick

2015-01-01

Ray parenchyma is an essential tissue for tree functioning and survival. This living tissue plays a major role for storage and transport of water, nutrients, and non-structural carbohydrates (NSC), thus regulating xylem hydraulics and growth. However, despite the importance of rays for tree carbon and water relations, methodological challenges hamper knowledge about ray intra- and inter-tree variability and its ecological meaning. In this study we provide a methodological toolbox for soundly quantifying spatial and temporal variability of different ray features. Anatomical ray features were surveyed in different cutting planes (cross-sectional, tangential, and radial) using quantitative image analysis on stem-wood micro-sections sampled from 41 mature Scots pines (Pinus sylvestris). The percentage of ray surface (PERPAR), a proxy for ray volume, was compared among cutting planes and between early- and latewood to assess measurement-induced variability. Different tangential ray metrics were correlated to assess their similarities. The accuracy of cross-sectional and tangential measurements for PERPAR estimates as a function of number of samples and the measured wood surface was assessed using bootstrapping statistical technique. Tangential sections offered the best 3D insight of ray integration into the xylem and provided the most accurate estimates of PERPAR, with 10 samples of 4 mm2 showing an estimate within ±6.0% of the true mean PERPAR (relative 95% confidence interval, CI95), and 20 samples of 4 mm2 showing a CI95 of ±4.3%. Cross-sections were most efficient for establishment of time series, and facilitated comparisons with other widely used xylem anatomical features. Earlywood had significantly lower PERPAR (5.77 vs. 6.18%) and marginally fewer initiating rays than latewood. In comparison to tangential sections, PERPAR was systematically overestimated (6.50 vs. 4.92%) and required approximately twice the sample area for similar accuracy. Radial cuttings provided the least accurate PERPAR estimates. This evaluation of ray parenchyma in conifers and the presented guidelines regarding data accuracy as a function of measured wood surface and number of samples represent an important methodological reference for ray quantification, which will ultimately improve the understanding of the fundamental role of ray parenchyma tissue for the performance and survival of trees growing in stressed environments. PMID:26635842

Molecular-dynamics study on characteristics of energy and tangential momentum accommodation coefficients

NASA Astrophysics Data System (ADS)

Yamaguchi, Hiroki; Matsuda, Yu; Niimi, Tomohide

2017-07-01

Gas-surface interaction is studied by the molecular dynamics method to investigate qualitatively characteristics of accommodation coefficients. A large number of trajectories of gas molecules colliding to and scattering from a surface are statistically analyzed to calculate the energy (thermal) accommodation coefficient (EAC) and the tangential momentum accommodation coefficient (TMAC). Considering experimental measurements of the accommodation coefficients, the incident velocities are stochastically sampled to represent a bulk condition. The accommodation coefficients for noble gases show qualitative coincidence with experimental values. To investigate characteristics of these accommodation coefficients in detail, the gas-surface interaction is parametrically studied by varying the molecular mass of gas, the gas-surface interaction strength, and the molecular size of gas, one by one. EAC increases with increasing every parameter, while TMAC increases with increasing the interaction strength, but decreases with increasing the molecular mass and the molecular size. Thus, contradictory results in experimentally measured TMAC for noble gases could result from the difference between the surface conditions employed in the measurements in the balance among the effective parameters of molecular mass, interaction strength, and molecular size, due to surface roughness and/or adsorbed molecules. The accommodation coefficients for a thermo-fluid dynamics field with a temperature difference between gas and surface and a bulk flow at the same time are also investigated.

A new model of cavern diameter based on a validated CFD study on stirring of a highly shear-thinning fluid.

PubMed

Story, Anna; Jaworski, Zdzisław

2017-01-01

Results of numerical simulations of momentum transfer for a highly shear-thinning fluid (0.2% Carbopol) in a stirred tank equipped with a Prochem Maxflo T type impeller are presented. The simulation results were validated using LDA data and both tangential and axial force measurements in the laminar and early transitional flow range. A good agreement between the predicted and experimental results of the local fluid velocity components was found. From the predicted and experimental values of both tangential and axial forces, the power number, Po , and thrust number, Th , were also calculated. Values of the absolute relative deviations were below 4.0 and 10.5%, respectively, for Po and Th , which confirms a satisfactory agreement with experiments. An intensive mixing zone, known as cavern, was observed near the impeller. In this zone, the local values of fluid velocity, strain rate, Metzner-Otto coefficient, shear stress and intensity of energy dissipation were all characterized by strong variability. Based on the results of experimental study a new model using non-dimensional impeller force number was proposed to predict the cavern diameter. Comparative numerical simulations were also carried out for a Newtonian fluid (water) and their results were similarly well verified using LDA measurements, as well as experimental power number values.

Contact problem on indentation of an elastic half-plane with an inhomogeneous coating by a flat punch in the presence of tangential stresses on a surface

NASA Astrophysics Data System (ADS)

Volkov, Sergei S.; Vasiliev, Andrey S.; Aizikovich, Sergei M.; Sadyrin, Evgeniy V.

2018-05-01

Indentation of an elastic half-space with functionally graded coating by a rigid flat punch is studied. The half-plane is additionally subjected to distributed tangential stresses. Tangential stresses are represented in a form of Fourier series. The problem is reduced to the solution of two dual integral equations over even and odd functions describing distribution of unknown normal contact stresses. The solutions of these dual integral equations are constructed by the bilateral asymptotic method. Approximated analytical expressions for contact normal stresses are provided.

A role for intermediate radial glia in the tangential expansion of the mammalian cerebral cortex.

PubMed

Reillo, Isabel; de Juan Romero, Camino; García-Cabezas, Miguel Ángel; Borrell, Víctor

2011-07-01

The cerebral cortex of large mammals undergoes massive surface area expansion and folding during development. Specific mechanisms to orchestrate the growth of the cortex in surface area rather than in thickness are likely to exist, but they have not been identified. Analyzing multiple species, we have identified a specialized type of progenitor cell that is exclusive to mammals with a folded cerebral cortex, which we named intermediate radial glia cell (IRGC). IRGCs express Pax6 but not Tbr2, have a radial fiber contacting the pial surface but not the ventricular surface, and are found in both the inner subventricular zone and outer subventricular zone (OSVZ). We find that IRGCs are massively generated in the OSVZ, thus augmenting the numbers of radial fibers. Fanning out of this expanding radial fiber scaffold promotes the tangential dispersion of radially migrating neurons, allowing for the growth in surface area of the cortical sheet. Accordingly, the tangential expansion of particular cortical regions was preceded by high proliferation in the underlying OSVZ, whereas the experimental reduction of IRGCs impaired the tangential dispersion of neurons and resulted in a smaller cortical surface. Thus, the generation of IRGCs plays a key role in the tangential expansion of the mammalian cerebral cortex.

Kalker's algorithm Fastsim solves tangential contact problems with slip-dependent friction and friction anisotropy

NASA Astrophysics Data System (ADS)

Piotrowski, J.

2010-07-01

This paper presents two extensions of Kalker's algorithm Fastsim of the simplified theory of rolling contact. The first extension is for solving tangential contact problems with the coefficient of friction depending on slip velocity. Two friction laws have been considered: with and without recuperation of the static friction. According to the tribological hypothesis for metallic bodies shear failure, the friction law without recuperation of static friction is more suitable for wheel and rail than the other one. Sample results present local quantities inside the contact area (division to slip and adhesion, traction) as well as global ones (creep forces as functions of creepages and rolling velocity). For the coefficient of friction diminishing with slip, the creep forces decay after reaching the maximum and they depend on the rolling velocity. The second extension is for solving tangential contact problems with friction anisotropy characterised by a convex set of the permissible tangential tractions. The effect of the anisotropy has been shown on examples of rolling without spin and in the presence of pure spin for the elliptical set. The friction anisotropy influences tangential tractions and creep forces. Sample results present local and global quantities. Both extensions have been described with the same language of formulation and they may be merged into one, joint algorithm.

A new isocentric technique for exact geometric matching in the radiotherapy of the breast and ipsilateral supraclavicular fossa using dual asymmetric jaws.

PubMed

Romeo, Nando

2012-10-01

In some clinical situations breast or chest wall radiotherapy for cancer is given in association with supraclavicular fossa irradiation. Often the treatment is delivered by two tangential fields to the breast or chest wall and an anterior field that irradiates the supraclavicular region. The tissue between the breast or chest wall and the supraclavicular region may be under or overdosed, because of the junction between the two tangential fields and the anterior field. To present a new isocentric technique for exact geometric matching between the two tangential fields and the anterior field. Patients are positioned with both arms raised. Using three-dimensional trigonometry, two half-fields, with isocenter between the breast and the supraclavicular region, are easily matched. The tangential fields have a collimator rotation to protect the lung without additional shielding. The correct gantry, collimator and couch positions are defined for the anterior field to match the tangential fields. A general formula for exact geometric matching in radiotherapy of the breast and supraclavicular fossa is presented. The method does not require additional shielding to eliminate divergence other than the four independent jaws. The result is simple to implement in modern delivery facilities. Copyright © 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Spiral Flows in Cool-core Galaxy Clusters

NASA Astrophysics Data System (ADS)

Keshet, Uri

2012-07-01

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, ρ ~ r -1 density (or T ~ r 0.4 temperature) radial profile, and ~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 Rb vpropr 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.

Numerical analysis of thermal creep flow in curved channels for designing a prototype of Knudsen micropump

NASA Astrophysics Data System (ADS)

Leontidis, V.; Brandner, J. J.; Baldas, L.; Colin, S.

2012-05-01

The possibility to generate a gas flow inside a channel just by imposing a tangential temperature gradient along the walls without the existence of an initial pressure difference is well known. The gas must be under rarefied conditions, meaning that the system must operate between the slip and the free molecular flow regimes, either at low pressure or/and at micro/nano-scale dimensions. This phenomenon is at the basis of the operation principle of Knudsen pumps, which are actually compressors without any moving parts. Nowadays, gas flows in the slip flow regime through microchannels can be modeled using commercial Computational Fluid Dynamics softwares, because in this regime the compressible Navier-Stokes equations with appropriate boundary conditions are still valid. A simulation procedure has been developed for the modeling of thermal creep flow using ANSYS Fluent®. The implementation of the boundary conditions is achieved by developing User Defined Functions (UDFs) by means of C++ routines. The complete first order velocity slip boundary condition, including the thermal creep effects due to the axial temperature gradient and the effect of the wall curvature, and the temperature jump boundary condition are applied. The developed simulation tool is used for the preliminary design of Knudsen micropumps consisting of a sequence of curved and straight channels.

Unsteady numerical simulation of the flow in the U9 Kaplan turbine model

NASA Astrophysics Data System (ADS)

Javadi, Ardalan; Nilsson, Håkan

2014-03-01

The Reynolds-averaged Navier-Stokes equations with the RNG k-ε turbulence model closure are utilized to simulate the unsteady turbulent flow throughout the whole flow passage of the U9 Kaplan turbine model. The U9 Kaplan turbine model comprises 20 stationary guide vanes and 6 rotating blades (696.3 RPM), working at best efficiency load (0.71 m3/s). The computations are conducted using a general finite volume method, using the OpenFOAM CFD code. A dynamic mesh is used together with a sliding GGI interface to include the effect of the rotating runner. The clearance is included in the guide vane. The hub and tip clearances are also included in the runner. An analysis is conducted of the unsteady behavior of the flow field, the pressure fluctuation in the draft tube, and the coherent structures of the flow. The tangential and axial velocity distributions at three sections in the draft tube are compared against LDV measurements. The numerical result is in reasonable agreement with the experimental data, and the important flow physics close to the hub in the draft tube is captured. The hub and tip vortices and an on-axis forced vortex are captured. The numerical results show that the frequency of the forced vortex in 1/5 of the runner rotation.

Hatch latch mechanism for Spacelab scientific airlock

NASA Technical Reports Server (NTRS)

Terhaar, G. R.

1979-01-01

The requirements, design tradeoff, design, and performance of the Spacelab scientific airlock hatch latching mechanisms are described. At space side the hatch is closed and held against internal airlock/module pressure by 12 tangential overcenter hooks driven by a driver. At module side the hatch is held by 4 hooks driven by rollers running on a cammed driver.

Automated planning of tangential breast intensity-modulated radiotherapy using heuristic optimization.

PubMed

Purdie, Thomas G; Dinniwell, Robert E; Letourneau, Daniel; Hill, Christine; Sharpe, Michael B

2011-10-01

To present an automated technique for two-field tangential breast intensity-modulated radiotherapy (IMRT) treatment planning. A total of 158 planned patients with Stage 0, I, and II breast cancer treated using whole-breast IMRT were retrospectively replanned using automated treatment planning tools. The tools developed are integrated into the existing clinical treatment planning system (Pinnacle(3)) and are designed to perform the manual volume delineation, beam placement, and IMRT treatment planning steps carried out by the treatment planning radiation therapist. The automated algorithm, using only the radio-opaque markers placed at CT simulation as inputs, optimizes the tangential beam parameters to geometrically minimize the amount of lung and heart treated while covering the whole-breast volume. The IMRT parameters are optimized according to the automatically delineated whole-breast volume. The mean time to generate a complete treatment plan was 6 min, 50 s ± 1 min 12 s. For the automated plans, 157 of 158 plans (99%) were deemed clinically acceptable, and 138 of 158 plans (87%) were deemed clinically improved or equal to the corresponding clinical plan when reviewed in a randomized, double-blinded study by one experienced breast radiation oncologist. In addition, overall the automated plans were dosimetrically equivalent to the clinical plans when scored for target coverage and lung and heart doses. We have developed robust and efficient automated tools for fully inversed planned tangential breast IMRT planning that can be readily integrated into clinical practice. The tools produce clinically acceptable plans using only the common anatomic landmarks from the CT simulation process as an input. We anticipate the tools will improve patient access to high-quality IMRT treatment by simplifying the planning process and will reduce the effort and cost of incorporating more advanced planning into clinical practice. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

SU-E-T-373: Evaluation and Reduction of Contralateral Skin /subcutaneous Dose for Tangential Breast Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butson, M; Carroll, S; Whitaker, M

2015-06-15

Purpose: Tangential breast irradiation is a standard treatment technique for breast cancer therapy. One aspect of dose delivery includes dose delivered to the skin caused by electron contamination. This effect is especially important for highly oblique beams used on the medical tangent where the electron contamination deposits dose on the contralateral breast side. This work aims to investigate and predict as well as define a method to reduce this dose during tangential breast radiotherapy. Methods: Analysis and calculation of breast skin and subcutaneous dose is performed using a Varian Eclipse planning system, AAA algorithm for 6MV x-ray treatments. Measurements weremore » made using EBT3 Gafchromic film to verify the accuracy of planning data. Various materials were tested to assess their ability to remove electron contamination on the contralateral breast. Results: Results showed that the Varian Eclipse AAA algorithm could accurately estimate contralateral breast dose in the build-up region at depths of 2mm or deeper. Surface dose was underestimated by the AAA algorithm. Doses up to 12% of applied dose were seen on the contralateral breast surface and up to 9 % at 2mm depth. Due to the nature of this radiation, being mainly low energy electron contamination, a bolus material could be used to reduce this dose to less than 3%. This is accomplished by 10 mm of superflab bolus or by 1 mm of lead. Conclusion: Contralateral breast skin and subcutaneous dose is present for tangential breast treatment and has been measured to be up to 12% of applied dose from the medial tangent beam. This dose is deposited at shallow depths and is accurately calculated by the Eclipse AAA algorithm at depths of 2mm or greater. Bolus material placed over the contralateral can be used to effectively reduce this skin dose.« less

Controlled vortical flow on delta wings through unsteady leading edge blowing

NASA Technical Reports Server (NTRS)

Lee, K. T.; Roberts, Leonard

1990-01-01

The vortical flow over a delta wing contributes an important part of the lift - the so called nonlinear lift. Controlling this vortical flow with its favorable influence would enhance aircraft maneuverability at high angle of attack. Several previous studies have shown that control of the vortical flow field is possible through the use of blowing jets. The present experimental research studies vortical flow control by applying a new blowing scheme to the rounded leading edge of a delta wing; this blowing scheme is called Tangential Leading Edge Blowing (TLEB). Vortical flow response both to steady blowing and to unsteady blowing is investigated. It is found that TLEB can redevelop stable, strong vortices even in the post-stall angle of attack regime. Analysis of the steady data shows that the effect of leading edge blowing can be interpreted as an effective change in angle of attack. The examination of the fundamental time scales for vortical flow re-organization after the application of blowing for different initial states of the flow field is studied. Different time scales for flow re-organization are shown to depend upon the effective angle of attack. A faster response time can be achieved at angles of attack beyond stall by a suitable choice of the initial blowing momentum strength. Consequently, TLEB shows the potential of controlling the vortical flow over a wide range of angles of attack; i.e., in both for pre-stall and post-stall conditions.

Modeling of the motion of the actin filament on the myosin motility assays

NASA Astrophysics Data System (ADS)

Young, Yuan; Shelley, Mike

2007-11-01

In motility assays, cytoskeletal actin filaments (actin filaments) glide over a surface coated with motor proteins, and the different modes of motion provide a simple measure of the force exerted by the motor proteins (Bourdieu, 1995). Motivated by these experiments, we consider the actin filament as a slender, elastic filament immersed in Stokesian flow, driven by a tangential forcing that mimics the force by the motor proteins. We find qualitative agreement on several points between our analysis and simulations and experimental observations. Furthermore, we study the correlation between filament transport and the characteristics of motion with the spatial pattern of motor protein density.

Computer code for gas-liquid two-phase vortex motions: GLVM

NASA Technical Reports Server (NTRS)

Yeh, T. T.

1986-01-01

A computer program aimed at the phase separation between gas and liquid at zero gravity, induced by vortex motion, is developed. It utilizes an explicit solution method for a set of equations describing rotating gas-liquid flows. The vortex motion is established by a tangential fluid injection. A Lax-Wendroff two-step (McCormack's) numerical scheme is used. The program can be used to study the fluid dynamical behavior of the rotational two-phase fluids in a cylindrical tank. It provides a quick/easy sensitivity test on various parameters and thus provides the guidance for the design and use of actual physical systems for handling two-phase fluids.

On the Wind Generation of Water Waves

NASA Astrophysics Data System (ADS)

Bühler, Oliver; Shatah, Jalal; Walsh, Samuel; Zeng, Chongchun

2016-11-01

In this work, we consider the mathematical theory of wind generated water waves. This entails determining the stability properties of the family of laminar flow solutions to the two-phase interface Euler equation. We present a rigorous derivation of the linearized evolution equations about an arbitrary steady solution, and, using this, we give a complete proof of the instability criterion of M iles [16]. Our analysis is valid even in the presence of surface tension and a vortex sheet (discontinuity in the tangential velocity across the air-sea interface). We are thus able to give a unified equation connecting the Kelvin-Helmholtz and quasi-laminar models of wave generation.

Problems of gaseous motion around stars

NASA Technical Reports Server (NTRS)

Huang, S.-S.

1973-01-01

A distinction is drawn between radial and tangential modes of ejection from stars, and the possible flow patterns are described. They are: expanding streams, falling streams, jet streams, circulatory streams, and gaseous envelopes. Motion around Be stars is discussed at some length, as a preliminary to studying more complicated flow in binary systems. The rotational velocity of the Be star is insufficient to form the ring. It appears likely that radial instability is temperature sensitive. Rings and disks in binary systems are discussed from the point of view of periodic orbits for particles within the gravitational field of such a system. The formation of these rings is discussed. The expected relation between rotational velocity of the ring and the orbital period is discussed. The relation of circumstellar streams to period changes is mentioned. Finally, the influence of magnetic fields on the circumstellar material and the system is discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pirrung, Georg; Madsen, Helge; Schreck, Scott

Current fast aeroelastic wind turbine codes suitable for certification lack an induction model for standstill conditions. A trailed vorticity model previously used as addition to a blade element momentum theory based aerodynamic model in normal operation has been extended to allow computing the induced velocities in standstill. The model is validated against analytical results for an elliptical wing in constant inflow and against stand still measurements from the NREL/NASA Phase VI unsteady experiment. The extended model obtains good results in case of the elliptical wing, but underpredicts the steady loading for the Phase VI blade in attached flow. The predictionmore » of the dynamic force coefficient loops from the Phase VI experiment is improved by the trailed vorticity modeling in both attached flow and stall in most cases. The exception is the tangential force coefficient in stall, where the codes and measurements deviate and no clear improvement is visible.« less

Trailed vorticity modeling for aeroelastic wind turbine simulations in stand still

DOE PAGES

Pirrung, Georg; Madsen, Helge; Schreck, Scott

2016-10-03

Current fast aeroelastic wind turbine codes suitable for certification lack an induction model for standstill conditions. A trailed vorticity model previously used as addition to a blade element momentum theory based aerodynamic model in normal operation has been extended to allow computing the induced velocities in standstill. The model is validated against analytical results for an elliptical wing in constant inflow and against stand still measurements from the NREL/NASA Phase VI unsteady experiment. The extended model obtains good results in case of the elliptical wing, but underpredicts the steady loading for the Phase VI blade in attached flow. The predictionmore » of the dynamic force coefficient loops from the Phase VI experiment is improved by the trailed vorticity modeling in both attached flow and stall in most cases. The exception is the tangential force coefficient in stall, where the codes and measurements deviate and no clear improvement is visible.« less

Gas turbine power plant with supersonic shock compression ramps

DOEpatents

Lawlor, Shawn P [Bellevue, WA; Novaresi, Mark A [San Diego, CA; Cornelius, Charles C [Kirkland, WA

2008-10-14

A gas turbine engine. The engine is based on the use of a gas turbine driven rotor having a compression ramp traveling at a local supersonic inlet velocity (based on the combination of inlet gas velocity and tangential speed of the ramp) which compresses inlet gas against a stationary sidewall. The supersonic compressor efficiently achieves high compression ratios while utilizing a compact, stabilized gasdynamic flow path. Operated at supersonic speeds, the inlet stabilizes an oblique/normal shock system in the gasdynamic flow path formed between the rim of the rotor, the strakes, and a stationary external housing. Part load efficiency is enhanced by use of a lean pre-mix system, a pre-swirl compressor, and a bypass stream to bleed a portion of the gas after passing through the pre-swirl compressor to the combustion gas outlet. Use of a stationary low NOx combustor provides excellent emissions results.

Evidence for magnetic field reconnection at the earth's magnetopause

NASA Technical Reports Server (NTRS)

Sonnerup, B. U. O.; Paschmann, G.; Papamastorakis, I.; Sckopke, N.; Haerendel, G.; Bame, S. J.; Asbridge, J. R.; Gosling, J. T.; Russell, C. T.

1981-01-01

Eleven Northern Hemisphere crossings of the dayside magnetopause by the ISEE spacecraft are examined to test the hypothesis that the large plasma flow speeds observed in the magnetopause and boundary layer are the result of the plasma acceleration intrinsic to the magnetic field reconnection process. In several cases energetic magnetospheric particles with the proper flow anisotropy, and in one case, reflected magnetosheath particles, were observed outside the magnetopause but adjacent to it. All results support the reconnection hypothesis. The energetic particles were also used to identify the outer separatrix surface, in one case of which is was possible to conclude from its location relative to the magnetopause that the reconnection site was in the vicinity of the equatorial plane rather than in the cusp. The electric field tangential to the magnetopause is inferred to be in the 0.4-2.8 mV/m range.

Numerical Hydrodynamics in Special Relativity.

PubMed

Martí, José Maria; Müller, Ewald

2003-01-01

This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD). Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions) of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction. Supplementary material is available for this article at 10.12942/lrr-2003-7 and is accessible for authorized users.

A genuinely discontinuous approach for multiphase EHD problems

NASA Astrophysics Data System (ADS)

Natarajan, Mahesh; Desjardins, Olivier

2017-11-01

Electrohydrodynamics (EHD) involves solving the Poisson equation for the electric field potential. For multiphase flows, although the electric field potential is a continuous quantity, due to the discontinuity in the electric permittivity between the phases, additional jump conditions at the interface, for the normal and tangential components of the electric field need to be satisfied. All approaches till date either ignore the jump conditions, or involve simplifying assumptions, and hence yield unconvincing results even for simple test problems. In the present work, we develop a genuinely discontinuous approach for the Poisson equation for multiphase flows using a Finite Volume Unsplit Volume of Fluid method. The governing equation and the jump conditions without assumptions are used to develop the method, and its efficiency is demonstrated by comparison of the numerical results with canonical test problems having exact solutions. Postdoctoral Associate, Department of Mechanical and Aerospace Engineering.

Effect of Combustion-chamber Shape on the Performance of a Prechamber Compression-ignition Engine

NASA Technical Reports Server (NTRS)

Moore, C S; Collins, J H , Jr

1934-01-01

The effect on engine performance of variations in the shape of the prechamber, the shape and direction of the connecting passage, the chamber volume using a tangential passage, the injection system, and the direction od the fuel spray in the chamber was investigated using a 5 by 7 inch single-cylinder compression-ignition engine. The results show that the performance of this engine can be considerably improved by selecting the best combination of variables and incorporating them in a single design. The best combination as determined from these tests consisted of a disk-shaped chamber connected to the cylinder by means of a flared tangential passage. The fuel was injected through a single-orifice nozzle directed normal to the air swirl and in the same plane. At an engine speed of 1,500 r.p.m. and with the theoretical fuel quantity for no excess air, the engine developed a brake mean effective pressure of 115 pounds per square inch with a fuel consumption of 0.49 pound per brake horsepower-hour and an explosion pressure of 820 pounds per square inch. A brake mean effective pressure of 100 pounds per square inch with a brake-fuel consumption of 0.44 pound per horsepower-hour at 1,500 r.p.m. was obtained.

Meninges control tangential migration of hem-derived Cajal-Retzius cells via CXCL12/CXCR4 signaling.

PubMed

Borrell, Víctor; Marín, Oscar

2006-10-01

Cajal-Retzius cells are critical in the development of the cerebral cortex, but little is known about the mechanisms controlling their development. Three focal sources of Cajal-Retzius cells have been identified in mice-the cortical hem, the ventral pallium and the septum-from where they migrate tangentially to populate the cortical surface. Using a variety of tissue culture assays and in vivo manipulations, we demonstrate that the tangential migration of cortical hem-derived Cajal-Retzius cells is controlled by the meninges. We show that the meningeal membranes are a necessary and sufficient substrate for the tangential migration of Cajal-Retzius cells. We also show that the chemokine CXCL12 secreted by the meninges enhances the dispersion of Cajal-Retzius cells along the cortical surface, while retaining them within the marginal zone in a CXCR4-dependent manner. Thus, the meningeal membranes are fundamental in the development of Cajal-Retzius cells and, hence, in the normal development of the cerebral cortex.

A system to measure minute hydraulic permeability of nanometer scale devices in a non-destructive manner

NASA Astrophysics Data System (ADS)

Smith, Ross A.; Fleischman, Aaron J.; Fissell, William H.; Zorman, Christian A.; Roy, Shuvo

2011-04-01

We report an automated system for measuring the hydraulic permeability of nanoporous membranes in a tangential-flow configuration. The system was designed and built specifically for micromachined silicon nanoporous membranes (SNM) with monodisperse slit-shaped pores. These novel membranes are under development for water filtration, artificial organ and drug delivery applications. The filtration cell permits non-destructive testing of the membrane over many remove-modify-replace testing cycles, allowing for direct experiments into the effects of surface modifications on such membranes. The experimental apparatus was validated using microfluidic tubing with circular cross sections that provided similar fluidic resistances to SNM. Further validation was performed with SNM chips for which the pore dimensions were known from scanning electron microscopy measurements. The system was then used to measure the hydraulic permeability of nanoporous membranes before and after surface modification. The system yields measurements with low variance and excellent agreement with predicted values, providing a platform for determining pore sizes in micro/nanofluidic systems with tight pore size distributions to a higher degree of precision than can be achieved with traditional techniques.

A Locally Adaptive Regularization Based on Anisotropic Diffusion for Deformable Image Registration of Sliding Organs

PubMed Central

Pace, Danielle F.; Aylward, Stephen R.; Niethammer, Marc

2014-01-01

We propose a deformable image registration algorithm that uses anisotropic smoothing for regularization to find correspondences between images of sliding organs. In particular, we apply the method for respiratory motion estimation in longitudinal thoracic and abdominal computed tomography scans. The algorithm uses locally adaptive diffusion tensors to determine the direction and magnitude with which to smooth the components of the displacement field that are normal and tangential to an expected sliding boundary. Validation was performed using synthetic, phantom, and 14 clinical datasets, including the publicly available DIR-Lab dataset. We show that motion discontinuities caused by sliding can be effectively recovered, unlike conventional regularizations that enforce globally smooth motion. In the clinical datasets, target registration error showed improved accuracy for lung landmarks compared to the diffusive regularization. We also present a generalization of our algorithm to other sliding geometries, including sliding tubes (e.g., needles sliding through tissue, or contrast agent flowing through a vessel). Potential clinical applications of this method include longitudinal change detection and radiotherapy for lung or abdominal tumours, especially those near the chest or abdominal wall. PMID:23899632

A locally adaptive regularization based on anisotropic diffusion for deformable image registration of sliding organs.

PubMed

Pace, Danielle F; Aylward, Stephen R; Niethammer, Marc

2013-11-01

We propose a deformable image registration algorithm that uses anisotropic smoothing for regularization to find correspondences between images of sliding organs. In particular, we apply the method for respiratory motion estimation in longitudinal thoracic and abdominal computed tomography scans. The algorithm uses locally adaptive diffusion tensors to determine the direction and magnitude with which to smooth the components of the displacement field that are normal and tangential to an expected sliding boundary. Validation was performed using synthetic, phantom, and 14 clinical datasets, including the publicly available DIR-Lab dataset. We show that motion discontinuities caused by sliding can be effectively recovered, unlike conventional regularizations that enforce globally smooth motion. In the clinical datasets, target registration error showed improved accuracy for lung landmarks compared to the diffusive regularization. We also present a generalization of our algorithm to other sliding geometries, including sliding tubes (e.g., needles sliding through tissue, or contrast agent flowing through a vessel). Potential clinical applications of this method include longitudinal change detection and radiotherapy for lung or abdominal tumours, especially those near the chest or abdominal wall.

Hypoglycemic Effect of Chinese Yam (Dioscorea opposita rhizoma) Polysaccharide in Different Structure and Molecular Weight.

PubMed

Li, Qian; Li, Wenzhi; Gao, Qunyu; Zou, Yuxiao

2017-10-01

Three new Chinese yam polysaccharides (namely HSY, huaishanyao in Chinese) were isolated using the methods of boiled water extraction and stepwise ethanolic precipitation, combined with the tangential flow ultrafiltration membrane system. Their molecular weights were determined by high performance gel permeation chromatography. Three type yam polysaccharides in different molecular weight were isolated: HSY-I (>50 kDa), HSY-II (10 to 50 kDa), HSY-III (<10 kDa). The monosaccharide and glycosidic bond links composition were analyzed with GC and Smith degradation. The structure characteristics were further discussed combined with infrared spectrophotometry. Dexamethasone-induced insulin resistance glucose/lipid metabolism diabetic mice model was established to evaluate the hypoglycemic effect of different concentration of HSY and different molecular weights polysaccharide HSY-I, HSY-II, and HSY-III. The results indicated that the HSY polysaccharide mixture, HSY-I and HSY-II had hypoglycemic effect. Three polysaccharides from Chinese yam tuber were isolated in this study. Their structures were characterized and hypoglycemic effects were evaluated. The result clearly identified the benefits of this plant as a healthy functional food. © 2017 Institute of Food Technologists®.

Circulation Control Model Experimental Database for CFD Validation

NASA Technical Reports Server (NTRS)

Paschal, Keith B.; Neuhart, Danny H.; Beeler, George B.; Allan, Brian G.

2012-01-01

A 2D circulation control wing was tested in the Basic Aerodynamic Research Tunnel at the NASA Langley Research Center. A traditional circulation control wing employs tangential blowing along the span over a trailing-edge Coanda surface for the purpose of lift augmentation. This model has been tested extensively at the Georgia Tech Research Institute for the purpose of performance documentation at various blowing rates. The current study seeks to expand on the previous work by documenting additional flow-field data needed for validation of computational fluid dynamics. Two jet momentum coefficients were tested during this entry: 0.047 and 0.114. Boundary-layer transition was investigated and turbulent boundary layers were established on both the upper and lower surfaces of the model. Chordwise and spanwise pressure measurements were made, and tunnel sidewall pressure footprints were documented. Laser Doppler Velocimetry measurements were made on both the upper and lower surface of the model at two chordwise locations (x/c = 0.8 and 0.9) to document the state of the boundary layers near the spanwise blowing slot.

Instability of fluid flow over saturated porous medium

NASA Astrophysics Data System (ADS)

Lyubimova, Tatyana; Kolchanova, Ekaterina; Lyubimov, Dmitry

2013-04-01

We investigate the stability of a fluid flow over a saturated porous medium. The problem is of importance due to the applications to washing out of contaminants from the bottom layer of vegetation, whose properties are similar to the properties of porous medium. In the case of porous medium with the relatively high permeability and porosity the flow involves a part of the fluid saturating the porous medium, with the tangential fluid velocity drop occurring because of the resistance of the solid matrix. The drop leads to the instability analogous to Kelvin-Helmholtz one accompanied by the formation of travelling waves. In the present paper we consider a two-layer system consisting of a pure fluid layer and a porous layer saturated by the fluid located underneath. The system is bounded by a rigid surface at the bottom and a non-deformable free surface at the top. It is under the gravity and inclined at a slight angle to the horizontal axis. The boundary conditions at the interface between the fluid and porous layers are the continuity of fluid velocities and the balance of normal and tangential stresses taking into account the resistance of the solid matrix with respect to the fluid flow near the interface [1-2]. The problem is solved in the framework of the Brinkman model applying the classical shooting algorithm with orthogonalization. The stability boundaries of the stationary fluid flow over the saturated porous medium with respect to the small oscillatory perturbations are obtained for the various values of the Darcy number and the ratio of the porous layer thickness to the full thickness of the system d. It was shown that at the d > 0.5 with increasing the porous layer thickness (or with decreasing of the fluid layer thickness) the stability threshold rises. This is because of the fact that the instability is primarily caused by perturbations located in the fluid layer. At the d < 0.5 the reduction of the porous layer thickness leads to the stability threshold growth. The numerical calculations were also conducted for nonlinear regimes of the flow applying the finite-element method. Flow characteristics are determined at supercritical values of parameters. The work was made under the financial support of Russian Foundation for Basic Research (Grant 12-01-00795). 1. Ochoa-Tapia J. A. and Whitaker S. Momentum transfer at the boundary between a porous medium and a homogeneous fluid-I. Theoretical development. Int. J. Heat Mass Transfer. 1995. N 38. P. 2635-2646. 2. Ochoa-Tapia J. A. and Whitaker S. Momentum transfer at the boundary between a porous medium and a homogeneous fluid-II. Comparison with experiment. Int. J. Heat Mass Transfer. 1995. N 38. P. 2647-2655.

Boundary layer control by a fish: Unsteady laminar boundary layers of rainbow trout swimming in turbulent flows

PubMed Central

Saarenrinne, Pentti

2016-01-01

ABSTRACT The boundary layers of rainbow trout, Oncorhynchus mykiss [0.231±0.016 m total body length (L) (mean±s.d.); N=6], swimming at 1.6±0.09 L s−1 (N=6) in an experimental flow channel (Reynolds number, Re=4×105) with medium turbulence (5.6% intensity) were examined using the particle image velocimetry technique. The tangential flow velocity distributions in the pectoral and pelvic surface regions (arc length from the rostrum, lx=71±8 mm, N=3, and lx=110±13 mm, N=4, respectively) were approximated by a laminar boundary layer model, the Falkner−Skan equation. The flow regime over the pectoral and pelvic surfaces was regarded as a laminar flow, which could create less skin-friction drag than would be the case with turbulent flow. Flow separation was postponed until vortex shedding occurred over the posterior surface (lx=163±22 mm, N=3). The ratio of the body-wave velocity to the swimming speed was in the order of 1.2. This was consistent with the condition of the boundary layer laminarization that had been confirmed earlier using a mechanical model. These findings suggest an energy-efficient swimming strategy for rainbow trout in a turbulent environment. PMID:27815242

Boundary layer control by a fish: Unsteady laminar boundary layers of rainbow trout swimming in turbulent flows.

PubMed

Yanase, Kazutaka; Saarenrinne, Pentti

2016-12-15

The boundary layers of rainbow trout, Oncorhynchus mykiss [0.231±0.016 m total body length (L) (mean±s.d.); N=6], swimming at 1.6±0.09 L s -1 (N=6) in an experimental flow channel (Reynolds number, Re=4×10 5 ) with medium turbulence (5.6% intensity) were examined using the particle image velocimetry technique. The tangential flow velocity distributions in the pectoral and pelvic surface regions (arc length from the rostrum, l x =71±8 mm, N=3, and l x =110±13 mm, N=4, respectively) were approximated by a laminar boundary layer model, the Falkner-Skan equation. The flow regime over the pectoral and pelvic surfaces was regarded as a laminar flow, which could create less skin-friction drag than would be the case with turbulent flow. Flow separation was postponed until vortex shedding occurred over the posterior surface (l x =163±22 mm, N=3). The ratio of the body-wave velocity to the swimming speed was in the order of 1.2. This was consistent with the condition of the boundary layer laminarization that had been confirmed earlier using a mechanical model. These findings suggest an energy-efficient swimming strategy for rainbow trout in a turbulent environment. © 2016. Published by The Company of Biologists Ltd.

Neoclassical parallel flow calculation in the presence of external parallel momentum sources in Heliotron J

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishioka, K.; Nakamura, Y.; Nishimura, S.

A moment approach to calculate neoclassical transport in non-axisymmetric torus plasmas composed of multiple ion species is extended to include the external parallel momentum sources due to unbalanced tangential neutral beam injections (NBIs). The momentum sources that are included in the parallel momentum balance are calculated from the collision operators of background particles with fast ions. This method is applied for the clarification of the physical mechanism of the neoclassical parallel ion flows and the multi-ion species effect on them in Heliotron J NBI plasmas. It is found that parallel ion flow can be determined by the balance between themore » parallel viscosity and the external momentum source in the region where the external source is much larger than the thermodynamic force driven source in the collisional plasmas. This is because the friction between C{sup 6+} and D{sup +} prevents a large difference between C{sup 6+} and D{sup +} flow velocities in such plasmas. The C{sup 6+} flow velocities, which are measured by the charge exchange recombination spectroscopy system, are numerically evaluated with this method. It is shown that the experimentally measured C{sup 6+} impurity flow velocities do not contradict clearly with the neoclassical estimations, and the dependence of parallel flow velocities on the magnetic field ripples is consistent in both results.« less

DEMONSTRATION OF SORBENT INJECTION TECHNOLOGY ON A TANGENTIALLY COAL-FIRED UTILITY BOILER (YORKTOWN LIMB DEMONSTRATION)

EPA Science Inventory

The report summarizes activities conducted and results achieved in an EPA-sponsored program to demonstrate Limestone Injection Multistage Burner (LIMB) technology on a tangentially fired coal-burning utility boiler, Virginia Power's 180-MWe Yorktown Unit No. 2. his successfully d...

Characteristic Length Scales in Fracture Networks: Hydraulic Connectivity through Periodic Hydraulic Tests

NASA Astrophysics Data System (ADS)

Becker, M.; Bour, O.; Le Borgne, T.; Longuevergne, L.; Lavenant, N.; Cole, M. C.; Guiheneuf, N.

2017-12-01

Determining hydraulic and transport connectivity in fractured bedrock has long been an important objective in contaminant hydrogeology, petroleum engineering, and geothermal operations. A persistent obstacle to making this determination is that the characteristic length scale is nearly impossible to determine in sparsely fractured networks. Both flow and transport occur through an unknown structure of interconnected fracture and/or fracture zones making the actual length that water or solutes travel undetermined. This poses difficulties for flow and transport models. For, example, hydraulic equations require a separation distance between pumping and observation well to determine hydraulic parameters. When wells pairs are close, the structure of the network can influence the interpretation of well separation and the flow dimension of the tested system. This issue is explored using hydraulic tests conducted in a shallow fractured crystalline rock. Periodic (oscillatory) slug tests were performed at the Ploemeur fractured rock test site located in Brittany, France. Hydraulic connectivity was examined between three zones in one well and four zones in another, located 6 m apart in map view. The wells are sufficiently close, however, that the tangential distance between the tested zones ranges between 6 and 30 m. Using standard periodic formulations of radial flow, estimates of storativity scale inversely with the square of the separation distance and hydraulic diffusivity directly with the square of the separation distance. Uncertainty in the connection paths between the two wells leads to an order of magnitude uncertainty in estimates of storativity and hydraulic diffusivity, although estimates of transmissivity are unaffected. The assumed flow dimension results in alternative estimates of hydraulic parameters. In general, one is faced with the prospect of assuming the hydraulic parameter and inverting the separation distance, or vice versa. Similar uncertainties exist, for instance, when trying to invert transport parameters from tracer mean residence time. This field test illustrates that when dealing with fracture networks, there is a need for analytic methods of complexity that lie between simple radial solutions and discrete fracture network models.

Direct Determination of the Dependence of the Surface Shear and Dilatational Viscosities on the Thermodynamic State of the Interface: Theoretical Foundations.

PubMed

Lopez; Hirsa

1998-10-01

Recent developments in nonlinear optical techniques for noninvasive probing of a surfactant influenced gas/liquid interface allow for the measurement of the surfactant surface concentration, c, and thus provide new opportunities for the direct determination of its intrinsic viscosities. Here, we present the theoretical foundations, based on the Boussinesq-Scriven surface model without the usual simplification of constant viscosities, for an experimental technique to directly measure the surface shear (µs) and dilatational (kappas) viscosities of a Newtonian interface as functions of the surfactant surface concentration. This ability to directly measure the surfactant concentration permits the use of a simple surface flow for the measurement of the surface viscosities. The requirements are that the interface must be nearly flat, and the flow steady, axisymmetric, and swirling; these flow conditions can be achieved in the deep-channel viscometer driven at relatively fast rates. The tangential stress balance on such an interface leads to two equations; the balance in the azimuthal direction involves only µs and its gradients, and the balance in the radial direction involves both µs and kappas and their gradients. By further exploiting recent developments in laser-based flow measuring techniques, the surface velocities and their gradients which appear in the two equations can be measured directly. The surface tension gradient, which appears in the radial balance equation, is incorporated from the equation of state for the surfactant system and direct measurements of the surfactant surface concentration distribution. The stress balance equations are then ordinary differential equations in the surface viscosities as functions of radial position, which can be readily integrated. Since c is measured as a function of radial position, we then have a direct measurement of µs and kappas as functions of c. Numerical computations of the Navier-Stokes equations are performed to determine the appropriate conditions to achieve the requisite secondary flow. Copyright 1998 Academic Press.

Rotor whirl forces induced by the tip clearance effect in axial flow compressors

NASA Astrophysics Data System (ADS)

Ehrich, F.

1993-10-01

It is now widely recognized that destabilizing forces, tending to generate forward rotor whirl, are generated in axial flow turbines as a result of the nonuniform torque induced by the nonuniform tip-clearance in a deflected rotor-the so called Thomas/Alford force (Thomas, 1958, and Alford, 1965). It is also recognized that there will be a similar effect in axial flow compressors, but qualitative considerations cannot definitively establish the magnitude or even the direction of the induced whirling forces-that is, if they will tend to forward or backward whirl. Applying a 'parallel compressor' model to simulate the operation of a compressor rotor deflected radially in its clearance, it is possible to derive a quantitative estimate of the proportionality factor which relates the Thomas/Alford force in axial flow compressors (i.e., the tangential force generated by a radial deflection of the rotor) to the torque level in the compressor. The analysis makes use of experimental data from the GE Aircraft Engines Low Speed Research Compressor facility comparing the performance of three different axial flow compressors, each with four stages (typical of a mid-block of an aircraft gas turbine compressor) at two different clearances (expressed as a percent of blade length) - CL/L = 1.4 percent and CL/L = 2.8 percent. It is found that the value of Beta is in the range of + 0.27 to - 0.71 in the vicinity of the stages' nominal operating line and + 0.08 to - 1.25 in the vicinity of the stages' operation at peak efficiency. The value of Beta reaches a level of between - 1.16 and - 3.36 as the compressor is operated near its stalled condition. The final result bears a very strong resemblance to the correlation obtained by improvising a normalization of the experimental data of Vance and Laudadio (1984) and a generic relationship to the analytic results of Colding-Jorgensen (1990).

At-line process analytical technology (PAT) for more efficient scale up of biopharmaceutical microfiltration unit operations.

PubMed

Watson, Douglas S; Kerchner, Kristi R; Gant, Sean S; Pedersen, Joseph W; Hamburger, James B; Ortigosa, Allison D; Potgieter, Thomas I

2016-01-01

Tangential flow microfiltration (MF) is a cost-effective and robust bioprocess separation technique, but successful full scale implementation is hindered by the empirical, trial-and-error nature of scale-up. We present an integrated approach leveraging at-line process analytical technology (PAT) and mass balance based modeling to de-risk MF scale-up. Chromatography-based PAT was employed to improve the consistency of an MF step that had been a bottleneck in the process used to manufacture a therapeutic protein. A 10-min reverse phase ultra high performance liquid chromatography (RP-UPLC) assay was developed to provide at-line monitoring of protein concentration. The method was successfully validated and method performance was comparable to previously validated methods. The PAT tool revealed areas of divergence from a mass balance-based model, highlighting specific opportunities for process improvement. Adjustment of appropriate process controls led to improved operability and significantly increased yield, providing a successful example of PAT deployment in the downstream purification of a therapeutic protein. The general approach presented here should be broadly applicable to reduce risk during scale-up of filtration processes and should be suitable for feed-forward and feed-back process control. © 2015 American Institute of Chemical Engineers.

Experimental Investigation of Rotating Stall in a Research Multistage Axial Compressor

NASA Technical Reports Server (NTRS)

Lepicovsky, Jan; Braunscheidel, Edward P.; Welch, Gerard E.

2007-01-01

A collection of experimental data acquired in the NASA low-speed multistage axial compressor while operated in rotating stall is presented in this paper. The compressor was instrumented with high-response wall pressure modules and a static pressure disc probe for in-flow measurement, and a split-fiber probe for simultaneous measurements of velocity magnitude and flow direction. The data acquired to-date have indicated that a single fully developed stall cell rotates about the flow annulus at 50.6% of the rotor speed. The stall phenomenon is substantially periodic at a fixed frequency of 8.29 Hz. It was determined that the rotating stall cell extends throughout the entire compressor, primarily in the axial direction. Spanwise distributions of the instantaneous absolute flow angle, axial and tangential velocity components, and static pressure acquired behind the first rotor are presented in the form of contour plots to visualize different patterns in the outer (midspan to casing) and inner (hub to mid-span) flow annuli during rotating stall. In most of the cases observed, the rotating stall started with a single cell. On occasion, rotating stall started with two emerging stall cells. The root cause of the variable stall cell count is unknown, but is not attributed to operating procedures.

Numerical investigation for entropy generation in hydromagnetic flow of fluid with variable properties and slip

NASA Astrophysics Data System (ADS)

Khan, M. Ijaz; Hayat, Tasawar; Alsaedi, Ahmed

2018-02-01

This modeling and computations present the study of viscous fluid flow with variable properties by a rotating stretchable disk. Rotating flow is generated through nonlinear rotating stretching surface. Nonlinear thermal radiation and heat generation/absorption are studied. Flow is conducting for a constant applied magnetic field. No polarization is taken. Induced magnetic field is not taken into account. Attention is focused on the entropy generation rate and Bejan number. The entropy generation rate and Bejan number clearly depend on velocity and thermal fields. The von Kármán approach is utilized to convert the partial differential expressions into ordinary ones. These expressions are non-dimensionalized, and numerical results are obtained for flow variables. The effects of the magnetic parameter, Prandtl number, radiative parameter, heat generation/absorption parameter, and slip parameter on velocity and temperature fields as well as the entropy generation rate and Bejan number are discussed. Drag forces (radial and tangential) and heat transfer rates are calculated and discussed. Furthermore the entropy generation rate is a decreasing function of magnetic variable and Reynolds number. The Bejan number effect on the entropy generation rate is reverse to that of the magnetic variable. Also opposite behavior of heat transfers is observed for varying estimations of radiative and slip variables.

Boundary-layer and wake measurements on a swept, circulation-control wing

NASA Technical Reports Server (NTRS)

Spaid, Frank W.; Keener, Earl R.

1987-01-01

Wind-tunnel measurements of boundary-layer and wake velocity profiles and surface static pressure distributions are presented for a swept, circulation-control wing. The model is an aspect-ratio-four semispan wing mounted on the tunnel side wall at a sweep angle of 45 deg. A full-span, tangential, rearward blowing, circulation-control slot is located ahead of the trailing edge on the upper surface. Flow surveys were obtained at mid-semispan at freestream Mach numbers of 0.425 and 0.70. Boundary-layer profiles measured on the forward portions of the wing are approximately streamwise and two dimensional. The flow in the vicinity of the jet exit and in the near wake is highly three dimensional. The jet flow near the slot on the Coanda surface is directed normal to the slot. Near-wake surveys show large outboard flows at the center of the wake. At Mach 0.425 and a 5-deg angle of attack, a range of jet-blowing rates was found for which an abrupt transition from incipient separation to attached flow occurs in the boundary layer upstream of the slot. The variation in the lower-surface separation location with blowing rate was determined from boundary-layer measurements at Mach 0.425.

Performance Evaluation of the ONR Axial Waterjet 2 (AxWJ-2)

DTIC Science & Technology

2009-12-01

regions of the blade wakes and near the wall. Pump curves In order to estimate the uncertainty on the measured pump performance, it was first necessary to...velocity well outside the hub wake , but the tangential velocity magnitude and the axial velocity wake deficit are overpredicted near the hub. The...of these plots consists of a grid of 55 * 1024 points. In all three plots, the low-velocity regions six blade wakes are clearly visible, as are the

Exploratory Investigation into the Durability of Beneficial Cold Worked Fastener Hole in Aluminum

NASA Technical Reports Server (NTRS)

Johnson, W. S.; Clark, David A.

1999-01-01

Cold working fastener holes in aluminum alloys is a widely used technique in the aerospace industry for improving the fatigue performance of structures. A compressive tangential stress introduced in the material during the cold working of the hole reduces the natural tendency of the material to crack at the holes under cyclic tensile loading. It is a lucrative technique for the aerospace industry in that it provides an increase in performance without any weight cost.

ALESEP. Part 2: A computer program for the analysis of leading edge separation bubbles on infinite swept wings

NASA Technical Reports Server (NTRS)

Davis, R. L.

1986-01-01

A program called ALESEP is presented for the analysis of the inviscid-viscous interaction which occurs due to the presence of a closed laminar-transitional separation bubble on an airfoil or infinite swept wing. The ALESEP code provides an iterative solution of the boundary layer equations expressed in an inverse formulation coupled to a Cauchy integral representation of the inviscid flow. This interaction analysis is treated as a local perturbation to a known solution obtained from a global airfoil analysis; hence, part of the required input to the ALESEP code are the reference displacement thickness and tangential velocity distributions. Special windward differencing may be used in the reversed flow regions of the separation bubble to accurately account for the flow direction in the discretization of the streamwise convection of momentum. The ALESEP code contains a forced transition model based on a streamwise intermittency function, a natural transition model based on a solution of the integral form of the turbulent kinetic energy equation, and an empirical natural transition model.

Control of vortical separation on conical bodies

NASA Technical Reports Server (NTRS)

Mourtos, Nikos J.; Roberts, Leonard

1987-01-01

In a variety of aeronautical applications, the flow around conical bodies at incidence is of interest. Such applications include, but are not limited to, highly maneuverable aircraft with delta wings, the aerospace plane and nose portions of spike inlets. The theoretical model used has three parts. First, the single line vortex model is used within the framework of slender body theory, to compute the outer inviscid field for specified separation lines. Next, the three dimensional boundary layer is represented by a momentum equation for the cross flow, analogous to that for a plane boundary layer; a von Karman Pohlhausen approximation is applied to solve this equation. The cross flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the position of the vortices and the vortex lift on the body. Lastly, control of separation is achieved by blowing tangentially from a slot located along a cone generator. It is found that for very small blowing coefficients, the separation can be postponed or suppressedy completely.

Numerical study of gravity effects on phase separation in a swirl chamber.

PubMed

Hsiao, Chao-Tsung; Ma, Jingsen; Chahine, Georges L

2016-01-01

The effects of gravity on a phase separator are studied numerically using an Eulerian/Lagrangian two-phase flow approach. The separator utilizes high intensity swirl to separate bubbles from the liquid. The two-phase flow enters tangentially a cylindrical swirl chamber and rotate around the cylinder axis. On earth, as the bubbles are captured by the vortex formed inside the swirl chamber due to the centripetal force, they also experience the buoyancy force due to gravity. In a reduced or zero gravity environment buoyancy is reduced or inexistent and capture of the bubbles by the vortex is modified. The present numerical simulations enable study of the relative importance of the acceleration of gravity on the bubble capture by the swirl flow in the separator. In absence of gravity, the bubbles get stratified depending on their sizes, with the larger bubbles entering the core region earlier than the smaller ones. However, in presence of gravity, stratification is more complex as the two acceleration fields - due to gravity and to rotation - compete or combine during the bubble capture.

A finite volume solver for three dimensional debris flow simulations based on a single calibration parameter

NASA Astrophysics Data System (ADS)

von Boetticher, Albrecht; Turowski, Jens M.; McArdell, Brian; Rickenmann, Dieter

2016-04-01

Debris flows are frequent natural hazards that cause massive damage. A wide range of debris flow models try to cover the complex flow behavior that arises from the inhomogeneous material mixture of water with clay, silt, sand, and gravel. The energy dissipation between moving grains depends on grain collisions and tangential friction, and the viscosity of the interstitial fine material suspension depends on the shear gradient. Thus a rheology description needs to be sensitive to the local pressure and shear rate, making the three-dimensional flow structure a key issue for flows in complex terrain. Furthermore, the momentum exchange between the granular and fluid phases should account for the presence of larger particles. We model the fine material suspension with a Herschel-Bulkley rheology law, and represent the gravel with the Coulomb-viscoplastic rheology of Domnik & Pudasaini (Domnik et al. 2013). Both composites are described by two phases that can mix; a third phase accounting for the air is kept separate to account for the free surface. The fluid dynamics are solved in three dimensions using the finite volume open-source code OpenFOAM. Computational costs are kept reasonable by using the Volume of Fluid method to solve only one phase-averaged system of Navier-Stokes equations. The Herschel-Bulkley parameters are modeled as a function of water content, volumetric solid concentration of the mixture, clay content and its mineral composition (Coussot et al. 1989, Yu et al. 2013). The gravel phase properties needed for the Coulomb-viscoplastic rheology are defined by the angle of repose of the gravel. In addition to this basic setup, larger grains and the corresponding grain collisions can be introduced by a coupled Lagrangian particle simulation. Based on the local Savage number a diffusive term in the gravel phase can activate phase separation. The resulting model can reproduce the sensitivity of the debris flow to water content and channel bed roughness, as illustrated with lab-scale and large-scale experiments. A large-scale natural landslide event down a curved channel is presented to show the model performance at such a scale, calibrated based on the observed surface super-elevation.

Heat Models of Asteroids and the YORP Effect

NASA Astrophysics Data System (ADS)

Golubov, O.

The Yarkovsky-O'Keefe-Radzievski-Paddack (YORP) effect is a torque of light pressure recoil forces acting on an asteroid. We show how this torque can be expressed as an integral of a universal function over the surface of an asteroid, and discuss generalizations of this expression for the case of non-Lambert's scattering laws, non-convex shapes of asteroids, and non-zero heat conductivity. Then we discuss tangential YORP (TYORP), which appears due to uneven heat conductivity in stones lying on the surface of an asteroid. TYORP manifests itself as a drag, which pulls the surface in the tangential direction. Finally, we discuss relation and interplay between the normal YORP and the tangential YORP.

Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

NASA Astrophysics Data System (ADS)

Yan, Xinzhu; Li, Jian; Li, Licheng; Huang, Zhengyong; Wang, Feipeng; Wei, Yuan

2016-10-01

In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

Improved design of a tangential entry cyclone separator for separation of particles from exhaust gas of diesel engine.

PubMed

Mukhopadhyay, N

2011-01-01

An effective design of cyclone separator with tangential inlet is developed applying an equation derived from the correlation of collection efficiency with maximum pressure drop components of the cyclone, which can efficiently remove the particles around 1microm of the exhaust gas of diesel engine.

Rationale and Application of Tangential Scanning to Industrial Inspection of Hardwood Logs

Treesearch

Nand K. Gupta; Daniel L. Schmoldt; Bruce Isaacson

1998-01-01

Industrial computed tomography (CT) inspection of hardwood logs has some unique requirements not found in other CT applications. Sawmill operations demand that large volumes of wood be scanned quickly at high spatial resolution for extended duty cycles. Current CT scanning geometries and commercial systems have both technical and economic [imitations. Tangential...

An investigation of factors affecting wettability of some southern hardwoods

Treesearch

Todd F. Shupe; Chung Y. Hse; Wan H. Wang

1999-01-01

>Wettability of sanded and nonsanded transverse and tangential sections of 22 southern hardwood species were[was] judged by measurement of contact angles using phenol-formaldehyde resins. As ex­pected, contact angle values on transverse sec­tions were higher than on tangential sections for both sanded and...

An investigation of selected factors that influence hardwood wettability

Treesearch

Todd F. Shupe; Chung-Yun Hse; Wan H. Wang

2001-01-01

Wettability of sanded and non-sanded transverse and tangential sections of 22 southern hardwoods species was judged by measurement of contact angles using phenol formaldehyde resins. As expected, contact angle values on transverse sections were higher than those on tangential sections for both sanded and non-sanded surfaces. On sanded surfaces, hackberry had the...

Soft lubrication

NASA Astrophysics Data System (ADS)

Skotheim, Jan; Mahadevan, Laksminarayanan

2004-11-01

We study the lubrication of fluid-immersed soft interfaces and show that elastic deformation couples tangential and normal forces and thus generates lift. We consider materials that deform easily, due to either geometry (e.g a shell) or constitutive properties (e.g. a gel or a rubber), so that the effects of pressure and temperature on the fluid properties may be neglected. Four different system geometries are considered: a rigid cylinder moving tangentially to a soft layer coating a rigid substrate; a soft cylinder moving tangentially to a rigid substrate; a cylindrical shell moving tangentially to a rigid substrate; and finally a journal bearing coated with a thin soft layer, which being a conforming contact allows us to gauge the influence of contact geometry. In addition, for the particular case of a soft layer coating a rigid substrate we consider both elastic and poroelastic material responses. Finally, we consider the role of contact geometry in the context of the journal bearing, a conforming contact. For all these cases we find the same generic behavior: there is an optimal combination of geometric and material parameters that maximizes the dimensionless normal force as a function of the softness.

Revisiting Maxwell’s accommodation coefficient: A study of nitrogen flow in a silica microtube across all flow regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Wenwen, E-mail: wlei@physics.usyd.edu.au; McKenzie, David R., E-mail: d.mckenzie@physics.usyd.edu.au

2014-12-15

Gas flows have been studied quantitatively for more than a hundred years and have relevance in modern fields such as the control of gas inputs to processes, the measurement of leak rates and the separation of gaseous species. Cha and McCoy have derived a convenient formula for the flow of an ideal gas applicable across a wide range of Knudsen numbers (Kn) that approaches the Navier–Stokes equations at small Kn and the Smoluchowski extension of the Knudsen flow equation at large Kn. Smoluchowski’s result relies on the Maxwell definition of the tangential momentum accommodation coefficient α, recently challenged by Aryamore » et al. We measure the flow rate of nitrogen gas in a smooth walled silica tube across a wide range of Knudsen numbers from 0.0048 to 12.4583. We find that the nitrogen flow obeys the Cha and McCoy equation with a large value of α, unlike carbon nanotubes which show flows consistent with a small value of α. Silica capillaries are therefore not atomically smooth. The flow at small Kn has α=0.91 and at large Kn has α close to one, consistent with the redefinition of accommodation coefficient by Arya et al., which also resolves a problem in the literature where there are many observations of α of less than one at small Kn and many equal to one at large Kn. Silica capillaries are an excellent choice for an accurate flow control system. - Highlights: • First experimental study on flow rate across all flow regimes in a well-defined microtube. • Extend Cha and McCoy theory for molecular flow regime. • Demonstrate the Maxwell accommodation coefficient is different in the slip and molecular flow regimes.« less

Flow analysis for the nacelle of an advanced ducted propeller at high angle-of-attack and at cruise with boundary layer control

NASA Technical Reports Server (NTRS)

Hwang, D. P.; Boldman, D. R.; Hughes, C. E.

1994-01-01

An axisymmetric panel code and a three dimensional Navier-Stokes code (used as an inviscid Euler code) were verified for low speed, high angle of attack flow conditions. A three dimensional Navier-Stokes code (used as an inviscid code), and an axisymmetric Navier-Stokes code (used as both viscous and inviscid code) were also assessed for high Mach number cruise conditions. The boundary layer calculations were made by using the results from the panel code or Euler calculation. The panel method can predict the internal surface pressure distributions very well if no shock exists. However, only Euler and Navier-Stokes calculations can provide a good prediction of the surface static pressure distribution including the pressure rise across the shock. Because of the high CPU time required for a three dimensional Navier-Stokes calculation, only the axisymmetric Navier-Stokes calculation was considered at cruise conditions. The use of suction and tangential blowing boundary layer control to eliminate the flow separation on the internal surface was demonstrated for low free stream Mach number and high angle of attack cases. The calculation also shows that transition from laminar flow to turbulent flow on the external cowl surface can be delayed by using suction boundary layer control at cruise flow conditions. The results were compared with experimental data where possible.

Further studies on cortical tangential migration in wild type and Pax-6 mutant mice.

PubMed

Jiménez, D; López-Mascaraque, L; de Carlos, J A; Valverde, F

2002-01-01

In this study we present new data concerning the tangential migration from the medial and lateral ganglionic eminences (MGE and LGE) to the cerebral cortex during development. We have used Calbindin as a useful marker to follow the itinerary of tangential migratory cells during early developmental stages in wild-type and Pax-6 homozygous mutant mice. In the wild-type mice, at early developmental stages, migrating cells advance through the intermediate zone (IZ) and preplate (PP). At more advanced stages, migrating cells were present in the subplate (SP) and cortical plate (CP) to reach the entire developing cerebral cortex. We found that, in the homozygous mutant mice (Pax-6(Sey-Neu)/Pax-6(Sey-Neu)), this tangential migration is severely affected at early developmental stages: migrating cells were absent in the IZ, which were only found some days later, suggesting that in the mutant mice, there is a temporal delay in tangential migration. We have also defined some possible mechanisms to explain certain migratory routes from the basal telencephalon to the cerebral cortex. We describe the existence of two factors, which we consider to be essential for the normal migration; the first one is the cell adhesion molecule PSA-NCAM, whose role in other migratory systems is well known. The second factor is Robo-2, whose expression delimits a channel for the passage of migratory cells from the basal telencephalon to the cerebral cortex.

A technique for treating local breast cancer using a single set-up point and asymmetric collimation.

PubMed

Rosenow, U F; Valentine, E S; Davis, L W

1990-07-01

Using both pairs of asymmetric jaws of a linear accelerator local-regional breast cancer may be treated from a single set-up point. This point is placed at the abutment of the supraclavicular fields with the medial and lateral tangential fields. Positioning the jaws to create a half-beam superiorly permits treatment of the supraclavicular field. Positioning both jaws asymmetrically at midline to define a single beam in the inferoanterior quadrant permits treatment of the breast from medial and lateral tangents. The highest possible matching accuracy between the supraclavicular and tangential fields is inherently provided by this technique. For treatment of all fields at 100 cm source to axis distance (SAD) the lateral placement and depth of the set-up point may be determined by simulation and simple trigonometry. We elaborate on the clinical procedure. For the technologists treatment of all fields from a single set-up point is simple and efficient. Since the tissue at the superior border of the tangential fields is generally firmer than in mid-breast, greater accuracy in day-to-day set-up is permitted. This technique eliminates the need for table angles even when tangential fields only are planned. Because of half-beam collimation the limit to the tangential field length is 20 cm. Means will be suggested to overcome this limitation in the few cases where it occurs. Another modification is suggested for linear accelerators with only one independent pair of jaws.

Benchmark of the local drift-kinetic models for neoclassical transport simulation in helical plasmas

NASA Astrophysics Data System (ADS)

Huang, B.; Satake, S.; Kanno, R.; Sugama, H.; Matsuoka, S.

2017-02-01

The benchmarks of the neoclassical transport codes based on the several local drift-kinetic models are reported here. Here, the drift-kinetic models are zero orbit width (ZOW), zero magnetic drift, DKES-like, and global, as classified in Matsuoka et al. [Phys. Plasmas 22, 072511 (2015)]. The magnetic geometries of Helically Symmetric Experiment, Large Helical Device (LHD), and Wendelstein 7-X are employed in the benchmarks. It is found that the assumption of E ×B incompressibility causes discrepancy of neoclassical radial flux and parallel flow among the models when E ×B is sufficiently large compared to the magnetic drift velocities. For example, Mp≤0.4 where Mp is the poloidal Mach number. On the other hand, when E ×B and the magnetic drift velocities are comparable, the tangential magnetic drift, which is included in both the global and ZOW models, fills the role of suppressing unphysical peaking of neoclassical radial-fluxes found in the other local models at Er≃0 . In low collisionality plasmas, in particular, the tangential drift effect works well to suppress such unphysical behavior of the radial transport caused in the simulations. It is demonstrated that the ZOW model has the advantage of mitigating the unphysical behavior in the several magnetic geometries, and that it also implements the evaluation of bootstrap current in LHD with the low computation cost compared to the global model.

Interface Instabilities in the Interstellar Medium

NASA Technical Reports Server (NTRS)

Hunter, J. H., Jr.; Siopis, C.; Whitaker, R. W.; Lovelace, R. V. E.

1995-01-01

In the present communication, we reexamine two limiting cases of star-forming mechanisms involving self-gravity, thermodynamics, and velocity fields, that we believe must be ubiquitous in the ISM -- the generally oblique collision of supersonic gas streams or turbulent eddies. The general case of oblique collisions has not yet been examined. However, two limiting cases have been studied in detail: (1) The head-on collision of two identical gas streams that form dense, cool accretion shocks that become unstable and may form Jeans mass clouds, which subsequently undergo collapse. (2) Linearly unstable tangential velocity discontinuities, which result in Kelvin-Helmholtz (K-H) instabilities and related phenomena. The compressible K-H instabilities exhibit rich and unexpected behaviors. Moreover a new thermal-dynamic (T-D) mode was discovered that arises from the coupling of the perturbed thermal behavior and the unperturbed flow. The T-D mode has the curious characteristic that it may be strongly unstable to interface modes when the global modes in either medium are absolutely thermally stable. In the present communication additional models of case 1 are described and discussed, and self-gravity is added in the linear theory of tangential discontinuities, case 2. We prove that self-gravity fundamentally changes the behavior of interfacial modes -- density discontinuities (or steps) are inherently unstable on roughly the free-fall timescale of the denser medium to perturbations of all wavelengths.

Numerical study of flow, combustion and emissions characteristics in a 625 MWe tangentially fired boiler with composition of coal 70% LRC and 30% MRC

NASA Astrophysics Data System (ADS)

Sa'adiyah, Devy; Bangga, Galih; Widodo, Wawan; Ikhwan, Nur

2017-08-01

Tangential fired boiler is one of the methods that can produce more complete combustion. This method applied in Suralaya Power Plant, Indonesia. However, the boiler where supposed to use low rank coal (LRC), but at a given time must be mixed with medium rank coal (MRC) from another unit because of lack of LRC coal. Accordingly to the situation, the study about choosing the right position of LRC and MRC in the burner elevation must be investigated. The composition of coal is 70%LRC / 30%MRC where MRC will be placed at the lower (A & C - Case I)) or higher (E & G - Case II) elevation as the cases in this study. The study is carried out using Computational Fluid Dynamics (CFD) method. The simulation with original case (100%LRC) has a good agreement with the measurement data. As the results, MRC is more recommended at the burner elevation A & C rather than burner elevation E & G because it has closer temperature (880 K) compared with 100%LRC and has smaller local heating area between upper side wall and front wall with the range of temperature 1900 - 2000 K. For emissions, case I has smaller NOx and higher CO2 with 104 ppm and 15,6%. Moreover, it has samller O2 residue with 5,8% due to more complete combustion.

THE HERCULES SATELLITE: A STELLAR STREAM IN THE MILKY WAY HALO?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Nicolas F.; Jin, Shoko, E-mail: martin@mpia.d, E-mail: shoko@ari.uni-heidelberg.d

2010-10-01

We investigate the possibility that the recently discovered Hercules Milky Way (MW) satellite is in fact a stellar stream in formation, thereby explaining its very elongated shape with an axis ratio of 3:1. Under the assumption that Hercules is a stellar stream and that its stars are flowing along the orbit of its progenitor, we find an orbit that would have recently brought the system close enough to the MW to induce its disruption and transformation from a bound dwarf galaxy into a stellar stream. The application of simple analytical techniques to the tentative radial velocity gradient observed in themore » satellite provides tight constraints on the tangential velocity of the system (v{sub t} = -16{sup +6}{sub -22} km s{sup -1} in the Galactic standard of rest). Combined with its large receding velocity, the determined tangential velocity yields an orbit with a small pericentric distance (R{sub peri} = 6{sup +9}{sub -2} kpc). Tidal disruption is therefore a valid scenario for explaining the extreme shape of Hercules. The increase in the mean flattening of dwarf galaxies as one considers fainter systems could therefore be the impact of a few of these satellites not being bound stellar systems dominated by dark matter but, in fact, stellar streams in formation, shedding their stars in the MW's stellar halo.« less

SU-E-T-59: A Novel Multi-Beam Dynamic IMRT with Fixed-Jaw Technique for Left Breast Cancer Patients with Regional Lymph Nodes Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J; Yang, Z; Hu, W

2015-06-15

Purpose: This study was to investigate the dosimetric benefit of a novel intensity modulated radiation therapy (IMRT) technique for irradiating the left breast and regional lymph node (RLN). Methods: The breast and RLN (internal mammary node and periclavicular node) and normal tissue were contoured for 16 consecutive left-sided breast cancer patients previously treated with RT after lumpectomy. Nine equi-spaced fields IMRT (9 -field IMRT), tangential multi-beam IMRT (tangential-IMRT) and IMRT with fixed-jaw technique (FJT-IMRT) were developed and compared with three-dimensional conformal RT (3DCRT). Prescribed dose was 50 Gy in 25 fractions. Dose distributions and dose volume histograms were used tomore » evaluate plans. Results: All IMRTs achieved similar target coverage and substantially reduced heart V30 and V20 compared to the 3DCRT. The average heart mean dose had different changes, which were 9.0Gy for 9-field IMRT, 5.7Gy for tangential-IMRT and 4.2Gy for FJT-IMRT. For the contralateral lung and breast, the 9-field IMRT has the highest mean dose; and the FJT-IMRT and tangential-IMRT had similar lower value. For the thyroid, both 9-field IMRT and FJT-IMRT had similar V30 (20% and 22%) and were significantly lower than that of 3DCRT (34%) and tangential-IMRT (46%). Moreover, the thyroid mean dose of FJT-IMRT is the lowest. For cervical esophagus and humeral head, the FJT-IMRT also had the best sparing. Conclusion: All 9-field IMRT, tangential-IMRT and FJT-IMRT had superiority for targets coverage and substantially reduced the heart volume of high dose irradiation. The FJT-IMRT showed advantages of avoiding the contralateral breast and lung irradiation and decreasing the thyroid, humeral head and cervical esophagus radiation dose at the expense of a slight monitor units (MUs) increasing.« less

3-D Waveform Modeling of the 11 September 2001 World Trade Center Collapse Events in New York City

NASA Astrophysics Data System (ADS)

Yoo, S.; Rhie, J.; Kim, W.

2010-12-01

The seismic signals from collapse of the twin towers of World Trade Center (WTC), NYC were well recorded by the seismographic stations in the northeastern United States. The building collapse can be represented by a vertical single force which does not generate tangential component seismic signals during the source process. The waveforms recorded by the Basking Ridge, NJ (BRNJ) station located due west of the WTC site show that the amplitude on tangential component is negligible and indicates that a vertical single force assumption is valid and the velocity structure is more or less homogeneous along the propagation path. However, 3-component seismograms recorded at Palisades, NY (PAL), which is located 33.8 km due north of the WTC site along the Hudson River (azimuth = 15.2°), show abnormal features. The amplitude on tangential component is larger than on vertical- or on radial-component. This observation may be attributable to the complex energy conversion between Rayleigh and Love waves due to the strong low velocity anomaly associated with unconsolidated sediments under the Hudson River. To test the effects of the low velocity anomaly on the enhanced amplitude in tangential component, we developed a 3D velocity model by considering local geology such as unconsolidated sediment layer, Palisades sill, Triassic sandstone, and crystalline basement and simulated waveforms at PAL. The preliminary synthetic results show that 3D velocity structure can significantly enhance the amplitude in tangential component but it is not as large as the observation. Although a more precise 3D model is required to better explain the observations, our results confirm that the low velocity layer under the Hudson River can enhance the amplitude in tangential component at PAL. This result suggests that a good understanding of the amplitude enhancements for specific event-site pairs may be important to evaluate seismic hazard of metropolitan New York City.

Application of unsteady airfoil theory to rotary wings

NASA Technical Reports Server (NTRS)

Kaza, K. R. V.; Kvaternik, R. G.

1981-01-01

A clarification is presented on recent work concerning the application of unsteady airfoil theory to rotary wings. The application of this theory may be seen as consisting of four steps: (1) the selection of an appropriate unsteady airfoil theory; (2) the resolution of that velocity which is the resultant of aerodynamic and dynamic velocities at a point on the elastic axis into radial, tangential and perpendicular components, and the angular velocity of a blade section about the deformed axis; (3) the expression of lift and pitching moments in terms of the three components; and (4) the derivation of explicit expressions for the components in terms of flight velocity, induced flow, rotor rotational speed, blade motion variables, etc.

Development of computer models for correlating data of film cooling of nose cone under hypersonic flow

NASA Technical Reports Server (NTRS)

Sharpe, L., Jr.

1987-01-01

A 12.5 degree half cone with tangential slot injection at Mach 6.95 was studied to determine the heating rates to the surface of the body near and far downstream of the slot. The cone had a zero degree angle of attack. The heating rates were obtained using a computer program that was developed at NASA-Langley Research Center. The concentration of nitrogen from the slot into the boundary layer was also determined. The ratio of slot to freestream was varied to determine its effect on heating. The numerical heating rates were compared to other correlations obtained from experimental studies as well as theoretical laminar and turbulent results.

Allogeneic cell therapy bioprocess economics and optimization: downstream processing decisions.

PubMed

Hassan, Sally; Simaria, Ana S; Varadaraju, Hemanthram; Gupta, Siddharth; Warren, Kim; Farid, Suzanne S

2015-01-01

To develop a decisional tool to identify the most cost effective process flowsheets for allogeneic cell therapies across a range of production scales. A bioprocess economics and optimization tool was built to assess competing cell expansion and downstream processing (DSP) technologies. Tangential flow filtration was generally more cost-effective for the lower cells/lot achieved in planar technologies and fluidized bed centrifugation became the only feasible option for handling large bioreactor outputs. DSP bottlenecks were observed at large commercial lot sizes requiring multiple large bioreactors. The DSP contribution to the cost of goods/dose ranged between 20-55%, and 50-80% for planar and bioreactor flowsheets, respectively. This analysis can facilitate early decision-making during process development.

Two-phase turbine engines. [using gas-liquid mixture accelerated in nozzles

NASA Technical Reports Server (NTRS)

Elliott, D. G.; Hays, L. G.

1976-01-01

A description is given of a two-phase turbine which utilizes a uniform mixture of gas and liquid accelerated in nozzles of the types reported by Elliott and Weinberg (1968). The mixture acts directly on an axial flow or tangential impulse turbine or is separated into gas and liquid streams which operate separately on a gas turbine and a hydraulic turbine. The basic two-phase cycles are examined, taking into account working fluids, aspects of nozzle expansion, details of turbine cycle operation, and the effect of mixture ratio variation. Attention is also given to two-phase nozzle efficiency, two-phase turbine operating characteristics and efficiencies, separator turbines, and impulse turbine experiments.

Heat transfer in internal channel of a blade: Effects of rotation in a trailing edge cooling system

NASA Astrophysics Data System (ADS)

Andrei, Luca; Andreini, Antonio; Bonanni, Leonardo; Facchini, Bruno

2012-06-01

The aerothermal performance of a trailing edge (TE) internal cooling system of a high pressure gas turbine blade was evaluated under stationary and rotating conditions. The investigated geometry consists of a 30:1 scaled model reproducing a typical wedge shaped discharge duct with one row of enlarged pedestals. The airflow pattern inside the device simulates a highly loaded rotor blade cooling scheme with a 90 [deg] turning flow from the radial hub inlet to the tangential TE outlet. Two different tip configurations were tested, the first one with a completely closed section, the second one with a 5 holes outlet surfaces discharging at ambient pressure. In order to assess rotation effects, a rotating test rig, composed of a rotating arm holding both the PMMA TE model and the instrumentation, was purposely developed and manufactured. A thin Inconel heating foil and wide band Thermo-chromic Liquid Crystals are used to perform steady state heat transfer measurements on the blade pressure side. A rotary joint ensures the pneumatic connection between the blower and the rotating apparatus; moreover several slip rings are used for both instrumentation power supply and thermocouple connection. A parallel CFD analysis involving steady-state RANS modeling was conducted to allow an insight of the flow field inside the redirecting channel and the interpedestal ducts to better interpret the developing vortical structures. Low-Reynolds grid clustering permits to integrate up to the wall both the momentum and the thermal boundary layer. Calculations were performed by means of an in-house developed pressure based solver exploiting the k-ω SST turbulence model implemented in the framework of the open-source finite volume discretization toolbox OpenFOAM®. Analyzed flow conditions correspond to Reynolds number of 20000 in the hub inlet section and angular speed varies to obtain rotation numbers in the range from 0 to 0.3. The orientation of the rotation axis is orthogonal to the heated surface as to resemble a 90 [deg] blade metal angle. Results are reported in terms of detailed heat transfer coefficient 2D maps on the suction side surface as well as spanwise profiles inside the pedestal ducts.

The structure-mechanical relationship of palm vascular tissue.

PubMed

Wang, Ningling; Liu, Wangyu; Huang, Jiale; Ma, Ke

2014-08-01

The structure-mechanical relationship of palm sheath is studied with numerical and experimental methods. The cellular structure of the vascular tissue is rebuilt with an image-based reconstruction method and used to create finite element models. The validity of the models is firstly verified with the results from the tensile tests. Then, the cell walls inside each of the specific regions (fiber cap, vessel, xylem, etc.) are randomly removed to obtain virtually imperfect structures. By comparing the magnitudes of performance degradation in the different imperfect structures, the influences of each region on the overall mechanical performances of the vascular tissue are discussed. The longitudinal stiffness and yield strength are sensitive to the defects in the vessel regions. While in the transverse directions (including the radial and tangential directions), the parenchymatous tissue determines the mechanical properties of the vascular tissue. Moreover, the hydraulic, dynamic response and energy absorption behavior of the vascular tissue are numerically explored. The flexibility of natural palm tissue enhances its impact resistance. Under the quasi-static compression, the cell walls connecting the fiber cap and the vessel dissipate more energy. The dominant role of the fiber cap in the plastic energy dissipation under high-speed impact is observed. And the radially-arranged fiber cap also allows the palm tissue to improve its tangential mechanical performances under hydraulic pressure. Copyright © 2014 Elsevier Ltd. All rights reserved.

Performance evaluation of Maxwell and Cercignani-Lampis gas-wall interaction models in the modeling of thermally driven rarefied gas transport.

PubMed

Liang, Tengfei; Li, Qi; Ye, Wenjing

2013-07-01

A systematic study on the performance of two empirical gas-wall interaction models, the Maxwell model and the Cercignani-Lampis (CL) model, in the entire Knudsen range is conducted. The models are evaluated by examining the accuracy of key macroscopic quantities such as temperature, density, and pressure, in three benchmark thermal problems, namely the Fourier thermal problem, the Knudsen force problem, and the thermal transpiration problem. The reference solutions are obtained from a validated hybrid DSMC-MD algorithm developed in-house. It has been found that while both models predict temperature and density reasonably well in the Fourier thermal problem, the pressure profile obtained from Maxwell model exhibits a trend that opposes that from the reference solution. As a consequence, the Maxwell model is unable to predict the orientation change of the Knudsen force acting on a cold cylinder embedded in a hot cylindrical enclosure at a certain Knudsen number. In the simulation of the thermal transpiration coefficient, although all three models overestimate the coefficient, the coefficient obtained from CL model is the closest to the reference solution. The Maxwell model performs the worst. The cause of the overestimated coefficient is investigated and its link to the overly constrained correlation between the tangential momentum accommodation coefficient and the tangential energy accommodation coefficient inherent in the models is pointed out. Directions for further improvement of models are suggested.

Earlier and greater hand pre-shaping in the elderly: a study based on kinematic analysis of reaching movements to grasp objects.

PubMed

Tamaru, Yoshiki; Naito, Yasuo; Nishikawa, Takashi

2017-11-01

Elderly people are less able to manipulate objects skilfully than young adults. Although previous studies have examined age-related deterioration of hand movements with a focus on the phase after grasping objects, the changes in the reaching phase have not been studied thus far. We aimed to examine whether changes in hand shape patterns during the reaching phase of grasping movements differ between young adults and the elderly. Ten healthy elderly adults and 10 healthy young adults were examined using the Simple Test for Evaluating Hand Functions and kinetic analysis of hand pre-shaping reach-to-grasp tasks. The results were then compared between the two groups. For kinetic analysis, we measured the time of peak tangential velocity of the wrist and the inter-fingertip distance (the distance between the tips of the thumb and index finger) at different time points. The results showed that the elderly group's performance on the Simple Test for Evaluating Hand Functions was significantly lower than that of the young adult group, irrespective of whether the dominant or non-dominant hand was used, indicating deterioration of hand movement in the elderly. The peak tangential velocity of the wrist in either hand appeared significantly earlier in the elderly group than in the young adult group. The elderly group also showed larger inter-fingertip distances with arch-like fingertip trajectories compared to the young adult group for all object sizes. To perform accurate prehension, elderly people have an earlier peak tangential velocity point than young adults. This allows for a longer adjustment time for reaching and grasping movements and for reducing errors in object prehension by opening the hand and fingers wider. Elderly individuals gradually modify their strategy based on previous successes and failures during daily living to compensate for their decline in dexterity and operational capabilities. © 2017 Japanese Psychogeriatric Society.

Simulation of Dose to Surrounding Normal Structures in Tangential Breast Radiotherapy Due to Setup Error

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakar, Ramachandran; Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi; Department of Radiology, All India Institute of Medical Sciences, New Delhi

Setup error plays a significant role in the final treatment outcome in radiotherapy. The effect of setup error on the planning target volume (PTV) and surrounding critical structures has been studied and the maximum allowed tolerance in setup error with minimal complications to the surrounding critical structure and acceptable tumor control probability is determined. Twelve patients were selected for this study after breast conservation surgery, wherein 8 patients were right-sided and 4 were left-sided breast. Tangential fields were placed on the 3-dimensional-computed tomography (3D-CT) dataset by isocentric technique and the dose to the PTV, ipsilateral lung (IL), contralateral lung (CLL),more » contralateral breast (CLB), heart, and liver were then computed from dose-volume histograms (DVHs). The planning isocenter was shifted for 3 and 10 mm in all 3 directions (X, Y, Z) to simulate the setup error encountered during treatment. Dosimetric studies were performed for each patient for PTV according to ICRU 50 guidelines: mean doses to PTV, IL, CLL, heart, CLB, liver, and percentage of lung volume that received a dose of 20 Gy or more (V20); percentage of heart volume that received a dose of 30 Gy or more (V30); and volume of liver that received a dose of 50 Gy or more (V50) were calculated for all of the above-mentioned isocenter shifts and compared to the results with zero isocenter shift. Simulation of different isocenter shifts in all 3 directions showed that the isocentric shifts along the posterior direction had a very significant effect on the dose to the heart, IL, CLL, and CLB, which was followed by the lateral direction. The setup error in isocenter should be strictly kept below 3 mm. The study shows that isocenter verification in the case of tangential fields should be performed to reduce future complications to adjacent normal tissues.« less

Gaseous slip flow analysis of a micromachined flow sensor for ultra small flow applications

NASA Astrophysics Data System (ADS)

Jang, Jaesung; Wereley, Steven T.

2007-02-01

The velocity slip of a fluid at a wall is one of the most typical phenomena in microscale gas flows. This paper presents a flow analysis considering the velocity slip in a capacitive micro gas flow sensor based on pressure difference measurements along a microchannel. The tangential momentum accommodation coefficient (TMAC) measurements of a particular channel wall in planar microchannels will be presented while the previous micro gas flow studies have been based on the same TMACs on both walls. The sensors consist of a pair of capacitive pressure sensors, inlet/outlet and a microchannel. The main microchannel is 128.0 µm wide, 4.64 µm deep and 5680 µm long, and operated under nearly atmospheric conditions where the outlet Knudsen number is 0.0137. The sensor was fabricated using silicon wet etching, ultrasonic drilling, deep reactive ion etching (DRIE) and anodic bonding. The capacitance change of the sensor and the mass flow rate of nitrogen were measured as the inlet-to-outlet pressure ratio was varied from 1.00 to 1.24. The measured maximum mass flow rate was 3.86 × 10-10 kg s-1 (0.019 sccm) at the highest pressure ratio tested. As the pressure difference increased, both the capacitance of the differential pressure sensor and the flow rate through the main microchannel increased. The laminar friction constant f sdot Re, an important consideration in sensor design, varied from the incompressible no-slip case and the mass sensitivity and resolution of this sensor were discussed. Using the current slip flow formulae, a microchannel with much smaller mass flow rates can be designed at the same pressure ratios.

Determination for the Entrapment Criterion of Non-metallic Inclusions by the Solidification Front During Steel Centrifugal Continuous Casting

NASA Astrophysics Data System (ADS)

Wang, Qiangqiang; Zhang, Lifeng

2016-06-01

In the current study, the three-dimensional fluid flow, heat transfer, and solidification in steel centrifugal continuous casting strands were simulated. The volume of fluid model was used to solve the multiphase phenomena between the molten steel and the air. The entrapment and final distribution of inclusions in the solidified shell were studied with the discussion on the effect of rotation behavior of the caster system. Main results indicate that after applying the rotation of the shell, the fluid flow transformed from a recirculation flow to a rotation flow in the mold region and was driven to flow around in the casting direction. As the distance below the meniscus increased, the distribution of the tangential speed of the flow and the centrifugal force along one diameter of the strand became symmetrical gradually. The jet flow from the nozzle hardly impinged on the same location on the shell due to the rotation of the shell during solidification. Thus, the shell thickness on the same height was uniform around, and the thinning shell and a hot spot on the surface of shell were avoided. Both of the measurement and the calculation about the distribution of oxide inclusions along the radial direction indicated the number of inclusions at the side and the center was more than that at the quarter on the cross section of billet. With a larger diameter, inclusions tended to be entrapped toward the center area of the billet.

Electrokinetic framework of dielectrophoretic deposition devices

NASA Astrophysics Data System (ADS)

Burg, Brian R.; Bianco, Vincenzo; Schneider, Julian; Poulikakos, Dimos

2010-06-01

Numerical modeling and experiments are performed investigating the properties of a dielectrophoresis-based deposition device, in order to establish the electrokinetic framework required to understand the effects of applied inhomogeneous electric fields while moving particles to desired locations. By capacitively coupling electrodes to a conductive substrate, the controlled large-scale parallel dielectrophoretic assembly of nanostructures in individually accessible devices at a high integration density is accomplished. Thermal gradients in the solution, which give rise to local permittivity and conductivity changes, and velocity fields are solved by coupling electric, thermal, and fluid-mechanical equations. The induced electrothermal flow (ETF) causes vortices above the electrode gap, attracting particles, such as single-walled carbon nanotubes (SWNTs), before they are trapped by the dielectrophoretic force and deposit across the electrodes. Long-range carbon nanotube transport is governed by hydrodynamic effects, while local trapping is dominated by dielectrophoretic forces in low concentration SWNT dispersions. Results show that by decreasing the ac frequency ac electroosmosis on the metallic electrodes occurs due to the emergence of an electric double layer, disturbing the initial flow pattern of the system. By superimposing a dc potential offset, a generated tangential electroosmotic fluid flow in the dielectric electrode gap also disrupts the ETF. Capacitive coupling is most efficient in the high frequency regime where it is the dominating impedance contribution. Understanding the occurrence and interaction of these different effects, including a self-limiting integration mechanism for individual nanostructures, allows an increased deposition yield at overall lower electric field strengths through a prudent choice of electric field parameters. The findings provide important avenues toward gentler particle handling, without direct current throughput, a relevant aspect for limiting process effects during device fabrication, all while increasing dielectrophoretic deposition efficiency in nanostructured networks.

Long-term scar quality after hydrosurgical versus conventional debridement of deep dermal burns (HyCon trial): study protocol for a randomized controlled trial.

PubMed

Legemate, Catherine M; Goei, Harold; Middelkoop, Esther; Oen, Irma M M H; Nijhuis, Tim H J; Kwa, Kelly A A; van Zuijlen, Paul P M; Beerthuizen, Gerard I J M; Nieuwenhuis, Marianne K; van Baar, Margriet E; van der Vlies, Cornelis H

2018-04-19

Deep dermal burns require tangential excision of non-viable tissue and skin grafting to improve wound healing and burn-scar quality. Tangential excision is conventionally performed with a knife, but during the last decade hydrosurgery has become popular as a new tool for tangential excision. Hydrosurgery is generally thought to be a more precise and controlled manner of burn debridement leading to preservation of viable tissue and, therefore, better scar quality. Although scar quality is considered to be one of the most important outcomes in burn surgery today, no randomized controlled study has compared the effect of these two common treatment modalities with scar quality as a primary outcome. The aim of this study is, therefore, to compare long-term scar quality after hydrosurgical versus conventional tangential excision in deep dermal burns. A multicenter, randomized, intra-patient, controlled trial will be conducted in the Dutch burn centers of Rotterdam, Beverwijk, and Groningen. All patients with deep dermal burns that require excision and grafting are eligible. Exclusion criteria are: a burn wound < 50 cm 2 , total body surface area (TBSA) burned > 30%, full-thickness burns, chemical or electrical burns, infected wounds (clinical symptoms in combination with positive wound swabs), insufficient knowledge of the Dutch or English language, patients that are unlikely to comply with requirements of the study protocol and follow-up, and patients who are (temporarily) incompetent because of sedation and/or intubation. A total of 137 patients will be included. Comparable wound areas A and B will be appointed, randomized and either excised conventionally with a knife or with the hydrosurgery system. The primary outcome is scar quality measured by the observer score of the Patient and Observer Scar Assessment Scale (POSAS); a subjective scar-assessment instrument, consisting of two separate six-item scales (observer and patient) that are both scored on a 10-point rating scale. This study will contribute to the optimal surgical treatment of patients with deep dermal burn wounds. Dutch Trial Register, NTR6232 . Registered on 23 January 2017.

Three-dimensional flow in radial turbomachinery and its impact on design

NASA Technical Reports Server (NTRS)

Tan, Choon S.; Hawthorne, William

1993-01-01

In the two papers on the 'Theory of Blade Design for Large Deflections' published in 1984, a new inverse design technique was presented for designing the shape of turbomachinery blades in three-dimensional flow. The technique involves the determination of the blade profile from the specification of a distribution of the product of the radius and the pitched averaged tangential velocity (i.e., r bar-V(sub theta), the mean swirl schedule) within the bladed region. This is in contrast to the conventional inverse design technique for turbomachinery blading in two dimensional flow in which the blade surface pressure or velocity distribution is specified and the blade profile determined as a result; this is feasible in two-dimensional flow because the streamlines along the blade surfaces are known a priori. However, in three-dimensional flow, the stream surface is free to deform within the blade passage so that the streamlines on the blade surfaces are not known a priori; thus it is difficult and not so useful to prescribe the blade surface pressure or velocity distribution and determine the resulting blade profile. It therefore seems logical to prescribe the swirl schedule within the bladed region for designing a turbomachinery blade profile in three-dimensional flow. Furthermore, specifying r bar-V(sub theta) has the following advantages: (1) it is related to the circulation around the blade (i.e., it is an aerodynamic quantity); (2) the work done or extracted is approximately proportional to the overall change in r bar-V(sub theta) across a given blade row (Euler turbine equation); and (3) the rate of change of r bar-V(sub theta) along the mean streamline at the blade is related to the pressure jump across the blade and therefore the blade loading. Since the publications of those two papers, the technique has been applied to the design of a low speed as well as a high speed radial inflow turbine (for turbocharger applications) both of which showed definite improvements in performance over that of wheels of conventional designs, the design study of a high pressure ratio radial inflow turbine with and without splitter blades.

Prehension synergies: A study of digit force adjustments to the continuously varied load force exerted on a partially constrained hand-held object

PubMed Central

Friedman, Jason; Latash, Mark L.; Zatsiorsky, Vladimir M.

2009-01-01

We examined how the digit forces adjust when a load force acting on a hand-held object continuously varies. The subjects were required to hold the handle still while a linearly increasing and then decreasing force was applied to the handle. The handle was constrained, such that it could only move up and down, and rotate about a horizontal axis. In addition the moment arm of the thumb tangential force was 1.5 times the moment arm of the virtual finger (VF, an imagined finger with the mechanical action equal to that of the four fingers) force. Unlike the situation when there are equal moment arms, the experimental setup forced the subjects to choose between (a) sharing equally the increase in load force between the thumb and virtual finger but generating a moment of tangential force, which had to be compensated by negatively covarying the moment due to normal forces, or (b) sharing unequally the load force increase between the thumb and VF but preventing generation of a moment of tangential forces. We found that different subjects tended to use one of these two strategies. These findings suggest that the selection by the CNS of prehension synergies at the VF-thumb level with respect to the moment of force are non-obligatory and reflect individual subject preferences. This unequal sharing of the load by the tangential forces, in contrast to the previously observed equal sharing, suggests that the invariant feature of prehension may be a correlated increase in tangential forces rather than an equal increase. PMID:19554319

A comparative analysis of permanent magnet-type bearingless synchronous motors for fully magnetically levitated rotors

NASA Astrophysics Data System (ADS)

Charpentier, J. F.; Lemarquand, G.

1998-06-01

Radial instability of synchronous motors is important data to design magnetic bearings. Moreover, original motor structures must be proposed to decrease the instability. In this article, four structures with a permanent magnet rotor, six poles, and the same main mechanical dimensions are analyzed and compared. The first concerns a rotor with six tiles of permanent magnets radially magnetized and adhered to an iron core. The second is a rotor with six axial permanent magnets tangentially magnetized and separated by iron pole pieces, where the shaft is amagnetic. The third design proposes a rotor with six contiguous tiles of permanent magnets tangentially magnetized and an amagnetic shaft. In the fourth structure each north pole is made up of two contiguous tiles of permanent magnets tangentially magnetized in opposite direction and each south pole is made up of an iron pole piece. The shaft of this structure is amagnetic. The stator structure and the currents in stator windings produce a six poles flux distribution. A finite element method program is employed to study the forces and the torques. The four structures are designed to provide the same motor performance (torque). The radial instability is modeled by outcentering the rotor. The relationships between the radial force and the type of structure are analyzed. The result is that the third structure is the best solution for fully magnetically levitated rotors. It has a small instability and does not generate any disturbing force whose frequency is the double of the rotation frequency. This structure also has good properties to be used as a radial magnetic bearing.

DOUBLE code simulations of emissivities of fast neutrals for different plasma observation view-lines of neutral particle analyzers on the COMPASS tokamak

NASA Astrophysics Data System (ADS)

Mitosinkova, K.; Tomes, M.; Stockel, J.; Varju, J.; Stano, M.

2018-03-01

Neutral particle analyzers (NPA) measure line-integrated energy spectra of fast neutral atoms escaping the tokamak plasma, which are a product of charge-exchange (CX) collisions of plasma ions with background neutrals. They can observe variations in the ion temperature T i of non-thermal fast ions created by additional plasma heating. However, the plasma column which a fast atom has to pass through must be sufficiently short in comparison with the fast atom’s mean-free-path. Tokamak COMPASS is currently equipped with one NPA installed at a tangential mid-plane port. This orientation is optimal for observing non-thermal fast ions. However, in this configuration the signal at energies useful for T i derivation is lost in noise due to the too long fast atoms’ trajectories. Thus, a second NPA is planned to be connected for the purpose of measuring T i. We analyzed different possible view-lines (perpendicular mid-plane, tangential mid-plane, and top view) for the second NPA using the DOUBLE Monte-Carlo code and compared the results with the performance of the present NPA with tangential orientation. The DOUBLE code provides fast-atoms’ emissivity functions along the NPA view-line. The position of the median of these emissivity functions is related to the location from where the measured signal originates. Further, we compared the difference between the real central T i used as a DOUBLE code input and the T iCX derived from the exponential decay of simulated energy spectra. The advantages and disadvantages of each NPA location are discussed.

Science of Water Leaks: Validated Theory for Moisture Flow in Microchannels and Nanochannels.

PubMed

Lei, Wenwen; Fong, Nicole; Yin, Yongbai; Svehla, Martin; McKenzie, David R

2015-10-27

Water is ubiquitous; the science of its transport in micro- and nanochannels has applications in electronics, medicine, filtration, packaging, and earth and planetary science. Validated theory for water vapor and two-phase water flows is a "missing link"; completing it enables us to define and quantify flow in a set of four standard leak configurations with dimensions from the nanoscale to the microscale. Here we report the first measurements of water vapor flow rates through four silica microchannels as a function of humidity, including under conditions when air is present as a background gas. An important finding is that the tangential momentum accommodation coefficient (TMAC) is strongly modified by surface layers of adsorbed water molecules, in agreement with previous work on the TMAC for nitrogen molecules impacting a silica surface in the presence of moisture. We measure enhanced flow rates for two-phase flows in silica microchannels driven by capillary filling. For the measurement of flows in nanochannels we use heavy water mass spectrometry. We construct the theory for the flow rates of the dominant modes of water transport through each of the four standard configurations and benchmark it against our new measurements in silica and against previously reported measurements for nanochannels in carbon nanotubes, carbon nanopipes, and porous alumina. The findings show that all behavior can be described by the four standard leak configurations and that measurements of leak behavior made using other molecules, such as helium, are not reliable. Single-phase water vapor flow is overestimated by a helium measurement, while two-phase flows are greatly underestimated for channels larger than 100 nm or for all channels when boundary slip applies, to an extent that depends on the slip length for the liquid-phase flows.

Analysis of three microscopic characters for separating the wood of Pinus contorta and P. ponderosa

Treesearch

Alex C. Wiedenhoeft; Regis B. Miller; Terra J. Theim

2003-01-01

Three microscopic characters were evaluated for the identification of Pinus contorta and Pinus ponderosa. The tangential diameter of the resin canals, including the epithelium, was compared to the tangential diameter of the entire resin canal complex. The latter measurement was shown to give diagnostic results for these species. Data from the examination of ray...

Transient Electromagnetic Wave Propagation in a Plasma Waveguide

DTIC Science & Technology

2011-10-24

dielectric. The calculation of the propagation characteristics is based upon tangential continuity of the electric and magnetic field components...filament as a time-dependent resistance , we have determined the electron density, the kinetic parameters for electron attachment and recombination, and...wall conductivity simplifies the imposition of the boundary conditions. The tangential component of the electric field and the normal component of the

The quality assessment of radial and tangential neutron radiography beamlines of TRR

NASA Astrophysics Data System (ADS)

Choopan Dastjerdi, M. H.; Movafeghi, A.; Khalafi, H.; Kasesaz, Y.

2017-07-01

To achieve a quality neutron radiographic image in a relatively short exposure time, the neutron radiography beam must be of good quality and relatively high neutron flux. Characterization of a neutron radiography beam, such as determination of the image quality and the neutron flux, is vital for producing quality radiographic images and also provides a means to compare the quality of different neutron radiography facilities. This paper provides a characterization of the radial and tangential neutron radiography beamlines at the Tehran research reactor. This work includes determination of the facilities category according to the American Society for Testing and Materials (ASTM) standards, and also uses the gold foils to determine the neutron beam flux. The radial neutron beam is a Category I neutron radiography facility, the highest possible quality level according to the ASTM. The tangential beam is a Category IV neutron radiography facility. Gold foil activation experiments show that the measured neutron flux for radial beamline with length-to-diameter ratio (L/D) =150 is 6.1× 106 n cm-2 s-1 and for tangential beamline with (L/D)=115 is 2.4× 104 n cm-2 s-1.

Combustion Stability Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants

NASA Technical Reports Server (NTRS)

Hulka, J. R.

2010-01-01

Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion stability analyses of several of the configurations. This paper presents test data and analyses of combustion stability from the recent PCAD-funded test programs at the NASA MSFC. These test programs used swirl coaxial element injectors with liquid oxygen and liquid methane propellants. Oxygen was injected conventionally in the center of the coaxial element, and swirl was provided by tangential entry slots. Injectors with 28-element and 40-element patterns were tested with several configurations of combustion chambers, including ablative and calorimeter spool sections, and several configurations of fuel injection design. Low frequency combustion instability (chug) occurred with both injectors, and high-frequency combustion instability occurred at the first tangential (1T) transverse mode with the 40-element injector. In most tests, a transition between high-amplitude chug with gaseous methane flow and low-amplitude chug with liquid methane flow was readily observed. Chug analyses of both conditions were conducted using techniques from Wenzel and Szuch and from the Rocket Combustor Interactive Design and Analysis (ROCCID) code. The 1T mode instability occurred in several tests and was apparent by high-frequency pressure measurements as well as dramatic increases in calorimeter-measured heat flux throughout the chamber. Analyses of the transverse mode were conducted with ROCCID and empirical methods such as Hewitt d/V. This paper describes the test hardware configurations, test data, analysis methods, and presents results of the various analyses.

Skin friction measurements in high temperature high speed flows

NASA Technical Reports Server (NTRS)

Schetz, J. A.; Diller, Thomas E.; Wicks, A. L.

1992-01-01

An experimental investigation was conducted to measure skin friction along the chamber walls of supersonic combustors. A direct force measurement device was used to simultaneously measure an axial and transverse component of the small tangential shear force passing over a non-intrusive floating element. The floating head is mounted to a stiff cantilever beam arrangement with deflection due to the flow on the order of 0.00254 mm (0.0001 in.). This allowed the instrument to be a non-nulling type. A second gauge was designed with active cooling of the floating sensor head to eliminate non-uniform temperature effects between the sensor head and the surrounding wall. Samples of measurements made in combustor test facilities at NASA Langley Research Center and at the General Applied Science Laboratory (GASL) are presented. Skin friction coefficients between 0.001 - 0.005 were measured dependent on the facility and measurement location. Analysis of the measurement uncertainties indicate an accuracy to within +/- 10-15 percent of the streamwise component.

Use of source distributions for evaluating theoretical aerodynamics of thin finite wings at supersonic speeds

NASA Technical Reports Server (NTRS)

Evvard, John C

1950-01-01

A series of publications on the source-distribution methods for evaluating the aerodynamics of thin wings at supersonic speeds is summarized, extended, and unified. Included in the first part are the deviations of: (a) the linearized partial-differential equation for unsteady flow at a substantially constant Mach number. b) The source-distribution solution for the perturbation-velocity potential that satisfies the boundary conditions of tangential flow at the surface and in the plane of the wing; and (c) the integral equation for determining the strength and the location of sources to describe the interaction effects (as represented by upwash) of the bottom and top wing surfaces through the region between the finite wing boundary and the foremost Mach wave. The second part deals with steady-state thin-wing problems. The third part of the report approximates the integral equation for unsteady upwash and includes a solution of approximate equation. Expressions are then derived to evaluate the load distributions for time-dependent finite-wing motions.

Quasars Probing Galaxies. I. Signatures of Gas Accretion at Redshift z ≈ 0.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Stephanie H.; Martin, Crystal L.; Kacprzak, Glenn G.

2017-02-01

We describe the kinematics of circumgalactic gas near the galactic plane, combining new measurements of galaxy rotation curves and spectroscopy of background quasars. The sightlines pass within 19–93 kpc of the target galaxy and generally detect Mg ii absorption. The Mg ii Doppler shifts have the same sign as the galactic rotation, so the cold gas co-rotates with the galaxy. Because the absorption spans a broader velocity range than disk rotation can explain, we explore simple models for the circumgalactic kinematics. Gas spiraling inwards (near the disk plane) offers a successful description of the observations. An appendix describes the additionmore » of tangential and radial gas flows and illustrates how the sign of the disk inclination produces testable differences in the projected line-of-sight velocity range. This inflow interpretation implies that cold flow disks remain common down to redshift z ≈ 0.2 and prolong star formation by supplying gas to the disk.« less

Ceramic tile expansion engine housing

DOEpatents

Myers, Blake

1995-01-01

An expandable ceramic tile housing for a high temperature engine is disclosed wherein each tile is independently supported in place in an interlocking matrix by retention mechanisms which mechanically couple the individual ceramic tiles to an outer metal support housing while maintaining thermal isolation of the metal housing from the ceramic tiles. The ceramic tiles are formed with either an octagonal front face portion and a square shank portion or a square front face portion with an octagonal shank portion. The length of the sides of the octagonal front face portion on one tile is equal to the length of the sides of the square front face portion of adjoining tiles to permit formation of an interlocking matrix. Fibrous ceramic sealing material may be placed between radial and tangential facing surfaces of adjacent tiles to limit radial gas flow therebetween. Labyrinth-sealed pressure-controlled compartments may be established between the tile housing and the outer metal support housing to control radial gas flow.

Ceramic tile expansion engine housing

DOEpatents

Myers, B.

1995-04-11

An expandable ceramic tile housing for a high temperature engine is disclosed wherein each tile is independently supported in place in an interlocking matrix by retention mechanisms which mechanically couple the individual ceramic tiles to an outer metal support housing while maintaining thermal isolation of the metal housing from the ceramic tiles. The ceramic tiles are formed with either an octagonal front face portion and a square shank portion or a square front face portion with an octagonal shank portion. The length of the sides of the octagonal front face portion on one tile is equal to the length of the sides of the square front face portion of adjoining tiles to permit formation of an interlocking matrix. Fibrous ceramic sealing material may be placed between radial and tangential facing surfaces of adjacent tiles to limit radial gas flow there between. Labyrinth-sealed pressure-controlled compartments may be established between the tile housing and the outer metal support housing to control radial gas flow. 8 figures.

Granular shear flows of flexible rod-like particles

NASA Astrophysics Data System (ADS)

Guo, Y.; Curtis, J.; Wassgren, C.; Ketterhagen, W.; Hancock, B.

2013-06-01

Flexible particles are widely encountered in nature, e.g., stalks of plants, fiberglass particles, and ceramic nanofibers. Early studies indicated that the deformability of particles has a significant impact on the properties of granular materials and fiber suspensions. In this study, shear flows of flexible particles are simulated using the Discrete Element Method (DEM) to explore the effect of particle flexibility on the flow behavior and constitutive laws. A flexible particle is formed by connecting a number of constituent spheres in a straight line using elastic bonds. The forces/moments due to the normal, tangential, bending, and torsional deformation of a bond resist the relative movement between two bonded constituent spheres. The bond stiffness determines how difficult it is to make a particle deform, and the bond damping accounts for the energy dissipation in the particle vibration process. The simulation results show that elastically bonded particles have smaller coefficients of restitution compared to rigidly connected particles, due to the fact that kinetic energy is partially converted to potential energy in a contact between flexible particles. The coefficient of restitution decreases as the bond stiffness decreases and the bond damping coefficient increases. As a result, smaller stresses are obtained for granular flows of the flexible particles with smaller bond stiffness and larger bond damping coefficient.

Arc dynamics of a pulsed DC nitrogen rotating gliding arc discharge

NASA Astrophysics Data System (ADS)

Zhu, Fengsen; Zhang, Hao; Li, Xiaodong; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Tu, Xin

2018-03-01

In this study, a novel pulsed direct current (DC) rotating gliding arc (RGA) plasma reactor co-driven by an external magnetic field and a tangential gas flow has been developed. The dynamic characteristics of the rotating gliding arc have been investigated by means of numerical simulation and experiment. The simulation results show that a highly turbulent vortex flow can be generated at the bottom of the RGA reactor to accelerate the arc rotation after arc ignition, whereas the magnitude of gas velocity declined significantly along the axial direction of the RGA reactor. The calculated arc rotation frequency (14.4 Hz) is reasonably close to the experimental result (18.5 Hz) at a gas flow rate of 10 l min-1. In the presence of an external magnet, the arc rotation frequency is around five times higher than that of the RGA reactor without using a magnet, which suggests that the external magnetic field plays a dominant role in the maintenance of the arc rotation in the upper zone of the RGA reactor. In addition, when the magnet is placed outside the reactor reversely to form a reverse external magnetic field, the arc can be stabilized at a fixed position in the inner wall of the outer electrode at a critical gas flow rate of 16 l min-1.

Linear flow dynamics near a T/NT interface

NASA Astrophysics Data System (ADS)

Teixeira, Miguel; Silva, Carlos

2011-11-01

The characteristics of a suddenly-inserted T/NT interface separating a homogeneous and isotropic shear-free turbulence region from a non-turbulent flow region are investigated using rapid distortion theory (RDT), taking full account of viscous effects. Profiles of the velocity variances, TKE, viscous dissipation rate, turbulence length scales, and pressure statistics are derived, showing very good agreement with DNS. The normalized inviscid flow statistics at the T/NT interface do not depend on the form of the assumed TKE spectrum. In the non-turbulent region, where the flow is irrotational (except within a thin viscous boundary layer), the dissipation rate decays as z-6, where z is distance from the T/NT interface. The mean pressure exhibits a decrease towards the turbulence due to the associated velocity fluctuations, consistent with the generation of a mean entrainment velocity. The vorticity variance and dissipation rate display large maxima at the T/NT interface due to the existing inviscid discontinuities of the tangential velocity, and these maxima are quantitatively related to the thickness of the viscous boundary layer (VBL). At equilibrium, RDT suggests that the thickness of the T/NT interface scales on the Kolmogorov microscale. We acknowledge the financial support of FCT under Project PTDC/EME-MFE/099636/2008.

Measurement of gas species, temperatures, coal burnout, and wall heat fluxes in a 200 MWe lignite-fired boiler with different overfire air damper openings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jianping Jing; Zhengqi Li; Guangkui Liu

Measurements were performed on a 200 MWe, wall-fired, lignite utility boiler. For different overfire air (OFA) damper openings, the gas temperature, gas species concentration, coal burnout, release rates of components (C, H, and N), furnace temperature, and heat flux and boiler efficiency were measured. Cold air experiments for a single burner were conducted in the laboratory. The double-swirl flow pulverized-coal burner has two ring recirculation zones starting in the secondary air region in the burner. As the secondary air flow increases, the axial velocity of air flow increases, the maxima of radial velocity, tangential velocity and turbulence intensity all increase,more » and the swirl intensity of air flow and the size of recirculation zones increase slightly. In the central region of the burner, as the OFA damper opening widens, the gas temperature and CO concentration increase, while the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and coal particles ignite earlier. In the secondary air region of the burner, the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and the gas temperature and CO concentration vary slightly. In the sidewall region, the gas temperature, O{sub 2} concentration, and NOx concentration decrease, while the CO concentration increases and the gas temperature varies slightly. The furnace temperature and heat flux in the main burning region decrease appreciably, but increase slightly in the burnout region. The NOx emission decreases from 1203.6 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 0% to 511.7 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 80% and the boiler efficiency decreases from 92.59 to 91.9%. 15 refs., 17 figs., 3 tabs.« less

Perpendicular blade vortex interaction and its implications for helicopter noise prediction: Wave-number frequency spectra in a trailing vortex for BWI noise prediction

NASA Technical Reports Server (NTRS)

Devenport, William J.; Glegg, Stewart A. L.

1993-01-01

Perpendicular blade vortex interactions are a common occurrence in helicopter rotor flows. Under certain conditions they produce a substantial proportion of the acoustic noise. However, the mechanism of noise generation is not well understood. Specifically, turbulence associated with the trailing vortices shed from the blade tips appears insufficient to account for the noise generated. The hypothesis that the first perpendicular interaction experienced by a trailing vortex alters its turbulence structure in such a way as to increase the acoustic noise generated by subsequent interactions is examined. To investigate this hypothesis a two-part investigation was carried out. In the first part, experiments were performed to examine the behavior of a streamwise vortex as it passed over and downstream of a spanwise blade in incompressible flow. Blade vortex separations between +/- one eighth chord were studied for at a chord Reynolds number of 200,000. Three-component velocity and turbulence measurements were made in the flow from 4 chord lengths upstream to 15 chordlengths downstream of the blade using miniature 4-sensor hot wire probes. These measurements show that the interaction of the vortex with the blade and its wake causes the vortex core to loose circulation and diffuse much more rapidly than it otherwise would. Core radius increases and peak tangential velocity decreases with distance downstream of the blade. True turbulence levels within the core are much larger downstream than upstream of the blade. The net result is a much larger and more intense region of turbulent flow than that presented by the original vortex and thus, by implication, a greater potential for generating acoustic noise. In the second part, the turbulence measurements described above were used to derive the necessary inputs to a Blade Wake Interaction (BWI) noise prediction scheme. This resulted in significantly improved agreement between measurements and calculations of the BWI noise spectrum especially for the spectral peak at low frequencies, which previously was poorly predicted.

On angled bounce-off impact of a drop impinging on a flowing soap film

NASA Astrophysics Data System (ADS)

Basu, Saikat; Yawar, Ali; Concha, Andres; Bandi, M. M.

2017-12-01

Small drops impinging obliquely on thin flowing soap films frequently demonstrate the rare emergence of bulk elastic effects working in-tandem with the more commonplace hydrodynamic interactions. Three collision regimes are observable: (a) drop piercing through the film, (b) it coalescing with the flow, and (c) it bouncing off the film surface. During impact, the drop deforms along with a bulk elastic deformation of the film. For impacts that are close-to-tangential, the bounce-off regime predominates. We outline a reduced order analytical framework assuming a deformable drop and a deformable three-dimensional film, and the idealization invokes a phase-based parametric study. Angular inclination of the film and the ratio of post and pre-impact drop sizes entail the phase parameters. We also perform experiments with vertically descending droplets (constituted from deionized water) impacting against an inclined soap film, flowing under constant pressure head. Model-predicted phase domain for bounce-off compares well to our experimental findings. Additionally, the experiments exhibit momentum transfer to the film in the form of shed vortex dipoles, along with propagation of free surface waves. On consulting prior published work, we note that for locomotion of water-walking insects using an impulsive action, the momentum distribution to the shed vortices and waves are both significant, taking up respectively 2/3 and 1/3 of the imparted streamwise momentum. Considering the visually similar impulse actions, this theory, despite its assumption of a quiescent liquid bath of infinite depth, is applied to the drop bounce-off experiments, and the resultant shed vortex dipole momenta are compared to the momenta of the coherent vortex structures computed from particle imaging velocimetry data. The magnitudes reveal identical order (10-7 N s), suggesting that notwithstanding the disparities, the bounce-off regime may be tapped as a toy analog for impulse-based interfacial biolocomotion.

Control of VR-7 Dynamic Stall by Strong Steady Blowing

NASA Technical Reports Server (NTRS)

Weaver, D.; McAlister, K. W.; Tso, J.

2004-01-01

An experiment was performed in a water tunnel on a Boeing-Vertol VR-7 airfoil to study the effects of tangential blowing over the upper surface. Blowing was applied at the quarter-chord location during sinusoidal pitching oscillations described by alpha = alpha(sub m) + 10 deg sin omega t. Results were obtained for a Reynolds number of 1 x 10(exp 5), mean angles of 10 and 15 deg, reduced frequencies ranging from 0.005 to 0.15, and blowing rates from C(sub mu) = 0.16 to 0.66. Unsteady lift, drag, and pitching moment loads are reported, along with fluorescent-dye flow visualizations. Strong steady blowing was found to prevent the bursting of the leading-edge separation bubble at several test points. When this occurred, the lift was increased significantly, stall was averted, and the shape of the moment response showed a positive damping in pitch. In almost all cases, steady blowing reduced the hysteresis amplitudes present in the loads, but the benefits diminished as the reduced frequency and mean angle of oscillation increased. A limited number of pulsed blowing cases indicated that for low blowing rates, the greatest gains were achieved at F(sup +) = 0.9.

Pickup Ion Dynamics in the Outer Heliosheath Associated with the Growth of Kelvin-Helmholtz Instability at the Heliopause

NASA Astrophysics Data System (ADS)

Tsubouchi, K.

2017-12-01

A discovery of "IBEX ribbon", localized bright emission of energetic neutral atoms, has brought new insights into the plasma environment of its source region beyond the heliosphere. It has been basically established that its geometrical property is associated with the local interstellar magnetic field draped on the heliopause, and pickup ions (PUIs) in the outer heliosheath (OHS) must be its primary source particles. Understanding the PUI dynamics in OHS more in detail is our motivation for this study. We performed two-dimensional hybrid simulations to evaluate the response of PUIs to the structural variation in the heliosheath. We assumed the simulation system such that the background plasma is hot solar wind in the inner heliosheath and cold interstellar plasma in OHS, and the directions of these flows are tangential to the heliopause. Such a situation leads to the growth of Kelvin-Helmholtz instability (KHI), where the plasma mixing and turbulence excitation takes place. We identified that non-stationarity and non-uniformity emerges in the PUI density structure in a specific energy range as KHI process advances. Relevance of these results to the expected observation like IBEX ribbon will be discussed.

Nonlinear Electrostatic Properties of Lunar Dust

NASA Technical Reports Server (NTRS)

Irwin, Stacy A.

2012-01-01

A laboratory experiment was designed to study the induction charging and charge decay characteristics of small dielectric particles, or glass beads. Initially, the goal of the experiment was further understanding of induction charging of lunar dust particles. However, the mechanism of charging became a point of greater interest as the project continued. Within an environmentally-controlled acrylic glove box was placed a large parallel plate capacitor at high-voltage (HV) power supply with reversible polarity. Spherical 1-mm and 0.5-mm glass beads, singly, were placed between the plates, and their behaviors recorded on video and quantified. Nearly a hundred trials at various humidities were performed. The analysis of the results indicated a non-linear relationship between humidity and particle charge exchange time (CET), for both sizes of beads. Further, a difference in CET for top-resting beads and bottom-resting beads hinted at a different charging mechanism than that of simple induction. Results from the I-mm bead trials were presented at several space science and physics conferences in 2008 and 2009, and were published as a Master's thesis in August 2009. Tangential work stemming from this project resulted in presentations at other international conferences in 2010, and selection to attend workshop on granular matter flow 2011.

Stability of plasma cylinder with current in a helical plasma flow

NASA Astrophysics Data System (ADS)

Leonovich, Anatoly S.; Kozlov, Daniil A.; Zong, Qiugang

2018-04-01

Stability of a plasma cylinder with a current wrapped by a helical plasma flow is studied. Unstable surface modes of magnetohydrodynamic (MHD) oscillations develop at the boundary of the cylinder enwrapped by the plasma flow. Unstable eigenmodes can also develop for which the plasma cylinder is a waveguide. The growth rate of the surface modes is much higher than that for the eigenmodes. It is shown that the asymmetric MHD modes in the plasma cylinder are stable if the velocity of the plasma flow is below a certain threshold. Such a plasma flow velocity threshold is absent for the symmetric modes. They are unstable in any arbitrarily slow plasma flows. For all surface modes there is an upper threshold for the flow velocity above which they are stable. The helicity index of the flow around the plasma cylinder significantly affects both the Mach number dependence of the surface wave growth rate and the velocity threshold values. The higher the index, the lower the upper threshold of the velocity jump above which the surface waves become stable. Calculations have been carried out for the growth rates of unstable oscillations in an equilibrium plasma cylinder with current serving as a model of the low-latitude boundary layer (LLBL) of the Earth's magnetic tail. A tangential discontinuity model is used to simulate the geomagnetic tail boundary. It is shown that the magnetopause in the geotail LLBL is unstable to a surface wave (having the highest growth rate) in low- and medium-speed solar wind flows, but becomes stable to this wave in high-speed flows. However, it can remain weakly unstable to the radiative modes of MHD oscillations.

Initial boundary-value problem for the spherically symmetric Einstein equations with fluids with tangential pressure.

PubMed

Brito, Irene; Mena, Filipe C

2017-08-01

We prove that, for a given spherically symmetric fluid distribution with tangential pressure on an initial space-like hypersurface with a time-like boundary, there exists a unique, local in time solution to the Einstein equations in a neighbourhood of the boundary. As an application, we consider a particular elastic fluid interior matched to a vacuum exterior.

Forbidden tangential orbit transfers between intersecting Keplerian orbits

NASA Technical Reports Server (NTRS)

Burns, Rowland E.

1990-01-01

The classical problem of tangential impulse transfer between coplanar Keplerian orbits is addressed. A completely analytic solution which does not rely on sequential calculation is obtained and this solution is used to demonstrate that certain initially chosen angles can produce singularities in the parameters of the transfer orbit. A necessary and sufficient condition for such singularities is that the initial and final orbits intersect.

Algebra and topology for applications to physics

NASA Technical Reports Server (NTRS)

Rozhkov, S. S.

1987-01-01

The principal concepts of algebra and topology are examined with emphasis on applications to physics. In particular, attention is given to sets and mapping; topological spaces and continuous mapping; manifolds; and topological groups and Lie groups. The discussion also covers the tangential spaces of the differential manifolds, including Lie algebras, vector fields, and differential forms, properties of differential forms, mapping of tangential spaces, and integration of differential forms.

A Rotary Flow Channel for Shear Stress Sensor Calibration

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Scott, Michael A.

2004-01-01

A proposed shear sensor calibrator consists of a rotating wheel with the sensor mounted tangential to the rim and positioned in close proximity to the rim. The shear stress generated by the flow at the sensor position is simply tau(sub omega) = (mu)r(omega)/h, where mu is the viscosity of the ambient gas, r the wheel radius, omega the angular velocity of the wheel, and h the width of the gap between the wheel rim and the sensor. With numerical values of mu = 31 (mu)Pa s (neon at room temperature), r = 0.5 m, omega = 754 /s (7200 rpm), and h = 50.8 m, a shear stress of tau(sub omega) = 231 Pa can be generated. An analysis based on one-dimensional flow, with the flow velocity having only an angular component as a function of the axial and radial coordinates, yields corrections to the above simple formula for the curvature of the wheel, flatness of the sensor, and finite width of the wheel. It is assumed that the sensor mount contains a trough (sidewalls) to render a velocity release boundary condition at the edges of the rim. The Taylor number under maximum flow conditions is found to be 62.3, sufficiently low to obviate flow instability. The fact that the parameters entering into the evaluation of the shear stress can be measured to high accuracy with well-defined uncertainties makes the proposed calibrator suitable for a physical standard for shear stress calibration.

Observation and simulation of an optically driven micromotor

NASA Astrophysics Data System (ADS)

Metzger, N. K.; Mazilu, M.; Kelemen, L.; Ormos, P.; Dholakia, K.

2011-04-01

In the realm of low Reynolds number flow there is a need to find methods to pump, move and mix minute amounts of analyte. Interestingly, micro-devices performing such actuation can be initiated by means of the light-matter interaction. Light induced forces and torques are exerted on such micro-objects, which are then driven by the optical gradient or scattering force. Here, different driving geometries can be realized to harness the light induced force. For example, the scattering force enables micro-gears to be operated in a tangential setup where the micromotor rotors are in line with an optical waveguide. The operational geometry we investigate has the advantage that it reduces the complexity of the driving of such a device in a microfluidic environment by delivering the actuating light by means of a waveguide or fiber optic. In this paper we explore the case of a micromotor being driven by a fiber optically delivered light beam. We experimentally investigate how the driving light interacts with and diffracts from the motor, utilizing two-photon imaging. The micromotor rotation rate dependence on the light field parameters is explored. Additionally, a theoretical model based on the paraxial approximation is used to simulate the torque and predict the rotation rate of such a device and compare it with experiment. The results presented show that our model can be used to optimize the micromotor performance and some example motor designs are evaluated.

Concept of modernization of input device of oil and gas separator

NASA Astrophysics Data System (ADS)

Feodorov, A. B.; Afanasov, V. I.; Miroshnikov, R. S.; Bogachev, V. V.

2017-10-01

The process of defoaming in oil production is discussed. This technology is important in oil and gas fields. Today, the technology of separating the gas fraction is based on chemical catalysis. The use of mechanical technologies improves the economics of the process. Modernization of the separator input device is based on the use of long thin tubes. The chosen length of the tubes is two orders of magnitude larger than the diameter. The separation problem is solved by creating a high centrifugal acceleration. The tubes of the input device are connected in parallel and divide the input stream into several arms. The separated fluid flows are directed tangentially into the working tubes to create a vortex motion. The number of tubes connected in parallel is calculated in accordance with the flow rate of the fluid. The connection of the working tubes to the supply line is made in the form of a flange. This connection allows carrying out maintenance without stopping the flow of fluid. An important feature of this device is its high potential for further modernization. It is concerned with the determination of the parameters of the tubes and the connection geometry in the construction of a single product.

Investigation of the Non-Isothermal Convective Mixing of Turbulent, Round, Wall Jets

NASA Astrophysics Data System (ADS)

Kristo, Paul; Kimber, Mark

2017-11-01

The wall jet has become a paradigm for geometrically bounded flows due to the intrinsically difficult nature of the advection promoted by the geometry of the jet, coupled with prompt diffusion from the adjacent wall. Previous experimental investigations have sought to characterize the hydraulic and thermal behavior of such flows, however the physics promoted by parallel coplanar round jets has received inadequate experimental attention. The current effort is comprised of three parallel, coplanar, equidistant round jets issuing vertically downward into a pseudo-unconfined test section. The outer diameters of the jets are placed tangentially along a smooth flat plate. Non-intrusive optical techniques are incorporated for both hydraulic and thermal observations. Preliminary tests provide accurate inlet boundary conditions for each case. Reference metrics are captured during testing to account for ambient effects and readings inside of the test section. By varying the velocity and temperature inlet parameters, insights are drawn regarding the effects on the merging point (MP) and combined point (CP) of both the flow and thermal fields. Velocity fields in the plane normal to the wall yield additional insight into the deceleration caused by dissipation from both the plate and surrounding stagnant fluid.

Slurry atomizer for a coal-feeder and dryer used to provide coal at gasifier pressure

DOEpatents

Loth, John L.; Smith, William C.; Friggens, Gary R.

1982-01-01

The present invention is directed to a coal-water slurry atomizer for use a high-pressure dryer employed in a pumping system utilized to feed coal into a pressurized coal gasifier. The slurry atomizer is provided with a venturi, constant area slurry injection conduit, and a plurality of tangentially disposed steam injection ports. Superheated steam is injected into the atomizer through these ports to provide a vortical flow of the steam, which, in turn, shears slurry emerging from the slurry injection conduit. The droplets of slurry are rapidly dispersed in the dryer through the venturi where the water is vaporized from the slurry by the steam prior to deleterious heating of the coal.

Optimization of a hydrodynamic separator using a multiscale computational fluid dynamics approach.

PubMed

Schmitt, Vivien; Dufresne, Matthieu; Vazquez, Jose; Fischer, Martin; Morin, Antoine

2013-01-01

This article deals with the optimization of a hydrodynamic separator working on the tangential separation mechanism along a screen. The aim of this study is to optimize the shape of the device to avoid clogging. A multiscale approach is used. This methodology combines measurements and computational fluid dynamics (CFD). A local model enables us to observe the different phenomena occurring at the orifice scale, which shows the potential of expanded metal screens. A global model is used to simulate the flow within the device using a conceptual model of the screen (porous wall). After validation against the experimental measurements, the global model was used to investigate the influence of deflectors and disk plates in the structure.

Interface equation and viscosity contrast in Hele-Shaw flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casademunt, J.; Jasnow, D.; Hernandez-Machado, A.

1992-05-20

In this paper, the authors derive an integro-differential equation for the evolution of the interface separating two immiscible viscous fluids in a Hele-Shaw cell with a channel geometry, for arbitrary viscosity contrast. The authors' equation differs from a previous one obtained by a vortex-sheet formulation of the problem, in that the normal component of the interface velocity is formally decoupled from the gauge-dependent tangential part. The result is thus a closed integral equation for the normal velocity. The authors briefly comment on the advantages of such a formulation and implement an alternative computational algorithm based on it. Preliminary numerical resultsmore » confirm a highly inefficient finger competition in the zero viscosity contrast limit.« less

Numerical Investigation of the Formation of a Convective Column and a Fire Tornado by Forest Fires

NASA Astrophysics Data System (ADS)

Grishin, A. M.; Matvienko, O. V.

2014-09-01

Computational modeling of the formation of a convective column by forest fires has been carried out. It has been established that in the case of an unstable atmosphere stratification the basic factor influencing the thermal column formation is the intensification of the processes of turbulent mixing and that at a stable atmosphere stratification a more significant factor determining the convective column formation is the action of the buoyancy force. It has been shown that a swirling flow in the convective column is formed due to the appearance of a tangential velocity component as a consequence of the local circulation arising against the background of large-scale motion owing to the thermal and orographic inhomogeneities of the underlying surface.

Effect on Gaseous Film Cooling of Coolant Injection Through Angled Slots and Normal Holes

NASA Technical Reports Server (NTRS)

Papell, S. Stephen

1960-01-01

A study was made to determine the effect of coolant injection angularity on gaseous film-cooling effectiveness. In the correlation of experimental data an effective injection angle was defined by a vector summation of the coolant and mainstream gas flows. The cosine of this angle was used as a parameter to empirically develop a corrective term to qualify a correlating equation presented in Technical Note D-130 that was limited to tangential injection of the coolant. Data were also obtained for coolant injection through rows of holes normal to the test plate. The slot correlating equation was adapted to fit these data by the definition of an effective slot height. An additional corrective term was then determined to correlate these data.

Swirling midframe flow for gas turbine engine having advanced transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montgomery, Matthew D.; Charron, Richard C.; Rodriguez, Jose L.

A gas turbine engine can-annular combustion arrangement (10), including: an axial compressor (82) operable to rotate in a rotation direction (60); a diffuser (100, 110) configured to receive compressed air (16) from the axial compressor; a plenum (22) configured to receive the compressed air from the diffuser; a plurality of combustor cans (12) each having a combustor inlet (38) in fluid communication with the plenum, wherein each combustor can is tangentially oriented so that a respective combustor inlet is circumferentially offset from a respective combustor outlet in a direction opposite the rotation direction; and an airflow guiding arrangement (80) configuredmore » to impart circumferential motion to the compressed air in the plenum in the direction opposite the rotation direction.« less

Shock-jump conditions in a general medium: weak-solution approach

NASA Astrophysics Data System (ADS)

Forbes, L. K.; Krzysik, O. A.

2017-05-01

General conservation laws are considered, and the concept of a weak solution is extended to the case of an equation involving three space variables and time. Four-dimensional vector calculus is used to develop general jump conditions at a shock wave in the material. To illustrate the use of this result, jump conditions at a shock in unsteady three-dimensional compressible gas flow are presented. It is then proved rigorously that these reduce to the commonly assumed conditions in coordinates normal and tangential to the shock face. A similar calculation is also outlined for an unsteady three-dimensional shock in magnetohydrodynamics, and in a chemically reactive fluid. The technique is available for determining shock-jump conditions in quite general continuous media.

Shock-like structures in the tropical cyclone boundary layer

NASA Astrophysics Data System (ADS)

Williams, Gabriel J.; Taft, Richard K.; McNoldy, Brian D.; Schubert, Wayne H.

2013-06-01

This paper presents high horizontal resolution solutions of an axisymmetric, constant depth, slab boundary layer model designed to simulate the radial inflow and boundary layer pumping of a hurricane. Shock-like structures of increasing intensity appear for category 1-5 hurricanes. For example, in the category 3 case, the u>(∂u/∂r>) term in the radial equation of motion produces a shock-like structure in the radial wind, i.e., near the radius of maximum tangential wind the boundary layer radial inflow decreases from approximately 22 m s-1 to zero over a radial distance of a few kilometers. Associated with this large convergence is a spike in the radial distribution of boundary layer pumping, with updrafts larger than 22 m s-1 at a height of 1000 m. Based on these model results, it is argued that observed hurricane updrafts of this magnitude so close to the ocean surface are attributable to the dry dynamics of the frictional boundary layer rather than moist convective dynamics. The shock-like structure in the boundary layer radial wind also has important consequences for the evolution of the tangential wind and the vertical component of vorticity. On the inner side of the shock the tangential wind tendency is essentially zero, while on the outer side of the shock the tangential wind tendency is large due to the large radial inflow there. The result is the development of a U-shaped tangential wind profile and the development of a thin region of large vorticity. In many respects, the model solutions resemble the remarkable structures observed in the boundary layer of Hurricane Hugo (1989).

Three-dimensional vortex wake structure of flapping wings in hovering flight.

PubMed

Cheng, Bo; Roll, Jesse; Liu, Yun; Troolin, Daniel R; Deng, Xinyan

2014-02-06

Flapping wings continuously create and send vortices into their wake, while imparting downward momentum into the surrounding fluid. However, experimental studies concerning the details of the three-dimensional vorticity distribution and evolution in the far wake are limited. In this study, the three-dimensional vortex wake structure in both the near and far field of a dynamically scaled flapping wing was investigated experimentally, using volumetric three-component velocimetry. A single wing, with shape and kinematics similar to those of a fruitfly, was examined. The overall result of the wing action is to create an integrated vortex structure consisting of a tip vortex (TV), trailing-edge shear layer (TESL) and leading-edge vortex. The TESL rolls up into a root vortex (RV) as it is shed from the wing, and together with the TV, contracts radially and stretches tangentially in the downstream wake. The downwash is distributed in an arc-shaped region enclosed by the stretched tangential vorticity of the TVs and the RVs. A closed vortex ring structure is not observed in the current study owing to the lack of well-established starting and stopping vortex structures that smoothly connect the TV and RV. An evaluation of the vorticity transport equation shows that both the TV and the RV undergo vortex stretching while convecting downwards: a three-dimensional phenomenon in rotating flows. It also confirms that convection and secondary tilting and stretching effects dominate the evolution of vorticity.

Swimming with a cage: low-Reynolds-number locomotion inside a droplet.

PubMed

Reigh, Shang Yik; Zhu, Lailai; Gallaire, François; Lauga, Eric

2017-05-03

Inspired by recent experiments using synthetic microswimmers to manipulate droplets, we investigate the low-Reynolds-number locomotion of a model swimmer (a spherical squirmer) encapsulated inside a droplet of a comparable size in another viscous fluid. Meditated solely by hydrodynamic interactions, the encaged swimmer is seen to be able to propel the droplet, and in some situations both remain in a stable co-swimming state. The problem is tackled using both an exact analytical theory and a numerical implementation based on a boundary element method, with a particular focus on the kinematics of the co-moving swimmer and the droplet in a concentric configuration, and we obtain excellent quantitative agreement between the two. The droplet always moves slower than a swimmer which uses purely tangential surface actuation but when it uses a particular combination of tangential and normal actuations, the squirmer and droplet are able to attain the same velocity and stay concentric for all times. We next employ numerical simulations to examine the stability of their concentric co-movement, and highlight several stability scenarios depending on the particular gait adopted by the swimmer. Furthermore, we show that the droplet reverses the nature of the far-field flow induced by the swimmer: a droplet cage turns a pusher swimmer into a puller, and vice versa. Our work sheds light on the potential development of droplets as self-contained carriers of both chemical content and self-propelled devices for controllable and precise drug deliveries.

A Review of Issues Related to Data Acquisition and Analysis in EEG/MEG Studies.

PubMed

Puce, Aina; Hämäläinen, Matti S

2017-05-31

Electroencephalography (EEG) and magnetoencephalography (MEG) are non-invasive electrophysiological methods, which record electric potentials and magnetic fields due to electric currents in synchronously-active neurons. With MEG being more sensitive to neural activity from tangential currents and EEG being able to detect both radial and tangential sources, the two methods are complementary. Over the years, neurophysiological studies have changed considerably: high-density recordings are becoming de rigueur; there is interest in both spontaneous and evoked activity; and sophisticated artifact detection and removal methods are available. Improved head models for source estimation have also increased the precision of the current estimates, particularly for EEG and combined EEG/MEG. Because of their complementarity, more investigators are beginning to perform simultaneous EEG/MEG studies to gain more complete information about neural activity. Given the increase in methodological complexity in EEG/MEG, it is important to gather data that are of high quality and that are as artifact free as possible. Here, we discuss some issues in data acquisition and analysis of EEG and MEG data. Practical considerations for different types of EEG and MEG studies are also discussed.

Application of TiN/TiO2 coatings on stainless steel: composition and mechanical reliability

NASA Astrophysics Data System (ADS)

Nikolova, M. P.; Genov, A.; Valkov, S.; Yankov, E.; Dechev, D.; Ivanov, N.; Bezdushnyi, R.; Petrov, P.

2018-03-01

The paper reports on the effect of the substrate temperature (350 °C, 380 °C and 420 °C) during reactive magnetron sputtering of a TiN film on the phase composition, texture and mechanical properties of TiN/TiO2 coatings on 304L stainless steel substrates. Pure Ti was used as a cathode source of Ti. The texture and unit cell parameters of both TiN and TiO2 phases of the coating are discussed in relation with the tribological properties and adhesion of the coating. The scratch tests performed showed that the nitride deposited at 380 °C, having the highest unit cell parameter and a predominant (111) texture, possessed the lowest friction coefficient (μ), tangential force and brittleness. The anatase-type TiO2 with predominant (101) pole density and increased c unit cell parameter showed the highest stability on the nitride deposited at 420 °C. The results indicated that the friction coefficient, tangential force and critical forces of fracture could be varied by controlling the coating deposition temperature.

Design of a lightweight, cost effective thimble-like sensor for haptic applications based on contact force sensors.

PubMed

Ferre, Manuel; Galiana, Ignacio; Aracil, Rafael

2011-01-01

This paper describes the design and calibration of a thimble that measures the forces applied by a user during manipulation of virtual and real objects. Haptic devices benefit from force measurement capabilities at their end-point. However, the heavy weight and cost of force sensors prevent their widespread incorporation in these applications. The design of a lightweight, user-adaptable, and cost-effective thimble with four contact force sensors is described in this paper. The sensors are calibrated before being placed in the thimble to provide normal and tangential forces. Normal forces are exerted directly by the fingertip and thus can be properly measured. Tangential forces are estimated by sensors strategically placed in the thimble sides. Two applications are provided in order to facilitate an evaluation of sensorized thimble performance. These applications focus on: (i) force signal edge detection, which determines task segmentation of virtual object manipulation, and (ii) the development of complex object manipulation models, wherein the mechanical features of a real object are obtained and these features are then reproduced for training by means of virtual object manipulation.

Design of a Lightweight, Cost Effective Thimble-Like Sensor for Haptic Applications Based on Contact Force Sensors

PubMed Central

Ferre, Manuel; Galiana, Ignacio; Aracil, Rafael

2011-01-01

This paper describes the design and calibration of a thimble that measures the forces applied by a user during manipulation of virtual and real objects. Haptic devices benefit from force measurement capabilities at their end-point. However, the heavy weight and cost of force sensors prevent their widespread incorporation in these applications. The design of a lightweight, user-adaptable, and cost-effective thimble with four contact force sensors is described in this paper. The sensors are calibrated before being placed in the thimble to provide normal and tangential forces. Normal forces are exerted directly by the fingertip and thus can be properly measured. Tangential forces are estimated by sensors strategically placed in the thimble sides. Two applications are provided in order to facilitate an evaluation of sensorized thimble performance. These applications focus on: (i) force signal edge detection, which determines task segmentation of virtual object manipulation, and (ii) the development of complex object manipulation models, wherein the mechanical features of a real object are obtained and these features are then reproduced for training by means of virtual object manipulation. PMID:22247677

A theoretical and experimental study on the pulsed laser dressing of bronze-bonded diamond grinding wheels

NASA Astrophysics Data System (ADS)

Deng, H.; Chen, G. Y.; Zhou, C.; Zhou, X. C.; He, J.; Zhang, Y.

2014-09-01

A series of theoretical analyses and experimental investigations were performed to examine a pulsed fiber-laser tangential profiling and radial sharpening technique for bronze-bonded diamond grinding wheels. The mechanisms for the pulsed laser tangential profiling and radial sharpening of grinding wheels were theoretically analyzed, and the four key processing parameters that determine the quality, accuracy, and efficiency of pulsed laser dressing, namely, the laser power density, laser spot overlap ratio, laser scanning track line overlap ratio, and number of laser scanning cycles, were proposed. Further, by utilizing cylindrical bronze wheels (without diamond grains) and bronze-bonded diamond grinding wheels as the experimental subjects, the effects of these four processing parameters on the removal efficiency and the surface smoothness of the bond material after pulsed laser ablation, as well as the effects on the contour accuracy of the grinding wheels, the protrusion height of the diamond grains, the sharpness of the grain cutting edges, and the graphitization degree of the diamond grains after pulsed laser dressing, were explored. The optimal values of the four key processing parameters were identified.

Dynamics of Liquid-Filled Projectiles

DTIC Science & Technology

1976-04-01

1 Estimate of Shape of the Free Surface of the Liquid in a Liquid-Pilled Projectile During Acceleration 6 CHAPTER II. ANGULAR ACCELERATION OF THE...LIQUID IN A LIQUID-FILLED PROJECTILE DURING FLIGHT 13 Liquid "Spinup" in Configuration A 13 Angular Acceleration of the Liquid in Con... Angular Acceleration. 13 2.2 Tangential Velocity of Liquid Versus Radial Position at Several Values of Time (Liquid Configuration A) 21 2.3 Tangential