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Sample records for plunging liquid jet

  1. Distinguishing features of shallow angle plunging jets

    NASA Astrophysics Data System (ADS)

    Deshpande, Suraj S.; Trujillo, Mario F.

    2013-08-01

    Numerical simulations employing an algebraic volume-of-fluid methodology are used to study the air entrainment characteristics of a water jet plunging into a quiescent water pool at angles ranging from θ = 10° to θ = 90° measured from the horizontal. Our previous study of shallow angled jets [S. S. Deshpande, M. F. Trujillo, X. Wu, and G. L. Chahine, "Computational and experimental characterization of a liquid jet plunging into a quiescent pool at shallow inclination," Int. J. Heat Fluid Flow 34, 1-14 (2012)], 10.1016/j.ijheatfluidflow.2012.01.011 revealed the existence of a clearly discernible frequency of ingestion of large air cavities. This is in contrast with chaotic entrainment of small air pockets reported in the literature in case of steeper or vertically plunging jets. In the present work, the differences are addressed by first quantifying the cavity size and entrained air volumes for different impingement angles. The results support the expected trend - reduction in cavity size (D43) as θ is increased. Time histories of cavity volumes in the vicinity of the impingement region confirm the visual observations pertaining to a near-periodic ingestion of large air volumes for shallow jets (10°, 12°), and also show that such cavities are not formed for steep or vertical jets. Each large cavity (defined as Dc/Dj ≳ 3) exists in close association with a stagnation point flow. A local mass and momentum balance shows that the high stagnation pressure causes a radial redirection of the jet, resulting in a flow that resembles the initial impact of a jet on the pool. In fact, for these large cavities, their speed matches closely Uimpact/2, which coincides with initial cavity propagation for sufficiently high Froude numbers. Furthermore, it is shown that the approximate periodicity of air entrainment scales linearly with Froude number. This finding is confirmed by a number of simulations at θ = 12°. Qualitatively, for steeper jets, such large stagnation

  2. Laminar Plunging Jets - Interfacial Rupture and Inception of Entrainment

    NASA Astrophysics Data System (ADS)

    Kishore, Aravind

    Interfacial rupture and entrainment are commonly observed, e.g., air bubbles within a container being filled with water from a faucet. The example involves a liquid jet (density, rho, and viscosity, η) plunging into a receiving pool of liquid. Below a critical liquid-jet velocity, the interface develops a cusp-like shape within the receiving pool. The cusp becomes sharper with increasing liquid-jet velocity, and at a critical velocity ( Vc), the interface between the liquid and the surrounding fluid (density, rho0, and viscosity, η0) ruptures. Interfacial tension (sigma) can no longer preserve the integrity of the interface between the two immiscible fluids, and the plunging jet drags/entrains surrounding fluid into the receiving pool. Subsequently, the entrained fluid breaks up into bubbles within the receiving pool. The focus of this dissertation is the numerical prediction of the critical entrainment inception velocities for laminar plunging jets using the Volume-Of-Fluid (VOF) method, a Computational Fluid Dynamics (CFD) method to simulate multi-fluid flows. Canonical to bottle-filling operations in the industry is the plunging-jet configuration -- the liquid jet issues from a nozzle and plunges into a container filled with liquid. Simulations of this configuration require capturing flow phenomena over a large range of length scales (4 orders of magnitude). Results show severe under-prediction of critical entrainment velocities when the maximum resolution is insufficient to capture the sharpening, and eventual rupture, of the interfacial cusp. Higher resolutions resulted in computational meshes with prohibitively large number of cells, and a drastic reduction in time-step values. Experimental results in the literature suggest at least a 100-fold increase in the smallest length scale when the entrained fluid is a liquid instead of air. This narrows the range of length scales in the problem. We exploit the experimental correlation between critical capillary

  3. Numerical Investigation of Vertical Plunging Jet Using a Hybrid Multifluid–VOF Multiphase CFD Solver

    DOE PAGESBeta

    Shonibare, Olabanji Y.; Wardle, Kent E.

    2015-01-01

    A novel hybrid multiphase flow solver has been used to conduct simulations of a vertical plunging liquid jet. This solver combines a multifluid methodology with selective interface sharpening to enable simulation of both the initial jet impingement and the long-time entrained bubble plume phenomena. Models are implemented for variable bubble size capturing and dynamic switching of interface sharpened regions to capture transitions between the initially fully segregated flow types into the dispersed bubbly flow regime. It was found that the solver was able to capture the salient features of the flow phenomena under study and areas for quantitative improvement havemore » been explored and identified. In particular, a population balance approach is employed and detailed calibration of the underlying models with experimental data is required to enable quantitative prediction of bubble size and distribution to capture the transition between segregated and dispersed flow types with greater fidelity.« less

  4. Impact pressures of turbulent high-velocity jets plunging in pools with flat bottom

    NASA Astrophysics Data System (ADS)

    Manso, P. A.; Bollaert, E. F. R.; Schleiss, A. J.

    2007-01-01

    Dynamic pressures created by the impact of high-velocity turbulent jets plunging in a water pool with flat bottom were investigated. Pressure fluctuations were sampled at 1 kHz at the jet outlet and at the pool bottom using piezo-resistive pressure transducers, jet velocities of up to 30 m/s and pool depth to jet diameter ratios from 2.8 to 11.4. The high-velocity jets entrain air in the pool in conditions similar to prototype applications at water release structures of dams. The intermittent character of plunge pool flows was investigated for shallow and deep pools, based on high order moments and time correlations. Maximum intermittency was observed for pool depths at 5.6 jet diameters, which approximate the core development length. Wall pressure skewness was shown to allow identifying the zone of influence of downward and upward moving currents.

  5. FIELD MANUAL FOR PLUNGING WATER JET USE IN OIL SPILL CLEANUP

    EPA Science Inventory

    The use of plunging water jets can often make possible the control (and, as a consequence, the cleanup) of spilled oil and other floating pollutants in currents too swift for conventional equipment. This short, illustrated manual provides practical information for field and plann...

  6. Jets of incipient liquids

    NASA Astrophysics Data System (ADS)

    Reshetnikov, A. V.; Mazheiko, N. A.; Skripov, V. P.

    2000-05-01

    Jets of incipient water escaping into the atmosphere through a short channel are photographed. In some experiments. complete disintegration of the jet is observed. The relationship of this phenomenon with intense volume incipience is considered. The role of the Coanda effect upon complete opening of the jet is revealed. Measurement results of the recoil force R of the jets of incipient liquids are presented. Cases of negative thrust caused by the Coanda effect are noted. Generalization of experimental data is proposed.

  7. Dynamics of a cylinder plunging into liquid: a numerical study

    NASA Astrophysics Data System (ADS)

    Ding, Hang

    2012-11-01

    The impact of a cylinder on a liquid surface and subsequent events are investigated numerically. The flows are resolved by solving the Navier-Stokes equations and the Cahn-Hilliard equation. Moving contact lines are modeled by a diffuse interface model (Seppecher 1996; Jaqcmin 2000), and contact-angle hysteresis is included (Ding&Spelt 2008). The method is validated by comparison to the experiments by Aristoff and Bush (2009). Our studies focus on the dynamics of the waves induced by the impact and the cavity collapse behind the cylinder. A variety of parameters affect the flow behaviors such as wettability, impact speed, viscosity etc. Their effects on the transition of the flow phenomena are investigated through parametric simulations over relevant ranges of Weber and Reynolds numbers and contact angles. This work is supposed by the 100 Talents Program of the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 11172294).

  8. Whipping of electrified liquid jets.

    PubMed

    Guerrero, Josefa; Rivero, Javier; Gundabala, Venkata R; Perez-Saborid, Miguel; Fernandez-Nieves, Alberto

    2014-09-23

    We apply an electric field to a moderately conducting liquid surrounded by another coflowing liquid, all inside a glass-based microfluidic device, to study nonaxisymmetric instabilities. We find that the bending of the electrified jet results in a steady-state, helicoidal structure with a constant opening angle. Remarkably, the characteristic phase speed of the helicoidal wave only depends on the charge carried by the jet in the helicoidal region and its stability critically depends on the properties of the coflowing liquid. In fact, the steady-state helical structure becomes chaotic when the longest characteristic time is that of the inner liquid rather than that of the outer coflowing liquid. We also perform a numerical analysis to show that the natural preference of the jet is to adopt the conical helix structure observed experimentally. PMID:25201984

  9. Whipping of electrified liquid jets

    PubMed Central

    Guerrero, Josefa; Rivero, Javier; Gundabala, Venkata R.; Perez-Saborid, Miguel; Fernandez-Nieves, Alberto

    2014-01-01

    We apply an electric field to a moderately conducting liquid surrounded by another coflowing liquid, all inside a glass-based microfluidic device, to study nonaxisymmetric instabilities. We find that the bending of the electrified jet results in a steady-state, helicoidal structure with a constant opening angle. Remarkably, the characteristic phase speed of the helicoidal wave only depends on the charge carried by the jet in the helicoidal region and its stability critically depends on the properties of the coflowing liquid. In fact, the steady-state helical structure becomes chaotic when the longest characteristic time is that of the inner liquid rather than that of the outer coflowing liquid. We also perform a numerical analysis to show that the natural preference of the jet is to adopt the conical helix structure observed experimentally. PMID:25201984

  10. Transient gas jets into liquids

    NASA Astrophysics Data System (ADS)

    Lin, Jane Ming-Chin

    An experimental investigation of the development of high velocity, impulsively initiated gas jets into liquid was conducted in an effort to understand some of the physical processes that occur for a jet of very light fluid into a dense ambient atmosphere. Four gases, refrigerants 12 and 22, nitrogen, and helium were injected into water at nozzle exit Mach numbers from 1.0 to 2.2.The study showed that a gas jet into water develops in at least three stages: startup, transition, and global steady state. The startup is characterized by bubble growth; the growth rate is well predicted by classical bubble-growth theory. Jet transition is marked by axially directed flow, which penetrates through the startup bubble and which forms a cylindrical protrusion along the axis of symmetry. A combination of strong recirculating flow and liquid entrainment causes the startup bubble to deflate and to lift off and move downstream. In the steady state, instantaneous photographs show small-scale fluctuations of the jet boundary, but time-averaged photographs show the expected conical spreading of the steady jet; the measured spreading angles range from 18-25 degrees.However, the most significant finding of this study is that under some conditions, the gas jet into liquid never reaches the global steady state. Instead, the jet boundary exhibits chugging: large nonlinear oscillations which lead to irregular collapses of the gas column followed by explosive outward bursts of gas. The unsteadiness observed is much more violent than the familiar fluctuations typical of constant-density jets. The length scale of the motion is generally on the order of several jet diameters; the time scale is on the order of the period for bubble collapse.It was found that the amplitude and frequency of chugging are strongly dependent on the ratio of the liquid density to the gas density, the jet Mach number, and the operating pressure ratio. The conditions under which unsteadiness occurs were determined

  11. Disintegration of a Liquid Jet

    NASA Technical Reports Server (NTRS)

    Haenlein, A

    1932-01-01

    This report presents an experimental determination of the process of disintegration and atomization in its simplest form, and the influence of the physical properties of the liquid to be atomized on the disintegration of the jet. Particular attention was paid to the investigation of the process of atomization.

  12. Dynamics of liquid films and thin jets

    NASA Technical Reports Server (NTRS)

    Zak, M.

    1979-01-01

    The theory of liquid films and thin jets as one- and two-dimensional continuums is examined. The equations of motion have led to solutions for the characteristic speeds of wave propagation for the parameters characterizing the shape. The formal analogy with a compressible fluid indicates the possibility of shock wave generation in films and jets and the formal analogy to the theory of threads and membranes leads to the discovery of some new dynamic effects. The theory is illustrated by examples.

  13. Droplet formation for liquid monopropellant jets

    NASA Astrophysics Data System (ADS)

    Macken, Nelson A.

    1987-02-01

    The hydrodynamic development of droplets for conditions approximating those in the combustion chamber of regenerative liquid propellant guns has been investigated. The report contains a literature survey and discussion of various breakup mechanisms. Aerodynamic interaction is analyzed using classical stability theory and a formulation applied to anticipated working conditions. The model predicts mass removed and droplet size as a function of time. Results indicate that the jet does break up with almost all liquid atomized. Comparison to a simple burning rate model verifies that the hydrodynamic model is primarily responsible for liquid removal from the intact core. Results conflict with recent inverse gun code predictions which suggest significant liquid accumulation is occurring; i.e., the jet does not fully atomize and subsequently burn. A discussion of possible reasons for this discrepancy is included.

  14. Bouncing and Merging of Liquid Jets

    NASA Astrophysics Data System (ADS)

    Saha, Abhishek; Li, Minglei; Law, Chung K.

    2014-11-01

    Collision of two fluid jets is a technique that is utilized in many industrial applications, such as in rocket engines, to achieve controlled mixing, atomization and sometimes liquid phase reactions. Thus, the dynamics of colliding jets have direct impact on the performance, efficiency and reliability of such applications. In analogy with the dynamics of droplet-droplet collision, in this work we have experimentally demonstrated, for n-alkane hydrocarbons as well as water, that with increasing impact inertia obliquely colliding jets also exhibit the same nonmonotonic responses of merging, bouncing, merging again, and merging followed by disintegration; and that the continuous entrainment of the boundary layer air over the jet surface into the colliding interfacial region leads to two distinguishing features of jet collision, namely: there exists a maximum impact angle beyond which merging is always possible, and that merging is inhibited and then promoted with increasing pressure. These distinct response regimes were mapped and explained on the bases of impact inertia, deformation of the jet surface, viscous loss within the jet interior, and the thickness and pressure build-up within the interfacial region in order to activate the attractive surface van der Waals force to effect merging.

  15. Velocity-modulation atomization of liquid jets

    NASA Technical Reports Server (NTRS)

    Dressler, John L.

    1994-01-01

    A novel atomizer based on high-amplitude velocity atomization has been developed. Presently, the most common methods of atomization can use only the Rayleigh instability of a liquid cylinder and the Kelvin-Helmholtz instability of a liquid sheet. Our atomizer is capable of atomizing liquid jets by the excitation and destabilization of many other higher-order modes of surface deformation. The potential benefits of this sprayer are more uniform fuel air mixtures, faster fuel-air mixing, extended flow ranges for commercial nozzles, and the reduction of nozzle plugging by producing small drops from large nozzles.

  16. Breakup of Liquid Sheets and Jets

    NASA Astrophysics Data System (ADS)

    Lin, S. P.

    2003-09-01

    This book is an exposition of what we know about the physics underlying the onset of instability in liquid sheets and jets. Wave motion and breakup phenomena subsequent to the onset of instability are also carefully explained. Physical concepts are established through mathematics, accurate numerical analysis and comparison of theory with experiments. Exercises are provided for students new to the subject. Researchers interested in topics ranging from transition to turbulence, hydrodynamic stability or combustion will find this book a useful resource, whether their background lies in engineering, physics, chemistry, biology, medicine or applied mathematics.

  17. Liquid jet pumps for two-phase flows

    SciTech Connect

    Cunningham, R.G.

    1995-06-01

    Isothermal compression of a bubbly secondary fluid in a mixing-throat and diffuser is described by a one-dimensional flow model of a liquid-jet pump. Friction-loss coefficients used in the four equations may be determined experimentally, or taken from the literature. The model reduces to the liquid-jet gas compressor case if the secondary liquid is zero. Conversely, a zero secondary-gas flow reduces the liquid-jet gas and liquid (LJGL) model to that of the familiar liquid-jet liquid pump. A ``jet loss`` occurs in liquid-jet pumps if the nozzle tip is withdrawn from the entrance plane of the throat, and jet loss is included in the efficiency equations. Comparisons are made with published test data for liquid-jet liquid pumps and for liquid-jet gas compressors. The LJGL model is used to explore jet pump responses to two-phase secondary flows, nozzle-to-throat area ratio, and primary-jet velocity. The results are shown in terms of performance curves versus flow ratios. Predicted peak efficiencies are approximately 50 percent. Under sever operating conditions, LJGL pump performance curves exhibit maximum-flow ratios or cut-offs. Cut-offs occurs when two-phase secondary-flow steams attain sonic values at the entry of the mixing throat. A dimensionless number correlates flow-ratio cut-offs with pump geometry and operating conditions. Throat-entry choking of the secondary flow can be predicted, hence avoided, in designing jet pumps to hand two-phase fluids.

  18. Analysis of interaction phenomena between liquid jets and materials [preprint

    SciTech Connect

    Kang, S-W.; Reitter, T.; Carlson, G.

    1995-04-01

    The interaction phenomena of high-velocity liquid jets impinging on a material surface have been investigated theoretically and experimentally to understand the physics of material removal by jet-machining processes. Experiments were performed to delineate conditions under which liquid jet impacts will cause mass removal and to determine optimum jet-cutting conditions. Theoretical analyses have also been carried out to study the effects of multiple jet-droplet impacts on a target surface as a material deformation mechanism. The calculated target response and spallation behavior following droplet impacts and their physical implications are also discussed.

  19. Bouncing jet: a Newtonian liquid rebounding off a free surface.

    PubMed

    Thrasher, Matthew; Jung, Sunghwan; Pang, Yee Kwong; Chuu, Chih-Piao; Swinney, Harry L

    2007-11-01

    We find that a liquid jet can bounce off a bath of the same liquid if the bath is moving horizontally with respect to the jet. Previous observations of jets rebounding off a bath (e.g., the Kaye effect) have been reported only for non-Newtonian fluids, while we observe bouncing jets in a variety of Newtonian fluids, including mineral oil poured by hand. A thin layer of air separates the bouncing jet from the bath, and the relative motion replenishes the film of air. Jets with one or two bounces are stable for a range of viscosity, jet flow rate and velocity, and bath velocity. The bouncing phenomenon exhibits hysteresis and multiple steady states. PMID:18233768

  20. Bouncing jet: A Newtonian liquid rebounding off a free surface

    NASA Astrophysics Data System (ADS)

    Thrasher, Matthew; Jung, Sunghwan; Pang, Yee Kwong; Chuu, Chih-Piao; Swinney, Harry L.

    2007-11-01

    We find that a liquid jet can bounce off a bath of the same liquid if the bath is moving horizontally with respect to the jet. Previous observations of jets rebounding off a bath (e.g., the Kaye effect) have been reported only for non-Newtonian fluids, while we observe bouncing jets in a variety of Newtonian fluids, including mineral oil poured by hand. A thin layer of air separates the bouncing jet from the bath, and the relative motion replenishes the film of air. Jets with one or two bounces are stable for a range of viscosity, jet flow rate and velocity, and bath velocity. The bouncing phenomenon exhibits hysteresis and multiple steady states.

  1. Multiphase flow of miscible liquids: jets and drops

    NASA Astrophysics Data System (ADS)

    Walker, Travis W.; Logia, Alison N.; Fuller, Gerald G.

    2015-05-01

    Drops and jets of liquids that are miscible with the surrounding bulk liquid are present in many processes from cleaning surfaces with the aid of liquid soaps to the creation of biocompatible implants for drug delivery. Although the interactions of immiscible drops and jets show similarities to miscible systems, the small, transient interfacial tension associated with miscible systems create distinct outcomes such as intricate droplet shapes and breakup resistant jets. Experiments have been conducted to understand several basic multiphase flow problems involving miscible liquids. Using high-speed imaging of the morphological evolution of the flows, we have been able to show that these processes are controlled by interfacial tensions. Further multiphase flows include investigating miscible jets, which allow the creation of fibers from inelastic materials that are otherwise difficult to process due to capillary breakup. This work shows that stabilization from the diminishing interfacial tensions of the miscible jets allows various elongated morphologies to be formed.

  2. Analysis of interaction phenomena between liquid jets and materials

    SciTech Connect

    Kang, Sang-Wook; Reitter, T.; Carlson, G.

    1995-02-01

    The interaction phenomena of high-velocity liquid jets impinging on a material surface have been investigated theoretically and experimentally to gain an understanding of the physical mechanisms involved in material removal by fluidjet machining processes. Experiments were performed to determine conditions under which the liquid jet impacting a solid material will cause material removal and also to delineate possible physical mechanisms of mass removal at optimum jet-cutting conditions. We have also carried out numerical simulations of jet-induced surface pressure rises and of the material deformation and spallation behavior due to multiple droplet impacts. Results obtained from the experiments and theoretical calculations and their physical implications are also discussed.

  3. Liquid gallium jet-plasma interaction studies in ISTTOK tokamak

    NASA Astrophysics Data System (ADS)

    Gomes, R. B.; Fernandes, H.; Silva, C.; Sarakovskis, A.; Pereira, T.; Figueiredo, J.; Carvalho, B.; Soares, A.; Duarte, P.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Tale, I.; Alekseyv, A.

    2009-06-01

    Liquid metals have been pointed out as a suitable solution to solve problems related to the use of solid walls submitted to high power loads allowing, simultaneously, an efficient heat exhaustion process from fusion devices. The most promising candidate materials are lithium and gallium. However, lithium has a short liquid state temperature range when compared with gallium. To explore further this property, ISTTOK tokamak is being used to test the interaction of a free flying liquid gallium jet with the plasma. ISTTOK has been successfully operated with this jet without noticeable discharge degradation and no severe effect on the main plasma parameters or a significant plasma contamination by liquid metal. Additionally the response of an infrared sensor, intended to measure the jet surface temperature increase during its interaction with the plasma, has been studied. The jet power extraction capability is extrapolated from the heat flux profiles measured in ISTTOK plasmas.

  4. Atmospheric pressure plasma jet for liquid spray treatment

    NASA Astrophysics Data System (ADS)

    Mitić, S.; Philipps, J.; Hofmann, D.

    2016-05-01

    Atmospheric pressure plasma jets have been intensively studied in recent years due to growing interest in their use for biomedical applications and surface treatments. Either surfaces can be treated by a plasma jet afterglow for cleaning or activation or a material can be deposited by a reactive gas component activated by plasma. Effects of plasma on liquid have been reported several times where the electron spin trapping method was used for radical detection. Here we propose another method of liquid treatment using the atmospheric pressure plasma jet. In the device presented here, liquid was sprayed in droplets from an inner electrode directly into a plasma jet where it was treated and sprayed out by gas flow. Optical end electrical measurements were done for diagnostics of the plasma while electron paramagnetic resonance measurements were used for detection of radicals (\\text{OH},\\text{OOH},\\text{CH} ) produced by plasma treatment of liquids.

  5. Stability of liquid-nitrogen-jet laser-plasma targets

    SciTech Connect

    Fogelqvist, E. Kördel, M.; Selin, M.; Hertz, H. M.

    2015-11-07

    Microscopic jets of cryogenic substances such as liquid nitrogen are important regenerative high-density targets for high-repetition rate, high-brightness laser-plasma soft x-ray sources. When operated in vacuum such liquid jets exhibit several non-classical instabilities that negatively influence the x-ray source's spatial and temporal stability, yield, and brightness, parameters that all are important for applications such as water-window microscopy. In the present paper, we investigate liquid-nitrogen jets with a flash-illumination imaging system that allows for a quantitative stability analysis with high spatial and temporal resolution. Direct and indirect consequences of evaporation are identified as the key reasons for the observed instabilities. Operating the jets in an approximately 100 mbar ambient atmosphere counteracts the effects of evaporation and produces highly stable liquid nitrogen jets. For operation in vacuum, which is necessary for the laser plasmas, we improve the stability by introducing an external radiative heating element. The method significantly extends the distance from the nozzle that can be used for liquid-jet laser plasmas, which is of importance for high-average-power applications. Finally, we show that laser-plasma operation with the heating-element-stabilized jet shows improved short-term and long-term temporal stability in its water-window x-ray emission.

  6. Stability of liquid-nitrogen-jet laser-plasma targets

    NASA Astrophysics Data System (ADS)

    Fogelqvist, E.; Kördel, M.; Selin, M.; Hertz, H. M.

    2015-11-01

    Microscopic jets of cryogenic substances such as liquid nitrogen are important regenerative high-density targets for high-repetition rate, high-brightness laser-plasma soft x-ray sources. When operated in vacuum such liquid jets exhibit several non-classical instabilities that negatively influence the x-ray source's spatial and temporal stability, yield, and brightness, parameters that all are important for applications such as water-window microscopy. In the present paper, we investigate liquid-nitrogen jets with a flash-illumination imaging system that allows for a quantitative stability analysis with high spatial and temporal resolution. Direct and indirect consequences of evaporation are identified as the key reasons for the observed instabilities. Operating the jets in an approximately 100 mbar ambient atmosphere counteracts the effects of evaporation and produces highly stable liquid nitrogen jets. For operation in vacuum, which is necessary for the laser plasmas, we improve the stability by introducing an external radiative heating element. The method significantly extends the distance from the nozzle that can be used for liquid-jet laser plasmas, which is of importance for high-average-power applications. Finally, we show that laser-plasma operation with the heating-element-stabilized jet shows improved short-term and long-term temporal stability in its water-window x-ray emission.

  7. Splattering during turbulent liquid jet impingement on solid targets

    SciTech Connect

    Bhunia, S.K.; Lienhard, J.H. V . Dept. of Mechanical Engineering)

    1994-06-01

    In turbulent liquid jet impingement, a spray of droplets often breaks off of the liquid layer formed on the target. This splattering of liquid alters the efficiencies of jet impingement heat transfer processes and chemical containment safety devices, and leads to problems of aerosol formation in jet impingement cleaning processes. In this paper, the authors present a more complete study of splattering and improved correlations that extend and supersede the previous reports on this topic. The authors report experimental results on the amount of splattering for jets of water, isopropanol-water solutions, and soap-water mixtures. Jets were produced by straight tube nozzles of diameter 0.8--5.8 mm, with fully developed turbulent pipe-flow upstream of the nozzle exist. These experiments cover Weber numbers between 130--31,000, Reynolds numbers between 2,700--98,000, and nozzle-to-target separations of 0.2 [<=]l/d[<=]125. Splattering of up to 75 percent of the incoming jet liquid is observed. The results show that only the Weber number and l/d affect the fraction of jet liquid splattered. The presence of surfactants does not alter the splattering. A new correlation for the onset condition for splattering is given. In addition, the authors establish the range of applicability of the model of Lienhard et al. and the authors provide a more accurate set of coefficients for their correlation.

  8. Interaction of a Liquid Gallium Jet with ISTTOK Edge Plasmas

    NASA Astrophysics Data System (ADS)

    Gomes, R. B.; Fernandes, H.; Silva, C.; Sarakovskis, A.; Pereira, T.; Figueiredo, J.; Carvalho, B.; Soares, A.; Duarte, P.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Tale, I.

    2008-04-01

    The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages in the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaust from fusion devices. Presently the most promising candidate materials are lithium and gallium. However, lithium has a short liquid state range when compared, for example, with gallium that has essentially better thermal properties and lower vapor pressure. To explore further these properties, ISTTOK tokamak is being used to test the interaction of a free flying, fully formed liquid gallium jet with the plasma. The interacting, 2.3 mm diameter, jet is generated by hydrostatic pressure and has a 2.5 m/s flow velocity. The liquid metal injector has been build to allow the positioning of the jet inside the tokamak chamber, within a 13 mm range. This paper presents the first obtained experimental results concerning the liquid gallium jet-plasma interaction. A stable jet has been obtained, which was not noticeably affected by the magnetic field transients. ISTTOK has been successfully operated with the gallium jet without degradation of the discharge or a significant plasma contamination by liquid metal. This observation is supported by spectroscopic measurements showing that gallium radiation is limited to the region around the jet. Furthermore, the power deposited on the jet has been evaluated at different radial locations and the surface temperature increase estimated.

  9. Cavitating Jet Method and System for Oxygenation of Liquids

    NASA Technical Reports Server (NTRS)

    Chahine, Georges L.

    2012-01-01

    Reclamation and re-use of water is critical for space-based life support systems. A number of functions must be performed by any such system including removal of various contaminants and oxygenation. For long-duration space missions, this must be done with a compact, reliable system that requires little or no use of expendables and minimal power. DynaJets cavitating jets can oxidize selected organic compounds with much greater energy efficiency than ultrasonic devices typically used in sonochemistry. The focus of this work was to develop cavitating jets to simultaneously accomplish the functions of oxygenation and removal of contaminants of importance to space-structured water reclamation systems. The innovation is a method to increase the concentration of dissolved oxygen or other gasses in a liquid. It utilizes a particular form of novel cavitating jet operating at low to moderate pressures to achieve a high-efficiency means of transporting and mixing the gas into the liquid. When such a jet is utilized to simultaneously oxygenate the liquid and to oxidize organic compounds within the liquid, such as those in waste water, the rates of contaminant removal are increased. The invention is directed toward an increase in the dissolved gas content of a liquid, in general, and the dissolved oxygen content of a liquid in particular.

  10. Controls on Filling and Evacuation of Sediment in Waterfall Plunge Pools

    NASA Astrophysics Data System (ADS)

    Scheingross, J. S.; Lamb, M. P.

    2014-12-01

    Many waterfalls are characterized by the presence of deep plunge pools that experience periods of sediment fill and evacuation. These cycles of sediment fill are a first order control on the relative magnitude of lateral versus vertical erosion at the base of waterfalls, as vertical incision requires cover-free plunge pools to expose the bedrock floor, while lateral erosion can occur when pools are partially filled and plunge-pool walls are exposed. Currently, there exists no mechanistic model describing sediment transport through waterfall plunge pools, limiting our ability to predict waterfall retreat. To address this knowledge gap, we performed detailed laboratory experiments measuring plunge-pool sediment transport capacity (Qsc_pool) under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. Our experimental plunge-pool sediment transport capacity measurements match well with a mechanistic model we developed which combines existing waterfall jet theory with a modified Rouse profile to predict sediment transport capacity as a function of water discharge and suspended sediment concentration at the plunge-pool lip. Comparing the transport capacity of plunge pools to lower gradient portions of rivers (Qsc_river) shows that, for transport limited conditions, plunge pools fill with sediment under modest water discharges when Qsc_river > Qsc_pool, and empty to bedrock under high discharges when Qsc_pool > Qsc_river. These results are consistent with field observations of sand-filled plunge pools with downstream boulder rims, implying filling and excavation of plunge pools over single-storm timescales. Thus, partial filling of waterfall plunge pools may provide a mechanism to promote lateral undercutting and retreat of waterfalls in homogeneous rock in which plunge-pool vertical incision occurs during brief large floods that expose bedrock, whereas lateral erosion may prevail during smaller events.

  11. Magnetohydrodynamic stability of a compound liquid jet

    NASA Astrophysics Data System (ADS)

    Radwan, Ahmed E.

    1989-10-01

    The magnetohydrodynamics (MHD) stability of a compound nonmiscible fluid jet is discussed. A general eigenvalue relation, for that model which involves the fluid inertia, capillarity and electromagnetic forces, is derived. The model is capillary unstable only for small axisymmetric disturbances and stable for the rest. The magnetic fields interior and exterior to the gas-mantle jet have always a stabilizing influence. The radii ratio of the concentric jets plays an important role in the (instability) stability states and are (decreasing) increasing with increasing magnetic field intensity as the exterior radius is much larger than the interior radius; under some restrictions of the radii ratio and above a certain value of the magnetic field the capillary instability is omitted and completely suppressed and then stability sets in. The latter result is verified analytically and confirmed numerically in the case in which the cylindrical surface of the outer jet is sited at infinity.

  12. Time-resolved proper orthogonal decomposition of liquid jet dynamics

    NASA Astrophysics Data System (ADS)

    Arienti, Marco; Soteriou, Marios C.

    2009-11-01

    New insight into the mechanism of liquid jet in crossflow atomization is provided by an analysis technique based on proper orthogonal decomposition and spectral analysis. Data are provided in the form of high-speed videos of the jet near field from experiments over a broad range of injection conditions. For each condition, proper orthogonal modes (POMs) are generated and ordered by intensity variation relative to the time average. The feasibility of jet dynamics reduction by truncation of the POM series to the first few modes is then examined as a function of crossflow velocity for laminar and turbulent liquid injection. At conditions where the jet breaks up into large chunks of liquid, the superposition of specific orthogonal modes is observed to track long waves traveling along the liquid column. The temporal coefficients of these modes can be described as a bandpass spectrum that shifts toward higher frequencies as the crossflow velocity is increased. The dynamic correlation of these modes is quantified by their cross-power spectrum density. Based on the frequency and wavelength extracted from the videos, the observed traveling waves are linked to the linearly fastest growing wave of Kelvin-Helmholtz instability. The gas boundary layer thickness at the gas-liquid shear layer emerges at the end of this study as the dominant length scale of jet dynamics at moderate Weber numbers.

  13. Contraction of an inviscid swirling liquid jet: Comparison with results for a rotating granular jet.

    NASA Astrophysics Data System (ADS)

    Weidman, P. D.; Kubitschek, J. P.

    2007-11-01

    In honor of the tercentenary of Leonhard Euler, we report a new solution of the Euler equations for the shape of an inviscid rotating liquid jet emanating from a tube of inner radius R0 aligned with gravity. Jet contraction is dependent on the exit swirl parameter χ0 = R0 φ0/U0 where φ0 and U0 are the uniform rotation rate and axial velocity of the liquid at the exit. The results reveal that rotation reduces the rate of jet contraction. In the limit χ0-> 0 one recovers the contraction profile for a non-rotating jet and the limit χ0->∞ gives a jet of constant radius. In contrast, experiments and a kinematic model for a rotating non-cohesive granular jet show that it expands rather than contracts when a certain small angular velocity is exceeded. The blossoming profiles are parabolic in nature. The model predicts a jet of uniform radius for χ0-> 0 and a jet with an initially horizontal trajectory in the limit χ0->∞.

  14. Impinging jet separators for liquid metal magnetohydrodynamic power cycles

    NASA Technical Reports Server (NTRS)

    Bogdanoff, D. W.

    1973-01-01

    In many liquid metal MHD power, cycles, it is necessary to separate the phases of a high-speed liquid-gas flow. The usual method is to impinge the jet at a glancing angle against a solid surface. These surface separators achieve good separation of the two phases at a cost of a large velocity loss due to friction at the separator surface. This report deals with attempts to greatly reduce the friction loss by impinging two jets against each other. In the crude impinging jet separators tested to date, friction losses were greatly reduced, but the separation of the two phases was found to be much poorer than that achievable with surface separators. Analyses are presented which show many lines of attack (mainly changes in separator geometry) which should yield much better separation for impinging jet separators).

  15. Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools

    NASA Astrophysics Data System (ADS)

    Scheingross, Joel S.; Lamb, Michael P.

    2016-05-01

    Many waterfalls have deep plunge pools that are often partially or fully filled with sediment. Sediment fill may control plunge-pool bedrock erosion rates, partially determine habitat availability for aquatic organisms, and affect sediment routing and debris flow initiation. Currently, there exists no mechanistic model to describe sediment transport through waterfall plunge pools. Here we develop an analytical model to predict steady-state plunge-pool depth and sediment-transport capacity by combining existing jet theory with sediment transport mechanics. Our model predicts plunge-pool sediment-transport capacity increases with increasing river discharge, flow velocity, and waterfall drop height and decreases with increasing plunge-pool depth, radius, and grain size. We tested the model using flume experiments under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. The model and experiments show that through morphodynamic feedbacks, plunge pools aggrade to reach shallower equilibrium pool depths in response to increases in imposed sediment supply. Our theory for steady-state pool depth matches the experiments with an R2 value of 0.8, with discrepancies likely due to model simplifications of the hydraulics and sediment transport. Analysis of 75 waterfalls suggests that the water depths in natural plunge pools are strongly influenced by upstream sediment supply, and our model provides a mass-conserving framework to predict sediment and water storage in waterfall plunge pools for sediment routing, habitat assessment, and bedrock erosion modeling.

  16. Experimental investigation of charged liquid jet efflux from a capillary

    NASA Astrophysics Data System (ADS)

    Zhakin, A. I.; Belov, P. A.; Kuz'ko, A. E.

    2013-03-01

    The shapes and electrical characteristics of charged liquid (water, ethanol, glycerol, castor oil) jets emitted from a metal capillary have been experimentally studied depending on the applied high voltage. A map of efflux regimes in the flow velocity-applied voltage coordinates is constructed for water. The effects of medium viscosity, surface tension, and charge relaxation time on the laws of jet efflux are analyzed.

  17. Some Numerical Research of Supersonic Gaseous Jet Injected Into Liquid

    NASA Astrophysics Data System (ADS)

    Sun, L. H.; Hu, J.; Yu, Y.

    2011-09-01

    The article kept the laval nozzle outer radium (D) and nozzle expansion ratio as a constant. Three different underwater gas jets multiphase unsteady flows were simulated using the volume of fluid (VOF) method. It adopted standard κ—ɛ turbulence mode and SIMPLE algorithm to solve the two-phase flow of supersonic gaseous jet injected into liquid. We got the flow structure and the main parameters of the flow field and compared and analyzed the key parameters of three different flow field.

  18. Transverse liquid fuel jet breakup, burning, and ignition

    SciTech Connect

    Li, H.

    1990-12-31

    An analytical/numerical study of the breakup, burning, and ignition of liquid fuels injected transversely into a hot air stream is conducted. The non-reacting liquid jet breakup location is determined by the local sonic point criterion first proposed by Schetz, et al. (1980). Two models, one employing analysis of an elliptical jet cross-section and the other employing a two-dimensional blunt body to represent the transverse jet, have been used for sonic point calculations. An auxiliary criterion based on surface tension stability is used as a separate means of determining the breakup location. For the reacting liquid jet problem, a diffusion flame supported by a one-step chemical reaction within the gaseous boundary layer is solved along the ellipse surface in subsonic crossflow. Typical flame structures and concentration profiles have been calculated for various locations along the jet cross-section as a function of upstream Mach numbers. The integrated reaction rate along the jet cross-section is used to predict ignition position, which is found to be situated near the stagnation point. While a multi-step reaction is needed to represent the ignition process more accurately, the present calculation does yield reasonable predictions concerning ignition along a curved surface.

  19. Transverse liquid fuel jet breakup, burning, and ignition

    SciTech Connect

    Li, H.

    1990-01-01

    An analytical/numerical study of the breakup, burning, and ignition of liquid fuels injected transversely into a hot air stream is conducted. The non-reacting liquid jet breakup location is determined by the local sonic point criterion first proposed by Schetz, et al. (1980). Two models, one employing analysis of an elliptical jet cross-section and the other employing a two-dimensional blunt body to represent the transverse jet, have been used for sonic point calculations. An auxiliary criterion based on surface tension stability is used as a separate means of determining the breakup location. For the reacting liquid jet problem, a diffusion flame supported by a one-step chemical reaction within the gaseous boundary layer is solved along the ellipse surface in subsonic crossflow. Typical flame structures and concentration profiles have been calculated for various locations along the jet cross-section as a function of upstream Mach numbers. The integrated reaction rate along the jet cross-section is used to predict ignition position, which is found to be situated near the stagnation point. While a multi-step reaction is needed to represent the ignition process more accurately, the present calculation does yield reasonable predictions concerning ignition along a curved surface.

  20. Modeling of Turbulence Effect on Liquid Jet Atomization

    NASA Technical Reports Server (NTRS)

    Trinh, H. P.

    2007-01-01

    Recent studies indicate that turbulence behaviors within a liquid jet have considerable effect on the atomization process. Such turbulent flow phenomena are encountered in most practical applications of common liquid spray devices. This research aims to model the effects of turbulence occurring inside a cylindrical liquid jet to its atomization process. The two widely used atomization models Kelvin-Helmholtz (KH) instability of Reitz and the Taylor analogy breakup (TAB) of O'Rourke and Amsden portraying primary liquid jet disintegration and secondary droplet breakup, respectively, are examined. Additional terms are formulated and appropriately implemented into these two models to account for the turbulence effect. Results for the flow conditions examined in this study indicate that the turbulence terms are significant in comparison with other terms in the models. In the primary breakup regime, the turbulent liquid jet tends to break up into large drops while its intact core is slightly shorter than those without turbulence. In contrast, the secondary droplet breakup with the inside liquid turbulence consideration produces smaller drops. Computational results indicate that the proposed models provide predictions that agree reasonably well with available measured data.

  1. Numerical modeling for primary atomization of liquid jets

    NASA Technical Reports Server (NTRS)

    Przekwas, A. J.; Chuech, S. G.; Singhal, A. K.

    1989-01-01

    In the proposed numerical model for primary atomization, surface-wave dispersion equations are solved in conjunction with the jet-embedding technique of solving mean flow equations of a liquid jet. Linear and approximate nonlinear models have been considered. In each case, the dispersion equation is solved over the whole wavelength spectrum to predict drop sizes, frequency, and liquid-mass breakup rates without using any empirical constants. The present model has been applied to several low-speed and high-speed jets. For the high-speed case (the LOX/H2 coaxial injector of the Space Shuttle Main Engine Preburner), predicted drop sizes and liquid breakup rates are in good agreement with the results of the CICM code, which have been calibrated against measured data.

  2. On the separation of droplets from a liquid jet

    NASA Astrophysics Data System (ADS)

    1996-02-01

    The droplet separation from a liquid jet was investigated experimentally. Details of the shape of the thin liquid neck joining the droplet to its parent body were studied in terms of the fluid viscosity and the jet diameter. As the viscosity increased, the neck rapidly elongated creating a long thread. Its final diameter before rupture was approximately one micrometer and seems to be constant within wide range of parameters varied. One or multiple breakups of the micro-thread were observed, which produced micro-satellites, i.e. droplets in a micrometer range. The experimental results only partly confirmed the predictions of Eggers' (Phys. Rev. Lett. 71 (1993) 3458) similarity solution. The predicted shape of the pinch-off region well overlaps the long thread observed for very viscous liquids. However, the final jet diameter, retraction velocity of the thread and presence of multiple breakups differentiate the experimental evidence from the model expectations.

  3. On transit time instability in liquid jets

    NASA Technical Reports Server (NTRS)

    Grabitz, G.; Meier, G.

    1982-01-01

    A basic transit time instability in flows with disturbances of speed is found. It was shown that the mass distribution is established by and large by the described transit time effects. These transit time effects may also be involved for gas jets.

  4. Helical instability of a rotating viscous liquid jet

    NASA Astrophysics Data System (ADS)

    Kubitschek, J. P.; Weidman, P. D.

    2007-11-01

    Experimental results are presented for a rotating viscous liquid jet showing a clear preference for helical instabilities that evolve from initially planar disturbances at large rotation rates. In the ideal case of a uniformly rotating viscous liquid column with stress-free boundaries in the absence of gravity, the preferred modes of linear temporal instability are theoretically known over the entire physical domain. The relevant physical parameters are L=γ/ρa^3φ^2 and Re = a^2φ/ν, where a is the column radius, φ the uniform angular velocity and ρ, ν, and γ are fluid density, kinematic viscosity and surface tension, respectively. The theoretical results suggest that instability in different regions of L-Re parameter space is dominated by three modes: the axisymmetric mode, n>= 2 planar modes, and the first n = 1 spiral mode. For the rotating viscous liquid jet, experiments reveal that planar disturbances of the same mode numbers (n>= 2) spontaneously arise in the same regions of parameter space predicted by uniformly rotating viscous liquid column theory. However, these planar disturbances do not persist, but instead rapidly evolve into helical instabilities. Although fundamental differences exist between the rotating liquid jet and the uniformly rotating liquid column, some remarkable similarities associated with initial growth rates, disturbances frequencies, and mode transitions between the two systems are found.

  5. Observations of breakup processes of liquid jets using real-time X-ray radiography

    NASA Technical Reports Server (NTRS)

    Char, J. M.; Kuo, K. K.; Hsieh, K. C.

    1988-01-01

    To unravel the liquid-jet breakup process in the nondilute region, a newly developed system of real-time X-ray radiography, an advanced digital image processor, and a high-speed video camera were used. Based upon recorded X-ray images, the inner structure of a liquid jet during breakup was observed. The jet divergence angle, jet breakup length, and fraction distributions along the axial and transverse directions of the liquid jets were determined in the near-injector region. Both wall- and free-jet tests were conducted to study the effect of wall friction on the jet breakup process.

  6. Two-phase liquid-liquid flows generated by impinging liquid jets

    NASA Astrophysics Data System (ADS)

    Tsaoulidis, Dimitrios; Li, Qi; Angeli, Panagiota

    2015-11-01

    Two-phase flows in intensified small-scale systems find increasing applications in (bio)chemical analysis and synthesis, fuel cells, polymerisation, and separation processes (solvent extraction). Current nuclear spent fuel reprocessing separation technologies have been developed many decades ago and have not taken account recent advances on process intensification which can drive down plant size and economics. In this work, intensified impinging jets will be developed to create dispersions by bringing the two liquid phases into contact through opposing small channels. A systematic set of experiments has been undertaken, to investigate the hydrodynamic characteristics, to develop predictive models, and enable comparisons with other contactors. Drop size distribution and mixing intensity will be investigated for liquid-liquid mixtures as a function of various parameters using high speed imaging and conductivity probes.

  7. Study of liquid jet instability by confocal microscopy.

    PubMed

    Yang, Lisong; Adamson, Leanne J; Bain, Colin D

    2012-07-01

    The instability of a liquid microjet was used to measure the dynamic surface tension of liquids at the surface ages of ≤1 ms using confocal microscopy. The reflected light from a laser beam at normal incidence to the jet surface is linear in the displacement of the surface near the confocal position, leading to a radial resolution of 4 nm and a dynamic range of 4 μm in the surface position, thus permitting the measurement of amplitude of oscillation at the very early stage of jet instability. For larger oscillations outside the linear region of the confocal response, the swell and neck position of the jet can be located separately and the amplitude of oscillation determined with an accuracy of 0.2 μm. The growth rate of periodically perturbed water and ethanol∕water mixture jets with a 100-μm diameter nozzle and mean velocity of 5.7 m s(-1) has been measured. The dynamic surface tension was determined from the growth rate of the instability with a linear, axisymmetric, constant property model. Synchronisation of the confocal imaging system with the perturbation applied to the jet permitted a detailed study of the temporal evolution of the neck into a ligament and eventually into a satellite drop. PMID:22852668

  8. Study of liquid jet instability by confocal microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Lisong; Adamson, Leanne J.; Bain, Colin D.

    2012-07-01

    The instability of a liquid microjet was used to measure the dynamic surface tension of liquids at the surface ages of ≤1 ms using confocal microscopy. The reflected light from a laser beam at normal incidence to the jet surface is linear in the displacement of the surface near the confocal position, leading to a radial resolution of 4 nm and a dynamic range of 4 μm in the surface position, thus permitting the measurement of amplitude of oscillation at the very early stage of jet instability. For larger oscillations outside the linear region of the confocal response, the swell and neck position of the jet can be located separately and the amplitude of oscillation determined with an accuracy of 0.2 μm. The growth rate of periodically perturbed water and ethanol/water mixture jets with a 100-μm diameter nozzle and mean velocity of 5.7 m s-1 has been measured. The dynamic surface tension was determined from the growth rate of the instability with a linear, axisymmetric, constant property model. Synchronisation of the confocal imaging system with the perturbation applied to the jet permitted a detailed study of the temporal evolution of the neck into a ligament and eventually into a satellite drop.

  9. Liquid Jet Formation in Laser-Induced Forward Transfer

    NASA Astrophysics Data System (ADS)

    Brasz, C. Frederik

    Laser-induced forward transfer (LIFT) is a direct-write technique capable of printing precise patterns of a wide variety of materials. In this process, a laser pulse is focused through a transparent support and absorbed in a thin donor film, propelling material onto an adjacent acceptor substrate. For fluid materials, this transfer occurs through the formation of a narrow liquid jet, which eventually pinches off due to surface tension. This thesis examines in detail the fluid mechanics of the jet formation process occurring in LIFT. The main focus is on a variant of LIFT known as blister-actuated LIFT (BA-LIFT), in which the laser pulse is absorbed in an ink-coated polymer layer, rapidly deforming it locally into a blister to induce liquid jet formation. The early-time response of a fluid layer to a deforming boundary is analyzed with a domain perturbation method and potential-flow simulations, revealing scalings for energy and momentum transfer to the fluid and providing physical insight on how and why a jet forms in BA-LIFT. The remaining chapters explore more complex applications and modifications of LIFT. One is the possibility of high-repetition rate printing and limits on time delay and separation between pulses imposed by a tilting effect found for adjacent jets. Another examines a focusing effect achieved by perturbing the interface with ring-shaped disturbances. The third contains an experimental study of LIFT using a silver paste as the donor material instead of a Newtonian liquid. The transfer mechanism is significantly different, although with repeated pulses at one location, a focusing effect is again observed. All three of these chapters investigate how perturbations to the interface can strongly influence the jet formation process.

  10. The pressure relaxation of liquid jets after isochoric heating

    SciTech Connect

    Chen, X.M.; Schrock, V.E. . Dept. of Nuclear Engineering)

    1990-01-01

    During isochoric heating by fast neutron irradiation, a high pressure is almost instantaneously built up inside the falling liquid jets in a HYLIFE (ICF) reactor. It has been suggested that the jets will breakup as a consequence of negative pressure occurring during the relaxation. This is important to both the subsequent condensation process and the chamber wall design. In this paper the mechanism of the relaxation of liquid jets after isochoric heating has been studied with both incompressible and compressible models. The transient pressure field predicted is qualitatively similar for both models and reveals a strongly peaked tension in the wake of a rarefaction wave. The pressure then rises monotonically in radius to zero pressure on the boundary. The incompressible approximation greatly over predicts the peak tension, which increases with time as the rarefaction wave moves toward the center of the jet. Since the tension distribution is as a narrow spike rather than uniform, a cylindrical fracture is the most likely mode of failure. The paper also discusses the available methods for estimating liquid tensile strength.

  11. METHOD OF LIQUID-LIQUID EXTRACTION OF BLOOD SURROGATES FOR ASSESSING HUMAN EXPOSURE TO JET FUEL

    EPA Science Inventory

    A baseline method of liquid?liquid extraction for assessing human exposure to JP-8 jet fuel was established by extracting several representative compounds ranging from very volatile to semi-volatile organic compounds, including benzene, toluene, nonane, decane, undecane, tridec...

  12. Production of jet fuels from coal derived liquids

    SciTech Connect

    Fleming, B.A.; Fox, J.D.; Furlong, M.W.; Masin, J.G.; Sault, L.P.; Tatterson, D.F. . Research and Development Dept.); Fornoff, L.L.; Link, M.A.; Stahlnecker, E.; Torster, K. )

    1988-09-01

    Amoco and Lummus Crest have developed seven cases for upgrading by-product liquids from the Great Plains Coal Gasification Plant to jet fuels, and in several of the cases, saleable chemicals in addition to jet fuels. The analysis shows that the various grades of jet fuel can be produced from the Great Plains tar oil, but not economically. However, the phenolic and naphtha streams do have the potential to significantly increase (on the order of $10--15 million/year) the net revenues at Great Plains by producing chemicals, especially cresylic acid, cresol, and xylenol. The amount of these chemicals, which can be marketed, is a concern, but profits can be generated even when oxygenated chemical sales are limited to 10 percent of the US market. Another concern is that while commercial processes exist to extract phenolic mixtures, these processes have not been demonstrated with the Great Plains phenolic stream. 9 refs., 24 figs., 14 tabs.

  13. Parametric Investigation of Liquid Jets in Low Gravity

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2005-01-01

    An axisymmetric phase field model is developed and used to model surface tension forces on liquid jets in microgravity. The previous work in this area is reviewed and a baseline drop tower experiment selected for model comparison. This paper uses the model to parametrically investigate the influence of key parameters on the geysers formed by jets in microgravity. Investigation of the contact angle showed the expected trend of increasing contact angle increasing geyser height. Investigation of the tank radius showed some interesting effects and demonstrated the zone of free surface deformation is quite large. Variation of the surface tension with a laminar jet showed clearly the evolution of free surface shape with Weber number. It predicted a breakthrough Weber number of 1.

  14. Jet-noise reduction through liquid-base foam injection.

    NASA Technical Reports Server (NTRS)

    Manson, L.; Burge, H. L.

    1971-01-01

    An experimental investigation has been made of the sound-absorbing properties of liquid-base foams and of their ability to reduce jet noise. Protein, detergent, and polymer foaming agents were used in water solutions. A method of foam generation was developed to permit systematic variation of the foam density. The investigation included measurements of sound-absorption coefficents for both plane normal incidence waves and diffuse sound fields. The intrinsic acoustic properties of foam, e.g., the characteristic impedance and the propagation constant, were also determined. The sound emitted by a 1-in.-diam cold nitrogen jet was measured for subsonic (300 m/sec) and supersonic (422 m/sec) jets, with and without foam injection. Noise reductions up to 10 PNdB were measured.

  15. Magnetohydrodynamic Stability of a Streaming Gas Core Liquid Jet

    NASA Astrophysics Data System (ADS)

    Radwan, Ahmed E.; Elazab, Samia S.

    1989-01-01

    The magnetohydrodynamic instability of a streaming fluid jet (radius R0) ambient with streaming liquid is studied to the axisymmetric (m{=}0) and the non-axisymmetric (m{≥slant}1) disturbances (m is the azimuthal wavenumber). When the surface tension effect is suppressed; the jet is stable to all m{≥slant}0 for all wavelengths. In the absence of the magnetic field; the model is stable to all m{≥slant}1 for all wavelengths and also stable to m{=}0 if the perturbed wavelength is equal to or shorter than 2π R0. While it is unstable only to m{=}0 if the perturbed wavelength is longer than 2π R0. The streaming has a destabilizing effect. If the magnetic fields are sufficiently high, so that the Alfvén wave velocities are greater than the streaming velocities of the two fluids; the jet is stable against all disturbances and vice versa.

  16. Laser-induced jet formation in liquid films

    NASA Astrophysics Data System (ADS)

    Brasz, Frederik; Arnold, Craig

    2014-11-01

    The absorption of a focused laser pulse in a liquid film generates a cavitation bubble on which a narrow jet can form. This is the basis of laser-induced forward transfer (LIFT), a versatile printing technique that offers an alternative to inkjet printing. We study the influence of the fluid properties and laser pulse energy on jet formation using numerical simulations and time-resolved imaging. At low energies, surface tension causes the jet to retract without transferring a drop, and at high energies, the bubble breaks up into a splashing spray. We explore the parameter space of Weber number, Ohnesorge number, and ratio of film thickness to maximum bubble radius, revealing regions where uniform drops are transferred.

  17. Restraint of Liquid Jets by Surface Tension in Microgravity Modeled

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2001-01-01

    Tension in Microgravity Modeled Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, jets must be contained by surface tension forces. Recent NASA experiments in microgravity (Tank Pressure Control Experiment, TPCE, and Vented Tank Pressure Experiment, VTRE) resulted in a wealth of data about jet behavior in microgravity. VTRE was surprising in that, although it contained a complex geometry of baffles and vanes, the limit on liquid inflow was the emergence of a liquid jet from the top of the vane structure. Clearly understanding the restraint of liquid jets by surface tension is key to managing fluids in low gravity. To model this phenomenon, we need a numerical method that can track the fluid motion and the surface tension forces. The fluid motion is modeled with the Navier-Stokes equation formulated for low-speed incompressible flows. The quantities of velocity and pressure are placed on a staggered grid, with velocity being tracked at cell faces and pressure at cell centers. The free surface is tracked via the introduction of a color function that tracks liquid as 1/2 and gas as -1/2. A phase model developed by Jacqmin is used. This model converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly. Previous attempts at this formulation have been criticized for smearing the interface. However, by sharpening the phase

  18. Production of jet fuel from coal-derived liquids

    SciTech Connect

    Furlong, M.W.; Fox, J.D.; Masin, J.G.; Soderberg, D.J.

    1990-01-01

    Amoco and Lummus Crest, under a contract with the United States Department of Energy, are evaluating the process options and economics for upgrading the naphtha, crude phenols, and tar oil by-products from the Great Plains Coal Gasification Plant to jet fuels and other salable products. Conceptual processing schemes for maximizing the production of Grades JP-4, JP-8, and high-density (JP-8X) jet fuels, for maximizing profits, and for profitable production of each of the three jet fuels from the by-product liquids have been developed. Economic analyses of the designs show that jet fuel can be produced from the by-products, but not economically. However, jet fuel production could be subsidized profitably by processing the phenolic and naphtha streams to cresols, phenols, BTX, and other valuable chemical by-products. Uncertainties in the studies are marketability of the chemical by-products, replacement fuel costs, and viable schemes to process the phenol stream, among others. 8 figs., 2 tabs.

  19. Helical instability of a rotating viscous liquid jet

    NASA Astrophysics Data System (ADS)

    Kubitschek, J. P.; Weidman, P. D.

    2007-11-01

    Vertical rotating viscous liquid jet experiments show a clear preference for helical instabilities that evolve from initially planar disturbances at large rotation rates for fixed fluid properties. The laboratory setup for the experiments described herein was chosen as the nearest earth-based equivalent to a uniformly rotating viscous liquid column in the absence of gravity. In the ideal situation with stress-free boundaries, the preferred modes of linear temporal instability are theoretically known over the entire physical domain spanned by the Hocking parameter L =γ/ρa3Ω2 and the rotational Reynolds number Re =a2Ω/ν, where a is the column radius, Ω is its uniform angular velocity, and ρ, ν, and γ are, respectively, the fluid density, kinematic viscosity, and surface tension. The theoretical results show that instability in L-Re parameter space is dominated by three mode types: The axisymmetric mode, the n ≥2 planar modes, and the first n =1 spiral mode. Experiments reveal that, in the L-Re region for which the uniformly rotating liquid column is dominated by planar modes of instability, the rotating liquid jet spontaneously gives rise to planar disturbances of mode n ≥2 that rapidly evolve into helical instabilities. However, these observed instabilities are not the spiral normal modes that exist for n ≥1 as posited in linear stability theory. In spite of obvious fundamental differences between the rotating liquid jet and the uniformly rotating liquid column, some remarkable similarities associated with initial growth rates, angular frequencies, and mode transitions between the two systems are found.

  20. Equilibrium pellet and liquid jet shape under high ablation pressures

    NASA Astrophysics Data System (ADS)

    Parks, P. B.; Rosenbluth, M. N.

    1998-05-01

    Owing to the nonspherical nature of the heat deposition in the pellet ablation cloud by energy loss of incident plasma electrons streaming parallel to the uniform magnetic field, a nonuniform pressure distribution develops at the pellet surface. This can lead to deformation of "soft" cryogenic pellets exposed to high temperature and high density magnetized plasmas. The effect of deformation on the burning rate and stability of the condensed phase is evaluated for pellets and liquid jets.

  1. Role of Weber number in the primary breakup of liquid jets in crossflow

    NASA Astrophysics Data System (ADS)

    Pai, Madhusudan; Bermejo-Moreno, I.; Desjardins, Olivier; Pitsch, Heinz

    2009-11-01

    Atomization of liquid fuel controls the combustion efficiency and pollutant emissions from internal combustion engines and gas turbines. A liquid jet injected into a crossflow breaks up by developing liquid surface instabilities and deformations due to aerodynamic sources and liquid jet turbulence, among other causes. There is a pressing need to understand the origin and role of these instabilities in the breakup of a liquid jet. These instabilities can be accurately quantified in detailed numerical simulations of liquid jets. A spectrally-refined interface (SRI) tracking scheme for interface transport coupled to an accurate and robust Navier-Stokes/Ghost-fluid method gas-phase solver is employed to perform large-scale detailed numerical simulations of liquid jets in a laminar crossflow. The liquid Weber number controls the tendency of a liquid jet to break up, while the liquid Reynolds number controls the range of length scales in the liquid jet turbulence. The interplay and role of these phenomena in the primary breakup of liquid jets is quantified through a parametric study. Existing models for turbulent primary breakup of liquid jets in crossflow are reviewed based on the numerical results.

  2. Breakup characteristics of a liquid jet in subsonic crossflow

    NASA Astrophysics Data System (ADS)

    Gopala, Yogish

    This thesis describes an experimental investigation of the breakup processes involved in the formation of a spray created by a liquid jet injected into a gaseous crossflow. This work is motivated by the utilization of this method to inject fuel in combustors and afterburners of airplane engines. This study aims to develop a better understanding of the spray breakup processes and to provide better experimental inputs to improve the fidelity of numerical models. A review of the literature in this field identified the fundamental physical processes involved in the breakup of the spray and the dependence of spray properties on operating conditions. The time taken for the liquid column to break up into ligaments and droplets, the primary breakup time and the effect of injector geometry on the spray formation processes and spray properties as the key research areas in which research done so far has been inadequate. Determination of the location where the liquid column broke up was made difficult by the presence of a large number of droplets surrounding it. This study utilizes the liquid jet light guiding technique that enables accurate measurements of this location for a wide range of operating conditions. Prior to this study, the primary breakup time was thought to be a function the density ratio of the liquid and the gas, the diameter of the orifice and the air velocity. This study found that the time to breakup of the liquid column depends on the Reynolds number of the liquid jet. This suggests that the breakup of a turbulent liquid jet is influenced by both the aerodynamic breakup processes and the turbulent breakup processes. Observations of the phenomenon of the liquid jet splitting up into two or more jets were made at some operating conditions with the aid of the new visualization technique. Finally, this thesis investigates the effect of injector geometry on spray characteristics. One injector was a round edged orifice with a length to diameter ratio of 1 and a

  3. Liquid jet breakup regimes at supercritical pressures

    DOE PAGESBeta

    Oefelein, Joseph C.; Dahms, Rainer Norbert Uwe

    2015-07-23

    Previously, a theory has been presented that explains how discrete vapor–liquid interfaces become diminished at certain high-pressure conditions in a manner that leads to well known qualitative trends observed from imaging in a variety of experiments. Rather than surface tension forces, transport processes can dominate over relevant ranges of conditions. In this paper, this framework is now generalized to treat a wide range of fuel-oxidizer combinations in a manner consistent with theories of capillary flows and extended corresponding states theory. Different flow conditions and species-specific molecular properties are shown to produce distinct variations of interfacial structures and local free molecularmore » paths. These variations are shown to occur over the operating ranges in a variety of propulsion and power systems. Despite these variations, the generalized analysis reveals that the envelope of flow conditions at which the transition from classical sprays to diffusion-dominated mixing occurs exhibits a characteristic shape for all liquid–gas combinations. As a result, for alkane-oxidizer mixtures, it explains that these conditions shift to higher pressure flow conditions with increasing carbon number and demonstrates that, instead of widely assumed classical spray atomization, diffusion-dominated mixing may occur under relevant high-pressure conditions in many modern devices.« less

  4. Liquid jet breakup regimes at supercritical pressures

    SciTech Connect

    Oefelein, Joseph C.; Dahms, Rainer Norbert Uwe

    2015-07-23

    Previously, a theory has been presented that explains how discrete vapor–liquid interfaces become diminished at certain high-pressure conditions in a manner that leads to well known qualitative trends observed from imaging in a variety of experiments. Rather than surface tension forces, transport processes can dominate over relevant ranges of conditions. In this paper, this framework is now generalized to treat a wide range of fuel-oxidizer combinations in a manner consistent with theories of capillary flows and extended corresponding states theory. Different flow conditions and species-specific molecular properties are shown to produce distinct variations of interfacial structures and local free molecular paths. These variations are shown to occur over the operating ranges in a variety of propulsion and power systems. Despite these variations, the generalized analysis reveals that the envelope of flow conditions at which the transition from classical sprays to diffusion-dominated mixing occurs exhibits a characteristic shape for all liquid–gas combinations. As a result, for alkane-oxidizer mixtures, it explains that these conditions shift to higher pressure flow conditions with increasing carbon number and demonstrates that, instead of widely assumed classical spray atomization, diffusion-dominated mixing may occur under relevant high-pressure conditions in many modern devices.

  5. An Experimental Study of Droplets Produced by Plunging Breakers

    NASA Astrophysics Data System (ADS)

    Wang, D.; Dai, D.; Liu, X.; Duncan, J. H.

    2012-11-01

    The production of droplets by breaking water waves greatly affects the heat, mass and momentum transfer between the atmosphere and the sea surface. In this study, the production of droplets by mechanically generated breaking water waves was explored in a wave tank. The breakers were generated from dispersively focused wave packets (average frequency 1.15 Hz) using a programmable wave maker. Two overall wave maker amplitudes were used to create a strong spilling and a strong plunging breaker. The profile histories of the breaking wave crests along the center plane of the tank were measured with a cinematic laser-induced fluorescence technique, while the droplet diameter distributions and motions were measured at different locations along a horizontal line, which is 1 cm above the maximum height of the wave crest, using a double-pulsed cinematic shadowgraph technique. It is found that droplets are primarily generated when the plunging jet of the wave generates strong turbulence during impact with the wave's front face and when large air bubbles, entrapped during the plunging process, rise to the free surface and pop. The differences between the generation mechanisms in spilling and plunging breakers is highlighted. This work is supported by the Ocean Sciences Division of the National Science Foundation.

  6. Effect of gas mass flux on cryogenic liquid jet breakup

    NASA Astrophysics Data System (ADS)

    Ingebo, R. D.

    A scattered-light scanning instrument developed at NASA Lewis Research Center was used to measure the characteristic drop size of clouds of liquid nitrogen droplets. The instrument was calibrated with suspensions of monosized polystyrene spheres. In this investigation of the mechanism of liquid nitrogen jet disintegration in a high-velocity gas flow, the Sauter mean diameter, D32, was found to vary inversely with the nitrogen gas mass flux raised to the power 1.33. Values of D32 varied from 5 to 25 microns and the mass flux exponent of 1.33 agrees well with theory for liquid jet breakup in high-velocity gas flows. The loss of very small droplets due to the high vaporization rate of liquid nitrogen was avoided by sampling the spray very close to the atomizer, i.e., 1.3 cm downstream of the nozzle orifice. The presence of high velocity and thermal gradients in the gas phase also made sampling of the particles difficult. As a result, it was necessary to correct the measurements for background noise produced by both highly turbulent gas flows and thermally induced density gradients in the gas phase.

  7. Spray measurements of aerothermodynamic effect on disintegrating liquid jets

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1991-01-01

    An experimental investigation was made to determine the effect of atomizing gas mass flux and temperature on liquid jet breakup in sonic velocity gas flow. Characteristic drop size data were obtained by using the following atomizing gases: nitrogen, argon, and helium to breakup water jets in high velocity gas flow. A scattered light scanning instrument developed at Lewis Research Center was used to measure Sauter mean diameter (SMD). The three gases gave a molecular weight range of 4 to 40 and atomizing gas mass flux and temperature were varied from 6 to 50 g/sq cm and 275-400 K, respectively. The ratio of liquid jet diameter to SMD, D(sub 0)/D(sub 32), was correlated with aerodynamic and liquid-surface force ratios, i.e., the product of the Weber and Reynolds number, We Re, the gas to liquid density ratio, rho(sub g)/rho(sub 1) g and also the molecular scale dimensionless group, rho(sub 1)(Vm exp 3)/ mu(sub 1) g, to give the following expression: D(sub 0)/D(sub 32) = 0.90 x 10(exp -8) x (We Re rho sub g/rho sub 1)exp 0.44 x (rho sub 1 Vm exp 3/mu sub 1 g)exp 0.67 where We Re = ((rho sub g)exp 2(D sub 0)exp 2(V sub C)exp3))/ mu sub 1 sigma, mu sub 1 is liquid viscosity, sigma is surface tension, V sub C is the acoustic gas velocity, V sub m is the RMS velocity of gas molecules, and g is the acceleration of gas molecules due to gravity. Good agreement was obtained with atomization theory for liquid-jet breakup in the regime of aerodynamic stripping. Also, due to its low molecular weight and high acoustic velocity, helium was considerably more effective than nitrogen or argon in producing small-droplet sprays with values of D(sub 32) on the order of 5 microns.

  8. Spray Characterization of Gas-to-Liquid Synthetic Jet Fuels

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza

    2011-11-01

    In the recent years, development of alternative jet fuels is gaining importance owing to the demand for cleaner combustion. In addition to having energy density that matches those of conventional fuels, alternate jet fuels need to possess vital qualities such as rapid atomization and vaporization, quick re-ignition at high altitude, less emission, and poses ease of handling. The fuel preparatory steps (atomization and vaporization) and mixing in a combustion chamber play a crucial role on the subsequent combustion and emission characteristics. Gas-to-Liquid (GTL) synthetic jet fuel obtained from Fischer-Tropsch synthesis has grabbed the global attention due to its cleaner combustion characteristics as a result of the absence of aromatics and sulphur. As a part of an on-going joint effort between Texas A&M at Qatar (TAMUQ), Rolls-Royce (UK), and German Aerospace Laboratory (DLR), a spray characterization experimental facility is set up at TAMUQ to study the spray characteristics of GTL fuel and highlights the influence of change in fuel composition on the spray characteristics. In this work, spray characteristics such as droplet size, velocity, and distribution of different GTL fuel blends is investigated and compared with the spray characteristics of conventional JetA1 fuel. Supported by Qatar Science and Technology Park, QSTP.

  9. Production of jet fuel from coal-derived liquids

    SciTech Connect

    Furlong, M.W.; Fox, J.D.; Masin, J.G.; Soderberg, D.J.

    1987-01-01

    Amoco and Lummus Crest are evaluating the process options and economics for upgrading the naphtha, crude phenols, and tar oil by-products from the Great Plains Coal Gasification Plant to jet fuels and other salable products. Analytical characterizations of these three by-products indicate the range of products that can be manufactured from each, and potential problems which could be encountered during refining. These characterizations, along with limited experimental data and Amoco's proprietary process models, were used to design conceptual processing schemes for maximizing the production of Grades JP-4, JP-8, and high density (JP-8X) jet fuels from the by-product liquids. In addition to the maximum jet fuel schemes, conceptual designs have also been formulated for maximizing profits from refining of the Great Plains by-products. Conceptual processing schemes for profitable production of JP-4, JP-8, and JP-8X have been developed, as has a maximum profit'' case. All four of these additional cases have now been transferred to Lummus for design and integration studies. Development of these schemes required the use of linear programming technology. This technology includes not only conventional refining processes which have been adapted for use with coal-derived liquids (e.g. hydrotreating, hydrocracking), but also processes which may be uniquely suited to the Great Plains by-products such as cresylic acid extraction, hydordealkylation, and needle coking. 6 figs., 3 tabs.

  10. Initial instability of round liquid jet at subcritical and supercritical environments

    NASA Astrophysics Data System (ADS)

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2016-07-01

    In the present experimental work, the behavior of laminar liquid jet in its own vapor as well as supercritical fluid environment is conducted. Also the study of liquid jet injection into nitrogen (N2) environment is carried out at supercritical conditions. It is expected that the injected liquid jet would undergo thermodynamic transition to the chamber condition and this would alter the behavior of the injected jet. Moreover at such conditions there is a strong dependence between thermodynamic and fluid dynamic processes. Thus the thermodynamic transition has its effect on the initial instability as well as the breakup nature of the injected liquid jet. In the present study, the interfacial disturbance wavelength, breakup characteristics, and mixing behavior are analysed for the fluoroketone liquid jet that is injected into N2 environment as well as into its own vapor at subcritical to supercritical conditions. It is observed that at subcritical chamber conditions, the injected liquid jet exhibits classical liquid jet characteristics with Rayleigh breakup at lower Weber number and Taylor breakup at higher Weber number for both N2 and its own environment. At supercritical chamber conditions with its own environment, the injected liquid jet undergoes sudden thermodynamic transition to chamber conditions and single phase mixing characteristics is observed. However, the supercritical chamber conditions with N2 as ambient fluid does not have significant effect on the thermodynamic transition of the injected liquid jet.

  11. Functionalization of carbon nanowalls by plasma jet in liquid treatment

    NASA Astrophysics Data System (ADS)

    Ionita, Maria D.; Vizireanu, Sorin; Stoica, Silviu D.; Ionita, Mariana; Pandele, Andreea M.; Cucu, Ana; Stamatin, Ioan; Nistor, Leona C.; Dinescu, Gheorghe

    2016-02-01

    Submerged in liquid plasma treatment is a new approach for nanomaterials functionalization. This paper presents a surfactant free method for functionalization of graphene nano-platelets derived from carbon nanowalls through plasma jet treatment of their water suspensions. The untreated and under-liquid plasma treated suspensions were characterized in terms of their UV-Vis absorption, zeta-size, zeta-potential, pH, and conductivity. Investigation of dried material revealed that the graphene nano-sheets morphology and structure have been preserved, showing also new oxygen functional groups bonded to the carbon network after in liquid plasma treatment. The results demonstrate the efficiency of this technique in changing the properties of carbon nanowalls suspensions and also in getting functionalized multilayered graphene sheets.

  12. Nanoscale Liquid Jets Shape New Line of Business

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Just as a pistol shrimp stuns its prey by quickly closing its oversized claw to shoot out a shock-inducing, high-velocity jet of water, NanoMatrix, Inc., is sending shockwaves throughout the nanotechnology world with a revolutionary, small-scale fabrication process that uses powerful liquid jets to cut and shape objects. Emanuel Barros, a former project engineer at NASA s Ames Research Center, set out to form the Santa Cruz, California-based NanoMatrix firm and materialize the micro/nano cutting process partially inspired by the water-spewing crustacean. Early on in his 6-year NASA career, Barros led the development of re-flown flight hardware for an award-winning Spacelab project called NeuroLab. This project, the sixteenth and final Spacelab mission, focused on a series of experiments to determine the effects of microgravity on the development of the mammalian nervous system.

  13. Modeling of Turbulence Effects on Liquid Jet Atomization and Breakup

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P.; Chen, C. P.

    2005-01-01

    Recent experimental investigations and physical modeling studies have indicated that turbulence behaviors within a liquid jet have considerable effects on the atomization process. This study aims to model the turbulence effect in the atomization process of a cylindrical liquid jet. Two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (blob model) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup by O Rourke et al, are further extended to include turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and the initial flow conditions. For the secondary breakup, an additional turbulence force acted on parent drops is modeled and integrated into the TAB governing equation. The drop size formed from this breakup regime is estimated based on the energy balance before and after the breakup occurrence. This paper describes theoretical development of the current models, called "T-blob" and "T-TAB", for primary and secondary breakup respectivety. Several assessment studies are also presented in this paper.

  14. Acoustic excitation of liquid fuel droplets and coaxial jets

    NASA Astrophysics Data System (ADS)

    Rodriguez, Juan Ignacio

    This experimental study focuses on two important problems relevant to acoustic coupling with condensed phase transport processes, with special relevance to liquid rocket engine and airbreathing engine combustion instabilities. The first part of this dissertation describes droplet combustion characteristics of various fuels during exposure to external acoustical perturbations. Methanol, ethanol, a liquid synthetic fuel derived from coal gasification via the Fischer-Tropsch process, and a blend of aviation fuel and the synthetic fuel are used. During acoustic excitation, the droplet is situated at or near a pressure node condition, where the droplet experiences the largest velocity perturbations, and at or near a pressure antinode condition, where the droplet is exposed to minimal velocity fluctuations. For unforced conditions, the values of the droplet burning rate constant K of the different fuels are consistent with data in the literature. The location of the droplet with respect to a pressure node or antinode also has a measurable effect on droplet burning rates, which are different for different fuels and in some cases are as high as 28% above the unforced burning rate value. Estimates of flame extinction due to acoustic forcing for different fuels are also obtained. The second part of this work consists of an experimental study on coaxial jet behavior under non-reactive, cryogenic conditions, with direct applications to flow mixing and unstable behavior characterization in liquid rocket engines. These experiments, conducted with nitrogen, span a range of outer to inner jet momentum flux ratios from 0.013 to 23, and explore subcritical, nearcritical and supercritical pressure conditions, with and without acoustic excitation, for two injector geometries. Acoustic forcing at 3 kHz is utilized to maximize the pressure fluctuations within the chamber acting on the jet, reaching maximum values of 4% of the mean chamber pressure. The effect of the magnitude and phase

  15. Impinging jet spray formation using non-Newtonian liquids

    NASA Astrophysics Data System (ADS)

    Rodrigues, Neil S.

    Over the past two decades there has been a heightened interest in implementing gelled propellants for rocket propulsion, especially for hypergolic bi-propellants such as monomethylhydrazine (MMH) and nitrogen tetroxide oxidizer (NTO). Due to the very high level of toxicity of hypergolic liquid rocket propellants, increasing safety is an important area of need for continued space exploration and defense operations. Gelled propellants provide an attractive solution to meeting the requirements for safety, while also potentially improving performance. A gelling agent can be added to liquid propellants exhibiting Newtonian behavior to transform the liquid into a non-Newtonian fluid with some solid-like behavior, i.e. a gel. Non-Newtonian jet impingement is very different from its Newtonian counterpart in terms of fluid flow, atomization, and combustion. This is due to the added agents changing physical properties such as the bulk rheology (viscosity) and interfacial rheology (surface tension). Spray characterization of jet impingement with Newtonian liquids has been studied extensively in existing literature. However, there is a scarcity in literature of studies that consider the spray characterization of jet impingement with gelled propellants. This is a rather critical void since a major tradeoff of utilizing gelled propellants is the difficulty with atomization due to the increased effective viscosity. However, this difficulty can be overcome by using gels that exhibit shear-thinning behavior---viscosity decreases with increasing strain rate. Shear-thinning fluids are ideal because they have the distinct advantage of only flowing easily upon pressure. Thereby, greatly reducing the amount of propellant that could be accidentally leaked during both critical functions such as liftoff or engagement in the battlefield and regular tasks like refilling propellant tanks. This experimental work seeks to help resolve the scarcity in existing literature by providing drop size

  16. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur; McClure, John; Avila, Ricardo

    2005-01-01

    Torque and plunge force during the initial plunge phase in Friction Stir Welding were measured for a 0.5 inch diameter pin entering a 2219 aluminum alloy plate. Weld structures were preserved for metallographic observation by making emergency stops at various plunge depths. The plunging pin tool is seen to be surrounded by a very fine grained layer of recrystallized metal extending substantially below the bottom of the pin, implying a shear interface in the metal below and not at the tool-metal interface. Torque and plunge force during the initial plunge phase in Friction Stir Welding are calculated from a straight forward model based on a concept to plastic flow in the vicinity of the plunging tool compatible with structural observations. The concept: a disk of weld metal seized to and rotating with the bottom of the pin is squeezed out laterally by the plunge force and extruded upwards in a hollow cylinder around the tool. As the shear surface separating rotating disk from stationary weld metal engulfs fresh metal, the fresh metal is subjected to severe shear deformation, which results in its recrystallization. Encouraging agreement between computations and measured torque and plunge force is obtained.

  17. Numerical Simulation of Liquid Jet Atomization Including Turbulence Effects

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P.; Chen, C. P.; Balasubramanyam, M. S.

    2005-01-01

    This paper describes numerical implementation of a newly developed hybrid model, T-blob/T-TAB, into an existing computational fluid dynamics (CFD) program for primary and secondary breakup simulation of liquid jet atomization. This model extend two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (blob model) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup by O'Rourke and Amsden to include turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and the initial flow conditions. For the secondary breakup, an additional turbulence force acted on parent drops is modeled and integrated into the TAB governing equation. Several assessment studies are presented and the results indicate that the existing KH and TAB models tend to under-predict the product drop size and spray angle, while the current model provides superior results when compared with the measured data.

  18. Production of jet fuels from coal-derived liquids

    SciTech Connect

    Knudson, C.L.

    1990-06-01

    Samples of jet fuel (JP-4, JP-8, JP-8X) produced from the liquid by-products of the gasification of lignite coal from the Great Plains Gasification Plant were analyzed to determine the quantity and type of organo-oxygen compounds present. Results were compared to similar fuel samples produced from petroleum. Large quantities of oxygen compounds were found in the coal-derived liquids and were removed in the refining process. Trace quantities of organo-oxygenate compounds were suspected to be present in the refined fuels. Compounds were identified and quantified as part of an effort to determine the effect of these compounds in fuel instability. Results of the analysis showed trace levels of phenols, naphthols, benzofurans, hexanol, and hydrogenated naphthols were present in levels below 100 ppM. 9 figs., 3 tabs.

  19. Atmospheric pressure plasma jets interacting with liquid covered tissue: touching and not-touching the liquid

    NASA Astrophysics Data System (ADS)

    Norberg, Seth A.; Tian, Wei; Johnsen, Eric; Kushner, Mark J.

    2014-11-01

    In the use of atmospheric pressure plasma jets in biological applications, the plasma-produced charged and neutral species in the plume of the jet often interact with a thin layer of liquid covering the tissue being treated. The plasma-produced reactivity must then penetrate through the liquid layer to reach the tissue. In this computational investigation, a plasma jet created by a single discharge pulse at three different voltages was directed onto a 200 µm water layer covering tissue followed by a 10 s afterglow. The magnitude of the voltage and its pulse length determined if the ionization wave producing the plasma plume reached the surface of the liquid. When the ionization wave touches the surface, significantly more charged species were created in the water layer with H3O+aq, O3-aq, and O2-aq being the dominant terminal species. More aqueous OHaq, H2O2aq, and O3aq were also formed when the plasma plume touches the surface. The single pulse examined here corresponds to a low repetition rate plasma jet where reactive species would be blown out of the volume between pulses and there is not recirculation of flow or turbulence. For these conditions, NxOy species do not accumulate in the volume. As a result, aqueous nitrites, nitrates, and peroxynitrite, and the HNO3aq and HOONOaq, which trace their origin to solvated NxOy, have low densities.

  20. Impulsive plunging wave breaking downstream of a bump in a shallow water flume—Part I: Experimental observations

    NASA Astrophysics Data System (ADS)

    Kang, Donghoon; Ghosh, Surajeet; Reins, George; Koo, Bonguk; Wang, Zhaoyuan; Stern, Frederick

    2012-07-01

    The plunging wave-breaking process for impulsive flow over a bump in a shallow water flume is described, which is relevant to ship hydrodynamics albeit for an idealized geometry since it includes the effects of wave-body interactions and the wave breaking direction is opposite to the mean flow. This paper consists of two parts, which deal with experimental measurements and numerical simulations, respectively. In Part I, ensemble-averaged measurements are conducted, including the overall flume flow, 2-D particle image velocimetry (PIV) center-plane velocities, turbulence inside the breaking wave, and bottom pressures under the breaking wave. A series of individual plunging wave-breaking tests were conducted, which all followed a similar time line consisting of startup, steep wave formation, plunging wave breaking, and chaotic wave breaking swept downstream time phases. The plunging wave breaking process consists of four repeated plunging events each with three [jet impact (plunge), oblique splash and vertical jet] sub-events, which were identified first using a complementary computational fluid dynamics (CFD) study. Video images with red dye display the plunging wave breaking events and sub-events. The wave profile at maximum height, first plunge, bump and wave breaking vortex and entrapped air tube trajectories, entrapped air tube diameters, kinetic, potential, and total energy are analyzed. Similarities and differences are discussed with the previous deep water or sloping beach experimental and computational studies. The numerical simulations using the exact experimental initial and boundary conditions are presented in Part II of this paper.

  1. Korteweg-de Vries solitons on electrified liquid jets.

    PubMed

    Wang, Qiming; Papageorgiou, Demetrios T; Vanden-Broeck, Jean-Marc

    2015-06-01

    The propagation of axisymmetric waves on the surface of a liquid jet under the action of a radial electric field is considered. The jet is assumed to be inviscid and perfectly conducting, and a field is set up by placing the jet concentrically inside a perfectly cylindrical tube whose wall is maintained at a constant potential. A nontrivial interaction arises between the hydrodynamics and the electric field in the annulus, resulting in the formation of electrocapillary waves. The main objective of the present study is to describe nonlinear aspects of such axisymmetric waves in the weakly nonlinear regime, which is valid for long waves relative to the undisturbed jet radius. This is found to be possible if two conditions hold: the outer electrode radius is not too small, and the applied electric field is sufficiently strong. Under these conditions long waves are shown to be dispersive and a weakly nonlinear theory can be developed to describe the evolution of the disturbances. The canonical system that arises is the Kortweg-de Vries equation with coefficients that vary as the electric field and the electrode radius are varied. Interestingly, the coefficient of the highest-order third derivative term does not change sign and remains strictly positive, whereas the coefficient α of the nonlinear term can change sign for certain values of the parameters. This finding implies that solitary electrocapillary waves are possible; there are waves of elevation for α>0 and of depression for α<0. Regions in parameter space are identified where such waves are found. PMID:26172797

  2. Korteweg-de Vries solitons on electrified liquid jets

    NASA Astrophysics Data System (ADS)

    Wang, Qiming; Papageorgiou, Demetrios T.; Vanden-Broeck, Jean-Marc

    2015-06-01

    The propagation of axisymmetric waves on the surface of a liquid jet under the action of a radial electric field is considered. The jet is assumed to be inviscid and perfectly conducting, and a field is set up by placing the jet concentrically inside a perfectly cylindrical tube whose wall is maintained at a constant potential. A nontrivial interaction arises between the hydrodynamics and the electric field in the annulus, resulting in the formation of electrocapillary waves. The main objective of the present study is to describe nonlinear aspects of such axisymmetric waves in the weakly nonlinear regime, which is valid for long waves relative to the undisturbed jet radius. This is found to be possible if two conditions hold: the outer electrode radius is not too small, and the applied electric field is sufficiently strong. Under these conditions long waves are shown to be dispersive and a weakly nonlinear theory can be developed to describe the evolution of the disturbances. The canonical system that arises is the Kortweg-de Vries equation with coefficients that vary as the electric field and the electrode radius are varied. Interestingly, the coefficient of the highest-order third derivative term does not change sign and remains strictly positive, whereas the coefficient α of the nonlinear term can change sign for certain values of the parameters. This finding implies that solitary electrocapillary waves are possible; there are waves of elevation for α >0 and of depression for α <0 . Regions in parameter space are identified where such waves are found.

  3. Analysis of interaction phenomena between liquid jets and materials. Revision 1

    SciTech Connect

    Kang, S.W.; Reitter, T.; Carlson, G.

    1995-04-01

    The interaction phenomena of high-velocity liquid jets impinging on a material surface have been investigated theoretically and experimentally to understand the physics of material removal by jet-machining processes. Experiments were performed to delineate conditions under which liquid jet impacts will cause mass removal, and to determine optimum jet-cutting conditions. Theoretical analyses have also been carried out to study the effects of multiple jet-droplet impacts on a target surface as a material deformation mechanism. The calculated target response and spallation behavior following droplet impacts and their physical implications are also discussed.

  4. A liquid jet setup for x-ray scattering experiments on complex liquids at free-electron laser sources

    NASA Astrophysics Data System (ADS)

    Steinke, I.; Walther, M.; Lehmkühler, F.; Wochner, P.; Valerio, J.; Mager, R.; Schroer, M. A.; Lee, S.; Roseker, W.; Jain, A.; Sikorski, M.; Song, S.; Hartmann, R.; Huth, M.; Strüder, L.; Sprung, M.; Robert, A.; Fuoss, P. H.; Stephenson, G. B.; Grübel, G.

    2016-06-01

    In this paper we describe a setup for x-ray scattering experiments on complex fluids using a liquid jet. The setup supports Small and Wide Angle X-ray Scattering (SAXS/WAXS) geometries. The jet is formed by a gas-dynamic virtual nozzle (GDVN) allowing for diameters ranging between 1 μm and 20 μm at a jet length of several hundred μm. To control jet properties such as jet length, diameter, or flow rate, the instrument is equipped with several diagnostic tools. Three microscopes are installed to quantify jet dimensions and stability in situ. The setup has been used at several beamlines performing both SAXS and WAXS experiments. As a typical example we show an experiment on a colloidal dispersion in a liquid jet at the X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source free-electron laser.

  5. A liquid jet setup for x-ray scattering experiments on complex liquids at free-electron laser sources.

    PubMed

    Steinke, I; Walther, M; Lehmkühler, F; Wochner, P; Valerio, J; Mager, R; Schroer, M A; Lee, S; Roseker, W; Jain, A; Sikorski, M; Song, S; Hartmann, R; Huth, M; Strüder, L; Sprung, M; Robert, A; Fuoss, P H; Stephenson, G B; Grübel, G

    2016-06-01

    In this paper we describe a setup for x-ray scattering experiments on complex fluids using a liquid jet. The setup supports Small and Wide Angle X-ray Scattering (SAXS/WAXS) geometries. The jet is formed by a gas-dynamic virtual nozzle (GDVN) allowing for diameters ranging between 1 μm and 20 μm at a jet length of several hundred μm. To control jet properties such as jet length, diameter, or flow rate, the instrument is equipped with several diagnostic tools. Three microscopes are installed to quantify jet dimensions and stability in situ. The setup has been used at several beamlines performing both SAXS and WAXS experiments. As a typical example we show an experiment on a colloidal dispersion in a liquid jet at the X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source free-electron laser. PMID:27370468

  6. The Bouncing Jet: A Newtonian Liquid Rebounding off a Free Surface

    NASA Astrophysics Data System (ADS)

    Thrasher, Matthew; Jung, Sunghwan; Pang, Yee Kwong; Chuu, Chih-Piao; Swinney, Harry L.

    2007-10-01

    We find that a liquid jet can bounce off a bath of the same liquid if the bath is moving horizontally with respect to the jet. Previous observations of jets rebounding off a bath (e.g. Kaye effect) have been reported only for non-Newtonian fluids, while we observe bouncing jets in a variety of Newtonian fluids, including mineral oil poured by hand. A thin layer of air separates the bouncing jet from the bath, and the relative motion replenishes the film of air. Jets with one or two bounces are stable for a range of viscosity, jet flow rate and velocity, and bath velocity. The bouncing jet phenomenon can be observed in many household fluids using only minimal equipment, making it accessible as a classroom demonstration and a science project.

  7. Effect of nozzle length-to-diameter ratio on atomization of turbulent liquid jets

    NASA Astrophysics Data System (ADS)

    Osta, Anu Ranjan

    Breakup of liquid jets is of considerable interest motivated by its applicability in combustion and propulsion systems (CI and SI engines), and agricultural fertilizer/pesticide sprays, among others. Almost all of the practical liquid injectors introduce some degree of turbulence in the liquid jet leaving the injector passage and an intriguing question is the relative importance of the liquid turbulence, cavitation, and the aerodynamic forces in the breakup processes of fuel injectors. A better design of liquid fuel injector would reduce pollutants and increase the efficiency of liquid fuel combustion processes. An experimental study to investigate the effect of nozzle length to diameter ratio on the surface properties of turbulent liquid jets in gaseous crossflow and still air was carried out. Straight cavitation-free nozzles with length/diameter ratios of 10, 20 and 40 were used to generate turbulent liquid jets in gaseous crossflow. The present study was limited to small Ohnesorge number liquid jets (Oh < 0.01) injected in crossflow within the shear breakup regime (WeG > 110). The diagnostics consisted of pulsed shadowgraphy, pulsed digital holographic microscopy and x-ray diagnostics. The x-ray tests were conducted at the Advanced Photon Source (APS) facility of Argonne National Laboratory. The test matrix was designed to maintain the same aerodynamic forces in order to isolate the effects of jet turbulence on the breakup process. The measurements included liquid jet surface properties, breakup location of the liquid column as a whole, the breakup regime transitions, bubble size inside the jet and seeding particle displacement inside the jet structures. The results include the jet surface characteristics, the liquid column breakup lengths, bubble growth, and phenomenological analysis to explain the observed results. It is observed that for a jet breakup in crossflow the injector passage length does play a role in determining the breakup length as well as

  8. Development of a liquid jet model for implementation in a 3-dimensional Eularian analysis tool

    NASA Astrophysics Data System (ADS)

    Buschman, Francis X., III

    The ability to model the thermal behavior of a nuclear reactor is of utmost importance to the reactor designer. Condensation is an important phenomenon when modeling a reactor system's response to a Loss Of Coolant Accident (LOCA). Condensation is even more important with the use of passive safety systems which rely on condensation heat transfer for long term cooling. The increasing use of condensation heat transfer, including condensation on jets of water, in safety systems puts added pressure to correctly model this phenomenon with thermal-hydraulic system and sub-channel analysis codes. In this work, a stand alone module with which to simulate condensation on a liquid jet was developed and then implemented within a reactor vessel analysis code to improve that code's handling of jet condensation. It is shown that the developed liquid jet model vastly improves the ability of COBRA-TF to model condensation on turbulent liquid jets. The stand alone jet model and the coupled liquid jet COBRA-TF have been compared to experimental data. Jet condensation heat transfer experiments by Celata et al. with a variety of jet diameters, velocities, and subcooling were utilized to evaluate the models. A sensitivity study on the effects of noncondensables on jet condensation was also carried out using the stand alone jet model.

  9. Photoionization of Sodium Salt Solutions in a Liquid Jet

    SciTech Connect

    Grieves, G. A.; Petrik, Nikolay G.; Herring-Captain, J.; Olanrewaju, B.; Aleksandrov, A.; Tonkyn, Russell G.; Barlow, Stephan E.; Kimmel, Gregory A.; Orlando, Thomas M.

    2008-06-05

    A liquid microjet was employed to examine the gas/liquid interface of aqueous sodium halide (Na+X-, X=Cl, Br, I) salt solutions. Laser excitation at 193 nm produced and removed cations of the form H+(H2O)n and Na+(H2O)m from liquid jet surfaces containing either NaCl, NaBr or NaI. The protonated water cluster yield varied inversely with increasing salt concentration, while the solvated sodium ion cluster yield varied by anion type. The distribution of H+(H2O)n at low salt concentration is identical to that observed from low-energy electron irradiated amorphous ice and the production of these clusters can be accounted for using a localized ionization/Coulomb expulsion model. Production of Na+(H2O)m is not accounted for by this model but requires ionization of solvation shell waters and a contact ion/Coulomb expulsion mechanism. The reduced yields of Na+(H2O)m from high concentration (10-2 and 10-1 M) NaBr and NaI solutions indicate a propensity for Br- and I- at the solution surfaces and interfaces. This is supported by the observation of multiphoton induced production and desorption of Br+ and I+ from the 10-2 and 10-1 M solution surfaces.

  10. Practical Electrode System for EHD Liquid Jet Generation and Properties of Liquid Pumping

    NASA Astrophysics Data System (ADS)

    Hanaoka, Ryoichi; Hosodani, Naoki; Takahashi, Ichiro; Takata, Shinzo; Fukami, Tadashi

    The coaxial cone to rod electrode system was devised to generate a powerful electrohydrodynamic (EHD) liquid jet and the performance as a liquid pump was investigated using an isothermal weakly conducting liquid, HFC43-10. When a positive dc voltage was applied to the rod electrode, the liquid spouted forcibly from the glass tube outlet installed in the top of grounded conical electrode. The properties of liquid jet: pumping pressure, flow velocity and flow pattern were examined for the electrode systems with various cone angles (θ =40°∼90°) of the conical electrode. The potential distribution in the electrode gap and the conduction current also were measured as a function of applied voltage. In this paper, it is shown that the pumping pressure is almost independent of the cone angle of electrode systems as well as the flow velocity, but is raised effectively by a partial insulating coating of rod electrode surface and the current is reduced by a coating. The potential distribution in the gap revealed the existence of heterocharge layer in the vicinity of the electrode surfaces. It is considered that the EHD pumping in this study is attributed to a space charge layer with single ionic polarity near the rod electrode, which is formed by a non-uniform electric field.

  11. Production of jet fuel from coal-derived liquids

    SciTech Connect

    Furlong, M.W.; Fox, J.D.; Masin, J.G.

    1988-01-01

    Amoco and Lummus Crest, under a contract with the United States Department of Energy, are evaluating the process options and economics for upgrading the naphtha, crude phenols, and tar oil by-products from the Great Plains Coal Gasification Plant to jet fuels and other salable products. Analytical characterizations of these three by-products indicate the range of products that can be manufactured from each, and potential problems which could be encountered during refining. These characterizations, along with limited experimental data and Amoco's proprietary process models, were used to design conceptual processing schemes for maximizing the production of Grades JP-4, JP-8, and high-density (JP-8X) jet fuels from the by-product liquids. Conceptual designs have been completed and a case for profitable production of JP-8 has been selected for experimental testing and preliminary design in the later phases of the contract. Experimental work to date has shown that the tar oil stream requires substantially more severe processing than the preliminary design estimates indicated. A new design basis is now being tested and samples of JP-4, JP-8, and JP-8X are in production, based on that new, more severe processing scheme. Six barrels of tar oil have been hydrotreated according to the first step of the processing scheme and will be used to produce barrel quantities of JP-8. 2 refs., 2 figs.

  12. Production of jet fuel from coal-derived liquids

    SciTech Connect

    Furlong, M.W.; Fox, J.D.; Masin, J.G.

    1988-01-01

    Amoco and Lummus-Crest, under a contract with the United States Department of Energy, are evaluating the process options and economics for upgrading the naphtha, crude phenols, and tar oil by-products from the Great Plains Coal Gasification Plant to jet fuels and other salable products. Analytical characterizations of these three by-products indicate the range of products that can be manufactured from each and potential problems which could be encountered during refining. These characterizations, along with limited experimental data and Amoco's proprietary process models, were used to design conceptual processing schemes for maximizing the production of Grades JP-4, JP-8, and high-density (JP-8X) jet fuels from the by-product liquids. Conceptual designs have been completed and a case for profitable production of JP-8 has been selected for experimental testing and preliminary design in the later phases of the contract. Samples of JP-4, JP-8, and JP-8X aviation turbine fuels have been manufactured from the Great Plains tar oil. Larger samples of JP-8 are nearly completed. Specification of a design basis for profitable production of JP-8 is under way. 5 figs., 4 tabs.

  13. Production of jet fuel from coal-derived liquids

    SciTech Connect

    Furlong, M.W.; Fox, J.D.; Masin, J.G.

    1989-01-01

    Amoco and Lummus-Crest, under a contract with the United States Department of Energy, are evaluating the process options and economics for upgrading the naphtha, crude phenols, and tar oil by-products from the Great Plains Coal Gasification Plant to jet fuels and other salable products. Analytical characterizations of these three by-products indicate the range of products that can be manufactured from each and potential problems which could be encountered during refining. These characterizations, along with limited experimental data and Amoco's proprietary process models, were used to design conceptual processing schemes for maximizing the production of Grades JP-4, JP-8, and high-density (JP-8X) jet fuels from the by-product liquids. Conceptual designs have been completed and a case for profitable production of JP-8 has been selected for experimental testing and preliminary design. Samples of JP-4, JP-8, and JP-8X aviation turbine fuels have been manufactured from the Great Plains tar oil. Larger samples of JP-8 have also been produced and shipped to the US Air Force for further testing. Lummus-Crest Inc. is now completing a preliminary process design for the profitable production of JP-8 and has made recommendations for a production run to produce larger quantities of JP-8. 2 figs., 3 tabs.

  14. Effect of gravity on capillary instability of liquid jets.

    PubMed

    Amini, Ghobad; Ihme, Matthias; Dolatabadi, Ali

    2013-05-01

    The effect of gravity on the onset and growth rate of capillary instabilities in viscous liquid jets is studied. To this end, a spatial linear stability analysis of Cosserat's equations is performed using a multiscale expansion technique. A dispersion relation and expressions for the perturbation amplitude are derived to evaluate the growth rate of the most unstable axisymmetric disturbance mode. Modeling results are compared with classical results in the limit of zero Bond number, confirming the validity of this approach. Expressions for the critical Weber number, demarcating the transition between convective and absolute instability are derived as functions of capillary and Bond numbers. Parametric investigations for a range of relevant operating conditions (characterized by capillary, Weber, and Bond numbers) are performed to examine the jet breakup and the perturbation growth rate. In addition to the physical insight that is obtained from this investigation, the results that are presented in this work could also be of relevance as test cases for the algorithmic development and the verification of high-fidelity multiphase simulation codes. PMID:23767630

  15. Normal Impingement of a Circular Liquid Jet onto a Screen in a Weightless Environment

    NASA Technical Reports Server (NTRS)

    Symons, E. P.

    1976-01-01

    The normal impingement of a circular liquid jet onto a fine-mesh screen in a weightless environment was investigated. Equations were developed to predict the velocity of the emerging jet on the downstream side of the screen as a function of screen and liquid parameters and of the velocity of the impinging jet. Additionally, the stability of the emerging jet was found to be Weber number dependent. In general, excepting at high velocities, the screen behaved much as a baffle, deflecting the major portion of the impinging flow.

  16. Thinning and rupture of liquid films by moving slot jets.

    PubMed

    Berendsen, Christian W J; Zeegers, Jos C H; Darhuber, Anton A

    2013-12-23

    We present systematic experiments of the rupture and dewetting of thin films of a nonvolatile polar liquid on partially wetting substrates due to a moving slot jet, which impinges at normal incidence. The relative motion was provided by a custom-built spin coater with a bidirectionally accessible axis of rotation that enabled us to measure film thickness profiles in situ as a function of substrate velocity using dual-wavelength interference microscopy. On partially wetting polymeric substrates, dry spots form in liquid films with a residual thickness well below 1 μm. We measured the density of dry spots as well as the density and size distribution of the residual droplets as a function of film thickness. In a certain parameter range, the droplet distributions exhibit pronounced anisotropy due to the effect of long-range shear stresses on the dewetting rim instability. We find robust power-law scaling relations over a large range of film thicknesses and a striking similarity to literature data obtained with ultrathin polymer melt layers on silicon substrates. PMID:24299431

  17. Measurement of intact-core length of atomizing liquid jets by image deconvolution

    NASA Technical Reports Server (NTRS)

    Woodward, Roger; Burch, Robert; Kuo, Kenneth; Cheung, Fan-Bill

    1993-01-01

    The investigation of liquid jet breakup and spray development is critical to the understanding of combustion phenomena in liquid propellant rocket engines. Much work has been done to characterize low-speed liquid jet breakup and dilute sprays, but atomizing jets and dense sprays have yielded few quantitative measurements due to their high liquid load fractions and hence their optical opacity. Focus was on a characteristic of the primary breakup process of round liquid jets, namely the length of the intact-liquid core. The specific application considered is that of shear-coaxial-type rocket engine injectors in which liquid oxygen is injected through the center post while high velocity gaseous hydrogen is injected through a concentric annulus, providing a shear force to the liquid jet surface. Real-time x ray radiography, capable of imaging through the dense two-phase region surrounding the liquid core, is used to make the measurements. The intact-liquid-core length data were obtained and interpreted using two conceptually different methods to illustrate the effects of chamber pressure, gas-to-liquid momentum ratio, and cavitation.

  18. Measurement of intact-core length of atomizing liquid jets by image deconvolution

    NASA Astrophysics Data System (ADS)

    Woodward, Roger; Burch, Robert; Kuo, Kenneth; Cheung, Fan-Bill

    1993-11-01

    The investigation of liquid jet breakup and spray development is critical to the understanding of combustion phenomena in liquid propellant rocket engines. Much work has been done to characterize low-speed liquid jet breakup and dilute sprays, but atomizing jets and dense sprays have yielded few quantitative measurements due to their high liquid load fractions and hence their optical opacity. Focus was on a characteristic of the primary breakup process of round liquid jets, namely the length of the intact-liquid core. The specific application considered is that of shear-coaxial-type rocket engine injectors in which liquid oxygen is injected through the center post while high velocity gaseous hydrogen is injected through a concentric annulus, providing a shear force to the liquid jet surface. Real-time x ray radiography, capable of imaging through the dense two-phase region surrounding the liquid core, is used to make the measurements. The intact-liquid-core length data were obtained and interpreted using two conceptually different methods to illustrate the effects of chamber pressure, gas-to-liquid momentum ratio, and cavitation.

  19. Red Giant Plunging Through Space

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Poster Version

    This image from NASA's Spitzer Space Telescope (left panel) shows the 'bow shock' of a dying star named R Hydrae, or R Hya, in the constellation Hydra.

    Bow shocks are formed where the stellar wind from a star are pushed into a bow shape (illustration, right panel) as the star plunges through the gas and dust between stars. Our own Sun has a bow shock, but prior to this image one had never been observed around this particular class of red giant star.

    R Hya moves through space at approximately 50 kilometers per second. As it does so, it discharges dust and gas into space. Because the star is relatively cool, that ejecta quickly assumes a solid state and collides with the interstellar medium. The resulting dusty nebula is invisible to the naked eye but can be detected using an infrared telescope. This bow shock is 16,295 astronomical units from the star to the apex and 6,188 astronomical units thick (an astronomical unit is the distance between the sun and Earth). The mass of the bow shock is about 400 times the mass of the Earth.

    The false-color Spitzer image shows infrared emissions at 70 microns. Brighter colors represent greater intensities of infrared light at that wavelength. The location of the star itself is drawn onto the picture in the black 'unobserved' region in the center.

  20. A new device for generating thin jets of highly-viscous liquid

    NASA Astrophysics Data System (ADS)

    Onuki, Hajime; Oi, Yuto; Tagawa, Yoshiyuki

    2015-11-01

    Thin liquid jets are applied to various devices, such as ink-jet printers. However, it is challenging to generate liquid jets of highly-viscous liquids (~ 1,000 cSt) using existing methods. To overcome this challenge, we invent a highly-viscous liquid-jet generator. This device has simple structure as follows: a wettable-thin tube is inserted into a liquid filled container. We keep the liquid level inside a thin tube deeper than that outside of the tube. When an impulsive force acts on the bottom of the container, a thin jet is generated. The jet is up to 20 times faster than the initial velocity given by the impulsive force. We successfully generate jets with a wide range of viscosity (1-1,000 cSt). We also propose the physical model based on pressure-impulse approach to rationalize its mechanism. Inside the thin tube, a gradient of pressure impulse is much larger than that outside of the tube. We verify the performance of our device experimentally. We find that the proposed model can describe all experimental results in this research. JSPS KAKENHI Grant Number 26709007.

  1. Removal of metals and ceramics by combined effects of micro liquid jet and laser pulse

    NASA Astrophysics Data System (ADS)

    Ahn, Daehwan; Seo, Changho; Kim, Dongsik

    2012-12-01

    In this work, we analyze a hybrid laser/liquid jet micromachining process for several metals and ceramics based on the optical breakdown of a microdroplet. In the process, materials are removed by the combined effects of a laser pulse and a high-speed pulsed microjet ejected from the microdroplet. The opto-hydrodynamic phenomena occurring during this process and the interaction of the laser/liquid jet with various materials, including copper, aluminum, stainless steel, alumina, and boron nitride, are investigated experimentally. The results show that the laser/liquid jet can remove the materials with substantially increased removal rates and reduced thermal side effects compared with the conventional pulsed laser ablation process. Visualization of the process reveals that the materials are partially ablated and melted by the laser pulse during the early stage of the process and that the molten material is subsequently eliminated by the hydrodynamic impact of the liquid jet.

  2. Analysis of heat transfer for a normally impinging liquid-metal slot jet

    NASA Technical Reports Server (NTRS)

    Siegel, R.

    1973-01-01

    A two-dimensional liquid-metal slot jet that is impinging normally against a uniformly heated flat plate is analyzed. The distributions of wall temperature and heat-transfer coefficient are obtained as functions of position along the plate. The liquid-metal assumptions are made that the jet is inviscid and that molecular condition is dominating heat diffusion. The solution is obtained by mapping the jet flow region into a potential plane where it occupies a strip of uniform width. The energy equation is transformed into potential coordinates, and an exact solution obtained in the strip region. Conformal mapping is then used to transform the solution into the physical plane.

  3. On the spatial stability of a liquid jet in the presence of vapor cavities

    SciTech Connect

    Lü, Ming; Ning, Zhi Lu, Mei; Yan, Kai; Fu, Juan; Sun, Chunhua

    2013-11-15

    A dispersion equation describing the effect of temperature differences on the stability of three-dimensional cylindrical liquid jets in the presence of vapor cavities is presented by the use of linear stability analysis. The mathematical model and its solving method are verified by comparing them with the data in the literature, and then the effect of temperature differences between jet and surrounding gas on the spatial stability of liquid jet is investigated. Some conclusions can be drawn from the results of this investigation: (1) the temperature difference destabilizes the liquid jet when the jet liquid is cooler than the surrounding gas, (2) the smallest atomized droplet without taking into account the effect of temperature differences is significantly larger than that when the effect of temperature differences is taken into account, (3) the effect of temperature differences on the stability of liquid jet has little relationship with azimuthal wave modes, (4) cavitation destabilizes the liquid jet when the value of the bubble volume fraction is not greater than 0.1 (0 ≤ α ≤ 0.1), and the temperature difference can weaken this effect of cavitation on the stability of liquid jet, and (5) cavitation is responsible for generating smaller droplets, the effect of cavitation on the critical wave number with and without taking into account the effect of temperature differences is quite different, and temperature difference is likely to fully restrain the effect of cavitation on the critical wave number; however, cavitation is again responsible for generating smaller droplets despite the effect of temperature differences when the bubble volume fraction α = 0.1. These findings may explain some observations of practical atomizer performance.

  4. Experimental study on gas-liquid flow characteristics of submerged air jets

    NASA Astrophysics Data System (ADS)

    Qin, S. J.; Liu, J. T.; Miao, T. C.; Wu, D. Z.

    2016-05-01

    The gas-liquid flow structure and interfacial behavior of submerged air jets were investigated experimentally using high speed digital video camera and image processing techniques. The jet pressure ratio varied from 1.8 to 4.8 in the experiment. And results from different jet nozzles were processed and compared. Statistical characteristics of the jet diameters along the axial distance were obtained and analyzed. Time series analysis was implemented to study the interface unsteadiness by calculating the gas-liquid interface deviation. The results showed that the jet diameters increase first linearly then nonlinearly and its growth rate decreases along the axial distance. The reason for the divergence between the result of this experiment and those done by other researchers was analyzed. Comparing the results of different pressure ratios and nozzle diameters, we found that larger jet pressure ratios have larger jet diameters and nozzle diameters nearly have no bearing on the distribution of dimensionless jet diameters. The interface unsteadiness in low and high pressure ratios exhibited totally distinct properties. And a minimum unsteady value was found along the axis of the air jets.

  5. Impulsive plunging wave breaking downstream of a bump in a shallow water flume—Part II: Numerical simulations

    NASA Astrophysics Data System (ADS)

    Koo, Bonguk; Wang, Zhaoyuan; Yang, Jianming; Stern, Frederick

    2012-07-01

    Part II of this two-part paper presents the simulation results of the plunging wave-breaking generated by impulsive flow over a submerged bump fixed in a shallow water flume using the exact experimental initial and boundary conditions provided in Part I of this study. The overall plunging wave breaking process is described with major wave breaking events identified: jet plunge, oblique splash and vertical jet. These major events repeat up to four times before entering the chaotic breaking phase. The plunging wave breaking process of the simulations shows a similar time line as the experiments consisting of startup, steep wave formation, plunging wave, and chaotic wave breaking swept downstream time phases. Wave breaking profile, air entrainment, velocity, vorticity, flume bottom pressure, and energy are analyzed and compared with the experimental results. The simulations qualitatively predict all four time phases, all four plunging events and their sub-events. The wave profile and location at the maximum height is very close to the experiment results. The flume flow and velocity demonstrate the same flow trend as the experiments but with reduced velocity magnitudes. The simulations show similar bottom pressure to the experiments but with large oscillations, and the post-breaking water elevations are larger as compared to the experimental results.

  6. Deformation, wave phenomena, and breakup outcomes of round nonturbulent liquid jets in uniform gaseous crossflow

    NASA Astrophysics Data System (ADS)

    Ng, Chee-Loon

    Scope and method of study. An experimental and computational research is performed to study the deformation and breakup of round nonturbulent liquid jets in uniform gaseous crossflow. Pulsed photography and shadow graphy in conjunction with high-speed imaging were used to study the wave phenomena and the droplets properties/transport dynamics of a nonturbulent liquid jet injected into a uniform crossflow within the bag breakup regime. The computational study extended the previous two-dimensional study by adding the third dimension, allowing the wave properties to be modeled. The computational simulation employed the Volume of Fluid (VOF) formulation of FLUENT, and was run on a 3-processors parallel Linux cluster and P4 desktops. The validated, time-accurate, CFD simulation analyzes the surface properties of the liquid jets within the column, bag, and shear breakup regimes by considering the effects of surface tension, liquid viscosity, and crossflow Weber number at large liquid/gas density ratios (>500) and small Ohnesorge numbers (<0.1). Findings and conclusions. Present experimental results show that the column waves along the liquid jet are attributed to Rayleigh-Taylor instabilities and the nodes layout per bag affected the breakup mechanisms of the bags. Three distinctive sizes of droplets were produced in the bag breakup regime. The size of bag-droplets normalized by the nozzle exit diameter was constant. The different trajectories for bag- and node-droplets suggested that separation of bag- and node-droplets is possible. The computational results included jet deformations, jet cross-sectional area, jet velocity, wake velocity defect, wake width, and wavelengths of column and surface waves. Present computational results yielded a similarity solution for the inner wake region. In bag breakup, the lower pressure along the sides of the jet pulled the liquid away from both the upwind and downwind surfaces of the liquid cross-section. In shear breakup, the

  7. Equilibrium configurations of a jet of an ideally conducting liquid in an external nonuniform magnetic field

    NASA Astrophysics Data System (ADS)

    Zubarev, N. M.; Zubareva, O. V.

    2016-06-01

    Possible equilibrium configurations of the free surface of a jet of an ideally conducting liquid placed in a nonuniform magnetic field are considered. The magnetic field is generated by two thin wires that are parallel to the jet and bear oppositely directed currents. Equilibrium is due to a balance between capillary and magnetic forces. For the plane symmetric case, when the jet deforms only in the plane of its cross section, two one-parameter families of exact solutions to the problem are derived using the method of conformal mapping. According to these solutions, a jet with an initially circular cross section deforms up to splitting into two separate jets. A criterion for jet splitting is derived by analyzing approximate two-parameter solutions.

  8. Analytical description of the breakup of liquid jets in air

    NASA Technical Reports Server (NTRS)

    Papageorgiou, Demetrios T.

    1993-01-01

    A viscous or inviscid cylindrical jet with surface tension in a vacuum tends to pinch due to the mechanism of capillary instability. Similarity solutions are constructed which describe this phenomenon as a critical time is encountered, for two physically distinct cases: inviscid jets governed by the Euler equations and highly viscous jets governed by the Stokes equations. In both cases the only assumption imposed is that at the time of pinching the jet shape has a radial length scale which is smaller than the axial length scale. For the inviscid case, we show that our solution corresponds exactly to one member of the one-parameter family of solutions obtained from slender jet theories and the shape of the jet is locally concave at breakup. For highly viscous jets our theory predicts local shapes which are monotonic increasing or decreasing indicating the formation of a mother drop connected to the jet by a thin fluid tube. This qualitative behavior is in complete agreement with both direct numerical simulations and experimental observations.

  9. High-order azimuthal instabilities on a cylindrical liquid jet driven by temporal and spatial perturbations

    NASA Astrophysics Data System (ADS)

    Dressler, John L.

    1998-09-01

    A method has been developed to drive a cylindrical liquid jet unstable for deformations with axial wavelengths shorter than the circumference of the jet and azimuthal mode numbers greater than 0. The benefit of this method is that a cylindrical liquid jet can be broken into a spray with an average diameter smaller than the diameter of the initial jet. The higher-order instabilities were created by establishing initial conditions for the jet in space and time at the nozzle. An electromechanical transducer creates the applied temporal initial condition which is a sinusoidally varying velocity perturbation added to the steady velocity of the jet. The amplitude of the velocity perturbation can be as large as the jet's steady velocity and the energy in the applied velocity perturbation drives the instability. The spatial perturbation is created by placing perturbations in the circumference of the nozzle. As the velocity perturbation travels on the jet, its leading edge steepens and the trailing edge broadens in a manner analogous to the steepening of a pressure pulse in a compressible gas. If the driven velocity perturbation is sufficiently large, a shock or jump forms on the leading edge of the velocity pulse and the jet may break up into higher-order modes. A theoretical analysis of the breakup process, based on an adaptation of compressible fluid shock theory, is used to derive a fundamental lower bound on the spray's Sauter mean diameter as a function of the velocity perturbation amplitude. Techniques for approaching the theoretical minimum spray diameter by using the higher-order modes to atomize liquid jets are discussed.

  10. Liquid jet breakup and subsequent droplet dynamics under normal gravity and in microgravity conditions

    NASA Astrophysics Data System (ADS)

    Suñol, Francesc; González-Cinca, Ricard

    2015-07-01

    We present an experimental study on the characteristics of liquid jets in different configurations. We consider jets injected perpendicular to gravity, jets injected parallel to gravity, and jets injected in a microgravity environment. We study the role played by gravity in the jet breakup length and in the dynamics of the droplets generated after breakup. We analyze droplets obtained in the dripping and jetting regimes, focusing the study on their size, trajectory, oscillation, and rotation. The particularities of the considered injection configurations are analyzed. In normal gravity conditions, in the dripping and jetting regimes, the breakup length increases with the Weber number. The transition between these regimes occurs at Wecr ≈ 3.2. Droplets are notably larger in the dripping regime than in the jetting one. In the latter case, droplet mean size decreases as the liquid flow rate is increased. In microgravity conditions, droplet trajectories form a conical shape due to droplet bouncing after collision. When a collision takes place, coalescence tends to occur at low modified Weber numbers (Wem < 2) while bouncing is observed at higher values (Wem > 2). The surface of a droplet oscillates after bouncing or coalescence events, following a damped oscillator behavior. The observed oscillation frequency agrees with theoretical predictions.

  11. Production of jet fuel from coal-derived liquids

    SciTech Connect

    Furlong, M.W.; Fox, J.D.; Masin, J.G.; Soderberg, D.J.

    1988-01-01

    Amoco and Lummus Crest, under a contract with the United States Department of Energy, are evaluating the process options and economics for upgrading the naphtha, crude phenols, and tar oil by-products from the Great Plains Coal Gasification Plant to jet fuels and other salable products. Task 1 of the work, in which processes to produce each of the three jet fuels, JP-4, JP-8, and JP-8X, were designed, has been completed. The formal Task 1 report should issue next quarter. Task 2 work was initiated this quarter. In Task 2, process conditions for producing jet fuel from the Great Plains tar oil stream will be verified and samples of each of the three jet fuels will be produced. Experimental work shows that the hydrotreating conditions specified in Task 1 will not convert sufficient aromatics in the tar oil to produce jet fuel. Alternative schemes have been proposed and are being tested in the laboratories at Amoco Research Center. The simplest of these schemes, in which the heavy ends from the hydrotreater are recycled to extinction, was tested and proved infeasible. A second stage, fixed bed hydrotreater will be added to the process along with the expanded bed, first-stage hydrotreater and the hydrocracker specified in the Task 1 design. Future work will include additional experiments to specify the best process configuration and production of samples of each of the three grades of jet fuel. 6 figs., 7 tabs.

  12. Disintegration of planar liquid film impacted by two-dimensional gas jets

    NASA Astrophysics Data System (ADS)

    Mehring, C.; Sirignano, W. A.

    2003-05-01

    The distortion and break-up of a thin planar liquid film impacted by two gas jets while discharging from a twin-fluid atomizer is studied numerically. The gas momentum vector has components normal and parallel to the liquid stream. Viscosity and compressibility are neglected in both the liquid phase and the gas phase. The reduced-dimension (lubrication) approximation is employed to describe the nonlinear distortion and breakup of the thin film. The gas-phase dynamics are modelled by using a boundary-element-method formulation. For the considered parameter range and for a given energy expenditure, direct modulation of liquid-phase velocities at the nozzle exit is found to be more effective in causing film rupture than indirect modulation via adjacent impacting gas jets. In the former case, dilational film modulation results in shorter breakup lengths than sinuous modulation. On the other hand, for gas-jet modulated films, sinuous mode forcing is more effective than dilational forcing for the same energy input. Co-flowing gas streams significantly alter wavelengths and amplitudes of film disturbances generated by direct film modulation. Large ratios of gas-jet momentum to liquid-film momentum result in "immediate" film rupture in response to the dynamics of the impacting gas jets, whereas for lower ratios films disintegration occurs further downstream after continuous growth of the initial disturbances. Film distortion is characterized by the formation of fluid blobs or long band-like films depending on Weber number values and density ratio.

  13. Experimental investigation on structures and velocity of liquid jets in a supersonic crossflow

    SciTech Connect

    Wang, Zhen-guo Wu, Liyin; Li, Qinglian; Li, Chun

    2014-09-29

    Particle image velocimetry was applied in the study focusing on the structure and velocity of water jets injected into a Ma = 2.1 crossflow. The instantaneous structures of the jet, including surface waves in the near-injector region and vortices in the far-field, were visualized clearly. Spray velocity increases rapidly to 66% of the mainstream velocity in the region of x/d < 15, owing to the strong gas-liquid interaction near the orifice. By contrast, the velocity grows slowly in the far-field region, where the liquid inside the spray is accelerated mainly by the continuous driven force provided by the mainstream with the gas-liquid shear. The injection and atomization of liquid jet in a supersonic crossflow serves as a foundation of scramjet combustion process, by affecting the combustion efficiency and some other performances. With various forces acting on the liquid jet (Mashayek et al. [AIAA J. 46, 2674–2686 (2008)] and Wang et al. [AIAA J. 50, 1360–1366 (2012)]), the atomization process involves very complex flow physics. These physical processes include strong vortical structures, small-scale wave formation, stripping of small droplets from the jet surface, formations of ligaments, and droplets with a wide range of sizes.

  14. Profiles of flow discharged from vertical rotating pipes: A contrast between inviscid liquid and granular jets

    NASA Astrophysics Data System (ADS)

    Weidman, P. D.; Kubitschek, J. P.; Medina, A.

    2008-11-01

    The stability of viscous rotating liquid columns and their application to rotating viscous liquid jets aligned under gravity is reviewed. Experiments on stable viscous fluid flow discharged from rotating vertical pipes exhibit very weak contraction. We present an elementary liquid jet analysis to understand this phenomenon. Indeed, our inviscid model of a slender rotating inviscid liquid jet shows that rotation suppresses contraction. Next we study the comparable problem for granular flow. Our model for noncohesive granular flow emanating from a vertical pipe rotating about its central axis, valid for sufficiently large rotation rate, shows that the granular profiles blossom rather than contract. The profiles of both the liquid and granular jets depend on the same dimensionless parameters—an exit Froude number Fr0 and an exit swirl parameter χ0. The limitations of both models are discussed. Experimental data for granular jet profiles compare well with the collision-free granular flow model in its range of applicability. A criterion for the rotation rate at which particles adjacent to the inner wall of the rotating pipe cease to flow is also given and compared to experiment.

  15. Taking the Plunge off the Ivory Tower.

    ERIC Educational Resources Information Center

    Mauzerall, Jorgette

    1997-01-01

    Relates the experiences of a white academic teaching in a black rural state college--a plunge into the world of black experience which shocked the academic. States that everything was different--students' names, their manner of dress, their reaction to the O.J. Simpson verdict. Finds that leaving the ivory tower was not easy, but the job exceeded…

  16. Hydrocarbon group type determination in jet fuels by high performance liquid chromatography

    NASA Technical Reports Server (NTRS)

    Antoine, A. C.

    1977-01-01

    Thirty-two jet and diesel fuel samples of varying chemical composition and physical properties were prepared from oil shale and coal syncrudes. Hydrocarbon types in these samples were determined by a fluorescent indicator adsorption analysis, and the results from three laboratories are presented and compared. Two methods of rapid high performance liquid chromatography were used to analyze some of the samples, and these results are also presented and compared. Two samples of petroleum-based Jet A fuel are similarly analyzed.

  17. Liquid jet impingement normal to a disk in zero gravity. Ph.D. Thesis - Toledo Univ.

    NASA Technical Reports Server (NTRS)

    Labus, T. L.

    1976-01-01

    An experimental and analytical investigation was conducted to determine the free surface shapes of circular liquid jets impinging normal to sharp-edged disks under both normal and zero gravity conditions. An order of magnitude analysis was conducted indicating regions where viscous forces were not significant when computing free surface shapes. The demarcation between the viscous and inviscid region was found to depend upon the flow Reynolds number and the ratio between the jet and disk radius.

  18. Plunge location of sediment driven hyperpycnal river discharges considering bottom friction, lateral entrainment, and particle settling

    NASA Astrophysics Data System (ADS)

    Strom, K. B.; Bhattacharya, J.

    2012-12-01

    River discharges with very high sediment loads have the potential to develop into plunging hyperpycnal flows that transition from a river jet to a turbidity current at some location basinward of the river mouth due to the density difference between the turbid river and the receiving water body. However, even if the bulk density of the turbid river is greater than that of the receiving lake or ocean, some distance is needed for the forward inertia of the river to dissipate so that the downward gravitational pull can cause the system to collapse into a subaqueous turbidity current. This collapsing at the plunge point has been found to occur when the densimetric Froude number decreases to a value between 0.3 < Frd < 0.7 (Fang and Stefan 2000, Parker and Toniolo 2007, Dai and Garcia 2010, Lamb et al. 2010). In 2D channel flow analysis at the plunge point, this has led to the concept of a two-fold criterion for plunging. The first is simply for the need of high enough suspended sediment concentration to overcome the density difference between the river fluid and the fluid of the receiving water. The second is the need for sufficiently deep water to reduce the densimetric Froude below the critical value for plunging, which leads to dependence of plunging on the receiving water basin topography (Lamb et al. 2010). In this analysis, we expand on past work by solving a system of ODE river jet equations to account for bottom friction, lateral entrainment of ambient fluid, and particle settling between the river mouth and the plunge location. Typical entrainment and bottom friction coefficients are used and the model is tested against the laboratory density current data of Fang and Stefan (1991). A suite of conditions is solved with variable river discharge velocity, aspect ratio, suspended sediment concentration, and particle size; a range of salinity values and bottom slopes are used for the receiving water body. The plunge location is then expressed as a function of the

  19. Effect of liquid droplets on turbulence structure in a round gaseous jet

    NASA Technical Reports Server (NTRS)

    Mostafa, A. M.; Elghobashi, S. E.

    1984-01-01

    A proposed two equation turbulence model for incompressible dilute two phase flows was validated and extended for steady incompressible two phase flow including phase change. The model was tested for the flow of a turbulent axisymmetric gaseous jet laden with multisize evaporating liquid droplets. Predicted results include distributions of the mean velocity; volume fractions of different phases concentration of the evaporated material in the carrier phase; turbulence intensity and shear stress of the carrier phase; droplet diameter distribution; and the jet spreading rate. Results are analyzed based on a qualitative comparison with the corresponding single phase jet flow.

  20. Transverse liquid fuel jet breakup, burning, and ignition. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Li, Hsi-Shang

    1990-01-01

    An analytical study of the breakup, burning, and ignition of liquid fuels injected transversely into a hot air stream is conducted. The non-reacting liquid jet breakup location is determined by the local sonic point criterion. Two models, one employing analysis of an elliptical jet cross-section and the other employing a two-dimensional blunt body to represent the transverse jet, were used for sonic point calculations. An auxiliary criterion based on surface tension stability is used as a separate means of determining the breakup location. For the reacting liquid jet problem, a diffusion flame supported by a one-step chemical reaction within the gaseous boundary layer is solved along the ellipse surface in subsonic cross flow. Typical flame structures and concentration profiles were calculated for various locations along the jet cross-section as a function of upstream Mach numbers. The integration reaction rate along the jet cross-section is used to predict ignition position, which is found to be situated near the stagnation point. While a multi-step reaction is needed to represent the ignition process more accurately, the present calculation does yield reasonable predictions concerning ignition along a curved surface.

  1. Numerical simulation of liquid-layer breakup on a moving wall due to an impinging jet

    NASA Astrophysics Data System (ADS)

    Yu, Taejong; Moon, Hojoon; You, Donghyun; Kim, Dokyun; Ovsyannikov, Andrey

    2014-11-01

    Jet wiping, which is a hydrodynamic method for controlling the liquid film thickness in coating processes, is constrained by a rather violent film instability called splashing. The instability is characterized by the ejection of droplets from the runback flow and results in an explosion of the film. The splashing phenomenon degrades the final coating quality. In the present research, a volume-of-fluid (VOF)-based method, which is developed at Cascade Technologies, is employed to simulate the air-liquid multiphase flow dynamics. The present numerical method is based on an unstructured-grid unsplit geometric VOF scheme and guarantees strict conservation of mass of two-phase flow, The simulation results are compared with experimental measurements such as the liquid-film thickness before and after the jet wiping, wall pressure and shear stress distributions. The trajectories of liquid droplets due to the fluid motion entrained by the gas-jet operation, are also qualitatively compared with experimental visualization. Physical phenomena observed during the liquid-layer breakup due to an impinging jet is characterized in order to develop ideas for controlling the liquid-layer instability and resulting splash generation and propagation. Supported by the Grant NRF-2012R1A1A2003699, the Brain Korea 21+ program, POSCO, and 2014 CTR Summer Program.

  2. Absolute And Convective Instability and Splitting of a Liquid Jet at Microgravity

    NASA Technical Reports Server (NTRS)

    Lin, S. P.

    2001-01-01

    The objective is to establish a definitive role of the capillary, viscous, and inertial forces at a liquid-gas interface in the absence of gravity by using the fluid dynamics problem of the stability of a liquid jet as a vehicle. The objective is achieved by reexamining known theories and new theories that can be verified completely only in microgravity. The experiments performed in the microgravity facility at NASA Glenn Research Center enable the verification of the theory with experimental data. Of particular interest are (1) to capture for the first time the image of absolute instability, (2) to elucidate the fundamental difference in the physical mechanism of the drop and spray formation from a liquid jet, and (3) to find the origin of the newly discovered phenomenon of jet splitting on earth and in space.

  3. Theoretical modeling of optimal focusing conditions using laser-induced breakdown spectroscopy in liquid jets.

    PubMed

    Yaroshchyk, Pavel; Morrison, Richard J S; Body, Doug; Chadwick, Bruce L

    2004-11-01

    Optimal conditions are determined for laser-induced breakdown spectroscopy in liquid jets by investigating laser de-focusing and laser energy variation in aqueous liquid jets containing dilute levels of calcium chloride. It has been found that the atomic emission shows a strong correlation with both laser pulse energy and focal position. The data cannot be rationalized on the basis of electron density or ionization temperature changes alone, but rather it requires the additional consideration of the volume of the liquid sample interacting with the laser and that portion of the volume which is above the threshold energy for plasma formation. A moving breakdown model has been applied to the plasma formation in the jet to calculate the amount of sample ablated with sufficient energy for plasma formation, which models well the observed results and allows prediction of optimal focusing conditions for a given laser energy. PMID:18070410

  4. Method for analyzing the gas jet impinging on a liquid surface

    NASA Astrophysics Data System (ADS)

    Mordasov, M. M.; Savenkov, A. P.; Chechetov, K. E.

    2016-05-01

    The impingement of a gas jet on a liquid surface in the stable-state regime is analyzed theoretically. We consider the case of the perpendicular jet action. It is found that for describing analytically the processes occurring in this case, it is necessary to employ the balance equation for forces at the interface and not the balance equation for pressures at the lowest point of cavity, which was used in most available publications. Recommendations for experimental studies of a gas jet impinging on a liquid surface are formulated. We report on the results of experiments confirming the correctness of our theoretical analysis and making it possible to determine the empirical value of the shape factor. The experiments were carried out with air and epoxy resin. The cavity formed on the liquid surface had radius R 0 = 1-8 mm and depth h = 0.2-12.5 mm.

  5. Deformation and dewetting of thin liquid films induced by moving gas jets.

    PubMed

    Berendsen, Christian W J; Zeegers, Jos C H; Darhuber, Anton A

    2013-10-01

    We study the deformation of thin liquid films subjected to impinging air-jets that are moving with respect to the substrate. The height profile and shape of the deformed liquid film is evaluated experimentally and numerically for different jet Reynolds numbers and translation speeds, for different liquids and substrate materials. Experiments and numerical results are in good agreement. On partially wetting substrates film rupture occurs. We imaged the appearance of dry spots and emergence of droplet patterns by high-speed, dual-wavelength interference microscopy. We systematically evaluated the resulting average droplet size and droplet density as a function of the experimental conditions. We show that within experimental accuracy the distribution of dry spots is dependent only on the residual film thickness and is not directly influenced by the shear stress and pressure gradients of the air-jet, nor by the speed of the substrate. PMID:23866198

  6. X-ray grating interferometry with a liquid-metal-jet source

    SciTech Connect

    Thüring, T.; Rutishauser, S.; Stampanoni, M.; Zhou, T.; Lundström, U.; Burvall, A.; Hertz, H. M.; David, C.

    2013-08-26

    A liquid-metal-jet X-ray tube is used in an X-ray phase-contrast microscope based on a Talbot type grating interferometer. With a focal spot size in the range of a few microns and a photon flux of ∼10{sup 12} photons/s×sr, the brightness of such a source is approximately one order of magnitude higher than for a conventional microfocus source. For comparison, a standard microfocus source was used with the same grating interferometer, showing significantly increased visibility for the liquid-metal-jet arrangement. Together with the increased flux, this results in improved signal-to-noise ratio.

  7. Visualization of high speed liquid jet impaction on a moving surface.

    PubMed

    Guo, Yuchen; Green, Sheldon

    2015-01-01

    Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing. PMID:25938331

  8. On the Unsteady Breakup of a Liquid Jet by a Coaxial Gas Stream

    NASA Astrophysics Data System (ADS)

    Varga, Christopher M.; Lasheras, Juan; Hopfinger, Emil

    2000-11-01

    The breakup and atomization of a liquid jet by a high-momentum coaxial gas stream is investigated experimentally for unsteady flow of the central liquid. The unsteady flow is characterized by the impulsive start-up and stopping of the liquid jet by means of a square wave function. Phase-Doppler particle sizing methods and laser attenuation measurements are employed to characterize the flow field during these transient periods, with conditional measurements made on the phase of the injection pulse. Spray properties such as the liquid intact length, the critical turbulent breakup distance, droplet size distributions, and the concentration field are measured. Physical models are considered for the dependence of these quantities on various flow properties including the gas-to-liquid dynamic pressure ratio, the turbulent dissipation rate, the mass flux ratio, and nozzle dimensions. In all the cases investigated here, the atomization regime based on the aerodynamic Weber number and the liquid jet Reynolds number is characterized by 'fibre-type' breakup of the liquid.

  9. Analysis of Column Instability Modes in Liquid Jet in Crossflow Atomization

    NASA Astrophysics Data System (ADS)

    Ghods, Sina; Arienti, Marco; Soteriou, Marios; Herrmann, Marcus

    2010-11-01

    Atomizing liquids by injecting them into crossflows is a common approach to generate fuel sprays in gas turbines and augmentors. The mechanisms by which the liquid jet initially breaks up, however, are not well understood. To analyze the instability mechanism of the liquid column, we perform proper orthogonal decomposition of side view images extracted from detailed simulations of the near injector primary atomization region. This analysis shows a single dominant wavelength with the associated interface corrugation traveling downstream with the jet. Using consistent temporal averaging of the simulation data we extract mean interface geometries and boundary layer velocity profiles. These are used to calculate the most unstable wavelength of the shear layer instability following the procedure of Boeck & Zaleski (2005). The theoretical wavelengths are comparable to those extracted from the simulation data. In addition to shear layer instability we analyze Rayleigh-Taylor as a potential instability mechanism of the liquid column.

  10. Experimental investigation of the breakup of a round liquid jet in a shock-induced crossflow

    NASA Astrophysics Data System (ADS)

    Olles, Joseph; Guildenbecher, Daniel; Wagner, Justin; Demauro, Edward; Farias, Paul; Grasser, Thomas; Sojka, Paul

    2015-11-01

    The breakup of a round water jet due to a step change in the convective air velocity following a 1D air-shock was experimentally investigated. Variations of this experiment have been conducted in the past, however here quantitative results on the breakup sizes and trajectories are shown. A shock tube was utilized to create the jet breakup, and the primary shape of the liquid and secondary droplet sizes were recorded optically. Through the use of digital in-line holography (DIH), the sizes, 3D position, and 3C velocities of secondary droplets were measured at kHz rates. Care was taken to ensure that the jet was kept round throughout the shock tube test section (absent of Plateau-Rayleigh instability). While the liquid jet geometry and velocity was kept constant, various gas-phase velocities allowed for the investigation of multiple breakup morphologies, as a function of the crossflow Weber number. The typical breakup regimes are seen; bag, multimode, and sheet-thinning. With high temporal and spatial resolution, interfacial and liquid column instabilities are seen in the jet breakup.

  11. Hydrodynamic characteristics and geometric properties of plunging and spilling breakers over impermeable slopes

    NASA Astrophysics Data System (ADS)

    Alagan Chella, Mayilvahanan; Bihs, Hans; Myrhaug, Dag; Muskulus, Michael

    2016-07-01

    The two-phase flow CFD model REEF3D has been used for modeling waves breaking over a sloping seabed for a spilling and a plunging breaker. This model is based on Reynolds-averaged Navier-Stokes (RANS) equations with the level set method (LSM) for the free surface and k-ω model for turbulence. First, the characteristics and geometric properties of plunging breaking waves with different offshore wave steepnesses over slopes are examined and discussed. The study further explores the hydrodynamic characteristics of spilling and plunging breakers in terms of the wave height evolution and attenuation, horizontal and vertical velocity, free surface profile evolution, and the geometric properties during the development of the breaking process. The numerical results show a good agreement with experimental data in terms of free surface elevation, horizontal and vertical velocity, wave envelope and turbulent intensity for the spilling and plunging breakers. Results of numerical simulations describing the physical flow characteristics such as the formation of the forward overturning water jet, air pocket, splash-up, and the secondary wave during the breaking process are presented for both cases. For both cases, the physical flow process is found to have similar flow features, but the breaking process occurs at significantly different scales.

  12. Application of underwater shock wave and laser-induced liquid jet to neurosurgery

    NASA Astrophysics Data System (ADS)

    Tominaga, T.; Nakagawa, A.; Hirano, T.; Sato, J.; Kato, K.; Hosseini, S. H. R.; Takayama, K.

    2006-03-01

    Paper deals with applications of underwater shock waves to medicine. A historical development of underwater shock wave generation by using pulsed Ho:YAG laser beam irradiation in water is briefly described and an overview is given regarding potential applications of shock waves to neuro-surgery. The laser beam irradiation in a liquid-filled catheter produces water vapor bubble and shock waves intermittently produces micro-liquid jets in a controlled fashion from the exit of the catheter. Correlations between shock dynamics and bubble dynamics are emphasized. To optimize the jet motion, results of basic parametric studies are briefly presented. The liquid jet discharged from the catheter exit has an impulse high enough to clearly exhibit effectiveness for various medical purposes. In liquid jets we observed reasonably strong shock waves and hence invented a compact shock generator aiming to apply to microsurgery. We applied it to a rat's bone window and developed an effective method of brain protection against shock loading. The insertion of Gore-Tex® sheet is found to attenuate shock waves drastically even for very short stand off distance and its physical mechanism is clarified. The laser-induced liquid jet (LILJ) is successfully applied to soft tissue dissection. Animal experiments were performed and results of histological observations are presented in details. Results of animal experiments revealed that LILJ can sharply dissect soft tissue with a minimum amount of liquid consumption, while blood vessels larger than 0.2 mm in diameter are preserved. Shock waves and LILJ have a potential to be indispensable tools in neuro-surgery.

  13. Production of jet fuels from coal derived liquids

    SciTech Connect

    Furlong, M.; Fox, J.; Masin, J.

    1989-06-01

    Amoco Oil Company has conducted bench- and pilot plant-scale experiments to produce jet fuels from the tar oil from the Great Plains Coal Gasification Plant in Beulah, North Dakota. Experiments show that the hydroprocessing conditions recommended in Task 1 are not severe enough to saturate the aromatics in the tar oil to meet jet fuel specifications. Alternatives were investigated. Jet fuel specifications can be achieved when the tar oil is: hydrotreated in an expanded-bed hydrotreater to lower aromatics and heteroatom content; the effluent is then hydrotreated in a second, fixed bed hydrotreater; and, finally, the 550{degree}F boiling fraction from the two hydrotreaters is hydrocracked to extinction. The process was verified by pilot-plant production of 2 barrels of JP-8 turbine fuel, which met all but the flash point specification for JP-8. In addition, small samples of JP-4, JP-8, and high-density fuel were produced as a part of Task 2. 13 figs., 21 tabs.

  14. A 24 keV liquid-metal-jet x-ray source for biomedical applications

    SciTech Connect

    Larsson, D. H.; Takman, P. A. C.; Lundstroem, U.; Burvall, A.; Hertz, H. M.

    2011-12-15

    We present a high-brightness 24-keV electron-impact microfocus x-ray source based on continuous operation of a heated liquid-indium/gallium-jet anode. The 30-70 W electron beam is magnetically focused onto the jet, producing a circular 7-13 {mu}m full width half maximum x-ray spot. The measured spectral brightness at the 24.2 keV In K{sub {alpha}} line is 3 x 10{sup 9} photons/(s x mm{sup 2}x mrad{sup 2}x 0.1% BW) at 30 W electron-beam power. The high photon energy compared to existing liquid-metal-jet sources increases the penetration depth and allows imaging of thicker samples. The applicability of the source in the biomedical field is demonstrated by high-resolution imaging of a mammography phantom and a phase-contrast angiography phantom.

  15. A two-phase model for subcooled and superheated liquid jets

    SciTech Connect

    Muralidhar, R.; Jersey, G.R.; Krambeck, F.J.; Sundaresan, S.

    1995-12-31

    This paper describes a two-phase jet model for predicting the liquid rainout (capture) and composition of subcooled and superheated HF/additive pressurized liquid releases. The parent droplets of the release mixture constitute the fist phase. The second phase can in general be a vapor-liquid fog. The drops are not in equilibrium with the fog phase with which they exchange mass and energy. The fog at any location is assumed to be in local equilibrium. Correlations are developed for predicting the initial drop size for hydrodynamic breakup of jets. Applications are discussed in this paper for HF/additive mixtures. The fog phase calculations account for HF oligomerization and HF-water complex formation in the vapor phase and equilibrium between the liquid and vapor in the fog. The model incorporates jet trajectory calculations and hence can predict the amount of liquid rained out (liquid capture) and the capture distance. The HF captures predicted by the model for various release conditions are in agreement with small and large scale release experiments.

  16. A new technology for revascularization of cerebral embolism using liquid jet impact

    NASA Astrophysics Data System (ADS)

    Kodama, Tetsuya; Takayama, Kazuyoshi; Uenohara, Hiroshi

    1997-12-01

    Revascularization time is the dominant factor in the treatment of acute cerebral embolism. In this paper we describe a rapid revascularization therapy using liquid jets generated by the interaction of gas bubbles with shock waves, which impact on the thrombi. The interaction of a shock wave with a gas bubble attached to an artificial thrombus which was inserted into a tube model of a cerebral artery was investigated. The shock wave was generated by detonating a microexplosive pellet. The overpressure of the shock wave was (n = 7) and (n = 3). The initial air bubble radii were varied from 0.87 mm to 2.18 mm. The subsequent collapse of the bubble was photographed using a high-speed framing camera, and the liquid jet penetrating into the artificial thrombus was visualized using x-ray photography. The penetration depth of the liquid jet increased with increasing bubble size. There was an optimal separation distance between the bubble and the shock wave source to obtain the maximum penetration depth. Liquid jets have the potential to penetrate through thrombi in as little as a few microseconds, and with very efficient ablation.

  17. On the transfer of energy to an unstable liquid jet in a coflowing compressible airstream

    NASA Technical Reports Server (NTRS)

    Li, Hsi-Shang; Kelly, Robert E.

    1993-01-01

    The transfer of energy from a compressible airstream to a coflowing unstable liquid jet via the pressure perturbation at the interface is studied as the Mach number varies continuously from subsonic to supersonic values. The 'lift' component of the pressure perturbation has been demonstrated to predominate up to slightly supersonic free-stream Mach numbers, after which the 'drag' component predominates.

  18. First Results of the Testing of the Liquid Gallium Jet Limiter Concept for ISTTOK

    SciTech Connect

    Gomes, R. B.; Fernandes, H.; Silva, C.; Borba, D.; Carvalho, B.; Varandas, C.

    2006-12-04

    The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages to the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaustion from fusion devices. Presently the most promising materials are Lithium and Gallium. ISTTOK, a small size tokamak, will be used to test the behavior of a liquid Gallium jet in the vacuum chamber and its influence on the plasma. This paper presents a description of the conceived setup as well as experimental results. The liquid Gallium jet is generated by hydrostatic pressure and injected in a radial position close to a moveable stainless steel limiter. Both the jet and the limiter positions are variable allowing for a controlled exposure of the liquid Gallium to the edge plasma. The main components of the Gallium loop are a MHD pump, the liquid metal injector and a filtering system. The MHD pump is of the induction type, based on rotating permanent magnets. The injector is build from a stainless steel pipe ended by a shaping nozzle. A setup has been developed to introduce oxide-free Gallium inside the loop's main supply tank. Raw liquid metal is placed inside a chamber heated and degassed under high vacuum while clean Gallium is extracted from the main body of the liquefied metal. Prior to installation on the tokamak, the experimental rig has been implemented using a Pyrex tube as test chamber to investigate the stability of the Gallium jet and its break-up length for several nozzle sizes. Results are presented in this paper. This rig was also useful to assess the behavior of the overall implemented apparatus.

  19. Traction Drive Inverter Cooling with Submerged Liquid Jet Impingement on Microfinned Enhanced Surfaces (Presentation)

    SciTech Connect

    Waye, S.; Narumanchi, S.; Moreno, G.

    2014-09-01

    Jet impingement is one means to improve thermal management for power electronics in electric-drive traction vehicles. Jet impingement on microfin-enhanced surfaces further augments heat transfer and thermal performance. A channel flow heat exchanger from a commercial inverter was characterized as a baseline system for comparison with two new prototype designs using liquid jet impingement on plain and microfinned enhanced surfaces. The submerged jets can target areas with the highest heat flux to provide local cooling, such as areas under insulated-gate bipolar transistors and diode devices. Low power experiments, where four diodes were powered, dissipated 105 W of heat and were used to validate computational fluid dynamics modeling of the baseline and prototype designs. Experiments and modeling used typical automotive flow rates using water-ethylene glycol as a coolant (50%-50% by volume). The computational fluid dynamics model was used to predict full inverter power heat dissipation. The channel flow and jet impingement configurations were tested at full inverter power of 40 to 100 kW (output power) on a dynamometer, translating to an approximate heat dissipation of 1 to 2 kW. With jet impingement, the cold plate material is not critical for the thermal pathway. A high-temperature plastic was used that could eventually be injection molded or formed, with the jets formed from a basic aluminum plate with orifices acting as nozzles. Long-term reliability of the jet nozzles and impingement on enhanced surfaces was examined. For jet impingement on microfinned surfaces, thermal performance increased 17%. Along with a weight reduction of approximately 3 kg, the specific power (kW/kg) increased by 36%, with an increase in power density (kW/L) of 12% compared with the baseline channel flow configuration.

  20. Experimental investigation of inclined liquid water jet flow onto vertically located superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Kibar, Ali; Karabay, Hasan; Yiğit, K. Süleyman; Ucar, Ikrime O.; Erbil, H. Yıldırım

    2010-11-01

    In this study, the behaviour of an inclined water jet, which is impinged onto hydrophobic and superhydrophobic surfaces, has been investigated experimentally. Water jet was impinged with different inclination angles (15°-45°) onto five different hydrophobic surfaces made of rough polymer, which were held vertically. The water contact angles on these surfaces were measured as 102°, 112°, 123°, 145° and 167° showing that the last surface was superhydrophobic. Two different nozzles with 1.75 and 4 mm in diameters were used to create the water jet. Water jet velocity was within the range of 0.5-5 m/s, thus the Weber number varied from 5 to 650 and Reynolds number from 500 to 8,000 during the experiments. Hydrophobic surfaces reflected the liquid jet depending on the surface contact angle, jet inclination angle and the Weber number. The variation of the reflection angle with the Weber number showed a maximum value for a constant jet angle. The maximum value of the reflection angle was nearly equal to half of the jet angle. It was determined that the viscous drag decreases as the contact angle of the hydrophobic surface increases. The drag force on the wall is reduced dramatically with superhydrophobic surfaces. The amount of reduction of the average shear stress on the wall was about 40%, when the contact angle of the surface was increased from 145° to 167°. The area of the spreading water layer decreased as the contact angle of the surface increased and as the jet inclination angle, Weber number and Reynolds number decreased.

  1. Production of jet fuels from coal-derived liquids

    SciTech Connect

    Furlong, M.; Fox, J.; Masin, J. . Research and Development Dept.); Stahlnecker, E.; Schreiber, G.; Klein, R. )

    1989-12-01

    A preliminary design for the production of JP-8 jet fuel and other salable products from the Great Plains by-products is given. The design incorporates experimental results from Tasks 2 and 3 with the scoping design from Task 1. The experimental results demonstrated the need for more severe hydrotreating conditions to convert the tar oil to jet fuel than was estimated in Task 1. As a result, capital costs for the revised design are significantly higher and the plant is less profitable than estimated in the Task 1 work. The increase in capital costs is offset somewhat by a higher phenol value in the current market. Refined estimates for the cost of an aromatics recovery unit preclude its economical construction in the new estimate, consequently the revised product slate includes no BTX. Recommendations are given for a 10,000 barrel production run. No commercial domestic facility exists which can provide suitable expanded-bed hydrotreating facilities for a production run of this size. However, an alternative approach using hot filtration and dilute fixed-bed hydrocracking followed by product fractionation and extinctive hydrotreating of the heavy products is recommended. Commercial domestic facilities which might reasonably accommodate this scheme are listed. 6 refs., 8 figs., 11 tabs.

  2. Droplet impact on deep liquid pools: Rayleigh jet to formation of secondary droplets.

    PubMed

    Castillo-Orozco, Eduardo; Davanlou, Ashkan; Choudhury, Pretam K; Kumar, Ranganathan

    2015-11-01

    The impact of droplets on a deep pool has applications in cleaning up oil spills, spray cooling, painting, inkjet printing, and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension, and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to Rayleigh jet breakup and number of daughter drops formed after its pinch-off. In this article, through systematic experiments we investigate the droplet impact phenomena by varying viscosity and surface tension of liquids as well as impact speeds. Further, using numerical simulations, we show that Rayleigh-Plateau instability is influenced by these parameters, and capillary time scale is the appropriate scale to normalize the breakup time. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested. Interestingly, crown splash is observed to occur at all Ohnesorge numbers; however, at high Oh, a large portion of kinetic energy is dissipated, and thus the Rayleigh jet is suppressed regardless of high impact velocity. The normalized required time for the Rayleigh jet to reach its peak varies linearly with the critical height of the jet. PMID:26651794

  3. Droplet impact on deep liquid pools: Rayleigh jet to formation of secondary droplets

    NASA Astrophysics Data System (ADS)

    Castillo-Orozco, Eduardo; Davanlou, Ashkan; Choudhury, Pretam K.; Kumar, Ranganathan

    2015-11-01

    The impact of droplets on a deep pool has applications in cleaning up oil spills, spray cooling, painting, inkjet printing, and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension, and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to Rayleigh jet breakup and number of daughter drops formed after its pinch-off. In this article, through systematic experiments we investigate the droplet impact phenomena by varying viscosity and surface tension of liquids as well as impact speeds. Further, using numerical simulations, we show that Rayleigh-Plateau instability is influenced by these parameters, and capillary time scale is the appropriate scale to normalize the breakup time. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested. Interestingly, crown splash is observed to occur at all Ohnesorge numbers; however, at high Oh, a large portion of kinetic energy is dissipated, and thus the Rayleigh jet is suppressed regardless of high impact velocity. The normalized required time for the Rayleigh jet to reach its peak varies linearly with the critical height of the jet.

  4. Intensification of liquid jet atomization through injection into the exit channel of the atomizer

    NASA Astrophysics Data System (ADS)

    Gel'Fand, B. E.; Dranovskii, M. L.; Novikov, A. G.; Pikalov, V. P.

    The injection of a gas jet into the liquid flow at the exit of an atomizer nozzle, directly before the liquid is discharged into the ambient atmosphere, was investigated experimentally as a possible method of improving the quality of atomization. The atomizer used in the experiments had transparent side walls and a nozzle of rectangular (2 x 4 mm) cross section; the relative length of the nozzle was 1.5-1.6. It is shown that gas injection not only improves the quality of atomization but also makes it possible to lower the liquid supply pressure and to increase the atomizer nozzle diameter.

  5. Heat transfer from a liquid bath due to an impinging gas jet: A numerical study

    SciTech Connect

    Qian, F.; Farouk, B.; Mutharasan, R.

    1995-12-31

    An impinging gasjet on a liquid surface is found in many industrial processes such as electric arc furnace steel-making and welding. Fundamental understanding of the interaction of a gas or plasmajet impinging on a liquid pool can provide important insights into process behavior resulting in improved efficiency. A numerical model is developed for solving both the impinging gas jet and the liquid pool temperature and flow fields along with the deformed interface shape for the above processing operation. Using curvilinear coordinates, the Navier-Stokes equations of each phase are solved separately and then coupled via continuity of static pressure, shear stress, temperature and heat flux at the interface.

  6. Determination of Cavity Dimensions Induced by Impingement of Gas Jets onto a Liquid Bath

    NASA Astrophysics Data System (ADS)

    Li, Mingming; Li, Qiang; Kuang, Shibo; Zou, Zongshu

    2016-02-01

    This paper presents an experimental and theoretical study on the cavity profile induced by the impingement of top-blown multiple gas jets onto a water or oil/water bath. The depth and diameter of the cavity were measured with respect to the lance height, gas flow rate, jets inclination angle, and oil volume. The experimental results show that the cavity depth increases with the increase of gas flow rate or oil thickness but the decrease of lance height or jets inclination angle. The cavity diameter is much less affected by gas flow rate compared to other variables. Then, the importance of the surface tension in the modeling of the cavity was theoretically identified. It was found that in the cratering process, the effect of the liquid surface tension on the cavity depth could be remarkably significant for a basic oxygen furnace (BOF) cold model but negligible for a real BOF steelmaking system. An improved theoretical model was hence proposed and validated using the experimental data obtained from both the single- or two-layer liquid baths. The new model includes not only the explicit consideration of the liquid surface tension but also that of the energy utilization efficiency of the jets impinging kinetic energy contributed to the cratering process.

  7. Transferring jet engine diagnostic and control technology to liquid propellant rocket engines

    SciTech Connect

    Alcock, J.F.; Hagar, S.K.

    1989-01-01

    This paper presents the methodology for developing a diagnostic and control system for a current, operational jet engine. A description is given of each development stage, the system components and the technologies which could be transferred to liquid propellant rocket engines. Finally, the operational impact is described in terms of cost and maintenance based on actual jet engine experience. Efforts are continuing to develop new diagnostic techniques under IR D for application on the advanced technical fighter. Already improved techniques and application methods are becoming available. This technology is being evaluated and may also be transferred to rocket engine diagnostic and control system development.

  8. Boiling-up of liquid nitrogen jet in water

    NASA Astrophysics Data System (ADS)

    Nakoryakov, V. E.; Tsoi, A. N.; Mezentsev, I. V.; Meleshkin, A. V.

    2014-06-01

    The hydrodynamic processes occurring at injection of cryogenic liquid into water pool were studied experimentally. Processes accompanying the phase transitions were registered. Data testify the developing pressure burst with an amplitude sufficient for possible formation of gas hydrates when methane is injected as a cryogenic fluid.

  9. Influence of Turbulence on the Restraint of Liquid Jets by Surface Tension in Microgravity Investigated

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2002-01-01

    Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, surface tension forces must contain jets. To model this phenomenon, a numerical method that tracks the fluid motion and the surface tension forces is required. Jacqmin has developed a phase model that converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly away. Previous attempts at this formulation were criticized for smearing the interface. This can be overcome by sharpening the phase function, double gridding the fluid function, and using a higher order solution for the fluid function. The solution of this equation can be rewritten as two coupled Poisson equations that also include the velocity. After the code was implemented in axisymmetric form and verified by several test cases at the NASA Glenn Research Center, the drop tower runs of Aydelott were modeled. Work last year with a laminar model was found to overpredict Aydelott's results, except at the lowest Reynolds number conditions of 400. This year, a simple turbulence model was implemented by adding a turbulent viscosity based on the mixing-length hypothesis and empirical measurements of previous works. Predictions made after this change was implemented have been much closer to experimentally observed flow patterns and geyser heights. Two model runs is shown. The first, without any turbulence correction

  10. Self-organization of jets in electrospinning from free liquid surface: A generalized approach

    NASA Astrophysics Data System (ADS)

    Lukas, David; Sarkar, Arindam; Pokorny, Pavel

    2008-04-01

    Electrospinning has enabled creation of excellent materials for a great number of applications. Previously, it was based on less productive capillary spinners. The present study is based on recent efforts to elevate electrospinning technology to an industrial level by simultaneously provoking innumerable polymeric jets from a sufficiently large liquid surface to increase productivity. Particularly, it deals with electrospinning from free surface of conductive liquids and validates a formulated hypothesis that explains self-organization of jets on one-dimensional free liquid surfaces in terms of electrohydrodynamic instability of surface waves. Here, it is shown how the hypothesis, based on a profound analysis of a dispersion law, explains that above a certain critical value of applied electric field intensity/field strength the system starts to be self-organized in mesocopic scale due to the mechanism of the "fastest forming instability." The mechanism plays a key role in selecting a particular wave with a characteristic wavelength whose amplitude boundlessly grows faster than the others. The fastest growing stationary wave, according to the hypothesis, marks the onset of electrospinning from a free liquid surface with its jets originating from the wave crests. Singularity of this approach lies in predicting critical values of the phenomenon, viz., critical field strength and corresponding critical interjet distance. The critical field strength, will, thereafter, be used in defining a unique dimensionless electrospinning number. It will, subsequently, be shown how the critical interjet distance, i.e., the maximal distance between the neighboring jets, simply depends on the capillary length. The capillary length represents a latent characteristic spatial scale of the system. The theory also predicts interjet distance for field strengths above the critical value. The said prediction is universally applicable for all conductive liquids if it is expressed in terms of

  11. Liquid jet breakup and atomization in rocket chambers under dense spray conditions

    NASA Technical Reports Server (NTRS)

    Kuo, Kenneth K.; Cheung, Fan-Bill; Woodward, Roger D.; Garner, Kenneth N.

    1991-01-01

    Two advanced diagnostic techniques were established and employed in this project. The first technique involves the use of a real-time x ray radiography system along with a high-speed CCD Xybion camera and an advanced digital image processor to investigate the breakup processes of the liquid core. The focus of this part of the project is to determine the inner structure of the liquid jet and via thin sheets of laser light, with the scatters light being photographed by a Xybion electronic camera synchronized to the laser pulse. This technique, which is capable of recording the breakup event occurring within 25 nano-seconds, enables us to freeze the motions of the jet and liquid droplets. The focus of this part of the project is to determine the outer structure of the liquid jet and to discover the configuration of the surface waves, the spray pattern, and the droplet size distribution in the non-dilute region. Results obtained by these two advanced diagnostic techniques will provide the much needed database for model development and accurate prediction of engine performance. The present work also represents a breakthrough in the area of advanced diagnostics of dense sprays.

  12. Direct numerical simulation of ignition in turbulent n-heptane liquid-fuel spray jets

    SciTech Connect

    Wang, Y.; Rutland, C.J.

    2007-06-15

    Direct numerical simulation was used for fundamental studies of the ignition of turbulent n-heptane liquid-fuel spray jets. A chemistry mechanism with 33 species and 64 reactions was adopted to describe the chemical reactions. The Eulerian method is employed to solve the carrier-gas flow field and the Lagrangian method is used to track the liquid-fuel droplets. Two-way coupling interaction is considered through the exchange of mass, momentum, and energy between the carrier-gas fluid and the liquid-fuel spray. The initial carrier-gas temperature was 1500 K. Six cases were simulated with different droplet radii (from 10 to 30 {mu}m) and two initial velocities (100 and 150 m/s). From the simulations, it was found that evaporative cooling and turbulence mixing play important roles in the ignition of liquid-fuel spray jets. Ignition first occurs at the edges of the jets where the fuel mixture is lean, and the scalar dissipation rate and the vorticity magnitude are very low. For smaller droplets, ignition occurs later than for larger droplets due to increased evaporative cooling. Higher initial droplet velocity enhances turbulence mixing and evaporative cooling. For smaller droplets, higher initial droplet velocity causes the ignition to occur earlier, whereas for larger droplets, higher initial droplet velocity delays the ignition time. (author)

  13. Vehicle-scale investigation of a fluorine jet-pump liquid hydrogen tank pressurization system

    NASA Technical Reports Server (NTRS)

    Cady, E. C.; Kendle, D. W.

    1972-01-01

    A comprehensive analytical and experimental program was performed to evaluate the performance of a fluorine-hydrogen jet-pump injector for main tank injection (MTI) pressurization of a liquid hydrogen (LH2) tank. The injector performance during pressurization and LH2 expulsion was determined by a series of seven tests of a full-scale injector and MTI pressure control system in a 28.3 cu m (1000 cu ft) flight-weight LH2 tank. Although the injector did not effectively jet-pump LH2 continuously, it showed improved pressurization performance compared to straight-pipe injectors tested under the same conditions in a previous program. The MTI computer code was modified to allow performance prediction for the jet-pump injector.

  14. Plunging ranula: an unusual multilocular presentation.

    PubMed

    Mabongo, M; Buch, B; Ngwenya, S P

    2014-10-01

    A 32-year-old male patient who was HIV positive presented at the Wits Oral Health Centre complaining of a large swelling of the left submandibular region of three years' duration. The swelling was nontender, soft and doughy on palpation and appeared to be crossing the midline. Bilateral submandibular and submental lymphadenopathy was present. Intraorally the lesion caused considerable elevation of the floor of the mouth and impaired the flow of saliva. Fluid from the lesion was aspirated and the patient sent for MRI examination. These images revealed a multilocular cystic lesion causing disruption of the mylohyold muscle. The aspirate consisted of a thick, bloody fluid which tested positive for salivary amylase. A provisional diagnosis of plunging ranula was made. The multilocular nature of the lesion seen on MRI prompted a more extensive surgical approach in order to prevent recurrence. Consequently the sublingual gland was removed via an intraoral approach while the multilocular cyst was dissected by means of a submandibular approach in order to effect complete removal. Microscopic examination of the submitted specimen confirmed the clinical diagnosis of a plunging ranula. PMID:26571925

  15. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    McClure, John C.

    2005-01-01

    The many advantages of Friction Stir Welding have led to a relatively rapid acceptance in the often conservative welding community. Because the process is so different from traditional fusion welding, with which most investigators are most familiar, there remain many aspects of FSW for which there is no clear consensus. For example, the well known onion rings seen in transverse sections have been variously interpreted as grain size variations, variation in density of second phase particles and parts of the carousel of material rotating with the pin that have been shed from the carousel. Using Orientation Imaging Microscopy, Schneider has recently noted that the onion rings have a different orientation (and hence etch differently) than the surrounding material, and this orientation is consistent with slip plane orientations at the edge of the carousel. Likewise, the forces and torque exerted by the FSW tool on the work piece largely remain unaccounted for. Although these forces are routinely measured by investigators with commercial instrumented welders, they are rarely reported or even qualitatively analyzed. This paper will introduce a model based on a carousel or disk of material that rotates with the tool to estimate the torque and plunge force required to plunge a tool into the work piece. A stationary tool is modeled rather than the moving tool because effects such as thermal transients and metallurgical changes in the sample (primarily aging in aluminum) can be more easily accounted for. It is believed, however, that with some modifications the model should be applicable to a moving tool also.

  16. Dynamics of Pinch-Off in Immiscible Liquid/Liquid Jets

    NASA Astrophysics Data System (ADS)

    Longmire, E. K.; Webster, D. R.; Lowengrub, J. S.

    1997-11-01

    The behavior of glycerine/water jets flowing into a nearly immiscible ambient of Dow Corning 200 fluid is investigated using laser induced fluorescence flow visualization and particle image velocimetry. Clear images are obtained by matching the index of refraction in the glycerine/water solution with the index of refraction in the surrounding Dow Corning fluid. Jet Reynolds numbers are on the order of 100. The pinch-off of the jet column into droplets can be made repeatable by periodic forcing, and several pinch-off modes are examined. These modes are produced by varying the forcing frequency and amplitude, fluid viscosity ratio, and jet Reynolds number. The details of the pinch-off, including local variations in concentration near the transition location and the associated velocity fields will be discussed. The experimental results will be compared with numerical simulations that allow limited chemical mixing across the finite-thickness interface.

  17. Atomization of a small-diameter liquid jet by a high-speed gas stream

    NASA Astrophysics Data System (ADS)

    Varga, Christopher Michael

    The situation of a small-diameter liquid jet exposed to a large-diameter high-speed gas jet is investigated experimentally. Flow visualization and particle-sizing techniques are employed to examine both the initial breakup process and subsequent secondary atomization of the liquid. It is shown that nearly all of the breakup takes place in the near-field and that the bulk of the atomization is completed within the potential cone of the gas jet. The resultant drop size depends primarily on the gas velocity and to a weaker extent on the liquid mass flux. It is argued that the mechanism of primary atomization is similar to that of a liquid drop suddenly exposed to a high-speed gas stream. A phenomenological breakup model is proposed for the initial droplet size, based on the accelerative destabilization of the liquid jet surface by the Rayleigh-Taylor instability. Measurements of droplet sizes and surface wavelengths are shown to be in good agreement with the model predictions. The downstream evolution of the droplet-size distribution is also investigated, with consideration given to several secondary mechanisms including turbulent breakup, droplet-droplet collisions, and droplet acceleration. It is argued that the relative acceleration of droplets of different size classes, and energetic collisions between droplets, are together responsible for the experimentally observed variation of the mean drop size with downstream distance from the injection plane in the far-field of the spray. The feasibility of coaxial liquid-gas injection for pulse detonation engine (PDE) applications is additionally considered. The performance of coaxial atomizers under transient operating conditions appropriate to PDEs is analyzed along with the capability of this injection scheme to produce sufficiently small droplet sizes within restricted flow regimes. The ability to tailor the radial distributions of both the liquid mass flux and droplet sizes through the addition of swirl to the coaxial

  18. Investigation on cone jetting regimes of liquid droplets subjected to pyroelectric fields induced by laser blasts

    NASA Astrophysics Data System (ADS)

    Gennari, Oriella; Battista, Luigi; Silva, Benjamin; Grilli, Simonetta; Miccio, Lisa; Vespini, Veronica; Coppola, Sara; Orlando, Pierangelo; Aprin, Laurent; Slangen, Pierre; Ferraro, Pietro

    2015-02-01

    Electrical conductivity and viscosity play a major role in the tip jetting behaviour of liquids subjected to electrohydrodynamic (EHD) forces, thus influencing significantly the printing performance. Recently, we developed a nozzle- and electrode-free pyro-EHD system as a versatile alternative to conventional EHD configurations and we demonstrated different applications, including inkjet printing and three-dimensional lithography. However, only dielectric fluids have been used in all of those applications. Here, we present an experimental characterization of the pyro-EHD jetting regimes, induced by laser blasts, of sessile drops in case of dielectric and conductive liquids in order to extend the applicability of the system to a wider variety of fields including biochemistry and biotechnology where conductive aqueous solutions are typically used.

  19. Rupture of thin liquid films induced by impinging air-jets.

    PubMed

    Berendsen, Christian W J; Zeegers, Jos C H; Kruis, Geerit C F L; Riepen, Michel; Darhuber, Anton A

    2012-07-01

    Thin liquid films on partially wetting substrates are subjected to laminar axisymmetric air-jets impinging at normal incidence. We measured the time at which film rupture occurs and dewetting commences as a function of diameter and Reynolds number of the air-jet. We developed numerical models for the air flow as well as the height evolution of the thin liquid film. The experimental results were compared with numerical simulations based on the lubrication approximation and a phenomenological expression for the disjoining pressure. We achieved quantitative agreement for the rupture times. We found that the film thickness profiles were highly sensitive to the presence of minute quantities of surface-active contaminants. PMID:22671425

  20. Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1987-01-01

    Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a sampling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less effected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

  1. Vortex Interactions on Plunging Airfoil and Wings

    NASA Astrophysics Data System (ADS)

    Eslam Panah, Azar; Buchholz, James

    2012-11-01

    The development of robust qualitative and quantitative models for the vorticity fields generated by oscillating foils and wings can provide a framework in which to understand flow interactions within groups of unsteady lifting bodies (e.g. shoals of birds, fish, MAV's), and inform low-order aerodynamic models. In the present experimental study, the flow fields generated by a plunging flat-plate airfoil and finite-aspect-ratio wing are characterized in terms of vortex topology, and circulation at Re=10,000. Strouhal numbers (St=fA/U) between 0.1 and 0.6 are investigated for plunge amplitudes of ho/c = 0.2, 0.3, and 0.4, resulting in reduced frequencies (k= π fc/U) between 0.39 and 4.71. For the nominally two-dimensional airfoil, the number of discrete vortex structures shed from the trailing edge, and the trajectory of the leading edge vortex (LEV) and its interaction with trailing edge vortex (TEV) are found to be primarily governed by k; however, for St >0.4, the role of St on these phenomena increases. Likewise, circulation of the TEV exhibits a dependence on k; however, the circulation of the LEV depends primarily on St. The growth and ultimate strength of the LEV depends strongly on its interaction with the body; in particular, with a region of opposite-sign vorticity generated on the surface of the body due to the influence of the LEV. In the finite-aspect-ratio case, spanwise flow is also a significant factor. The roles of these phenomena on vortex evolution and strength will be discussed in detail.

  2. An Experimental Study of the Droplets Produced by a Plunging Breaker

    NASA Astrophysics Data System (ADS)

    Wang, D.; Liu, X.; Duncan, J. H.

    2011-11-01

    The dynamics of droplets generated by plunging breakers are experimentally studied in a wave tank that is 12 m long and 1.22 m wide with a water depth of 0.91 m. Breakers with various breaking intensity are generated from a packet of dispersively focused waves with average frequency of 1.15 Hz by varying the amplitude of wave maker motion. The sizes and motions of droplets at various positions relative the wave crest are measured with a cinematic shadowgraph technique, while the profile histories of the breaking wave crest along the center plane of the tank are simultaneously measured with a cinematic laser-induced fluorescence technique. Droplets are primarily created when strong turbulence is generated after the plunging jet impacts with the front face of the wave and when large air bubbles, entrapped during the plunging process, rise to the free surface and pop. The diameters and velocities of the droplets across one horizontal plane at an elevation just above the wave crest height are measured. The surface roughnesses of the breaking waves are estimated from the measured wave crest profile histories. The correlation between the flux of droplets and the surface roughness is investigated. Supported by the National Science Foundation, Division of Ocean Sciences, Grant OCE0751853.

  3. Thrust Enhancement of Flapping Wings in Tandem and Biplane Configurations by Pure Plunging Motion

    NASA Astrophysics Data System (ADS)

    Yilmaz, S. Banu; Sahin, Mehmet; Unal, M. Fevzi

    2012-11-01

    The propulsion performance of flapping NACA0012 airfoils undergoing harmonic plunging motion in tandem and biplane wing configurations is investigated numerically. An unstructured finite volume solver based on Arbitrary Lagrangian-Eulerian formulation is utilized in order to solve the incompressible unsteady Navier-Stokes equations. Four different tandem and four different biplane wing combinations are considered. Various instantaneous and time-averaged aerodynamic parameters including lift and drag coefficients, vorticity contours and streamlines are calculated for each case and compared with each other. As a reference the single wing case corresponding to the deflected jet phenomenon in Jones and Platzer (Exp. Fluids 46:799-810, 2009) is also studied. In these simulations, the Reynolds number is chosen as 252, the reduced frequency of plunging motion (k = 2 πf /U∞) is 12.3 and the plunge amplitude non-dimensionalized with respect to chord is 0.12. The solutions of the single wing case indicate dependence on the location of start-up vortices. Meanwhile the multiple wing configurations indicate that the highest thrust enhancement is obtained in one of the biplane cases where the two wings closely moving towards each other namely biplane asynchronous-closer case.

  4. Self-assembling array of magnetoelectrostatic jets from the surface of a superparamagnetic ionic liquid.

    PubMed

    King, Lyon B; Meyer, Edmond; Hopkins, Mark A; Hawkett, Brian S; Jain, Nirmesh

    2014-12-01

    Electrospray is a versatile technology used, for example, to ionize biomolecules for mass spectrometry, create nanofibers and nanowires, and propel spacecraft in orbit. Traditionally, electrospray is achieved via microfabricated capillary needle electrodes that are used to create the fluid jets. Here we report on multiple parallel jetting instabilities realized through the application of simultaneous electric and magnetic fields to the surface of a superparamagnetic electrically conducting ionic liquid with no needle electrodes. The ionic liquid ferrofluid is synthesized by suspending magnetic nanoparticles in a room-temperature molten salt carrier liquid. Two ILFFs are reported: one based on ethylammonium nitrate (EAN) and the other based on EMIM-NTf2. The ILFFs display an electrical conductivity of 0.63 S/m and a relative magnetic permeability as high as 10. When coincident electric and magnetic fields are applied to these liquids, the result is a self-assembling array of emitters that are composed entirely of the colloidal fluid. An analysis of the magnetic surface stress induced on the ILFF shows that the electric field required for transition to spray can be reduced by as much as 4.5 × 10(7) V/m compared to purely electrostatic spray. Ferrofluid mode studies in nonuniform magnetic fields show that it is feasible to realize arrays with up to 16 emitters/mm(2). PMID:25372842

  5. Time-resolved simulations and experiments of liquid jet break-up

    NASA Astrophysics Data System (ADS)

    Arienti, Marco; Soteriou, Marios; Sussman, Mark

    2008-11-01

    High-speed, high-resolution experimental visualization of the break-up of a liquid jet by a gaseous cross-flow has recently become possible due to advances in video camera technology. These visualizations can now be contrasted to high fidelity CFD simulations which are also just becoming possible due to continuing growth of computational capabilities. Such a contrast is expected to go beyond traditional comparisons of time-averaged quantities and focuses on dynamics. For example, comparisons of the characteristic break-up frequency and of the spatial instantaneous features of the jet may serve as validation of the computational model and to yield insight into the physics of the dynamic interplay between the disturbances induced by the injection device and Kelvin-Helmholtz / Rayleigh-Taylor instabilities at the interface. A state-of-the-art second-order coupled Level Set and Volume Of Fluid method (CLSVOF) that can capture liquid-gas interface dynamics is used for the study. High-speed videos of non-turbulent liquid injection in laminar crossflow are used to validate the time- and grid-converged capability of the code to capture upwind wave structures caused by the centrifugal acceleration of the deflected liquid. The extension to increasing air crossflow is also discussed with focus on the column break-up mechanism.

  6. Interaction of DC Microhollow Cathode Discharge Plasma Micro Jet with Liquid Media

    NASA Astrophysics Data System (ADS)

    Zhu, Weidong; Lopez, Jose; Becker, Kurt

    2008-10-01

    There have been different approaches in studying the interaction between plasma and liquid, such as sustained plasmas in contact with liquids and pulsed electric discharge in liquids. Recently, we have discovered that stable plasma can be sustained within a gas cavity maintained inside liquid media. A prototype device with key dimensions in sub-millimeter range were operated successfully in de-ionized water and turbo molecular pump oil with ambient air, pure nitrogen or pure oxygen used as the operating gas. Hydrogen Peroxide production in de-ionized water with ambient air as the working gas is estimated to be about 80 mg/L after 15 minutes plasma jet-water interaction while energy consumption is only about 8-10 W. With the radicals readily generated and directly introduced into the liquid media, it could lead to applications such as in-liquid bio-waste treatment, bio-rich liquid modification, in-situ monitoring/sensing, and filtration of by-products from VOC treatment by plasma.

  7. Two-Dimensional Optical Measurement of Waves on Liquid Lithium Jet Simulating IFMIF Target Flow

    SciTech Connect

    Kazuhiro Itoh; Hiroyuki Koterazawa; Taro Itoh; Yutaka Kukita; Hiroo Kondo; Nobuo Yamaoka; Hiroshi Horiike; Mizuho Ida; Hideo Nakamura; Hiroo Nakamura; Takeo Muroga

    2006-07-01

    Waves on a liquid-lithium jet flow, simulating a proposed high-energy beam target design, have been measured using an optical technique based on specular reflection of a single laser beam on the jet surface. The stream-wise and spanwise fluctuations of the local free-surface slope were least-square fitted with a sinusoidal curve to makeup the signals lost due to the constriction in the optical arrangement. The waveform was estimated with an assumption that wave phase speed can be calculated using the dispersion relation for linear capillary-gravity waves. The direction of propagation on the jet surface was also evaluated so that the wave amplitudes, calculated by integral of slope angle signal, agree consistently in stream-wise and spanwise direction. These measurements and analyses show that the waves at the measurement location for a jet velocity of 1.2 m/s can best be represented by oblique waves with an inclination of 1.23 rad, a wavelength of 3.8 mm and a wave amplitude of about 0.05 mm. (authors)

  8. Charge and energy transferred from a plasma jet to liquid and dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Mussard, M. Dang Van Sung; Foucher, E.; Rousseau, A.

    2015-10-01

    A key parameter in using plasma jets for biomedical applications is the transferred energy to the living tissues. The objective of this paper is to understand which parameters control the energy transfer from the plasma jet to a liquid or a dielectric surface. The plasma jet is flown with helium and ignited by a 600 Hz ac high voltage (up to 15 kV). Capacitors are connected to two measurement electrodes placed in the plasma source region, and under the sample. Charge and energy transferred are estimated by plotting Lissajous cycles; the number of bullets and the charge probability density function are also calculated. It is shown that the applied voltage and the gap (distance between the end of the tube and the sample) have a dramatic influence on the energy deposition on the sample as well as on the charge probability density function. Surprisingly, both gap distance and voltage have very little influence on the number of bullets reaching the sample per cycle. It is also shown that the conductivity of the liquid sample has almost no influence on the energy deposition and charge probability density function.

  9. New approach of a traditional analysis for predicting near-exit jet liquid instabilities

    NASA Astrophysics Data System (ADS)

    Jaramillo, Guillermo; Collicott, Steven

    2015-11-01

    Traditional linear instability theory for round liquid jets requires an exit-plane velocity profile be assumed so as to derive the characteristic growth rates and wavelengths of instabilities. This requires solving an eigenvalue problem for the Rayleigh Equation. In this new approach, a hyperbolic tangent velocity profile is assumed at the exit-plane of a round jet and a comparison is made with a hyperbolic secant profile. Temporal and Spatial Stability Analysis (TSA and SSA respectively) are the employed analytical tools to compare results of predicted most-unstable wavelengths from the given analytical velocity profiles and from previous experimental work. The local relevance of the velocity profile in the near-exit region of a liquid jet and the validity of an inviscid formulation through the Rayleigh equation are discussed as well. A comparison of numerical accuracy is made between two different mathematical approaches for the hyperbolic tangent profile with and without the Ricatti transformation. Reynolds number based on the momentum thickness of the boundary layer at the exit plane non-dimensionalizes the problem and, the Re range, based on measurements by Portillo in 2011, is 185 to 600. Wavelength measurements are taken from Portillo's experiment. School of Mechanical Engineering at Universidad del Valle, supported by a grant from Fulbright and Colciencias. Ph.D. student at the School of Aeronautics and Astronautics Purdue University.

  10. Small-animal tomography with a liquid-metal-jet x-ray source

    NASA Astrophysics Data System (ADS)

    Larsson, D. H.; Lundström, U.; Westermark, U.; Takman, P. A. C.; Burvall, A.; Arsenian Henriksson, M.; Hertz, H. M.

    2012-03-01

    X-ray tomography of small animals is an important tool for medical research. For high-resolution x-ray imaging of few-cm-thick samples such as, e.g., mice, high-brightness x-ray sources with energies in the few-10-keV range are required. In this paper we perform the first small-animal imaging and tomography experiments using liquid-metal-jet-anode x-ray sources. This type of source shows promise to increase the brightness of microfocus x-ray systems, but present sources are typically optimized for an energy of 9 keV. Here we describe the details of a high-brightness 24-keV electron-impact laboratory microfocus x-ray source based on continuous operation of a heated liquid-In/Ga-jet anode. The source normally operates with 40 W of electron-beam power focused onto the metal jet, producing a 7×7 μm2 FWHM x-ray spot. The peak spectral brightness is 4 × 109 photons / ( s × mm2 × mrad2 × 0.1%BW) at the 24.2 keV In Kα line. We use the new In/Ga source and an existing Ga/In/Sn source for high-resolution imaging and tomography of mice.

  11. Liquid and gelled sprays for mixing hypergolic propellants using an impinging jet injection system

    NASA Astrophysics Data System (ADS)

    James, Mark D.

    The characteristics of sprays produced by liquid rocket injectors are important in understanding rocket engine ignition and performance. The includes, but is not limited to, drop size distribution, spray density, drop velocity, oscillations in the spray, uniformity of mixing between propellants, and the spatial distribution of drops. Hypergolic ignition and the associated ignition delay times are also important features in rocket engines, providing high reliability and simplicity of the ignition event. The ignition delay time is closely related to the level and speed of mixing between a hypergolic fuel and oxidizer, which makes the injection method and conditions crucial in determining the ignition performance. Although mixing and ignition of liquid hypergolic propellants has been studied for many years, the processes for injection, mixing, and ignition of gelled hypergolic propellants are less understood. Gelled propellants are currently under investigation for use in rocket injectors to combine the advantages of solid and liquid propellants, although not without their own difficulties. A review of hypergolic ignition has been conducted for selected propellants, and methods for achieving ignition have been established. This research is focused on ignition using the liquid drop-on-drop method, as well as the doublet impinging jet injector. The events leading up to ignition, known as pre-ignition stage are discussed. An understanding of desirable ignition and combustion performance requires a study of the effects of injection, temperature, and ambient pressure conditions. A review of unlike-doublet impinging jet injection mixing has also been conducted. This includes mixing factors in reactive and non-reactive sprays. Important mixing factors include jet momentum, jet diameter and length, impingement angle, mass distribution, and injector configuration. An impinging jet injection system is presented using an electro-mechanically driven piston for injecting liquid

  12. Direct numerical simulations of temporally developing turbulent reacting liquid-fueled jets

    NASA Astrophysics Data System (ADS)

    Shashank, Shashank; Pitsch, Heinz

    2012-11-01

    Liquid fueled engines are ubiquitous in the transportation industry because liquid fuel minimizes the weight and volume of propulsion systems. The combustion that occurs in these engines is an inherently multi-physics process, involving fuel evaporation, reaction kinetics, and high levels of turbulence. A desire for high fidelity data that explains complex interaction between different physical mechanisms motivates the consideration of direct numerical simulation (DNS) as an investigation tool. In this study three-dimensional DNS of a reacting n-heptane liquid fueled temporal jet have been performed to study auto-ignition and subsequent burning in conditions that are representative of a diesel engine environment. In these simulations the continuous phase is described using an Eulerian representation whereas Lagrangian particle tracking is used to model the dispersed phase. The results of this study will demonstrate the importance of unsteady effects, and of accounting for the interaction between different modes of combustion, when simulating spray combustion.

  13. Liquid helium inertial jet for comparative study of classical and quantum turbulence

    SciTech Connect

    Duri, D.; Charvin, P.; Rousset, B.; Poncet, J.-M.; Diribarne, P.

    2011-11-15

    We present a new cryogenic wind tunnel facility developed to study the high Reynolds number developed classical or quantum turbulence in liquid {sup 4}He. A stable inertial round jet flow with a Reynolds number of 4 x 10{sup 6} can be sustained in both He I and He II down to a minimum temperature of 1.7 K. The circuit can be pressurized up to 3.5 x 10{sup 5} Pa. The system has been designed to exploit the self-similar properties of the jet far field in order to adapt to the spatial resolution of the existing probes. Multiple and complementary sensors can be simultaneously installed to obtain spatial and time resolved measurements. The technical difficulties and design details are described and the system performance is presented.

  14. Hydrocarbon group type determination in jet fuels by high performance liquid chromatography

    NASA Technical Reports Server (NTRS)

    Antoine, A. C.

    1977-01-01

    Results are given for the analysis of some jet and diesel fuel samples which were prepared from oil shale and coal syncrudes. Thirty-two samples of varying chemical composition and physical properties were obtained. Hydrocarbon types in these samples were determined by fluorescent indicator adsorption (FIA) analysis, and the results from three laboratories are presented and compared. Recently, rapid high performance liquid chromatography (HPLC) methods have been proposed for hydrocarbon group type analysis, with some suggestion for their use as a replacement of the FIA technique. Two of these methods were used to analyze some of the samples, and these results are also presented and compared. Two samples of petroleum-based Jet A fuel are similarly analyzed.

  15. Jet Pump for Liquid Helium Circulation Through the Fast Cycling Magnets of Nuclotron

    NASA Astrophysics Data System (ADS)

    Agapov, Nikolay; Emelianov, Nikita; Mitrofanova, Julia; Nikiforov, Dmitry

    Nuclotron is the first fast cycling superconducting synchrotron intended for the acceleration of high-energy nuclei and heavy ions. Its cryogenic system includes two helium refrigerators with a total capacity of 4000 W at 4.5 K. The 251.5 m long accelerator ring consists of 144 superconducting dipole and quadruple magnets. The magnets connected in parallel are refrigerated by a two-phase flow of boiling helium. In order to increase liquid helium flow directed to the superconducting magnets, jet pumps are used. We explain theoretical and experimental results that allow one to determinate main technical specifications and optimal geometric dimensions of the jet pumps. The experience of using this device and corresponding flow diagrams are described.

  16. Photoelectron spectroscopy of liquid water, some alcohols, and pure nonane in free micro jets

    NASA Astrophysics Data System (ADS)

    Faubel, Manfred; Steiner, Björn; Toennies, J. Peter

    1997-06-01

    The recently developed technique of accessing volatile liquids in a high vacuum environment by using a very thin liquid jet is implemented to carry out the first measurements of photoelectron spectra of pure liquid water, methanol, ethanol, 1-propanol, 1-butanol, and benzyl alcohol as well as of liquid n-nonane. The apparatus, which consists of a commercial hemispherical (10 cm mean radius) electron analyzer and a hollow cathode discharge He I light source is described in detail and the problems of the sampling of the photoelectrons in such an environment are discussed. For water and most of the alcohols up to six different electronic bands could be resolved. The spectra of 1-butanol and n-nonane show two weakly discernable peaks from which the threshold ionization potential could be determined. A deconvolution of the photoelectron spectra is used to extract ionization potentials of individual molecular bands of molecules near the surface of the liquid and shifts of the order of 1 eV compared to the gas phase are observed. A molecular orientation for water molecules at the surface of liquid water is inferred from a comparison of the relative band strengths with the gas phase. Similar effects are also observed for some of the alcohols. The results are discussed in terms of a simple "Born-solvation" model.

  17. Identification of the biologically active liquid chemistry induced by a nonthermal atmospheric pressure plasma jet.

    PubMed

    Wende, Kristian; Williams, Paul; Dalluge, Joe; Gaens, Wouter Van; Aboubakr, Hamada; Bischof, John; von Woedtke, Thomas; Goyal, Sagar M; Weltmann, Klaus-Dieter; Bogaerts, Annemie; Masur, Kai; Bruggeman, Peter J

    2015-01-01

    The mechanism of interaction of cold nonequilibrium plasma jets with mammalian cells in physiologic liquid is reported. The major biological active species produced by an argon RF plasma jet responsible for cell viability reduction are analyzed by experimental results obtained through physical, biological, and chemical diagnostics. This is complemented with chemical kinetics modeling of the plasma source to assess the dominant reactive gas phase species. Different plasma chemistries are obtained by changing the feed gas composition of the cold argon based RF plasma jet from argon, humidified argon (0.27%), to argon/oxygen (1%) and argon/air (1%) at constant power. A minimal consensus physiologic liquid was used, providing isotonic and isohydric conditions and nutrients but is devoid of scavengers or serum constituents. While argon and humidified argon plasma led to the creation of hydrogen peroxide dominated action on the mammalian cells, argon-oxygen and argon-air plasma created a very different biological action and was characterized by trace amounts of hydrogen peroxide only. In particular, for the argon-oxygen (1%), the authors observed a strong negative effect on mammalian cell proliferation and metabolism. This effect was distance dependent and showed a half life time of 30 min in a scavenger free physiologic buffer. Neither catalase and mannitol nor superoxide dismutase could rescue the cell proliferation rate. The strong distance dependency of the effect as well as the low water solubility rules out a major role for ozone and singlet oxygen but suggests a dominant role of atomic oxygen. Experimental results suggest that O reacts with chloride, yielding Cl2(-) or ClO(-). These chlorine species have a limited lifetime under physiologic conditions and therefore show a strong time dependent biological activity. The outcomes are compared with an argon MHz plasma jet (kinpen) to assess the differences between these (at least seemingly) similar plasma sources

  18. Experimental Investigation of Jet Impingement Heat Transfer Using Thermochromic Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Dempsey, Brian Paul

    1997-01-01

    Jet impingement cooling of a hypersonic airfoil leading edge is experimentally investigated using thermochromic liquid crystals (TLCS) to measure surface temperature. The experiment uses computer data acquisition with digital imaging of the TLCs to determine heat transfer coefficients during a transient experiment. The data reduction relies on analysis of a coupled transient conduction - convection heat transfer problem that characterizes the experiment. The recovery temperature of the jet is accounted for by running two experiments with different heating rates, thereby generating a second equation that is used to solve for the recovery temperature. The resulting solution requires a complicated numerical iteration that is handled by a computer. Because the computational data reduction method is complex, special attention is paid to error assessment. The error analysis considers random and systematic errors generated by the instrumentation along with errors generated by the approximate nature of the numerical methods. Results of the error analysis show that the experimentally determined heat transfer coefficients are accurate to within 15%. The error analysis also shows that the recovery temperature data may be in error by more than 50%. The results show that the recovery temperature data is only reliable when the recovery temperature of the jet is greater than 5 C, i.e. the jet velocity is in excess of 100 m/s. Parameters that were investigated include nozzle width, distance from the nozzle exit to the airfoil surface, and jet velocity. Heat transfer data is presented in graphical and tabular forms. An engineering analysis of hypersonic airfoil leading edge cooling is performed using the results from these experiments. Several suggestions for the improvement of the experimental technique are discussed.

  19. Temporal instability of coflowing liquid-gas jets under an electric field

    NASA Astrophysics Data System (ADS)

    Li, Guangbin; Luo, Xisheng; Si, Ting; Xu, Ronald X.

    2014-05-01

    Temporal instability of an electrified liquid jet in the core of a high-speed gas stream is studied to better understand the electro-flow focusing (EFF) technique. Two types of physical models with and without viscosities of fluids are considered. One utilizes uniform basic flow and an axial electric field, while the other one considers both the axial and radial electric fields and employs appropriate velocity profiles based on the pipe flow for inner liquid and the error function for outer gas stream. Both models demonstrate that the axisymmetric instability and the helical instability are two most unstable modes in the EFF problem. The significance of free charge initially imposed on the interface is highlighted and the effects of surface tension and liquid viscosity on the jet instability are also studied. It is shown that the increase of free charge density can definitely promote both the axisymmetric and helical instabilities and the transition between them arises for sufficiently large free charge densities when the axial electric field intensity increases. Finally, the EFF experiments are carried out to compare with theoretical predictions in the temporal instability analysis and a good agreement between them is achieved.

  20. Bubble and liquid flow characteristics in a cylindrical bath during swirl motion of bubbling jet

    NASA Astrophysics Data System (ADS)

    Iguchi, Manabu; Kondoh, Tsuneo; Uemura, Tomomasa; Yamamoto, Fujio; Morita, Zen-Ichiro

    1994-02-01

    Gas injection into a cylindrical bath through a centric bottom nozzle causes a swirl motion like rotary sloshing. Conditions indicating the initiation and cessation of the swirl motion have been made clear by many researchers. So far, the effect of the swirl motion on transport phenomena in the bath is not clear yet. The present study was made to clarify the bubble characteristics (void fraction, bubble frequency) and liquid flow characteristics (mean velocity, turbulence intensity, Reynolds shear stress) during swirl motion of bubbling jet. These two characteristics were investigated using an electro-resistivity probe and a two-dimensional LDV, respectively.

  1. A closed-loop pump-driven wire-guided flow jet for ultrafast spectroscopy of liquid samples

    NASA Astrophysics Data System (ADS)

    Picchiotti, Alessandra; Prokhorenko, Valentyn I.; Miller, R. J. Dwayne

    2015-09-01

    We describe the design and provide the results of the full characterization of a closed-loop pump-driven wire-guided flow jet system. The jet has excellent optical quality with a wide range of liquids spanning from alcohol to water based solutions, including phosphate buffers used for biological samples. The thickness of the jet film varies depending on the flow rate between 90 μm and 370 μm. The liquid film is very stable, and its thickness varies only by 0.76% under optimal conditions. Measured transmitted signal reveals a long term optical stability (hours) with a RMS of 0.8%, less than the overall noise of the spectroscopy setup used in our experiments. The closed loop nature of the overall jet design has been optimized for the study of precious biological samples, in limited volumes, to remove window contributions from spectroscopic observables. This feature is particularly important for femtosecond studies in the UV range.

  2. Black hole binary inspiral: Analysis of the plunge

    NASA Astrophysics Data System (ADS)

    Price, Richard H.; Nampalliwar, Sourabh; Khanna, Gaurav

    2016-02-01

    Binary black hole coalescence has its peak of gravitational-wave generation during the "plunge," the transition from quasicircular early motion to late quasinormal ringing (QNR). Although advances in numerical relativity have provided plunge waveforms, there is still no intuitive or phenomenological understanding of plunge comparable to that of the early and late stages. Here we make progress in developing such understanding by relying on insights of the linear mathematics of the particle perturbation model for the extreme mass limit. Our analysis, based on the Fourier-domain Green function, and a simple initial model, point to the crucial role played by the kinematics near the "light ring" (the circular photon orbit) in determining the plunge radiation and the excitation of QNR. That insight is then shown to successfully explain results obtained for particle motion in a Schwarzschild background.

  3. Liquid phase products and solid deposit formation from thermally stressed model jet fuels

    NASA Technical Reports Server (NTRS)

    Kim, W. S.; Bittker, D. A.

    1984-01-01

    The relationship between solid deposit formation and liquid degradation product concentration was studied for the high temperature (400 C) stressing of three hydrocarbon model fuels. A Jet Fuel Thermal Oxidation Tester was used to simulate actual engine fuel system conditions. The effects of fuel type, dissolved oxygen concentration, and hot surface contact time (reaction time) were studied. Effects of reaction time and removal of dissolved oxygen on deposit formation were found to be different for n-dodecane and for 2-ethylnaphthalene. When ten percent tetralin is added to n-dodecane to give a simpler model of an actual jet fuel, the tetralin inhibits both the deposit formation and the degradation of n-dodecane. For 2-ethylnaphthalene primary product analyses indicate a possible self-inhibition at long reaction times of the secondary reactions which form the deposit precursors. The mechanism of the primary breakdown of these fuels is suggested and the primary products which participate in these precursor-forming reactions are identified. Some implications of the results to the thermal degradation of real jet fuels are given.

  4. Exhaust emissions from a premixing, prevaporizing flame tube using liquid jet A fuel

    NASA Technical Reports Server (NTRS)

    Marek, C. J.; Papathakos, L. C.

    1976-01-01

    Emissions of nitrogen oxides, carbon monoxide, and unburned hydrocarbons were measured in a burner where liquid Jet A fuel was sprayed into the heated air stream and vaporized upstream of a perforated plate flameholder. The burner was tested at inlet air temperatures at 640, 800, and 833 K, an inlet pressure of 5.6 X 100,000 N/m squared, a reference velocity of 25 m/sec, and equivalence ratios from lean blowout to 0.7. Nitrogen oxide levels of below 1.0 g NO2/kg fuel were obtained at combustion efficiencies greater than 99 percent. The measured emission levels for the liquid fuel agreed well with previously reported premixed gaseous propane data and agreed with well stirred reactor predictions. Autoignition of the premixed fuel air mixture was a problem at inlet temperatures above 650 K with 104 msec premixing time.

  5. Sun-plunging Comets and Cometary Flares

    NASA Astrophysics Data System (ADS)

    Brown, J. C.; Carlson, R. W.

    2012-12-01

    During 2011, NASA's Solar Dynamics Observatory (SDO) made the first ever direct observations of sun-grazing comet destruction in the inner solar atmosphere. On July 6, the nucleus material of Comet C/2011 N3 (SOHO) (perihelion distance q~1.14R_sun) was observed to vaporize, decelerate and radiate, with total nucleus destruction over a path length ~ R_sun through the lower corona (density n ~ 10^8/cm^3). On Dec. 16, the much more massive Comet C/2011 W3 (Lovejoy), with similar q~1.17 R_sun), was seen vaporizing until it vanished behind the solar limb then re-emerging in a much diminished state. A range of current work on these data is being presented by others in this AGU session. These two 'sun-skimming' comets had q in the low corona. There, mass loss is dominated by insolation-driven sublimation, so the physics of their destruction is largely similar to those with q>> R_sun. However, Brown et al. (Astron. Astrophys. 535, A71, 2011) showed that mass loss and destruction is completely different for 'sun-plunging' comets with qn*= 2.5x10^11/cm^3, increasing exponentially with depth on scale height H~100-500 km). Consequently sun-plunger mass loss and destruction is dominated by ablation and by ram-pressure-driven explosion. The very large cometary kinetic energy (2x10^27 erg x (M/10^12) for mass M g) and its highly localized deposition in time (<10 s) and space (<6000 km ~ 10") should produce signatures somewhat like solar magnetic flares. Such 'cometary flare' events should offer wholly new ways to probe properties both of comets (e.g. element abundances) and of the low solar atmosphere (e.g magnetic fields). Super-flares produced by very large sun-plungers could have serious terrestrial consequences. We will present and discuss results of our current work on sun-plunging comets and explosive cometary flares, including

  6. A computer model for liquid jet atomization in rocket thrust chambers

    NASA Astrophysics Data System (ADS)

    Giridharan, M. G.; Lee, J. G.; Krishnan, A.; Yang, H. Q.; Ibrahim, E.; Chuech, S.; Przekwas, A. J.

    1991-12-01

    The process of atomization has been used as an efficient means of burning liquid fuels in rocket engines, gas turbine engines, internal combustion engines, and industrial furnaces. Despite its widespread application, this complex hydrodynamic phenomenon has not been well understood, and predictive models for this process are still in their infancy. The difficulty in simulating the atomization process arises from the relatively large number of parameters that influence it, including the details of the injector geometry, liquid and gas turbulence, and the operating conditions. In this study, numerical models are developed from first principles, to quantify factors influencing atomization. For example, the surface wave dynamics theory is used for modeling the primary atomization and the droplet energy conservation principle is applied for modeling the secondary atomization. The use of empirical correlations has been minimized by shifting the analyses to fundamental levels. During applications of these models, parametric studies are performed to understand and correlate the influence of relevant parameters on the atomization process. The predictions of these models are compared with existing experimental data. The main tasks of this study were the following: development of a primary atomization model; development of a secondary atomization model; development of a model for impinging jets; development of a model for swirling jets; and coupling of the primary atomization model with a CFD code.

  7. Formation and post-formation dynamics of bacterial biofilm streamers as highly viscous liquid jets

    NASA Astrophysics Data System (ADS)

    Das, Siddhartha; Kumar, Aloke

    2014-11-01

    It has been recently reported that in presence of low Reynolds number (Re << 1) transport, preformed bacterial biofilms, several hours after their formation, may degenerate in form of filamentous structures, known as streamers. In this work, we explain that such streamers form as the highly viscous liquid states of the intrinsically viscoelastic biofilms. Such ``viscous liquid'' state can be hypothesized by noting that the time of appearance of the streamers is substantially larger than the viscoelastic relaxation time scale of the biofilms, and this appearance is explained by the inability of a viscous liquid to withstand external shear. Further, by identifying the post formation dynamics of the streamers as that of a viscous liquid jet in a surrounding flow field, we can interpret several unexplained issues associated with the post-formation dynamics of streamers, such as the clogging of the flow passage or the exponential time growth of streamer dimensions. Overall our manuscript provides a biophysical basis for understanding the evolution of biofilm streamers in creeping flows.

  8. On the absence of asymmetric wakes for periodically plunging finite wings

    NASA Astrophysics Data System (ADS)

    Calderon, D. E.; Cleaver, D. J.; Gursul, I.; Wang, Z.

    2014-07-01

    It has previously been shown that, at high Strouhal numbers, oscillating airfoils can produce deflected jets that can create very high lift-coefficients for otherwise symmetric scenarios. These deflected jets form through pairing of the trailing-edge vortices to create asymmetric vortex couples that self-propel at an angle to the freestream, resulting in an asymmetric flow field and non-zero lift. In this paper results are presented that indicate these high-lift deflected jets cannot form for finite wings. Instead of the straight vortex tubes that pair and convect at an angle to the freestream observed for effectively infinite wings, finite wings exhibit vortex tubes that break into two branches near the tip forming double helix structures. One branch connects with the last vortex; one branch connects with the next vortex. This creates a long "daisy chain" of interconnected trailing edge vortices forming a long series of vortex loops. These symmetric flow fields are shown to persist for finite wings even to Strouhal numbers more than twice those required to produce asymmetric wakes on plunging airfoils. Two contributing reasons are discussed for why deflected jets are not observed. First the tip vortex creates three-dimensionality that discourages vortex coupling. Second, the symmetry of the circulation of the interconnected vortex loops, which has been confirmed by the experiments, is a natural consequence of the vortex topology. Therefore, the asymmetry in trailing edge vortex strength previously observed as characteristic of deflected jets cannot be supported for finite wings.

  9. Experimental and numerical investigations of the impingement of an oblique liquid jet onto a superhydrophobic surface: energy transformation

    NASA Astrophysics Data System (ADS)

    Kibar, Ali

    2016-02-01

    This study presents the theory of impinging an oblique liquid jet onto a vertical superhydrophobic surface based on both experimental and numerical results. A Brassica oleracea leaf with a 160° apparent contact angle was used for the superhydrophobic surface. Distilled water was sent onto the vertical superhydrophobic surface in the range of 1750-3050 Reynolds number, with an inclination angle of 20°-40°, using a circular glass tube with a 1.75 mm inner diameter. The impinging liquid jet spread onto the surface governed by the inertia of the liquid and then reflected off the superhydrophobic surface due to the surface energy of the spreading liquid. Two different energy approaches, which have time-scale and per-unit length, were performed to determine transformation of the energy. The kinetic energy of the impinging liquid jet was transformed into the surface energy with an increasing interfacial surface area between the liquid and air during spreading. Afterwards, this surface energy of the spreading liquid was transformed into the reflection kinetic energy.

  10. OPTIMIZED DETERMINATION OF TRACE JET FUEL VOLATILE ORGANIC COMPOUNDS IN HUMAN BLOOD USING IN-FIELD LIQUID-LIQUID EXTRACTION WITH SUBSEQUENT LABORATORY GAS CHROMATOGRAPHIC-MASS SPECTROMETRIC ANALYSIS AND ON-COLUMN LARGE VOLUME INJECTION

    EPA Science Inventory

    A practical and sensitive method to assess volatile organic compounds (VOCs) from JP-8 jet fuel in human whole blood was developed by modifying previously established liquid-liquid extraction procedures, optimizing extraction times, solvent volume, specific sample processing te...

  11. The penetration of a soft solid by a liquid jet, with application to the administration of a needle-free injection.

    PubMed

    Shergold, Oliver A; Fleck, Norman A; King, Toby S

    2006-01-01

    Liquid jet injections have been performed on human skin in vivo and silicone rubber using Intraject needle-free injectors. The discharge characteristics of the liquid jet were measured using a custom-built test instrument. The experiments reveal that a high-speed liquid jet penetrates a soft solid by the formation and opening of a planar crack. The fluid stagnation pressure required for skin penetration decreases with increasing diameter of the liquid jet. These findings are consistent with the slow-speed penetration of a soft solid by a sharp-tipped punch. It is demonstrated that the Shergold-Fleck sharp-tipped punch penetration model [Shergold, O.A., Fleck, N.A., 2004. Mechanisms of deep penetration of soft solids. Proc. Roy. Soc. Lond. A 460, 3037-3058.] gives adequate predictions for the pressure required to penetrate a soft solid by a high-speed liquid jet. PMID:16277987

  12. Formation and post-formation dynamics of bacterial biofilm streamers as highly viscous liquid jets

    PubMed Central

    Das, Siddhartha; Kumar, Aloke

    2014-01-01

    It has been recently reported that in presence of low Reynolds number (Re ≪ 1) transport, preformed bacterial biofilms, several hours after their formation, may degenerate in form of filamentous structures, known as streamers. In this work, we explain that such streamers form as the highly viscous liquid states of the intrinsically viscoelastic biofilms. Such “viscous liquid” state can be hypothesized by noting that the time of appearance of the streamers is substantially larger than the viscoelastic relaxation time scale of the biofilms, and this appearance is explained by the inability of a viscous liquid to withstand external shear. Further, by identifying the post formation dynamics of the streamers as that of a viscous liquid jet in a surrounding flow field, we can interpret several unexplained issues associated with the post-formation dynamics of streamers, such as the clogging of the flow passage or the exponential time growth of streamer dimensions. Overall our manuscript provides a biophysical basis for understanding the evolution of biofilm streamers in creeping flows. PMID:25410423

  13. Absolute and convective instability of a viscous liquid jet surrounded by a viscous gas in a vertical pipe

    NASA Technical Reports Server (NTRS)

    Lin, S. P.; Lian, Z. W.

    1993-01-01

    The absolute and convective instability of a viscous liquid jet emanating into a viscous gas in a vertical pipe is analyzed in a parameter space spanned by the Reynolds number, the Froude number, the Weber number, the viscosity ratio, the density ratio, and the diameter ratio. The numerical results of the analysis are used to demonstrate that reduction in gravity tends to enhance the Rayleigh mode of convective instability which leads to the breakup of a liquid jet into drops of diameters comparable with the jet diameter. On the contrary, the Taylor mode of convective instability that leads to atomization is retarded at reduced gravity. The Rayleigh mode becomes absolutely unstable when the Reynolds number exceeds a critical value for a given set of the rest of the relevant parameters. The domain of absolute instability is significantly enlarged when the effect of gas viscosity is not neglected.

  14. Optimization of liquid jet system for laser-induced breakdown spectroscopy analysis

    NASA Astrophysics Data System (ADS)

    Skočovská, Katarína; Novotný, Jan; Prochazka, David; Pořízka, Pavel; Novotný, Karel; Kaiser, Jozef

    2016-04-01

    A complex optimization of geometrical and temporal parameters of a jet system (developed in Laser-induced breakdown spectroscopy (LIBS) laboratory of Brno University of Technology) for direct elemental analysis of samples in a liquid state of matter using LIBS was carried out. First, the peristaltic pump was synchronized with the flashlamp of the ablation laser, which reduced variation of the ablated sample amount. Also, the fluctuation of the laser ray angle incident on the jet surface was diminished. Such synchronization reduced signal standard deviations and thus increased repeatability of the measurements. Then, laser energy and distance of the focusing lens from the sample were optimized. The gate delay time and the gate width were optimized for single pulse (SP) experiments; the gate delay time and the inter-pulse delay were optimized for the use of double pulse (DP) variant. Results were assessed according to the highest signal to noise ratios and the lowest relative standard deviations of the signal. The sensitivity of the single pulse and the double pulse LIBS for the detection of heavy metals traces, copper (Cu i at 324.754 nm) and lead (Pb i at 405.781 nm), in aqueous solution of copper (ii) sulfate and lead (ii) acetate, was estimated in terms of limits of detection (LODs). As a result, sensitivity improvement of DP LIBS system was observed, the LOD of Cu obtained with DP was calculated 40% lower than LOD gained from SP technique.

  15. Effect of liquid droplets on turbulence in a round gaseous jet

    NASA Technical Reports Server (NTRS)

    Mostafa, A. A.; Elghobashi, S. E.

    1986-01-01

    The main objective of this investigation is to develop a two-equation turbulence model for dilute vaporizing sprays or in general for dispersed two-phase flows including the effects of phase changes. The model that accounts for the interaction between the two phases is based on rigorously derived equations for turbulence kinetic energy (K) and its dissipation rate epsilon of the carrier phase using the momentum equation of that phase. Closure is achieved by modeling the turbulent correlations, up to third order, in the equations of the mean motion, concentration of the vapor in the carrier phase, and the kinetic energy of turbulence and its dissipation rate for the carrier phase. The governing equations are presented in both the exact and the modeled formes. The governing equations are solved numerically using a finite-difference procedure to test the presented model for the flow of a turbulent axisymmetric gaseous jet laden with either evaporating liquid droplets or solid particles. The predictions include the distribution of the mean velocity, volume fractions of the different phases, concentration of the evaporated material in the carrier phase, turbulence intensity and shear stress of the carrier phase, droplet diameter distribution, and the jet spreading rate. The predictions are in good agreement with the experimental data.

  16. Terminal Liquid Mass Fractions and Terminal Mean Droplet Sizes in He Free-Jet Expansions

    SciTech Connect

    Knuth, E. L.; Kornilov, O.; Toennies, J. P.

    2011-05-20

    The terminal liquid mass fraction in He free-jet expansions is deduced from time-of-flight measurements using conservation of energy. Both the present results and results from prior measurements are correlated using a scaling parameter which was used previously for correlating droplet size as a function of source conditions. Deduced values of the mass fraction range from 0.047 to 0.42. The terminal mean droplet size is determined using a novel technique based on a size-dependent attenuation of the beam droplets when impacted by electrons. The determined sizes are in agreement with sizes obtained previously by crossing the droplet beam with an atomic beam, confirming the suitability of the present technique, which is relatively simple in comparison with crossing the droplet beam with an atomic beam. Measured values of the terminal velocity of the droplets are compared with values calculated for a model in which real-fluid properties are used for the enthalpy in the source but conversion of heat of condensation into energy of directed motion is neglected. The deviations from perfect-gas behavior in free-jet expansions are shown to be due to real-fluid properties and condensation.

  17. Optimization of liquid jet system for laser-induced breakdown spectroscopy analysis.

    PubMed

    Skočovská, Katarína; Novotný, Jan; Prochazka, David; Pořízka, Pavel; Novotný, Karel; Kaiser, Jozef

    2016-04-01

    A complex optimization of geometrical and temporal parameters of a jet system (developed in Laser-induced breakdown spectroscopy (LIBS) laboratory of Brno University of Technology) for direct elemental analysis of samples in a liquid state of matter using LIBS was carried out. First, the peristaltic pump was synchronized with the flashlamp of the ablation laser, which reduced variation of the ablated sample amount. Also, the fluctuation of the laser ray angle incident on the jet surface was diminished. Such synchronization reduced signal standard deviations and thus increased repeatability of the measurements. Then, laser energy and distance of the focusing lens from the sample were optimized. The gate delay time and the gate width were optimized for single pulse (SP) experiments; the gate delay time and the inter-pulse delay were optimized for the use of double pulse (DP) variant. Results were assessed according to the highest signal to noise ratios and the lowest relative standard deviations of the signal. The sensitivity of the single pulse and the double pulse LIBS for the detection of heavy metals traces, copper (Cu i at 324.754 nm) and lead (Pb i at 405.781 nm), in aqueous solution of copper (ii) sulfate and lead (ii) acetate, was estimated in terms of limits of detection (LODs). As a result, sensitivity improvement of DP LIBS system was observed, the LOD of Cu obtained with DP was calculated 40% lower than LOD gained from SP technique. PMID:27131663

  18. Deposition of micron liquid droplets on wall in impinging turbulent air jet

    NASA Astrophysics Data System (ADS)

    Liu, Tianshu; Nink, Jacob; Merati, Parviz; Tian, Tian; Li, Yong; Shieh, Tom

    2010-06-01

    The fluid mechanics of the deposition of micron liquid (olive oil) droplets on a glass wall in an impinging turbulent air jet is studied experimentally. The spatial patterns of droplets deposited on a wall are measured by using luminescent oil visualization technique, and the statistical data of deposited droplets are obtained through microscopic imagery. Two distinct rings of droplets deposited on a wall are found, and the mechanisms of the formation of the inner and outer rings are investigated based on global diagnostics of velocity and skin friction fields. In particular, the intriguing effects of turbulence, including large-scale coherent vortices and small-scale random turbulence, on micron droplet deposition on a wall and coalescence in the air are explored.

  19. Modeling the Restraint of Liquid Jets by Surface Tension in Microgravity

    NASA Technical Reports Server (NTRS)

    Chato, David J.; Jacqmim, David A.

    2001-01-01

    An axisymmetric phase field model is developed and used to model surface tension forces on liquid jets in microgravity. The previous work in this area is reviewed and a baseline drop tower experiment selected 'for model comparison. A mathematical model is developed which includes a free surface. a symmetric centerline and wall boundaries with given contact angles. The model is solved numerically with a compact fourth order stencil on a equally spaced axisymmetric grid. After grid convergence studies, a grid is selected and all drop tower tests modeled. Agreement was assessed by comparing predicted and measured free surface rise. Trend wise agreement is good but agreement in magnitude is only fair. Suspected sources of disagreement are suspected to be lack of a turbulence model and the existence of slosh baffles in the experiment which were not included in the model.

  20. Effect of X-ray spot size on liquid jet photoelectron spectroscopy

    PubMed Central

    Olivieri, Giorgia; Goel, Alok; Kleibert, Armin; Brown, Matthew A.

    2015-01-01

    A 30 µm pinhole is introduced in the intermediate focus of the SIM beamline at the Swiss Light Source to improve the spot size at the second downstream focus, which is used here for liquid jet X-ray photoelectron spectroscopy experiments. The 30 µm pinhole reduces the beam dimensions from 250 (v) × 100 (h) µm to 75 × 45 µm for a vertical exit slit of 100 µm. The smaller X-ray spot results in a substantial decrease in the gas-phase contribution of the spectra from 40% down to 20% and will help to simplify the interpretation and peak assignments of future experiments. PMID:26524318

  1. EROSIVE WEAR OF DUCTILE METALS BY A PARTICLE-LADEN HIGH-VELOCITY LIQUID-JET

    SciTech Connect

    Li, Simon Ka-Keung; Humphrey, Joseph A.C.; Levy, Alan

    1980-12-01

    A liquid-solid particle jet impingement flow apparatus is described and experimental measurements are reported for the accelerated erosion of copper, aluminum and mild steel sheet metal by coal suspensions in kerosene and alumina and silicon carbide suspensions in water. Slurry velocities of up to 130 ft/sec (40 m/sec) and impingement angles ranging from 15 degrees to 90 degrees were investigated. The maximum particle concentration used was 40% by weight. For high velocity the results of this study show two erosion maxima arising at impingement angles of 90 degrees and 40 degrees respectively~ whereas in corresponding gas-solid particle investigations maximum erosion occurs at approximately 20 degrees. In the study both particle concentration and composition were varied. A polynomial regression technique was used to calculate empirical and semi-theoretical correlation constants.

  2. Liquid jet impingement normal to a disk in zero gravity. Ph.D. Thesis Toledo Univ.

    NASA Technical Reports Server (NTRS)

    Labus, T. L.

    1977-01-01

    The free surface shapes of circular liquid jets impinging normal to sharp-edged disks in zero gravity are determined. Zero gravity drop tower experiments yielded three distinct flow patterns that were classified in terms of the relative effects of surface tension and inertial forces. An order of magnitude analysis was conducted that indicated regions where viscous forces were not significant in the computation of free surface shapes. The free surface analysis was simplified by transforming the governing potential flow equations and boundary conditions into the inverse plane, where the stream function and velocity potential became the coordinates. The resulting nonlinear equations were solved by standard finite difference methods, and comparisons were made with the experimental data for the inertia dominated regime.

  3. Atomization and Dispersion of a Liquid Jet Injected Into a Crossflow of Air

    NASA Technical Reports Server (NTRS)

    Seay, J. E.; Samuelson, G. S.

    1996-01-01

    In recent years, environmental regulations have become more stringent, requiring lower emissions of mainly nitrogen oxides (NOx), as well as carbon monoxide (CO) and unburned hydrocarbons (UHC). These regulations have forced the gas turbine industry to examine non-conventional combustion strategies, such as the lean burn approach. The reasoning behind operating under lean conditions is to maintain the temperature of combustion near and below temperatures required for the formation of thermal nitric oxide (NO). To be successful, however, the lean processes require careful preparation of the fuel/air mixture to preclude formation of either locally rich reaction zones, which may give rise to NO formation, or locally lean reaction zones, which may give rise to inefficient fuel processing. As a result fuel preparation is crucial to the development and success of new aeroengine combustor technologies. A key element of the fuel preparation process is the fuel nozzle. As nozzle technologies have developed, airblast atomization has been adopted for both industrial and aircraft gas turbine applications. However, the majority of the work to date has focused on prefilming nozzles, which despite their complexity and high cost have become an industry standard for conventional combustion strategies. It is likely that the new strategies required to meet future emissions goals will utilize novel fuel injector approaches, such as radial injection. This thesis proposes and demonstrates an experiment to examine, on a mechanistic level (i.e., the physics of the action), the processes associated with the atomization, evaporation, and dispersion of a liquid jet introduced, from a radial, plain-jet airblast injector, into a crossflow of air. This understanding requires the knowledge not only of what factors influence atomization, but also the underlying mechanism associated with liquid breakup and dispersion. The experimental data acquired identify conditions and geometries for improved

  4. Ultraviolet vision and foraging in dip and plunge diving birds.

    PubMed

    Håstad, Olle; Ernstdotter, Emma; Odeen, Anders

    2005-09-22

    Many fishes are sensitive to ultraviolet (UV) light and display UV markings during courtship. As UV scatters more than longer wavelengths of light, these signals are only effective at short distances, reducing the risk of detection by swimming predators. Such underwater scattering will be insignificant for dip and plunge diving birds, which prey on fishes just below the water surface. One could therefore expect to find adaptations in the eyes of dip and plunge diving birds that tune colour reception to UV signals. We used a molecular method to survey the colour vision tuning of five families of dip or plunge divers and compared the results with those from sister taxa of other foraging methods. We found evidence of extended UV vision only in gulls (Laridae). Based on available evidence, it is more probable that this trait is associated with their terrestrial foraging habits rather than piscivory. PMID:17148194

  5. High-power liquid-lithium jet target for neutron production.

    PubMed

    Halfon, S; Arenshtam, A; Kijel, D; Paul, M; Berkovits, D; Eliyahu, I; Feinberg, G; Friedman, M; Hazenshprung, N; Mardor, I; Nagler, A; Shimel, G; Tessler, M; Silverman, I

    2013-12-01

    A compact liquid-lithium target (LiLiT) was built and tested with a high-power electron gun at the Soreq Nuclear Research Center. The lithium target, to be bombarded by the high-intensity proton beam of the Soreq Applied Research Accelerator Facility (SARAF), will constitute an intense source of neutrons produced by the (7)Li(p,n)(7)Be reaction for nuclear astrophysics research and as a pilot setup for accelerator-based Boron Neutron Capture Therapy. The liquid-lithium jet target acts both as neutron-producing target and beam dump by removing the beam thermal power (>5 kW, >1 MW/cm(3)) with fast transport. The target was designed based on a thermal model, accompanied by a detailed calculation of the (7)Li(p,n) neutron yield, energy distribution, and angular distribution. Liquid lithium is circulated through the target loop at ~200 °C and generates a stable 1.5 mm-thick film flowing at a velocity up to 7 m/s onto a concave supporting wall. Electron beam irradiation demonstrated that the liquid-lithium target can dissipate electron power areal densities of >4 kW/cm(2) and volume power density of ~2 MW/cm(3) at a lithium flow of ~4 m/s while maintaining stable temperature and vacuum conditions. The LiLiT setup is presently in online commissioning stage for high-intensity proton beam irradiation (1.91-2.5 MeV, 1-2 mA) at SARAF. PMID:24387433

  6. High-power liquid-lithium jet target for neutron production

    NASA Astrophysics Data System (ADS)

    Halfon, S.; Arenshtam, A.; Kijel, D.; Paul, M.; Berkovits, D.; Eliyahu, I.; Feinberg, G.; Friedman, M.; Hazenshprung, N.; Mardor, I.; Nagler, A.; Shimel, G.; Tessler, M.; Silverman, I.

    2013-12-01

    A compact liquid-lithium target (LiLiT) was built and tested with a high-power electron gun at the Soreq Nuclear Research Center. The lithium target, to be bombarded by the high-intensity proton beam of the Soreq Applied Research Accelerator Facility (SARAF), will constitute an intense source of neutrons produced by the 7Li(p,n)7Be reaction for nuclear astrophysics research and as a pilot setup for accelerator-based Boron Neutron Capture Therapy. The liquid-lithium jet target acts both as neutron-producing target and beam dump by removing the beam thermal power (>5 kW, >1 MW/cm3) with fast transport. The target was designed based on a thermal model, accompanied by a detailed calculation of the 7Li(p,n) neutron yield, energy distribution, and angular distribution. Liquid lithium is circulated through the target loop at ˜200 °C and generates a stable 1.5 mm-thick film flowing at a velocity up to 7 m/s onto a concave supporting wall. Electron beam irradiation demonstrated that the liquid-lithium target can dissipate electron power areal densities of >4 kW/cm2 and volume power density of ˜2 MW/cm3 at a lithium flow of ˜4 m/s while maintaining stable temperature and vacuum conditions. The LiLiT setup is presently in online commissioning stage for high-intensity proton beam irradiation (1.91-2.5 MeV, 1-2 mA) at SARAF.

  7. High-power liquid-lithium jet target for neutron production

    SciTech Connect

    Halfon, S.; Feinberg, G.; Arenshtam, A.; Kijel, D.; Berkovits, D.; Eliyahu, I.; Hazenshprung, N.; Mardor, I.; Nagler, A.; Shimel, G.; Silverman, I.; Paul, M.; Friedman, M.; Tessler, M.

    2013-12-15

    A compact liquid-lithium target (LiLiT) was built and tested with a high-power electron gun at the Soreq Nuclear Research Center. The lithium target, to be bombarded by the high-intensity proton beam of the Soreq Applied Research Accelerator Facility (SARAF), will constitute an intense source of neutrons produced by the {sup 7}Li(p,n){sup 7}Be reaction for nuclear astrophysics research and as a pilot setup for accelerator-based Boron Neutron Capture Therapy. The liquid-lithium jet target acts both as neutron-producing target and beam dump by removing the beam thermal power (>5 kW, >1 MW/cm{sup 3}) with fast transport. The target was designed based on a thermal model, accompanied by a detailed calculation of the {sup 7}Li(p,n) neutron yield, energy distribution, and angular distribution. Liquid lithium is circulated through the target loop at ∼200 °C and generates a stable 1.5 mm-thick film flowing at a velocity up to 7 m/s onto a concave supporting wall. Electron beam irradiation demonstrated that the liquid-lithium target can dissipate electron power areal densities of >4 kW/cm{sup 2} and volume power density of ∼2 MW/cm{sup 3} at a lithium flow of ∼4 m/s while maintaining stable temperature and vacuum conditions. The LiLiT setup is presently in online commissioning stage for high-intensity proton beam irradiation (1.91–2.5 MeV, 1–2 mA) at SARAF.

  8. Dynamical properties of non-equilibrium atmospheric plasma jets and their applications to plasma processing in liquids

    NASA Astrophysics Data System (ADS)

    Kitano, Katsuhisa; Satoshi, Ikawa; Furusho, Hitoshi; Nagasaki, Yukio; Hamaguchi, Satoshi

    2007-11-01

    Non-equilibrium atmospheric pressure plasma jets are discussed with the emphasis on their physics and applications. Plume-like plasmas, which may be called plasma jets, have been generated in a discharge system consisting of a dielectric/metal tube (through which He gas flows at the atmospheric pressure) and a single electrode attached to the tube, to which low-frequency, high-voltage pulses (˜10kV, ˜10kHz) are applied. With visible light images taken by a high-speed ICCD camera, it has been confirmed that the plasma jet consists of a series of small ``plasma bullets'' that are emitted intermittently from the powered electrode in sync with the positive voltage pulses. The observed ``plasma bullet'' may be interpreted as a fast moving ionization front. The plasma jets are energetic enough to generate highly reactive charge-neutral radicals but their gas temperatures remain low. Therefore the plasma jets are ideal for processing of liquid based materials at low temperatures and some examples of process applications, such as reduction of cations, polymerization of liquid monomers, and sterilization, will be also presented.

  9. A ballistic compressor-based experiment for the visualization of liquid propellant jet combustion above 100 MPa

    NASA Astrophysics Data System (ADS)

    Birk, A.; Kooker, D. E.

    This paper describes the components and operation of an experimental setup for the visualization of liquid propellant (LP) jet combustion at pressures above 100 MPa. The apparatus consists of an in-line ballistic compressor and LP injector. The ballistic compressor, based on a modified 76 mm gun, provides high-pressure (ca. 55 MPa) clear hot gas for the jet ignition. A piston (projectile) is fired toward a test chamber beyond the barrel's end, and its rebound is arrested in a transition section that seals the test chamber to the barrel. The LP jet is injected once the piston is restrained, and combustion of the jet further elevates the pressure. At a preset pressure, a disc in the piston ruptures and the combustion gas vents sonically into the barrel. If a monopropellant is used, the jet injection-combustion process then resembles liquid rocket combustion but at very high pressures (ca. 140 MPa). This paper discusses the ballistics of the compression and compares experimental results to those predicted by a numerical model of the apparatus. Experimentally, a pressure of 70 MPa was achieved upon a 12.5 volumetric compression factor by firing a 10 kg piston into 1.04 MPa argon using a charge of 75 g of small-grain M1 propellant.

  10. A Water Model Study of Impinging Gas Jets on Liquid Surfaces

    NASA Astrophysics Data System (ADS)

    Hwang, Ho Yong; Irons, Gordon A.

    2012-04-01

    Water modeling experiments were designed to observe the deformation of a liquid surface by impinging the gas jet. Video images were taken and processed in a systematic way. The important surface cavity parameters, such as depth, width, and their frequency of oscillation, were obtained. The relation between surface depression depth and the supplied gas momentum were consistent with previous findings and were extended to higher flow rates. The surface instability and the onset of splashing were observed and interpreted with the Blowing number. The wave behaviors were described qualitatively with a combination of photographic evidence and power spectral density analysis to extract the characteristic wave numbers for each gas flow rate. The analysis of the time series of the surface variables showed a connection to the attenuation of turbulence gas pressure fluctuation and the surface deformation by the gas impingement. Bath velocities were measured with a particle image velocimetry (PIV) technique. To quantify the transfer of kinetic energy from the gas to the liquid, an energy transfer index was defined and calculated with the PIV data. The index was insensitive to gas flow rate but increased with cavity width. The momentum transfer across the interface was also analyzed, and a similar cavity width dependence was found. A correlation between the cavity shape and momentum transfer was proposed.

  11. Non-thermal processes on ice and liquid micro-jet surfaces

    NASA Astrophysics Data System (ADS)

    Olanrewaju, Babajide O.

    The primary focus of this research is to investigate non-thermal processes occurring on ice surfaces and the photo-ejection of ions from liquid surfaces. Processes at the air-water/ice interface are known to play a very important role in the release of reactive halogen species with atmospheric aerosols serving as catalysts. The ability to make different types of ice with various morphologies, hence, different adsorption and surface properties in vacuum, provide a useful way to probe the catalytic effect of ice in atmospheric reactions. Also, the use of the liquid jet technique provides the rare opportunity to probe liquid samples at the interface; hitherto impossible to investigate with traditional surface science techniques. In Chapter 2, the effect of ice morphology on the release of reactive halogen species from photodissociation of adsorbed organic halides on ice will be presented. Quantum state resolved measurements of neutral atomic iodine from the photon irradiation of submonolayer coverages of methyl iodide adsorbed on low temperature water ice were conducted. Temperature programmed desorption (TPD) studies of methyl iodide adsorbed on ice were performed to provide information on the effect of ice morphology on the adsorption of submonolayer methyl iodide. The interaction and autoionization of HCl on low-temperature (80{140 K) water ice surfaces has been studied using low-energy (5-250 eV) electron-stimulated desorption (ESD) and temperature programmed desorption (TPD). A detailed ESD study of the interactions of low concentrations of HCl with low-temperature porous amorphous solid water (PASW), amorphous solid water (ASW) and crystalline ice (CI) surfaces will be presented in Chapter 3. The ESD cation yields from HCl adsorbed on ice, as well as the coverage dependence, kinetic energy distributions and TPD measurements were all monitored. Probing liquid surface using traditional surface science technique is usually difficult because of the problem of

  12. Characterization and Scaling of Vortex Shedding from a Plunging Plate

    NASA Astrophysics Data System (ADS)

    Eslam Panah, Azar; Buchholz, James

    2011-11-01

    Leading-edge and trailing-edge vortices (LEV and TEV) are investigated for a plunging flat plate airfoil at a chord Reynolds number of 10,000 while varying plunge amplitude and Strouhal number. Digital Particle Image Velocimetry is used to examine the strength and dynamics of shed vortices. Vortex strength, timing, pinch-off and trajectory are examined. By tracking the development of both the LEV and TEV in phase-locked measurements throughout the cycle and extracting the respective vortex circulation, the dimensionless circulation of both the LEV and TEV at each phase in the cycle could be determined. Guided by theoretical considerations for vorticity generation and aerodynamic theory, we will discuss the role of kinematic parameters on vortex shedding and the applicability of a scaling factor for the circulation of the shed vortex structures. Whereas a scaling parameter based on plate kinematics effectively collapses the circulation values of the shed leading-edge vortices with variation in Strouhal number, plunge amplitude, and angle of attack, it is found that the strength of the trailing-edge structures vary little with variation in plunge amplitude and angle of attack. This work is supported by AFOSR under award number FA9550-11-1-0019 monitored by Dr. Doug Smith.

  13. Experimental observations of the breakup of multiple metal jets in a volatile liquid

    SciTech Connect

    Marciniak, M.J.

    1995-07-01

    A postulated severe loss of coolant accident in a nuclear reactor can lead to significant core damage due to residual heat generation. Subsequently, melted core materials (i.e.; corium) could migrate downward and impinge upon the lower head of the reactor pressure vessel (RPV). During this relocation, the complexity of the reactor structure could segregate the molten corium into various flow paths. A perforated flow plate could readily provide the mechanism to segregate the molten corium. The resulting small (a few cm) diameter melt streams, driven by gravity, could then penetrate the remaining coolant in the RPV and cause any of the following events: impingement of the high temperature melt streams on the lower head could breach the RPV; re-agglomeration of the corium melt on the lower head could influence the coolability of the debris bed; {open_quotes}pre-mixing{close_quotes} of the melt streams with the coolant could lead to a vapor explosion; or, sufficient quenching of the melt streams by the coolant could produce a stabilized debris bed. An overview of the thermo-science issues related to core-melt accidents is presented by Theofanous. Thus, insight into the melt stream breakup mechanisms (i.e.; interfacial conditions, fragmentation, and geometric spacing) during the melt-coolant interactions is necessary to evaluate the plausibility, and characteristics, of these events. Molten Fuel Stream Breakup Simulation (MFSBS) experiments have been performed at Argonne National Laboratory in which simulant materials were used to determine a `boiling` jet breakup length correlation and to visualize the melt fragmentation mechanisms during the penetration of a single molten metal jet into a volatile liquid. The goal was to characterize the hydrodynamics of the corium-water interactions in a postulated core melt accident. The present experiment closely follows the procedures of the MFSBS.

  14. Multi-fluid Dynamics for Supersonic Jet-and-Crossflows and Liquid Plug Rupture

    NASA Astrophysics Data System (ADS)

    Hassan, Ezeldin A.

    Multi-fluid dynamics simulations require appropriate numerical treatments based on the main flow characteristics, such as flow speed, turbulence, thermodynamic state, and time and length scales. In this thesis, two distinct problems are investigated: supersonic jet and crossflow interactions; and liquid plug propagation and rupture in an airway. Gaseous non-reactive ethylene jet and air crossflow simulation represents essential physics for fuel injection in SCRAMJET engines. The regime is highly unsteady, involving shocks, turbulent mixing, and large-scale vortical structures. An eddy-viscosity-based multi-scale turbulence model is proposed to resolve turbulent structures consistent with grid resolution and turbulence length scales. Predictions of the time-averaged fuel concentration from the multi-scale model is improved over Reynolds-averaged Navier-Stokes models originally derived from stationary flow. The response to the multi-scale model alone is, however, limited, in cases where the vortical structures are small and scattered thus requiring prohibitively expensive grids in order to resolve the flow field accurately. Statistical information related to turbulent fluctuations is utilized to estimate an effective turbulent Schmidt number, which is shown to be highly varying in space. Accordingly, an adaptive turbulent Schmidt number approach is proposed, by allowing the resolved field to adaptively influence the value of turbulent Schmidt number in the multi-scale turbulence model. The proposed model estimates a time-averaged turbulent Schmidt number adapted to the computed flowfield, instead of the constant value common to the eddy-viscosity-based Navier-Stokes models. This approach is assessed using a grid-refinement study for the normal injection case, and tested with 30 degree injection, showing improved results over the constant turbulent Schmidt model both in mean and variance of fuel concentration predictions. For the incompressible liquid plug propagation

  15. A closed-loop pump-driven wire-guided flow jet for ultrafast spectroscopy of liquid samples.

    PubMed

    Picchiotti, Alessandra; Prokhorenko, Valentyn I; Miller, R J Dwayne

    2015-09-01

    We describe the design and provide the results of the full characterization of a closed-loop pump-driven wire-guided flow jet system. The jet has excellent optical quality with a wide range of liquids spanning from alcohol to water based solutions, including phosphate buffers used for biological samples. The thickness of the jet film varies depending on the flow rate between 90 μm and 370 μm. The liquid film is very stable, and its thickness varies only by 0.76% under optimal conditions. Measured transmitted signal reveals a long term optical stability (hours) with a RMS of 0.8%, less than the overall noise of the spectroscopy setup used in our experiments. The closed loop nature of the overall jet design has been optimized for the study of precious biological samples, in limited volumes, to remove window contributions from spectroscopic observables. This feature is particularly important for femtosecond studies in the UV range. PMID:26429427

  16. Effects of gas flow on oxidation reaction in liquid induced by He/O{sub 2} plasma-jet irradiation

    SciTech Connect

    Nakajima, Atsushi; Uchida, Giichiro Takenaka, Kosuke; Setsuhara, Yuichi; Kawasaki, Toshiyuki; Koga, Kazunori; Sarinont, Thapanut; Amano, Takaaki; Shiratani, Masaharu

    2015-07-28

    We present here analysis of oxidation reaction in liquid by a plasma-jet irradiation under various gas flow patterns such as laminar and turbulence flows. To estimate the total amount of oxidation reaction induced by reactive oxygen species (ROS) in liquid, we employ a KI-starch solution system, where the absorbance of the KI-starch solution near 600 nm behaves linear to the total amount of oxidation reaction in liquid. The laminar flow with higher gas velocity induces an increase in the ROS distribution area on the liquid surface, which results in a large amount of oxidation reaction in liquid. However, a much faster gas flow conversely results in a reduction in the total amount of oxidation reaction in liquid under the following two conditions: first condition is that the turbulence flow is triggered in a gas flow channel at a high Reynolds number of gas flow, which leads to a marked change of the spatial distribution of the ROS concentration in gas phase. Second condition is that the dimpled liquid surface is formed by strong gas flow, which prevents the ROS from being transported in radial direction along the liquid surface.

  17. Effects of gas flow on oxidation reaction in liquid induced by He/O2 plasma-jet irradiation

    NASA Astrophysics Data System (ADS)

    Nakajima, Atsushi; Uchida, Giichiro; Kawasaki, Toshiyuki; Koga, Kazunori; Sarinont, Thapanut; Amano, Takaaki; Takenaka, Kosuke; Shiratani, Masaharu; Setsuhara, Yuichi

    2015-07-01

    We present here analysis of oxidation reaction in liquid by a plasma-jet irradiation under various gas flow patterns such as laminar and turbulence flows. To estimate the total amount of oxidation reaction induced by reactive oxygen species (ROS) in liquid, we employ a KI-starch solution system, where the absorbance of the KI-starch solution near 600 nm behaves linear to the total amount of oxidation reaction in liquid. The laminar flow with higher gas velocity induces an increase in the ROS distribution area on the liquid surface, which results in a large amount of oxidation reaction in liquid. However, a much faster gas flow conversely results in a reduction in the total amount of oxidation reaction in liquid under the following two conditions: first condition is that the turbulence flow is triggered in a gas flow channel at a high Reynolds number of gas flow, which leads to a marked change of the spatial distribution of the ROS concentration in gas phase. Second condition is that the dimpled liquid surface is formed by strong gas flow, which prevents the ROS from being transported in radial direction along the liquid surface.

  18. Image analysis of jet structure on electrospinning from free liquid surface

    SciTech Connect

    Kula, Jiri Linka, Ales Tunak, Maros; Lukas, David

    2014-06-16

    The work analyses intra-jet distances during electrospinning from a free surface of water based poly(vinyl alcohol) solution confined by two thin metallic plates employed as a spinning electrode. A unique computer vision system and digital image processing were designed in order to track position of every polymer jet. Here, we show that jet position data are in good compliance with theoretically predicted intra-jet distances by linear stability analysis. Jet density is a critical parameter of electrospinning technology, since it determines the process efficiency and homogeneity of produced nanofibrous layer. Achievements made in this research could be used as essential approach to study jetting from two-dimensional spinning electrodes, or as fundamentals for further development of control system related to Nanospider{sup ™} technology.

  19. Underlying principle of efficient propulsion in flexible plunging foils

    NASA Astrophysics Data System (ADS)

    Zhu, Xiao-Jue; He, Guo-Wei; Zhang, Xing

    2014-12-01

    Passive flexibility was found to enhance propulsive efficiency in swimming animals. In this study, we numerically investigate the roles of structural resonance and hydrodynamic wake resonance in optimizing efficiency of a flexible plunging foil. The results indicates that (1) optimal efficiency is not necessarily achieved when the driving frequency matches the structural eigenfrequency; (2) optimal efficiency always occurs when the driving frequency matches the wake resonant frequency of the time averaged velocity profile. Thus, the underlying principle of efficient propulsion in flexible plunging foil is the hydrodynamic wake resonance, rather than the structural resonance. In addition, we also found that whether the efficiency can be optimized at the structural resonant point depends on the strength of the leading edge vortex relative to that of the trailing edge vortex. The result of this work provides new insights into the role of passive flexibility in flapping-based propulsion.

  20. Computer simulation of mobilization and mixing of kaolin with submerged liquid jets in 25,000-gallon horizontal cylindrical tanks

    SciTech Connect

    Eyler, L.L.; Mahoney, L.A.

    1995-03-01

    This report presents and analyzes results of computer model simulation of mobilization and mixing of kaolin using the TEMPEST code. The simulations are conducted in a horizontal cylindrical geometry replicating a 95 m{sup 3} (25,000 gal) test tank at ORNL, which is scaled to approximate Melton Valley Storage tanks, which are 190 m{sup 3} (50,000 gal). Mobilization and mixing is accomplished by two submerged liquid jets. Two configurations are simulated, one with the jets located at the center of the tank lengthwise and one with the jets located 1/4 tank length from one end. Computer simulations of both jet and suction configurations are performed. Total flow rates of 50, 100, and 200 gpm are modeled, corresponding to jet velocities of 1.52, 3.05, 6.10 m/s (5, 10, 20 ft/s). Calculations were performed to a time of 2 h for the center jet location and to a little over 1 h for the quarter jet location. This report presents computer and fluid properties model basis, preliminary numerical testing, and results. The results are presented in form of flow field and sludge layer contours. Degree of mobilization is presented as fraction of initial sludge layer remaining as a function of time. For the center jet location at 200 gpm, the sludge layer is completely mobilized in just over 1 h. For 100 gpm flow, about 5% of the sludge layer remains after 2 h. For 50 gpm flow, nearly 40% of the initial sludge layer remains after 2 h. For the quarter jets at 200 gpm, about 10% of the initial sludge layer remains after 1 h. For 100 gpm, about 40% of the sludge layer remains after 1 h. The boundary of the sludge layer is defined as 98% max packing for the particles. Mixing time estimates for these cases range from between 9.4 h and 16.2 h. A more critical evaluation and comparison of predictions and the test results is needed.

  1. Modeling Single-Phase and Boiling Liquid Jet Impingement Cooling in Power Electronics

    SciTech Connect

    Narumanchi, S. V. J.; Hassani, V.; Bharathan, D.

    2005-12-01

    Jet impingement has been an attractive cooling option in a number of industries over the past few decades. Over the past 15 years, jet impingement has been explored as a cooling option in microelectronics. Recently, interest has been expressed by the automotive industry in exploring jet impingement for cooling power electronics components. This technical report explores, from a modeling perspective, both single-phase and boiling jet impingement cooling in power electronics, primarily from a heat transfer viewpoint. The discussion is from the viewpoint of the cooling of IGBTs (insulated-gate bipolar transistors), which are found in hybrid automobile inverters.

  2. Transitions in the vortex wake behind the plunging profile

    NASA Astrophysics Data System (ADS)

    Kozłowski, Tomasz; Kudela, Henryk

    2014-12-01

    In this study we investigate numerically the vortex wake formation behind the profile performing simple harmonic motion known in the literature as plunging. This research was inspired by the flapping motion which is appropriate for birds, insects and fishes. We assume the two dimensional model of flow. Depending on the parameters such as plunging amplitude, frequency and the Reynolds number, we demonstrate many different types of vortex street behind the profile. It is well known that the type of vortex wake determines the hydrodynamic forces acting on the profile. Dependences of the plunging amplitude, the Strouhal number and various topology vortices are established by constructing the phase transition diagram. The areas in the diagram related to the drag, thrust, and lift force generation are captured. We notice also the areas where the vorticity field is disordered. The disordered vorticity field does not allow maintenance of the periodic forces on the profile. An increase in the Reynolds number leads to the transition of the vortex wake behind the profile. The transition is caused by the phenomenon of boundary layer eruption. Further increase of the Reynolds number causes the vortex street related to the generation of the lift force to vanish.

  3. Splash jet and slamming generated by a rotating flap

    NASA Astrophysics Data System (ADS)

    Sun, S. Y.; Sun, S. L.; Ren, H. L.; Wu, G. X.

    2015-09-01

    The hydrodynamic problem of slamming generated by a rotating flap, commonly known as Oyster in the wave energy sector, plunging into water, is analysed based on the incompressible velocity potential theory. The problem is solved through the boundary element method in the time domain. Two typical case studies are undertaken. One is the flap plunging into calm water and the other into an incoming wave. The splash jet formed during the flap plunging is included in the simulation. When the jet meets the main flow, it is treated through the domain decomposition method without taking account the secondary impact, which is similar to the mathematical method of Riemann's second sheet in the complex plane. The problem is solved in each non-overlapping subdomain, and the velocity and pressure continuity condition is imposed on the interface of the subdomains. Detailed results for the flap plunging into water with different velocities or accelerations are provided. The gravity and wave effects are also investigated.

  4. Application of Proper Orthogonal Decomposition to the morphological analysis of confined co-axial jets of immiscible liquids with comparable densities

    NASA Astrophysics Data System (ADS)

    Charalampous, Georgios; Hardalupas, Yannis

    2014-11-01

    The development of a round liquid jet under the influence of a confined coaxial flow of an immiscible liquid of comparable density (central to annular flow density ratio of 8:10) was investigated in the vicinity of the nozzle exit. Two flow regimes were considered; one where the annular flow is faster than the central jet, so the central liquid jet is accelerated and one where the annular flow is slower, so the central liquid jet is decelerated. The central jet was visualised by high speed photography. Three modes of jet development were identified and classified in terms of the Reynolds number, Re, of the central jet which was in the range of 525 < Re < 2725, a modified definition of the Weber number, We, which allows the distinction between accelerating and deceleration flows and was in the range of -22 < We < 67 and the annular to central Momentum Ratio, MR, of the two streams which was in the range of 3.6 < MR < 91. By processing the time resolved jet images using Proper Orthogonal Decomposition (POD), it was possible to reduce the description of jet morphology to a small number of spatial modes, which isolated the most significant morphologies of the jet development. In this way, the temporal and spatial characteristics of the instabilities on the interface were clearly identified which highlights the advantages of POD over direct observation of the images. Relationships between the flow parameters and the interfacial waves were established. The wavelength of the interfacial instability was found to depend on the velocity of the fastest moving stream, which is contrary to findings for fluids with large density differences.

  5. Effects of irradiation distance on supply of reactive oxygen species to the bottom of a Petri dish filled with liquid by an atmospheric O2/He plasma jet

    NASA Astrophysics Data System (ADS)

    Kawasaki, Toshiyuki; Kusumegi, Shota; Kudo, Akihiro; Sakanoshita, Tomohiro; Tsurumaru, Takuya; Sato, Akihiro; Uchida, Giichiro; Koga, Kazunori; Shiratani, Masaharu

    2016-05-01

    The impact of irradiation distances on plasma jet-induced specific effects on the supply of reactive oxygen species (ROS) to the bottom of a Petri dish filled with liquid was investigated using a KI-starch gel reagent that can be employed as a ROS indicator even in water. O3 exposure experiments without plasma irradiation were also performed to elucidate the specific effects of the plasma jet. Relative concentrations of ROS transported to the bottom were evaluated using absorbance measurements. The results indicated that ROS supply to the bottom is markedly enhanced by the plasma jet irradiation at shorter irradiation distances, whereas similar results could not be obtained for the O3 exposure. In these cases, the liquid mixing in the depth direction was also enhanced by the plasma jet irradiation only, and the supply of reactive atomic oxygen to the liquid surface was markedly increased as well.

  6. Breakup of metal jets penetrating a volatile liquid. Final report, October 1, 1991--February 28, 1993

    SciTech Connect

    Schneider, J.P.

    1995-07-01

    In a loss of coolant accident, the core may become uncovered, causing the fuel pins to melt. The molten fuel would pour onto the plenum and collect on the reactor pressure vessel (RPV) lower head. The RPV internal structure includes one or more perforated plates in the lower plenum which would divide the molten fuel into small diameter streams or jets, which would break up as they penetrate the coolant in the lower plenum. The breakup of these jets would occur in two phases, each dominated by a distinct fragmentation mechanism. As a fuel jet first penetrates the coolant, a stagnation flow develops at its leading edge, causing the column to spread radially and eject molten fuel into the coolant. The jet fluid in the column is fragmented by pressure fluctuations due to the jet/ambient fluid relative motion, so that a steady jet is reduced to a field of falling drops below a critical depth called the breakup length. The present work includes analyses yielding simple correlations for jet breakup length and jet leading edge penetration.

  7. One-dimensional nonlinear instability study of a slightly viscoelastic, perfectly conducting liquid jet under a radial electric field

    NASA Astrophysics Data System (ADS)

    Li, Fang; Yin, Xie-Yuan; Yin, Xie-Zhen

    2016-05-01

    A one-dimensional electrified viscoelastic model is built to study the nonlinear behavior of a slightly viscoelastic, perfectly conducting liquid jet under a radial electric field. The equations are solved numerically using an implicit finite difference scheme together with a boundary element method. The electrified viscoelastic jet is found to evolve into a beads-on-string structure in the presence of the radial electric field. Although the radial electric field greatly enhances the linear instability of the jet, its influence on the decay of the filament thickness is limited during the nonlinear evolution of the jet. On the other hand, the radial electric field induces axial non-uniformity of the first normal stress difference within the filament. The first normal stress difference in the center region of the filament may be greatly decreased by the radial electric field. The regions with/without satellite droplets are illuminated on the χ (the electrical Bond number)-k (the dimensionless wave number) plane. Satellite droplets may be formed for larger wave numbers at larger radial electric fields.

  8. Fluid dynamics and convective heat transfer in impinging jets through implementation of a high resolution liquid crystal technique

    NASA Technical Reports Server (NTRS)

    Kim, K.; Wiedner, B.; Camci, C.

    1993-01-01

    A combined convective heat transfer and fluid dynamics investigation in a turbulent round jet impinging on a flat surface is presented. The experimental study uses a high resolution liquid crystal technique for the determination of the convective heat transfer coefficients on the impingement plate. The heat transfer experiments are performed using a transient heat transfer method. The mean flow and the character of turbulent flow in the free jet is presented through five hole probe and hot wire measurements, respectively. The flow field character of the region near the impingement plate plays an important role in the amount of convective heat transfer. Detailed surveys obtained from five hole probe and hot wire measurements are provided. An extensive validation of the liquid crystal based heat transfer method against a conventional technique is also presented. After a complete documentation of the mean and turbulent flow field, the convective heat transfer coefficient distributions on the impingement plate are presented. The near wall of the impingement plate and the free jet region is treated separately. The current heat transfer distributions are compared to other studies available from the literature. The present paper contains complete sets of information on the three dimensional mean flow, turbulent velocity fluctuations, and convective heat transfer to the plate. The experiments also prove that the present nonintrusive heat transfer method is highly effective in obtaining high resolution heat transfer maps with a heat transfer coefficient uncertainty of 5.7 percent.

  9. Visco Jet Joule-Thomson Device Characterization Tests in Liquid Methane

    NASA Technical Reports Server (NTRS)

    Jurns, John M.

    2009-01-01

    Joule-Thomson (J-T) devices have been identified as critical components for Thermodynamic Vent Systems (TVS) planned for future space exploration missions. Lee Visco Jets (The Lee Company) (Ref. 4) are one type of J-T device that may be used for LCH4 propellant systems. Visco Jets have been previously tested and characterized in LN2 and LH2 (Refs. 6 and 7), but have not been characterized in LOX or LCH4. Previous Visco Jet tests with LH2 resulted in clogging of the Visco Jet orifice under certain conditions. It has been postulated that this clogging was due to the presence of neon impurities in the LH2 that solidified in the orifices. Visco Jets therefore require testing in LCH4 to verify that they will not clog under normal operating conditions. This report describes a series of tests that were performed at the NASA Glenn Research Center to determine if Visco Jets would clog under normal operating conditions with LCH4 propellant. Test results from this program indicate that no decrease in flow rate was observed for the Visco Jets tested, and that current equation used for predicting flow rate appears to under-predict actual flow at high Lohm ratings.

  10. Characterization of extreme ultraviolet light-emitting plasmas from a laser-excited fluorine containing liquid polymer jet target

    NASA Astrophysics Data System (ADS)

    Abel, B.; Assmann, J.; Faubel, M.; Gäbel, K.; Kranzusch, S.; Lugovoj, E.; Mann, K.; Missalla, T.; Peth, Ch.

    2004-06-01

    The operation of a liquid polymer jet laser-plasma target and the characterization of the absolute x-ray emission in the extreme ultraviolet wavelength window from 9-19 nm is reported. The target is a liquid polymer (perfluoro-polyether) that is exposed to pulsed and focused laser light at 532 nm in the form of a thin, liquid microjet (d=40 to 160 μm) in vacuum. The spectral brightness of the source in the 13 nm range is relatively high because a large fraction of radiative energy is emitted in one single line only, which is assigned to be the 2p-3d FVII doublet at 12.8 nm, with a laser energy conversion efficiency of 0.45% (2π sr, 2% bandwidth) in our initial experiment. A further increase of the relative emission has been found in the wavelength range between 7 and 17 nm when the jet diameter was increased from 40 to 160 μm. The two-dimensional spatial profile of the source plasma (d=40 to 50 μm) has been analyzed with a pinhole camera.

  11. Condensation enhancement on a pool surface caused by a submerged liquid jet

    SciTech Connect

    Shumway, R.W.

    1997-05-01

    One advanced nuclear reactor design has a residual heat removal (RHR) pipe connected to the bottom of a steam generator outlet plenum. The water in the plenum can become thermally stratified during postulated loss of coolant accidents. Cold water injected through the RHR pipe has the potential effect of increasing the steam condensation on the pool surface due to the stirring action of the jet. The amount of increase depends on a number of factors, including the jet velocity and the pool height above the jet injection point. Prediction of steam condensation rates, before and after the jet breaks the pool surface, is the topic of this paper. Data and correlations exist for pre surface breakthrough and a method has been developed for post breakthrough. The models have been incorporated into the reactor safety analysis computer software known as RELAP5. Comparisons of predictions against data are presented.

  12. Advanced Liquid Cooling for a Traction Drive Inverter Using Jet Impingement and Microfinned Enhanced Surfaces: Preprint

    SciTech Connect

    Waye, S. K.; Narumanchi, S.; Mihalic, M.; Moreno, G.; Bennion, K.; Jeffers, J.

    2014-08-01

    Jet impingement on plain and micro-finned enhanced surfaces was compared to a traditional channel flow configuration. The jets provide localized cooling to areas heated by the insulated-gate bipolar transistor and diode devices. Enhanced microfinned surfaces increase surface area and thermal performance. Using lighter materials and designing the fluid path to manage pressure losses increases overall performance while reducing weight, volume, and cost. Powering four diodes in the center power module of the inverter and computational fluid dynamics (CFD) modeling was used to characterize the baseline as well as jet-impingement-based heat exchangers. CFD modeling showed the thermal performance improvements should hold for a fully powered inverter. Increased thermal performance was observed for the jet-impingement configurations when tested at full inverter power (40 to 100 kW output power) on a dynamometer. The reliability of the jets and enhanced surfaces over time was also investigated. Experimentally, the junction-to- coolant thermal resistance was reduced by up to 12.5% for jet impingement on enhanced surfaces s compared to the baseline channel flow configuration. Base plate-to-coolant (convective) resistance was reduced by up to 37.0% for the jet-based configuration compared to the baseline, suggesting that while improvements to the cooling side reduce overall resistance, reducing the passive stack resistance may contribute to lowering overall junction-to-coolant resistance. Full inverter power testing showed reduced thermal resistance from the middle of the module baseplate to coolant of up to 16.5%. Between the improvement in thermal performance and pumping power, the coefficient of performance improved by up to 13% for the jet-based configuration.

  13. A study of liquid boric oxide particle growth rates in a gas stream from a simulated jet engine combustor

    NASA Technical Reports Server (NTRS)

    Setze, Paul C

    1957-01-01

    It was experimentally determined that the liquid boric oxide particles leaving a jet engine combustor, burning a boron-containing fuel, will have diameters of 1.0 x 10(exp -5) to 2.0 x 10(exp -5) centimeter. For this size range the particle heat-transfer and drag coefficients are essentially infinite. The results may be applied to any boron-containing fuel. Equations are developed that enable the calculation of the particle size-time history. A study of boric oxide deposition mechanisms is included, and suggestions for decreading deposition rates given.

  14. Flow structure and vorticity transport on a plunging wing

    NASA Astrophysics Data System (ADS)

    Eslam Panah, Azar

    The structure and dynamics of the flow field created by a plunging flat plate airfoil are investigated at a chord Reynolds number of 10,000 while varying plunge amplitude and Strouhal number. Digital particle image velocimetry measurements are used to characterize the shedding patterns and the interactions between the leading and trailing edge vortex structures (LEV and TEV), resulting in the development of a wake classification system based on the nature and timing of interactions between the leading- and trailing-edge vortices. The convection speed of the LEV and its resulting interaction with the TEV is primarily dependent on reduced frequency; however, at Strouhal numbers above approximately 0.4, a significant influence of Strouhal number (or plunge amplitude) is observed in which LEV convection is retarded, and the contribution of the LEV to the wake is diminished. It is shown that this effect is caused by an enhanced interaction between the LEV and the airfoil surface, due to a significant increase in the strength of the vortices in this Strouhal number range, for all plunge amplitudes investigated. Comparison with low-Reynolds-number studies of plunging airfoil aerodynamics reveals a high degree of consistency and suggests applicability of the classification system beyond the range examined in the present work. Some important differences are also observed. The three-dimensional flow field was characterized for a plunging two-dimensional flat-plate airfoil using three-dimensional reconstructions of planar PIV data. Whereas the phase-averaged description of the flow field shows the secondary vortex penetrating the leading-edge shear layer to terminate LEV formation on the airfoil, time-resolved, instantaneous PIV measurements show a continuous and growing entrainment of secondary vorticity into the shear layer and LEV. A planar control volume analysis on the airfoil indicated that the generation of secondary vorticity produced approximately one half the

  15. Experimental investigation of 2D flexible plunging hydrofoil

    NASA Astrophysics Data System (ADS)

    Tian, Ruijun; Mitchell, Robert; Shu, Fangjun

    2012-11-01

    It is believed that both birds and insects benefit from their wing flexibility during the flapping flight. One of the possible benefits is higher lift force generation capability than that of rigid wing models. Both experimental and computational work has discovered that the leading edge vortex (LEV) plays an important role in this advantage of high lift force generating efficiency. In the present work, flow physics related to high lift-generating flexible wings are investigated experimentally. Both flexible and rigid hydrofoils (NACA0012) were actively plunged in glycerol-water solution with various amplitude, frequency and Reynolds number combinations. Phase-locked Particle Image Velocimetry (PIV) measurements were conducted to investigate the generation and evolution of the LEVs. Lift and drag forces during plunging were also measured to uncover the relationship between the force response and the surrounding flow field development. The overall results were also compared between flexible and rigid hydrofoils to provide qualitative data for validation of computational work. Supported by Army High Performance Computing Center.

  16. Lagrangian observations of acceleration and bubble dynamics in plunging breakers

    NASA Astrophysics Data System (ADS)

    Canals, Miguel; Amador, Andre

    2012-11-01

    Understanding the three-dimensional structure of plunging waves is one of the most difficult problems in fundamental fluid dynamics. In this presentation we provide an analysis of field data collected in breaking waves using novel Lagrangian drifters with a diameter of 5-10 cm and equipped with miniature HD cameras and inertial measurement units. These drifters were deployed, using a personal watercraft, into the breaking region of waves ranging from 1-5 meters in height. We analyze in detail the time series of particle acceleration and rotation and how these quantities relate to the imagery captured by the camera aboard the drifters. This data represents the first dedicated study of the three-dimensional particle dynamics of plunging breakers. Going beyond the basic statistical analysis of the acceleration data, we make an attempt at characterizing the intensity of the wave breaking process using the bubble size and characteristics obtained from the HD video images. We also attempt to relate the spectral statistics of acceleration and particle rotation to existing Lagrangian turbulence models in the hopes of obtaining estimates of the kinetic energy dissipation in breaking waves, while taking into account the unsteady and heterogeneous nature of the turbulent flow.

  17. Generation of capillary instabilities by external disturbances in a liquid jet. Ph.D. Thesis - State Univ. of N.Y.

    NASA Technical Reports Server (NTRS)

    Leib, S. J.

    1985-01-01

    The receptivity problem in a circular liquid jet is considered. A time harmonic axial pressure gradient is imposed on the steady, parallel flow of a jet of liquid emerging from a circular duct. Using a technique developed in plasma physics a casual solution to the forced problem is obtained over certain ranges of Weber number for a number of mean velocity profiles. This solution contains a term which grows exponentially in the downstream direction and can be identified with a capillary instability wave. Hence, it is found that the externally imposed disturbances can indeed trigger instability waves in a liquid jet. The amplitude of the instability wave generated relative to the amplitude of the forcing is computed numerically for a number of cases.

  18. Unconditional jetting.

    PubMed

    Gañán-Calvo, Alfonso M

    2008-08-01

    Capillary jetting of a fluid dispersed into another immiscible phase is usually limited by a critical capillary number, a function of the Reynolds number and the fluid property ratios. Critical conditions are set when the minimum spreading velocity of small perturbations v_{-};{*} along the jet (marginal stability velocity) is zero. Here we identify and describe parametric regions of high technological relevance, where v_{-};{*}>0 and the jet flow is always supercritical independently of the dispersed liquid flow rate; within these relatively broad regions, the jet does not undergo the usual dripping-jetting transition, so that either the jet can be made arbitrarily thin (yielding droplets of any imaginably small size), or the issuing flow rate can be made arbitrarily small. In this work, we provide illustrative analytical studies of asymptotic cases for both negligible and dominant inertia forces. In this latter case, requiring a nonzero jet surface velocity, axisymmetric perturbation waves "surf" downstream for all given wave numbers, while the liquid bulk can remain static. In the former case (implying small Reynolds flow) we found that the jet profile small slope is limited by a critical value; different published experiments support our predictions. PMID:18850933

  19. Similarity between the primary and secondary air-assisted liquid jet breakup mechanisms.

    PubMed

    Wang, Yujie; Im, Kyoung-Su; Fezzaa, Kamel

    2008-04-18

    We report an ultrafast synchrotron x-ray phase-contrast imaging study of the primary breakup mechanism of a coaxial air-assisted water jet. There exist great similarities between the primary (jet) and the secondary (drop) breakup, and in the primary breakup on different length scales. A transition from a ligament- to a membrane-mediated breakup is identified around an effective Weber number We' approximately 13. This observation reveals the critical role an effective Weber number plays in determining the atomization process and strongly supports the cascade breakup model. PMID:18518113

  20. Stretched Inertial Jets

    NASA Astrophysics Data System (ADS)

    Ghabache, Elisabeth; Antkowiak, Arnaud; Seon, Thomas; Villermaux, Emmanuel

    2015-11-01

    Liquid jets often arise as short-lived bursting liquid flows. Cavitation or impact-driven jets, bursting champagne bubbles, shaped-charge jets, ballistospores or drop-on-demand inkjet printing are a few examples where liquid jets are suddenly released. The trademark of all these discharge jets is the property of being stretched, due to the quenching injection. the present theoretical and experimental investigation, the structure of the jet flow field will be unraveled experimentally for a few emblematic occurrences of discharge jets. Though the injection markedly depends on each flow configuration, the jet velocity field will be shown to be systematically and rapidly attracted to the universal stretching flow z/t. The emergence of this inertial attractor actually only relies on simple kinematic ingredients, and as such is fairly generic. The universality of the jet velocity structure will be discussed.

  1. Evaluation of fatty acid oxidation by reactive oxygen species induced in liquids using atmospheric-pressure nonthermal plasma jets

    NASA Astrophysics Data System (ADS)

    Tani, Atsushi; Fukui, Satoshi; Ikawa, Satoshi; Kitano, Katsuhisa

    2015-10-01

    We investigated fatty acid oxidation by atmospheric-pressure nonthermal helium plasma using linoleic acid, an unsaturated fatty acid, together with evaluating active species induced in liquids. If the ambient gas contains oxygen, direct plasma such as plasma jets coming into contact with the liquid surface supplies various active species, such as singlet oxygen, ozone, and superoxide anion radicals, to the liquid. The direct plasma easily oxidizes linoleic acid, indicating that fatty acid oxidation will occur in the direct plasma. In contrast, afterglow flow, where the plasma is terminated in a glass tube and does not touch the surface of the liquid sample, supplies mainly superoxide anion radicals. The fact that there was no clear observation of linoleic acid oxidation using the afterglow reveals that it may not affect lipids, even in an atmosphere containing oxygen. The afterglow flow can potentially be used for the sterilization of aqueous solutions using the reduced pH method, in medical and dental applications, because it provides bactericidal activity in the aqueous solution despite containing a smaller amount of active species.

  2. Liquid Fuel Emulsion Jet-in-Crossflow Penetration and Dispersion Under High Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Gomez, Guillermo Andres

    The current work focuses on the jet-in-crossflow penetration and dispersion behavior of water-in-oil emulsions in a high pressure environment. Both fuel injection strategies of using a water-in-oil emulsion and a jet-in-crossflow have demonstrated unique benefits in improving gas turbine performance from an emissions and efficiency standpoint. A jet-in-crossflow is very practical for use in gas turbine engines, rocket propulsion, and aircraft engines since it utilizes already available crossflow air to atomize fuel. Injecting water into a combustion chamber in the form of a water-in-oil emulsion allows for pollutant emissions reduction while reducing efficiency loses that may result from using a separate water or steam injection circuit. Dispersion effects on oil droplets are expected, therefore investigating the distribution of both oil and water droplets in the crossflow is an objective in this work. Understanding the synchronization and injection behavior of the two strategies is of key interest due to their combined benefits. A water-to-oil ratio and an ambient pressure parameter are developed for emulsion jet-in-crossflow trajectories. To this end, a total of 24 emulsion jet-in-crossflow tests were performed with varying ambient pressures of 2-8 atm and momentum flux ratios of 50, 85, and 120. Sobel edge filtering was applied to each averaged image obtained from a high speed video of each test case. Averaged and filtered images were used to resolve top and bottom edges of the trajectory in addition to the overall peak intensity up to 40 mm downstream of the injection point. An optimized correlation was established and found to differ from literature based correlations obtained under atmospheric pressure conditions. Overall it was found that additional parameters were not necessary for the top edge and peak intensity correlations, but a need for a unique emulsion bottom edge and width trajectory correlation was recognized. In addition to investigating emulsion

  3. Effects of the electrical parameters and gas flow rate on the generation of reactive species in liquids exposed to atmospheric pressure plasma jets

    NASA Astrophysics Data System (ADS)

    Baek, Eun Jeong; Joh, Hea Min; Kim, Sun Ja; Chung, T. H.

    2016-07-01

    In this work, an atmospheric pressure plasma jet was fabricated and studied for plasma-liquid interactions. The plasma jet consists of a quartz-covered pin electrode and outer quartz tube with a tapered nozzle. Using the current-voltage (I-V) and optical emission characteristics of the plasma jet, the plasma density and the speed of the plume were investigated. The optical emission spectra clearly indicated the excited NO, O, OH, N2, and N2+ in the plasma plumes. Then the plasma jets were applied to the deionized water. We investigated the effects of the operating parameters such as applied voltage, pulse frequency, and gas flow rate on the generation of reactive species in the gas and liquid phases. The densities of reactive species including OH radicals were obtained at the plasma-liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. The nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of reactive oxygen and nitrogen species (RONS) in the plasmas and liquids.

  4. Experimental study of flow field around a plunging flexible hydrofoil

    NASA Astrophysics Data System (ADS)

    Martin-Alarcon, Leonardo; Yang, Tao; Shu, Fangjun; Wei, Mingjun

    2011-11-01

    Recent developments in micro air vehicles (MAVs) have led to the improvement of computational fluid dynamics (CFD) simulations capable of simulating flexible flapping wing phenomena. For validation of these simulations, an experimental methodology is applied to characterize the flow physics involved with an immersed flexible flapping hydrofoil. Using a one-degree of freedom crank-shaft system, a silicone hydrofoil was actuated to flap under various kinematic conditions. The hydrofoil was subject to active plunging and passive pitching motion in both water and aqueous glycerin solutions. Phase-locked particle image velocimetry (PIV) measurements were obtained around the flapping hydrofoil. These measurements, along with force measurements using a six-axis load cell, are used to compare the results with those of the numerical simulations. By comparing the hydrofoil deformation, vortex evolution and force generation, good agreements between CFD and experimental results were observed. Supported by Army High Performance Computing Research Center.

  5. Flow structure and performance of a flexible plunging airfoil

    NASA Astrophysics Data System (ADS)

    Akkala, James Marcus

    An investigation was performed with the intent of characterizing the effect of flexibility on a plunging airfoil, over a parameter space applicable to birds and flapping MAVs. The kinematics of the motion was determined using of a high speed camera, and the deformations and strains involved in the motion were examined. The vortex dynamics associated with the plunging motion were mapped out using particle image velocimetry (PIV), and categorized according to the behavior of the leading edge vortex (LEV). The development and shedding process of the LEVs was also studied, along with their flow trajectories. Results of the flexible airfoils were compared to similar cases performed with a rigid airfoil, so as to determine the effects caused by flexibility. Aerodynamic loads of the airfoils were also measured using a force sensor, and the recorded thrust, lift and power coefficients were analyzed for dependencies, as was the overall propulsive efficiency. Thrust and power coefficients were found to scale with the Strouhal number defined by the trialing edge amplitude, causing the data of the flexible airfoils to collapse down to a single curve. The lift coefficient was likewise found to scale with trailing edge Strouhal number; however, its data tended to collapse down to a linear relationship. On the other hand, the wake classification and the propulsive efficiency were more successfully scaled by the reduced frequency of the motion. The circulation of the LEV was determined in each case and the resulting data was scaled using a parameter developed for this specific study, which provided significant collapse of the data throughout the entire parameter space tested.

  6. Liquid mixing enhanced by pulse width modulation in a Y-shaped jet configuration

    NASA Astrophysics Data System (ADS)

    Xia, Qingfeng; Zhong, Shan

    2013-04-01

    In this paper, mixing between two fluid streams, which are injected into a planar mixing channel via a Y-shaped confluence section at the same volume flow rate, is studied experimentally. The injection of the two fluid streams is controlled by two separate solenoid valves, which are operated with a phase difference of 180°, using pulse width modulation. The experiments are conducted using water at a mean Reynolds number between 83 and 250, a range of pulsation frequencies and two duty cycles (25 and 50%). Both particle-image velocimetry and planar laser-induced fluorescence technique are used to visualize the flow patterns and to quantify the mixing degree in the mixing channel. This experiment shows that the pulsation of each jet produces vortical structures, which promotes mixing via vortex entrainment and vortex breakup, and at the same time the mixing is also greatly enhanced by sequential segmentation produced by a 180° out-of-phase pulsation of the two jets. This mixing enhancement method is effective at a Reynolds number greater than 125 with a mixing degree of 0.9 being achieved. For the Reynolds numbers studied in the present experiments, an optimal frequency exists, which corresponds to a Strouhal number in the range of 0.5-2. Furthermore, at a given mean Reynolds number a lower duty cycle is found to produce a better mixing due to the resultant higher instantaneous Reynolds number in the jet flow. It is also found that pulsation of only one jet can produce a similar mixing effect.

  7. Conjugate heat transfer from a heated disk to a thin liquid film formed by a controlled impinging jet

    NASA Technical Reports Server (NTRS)

    Faghri, A.; Thomas, S.; Rahman, M. M.

    1993-01-01

    An experimental and numerical study of the heat transfer from a heated horizontal disk to a thin film of liquid is described. The liquid was delivered to the disk by a collar arrangement such that the film thickness and radial velocity were known at the outer radius of the collar. This method of delivery is termed as a controlled impinging jet. Flow visualization tests were performed and heat transfer data were collected along the radius of the disk for different volumetric flow rates and inlet temperatures in the supercritical and subcritical regions. The heat transfer coefficient was found to increase with flow rate when both supercritical and subcritical regions were present on the heated surface. A numerical simulation of this free surface problem was performed, which included the effects of conjugate heat transfer within the heated disk and the liquid. The numerical predictions agree with the experimental results and show that conjugate heat transfer has a significant effect on the local wail temperature and heat transfer coefficient.

  8. Modified Design of Hydroturbine Wicket Gates to Include Liquid Control Jets

    NASA Astrophysics Data System (ADS)

    Lewis, Bryan; Cimbala, John; Wouden, Alex

    2013-11-01

    With the ever-increasing penetration of alternative electricity generation, it is becoming more common to operate hydroturbines under off-design conditions in order to maintain stability in the electric power grid. Improving the off-design performance of these turbines is therefore of significant importance. As the runner blades of a Francis hydroturbine pass though the wakes created by the upstream guide vanes (wicket gates and stay vanes), they experience significant changes in the instantaneous values of absolute velocity, flow angle, and pressure. The concept of adding water jets to the trailing edge of the guide vanes is proposed as a method for reducing the dynamic load on the hydroturbine runner blades, as well as modifying the flow angle of the water entering the runner to improve turbine efficiency during off-design operation. In order to add water jets that are capable of turning the flow, a modified beveled trailing edge design is presented. Computational experiments show that a +/-5° change in swirl angle is achievable with the new design, as well as up to 4% improvement in turbine efficiency during off-design operation. This correlates to an overall improvement in machine efficiency of up to 2%, when the losses through the jet channels are taken into account. Funding for this work was provided by the DOD, through the National Defense Science and Engineering Graduate (NDSEG) Fellowship, and the DOE, through the Penn State Hydropower Research Grant.

  9. Scaling-up a liquid water jet laser plasma source to high average power for extreme-ultraviolet lithography

    NASA Astrophysics Data System (ADS)

    Vogt, Ulrich; Stiel, Holger; Will, Ingo; Wieland, Marek; Wilhein, Thomas; Nickles, Peter V.; Sandner, Wolfgang

    2001-08-01

    In this article we describe a laser plasma source for Extreme Ultraviolet Lithography (EUVL) based on a liquid water jet target. Although jet targets are known for some time now, no attempts have been made to prove the functionality of the target under conditions similar to an EUVL production-line facility, that means illumination with high average power laser systems (in the multi-kW regime) at repetition rates in the kHz region. Such systems are currently under development. We used the MBI-burst laser to simulate these extreme illumination conditions. We examined the hydrodynamic stability of the target as a function of the laser repetition rate at different average laser powers (0.6kW and 5kW per burst). Additionally, the dependence of the conversion efficiency on pulse duration in the range from 30ps to 3ns was investigated. From our results one can conclude parameters for future design of driver lasers for EUVL systems.

  10. A Needleless Liquid Jet Injection Delivery Method for Cardiac Gene Therapy: A Comparative Evaluation Versus Standard Routes of Delivery Reveals Enhanced Therapeutic Retention and Cardiac Specific Gene Expression

    PubMed Central

    Fargnoli, AS; Katz, MG; Williams, RD; Margulies, KB; Bridges, CR

    2014-01-01

    Background This study evaluates needleless liquid jet method and compares it with three common experimental methods: (1) Intramuscular injection (IM) (2) Left ventricular intracavitary infusion (LVIC) (3) LV intracavitary infusion with aortic and pulmonary occlusion (LVIC-OCCL). Methods and Results Two protocols were executed. First, [n=24 rats], retention of dye was evaluated 10 minutes after delivery in an acute model. The acute study revealed the following: significantly higher dye retention (expressed as % myocardial cross section area) in the left ventricle in both the Liquid Jet [52±4] % and LVIC-OCCL [58±3] % groups p<0.05 compared with IM [31±8] % and LVIC [35±4] %. In the second, [n=16 rats], each animal received AAV.EGFP at a single dose with terminal 6 week endpoint. In the second phase with AAV.EGFP at 6 weeks post-delivery, a similar trend was found with Liquid Jet [54±5] % and LVIC-OCCL [60±8] % featuring more LV expression as compared with IM [30±9] % and LVIC [23±9] %. The IM and LVIC-OCCL cross sections revealed myocardial fibrosis. Conclusions With more detailed development in future model studies, needleless liquid jet delivery offers a promising strategy to improve direct myocardial delivery. PMID:25315468