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Sample records for plunging liquid jet

  1. Study of Air Entrainment by a Horizontal Plunging Liquid Jet

    NASA Astrophysics Data System (ADS)

    Trujillo, Mario; Deshpande, Suraj; Wu, Xiongjun; Chahine, Georges

    2009-11-01

    The process of air entrainment following the impact of an initially horizontal circular water jet on a pool of water has been studied computationally and experimentally. It has been found that the entrainment of air cavities in the near field region is periodic, not continuous as reported in earlier studies. The simulations are based on a Volume-of-Fluid methodology with interfacial compression using a modified version of the open source utilities, OpenFoam. Close agreement with experiments is reported on the creation of cavities in the near field, where air entrainment occurs. The period of entrainment is found to be proportional to g, and a simplified closed-form solution for this periodic event is presented. An overall physical picture of the mechanisms leading to bubble formation is given. The far field, which is characterized by the presence of small bubbles is only partially resolved computationally. Comparisons against velocity data are performed in this region leading to adequate qualitative agreement.

  2. 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 ? = 10 to ? = 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 ? 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 ? = 12. Qualitatively, for steeper jets, such large stagnation pressure region does not exist, and the deflection of the entire incoming jet is non-existent. In fact, for ? = 25, 45, 90, the jet penetrates the pool nearly undisturbed and consequently large cavities are not formed.

  3. 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, ?) 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, ?0) 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 number, Cac = ??Vc/sigma and viscosity ratio, ?0/? in postulating an alternate approach involving scaling of the pertinent physics by using liquids as entrained fluids. The scaling approach is tested using a rotating cylinder placed at the interface between two fluids. A mesh-independence study using successively finer meshes predicted critical entrainment velocity values within about 1% of each other. Numerical predictions compared well with experimental data, with less than 1% difference in the case where exact experimental data was available, and a maximum of 6% difference for cases where experimental data was extrapolated to make the comparison. These results lend credibility to our approach. The effect of densities of the two fluids manifests as buoyancy force at the interfacial cusp. Remarkably, contrary to a priori notions, our simulation results showed that as Deltarho increased, the effect of buoyancy decreased relative to other forces at the interfacial cusp. Finally, we proposed an empirical correlation between Cac and ? 0/? which allows extrapolation of critical entrainment conditions between the rotating-cylinder configuration (with liquids being entrained) to the plunging-jet configuration (with air being entrained). The primary contribution of this research is the physics-based scaling approach utilized to overcome the simulation challenges posed by the physics of interface rupture and entrainment.

  4. 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

  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. Enhancing liquid jet erosion

    SciTech Connect

    Johnson V.E. Jr.

    1984-10-02

    Process and apparatus for enhancing the erosive intensity of a high velocity liquid jet when the jet is impacted against a surface for cutting, cleaning, drilling or otherwise acting on the surface. A preferred method comprises the steps of forming a high velocity liquid jet, oscillating the velocity of the jet at a preferred Strouhal number, and impinging the pulsed jet against a solid surface to be eroded. Typically the liquid jet is pulsed by oscillating the velocity of the jet mechanically or by hydrodynamic and acoustic interactions. The invention may be applied to enhance cavitation erosion in a cavitating liquid jet, or to modulate the velocity of a liquid jet, or to modulate the velocity of a liquid jet exiting in a gas, causing it to form into discrete slugs, thereby producing an intermittent percussive effect.

  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. Determination of heat transfer coefficients in plastic French straws plunged in liquid nitrogen.

    PubMed

    Santos, M Victoria; Sansinena, M; Chirife, J; Zaritzky, N

    2014-12-01

    The knowledge of the thermodynamic process during the cooling of reproductive biological systems is important to assess and optimize the cryopreservation procedures. The time-temperature curve of a sample immersed in liquid nitrogen enables the calculation of cooling rates and helps to determine whether it is vitrified or undergoes phase change transition. When dealing with cryogenic liquids, the temperature difference between the solid and the sample is high enough to cause boiling of the liquid, and the sample can undergo different regimes such as film and/or nucleate pool boiling. In the present work, the surface heat transfer coefficients (h) for plastic French straws plunged in liquid nitrogen were determined using the measurement of time-temperature curves. When straws filled with ice were used the cooling curve showed an abrupt slope change which was attributed to the transition of film into nucleate pool boiling regime. The h value that fitted each stage of the cooling process was calculated using a numerical finite element program that solves the heat transfer partial differential equation under transient conditions. In the cooling process corresponding to film boiling regime, the h that best fitted experimental results was h=148.125.4 W/m(2) K and for nucleate-boiling h=135551 W/m(2) K. These values were further validated by predicting the time-temperature curve for French straws filled with a biological fluid system (bovine semen-extender) which undergoes freezing. Good agreement was obtained between the experimental and predicted temperature profiles, further confirming the accuracy of the h values previously determined for the ice-filled straw. These coefficients were corroborated using literature correlations. The determination of the boiling regimes that govern the cooling process when plunging straws in liquid nitrogen constitutes an important issue when trying to optimize cryopreservation procedures. Furthermore, this information can lead to improvements in the design of cooling devices in the cryobiology field. PMID:25445573

  9. Modeling liquid jet atomization processes

    NASA Astrophysics Data System (ADS)

    Heister, Stephen D.

    1994-11-01

    This report summarizes efforts in developing an analytic/numerical modeling capability for both steady and unsteady liquid jet atomization processes. The research involves the application of boundary element methods to model nonlinear deformation of liquid surfaces. An inviscid model has been developed to investigate dynamics of a finite-length jet which includes the presence of the orifice flow passages. In addition, a second model has been developed to simulate gas-phase interactions with the distorting jet surface. Preliminary developments associated with a viscous model are also discussed.

  10. 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

  11. 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

  12. 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 experimentally. In particular, a quantitative measure of jet susceptibility to unsteadiness has been established. Steady jets can be achieved in two ways: by being discharged from deLaval nozzles (increasing the exit Mach number) or by being overpressured.The unsteady behavior is modeled as the collapse of a bubble in liquid; comparisons of collapse times show good agreement. A mechanism for the unsteadiness is discussed. It is proposed that the chugging is the response of the jet boundary to a pressure difference between the jet and surrounding liquid, which arises as the result of the rapid expansion of a light fluid into a dense ambient atmosphere. The flow is shown to be similar to the discharge of a gas from a nozzle into a channel of larger cross section. An upper limit to the pressure difference is determined based on estimates of the minimum base pressure for such channel flows; a lower limit is established for the collapse time. All experimental values are within the bounds. The derived values indicate that the pressure differences between the jet and liquid may be more than 90 percent of the ambient pressure.

  13. 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.

  14. Atomization characteristics of impinging liquid jets

    NASA Technical Reports Server (NTRS)

    Ryan, H. M.; Anderson, W. E.; Pal, S.; Santoro, R. J.

    1993-01-01

    A systematic study is presented of the atomization of impinging liquid jets investigating the effects of jet conditions (laminar versus turbulent), orifice diameter, impingement angle and jet velocity. Results are compared to current theories in terms of sheet breakup length, sheet shape and drop size. Experiments contrasting laminar and turbulent jet conditions clearly show that the jet conditions have a dramatic effect on the atomization process.

  15. Cavitation bubble behavior inside a liquid jet

    NASA Astrophysics Data System (ADS)

    Robert, Etienne; Lettry, Jacques; Farhat, Mohamed; Monkewitz, Peter A.; Avellan, Franois

    2007-06-01

    The growth and collapse of laser-induced vapor cavities inside axisymmetric free-falling liquid water jets have been studied. Bubbles of different size are generated at various distances from the jet axis and the effects on the jet interface are recorded by means of ultrafast cinematography. The configuration is characterized by two dimensionless parameters: the bubble to jet diameter ratio ? and the eccentricity coefficient ? defined as the radius of bubble generation divided by the jet radius. For high ? and ?, microjets and droplets are ejected from the liquid jet at speeds exceeding 100m/s. The observed jet fragmentation shows similarities with experiments conducted on a liquid mercury jet hit by a pulsed proton beam, a candidate configuration for future accelerator based facilities.

  16. Liquid jet pumped by rising gas bubbles

    NASA Technical Reports Server (NTRS)

    Hussain, N. A.; Siegel, R.

    1975-01-01

    A two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. Bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped upward consists of the bubble wakes and the liquid brought into the jet region by turbulent entrainment. The expansion of the gas bubbles as they rise through the liquid is taken into account. The continuity and momentum equations are solved numerically for an axisymmetric air jet submerged in water. Water pumping rates are obtained as a function of air flow rate and depth of submergence. Comparisons are made with limited experimental information in the literature.

  17. Instability arisen on liquid jet penetrated in flowing liquid bath

    NASA Astrophysics Data System (ADS)

    Oka, Naoto; Ueno, Ichiro

    2009-11-01

    We carry out an experimental study with a special interest on a penetration process and an instability on a liquid jet impinged to a flowing liquid pool. The impinged jet penetrates into the flowing bath accompanying with an entrainment of the ambient immiscible gas without coalescing with the liquid in the pool until the air wrap around the jet collapses. The wrapping air controls instabilities arisen on the jet. We observe the dynamic behaviors of the penetrated jet and the departure of the bubble of the wrapping gas at the tip of the collapsing jet by use of a high-speed camera in order to categorize the behaviors as functions of the velocities of the jet and flow in the pool. We also evaluate an averaged thickness of the wrapping gas through the observation.

  18. Liquid jet pumped by rising gas bubbles

    NASA Technical Reports Server (NTRS)

    Hussain, N. A.; Siegel, R.

    1975-01-01

    From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped upward consists of the bubble wakes and the liquid brought into the jet region by turbulent entrainment. The expansion of the gas bubbles as they arise through the liquid is taken into account. The continuity and momentum equations are solved numerically for an axisymmetric air jet submerged in water. Water pumping rates are obtained as a function of air flow rate and depth of submergence. Comparisons are made with limited experimental information in the literature.

  19. Aerodynamic breakup of liquid jets - A review

    NASA Astrophysics Data System (ADS)

    Utreja, L. R.; Harmon, D. B.

    1990-06-01

    There are many applications for which it is important to understand the breakup of a liquid glob or jet into droplets (e.g., propulsion, control, and cooling of system components). The aerodynamic breakup of liquids is a complex process and is affected by the geometry, flow conditions and the liquid properties. This paper summarizes the results of several studies on the subject and discusses features of the phenomena which appear to be possible mechanisms in the liquid breakup process. The acceleration waves are the most likely mechanism responsible for the liquid breakup with secondary influence from the liquid properties, surface tension and viscosity. Correlations are presented for predicting the stability of liquid drops and breakup conditions. The results of this analysis will help toward better understanding of the role of aerodynamic forces in the breakup of liquids.

  20. Fundamental studies of impinging liquid jets

    NASA Technical Reports Server (NTRS)

    Anderson, W. E.; Ryan, H. M.; Pal, S.; Santoro, R. J.

    1992-01-01

    Atomization caused by impinging two liquid jets at an angle was studied experimentally and analytically. Measurements of drop size, sheet length and width at breakup, and apparent wave structures on the liquid sheet surface were made for different flow conditions and different geometries. The breakup of the attenuating liquid sheet into ligaments was modeled by linear stability theory. Breakup lengths were predicted from the fastest growing wave on the sheet surface, and drop diameters were calculated based on surface tension-controlled breakup of the ligaments.

  1. 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.

  2. Size limits the formation of liquid jets during bubble bursting

    PubMed Central

    Lee, Ji San; Weon, Byung Mook; Park, Su Ji; Je, Jung Ho; Fezzaa, Kamel; Lee, Wah-Keat

    2011-01-01

    A bubble reaching an airliquid interface usually bursts and forms a liquid jet. Jetting is relevant to climate and health as it is a source of aerosol droplets from breaking waves. Jetting has been observed for large bubbles with radii of R?100??m. However, few studies have been devoted to small bubbles (R<100??m) despite the entrainment of a large number of such bubbles in sea water. Here we show that jet formation is inhibited by bubble size; a jet is not formed during bursting for bubbles smaller than a critical size. Using ultrafast X-ray and optical imaging methods, we build a phase diagram for jetting and the absence of jetting. Our results demonstrate that jetting in bubble bursting is analogous to pinching-off in liquid coalescence. The coalescence mechanism for bubble bursting may be useful in preventing jet formation in industry and improving climate models concerning aerosol production. PMID:21694715

  3. Size limits the formation of liquid jets during bubble bursting.

    PubMed

    Lee, Ji San; Weon, Byung Mook; Park, Su Ji; Je, Jung Ho; Fezzaa, Kamel; Lee, Wah-Keat

    2011-01-01

    A bubble reaching an air-liquid interface usually bursts and forms a liquid jet. Jetting is relevant to climate and health as it is a source of aerosol droplets from breaking waves. Jetting has been observed for large bubbles with radii of R?100??m. However, few studies have been devoted to small bubbles (R<100??m) despite the entrainment of a large number of such bubbles in sea water. Here we show that jet formation is inhibited by bubble size; a jet is not formed during bursting for bubbles smaller than a critical size. Using ultrafast X-ray and optical imaging methods, we build a phase diagram for jetting and the absence of jetting. Our results demonstrate that jetting in bubble bursting is analogous to pinching-off in liquid coalescence. The coalescence mechanism for bubble bursting may be useful in preventing jet formation in industry and improving climate models concerning aerosol production. PMID:21694715

  4. Dropsize correlation for cryogenic liquid-jet atomization

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1990-01-01

    Momentum transfer from high velocity nitrogen gas flow to liquid-nitrogen jets was investigated. A correlation of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for cryogenic liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied by using three differently sized two-fluid fuel atomizers with different nozzle diameters.

  5. Dropsize correlation for cryogenic liquid-jet atomization

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1991-01-01

    Momentum transfer from high velocity nitrogen gas flow to liquid-nitrogen jets was investigated. A correlation of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for cryogenic liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied by using three differently sized two-fluid fuel atomizers with different nozzle diameters.

  6. Liquid breakup studies for jet-type singlet oxygen generators

    NASA Astrophysics Data System (ADS)

    Schall, Wolfgang O.; Plock, Ina

    1997-04-01

    The instability of the liquid jets in a jet singlet oxygen generator for oxygen-iodine lasers may limit the operational conditions and the scalability of such generators. Therefore the type of instability and the breakup behavior of jets is investigated experimentally for varying operational conditions. Jets of basic hydrogen peroxide are simulated by the use of glycerin solutions with different viscosities. Transition from laminar to turbulent jets, the associated breakup modes and the beginning of jet dissolution by surface spraying are observed. Jet lengths have been measured for various parameters, including gas counter-flow.

  7. Atomization of a liquid jet in a crossflow

    NASA Astrophysics Data System (ADS)

    Ashgriz, Nasser

    2012-06-01

    This presentation is on the recent development on the atomization process during the injection of a liquid jet into a high velocity gaseous cross flow. The results of experimental correlations on jet trajectory are reviewed. In addition, theoretical models for the simulation of the atomization process in jet in cross flow are discussed.

  8. 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.

  9. Plunging Ranula: A Case Report

    PubMed Central

    Gupta, Ambika; Karjodkar, F. R.

    2011-01-01

    Plunging ranulas, also known as deep, diving, cervical or deep plunging ranula, usually appear in conjunction with oral ranula. Rarely, these ranulas may arise independent of oral swelling. A rare case of plunging ranula without oral swelling is discussed along with review of literature. PMID:21991487

  10. Heat transfer in condensation of vapor on a liquid jet

    SciTech Connect

    Volkov, D.I.; Ivanov, V.I.; Christyakov, V.A. )

    1989-11-01

    An analysis of published technique for calculating coefficients of heat transfer from a vapor condensing on a liquid jet is presented. The analytic results of various investigators are compared with each other and with our experimental results. Recommendations are given on calculating the coefficient of heat transfer in condensation of vapor on a liquid jet.

  11. Liquid Jet Cavitation via Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Ashurst, W. T.

    1997-11-01

    A two-dimensional molecular dynamics simulation of a liquid jet is used to investigate cavitation in a diesel-like fuel injector. A channel with a length four times its width has been examined at various system sizes (widths of 20 to 160 σ, where σ is the zero energy location in the Lennard-Jones potential). The wall boundary condition is Maxwell's diffuse reflection, similar to the work by Sun & Ebner (Phys. Rev A 46, 4813, 1992). Currently, the jet exhausts into a vacuum, but a second, low density gas will be incorporated to represent the compressed air in a diesel chamber. Four different flow rates are examined. With ρ U equal to √mɛ/σ^2 (the largest flow rate) the static pressure decreases by a factor of twenty between the channel entrance and exit. The largest flow rate has a parabolic velocity profile with almost constant density across the channel. The smallest flow rate has the same velocity profile but the density exhibits a large variation, with the minimum value in the channel center. Thus, the product ρ U is nearly constant across the channel at this flow rate. The discharge coefficient CD has a small variation with flow rate, but the velocity coefficient CV varies with the amount of two-phase fluid within the channel. The ratio of CV to CD varies from 1.3 (largest flow rate) to 2.0 (the smallest flow rate, which is one-eighth of the largest).

  12. Flow visualization of high-speed pulsed-liquid jet

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Liang; Shi, Hong-Hui; Itoh, Motoyuki; Kishimoto, Masami

    2001-04-01

    This paper describes a flow visualization of high-speed liquid jets ranging from 20 m/s to 200 m/s, which were generated from two different methods. The first method is that the jet (200 m/s) is generated by using a high-speed projectile to impact a rectangular nozzle where water is contained. For the 200 m/s liquid jets, flow visualization was conducted using a Xenon flash unit. The second method is that the jet (20 m/s) is generated by using compressed gas to push liquid flowing through a tube. For the 20 m/s liquid jets, flow visualization was conducted using a strobe light unit. A number of interesting phenomena have been newly found.

  13. 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.

  14. Primary atomization of a liquid jet in crossflow

    NASA Astrophysics Data System (ADS)

    Rana, S.; Herrmann, M.

    2011-09-01

    In this fluid dynamics video, we present a visualization of the primary atomization of a turbulent liquid jet injected into a turbulent gaseous crossflow. It is based on a detailed numerical simulation of the primary atomization region of the jet using a finite volume, balanced force, incompressible LES/DNS flow solver coupled to a Refined Level Set Grid (RLSG) solver to track the phase interface position. The visualization highlights the two distinct breakup modes of the jet: the column breakup mode of the main liquid column and the ligament breakup mode on the sides of the jet and highlights the complex evolution of the phase interface geometry.

  15. Deformation of Laminar Round Liquid Jets in Uniform Fluid Crossflows

    NASA Astrophysics Data System (ADS)

    Aalburg, Christian; Faeth, Gerard M.; van Leer, Bram

    2000-11-01

    The deformation and drag properties of laminar round liquid jets in uniform crossflows of fluids having smaller densities were studied computationally. Effects of liquid-jet/ambient-fluid density ratio (in the range 2-64), liquid-viscous/surface-tension force ratio (Ohnesorge range of 0.001-10) and crossflow Reynolds numbers (up to 100) were emphasized in order to address conditions relevant to high-pressure combusting sprays. Predictions of deformation and drag properties were in good agreement with recent measurements. It was found that increased effects of liquid viscosity (increased Ohnesorge numbers) inhibited deformation and required progressively larger drag disturbances (larger Weber numbers) to initiate breakup, very similar to the secondary breakup properties of drops. The liquid-jet/ambient-fluid density ratio, and the presence of attached recirculation regions in the wake of the liquid jet (or Reynolds number) had surprisingly little effect on liquid jet deformation and breakup properties. Similar to drops, the liquid jets oscillated at small Ohnesorge numbers but this motion was damped as Ohnesorge numbers increased.

  16. Convective and Absolute Instability of Liquid Jets under Gravity Effects

    NASA Astrophysics Data System (ADS)

    Amini, Ghobad; Ihme, Matthias; Dolatabadi, Ali

    2012-11-01

    The break-up of liquid jets is of practical importance for several applications, including liquid-fuel-injection and ink-jet printing. In this work, the effect of gravity on the onset and growth rate of absolute and convective instabilities in liquid jets is studied. The mathematical problem is formulated in terms of quasi-one-dimensional equations, and the linearized stability equations are solved using a first-order perturbation method. An analytic form of the dispersion equation is derived, and the variation of the growth rate is investigated for a range of positive and negative Bond numbers, corresponding to downward-pointing and rising liquid jet. The critical Weber number, demarcating the transition between convective and absolute instability is determined as function of Reynolds and Froude numbers. Model-results for the limiting case of zero gravity are compared with classical results of Chandrasekhar and Leib & Goldstein, confirming the validity of this approach.

  17. Breakup of liquid jets from non-circular orifices

    NASA Astrophysics Data System (ADS)

    Sharma, Priyesh; Fang, Tiegang

    2014-02-01

    The purpose of this investigation is to study the effect of the orifice geometry on liquid breakup. In order to develop a better understanding of the liquid jet breakup, investigations were carried out in two stepsstudy of low-pressure liquid jet breakup and high-pressure fuel atomization. This paper presents the experimental investigations conducted to study the flow behavior of low-pressure water jets emanating from orifices with non-circular geometries, including rectangular, square, and triangular shapes and draws a comparison with the flow behavior of circular jets. The orifices had approximately same cross-sectional areas and were machined by electro-discharge machining process in stainless steel discs. The liquid jets were discharged in the vertical direction in atmospheric air at room temperature and pressure conditions. The analysis was carried out for gage pressures varying from 0 to 1,000 psi (absolute pressures from 0.10 to 6.99 MPa). The flow behavior was analyzed using high-speed visualization techniques. To draw a comparison between flow behavior from circular and non-circular orifices, jet breakup length and width were measured. The flow characteristics were analyzed from different directions, including looking at the flow from the straight edges of the orifices as well as their sharp corners. The non-circular geometric jets demonstrated enhanced instability as compared to the circular jets. This has been attributed to the axis-switching phenomenon exhibited by them. As a result, the non-circular jets yielded shorter breakup lengths as compared to the circular jets. In order to demonstrate the presence of axis-switching phenomenon in square and triangular jets, the jet widths were plotted along the axial direction. This technique clearly demonstrated the axis switching occurring in square and triangular jets, which was not clearly visible unlike the case of rectangular jets. To conclude, non-circular geometry induces greater instabilities in the liquid jets, thereby leading to faster disintegration. Thus, non-circular orifice geometries can provide a cheaper solution of improving liquid breakup and thus may enhance fuel atomization as compared to the precise manufacturing techniques of drilling smaller orifices or using costly elevated fuel injection pressure systems.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Fogelqvist, E.; Krdel, 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.

  20. Focusing of cylindrical liquid jets into droplets

    NASA Astrophysics Data System (ADS)

    Edwards, Kristen; McCleney, Amy; Bardet, Philippe

    2013-11-01

    Upward angled water jets discharging in quiescent air are studied experimentally with time varying forcing. The jets issue from a 2 mm diameter tube, while highly controllable forcing is accomplished with a magnetic linear motor coupled with an arbitrary waveform generator. In particular, regimes of jet focusing are generated at various injection rates. The jets result in large droplets that can be created at various elevations. This type of flow mimics the spray generated by an Archer fish. Actual forcing functions were monitored using LDT.

  1. Steady cone-jet electrosprays in liquid insulator baths.

    PubMed

    Barrero, A; López-Herrera, J M; Boucard, A; Loscertales, I G; Márquez, M

    2004-04-01

    This study shows that conducting liquids can be electrosprayed in steady cone-jet mode inside liquid insulator baths. Experimental results show that the current emitted from the meniscus fits well the scaling laws given in the literature for electrosprays in air at atmospheric pressure or vacuum. The technique may be of interest in obtaining fine liquid-liquid emulsions of uniformly sized droplets in the nanometric range. PMID:14985028

  2. 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.

  3. Liquid flow focused by a gas: jetting, dripping, and recirculation.

    PubMed

    Herrada, Miguel A; Gañán-Calvo, Alfonso M; Ojeda-Monge, Antonio; Bluth, Benjamin; Riesco-Chueca, Pascual

    2008-09-01

    The liquid cone-jet mode can be produced upon stimulation by a coflowing gas sheath. Most applications deal with the jet breakup, leading to either of two droplet generation regimes: Jetting and dripping. The cone-jet flow pattern is explored by direct axisymmetric volume of fluid (VOF) numerical simulation; its evolution is studied as the liquid flow rate is increased around the jetting-dripping transition. As observed in other focused flows such as electrospraying cones upon steady thread emission, the flow displays a strong recirculating pattern within the conical meniscus; it is shown to play a role on the stability of the system, being a precursor to the onset of dripping. Close to the minimum liquid flow rate for steady jetting, the recirculation cell penetrates into the feed tube. Both the jet diameter and the size of the cell are accurately estimated by a simple theoretical model. In addition, the transition from jetting to dripping is numerically analyzed in detail in some illustrative cases, and compared, to good agreement, with a set of experiments. PMID:18851159

  4. 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.

  5. 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.

  6. 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->∞.

  7. 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).

  8. 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 ?? 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.

  9. The Mechanics and Stability of Liquid Jets and Films

    NASA Astrophysics Data System (ADS)

    Ellwood, Kevin Richard John

    The underlying objective of this thesis is to study the process of coating by jet atomization, whose mechanism is divided into the mechanics and stability of liquid jets and the dynamics of thin films. The first step in the analysis of the mechanics of liquid jets is to examine the two-dimensional formation of non-Newtonian liquid jets. Steady-state, free-surface profiles and the subsequent motion of unstable surfaces are analyzed by the Galerkin finite-element method with free-surface parameterization. A constitutive equation is used to approximate Bingham liquids, which incorporates the effects of shear thinning. Increased surface tension and shear thinning destabilize round jets and increase the size of satellite drops, while increased yield stress decreases the size of satellite drops. The increase in satellite drop size is a response to the increased growth rate of disturbances on the free surface. Inertial effects prevent liquid from leaving regions that form satellites under the more rapid advance of disturbances. Nonlinear analysis show that the most unstable wavelength is closely approximated by linear theory. However, the dynamics near jet breakup are controlled by nonlinear effects. Two-dimensional studies are continued with the analysis of electrohydrodynamic jet breakup. An applied electric field will increase the size of the satellite drop formed, despite an increase in breakup time. The contradiction is due to the pressure gradient induced in the jet near the point of disintegration, which causes slowly propagating disturbances to advance rapidly in the final stages of the process. Three-dimensional jets are also analyzed using a unique streamlined finite-element method. The effects of inertia, gravity, and nozzle geometries are considered when producing steady-state jets. Also considered is the problem of die design where the die (or nozzle) shape is determined to produce a jet with a specified final shape, which is important to the extrusion of polymers. The next step of the study of coatings is an analysis of the spreading and leveling of thin films. The constitutive equation used is the modified Oldroyd-B model. Asymptotic analysis, which is exact for long wavelengths of small disturbance amplitudes, is compared with direct nonlinear finite-element analysis. Increased relaxation time decreases the rate of leveling and spreading, enhances surface defects, while increased retardation time reverses the effects of increased relaxation time.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Large bubble rupture sparks fast liquid jet.

    PubMed

    Son, Thomas; Antkowiak, Arnaud

    2012-07-01

    This Letter presents the novel experimental observation of long and narrow jets shooting out in disconnecting large elongated bubbles. We investigate this phenomenon by carrying out experiments with various viscosities, surface tensions, densities and nozzle radii. We propose a universal scaling law for the jet velocity, which unexpectedly involves the bubble height to the power 3/2. This anomalous exponent suggests an energy focusing phenomenon. We demonstrate experimentally that this focusing is purely gravity driven and independent of the pinch-off singularity. PMID:23031107

  15. 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.

  16. Impact of Liquid Fuel Boundary Condition and Nozzle Geometry on Liquid Jet in Crossflow Atomization

    NASA Astrophysics Data System (ADS)

    Ghods, Sina; Herrmann, Marcus

    2012-11-01

    The atomization of a liquid jet by a high speed cross-flowing gas has many applications such as gas turbines and augmentors. The mechanisms by which the liquid jet initially breaks up, however, are not well understood. Experimental studies suggest the dependence of spray properties on operating conditions and nozzle geometry. Detailed numerical simulations can offer better understanding of the underlying physical mechanisms that lead to the breakup of the injected liquid jet. In this work, we present detailed numerical simulation results of turbulent liquid jets injected into turbulent gaseous cross flows for different liquid fuel boundary conditions and injector geometries. We employ a finite volume, balanced force fractional step flow solver to solve the Navier-Stokes equations coupled to a Refined Level Set Grid method to follow the phase interface. To enable the simulation of atomization of high density ratio fluids, we ensure discrete consistency between the solution of the conservative momentum equation and the level set based continuity equation by employing the Rescaled Conservative Momentum method. We analyze the impact of liquid jet turbulent fluctuations and injector geometry on different jet properties such as jet penetration and generated drop sizes. This work was supported by NSF grant number CBET-0853627.

  17. Inkjet printing - the physics of manipulating liquid jets and drops

    NASA Astrophysics Data System (ADS)

    Martin, G. D.; Hoath, S. D.; Hutchings, I. M.

    2008-03-01

    Over the last 30 years inkjet printing technology has been developed for many applications including: product date codes, mailing shots, desktop printing, large-area graphics and, most recently, the direct writing of materials to form electronic, biological, polymeric and metallic devices. The new non-graphical applications require higher print rates, better resolution and higher reliability while printing more complex, non-Newtonian and heavily solids-loaded liquids. This makes the understanding of the physics involved in the precise manipulation of liquid jets and drops ever more important. The proper understanding and control of jet formation and subsequent motion of the jetted materials requires physical studies into material properties at very high shear rates, acoustic modes in print heads, instabilities of jets, drop formation, drop motion, stretching of fluid ligaments, the role of polymers in jet break up, electrical charging of drops and the aerodynamic and electrostatic interaction of jets and drops in flight. Techniques for observation, measurement and analysis are evolving to assist these studies. This paper presents some examples of the application of physics to understanding and implementing inkjet printing, including recent work at the Cambridge Inkjet Research Centre.

  18. Stabilization of Rayleigh instability in steady hollow liquid-metal jet by magnetic field

    SciTech Connect

    Dobkin, S.V.; Son, E.E.

    1983-10-01

    Methods of weakening the Rayleigh instability of liquid metal hollow jet are considered. The finite electrical conductivity of the liquid and the phase transition at the inner jet surface are considered. (AIP)

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

    NASA Technical Reports Server (NTRS)

    Trinh, Huu; Chen, C. P.

    2004-01-01

    Recent experimental investigations and physical modeling studies have indicated that turbulence behaviors within a liquid jet have considerable effects on the atomization process. For certain flow regimes, it has been observed that the liquid jet surface is highly turbulent. This turbulence characteristic plays a key role on the breakup of the liquid jet near to the injector exit. Other experiments also showed that the breakup length of the liquid core is sharply shortened as the liquid jet is changed from the laminar to the turbulent flow conditions. In the numerical and physical modeling arena, most of commonly used atomization models do not include the turbulence effect. Limited attempts have been made in modeling the turbulence phenomena on the liquid jet disintegration. The subject correlation and models treat the turbulence either as an only source or a primary driver in the breakup process. This study aims to model the turbulence effect in the atomization process of a cylindrical liquid jet. In the course of this study, two widely used models, Reitz's primary atomization (blob) and Taylor-Analogy-Break (TAB) secondary droplet breakup by O Rourke et al. are examined. Additional terms are derived and implemented appropriately into these two models to account for the turbulence effect on the atomization process. Since this enhancement effort is based on a framework of the two existing atomization models, it is appropriate to denote the two present models as T-blob and T-TAB for the primary and secondary atomization predictions, respectively. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic time scales and the initial flow conditions. This treatment offers a balance of contributions of individual physical phenomena on the liquid breakup process. For the secondary breakup, an addition 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. The turbulence energy is also considered in this process.

  20. 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.

  1. Converging swirling liquid jets from pressure swirl atomizers: Effect of inner air pressure

    NASA Astrophysics Data System (ADS)

    Sivakumar, D.; Raghunandan, B. N.

    2002-12-01

    Converging swirling liquid jets from pressure swirl atomizers injected into atmospheric air are studied experimentally using still and cine photographic techniques in the context of liquid-liquid coaxial swirl atomizers used in liquid rocket engines. The jet exhibits several interesting flow features in contrast to the nonswirling liquid jets (annular liquid jets) studied in the literature. The swirl motion creates multiple converging sections in the jet, which gradually collapse one after the other due to the liquid sheet breakup with increasing Weber number (We). This is clearly related to the air inside the converging jet which exhibits a peculiar variation of the pressure difference across the liquid sheet, ?P, with We. The variation shows a decreasing trend of ?P with We in an overall sense, but exhibits local maxima and minima at specific flow conditions. The number of maxima or minima observed in the curve depends on the number of converging sections seen in the jet at the lowest We. An interesting feature of this variation is that it delineates the regions of prominent jet flow features like the oscillating jet region, nonoscillating jet region, number of converging sections, and so on. Numerical predictions of the jet characteristics are obtained by modifying an existing nonswirling liquid jet model by including the swirling motion. The comparison between the experimental and numerical measurements shows that the pressure difference across the liquid sheet is important for the jet behavior and cannot be neglected in any theoretical analysis.

  2. 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 ?m 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 ?m. The growth rate of periodically perturbed water and ethanol/water mixture jets with a 100-?m 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.

  3. 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.

  4. 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.

  5. Supersonic liquid jets: Their generation and shock wave characteristics

    NASA Astrophysics Data System (ADS)

    Pianthong, K.; Zakrzewski, S.; Behnia, M.; Milton, B. E.

    The generation of high-speed liquid (water and diesel fuel) jets in the supersonic range using a vertical single-stage powder gun is described. The effect of projectile velocity and mass on the jet velocity is investigated experimentally. Jet exit velocities for a set of nozzle inner profiles (e.g. straight cone with different cone angles, exponential, hyperbolic etc.) are compared. The optimum condition to achieve the maximum jet velocity and hence better atomization and mixing is then determined. The visual images of supersonic diesel fuel jets (velocity about 2000 m/s) were obtained by the shadowgraph method. This provides better understanding of each stage of the generation of the jets and makes the study of their characteristics and the potential for auto-ignition possible. In the experiments, a pressure relief section has been used to minimize the compressed air wave ahead of the projectile. To clarify the processes inside the section, additional experiments have been performed with the use of the shadowgraph method, showing the projectile travelling inside and leaving the pressure relief section at a velocity of about 1100 m/s.

  6. 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...

  7. Liquid Engine Jet Atomization Workshop report

    NASA Technical Reports Server (NTRS)

    Gross, Klaus W.

    1987-01-01

    The workshop was oriented to disclose information and unsettled problems to understand the fundamental physical mechanism of the droplet formation process. Based on presentation and discussion of results, recommendations were made which should lead to associated future activities. To accomplish this task, existing observations and experiments, contributing to the basic knowledge, providing data for analytical concept verification, and forming a basis for empirical correlations were solicited. Advanced analytical modeling methods or results from specific studies were requested as well as the experience and advice from injector designers. All effort is directed to advance current analytical techniques, simulating the flow behavior downstream of the injection elements in a liquid rocket combustion chamber. Such a tool can be used to optimize injector designs with respect to short length weight savings, wall material protection, or large heat energy transport to a regenerative cooling fluid, while simultaneously achieving the maximum specific impulse in performance. The liquid atomization process also forms a sound basis for combustion instability analysis.

  8. Dynamics of a liquid jet atomized by gaseous crossflow

    NASA Astrophysics Data System (ADS)

    Marco, Arienti; Hagen, Gregory; Corn, May; Soteriou, Marios

    2008-11-01

    When captured by high-speed, high-resolution videos, the dynamics of a liquid jet subject to a crossflowing air stream with no external forcing appears to be composed by slow column bending motions and fast traveling surface waves. Sequences of consecutive near field line-of-sight images of the jet acquired for gas Weber numbers between 10 and 300 and momentum flux ratios between 10 and 100 are analyzed with the method of snapshots to decouple this complex liquid interface motion into few fundamental dynamic modes. The exposure time of each snapshot ``freezes'' the flow, thus providing a sharp liquid interface, while the acquisition rate is comparable to the characteristic time of moderate Weber number surface waves. Spectral decomposition analysis reveals broad-band oscillations that can be linked to the amplification of column waves near the point of column break-up. As the Weber number increases at constant momentum flux ratio, the broad band peak shifts toward higher frequencies until the aliasing limit is reached. As the liquid jet velocity increases, and the column becomes turbulent, a cascade of finer temporal and spatial structures are found with increasing pixel brightness variation intensity that affect similarly small scales of the downstream spray.

  9. Analysis of liquid reservoir effect induced by pulsed laser liquid jet.

    PubMed

    Arafune, T; Kato, T; Kobayashi, E; Washio, T; Nakagawa, A; Ogawa, Y; Tominaga, T

    2013-01-01

    A pulsed-laser-induced liquid jet (LILJ) is a new device used in neurosurgery to simultaneously crush, incise, and aspirate tissues and tumors, preserving blood vessels and nerves. In addition, a feature of a pulsed LILJ is its ability to excavate tissue at constant depth while a liquid jet is being repeatedly focused at the same point. To clarify the mechanisms of constant depth of excavation, we employed a gelatin phantom and extracted brain tissue using a high-speed camera, and we then confirmed that the liquid-reservoir-induced LILJ played an important role in enabling the safe usage of an LILJ. PMID:24109838

  10. 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.

  11. 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.

  12. Atomization of a Liquid Jet by a High Momentum Co-axial Swirling Gas Jet.

    NASA Astrophysics Data System (ADS)

    Préaux, Guillaume; Lasheras, Juan; Hopfinger, Emil

    1997-11-01

    The break-up and atomization of a low momentum round liquid jet by a high speed swirling coaxial air jet is investigated using laser diffraction and phase Doppler (PDPA) techniques. It was found that, for a given momentum flux ratio (M), there exists a critical swirl number S_cr (S is here defined as the ratio of the tangential to the axial air jet velocity), below which the liquid atomization is only weakly affected by the swirl. Above this critical number, the jet undergoes an explosive break-up whereby the radial spreading of the liquid is greatly enhanced. For small M the critical swirl number was found to decrease with increasing M, asymptotically approching a constant value at large M. Concerning the effect of the swirl on the atomisation we present, for a given value of M, detailed measurements of the droplet size probability density function (pdf) and of the liquid volumetric void fraction (α_l) for swirl numbers near and above the critical value, and compare them to the case of no swirl. For swirl numbers well above the critical, it is shown that the pdf of the droplet size distribution is highly non-uniform throughout the spray with both the mean droplet size (SMD) and αl at the outer edges being considerably larger than those at the centerline of the spray. Finally, the existance of a narrow banwidth of swirl numbers near the critical one for which an optimum spatial uniformity exists in both the droplet size and liquid void fraction is investigated.

  13. Global frequency response analysis of gravitationally stretched liquid jets

    NASA Astrophysics Data System (ADS)

    Consoli-Lizzi, Paula; Coenen, Wilfried; Sevilla, Alejandro

    2013-11-01

    The convective capillary break-up of freely falling axisymmetric jets of Newtonian liquid is theoretically studied with a one-dimensional description of the mass and momentum conservation equations. Instead of using the classical quasi-parallel assumption in the stability analysis, here we compute the global linear response of the flow to harmonic inputs at the exit of the jet, allowing us to predict its break-up length in cases where the base flow is not slender. Our theory compares favourably with recent experiments by Javadi et al. (PRL 110, 144501, 2013), who measured the break-up length of unforced liquid jets of several viscosities. From the physical point of view, our main finding is that the meniscus region near the injector outlet, where the jet experiences the strongest axial stretching, delays the growth of capillary disturbances due to a spatial counterpart of the kinematic stabilizing mechanism firstly described by Tomotika (Proc. Roy. Soc. 153, 1936) in a temporal setting. Supported by Spanish MINECO under project DPI 2011-28356-C03-02.

  14. 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 function, double gridding the fluid function, and using a higher order solution for the fluid function, interface smearing is avoided. These equations can be rewritten as two coupled Poisson equations that also include the velocity. The method of solution is as follows: first, the phase equations are solved from this solution, a velocity field is generated, then a successive overrelaxation scheme is used to solve for a pressure field consistent with the velocity solution. After the code was implemented in axisymmetric form and verified by several test cases, the drop tower runs of Aydelott were modeled. The model handed the free-surface deformation quite nicely, even to the point of modeling geyser growth in the regime where the free surface was no longer restrained. A representative run is shown.

  15. 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.

  16. Liquid jets injected into non-uniform crossflow

    NASA Astrophysics Data System (ADS)

    Tambe, Samir

    An experimental study has been conducted with liquid jets injected transversely into a crossflow to study the effect of non-uniformities in the crossflow velocity distribution to the jet behavior. Two different non-uniform crossflows were created during this work, a shear-laden crossflow and a swirling crossflow. The shear-laden crossflow was generated by merging two independent, co-directional, parallel airstreams creating a shear mixing layer at the interface between them. The crossflow exhibited a quasi-linear velocity gradient across the height of the test chamber. By varying the velocities of the two airstreams, the sense and the slope of the crossflow velocity gradient could be changed. Particle Image Velocimetry (PIV) studies were conducted to characterize the crossflow. The parameter, UR, is defined as the ratio of the velocities of the two streams and governs the velocity gradient. A positive velocity gradient was observed for UR > 1 and a negative velocity gradient for UR < 1. PIV and Phase Doppler Particle Anemometry (PDPA) studies were conducted to study the penetration and atomization of 0.5 mm diameter water jets injected into this crossflow. The crossflow velocity gradient was observed to have a significant effect on jet penetration as well as the post breakup spray. For high UR (> 1), jet penetration increased and the Sauter Mean Diameter (SMD) distribution became more uniform. For low UR (< 1), low penetration, higher droplet velocities and better atomization were observed. The second crossflow tested was a swirling flow generated using in-house designed axial swirlers. Three swirlers were used, with vane exit angles of 30, 45 and 60. Laser Doppler Velocimetry (LDV) was used to study the crossflow velocities. The axial (Ux) and the tangential (Utheta) components of the crossflow velocity were observed to decrease with increasing radial distance away from the centerbody. The flow angle of the crossflow was smaller than the vane exit angle, with the difference increasing with the vane exit angle. Water jets were injected from a 0.5 mm diameter orifice located on a cylindrical centerbody. Multi-plane PIV measurements were conducted to study the penetration and droplet velocity distribution of the jets. The jets were observed to follow a path close to the helical trajectory of the crossflow with a flow angle slightly less than the crossflow. This deficit in flow angle is attributed to the centrifugal acceleration experienced by the jet. Mie-Scattering images obtained from PIV were used to recreate the jet plume and to obtain the jet trajectory for penetration analysis. In cylindrical coordinate system, the jet penetration can be described in terms of radial and "circumferential" penetration, where circumferential penetration relates to the difference in the circumferential displacement of the jet and the crossflow over the same streamwise displacement. Radial penetration increased with q while circumferential penetration increased with swirl angle. PIV results from cross-sectional and streamwise planes were combined to generate three-dimensional droplet velocity distribution throughout the jet plume. The three-dimensional velocity distribution yielded further insight into the evolution of the jet plume.

  17. Penetration of Liquid Jets into a High-velocity Air Stream

    NASA Technical Reports Server (NTRS)

    Chelko, Louis J

    1950-01-01

    Data are presented showing the penetration characteristics of liquid jets directed approximately perpendicular to a high-velocity air stream for jet-nozzle-throat diameters from 0.0135 to 0.0625 inch, air stream densities from 0.0805 to 0.1365 pound per cubic foot, liquid jet velocities from 168.1 to 229.0 feet per second and a liquid jet density of approximately 62 pounds per cubic foot. The data were analyzed and a correlation was developed that permitted the determination of the penetration length of the liquid jet for any operation condition within the range of variables investigated.

  18. 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 discharge coefficient of 0.95 at the operating conditions of interest. The other injector was a sharp edged orifice with a length to diameter ratio of 10 and a discharge coefficient of 0.74 at the operating conditions of interest. It was shown that the sharp edged orifice was likely to develop cavitation bubbles beyond a flow Reynolds number of 8,000. It was found that a sharp transition in the injector can lead to the liquid column disintegrating sooner. The classical Rayleigh Taylor instabilities that are usually seen with a smooth transition in the injector were not seen in the presence of a sharp transition. The droplets produced with such an injector are larger in size and the spray penetrated deeper into the crossflow.

  19. 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.

  20. 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

  1. Jet impingement and primary atomization of non-Newtonian liquids

    NASA Astrophysics Data System (ADS)

    Mallory, Jennifer A.

    The effect of liquid rheology on the flowfield resulting from non-Newtonian impinging jets was investigated experimentally and analytically. Experimental data were acquired using a unique experimental apparatus developed to examine the jet impingement of non-Newtonian liquids. The analytical modeling was aimed at determining which physical mechanisms transform non-Newtonian impinging jets into a sheet with waves on its surface, how those waves influence sheet fragmentation and subsequent ligament formation, and how those ligaments break up to form drops (primary atomization). Prior to impinging jet measurements, the rheological properties of 0.5 wt.-% CMC-7HF, 1.4 wt.-% CMC-7MF, 0.8 wt.-% CMC-7MF, 0.06 wt.-% CMC-7MF 75 wt.-% glycerin, 1 wt.-% Kappa carrageenan, and 1 wt.-% Agar were determined through the use of rotational and capillary rheometers. Two approaches were used to experimentally measure solid-like gel propellant simulant static surface tension. All liquids exhibited pseudoplastic rheological behavior. At various atomizer geometric and flow parameters sheet instability wavelength, sheet breakup length, ligament diameter, and drop sizes were measured from high-speed video images. Results showed that viscosity dependence on shear rate is not the sole factor that determines atomization likelihood. Instead, a key role is played by the interaction of the gelling agent with the solvent at the molecular level. For instance, despite high jet exit velocities and varying atomizer geometric parameters HPC gel propellant simulants did not atomize. The molecular nature of HPC results in physical entanglement of polymer chains when gelled, which resists liquid breakup and subsequent spray formation. However, atomization was achieved with Agar, which absorbs the water and forms a network around it rather than bonding to it. The measured liquid sheet instability wavelength, sheet breakup length, ligament diameter, and drop sizes were compared to predictions from a linear stability theory model, which employed the Bird-Carreau pseudoplastic rheology model and semi-empirical theories of sheet breakup length taken from the literature. Analytical results accurately predicted experiment data for all investigated formulations, with the exception of 1 wt.-% Agar. This is attributed to Agar's slightly different chemical molecular structure and its effect on resultant atomization. Overall, the linear stability theory developed here shows an improvement over previous linear stability theories which consistently over-predicted results.

  2. 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.

  3. 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.

  4. Atomization patterns of liquid sheets formed by two impinging jets

    NASA Astrophysics Data System (ADS)

    Ma, Dong-Jun; Chen, Xiao-Dong; Yang, Vigor

    2010-11-01

    High fidelity numerical simulations have been performed to study the atomization patterns and breakup characteristics of liquid sheets formed by two impinging jets. A fully three-dimensional Volume-of-Fluid method with adaptive mesh refinement (AMR) based on octree-mesh is used to simulate the primary atomization. The start of the art visualization techniques with volume rending were also used to highlight the breakup characteristics. The oblique collision of two cylindrical laminar jets leads to the liquid owing outward from the impact point, creating a thin sheet which lies in a plane perpendicular to the plane containing the two jets and disintegrates into ligaments or droplets. The breakup of the sheet is dominant by the viscosity and surface tension effects (Reynolds and Webber number). The periodic waves from the point of impingement were apparent on the surface of the sheet. The circumferentially space drops were shed from the periphery of the sheet, as well as the ligaments were fragmented from the leading edge of the sheet and then broke into droplets following the Rayleigh mechanism. The impact waves caused early breakdown of the sheet downstream of the impingement point, whereas waves amplified by aerodynamic stresses controlled the breakdown of the rest of the sheet and the ligaments.

  5. 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.

  6. 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.

  7. 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.

  8. Liquid jet generated by thermocavitation bubbles within a droplet

    NASA Astrophysics Data System (ADS)

    Padilla-Martinez, J. P.; Banks, Darren; Ramirez-San-Juan, J. C.; Aguilar, G.; Ramos-Garcia, R.

    2013-03-01

    High-speed video imaging was used to study the dynamic behavior of cavitation bubbles induced by a continuous wave (CW) laser into highly absorbing droplets water containing copper nitrate (CuNO4). The droplet lays horizontally on a glass surface and the laser beam (?=975 nm) propagates vertically from underneath, across the glass and into the droplet. This beam is focused ?=400 ?m above the glass-liquid interface in order to produce the largest bubble as possible (Rmax ~ 1mm). In our experiment the thermocavitation bubbles are always in contact with the substrate, taking a hemispherical shape, regardless of where the laser focal point is, as opposed to the other methods that involved nano and picosecond laser pulses, where bubbles may nucleate and grow within the bulk of the fluid. We focus on the liquid jet which emerges out the droplet at velocities of about 3 m/s, due to the acoustic pressure wave (APW) emitted immediately after the bubble collapse, and after it breaks up into a secondary droplet or droplets depending of the droplet's volume, showing an alternative way of droplet generator that is simplest, light and cheaper. The dynamics of cavitation bubbles in confined geometries (drops) offers a rich hydrodynamic and the liquid jet generated after the bubble collapse could be used like acoustic waveguide, as was showed by Nicolas Bertin et. al.

  9. 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 of the acoustic field generated within the chamber on the dark core length and the inner jet spreading angles is presented and the stability of coaxial flows in the current flow regime is discussed with respect to evidence for convective and absolute jet instabilities under different operating conditions.

  10. Disintegration of a Round Liquid Jet due to Impact on a Superhydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Jalaal, Maziyar; Stoeber, Boris

    2013-11-01

    Liquid jet breakup has several applications such as Inkjet printers, diesel fuel injectors, and paint sprays. Very recently liquid jets have been shown to be useful for small volume transportation (Clestini et al. Soft Matter, 2010), where a micro-scale liquid jet on superhydrophobic surface was investigated. Although the instability of the liquid jet for some circumstances was shown, the disintegration of the liquid jet was not discussed. In the present study, we aim to analyze the breakup of a micro liquid jet due to inclined impact to a superhydrophobic surface. A range of Weber and Reynolds numbers have been explored experimentally. Water-glycerin solution as the working fluid. Generally, it is shown that the liquid jet forms a disc-like film over the surface and further rebounds (``bouncing jet''). A simple energy balance method is provided to estimate the diameter of the disc-like film. It is shown, for the case of low viscosity (large Re), this parameter is logarithmically proportional to the normal Weber number. Additionally, linear stability analysis for viscous jets provides a good estimate of droplet size. From an application point of view, using superhydrophobic surfaces 1) enables rebound of the liquid jet 2) advances the breakup point (shorten the breakup length).

  11. 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 and drop velocity mean values and distribution of several non-Newtonian liquids using a like-on-like impinging jet doublet. The drop size and drop velocity are important areas of study because of the effect on mass transfer and mass dispersal. Phase Doppler Anemometry (PDA) is used to measure the drop diameter and drop velocity. The drop diameter is measured by finding a phase difference between two signals. The drop velocity is measured using Laser Doppler Anemometry (LDA), which is based on the Doppler shift. Parametric studies are conducted based on dimensionless groups, impinging jet geometry, and spatial position. The investigated non-Newtonian liquids collapse onto a single mean diameter versus Reynolds number curve. However, this behavior is not observed for the gels due to differences in surface tension and molecular structure. In general, increasing the inertial force results in smaller drops and greater drop velocities. The different geometric parameters are observed to have varying degrees of influence, based on the propellant simulant considered. Larger drops with lower axial velocities are generally observed with increasing transverse distances from the centerline of the impinging jet spray.

  12. Penetration process and instabilities arisen on a liquid jet impinged to a liquid flowing in a channel

    NASA Astrophysics Data System (ADS)

    Hattori, Kaoru; Ueno, Ichiro

    2010-11-01

    We conduct a series of experiments with a special interest on a penetration process and instabilities arisen on a liquid jet impinged to a liquid of the same kind flowing in a channel. The impinged jet penetrates into the flowing bath accompanying with entrainment of the ambient immiscible gas, which results in the impinged jet wrapped by the entrained gas as a "sheath." This sheath formation enables the impinged jet to survive in the fluid in the channel without coalescing until the entrained-air sheath breaks down. Occasionally a "cap" of the entrained air is formed at the tip of the penetrated jet, and the jet elongates like a long balloon. Dynamic behaviors of the penetrated jet and the departure of the bubble of warring gas at the tip of the collapsing jet observed by use of a high-speed camera are discussed.

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

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza; GTL jet fuel Consortium Team

    2012-11-01

    Gas-to-Liquid (GTL) Synthetic Paraffinic Kerosene (SPK) fuel obtained from Fischer-Tropsch synthesis has grabbed the global attention due to its cleaner combustion characteristics. GTL fuels are expected to meet the vital qualities such as atomization, combustion and emission characteristics of conventional jet fuels. It is imperative to understand fuel atomization in order to gain insights on the combustion and emission aspects of an alternative fuel. In this work spray characteristics of GTL-SPK, which could be used as a drop-in fuel in aircraft gas turbine engines, is studied. This work outlines the spray experimental facility, the methodology used and the results obtained using two SPK's with different chemical compositions. The spray characteristics, such as droplet size and distribution, are presented at three differential pressures across a simplex nozzle and compared with that of the conventional Jet A-1 fuel. Experimental results clearly show that although the chemical composition is significantly different between SPK's, the spray characteristics are not very different. This could be attributed to the minimal difference in fluid properties between the SPK's. Also, the spray characteristics of SPK's show close resemblance to the spray characteristics of Jet A-1 fuel.

  14. Phase field modeling of liquid jets in low gravity

    NASA Astrophysics Data System (ADS)

    Chato, David J.

    2009-03-01

    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. The model is solved numerically with a compact fourth order stencil on an 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 the simple turbulence model and the existence of slosh baffles in the experiment that were not included in the model. Parametric investigation was conducted to study 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. A breakthrough Weber number of 1 was predicted by the variation of the surface tension model which is close to the experimentally measured Weber number of 1.5 found in prior experimental work.

  15. 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.

  16. 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?m 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.

  17. 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.

  18. 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.

  19. 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 influence the characteristics of the jet upwind surface. The present results for jet breakup in still air also show that the ligament distribution follows an arrangement along the jet surface and bubble formation associated with the jet breakup as well. The x-ray diagnostic allowed the surface and internal topography of fuel jets to be visualized and the breakup mechanism in the dense-spray near-injector region to be revealed.

  20. Parametric effects on pinch-off modes in liquid/liquid jet systems

    NASA Astrophysics Data System (ADS)

    Milosevic, Ilija N.

    Many industries rely on liquid/liquid extraction systems, where jet pinch off occurs on a regular basis. Inherent short time and length scales make analytical and numerical simulation of the process very challenging. A main objective of this work was to document the details of various pinch-off modes at different length scales using Laser Induced Fluorescence and Particle Image Velocimetry. A water glycerine mixture was injected into ambient either silicone oil or 1-octanol. The resultant viscosity ratios, inner to outer fluid, were 1.6 and 2.8, respectively. Ohnesorge numbers were 0.013 for ambient silicone oil and 0.08 for ambient 1-octanol. Reynolds and Strouhal numbers ranged from 30 to 100 and 0.5 to 3.5, respectively. Decreasing the Strouhal number increased the number of drops formed per forcing. Increasing the Reynolds number suppressed satellite formation, and in some cases the number of drops decreased from two to one per cycle. Increasing the Ohnesorge number to 0.08 suppressed the pinch off yielding a longer jet with three-dimensional threads. At Ohnesorge number 0.013, increasing the forcing amplitude shortened the jet, and eventually led to a dripping mode. High-resolution measurements of pinch-off angles were compared to results from similarity theory. Two modes were investigated: drops breaking from the jet (jet/drop) and, one drop splitting into two (splitting drop). The jet/drop mode angle measurements agreed with similarity predictions. The splitting drop mode converged towards smaller angles. Scaling analysis showed that a Stokesian similarity regime applied for a neck radius of 6 microns or less. The smallest radius observed in experiments was 15 microns. Therefore, it is not known whether splitting drop mode might still converge to same behavior.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. The Impact of Density Ratio on the Primary Atomization of a Turbulent Liquid Jet in Crossflow

    NASA Astrophysics Data System (ADS)

    Herrmann, Marcus

    2009-11-01

    Atomizing liquids by injecting them into crossflows is a common approach to generate fuel sprays in gas turbines and augmentors. Although correlations derived from experimental data exist for the jet penetration, predicting the drop size distribution resulting from the primary breakup of the liquid jet is a more challenging task. Furthermore, most correlations are derived from experimental data performed at ambient conditions, thereby not matching the density ratio found in most gas turbine applications. In this paper, we will study the impact of density ratio on the primary atomization of a turbulent liquid jet injected into a subsonic crossflow using detailed numerical simulations, leaving constant all other relevant characteristic numbers, i.e. jet and crossflow Weber numbers, Reynolds numbers, and momentum flux ratio. The influence of density ratio on the physical mechanisms causing the initial breakup of the jet, the resulting grid dependent/independent drop size distributions, and the jet penetration will be discussed.

  7. Analysis of impingement heat transfer for two parallel liquid-metal slot jets

    NASA Technical Reports Server (NTRS)

    Siegel, R.

    1974-01-01

    An analytical method is developed for determining heat transfer by impinging liquid-metal slot jets. The method involves mapping the jet flow region, which is bounded by free streamlines, into a potential plane where it becomes a uniform flow in a channel of constant width. The energy equation is transformed into potential plane coordinates and is solved in the channel flow region. Conformal mapping is then used to transform the solution back into the physical plane and obtain the desired heat-transfer characteristics. The analysis given here determines the heat-transfer characteristics for two parallel liquid-metal slot jets impinging normally against a uniformly heated flat plate. The liquid-metal assumptions are made that the jets are inviscid and that molecular conduction is dominating heat diffusion. Wall temperature distributions along the heated plate are obtained as a function of spacing between the jets and the jet Peclet number.

  8. Behavior of cylindrical liquid jets evolving in a transverse acoustic field

    NASA Astrophysics Data System (ADS)

    Carpentier, Jean-Baptiste; Baillot, Françoise; Blaisot, Jean-Bernard; Dumouchel, Christophe

    2009-02-01

    This paper presents a theoretical and an experimental investigation of low-velocity cylindrical liquid jets submitted to transverse planar acoustic waves. For this purpose, the behavior of a liquid jet traversing the section of a Kundt tube was examined. Experiments reported that the liquid jet could be either deviated from its trajectory or deformed as a succession of lobes oriented in space and whose length and width depend on the jet acoustic environment. Furthermore, for a sufficient acoustic velocity, the jet deformation increases in such proportion that a premature and vivid atomization mechanism disintegrates the liquid flow. Theoretical models are proposed to understand these behaviors. The first one calls out for acoustic radiation pressure to explain the jet deviation. The second one consists in a modal analysis of the vibrations of a jet when submitted to a transverse stationary acoustic field. As a first approach, a simplified two-dimensional model is proposed. This model reports that a sudden exposition of the jet to an acoustic field triggers two jet eigenmodes. One of them induces jet deformations that were not experimentally observed. This part of the solution emerges due to theoretical deficiencies. However, the second mode reproduces the lobe formation and leads to atomization criteria in good agreement with the experimental results. The paper ends with an extension of the mathematical development in three dimensions in order to provide a basis to a more consistent model.

  9. Detailed Numerical Simulation of Liquid Jet In Crossflow Atomization with High Density Ratios

    NASA Astrophysics Data System (ADS)

    Ghods, Sina

    The atomization of a liquid jet by a high speed cross-flowing gas has many applications such as gas turbines and augmentors. The mechanisms by which the liquid jet initially breaks up, however, are not well understood. Experimental studies suggest the dependence of spray properties on operating conditions and nozzle geom- etry. Detailed numerical simulations can offer better understanding of the underlying physical mechanisms that lead to the breakup of the injected liquid jet. In this work, detailed numerical simulation results of turbulent liquid jets injected into turbulent gaseous cross flows for different density ratios is presented. A finite volume, balanced force fractional step flow solver to solve the Navier-Stokes equations is employed and coupled to a Refined Level Set Grid method to follow the phase interface. To enable the simulation of atomization of high density ratio fluids, we ensure discrete consistency between the solution of the conservative momentum equation and the level set based continuity equation by employing the Consistent Rescaled Momentum Transport (CRMT) method. The impact of different inflow jet boundary conditions on different jet properties including jet penetration is analyzed and results are compared to those obtained experimentally by Brown & McDonell(2006). In addition, instability analysis is performed to find the most dominant insta- bility mechanism that causes the liquid jet to breakup. Linear instability analysis is achieved using linear theories for Rayleigh-Taylor and Kelvin- Helmholtz instabilities and non-linear analysis is performed using our flow solver with different inflow jet boundary conditions.

  10. 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.

  11. 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.

  12. Microfluidic liquid jet system with compatibility for atmospheric and high-vacuum conditions.

    PubMed

    Trebbin, Martin; Krger, Kilian; DePonte, Daniel; Roth, Stephan V; Chapman, Henry N; Frster, Stephan

    2014-05-21

    We present microfluidic chip based devices that produce liquid jets with micrometer diameters while operating at very low flow rates. The chip production is based on established soft-lithographical techniques employing a three-layer design protocol. This allows the exact, controlled and reproducible design of critical parts such as nozzles and the production of nozzle arrays. The microfluidic chips reproducibly generate liquid jets exiting at perfect right angles with diameters between 20 ?m and 2 ?m, and under special circumstances, even down to 0.9 ?m. Jet diameter, jet length, and the domain of the jetting/dripping instability can be predicted and controlled based on the theory for liquid jets in the plate-orifice configuration described by Gan-Calvo et al. Additionally, conditions under which the device produces highly reproducible monodisperse droplets at exact and predictable rates can be achieved. The devices operate under atmospheric and under vacuum conditions making them highly relevant for a wide range of applications, for example, for free-electron lasers. Further, the straightforward integration of additional features such as a jet-in-jet is demonstrated. This device design has the potential to integrate more features based on established microfluidic components and may become a standard device for small liquid jet production. PMID:24671443

  13. Stability analysis of an electrified liquid jet in the presence of an externally coflowing liquid

    NASA Astrophysics Data System (ADS)

    Gundabala, Venkat; Modi, Vikrant; Gundabala microfluidics Group Team

    2015-03-01

    Traditionally, electrospinning and electrospray are carried out with either air or vacuum as external medium. Recently, it has been shown that electrospray can be successfully implemented in the presence of an external flowing liquid. We envisage that implementation of electrospinning process in the presence of an external liquid coflowing with the electrospinning solution will allow greater control on the fiber deposition and morphology. In the present work, to gain fundamental understanding on the behaviour of an electrified liquid jet in the presence of an externally coflowing liquid, we perform stability analysis on the system. The classical Rayleigh-Plateau instability and an electrically induced axisymmetric instability were identified. The effect of the viscosity, velocity, and permittivity of the external liquid on the two instabilities was studied. It was found that both the growth rate and the critical wavenumbers were strongly influenced by the above parameters. An operating diagram predicting the transition from drop generation mode to fiber generation mode as a function of external liquid properties is generated.

  14. 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.

  15. Multi-zone behavior of transverse liquid jet in high-speed flow

    NASA Astrophysics Data System (ADS)

    Chen, T. H.; Smith, C. R.; Schommer, D. G.; Nejad, A. S.

    1993-01-01

    The behavior of a liquid-fuel spray transversely injected into a uniform high-speed crossflow is characterized utilizing a laser-sheet imaging method. The dependence of jet penetration upon jet-to-crossflow momentum ratio is examined by varying the ratio from 3 to 45. A detailed comparison of the jet trajectories (penetration profiles) measured with those predicted by available correlation functions showed gross discrepancies.

  16. Shock attenuation in two-phase (gas-liquid) jets for inertial fusion applications

    NASA Astrophysics Data System (ADS)

    Lascar, Celine C.

    Z-Pinch IFE (Inertial Fusion Energy) reactor designs will likely utilize high yield targets ( 3 GJ) at low repetition rates ( 0.1 Hz). Appropriately arranged thick liquid jets can adequately protect the cavity walls from the target X-rays, ions, and neutrons. However, the shock waves and mechanical loadings produced by rapid heating and evaporation of incompressible liquid jets may be challenging to accommodate within a small reactor cavity. This investigation examines the possibility of using two-phase compressible (liquid/gas) jets to protect the cavity walls in high yield IFE systems, thereby mitigating the mechanical consequences of rapid energy deposition within the jets. Two-phase, free, vertical jets with different cross sections (planar, circular, and annular) were examined over wide ranges of liquid velocities and void fractions. The void fraction and bubble size distributions within the jets were measured; correlations to predict variations of the slip ratio and the Sauter mean diameter were developed. An exploding wire system was used to generate a shock wave at the center of the annular jets. Attenuation of the shock by the surrounding single- or two-phase medium was measured. The results show that stable coherent jets can be established and steadily maintained over a wide range of inlet void fractions and liquid velocities, and that significant attenuation in shock strength can be attained with relatively modest void fractions ( 1%); the compressible two-phase jets effectively convert and dissipate mechanical energy into thermal energy within the gas bubbles. The experimental characteristics of single- and two-phase jets were compared against predictions of a state-of-art CFD code (FLUENTRTM ). The data obtained in this investigation will allow reactor system designers to predict the behavior of single- and two-phase jets and quantify their effectiveness in mitigating the consequences of shock waves on the cavity walls in high yield IFE systems.

  17. On the numerical solution of liquid film and jet flows

    NASA Astrophysics Data System (ADS)

    Pacheco, Jose Rafael

    1999-09-01

    The analysis of many fluid flows of practical interest such as liquid films and jets are complicated by the presence of free surface boundaries. Exact solutions are scare and increasingly, numerical methods are being applied to predict local flow properties and hydrodynamic structure. Like the unknown pressure and velocities, the shape and the position of the boundary must be determined as part of the solution. This information is needed for the design of cooling schemes in high-temperature applications, to optimize heat treatment of metals, and to improve material production processes. The objective of this research is to develop an accurate and efficient numerical method that can be applied to the simulation of free surface flow problems, i.e. horizontal jets, impinging jets and films with and without rotation. The governing equations are written in terms of primitive variables and solved by the non-staggered grid fractional step method when hydraulic jumps are absent in the flow. The physical domain is transformed to a rectangle for two-dimensional problems or a parallelepiped for three- dimensional problems by means of a numerical mapping technique. The pressure Poisson equation is formulated in the same manner as on a staggered grid and solved with a SOR method. The location of the phase boundary is accomplished by applying both, the normal-stress condition or the kinematic boundary condition depending on the physical force that regulates the behavior of the flow. The method was applied to solve plane Newtonian jet flows. The numerical predictions are in good agreement with the results based on the finite and spectral element methods as well as the finite difference streamfunction vorticity formulation. The boundary conditions at the free surface are more accurately satisfied when compared with available data. In the presence of hydraulic jumps, the problem is modeled using the shallow-water approximation and the governing equations are solved using shock capturing schemes. The governing equations were discretized using both the l and flux vector splitting methods. The finite difference technique incorporates a numerical mapping so that the flow regime is transformed to a regular domain for numerical integration. These methods were applied for the simulation of a thin film flowing radially outward on a stationary disk. In this formulation, a first-order forward difference approximation for the time derivative was used. The results showed the location of the hydraulic jump could be predicted. Among the advantages of the non-staggered grid fractional step method are: the accuracy is second order in space and time, it can handle three-dimensional problems in complex geometries such as flows that turn 90, it is possible to perform large eddy simulations and to implement turbulent models, and because of local orthogonality at the surface, melting problems can be studied with this method. The flux vector splitting technique can be used to analyze thin films with singularities present in the flow field.

  18. Cryogenic liquid-jet breakup in two-fluid atomizers

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1991-01-01

    A two-fluid atomizer was used to study the breakup of liquid-nitrogen jets in nitrogen, argon, and helium atomizing gas flows. A scattered-light scanner particle sizing instrument previously developed at NASA Lewis Research Center was further developed and used to determine characteristic drop diameters for the cryogenic sprays. In the breakup regime of aerodynamic-stripping, i.e., sonic-velocity conditions, the following correlation of the reciprocal Sauter mean diameter, D(sub 32)exp -1, with the atomizing-gas flowrate, W(g), was obtained: D(sub 32)exp -1 = k(sub c)(W(g)exp 1.33), where k(sub c) is a proportionality constant evaluated for each atomizing gas. Values of k(sub c) = 120, 220, and 1100 were obtained for argon, nitrogen, and helium gasflows, respectively. The reciprocal Sauter mean diameter and gas flowrate have the units of 1/cm and g/sec, respectively. In the regime of capillary-wave breakup, or subsonic conditions, it was found that D(sub 32)exp -1 = k(g)(W(g)exp 0.75), where k = 270, 390, and 880 for argon, nitrogen, and helium gasflows, respectively.

  19. Analysis of liquid-metal-jet impingement cooling in a corner region and for a row of jets

    NASA Technical Reports Server (NTRS)

    Siegel, R.

    1975-01-01

    A conformal mapping method was used to analyze liquid-metal-jet impingement heat transfer. The jet flow region and energy equation are transformed to correspond to uniform flow in a parallel plate channel with nonuniform heat addition along a portion of one wall. The exact solution for the wall-temperature distribution was obtained in the transformed channel, and the results are mapped back into the physical plane. Two geometries are analyzed. One is for a single slot jet directed either into an interior corner formed by two flat plates, or over the external sides of the corner; the flat plates are uniformly heated, and the corner can have various included angles. The heat-transfer coefficient at the stagnation point at the apex of the plates is obtained as a function of the corner angle, and temperature distributions are calculated along the heated walls. The second geometry is an infinite row of uniformly spaced parallel slot jets impinging normally against a uniformly heated plate. The heat-transfer behavior is obtained as a function of the spacing between the jets. Results are given for several jet Peclet numbers from 5 to 50.

  20. Experimental investigations of steady and dynamic behavior of transverse liquid jets

    NASA Astrophysics Data System (ADS)

    Elshamy, Omar M.

    The injection of a liquid jet into a crossflow of air provides a means of higher penetration and rapidly mixing liquid fuel and air for combustion applications. The structure of the spray, formed is investigated. To attain this goal, the problem is divided into the following tasks which involve: (1) characterize the penetration, breakup, atomization, mixing, and breakup of liquid jet injected into crossflow at conditions relevant to real engine conditions, (2) establish an understanding of the structure of that transverse jet near the injection point, and (3) study the dynamics behavior of the transverse jet and propose new method to control the transverse liquid jet in crossflow. Two breakup modes have been observed, column and surface breakup. The agreement between the breakup map developed in the present study with the existing ones is quite good. The agreement between the PIV and LDV measurements was good and within 10% accuracy. PIV probe has been proven as a good tool to capture the aero-structure of spray generated by liquid jet in cross flows by comparing its results with the corresponding LDV results. Droplet velocity exhibits a minimum in the spray core. As the momentum ratio increases, the transverse location as well as the droplet velocity of the spray core increases, while the droplet velocity at the outer periphery decreases. Elevating the ambient pressure slightly decreases the penetration and decreases the spray spread. At higher ambient pressure, shorter axial distance is required for the droplet to follow the airflow. Mechanically exciting the transverse liquid jet can have a significant effect on the mixing, spreading, and penetration of the liquid jet in crossflow. The penetration of the jet may increase by more than 40% while the spread of the jet by 100% at an axial location of about ten diameters downstream of the injection point. The optimum excitation Strouhal number is about 0.0047, at which homogenous droplet average velocity distribution and maximum interaction between the liquid jet and the crossflow are observed. Novel correlations that describe the outer and inner boundaries of the dynamic jet are developed.

  1. 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.

  2. 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.

  3. Experimental investigation of cavity stability for a gas-jet penetrating into a liquid sheet

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Chen, Wenyu; Hu, Liang; Xie, Haibo; Fu, Xin

    2015-08-01

    Generating stable cavity without droplets splatter is commonly required when process of a gas-jet penetrating into a liquid sheet is implemented in various industrial applications. In this study, experiments were carried out to investigate the cavity stability under different penetrating parameters, including different nozzle diameters, liquid sheet thicknesses, gas flow rates, and jet heights. When keeping other parameters fixed but moving the nozzle close to the liquid sheet surface, it was found that the cavity was frequently disturbed by the wall-jet and became unstable accompanied with droplets splatter at too low jet heights. Images of the cavities were captured by high speed video camera to study cavity performances, including its size, surface morphology, and droplets splatter. It was further found that violent surface waves were commonly generated by the strong wall-jet disturbance at low jet heights and droplets splatter was caused as long as Rayleigh instability happened due to higher frequency oscillation of the surface wave. Critical jet heights causing cavity stability transition were studied for different penetrating conditions, which were further expressed by a local modified Froude number as a normalized formulation. Curve fitting illustrating the conditions to generate stable penetrating cavities was given at last to provide guides for the jet controls in industry.

  4. Detailed Numerical Simulations of the Primary Atomization of a Turbulent Liquid Jet in Crossflow

    NASA Astrophysics Data System (ADS)

    Herrmann, Marcus

    2008-11-01

    Atomizing liquids by injecting them into crossflows is a common approach to generate fuel sprays in gas turbines and augmentors. While correlations derived from experimental data exist for the jet penetration, predicting the drop size distribution resulting from the primary breakup of the liquid jet is a more challenging task. This is in part due to the fact that often, several different atomization mechanisms occur on the jet's surface at the same time. Detailed numerical simulations can help study the simultaneously occurring mechanisms, even in regions of the liquid jet, where traditional experimental methods cannot observe the phase interface dynamics. To handle the large range of time and length scales that occur during atomization, we employ the Refined Level Set Grid (RLSG) method, coupled to a finite volume, balanced force, incompressible LES flow solver. We will present results for a momentum flux ratio 6.6 turbulent liquid jet of Weber number 330 and Reynolds number 14,000 injected into a gaseous crossflow of Reynolds number 740,000, taking the detailed geometry of the injector into account. The physical mechanisms causing the initial breakup of the jet, the resulting grid dependent/independent drop size distributions, and the jet penetration will be discussed.

  5. 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.

  6. Hydraulic jumps with corners due to obliquely inclined circular liquid jets

    NASA Astrophysics Data System (ADS)

    Kate, R. P.; Das, P. K.; Chakraborty, Suman

    2007-05-01

    We have discovered that hydraulic jumps corresponding to obliquely inclined circular liquid jets, under certain conditions of impingement, confer a series of interesting flow patterns (including jumps with corners). These patterns are markedly different from the regular elliptical (or oblate) shaped jump profiles that are commonly observed with higher angles of jet inclination. These patterns are attributed to the changes in the spreading flow profile due to jet-jump interaction at relatively lower jet inclination angles. The irregular shaped jump profiles, close to the critical angle of jet inclination, are mathematically characterized by introducing the concept of an equivalent jump radius. These theoretical predictions match excellently with the experimental findings. A phenomenological explanation is also provided by drawing analogies from shock-wave interactions in compressible fluid mechanics and from twin-jet interaction mechanisms.

  7. Cavitation in a Two-Dimensional Nozzle and Liquid Jet Atomization

    NASA Astrophysics Data System (ADS)

    Sou, Akira; Tomiyama, Akio; Hosokawa, Shigeo; Nigorikawa, Shinji; Maeda, Tatsutoshi

    Cavitation in nozzles of liquid injectors is known to affect the atomization of a discharged liquid jet. To understand how cavitating flow in a nozzle enhances the liquid jet atomization, liquid velocity distribution of cavitating flow in a two-dimensional transparent nozzle was measured using a Laser Doppler Velocimetry (LDV) system. As a result, the following conclusions were obtained: (1) The inception of cavitation occurs near the outer edge of separated boundary layer (SBL), where the time-averaged local velocity takes the highest value and the time-averaged pressure is almost equal to the vapor saturation pressure. (2) When the cavitation number ? is greater than 0.78 (in no cavitation and developing cavitation regimes), the reattachment of SBL occurs in the middle of the nozzle. A large velocity fluctuation, which appears just downstream of SBL, decreases near the nozzle exit. Hence the wavy jet is formed in these regimes. (3) For ? ? 0.65 (in super cavitation regime), the lateral flow directing from the core region toward the side walls just upstream of the nozzle exit is a major cause of the increase in the spray angle and drastic enhancement of liquid jet atomization. The strong turbulence just upstream of the exit must play an important role in the formation of ligaments on liquid jet interface.

  8. Quantitative liquid jet instability measurement system using asymmetric magnification and digital image processing

    NASA Astrophysics Data System (ADS)

    Collicott, Steven H.; Zhang, Shucheng; Schneider, Steven P.

    1994-04-01

    A new technique for measuring the growth of instabilities on the surface of liquid jets flowing into gas is demonstrated. A collimated beam of white light illuminates the jet from behind, forming a shadow image. A pair of cylindrical lenses are arranged to provide different magnifications in the streamwise and cross-stream directions. A number of streamwise diameters and one cross-stream diameter are thus captured with maximum resolution in a single image on a charge-coupled device (CCD) electronic camera. A short-duration spark is used to freeze the jet motion. A mask representing the theoretical edge-response of the imaging system is digitally convolved with the cross-stream gray scale data to obtain sub-pixel resolution of the jet edge profile. The method is demonstrated using the well-known capillary jet instability and a ratio of streamwise to cross-stream magnifications of 40. Well-resolved single images show the development of the instability from small perturbations through the formation of the first drop. The system forms an accurate automated method of measuring the development of liquid jet instabilities. It can readily be applied to practical problems including liquid jet atomization.

  9. 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.

  10. Electrohydrodynamic inter-electrode flow and liquid jet characteristics in charge injection atomizers

    NASA Astrophysics Data System (ADS)

    Kourmatzis, A.; Shrimpton, J. S.

    2014-03-01

    The governing equations of electrohydrodynamics pertinent to forced and free electroconvection have been examined in the context of an array of charge injection atomization systems for dielectric electrically insulating liquids. The underlying physics defining their operation has been described further by linking the internal charge injection process inside the atomizer with resulting charged liquid jet characteristics outside it. A new nondimensional number termed the electric jet Reynolds number Re E,j is required to describe charge injection systems universally. The electric jet Reynolds number Re E,j varies linearly with the inter-electrode gap electric Reynolds number Re E, and the inter-electrode gap Reynolds number Re E varies linearly with the conventional liquid jet Reynolds number Re j. These variations yield two new seemingly universal constants relevant in the description of two-phase charge injection systems. The first constant being which physically represents the ratio of jet to inter-electrode gap electric field multipled by a nondimensional geometric factor while it may also be physically seen as a forced flow charge injection strength term, analogous to the `C' term described in single-phase free electroconvection. The second constant being which physically represents the ratio of inter-electrode gap ionic drift velocity, to the liquid jet velocity, multipled by a nondimensional geometric factor. These scalings have been found to be valid for charge injection systems regardless of fuel, voltage pulsation, electrode shape, orifice diameter, and inter-electrode gap length.

  11. Transient behavior of liquid jets injected normal to a high velocity gas stream

    NASA Astrophysics Data System (ADS)

    Less, D. M.

    The transient effects of the breakup and atomization of liquid jets in a crossflow on the size of droplets within the spray plume was experimentally determined. Water and water/methanol mixtures were injected normal to a high velocity air stream at Mach numbers of 0.48 and 3.0 with ambient stagnation temperature and respective stagnation pressures of 1.4 and 4.3 atm. The liquids were injected at liquid-to-gas momentum flux ratios ranging from 4 to 12. Droplet size distributions were obtained using a Fraunhofer diffraction technique at sampling rates of up to 9 kHz. Liquid mass flow rates were inferred from measurements of the extinction of a laser beam traversing the plume. The droplet sizes were found to fluctuate with frequencies of the order of 1 to 10 kHz. The fluctuations were characterized by a sudden and relatively brief increase in the mean diameter of the droplets caused by the passage of fractured clumps through the spray plume. Also evident in the droplet size distributions was the very small size of the droplets that had been sheared off the windward surfaces of the jet. The jet fracture frequency was related to the frequency of waves propagating along the initial jet column. The column waves are postulated to have been caused by jet perturbations created by vortices in the air flow around the jet column.

  12. Unsteady penetration of a target by a liquid jet.

    PubMed

    Uth, Tobias; Deshpande, Vikram S

    2013-12-10

    It is widely acknowledged that ceramic armor experiences an unsteady penetration response: an impacting projectile may erode on the surface of a ceramic target without substantial penetration for a significant amount of time and then suddenly start to penetrate the target. Although known for more than four decades, this phenomenon, commonly referred to as dwell, remains largely unexplained. Here, we use scaled analog experiments with a low-speed water jet and a soft, translucent target material to investigate dwell. The transient target response, in terms of depth of penetration and impact force, is captured using a high-speed camera in combination with a piezoelectric force sensor. We observe the phenomenon of dwell using a soft (noncracking) target material. The results show that the penetration rate increases when the flow of the impacting water jet is reversed due to the deformation of the jet-target interface--this reversal is also associated with an increase in the force exerted by the jet on the target. Creep penetration experiments with a constant indentation force did not show an increase in the penetration rate, confirming that flow reversal is the cause of the unsteady penetration rate. Our results suggest that dwell can occur in a ductile noncracking target due to flow reversal. This phenomenon of flow reversal is rather widespread and present in a wide range of impact situations, including water-jet cutting, needleless injection, and deposit removal via a fluid jet. PMID:24277818

  13. Experimental Investigation of Jet-Induced Mixing of a Large Liquid Hydrogen Storage Tank

    NASA Technical Reports Server (NTRS)

    Lin, C. S.; Hasan, M. M.; Vandresar, N. T.

    1994-01-01

    Experiments have been conducted to investigate the effect of fluid mixing on the depressurization of a large liquid hydrogen storage tank. The test tank is approximately ellipsoidal, having a volume of 4.89 m(exp 3) and an average wall heat flux of 4.2 W/m(exp 2) due to external heat input. A mixer unit was installed near the bottom of the tank to generate an upward directed axial jet flow normal to the liquid-vapor interface. Mixing tests were initiated after achieving thermally stratified conditions in the tank either by the introduction of hydrogen gas into the tank or by self-pressurization due to ambient heat leak through the tank wall. The subcooled liquid jet directed towards the liquid-vapor interface by the mixer induced vapor condensation and caused a reduction in tank pressure. Tests were conducted at two jet submergence depths for jet Reynolds numbers from 80,000 to 495,000 and Richardson numbers from 0.014 to 0.52. Results show that the rate of tank pressure change is controlled by the competing effects of subcooled jet flow and the free convection boundary layer flow due to external tank wall heating. It is shown that existing correlations for mixing time and vapor condensation rate based on small scale tanks may not be applicable to large scale liquid hydrogen systems.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  15. 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.

  16. 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.

  17. 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.

  18. Unsteady penetration of a target by a liquid jet

    PubMed Central

    Uth, Tobias; Deshpande, Vikram S.

    2013-01-01

    It is widely acknowledged that ceramic armor experiences an unsteady penetration response: an impacting projectile may erode on the surface of a ceramic target without substantial penetration for a significant amount of time and then suddenly start to penetrate the target. Although known for more than four decades, this phenomenon, commonly referred to as dwell, remains largely unexplained. Here, we use scaled analog experiments with a low-speed water jet and a soft, translucent target material to investigate dwell. The transient target response, in terms of depth of penetration and impact force, is captured using a high-speed camera in combination with a piezoelectric force sensor. We observe the phenomenon of dwell using a soft (noncracking) target material. The results show that the penetration rate increases when the flow of the impacting water jet is reversed due to the deformation of the jet–target interface––this reversal is also associated with an increase in the force exerted by the jet on the target. Creep penetration experiments with a constant indentation force did not show an increase in the penetration rate, confirming that flow reversal is the cause of the unsteady penetration rate. Our results suggest that dwell can occur in a ductile noncracking target due to flow reversal. This phenomenon of flow reversal is rather widespread and present in a wide range of impact situations, including water-jet cutting, needleless injection, and deposit removal via a fluid jet. PMID:24277818

  19. 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

  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. Effect of mass-velocity on liquid jet atomization in Mach 1 gasflow

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1988-01-01

    Interacting two-phase flow in four differently sized pneumatic two-fluid atomizers was investigated to determine the effect of gas mass-velocity on the Sauter mean diameter of sprays produced by small diameter liquid jets breaking up in high velocity gas flow. 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. A scattered-light scanner, developed at NASA Lewis Research Center, was used to measure the Sauter mean diameter, D sub 32, which was correlated with nitrogen gas mass-velocity to give the following expression: D (sup -1)(sub 32) = 11.7(rho (sub n) V (sub n)) (sup 1.33). The exponent 1.33 for the gas mass-velocity is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime.

  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. Coaxial atomization of a round liquid jet in a high speed gas stream: A phenomenological study

    NASA Astrophysics Data System (ADS)

    Mayer, W. O. H.

    1994-05-01

    Coaxial injectors have proven to be advantageous for the injection, atomization and mixing of propellants in cryogenic H2/O2 rocket engines. Thereby, a round liquid oxygen jet is atomized by a fast, coaxial gaseous hydrogen jet. This article summarizes phenomenological studies of coaxial spray generation under a broad variation of influencing parameters including injector design, inflow, and fluid conditions. The experimental investigations, performed using spark light photography and high speed cinematography in a shadow graph setup as main diagnostic means, illuminate the most important processes leading to atomization. These are identified as turbulence in the liquid jet, surface instability, surface wave growth and droplet detachment. Numerical simulations including free surface flow phenomena are a further diagnostic tool to elucidate some atomization particulars. The results of the study are of general importance in the field of liquid atomization.

  4. Numerical Simulation of the Instability of an Inviscid Liquid Jet in a Coflowing Compressible Airstream

    NASA Technical Reports Server (NTRS)

    Li, H. -S.

    1994-01-01

    The nonlinear interfacial instability of a liquid jet in a coflowing compressible airstream is studied numerically. A high-resolution scheme which has second-order accuracy in space and time is coupled with a Lagrangian marker particle algorithm to visualize the large-scale motion of the interfaces in compressible flow. A numerical algorithm based on an approximate equation of state of a compressible liquid is developed to allow this two-fluid system to be governed by the nonlinear unsteady Euler equations in conservative form. The initial growth of small disturbances given by the simulations agrees well with linear theory. The process of jet disruption in compressible flow is demonstrated to consist of the formation of liquid spikes, interweaving of the gas and liquid and stretching and detachment of the liquid main center core.

  5. 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 boundary conditions at the river mouth and those of the receiving water. The relationships can be used for modern systems, but can also help to put reasonable bounds on paleo-hydraulic setting. References Dai, A. & Garcia, M. H. (2010). Energy Dissipative Plunging Flows. Journal of Hydraulic Engineering, 136(8), 519-523. Fang, X. & Stefan, H. G. (1991). Integral Jet Model for Flow from an Open Channel into a Shallow Lake or Reservoir. St. Anthony Falls Hydraulic Laboratory. Fang, X. & Stefan, H. G. (2000). Dependence of dilution of a plunging discharge over a sloping bottom on inflow conditions and bottom friction. Journal of Hydraulic Research, 38(1), 15-25. Lamb, M. P., McElroy, B., Kopriva, B., Shaw, J., & Mohrig, D. (2010). Linking river-flood dynamics to hyperpycnal-plume deposits: Experiments, theory, and geological implications. Geological Society of America Bulletin, 122(9/10), 1389-1400. Parker, G. & Toniolo, H. (2007). Note on the Analysis of Plunging of Density Flows. Journal of Hydraulic Engineering, 133(6), 690-694.

  6. Drop Size Distributions of Aerated Liquid Jets injected in Subsonic Crossflow

    NASA Astrophysics Data System (ADS)

    Adebayo, Adegboyega; Sallam, Khaled; Lin, Kuo-Cheng; Carter, Campbell

    2013-11-01

    An Experimental investigation of the breakup of aerated liquid jets in subsonic crossflow is described. Test conditions include crossflow Mach numbers of 0.3 and 0.6, Gas-to-liquid ratio of 0%, 4%, and 8%. Double pulsed digital holography was used to investigate the spray characteristics at downstream distances of 25, 50, and 100 jet diameters. The holograms are analyzed using image-processing algorithms to yield information about the drop sizes, drop velocities, and mass fluxes. Different drop size distributions are tested and compared including Rosin-Rammler distribution, log-normal distribution, and Simmons' universal root-normal distribution.

  7. Axisymmetric confined turbulent jet directed towards the liquid surface from below

    NASA Technical Reports Server (NTRS)

    Hasan, Mohammad M.; Lin, Chin-Shun

    1988-01-01

    A numerical simulation is presented of an axisymmetric turbulent jet discharging axially from below into a cylindrical tank and directed towards the liquid vapor interface. The liquid vapor interface is assumed to be flat and shear free. The k-epsilon turbulence model is used to calculate the eddy viscosity. The turbulence intensity distribution and the length scale associated with the k-epsilon model are calculated as functions of jet flow rates and systems parameters. Numerical results are compared with appropriate experimental data. The problems associated with the free surface boundary conditions for the turbulent quantities are discussed.

  8. Axisymmetric confined turbulent jet directed towards the liquid surface from below

    NASA Technical Reports Server (NTRS)

    Hasan, Mohammad M.; Lin, Chin-Shun

    1989-01-01

    A numerical simulation is presented of an axisymmetric turbulent jet discharging axially from below into a cylindrical tank and directed towards the liquid vapor interface. The liquid vapor interface is assumed to be flat and shear free. The k-epsilon turbulence model is used to calculate the eddy viscosity. The turbulence intensity distribution and the length scale associated with the k-epsilon model are calculated as functions of jet flow rates and systems parameters. Numerical results are compared with appropriate experimental data. The problems associated with the free surface boundary conditions for the turbulent quantities are discussed.

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

    SciTech Connect

    Thring, T.; Rutishauser, S.; Stampanoni, M.; Institute for Biomedical Engineering, Swiss Federal Institute of Technology, Zurich ; Zhou, T.; Lundstrm, 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/ssr, 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.

  10. 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

  11. Numerical investigation on the primary breakup of an inelastic non-Newtonian liquid jet with inflow turbulence

    NASA Astrophysics Data System (ADS)

    Zhu, Chengxiang; Ertl, Moritz; Weigand, Bernhard

    2013-08-01

    Direct Numerical Simulations of the primary breakup of an inelastic non-Newtonian liquid jet with inflow turbulence are presented in this paper. The jet's structure, surface behavior, non-Newtonian characteristics as well as its specific breakup mechanism are investigated and discussed. The shear thinning viscosity of the liquid phase plays an important role during jet injection resulting in circumferential rotation of interfacial waves. Streamwise contra-rotating vortex pairs as well as triple vortex structures are observed in the liquid phase. The local Ohnesorge number, which has a branch-structure distribution in the liquid phase before disintegration, is found to be 30% smaller in regions near the nozzle exit and in the shear layer than in the jet tip, suggesting a clear non-Newtonian influence. A cavity breakup mechanism for this type of non-Newtonian jet is identified and explained, giving a new perspective for jet disintegration analysis.

  12. 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.

  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. 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.

  15. Optimization of drug viscosity used in gas-powered liquid jet injectors.

    PubMed

    Portaro, Rocco; Nakayama, Haruka; Hoi Dick Ng

    2015-08-01

    This paper describes the effect of drug viscosity on the performance of gas powered liquid jet injectors. The analysis is accomplished utilizing a Computational Fluid Dynamics (CFD) model that obtains the stagnation pressure at the nozzle outlet. The technique is based on previous work used to predict gas power driven injector piston velocity with time. The results depict the variation in average and peak injector stagnation pressure for three different driven pressures; driving injections which vary from 0.2 cP to 87 cP in viscosity. Furthermore, a numerical representation of jet shape is also obtained to verify the effect of viscosity on jet geometry. These results demonstrate that increasing viscosity by 10 times that of water produces only a slight decrease in injector stagnation pressure and produces jets with greater confinement, which will display better characteristics for puncturing the skin. PMID:26737990

  16. Flow of a two-dimensional liquid metal jet in a strong magnetic field.

    SciTech Connect

    Reed, C.B.; Molokov, S.

    2002-02-22

    Two-dimensional, steady flow of a liquid metal slender jet pouring from a nozzle in the presence of a transverse, nonuniform magnetic field is studied. The surface tension has been neglected, while gravity is shown to be not important. The main aim of the study is to evaluate the importance of the inertial effects. It has been shown that for gradually varying fields characteristic for the divertor region of a tokamak, inertial effects are negligible for N > 10, where N is the interaction parameter. Thus the inertialess flow model is expected to give good results even for relatively low magnetic fields and high jet velocity. Simple relations for the jet thickness and velocity have been derived. The results show that the jet becomes thicker if the field increases along the flow and thinner if it decreases.

  17. Model validation image data for breakup of a liquid jet in crossflow: part I

    NASA Astrophysics Data System (ADS)

    Sedarsky, David; Paciaroni, Megan; Berrocal, Edouard; Petterson, Per; Zelina, Joseph; Gord, James; Linne, Mark

    2010-08-01

    We have applied three different imaging diagnostics: particle imaging velocimetry, high-speed shadowgraphy, and ballistic imaging, to observe the breakup of a liquid jet in a crossflow of air under a variety of conditions. The experimental system was designed to provide well-controlled conditions with minimal amounts of turbulence in the liquid jet and the gaseous crossflow. A variety of Weber numbers and momentum flux ratios were studied in order to provide a sizable data set for the validation of computational models. This paper briefly describes the three spray imaging techniques, outlines the results obtained to-date, and tabulates image statistics for each of ten spray conditions at varying distances from the spray nozzle orifice. The end result is a first installment in what will become a comprehensive model validation data set for jets in crossflow for use by computational fluid dynamics modelers.

  18. 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.

  19. 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.

  20. Self-destabilizing mechanism of a laminar inviscid liquid jet issuing from a circular nozzle

    NASA Astrophysics Data System (ADS)

    Umemura, Akira

    2011-04-01

    A laminar inviscid liquid (typically water) jet issuing from a circular nozzle into otherwise quiescent air disintegrates into droplets periodically at a distance from the nozzle. The Plateau-Rayleigh instability theory and others cannot determine this breakup length because they do not have any logic that determines the initial amplitude of the unstable wave responsible for the breakup. In this paper, a closed spatial evolution solution is derived for a uniformly issued liquid jet by applying a theory that identifies the origin of the unstable wave. This solution describes the self-destabilizing mechanism of the liquid jet in the steady breakup state, showing that the initial amplitude of the unstable wave is determined by the capillary wave with upstream propagating speed that is created by the tip contraction at every breakup. Finally, the developed theory is extended to allow for the self-destabilizing mechanism of a liquid jet issuing from a long nozzle, which initially has a parabolic velocity profile and results in a long breakup length.

  1. 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.

  2. 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.

  3. A Particle-Tracking-Velocimetry (PTV) Investigation of Liquid Injection in a DC Plasma Jet

    NASA Astrophysics Data System (ADS)

    Damiani, David; Tarlet, Dominique; Meillot, Erick

    2014-02-01

    The present article describes experimental results of liquid injection in a thermal plasma jet by particle-tracking velocimetry (PTV). This technique delivers an in-situ real-time analysis of the liquid breakup and measures the velocities and the trajectories of the particles. The observations were done within the 10 mm surrounding the injection location where the plasma brightness is considerable. First, a validation of the proposed investigation method was carried out in a slower plasma jet. Subsequently, PTV measurements within faster plasma jets, resulting in a set of trajectories, were compared with trajectories achieved through optical diagnostics based on a simple shadow-graph technique proposed by Damiani et al. [Injection d'un liquide au sein d'un jet plasma thermique: optimisation de la trajectoire des particules, Proceedings of Congrs Francophone de Techniques Laser, CFTL 2010, Vandoeuvre ls nancy, France, 2010 (in French)]. These trajectories indicated that a higher plasma flow rate was required to spray all droplet sizes in the axis of the flow, thereby enabling an optimal spraying (then coating) application for producing nanostructured thin layers. This study showed that the liquid injection parameters are of main importance to obtain optimal injection and plasma parameters to achieve the required coating properties.

  4. An experimental investigation on the interaction of hydraulic jumps formed by two normal impinging circular liquid jets

    NASA Astrophysics Data System (ADS)

    Kate, R. P.; Das, P. K.; Chakraborty, Suman

    The flow field due to two normal impinging liquid jets is different from the flow field associated with a single normal impinging liquid jet, and even from the flow field around two normal impinging compressible fluid jets. Depending on the spacing between the two jets and their relative strengths, different kinds of hydraulic jump interactions are possible, resulting in a variety of flow patterns. The present study experimentally elucidates the jump--jump interactions formed in such cases, for different values of inter-jet spacings and for different strengths of the individual jets. Analogous flow fields associated with the interactions between a single impinging jet and a fence are also studied to allow convenient experimental flow vizualizations.

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

    NASA Astrophysics Data System (ADS)

    Gomes, R. B.; Fernandes, H.; Silva, C.; Borba, D.; Carvalho, B.; Varandas, C.; Lielausis, O.; Klyukin, A.; Platacis, E.; Mikelsons, A.; Platnieks, I.

    2006-12-01

    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.

  6. 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.

  7. 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.

  8. Study on bubble sizes in a down-flow liquid jet gas pump

    NASA Astrophysics Data System (ADS)

    Wu, Y. L.; Xiang, Q. J.; Li, H.; Chen, S. X.

    2012-11-01

    In this paper the liquid jet gas pump as an important gas-liquid contactor is investigated on bubble sizes. Its internal mixed effect is influenced by gas holdup, bubble size distribution and interfacial area. To improve the mixed effect, experiment investigations have been carried out in a modified down-flow liquid jet gas pump with special emphasis on gas distribution. The mixing tube and diffuser are made of transparent Perspex for visual observation. Bubble diameters in the diffuser have been measured by photographic and capillary method at different operating conditions. Under the same Reynolds number of orifice, about 80% of the bubble diameters range from 0.6 mm to 1.3 mm, which has no obvious effect on the gas-liquid flow rate ratio. The average bubble diameter increases by the decrease of Orifice Reynolds number at the same gas-liquid flow rate ratio (lower gas-liquid rate ratio), the maximal bubble size can reach 3 mm. With the decrease of gas-liquid flow rate ratio, gas gathers together in the wall and the stream appears non uniform, the sampling test shows that the bubble diameters have a small diminution. It is found experimentally that the bubble diameters are strongly dependent on Orifice Reynolds number and the bubble distribution is affected by gas-liquid flow rate ratio

  9. Experimental study on plunging breaking waves in deep water

    NASA Astrophysics Data System (ADS)

    Lim, Ho-Joon; Chang, Kuang-An; Huang, Zhi-Cheng; Na, Byoungjoon

    2015-03-01

    This study presents a unique data set that combines measurements of velocities and void fraction under an unsteady deep water plunging breaker in a laboratory. Flow properties in the aerated crest region of the breaking wave were measured using modified particle image velocimetry (PIV) and bubble image velocimetry (BIV). Results show that the maximum velocity in the plunging breaker reached 1.68C at the first impingement of the overturning water jet with C being the phase speed of the primary breaking wave, while the maximum velocity reached 2.14C at the beginning of the first splash-up. A similarity profile of void fraction was found in the successive impinging and splash-up rollers. In the highly foamy splashing roller, the increase of turbulent level and vorticity level were strongly correlated with the increase of void fraction when the range of void fraction was between 0 and 0.4 (from the trough level to approximately the center of the roller). The levels became constant when void fraction was greater than 0.5. The mass flux, momentum flux, kinetic energy, potential energy, and total energy were computed and compared with and without the void fraction being accounted for. The results show that all the mean and turbulence properties related to the air-water mixture are considerably overestimated unless void fraction is considered. When including the density variation due to the air bubbles, the wave energy dissipated exponentially a short distance after breaking; about 54% and 85% of the total energy dissipated within one and two wavelengths beyond the breaking wave impingement point, respectively.

  10. 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.

  11. 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

  12. Deformation and breakup of round drops and nonturbulent liquid jets in uniform crossflows

    NASA Astrophysics Data System (ADS)

    Aalburg, Christian

    2002-09-01

    The deformation and breakup properties of liquid drops and round liquid jets in uniform crossflows were studied computationally, motivated by applications to the behavior of sprays in crossflows found in a variety of power and propulsion systems. The objective of the present investigation was to extend the parameter range of past deformation and breakup studies, by means of numerical computations, to conditions more representative of practical high-pressure spray combustion processes. The time-dependent, incompressible and two-dimensional Navier-Stokes equations were solved on a uniform, staggered grid using the projection method of Chorin (1968) and the Level Set method of Sussman et al. (1994). Numerical simulations of the effect of crossflows on the deformation and breakup of drops and round liquid jets were carried out for the following range of parameters to study the independent effects of four dimensionless variables that fully describe the problem: Weber numbers of 0.1--2,000,000, Ohnesorge numbers of 0.001--100, Reynolds numbers of 12.5--200 and liquid/gas density ratios of 2--infinity (the last by Richardson extrapolation). The present results were in good agreement with existing measurements of deformation and breakup properties of both liquid drops and round liquid jets at large liquid/gas density ratios and with wake and drag properties of spheres and cylinders in crossflows. Similar to past experimental observations, remarkable similarities were observed between the breakup properties of round liquid jets and liquid drops. The liquid/gas density ratio was found to have a relatively small effect on deformation and breakup. Effects of Reynolds number variations were also small for conditions where the drag coefficient is relatively independent of the Reynolds number. As the Stokes flow regime is approached, however, the Weber number (We) required for breakup increases significantly due to increased drag coefficients. At large Ohnesorge number (Oh) conditions, where liquid viscous forces dominate surface tension forces, breakup is best defined in terms of a critical ratio of drag forces to liquid viscous forces, We 1/2/Oh, and plotting We1/2 /Oh vs. 1/Oh yielded breakup regime boundaries that were relatively constant for large Oh and largely independent of other parameters of the flow.

  13. 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.

  14. 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

    2015-11-01

    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.

  15. 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.

  16. 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, breaks through the free surface and strikes the far end of the tank. In the second, the turbulence spreads the jet momentum over more of the free surface, enabling the surface tension forces to turn the jet back into the bulk liquid. The model geyser height with the second model is 1.1 cm. This is quite close to the 1.5-cm geyser height measured by Aydelott.

  17. 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)

  18. 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.

  19. 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.

  20. 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 gas flow is examined, and the behavior of these jet flows in confinement tubes is also investigated. The results of this study indicate that from the standpoint of good atomization quality and controllability, coaxial injection is indeed a feasible solution for meeting the transient fuel-injection needs of the PDE.

  1. Vapor condensation at the free surface of an axisymmetric liquid mixed by a laminar jet

    NASA Technical Reports Server (NTRS)

    Lin, Chin-Shun

    1991-01-01

    This paper presents numerical solutions of jet-induced mixing in a partially full cryogenic tank. An axisymmetric laminar jet is discharged from the central part of the tank bottom toward the liquid-vapor interface. Liquid is withdrawn at the same volume flow rate from the outer part of the tank. The jet is at a temperature lower than the interface, which is maintained at a certain saturation temperature. The interface is assumed to be flat and shear free and the condensation-induced velocity is assumed to be negligibly small compared with radial interface velocity. Finite-difference method is used to slove the nondimensional form of steady-state continuity, momentum, and energy equations. Calculations are conducted for jet Reynolds numbers ranging from 150 to 600 and Prandtl numbers ranging from 0.85 to 2.65. The effects of previously stated parameters on the condensation Nusselt and Stanton numbers that characterize the steady-state interface condensation process are investigated. Detailed analysis is performed to gain a better understanding of the fundamentals of fluid mixing and interface condensation.

  2. Numerical studies of the effects of jet-induced mixing on liquid-vapor interface condensation

    NASA Technical Reports Server (NTRS)

    Lin, Chin-Shun

    1989-01-01

    Numerical solutions of jet-induced mixing in a partially full cryogenic tank are presented. An axisymmetric laminar jet is discharged from the central part of the tank bottom toward the liquid-vapor interface. Liquid is withdrawn at the same volume flow rate from the outer part of the tank. The jet is at a temperature lower than the interface, which is maintained at a certain saturation temperature. The interface is assumed to be flat and shear-free and the condensation-induced velocity is assumed to be negligibly small compared with radial interface velocity. Finite-difference method is used to solve the nondimensional form of steady state continuity, momentum, and energy equations. Calculations are conducted for jet Reynolds numbers ranging from 150 to 600 and Prandtl numbers ranging from 0.85 to 2.65. The effects of above stated parameters on the condensation Nusselt and Stanton numbers which characterize the steady-state interface condensation process are investigated. Detailed analysis to gain a better understanding of the fundamentals of fluid mixing and interface condensation is performed.

  3. 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.

  4. 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.

  5. Surface Breakup of A Liquid Jet Injected Into A Gaseous Crossflow

    NASA Astrophysics Data System (ADS)

    Behzad Jazi, Mohsen

    The normal injection of a liquid jet into a gaseous crossflow has many engineering applications. In this thesis, detailed numerical simulations based on the level set method are employed to understand the physical mechanism underlying the jet ``surface breakup''. The numerical observations reveal the existence of hydrodynamic instabilities on the jet periphery. The temporal growth of such azimuthal instabilities leads to the formation of interface corrugations, which are eventually sheared off of the jet surface as sheet-like structures. The sheets finally undergo disintegration into ligaments and drops during the surface breakup process. Temporal linear stability analyses are employed to understand the nature of these instabilities. To facilitate the analysis, analytical solutions for the flow fields of the jet and the crossflow are derived. We identify the ``shear instability'' as the primary destabilization mechanism in the flow. This inherently inviscid mechanism opposes the previously suggested mechanism of surface breakup (known as ``boundary layer stripping''), which is based on a viscous interpretation. The influence of the jet-to-crossflow density ratio on the flow stability are also studied. The findings show that a higher density jet leads to higher wavenumber instabilities on the jet surface and thereby subsequent smaller drops and ligaments. The stability characteristics of the most amplified modes (i.e., the wavenumber and corresponding growth rate) obtained from stability analyses and numerical simulations are in good agreement. The stability results of the jet also show that the density may have a non-monotonic stabilizing/destabilizing effect on the flow stability. To investigate such effect, the concept of wave resonance are employed to physically interpret the inviscid instability mechanism in two-phase flows with sharp interfaces and linear velocity profiles. We demonstrate that neutrally stable waves are formed due to the density jump in the flow, in addition to the well-known vorticity (Rayleigh) waves. Under certain conditions, such neutral waves are capable of resonating and generating unstable modes. The resonance of different pairs of neutral waves, therefore, results in either stabilizing or destabilizing effect of density variation. We predict similar reasoning behind the density behavior in the jet in crossflow configuration with smoothly varying velocity and density profiles.

  6. Ballistic imaging of the liquid core for a steady jet in crossflow

    NASA Astrophysics Data System (ADS)

    Linne, Mark A.; Paciaroni, Megan; Gord, James R.; Meyer, Terrence R.

    2005-11-01

    A time-gated ballistic imaging instrument is used to obtain high-spatial-resolution, single-shot images of the liquid core in a water spray issuing into a gaseous crossflow. We describe further development of the diagnostic technique to improve spatial resolution and present images and statistics for various jets under crossflow experimental conditions (different Weber numbers). Series of these images reveal a near-nozzle flow field undergoing breakup and subsequent droplet formation by stripping. One can also detect signatures of spatially periodic behavior in the liquid core and formation of small voids during breakup.

  7. Ballistic imaging of the liquid core for a steady jet in crossflow.

    PubMed

    Linne, Mark A; Paciaroni, Megan; Gord, James R; Meyer, Terrence R

    2005-11-01

    A time-gated ballistic imaging instrument is used to obtain high-spatial-resolution, single-shot images of the liquid core in a water spray issuing into a gaseous crossflow. We describe further development of the diagnostic technique to improve spatial resolution and present images and statistics for various jets under crossflow experimental conditions (different Weber numbers). Series of these images reveal a near-nozzle flow field undergoing breakup and subsequent droplet formation by stripping. One can also detect signatures of spatially periodic behavior in the liquid core and formation of small voids during breakup. PMID:16270551

  8. 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 smapling 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 affected 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.

  9. 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.

  10. Production of jet fuels from coal-derived liquids. Volume 15. Thermal stability of coal-derived jet fuels. Final report, September 1988-December 1989

    SciTech Connect

    Eser, S.; Song, C.; Copenhaver, R.M.; Perison, J.; Schobert, H.H.

    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. The thermal stability of organo-oxygen compound and the coal derived jet fuels was determined.

  11. Jet pinch-off and drop formation in immiscible liquid-liquid systems

    NASA Astrophysics Data System (ADS)

    Webster, D. R.; Longmire, E. K.

    The behavior of glycerin-water jets flowing into immiscible ambients of Dow Corning 200 fluid was investigated using laser induced fluorescence (LIF). Undistorted images were obtained by matching the index of refraction of the fluids. A sinusoidal perturbation was superposed on the flow to phase lock the drop formation. The forcing frequency dramatically affected the size, spacing, and number of drops that formed within a forcing cycle and the angle between drops and the jet interface just before pinch-off. Two fluid combinations were studied with similar density ratios, but viscosity ratios differing by a factor of 20. The viscosity ratio affected the jet stability as well as pinch-off angles and drop size.

  12. Transverse injection of a particle-laden liquid jet in supersonic flow: A three-phase flow

    NASA Technical Reports Server (NTRS)

    Schetz, J. A.; Ogg, J. C.

    1980-01-01

    The results of a two part study of the behavior of particle laden liquid jets injected into air are presented. Water was used as the liquid carrier and either 1-37 or 13-44 microns diam. spherical glass beads with a specific gravity of 2.8-3.0 as the particles. The observations were mainly photographic. The breakup of jets injected into still air was investigated as a function of particle loading, and the results were compared to the pure liquid jet case. The jets were found to be more stable with particles present. The length to breakup was increased, and the formation of satellite droplets was suppressed. The penetration and breakup of transverse jets in a Mach 3.0 air stream was studied. The general breakup mechanism of wave formation was found to be the same as for the all liquid case. Significant separation of the phases was observed, and the penetration of the liquid phase was reduced compared to all liquid cases at the same value of the jet to free stream momentum flux ratio.

  13. Impact of plunging breaking waves on a partially submerged cube

    NASA Astrophysics Data System (ADS)

    Wang, A.; Ikeda, C.; Duncan, J. H.

    2013-11-01

    The impact of a deep-water plunging breaking wave on a partially submerged cube is studied experimentally in a tank that is 14.8 m long and 1.2 m wide with a water depth of 0.91 m. The breakers are created from dispersively focused wave packets generated by a programmable wave maker. The water surface profile in the vertical center plane of the cube is measured using a cinematic laser-induced fluorescence technique with movie frame rates ranging from 300 to 4,500 Hz. The pressure distribution on the front face of the cube is measured with 24 fast-response sensors simultaneously with the wave profile measurements. The cube is positioned vertically at three heights relative to the mean water level and horizontally at a distance from the wave maker where a strong vertical water jet is formed. The portion of the water surface between the contact point on the front face of the cube and the wave crest is fitted with a circular arc and the radius and vertical position of the fitted circle is tracked during the impact. The vertical acceleration of the contact point reaches more than 50 times the acceleration of gravity and the pressure distribution just below the free surface shows a localized high-pressure region with a very high vertical pressure gradient. This work is supported by the Office of Naval Research under grant N000141110095.

  14. 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.

  15. 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)

  16. Thorough small-angle X-ray scattering analysis of the instability of liquid micro-jets in air.

    PubMed

    Marmiroli, Benedetta; Cacho-Nerin, Fernando; Sartori, Barbara; Pérez, Javier; Amenitsch, Heinz

    2014-01-01

    Liquid jets are of interest, both for their industrial relevance and for scientific applications (more important, in particular for X-rays, after the advent of free-electron lasers that require liquid jets as sample carrier). Instability mechanisms have been described theoretically and by numerical simulation, but confirmed by few experimental techniques. In fact, these are mainly based on cameras, which is limited by the imaging resolution, and on light scattering, which is hindered by absorption, reflection, Mie scattering and multiple scattering due to complex air/liquid interfaces during jet break-up. In this communication it is demonstrated that synchrotron small-angle X-ray scattering (SAXS) can give quantitative information on liquid jet dynamics at the nanoscale, by detecting time-dependent morphology and break-up length. Jets ejected from circular tubes of different diameters (100-450 µm) and speeds (0.7-21 m s(-1)) have been explored to cover the Rayleigh and first wind-induced regimes. Various solvents (water, ethanol, 2-propanol) and their mixtures have been examined. The determination of the liquid jet behaviour becomes essential, as it provides background data in subsequent studies of chemical and biological reactions using SAXS or X-ray diffraction based on synchrotron radiation and free-electron lasers. PMID:24365936

  17. 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 ?f /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.

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

    NASA Astrophysics Data System (ADS)

    Larsson, D. H.; Lundstrm, 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 77 ?m2 FWHM x-ray spot. The peak spectral brightness is 4 109 photons / ( s mm2 mrad2 0.1%BW) at the 24.2 keV In K? line. We use the new In/Ga source and an existing Ga/In/Sn source for high-resolution imaging and tomography of mice.

  19. 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.

  20. 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 and gelled hypergolic propellants. A calibration of the system is done with water in preparation for hypergolic injection, and characteristics of individual water and gelled JP-8 jets are studied at velocities in the range of 3 ft/s to 61 ft/s. The piston response is also analyzed to characterize the startup and steady state liquid jet velocities using orifices of 0.02" in diameter. Using this injection system, water and gelled JP-8 sprays are formed and compared across injection velocities of 30 ft/s to 121 ft/s. The comparison includes sheet shape and disintegration, total number of drops, drop size distributions, drop eccentricity, most populated drop bin size, and mean drop sizes. A test matrix for investigating the effects of mixing on ignition of MMH and IRFNA through different injection conditions are presented. First, water and IRFNA are injected to create a spray in the combustion chamber in order to verify effectiveness of test procedures and the test hardware. Next, injection of the hypergolic propellants MMH and IRFNA are done in accordance to the test matrix, although ignition was not observed as expected. These injections are followed by simple drop-on-drop tests to investigate propellant quality and ignition delay. Drop tests are performed with propellants IRFNA/MMH, and again with H2O2/Block 0 as possible propellant replacements for the proposed test plan.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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. PMID:25947392

  6. 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.

  7. 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.

  8. Simultaneous Multiphase PIV of Capillary Waves on a High Velocity Liquid Jet

    NASA Astrophysics Data System (ADS)

    Andre, Matthieu; Bardet, Philippe

    2013-11-01

    Relaxation of a laminar boundary layer below the free surface of a jet is inviscidly unstable and can roll-up which generates millimeter size waves. The latter largely modify important characteristics of jets such as heat and mass transfers between phases and can lead to breakup, or air entrainment. Two dimensional linear stability analysis predicts the initial disturbance wavelength and growth rate for inviscid flows; it does not take into account the effects of viscosity, non-linearity, or actual boundary layer profile. Because of the small temporal and spatial scales associated with this flow, few experimental data are available. Data acquisition is further complicated by the presence of a free surface with steep waves. The current experiment consists in a 20.3 mm 146.0 mm water slab laminar jet flowing onto a transparent open-channel at a Reynolds number of 2.9 104 to 1.4 105. Two high speed cameras are employed to obtain velocity fields simultaneously in the liquid and in the gas phase with Particle Image Velocimetry (PIV). Fluorescent dye is added in the liquid in order to improve interface detection. Each phase is recorded at 10 kHz, leading to a temporal resolution of 100 ?s and high magnification lenses give a spatial resolution of 200 ?m. The results confirm the mechanism of formation of the short surface waves. Generation of surface vorticity is identified in high curvature regions. Knowledge of the velocities in both phases allows studying vorticity flux through the free surface. The latter stage of wave growth can be accompanied by the formation of a vortex pair in the liquid and air entrapment.

  9. Experimental and Monte Carlo simulated spectra of a liquid-metal-jet x-ray source.

    PubMed

    Marziani, M; Gambaccini, M; Di Domenico, G; Taibi, A; Cardarelli, P

    2014-09-01

    A prototype x-ray system based on a liquid-metal-jet anode was evaluated within the framework of the LABSYNC project. The generated spectrum was measured using a CZT-based spectrometer and was compared with spectra simulated by three Monte Carlo codes: MCNPX, PENELOPE and EGS5. Notable differences in the simulated spectra were found. These are mainly attributable to differences in the models adopted for the electron-impact ionization cross section. The simulation that more closely reproduces the experimentally measured spectrum was provided by PENELOPE. PMID:24973466

  10. Investigation of laser-induced breakdown spectroscopy of a liquid jet

    SciTech Connect

    Feng Yuan; Yang Jiajun; Fan Jianmei; Yao Guanxin; Ji Xuehan; Zhang Xianyi; Zheng Xianfeng; Cui Zhifeng

    2010-05-01

    We investigate the feasibility of laser-induced breakdown spectroscopy for determination of heavy metal Pb in a Pb(NO3)2 aqueous solution by using a simple homemade vertical jet device and nanosecond laser pulses. Key experimental parameters that affect the analytical performance, such as delay of the time of observation, laser pulse energy, and liquid flow rate are optimized for the best limit of detection (LOD). The LOD was determined using Pb I emission at 405.781 nm, and after optimization, the 3{sigma} LOD was found to be at the level of 60 ppm.

  11. 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 ?m and 370 ?m. 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.

  12. 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 ?m and 370 ?m. 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

  13. 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.

  14. Vapor condensation on liquid surface due to laminar jet-induced mixing: The effects of system parameters

    NASA Technical Reports Server (NTRS)

    Lin, Chin-Shun; Hasan, Mohammad M.

    1989-01-01

    The effects of system parameters on the interface condensation rate in a laminar jet induced mixing tank are numerically studied. The physical system consists of a partially filled cylindrical tank with a slightly subcooled jet discharged from the center of the tank bottom toward the liquid-vapor interface which is at a saturation temperature corresponding to the constant tank pressure. Liquid is also withdrawn from the outer part of the tank bottom to maintain the constant liquid level. The jet velocity is selected to be low enough such that the free surface is approximately flat. The effect of vapor superheat is assumed to be negligible. Therefore, the interface condensation rate can be determined from the resulting temperature field in the liquid region alone. The nondimensional form of the steady state conservation equations are solved by a finite difference method for various system parameters including liquid height to tank diameter ratio, tank to jet diameter ratio, liquid inflow to outflow area ratio, and a heat leak parameter which characterizes the uniform wall heat flux. Detailed analyses based on the numerical solutions are performed and simplified equations are suggested for the prediction of condensation rate.

  15. Vapor condensation on liquid surface due to laminar jet-induced mixing - The effects of system parameters

    NASA Technical Reports Server (NTRS)

    Lin, Chin-Shun; Hasan, Mohammad M.

    1990-01-01

    The effects of system parameters on the interface condensation rate in a laminar jet induced mixing tank are numerically studied. The physical system consists of a partially filled cylindrical tank with a slightly subcooled jet discharged from the center of the tank bottom toward the liquid-vapor interface which is at a saturation temperature corresponding to the constant tank pressure. Liquid is also withdrawn from the outer part of the tank bottom to maintain the constant liquid level. The jet velocity is selected to be low enough such that the free surface is approximately flat. The effect of vapor superheat is assumed to be negligible. Therefore, the interface condensation rate can be determined from the resulting temperature field in the liquid region alone. The nondimensional form of the steady state conservation equations are solved by a finite difference method for various system parameters including liquid height to tank diameter ratio, tank to jet diameter ratio, liquid inflow to outflow area ratio, and a heat leak parameter which characterizes the uniform wall heat flux. Detailed analyses based on the numerical solutions are performed and simplified equations are suggested for the prediction of condensation rate.

  16. 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.

  17. Plasma Jet (V)UV-Radiation Impact on Biologically Relevant Liquids and Cell Suspension

    NASA Astrophysics Data System (ADS)

    Tresp, H.; Bussiahn, R.; Bundscherer, L.; Monden, A.; Hammer, M. U.; Masur, K.; Weltmann, K.-D.; Woedtke, Th. V.; Reuter, S.

    2014-10-01

    In this study the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH2O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH2O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals. This work is funded by German Federal Ministry of Education a Research (BMBF) (Grant # 03Z2DN12+11).

  18. 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.

  19. 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 - - Likely rate of occurrence of detectable cometary flares, in terms of the statistical distribution of relevant cometary masses M and of orbital q values. - Comparison of Brown et al's analytic estimates of their properties with those from numerical simulations, developed by modifying Carlson et al's (Icarus 121,228, 1997) Shoemaker-Levy-9 Jupiter impact model. The much higher comet-sun impact velocity compared to that for SL-9-Jupiter requires the addition of various effects, including solar, thermal, and radiative ablation, to hydrodynamic radial expansion of the impactor ,and subsequent fragmentation. The solar atmosphere's much higher temperature and ionization and lower density than Jupiter's also modify the "airburst" conditions. - Predictive estimates of the observational signatures of such explosions and their practical observability.

  20. 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.

  1. 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.

  2. 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...

  3. Scattered-light scanner measurements of cryogenic liquid-jet breakup

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.; Buchele, Donald R.

    1990-01-01

    The effect of highly turbulent Mach 1 gas flow and high thermal gradients on drop size measurements was investigated with a scattered light scanner. The instrument, developed at NASA-Lewis, was used to measure characteristic drop diameters or cyrogenic liquid sprays. By correcting for gas turbulence and thermal gradient affects, it was possible to obtain good reproducible data with the scattered light scanner. Tests were conducted primarily in the aerodynamic-stripping regime of liquid atomization and it was found that the loss of small droplets due to vaporization and dispersion had a marketed effect on drop size measurements. The nitrogen gas flow rate exponent of 1.33 is the same as that predicted by atomization theory for liquid jet breakup in high velocity gas flow. However, when the sprays were sampled farther downstream of the atomizer, at axial distances of 2.5 and 4.5 cm, the exponent for W sub n decreased 1.2 and 0.9, respectively. This was attributed to the loss of small droplets due to vaporization when values of downstream axial distances exceeded 1.3 cm.

  4. 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

  5. Stability and debris in high-brightness liquid-metal-jet-anode microfocus x-ray sources

    SciTech Connect

    Otendal, M.; Tuohimaa, T.; Hertz, H. M.

    2007-01-15

    We investigate the x-ray spot stability and the debris emission in liquid-metal-jet anode electron-impact x-ray sources operating in the 10-100 W microfocus regime. The x-ray spot size is 15-23 {mu}m in diameter and the electron-beam power density is up to {approx}210 kW/mm{sup 2}, an order of magnitude higher than for conventional microfocus sources. In the power range of the investigation the source is stable in terms of spot size and position. The debris emission rate increases exponentially with the applied electron-beam power but may be reduced by combining larger and faster target jets with smaller e-beam foci and by mitigation schemes. It is concluded that the investigated factors will not limit the performance and function of liquid-metal-jet-anode electron-impact microfocus sources when operating in this high-brightness regime.

  6. 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.

  7. 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.

  8. Physical characteristics of gas jets injected vertically upward into liquid metal

    NASA Astrophysics Data System (ADS)

    Castillejos, A. H.; Brimacombe, J. K.

    1989-10-01

    The time-averaged structure of plumes has been measured with a two-element electroresistivity probe during upward injection of nitrogen or helium into mercury in a ladle-shaped vessel. From these measurements and data obtained earlier for air jets in water, general correlations linking the spatial distribution of gas fraction with the Froude number and gas/liquid density ratio have been developed. Early evidence suggests that these correlations should be applicable to gas-stirred metallurgical baths. Measurements of the profiles of bubble velocity and bubble pierced length reveal that the kinetic energy of the gas is dissipated close to the nozzle, and buoyancy dominates flow over most of the plume.

  9. 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.

  10. 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.

  11. 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

  12. 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 performance of radial airblast injectors.

  13. Modeling and simulation of fragmentation of suddenly heated liquid metal jets.

    SciTech Connect

    Hassanein, A.; Konkashbaev, I.

    2001-06-26

    Thermoelastic response of liquid metal targets exposed to high-volumetric-energy deposition in times shorter than the target hydrodynamic response time (i.e., sound travel time) is of interest to several research areas, including first walls of fusion reactors (especially inertially confined fusion reactors), targets for high-power accelerators such as the Spallation Neutron Source, muon collider targets, etc. Under conditions that exist in these reactors, accelerators, etc., the deposited energy is considered instant in time from the hydrodynamic point of view. Because thermal heat conduction requires a longer than instant response time for energy redistribution, only hydrodynamic phenomena should be taken into account when modeling and simulating the fragmentation of suddenly heated liquid metal jets. Sudden energy deposition causes an instant rise in temperature that leads to a corresponding rise in the thermal pressure that causes excitation of sound waves, i.e., shock waves and rarefaction waves. During this excitation of sound waves, pressure oscillates with magnitude {+-} {Delta}P that corresponds to an initial thermal pressure of tens of katm. Liquids are frequently observed to withstand significant negative pressures (hydrostatic tensile stresses). Yet, a liquid subjected to a negative pressure is metastable. The formation and behavior of cavities (empty voids) under negative pressures was previously studied. Theoretically, the obtained fracture (failure) pressure of mercury is in good agreement with experimental results. Cavitation, or spontaneous formation of cavities, in stressed liquid metal targets is of interest to engineers and physicists who operate high-power targets in fusion reactors, nuclear accelerators, and particle colliders. The problems of liquid target oscillation in the presence of large magnitudes of negative pressure, and the mechanism of fragmentation and its consequences are considered in this analysis. It is shown that a cavity coming into existence will initiate a shock wave that is actually a relaxation shock wave initiated when the stretched medium reverts to normal density from the low-density state. The nature of this relaxation wave is similar to that of the detonation wave. It is also shown that a cavity born at the high-negative-pressure stage expands permanently and does not disappear. This permanent expansion and failure to disappear is a major difference between the cavity dynamics in stretched media and the dynamics observed in the usual cavitation processes that occur when vapor bubbles collapse during a phase of increased pressure, and is the result of ''unloading'' or ''discharging'' of the medium by the relaxation shock wave initiated by the appearance of the cavity. Detailed calculations of cavity dynamics are presented for both spherical and cylindrical liquid metal target systems.

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

    SciTech Connect

    Halfon, S.; Feinberg, G.; Racah Institute of Physics, Hebrew University, Jerusalem 91904 ; 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 (1.912.5 MeV, 12 mA) at SARAF.

  15. Instability of 2-D compressible gas jets in a viscous liquid medium

    SciTech Connect

    Bhunia, A.; Li, X.

    1998-12-31

    Bubbles from the disintegration of gas jets and sheets are of fundamental importance in many practical and industrial applications. Instability and breakup of gas sheets are conveniently utilized in chemical and pharmaceutical industries for gas dissolution in a liquid medium, in mining industries for coal and mineral preparation by froth floatation technique and in bubble plumes widely used for aeration, protection of structures against ocean waves and for mixing of stratified reservoirs. The instability of a plane compressible gas sheet in a quiescent viscous liquid medium of infinite expanse has been studied. It is found that there exist two unstable modes of disturbances, sinuous and varicose. For temporal instability, sinuous disturbance is stable if gas Weber number, defined as the ratio of aerodynamic to capillary forces, is less than unity, varicose mode controls the instability process except for large Weber numbers when both modes become equally important, and gas compressibility effect always enhances instability development and induces additional range of unstable wave numbers. For spatial-temporal evolution of disturbances, it is found that convective instability does not exist at all and the instability of plane gas sheets is always absolute in nature, which is strikingly opposite to the instability of plane liquid sheets. The absolutely unstable disturbance is found always temporally growing, although it may be spatially growing or decaying depending on flow conditions. Gas compressibility enhances and liquid viscosity damps out both temporal and spatial part of absolute instability growth rate. Although Weber number promotes the temporal growth rate of absolute instability, it has a dual effect of enhancing and inhibiting the spatial growth rate.

  16. 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

  17. 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.

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

    PubMed Central

    Hstad, Olle; Ernstdotter, Emma; deen, Anders

    2005-01-01

    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

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

    PubMed

    Hstad, 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

  20. The Lazarus project: Plunge waveforms from inspiralling black holes

    NASA Astrophysics Data System (ADS)

    Baker, J.; Brgmann, B.; Campanelli, M.; Lousto, C.; Takahashi, R.

    2001-10-01

    We study the coalescence of binary black holes from the innermost stable circular orbit down to the final single rotating black hole. We use a technique that combines the full numerical approach to solve Einstein equations, applied in the truly nonlinear regime, and linearized perturbation theory around the final distorted single black hole at later times. We thus produce an estimate for the plunge radiation with a non negligible signal lasting for over t~100M, and we obtain estimates of the total gravitational radiated energy and angular momentum during this process, plunging time, and waveforms. .

  1. Anaesthetic management in a case of huge plunging ranula

    PubMed Central

    Sheet, Jagabandhu; Mandal, Anamitra; Sengupta, Swapnadeep; Jana, Debaleena; Mukherji, Sudakshina; Swaika, Sarbari

    2014-01-01

    Plunging ranula is a rare form of mucous retention cyst arising from submandibular and sublingual salivary glands, which may occasionally become huge occupying the whole of the floor of the mouth and extending into the neck, thus, restricting the neck movement as well as disfiguring the normal airway anatomy. Without fiberoptic assistance, blind or retrograde nasal intubation remains valuable choices in this type of situation. Here, we present a case of successful management of airway by blind nasal intubation in a patient posted for excision of a huge plunging ranula. PMID:25886120

  2. 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 keeping the liquid surface clean and the distortion of information by the interference of equilibrium dense vapor above the liquid. By using the liquid jet technique the ejection of ions from surface of micron sized liquid can be adequately probed with a linear time-of-flight mass spectrometer. The photoionization of pure water and aqueous solutions of NaOH, NaCl and HCl is presented in Chapter 4. The aim of this investigation was to provide a fundamental understanding of the structure of water/vacuum interfaces. In Chapter 5, the ejection of ions from salt solutions containing divalent cations is also presented. The goal of the experiment was to figure out the solvation structure and reaction dynamics of divalent metal ions, M2+ on the surface of aqueous solution. A lot of work has been done in the gas phase either by a pickup-type cluster source or by collision induced dissociation of ejected ions from electrospray. For the first time the direct monitoring of ions ejected from liquid into gas phase is explored. Possible ejection mechanisms for the ejection of cations are discussed extensively in both Chapters 4 and 5. The results presented in this thesis is a combination of experiments performed at the Georgia Institute of Technology and the Pacific Northwest National Laboratory (PNNL) which includes experiments on ice and micro-jet respectively. The results in Chapters 2 and 3 have been submitted to the Journal of Chemical Physics and the Journal of Physical Chemistry respectively. It is important to note that the data presented in Chapter 3 was originally taken by Dr Janine Herring-Captain as part of her thesis work. It is also presented in this thesis due to effort in analyzing the data and preparation of the submitted manuscript. Chapter 4 and 5 represents papers which will also be submitted for publication in the open scientific literature. All the work leading to the results presented in these two chapters were done during my visit to PNNL and I would like to acknowledge that the instrumentation and data acquisition were done in collaboration with Nikolai Pet

  3. Aerodynamic effects in the break-up of liquid jets: on the first wind-induced break-up regime

    NASA Astrophysics Data System (ADS)

    Gordillo, J. M.; Prez-Saborid, M.

    2005-10-01

    We present both numerical and analytical results from a spatial stability analysis of the coupled gas liquid hydrodynamic equations governing the first wind-induced (FWI) liquid-jet break-up regime. Our study shows that an accurate evaluation of the growth rate of instabilities developing in a liquid jet discharging into a still gaseous atmosphere requires gas viscosity to be included in the stability equations even for low We_g, where We_g{=}rho_gU_l(2R_0/sigma) , and rho_g, U_l, R_0 and sigma are the gas density, the liquid injection velocity, the jet radius and the surface tension coefficient, respectively. The numerical results of the complete set of equations, in which the effect of viscosity in the gas perturbations is treated self-consistently for the first time, are in accordance with recently reported experimental growth rates. This permits us to conclude that the simple stability analysis presented here can be used to predict experimental results. Moreover, in order to throw light on the physical role played by the gas viscosity in the liquid-jet break-up process, we have considered the limiting case of very high Reynolds numbers and performed an asymptotic analysis which provides us with a parameter, alpha, that measures the relative importance of viscous effects in the gas perturbations. The criterion |alpha|{?} 1, with alpha computed a priori using only the much simpler inviscid stability results is a guide to assess the accuracy of a stability analysis in which viscous diffusion is neglected. We have also been able to explain the origin of the ad hoc constant 0.175 introduced by Sterling & Sleicher (J. Fluid Mech. vol. 68, 1975, p. 477) to correct the discrepancies between Weber's results (Z. Angew. Math. Mech. vol. 11, 1931, p. 136) and the experimental ones.

  4. A simple pneumatic device for plunge-freezing cells grown on electron microscopy grids.

    PubMed

    Cole, R; Matuszek, G; See, C; Rieder, C L

    1990-10-01

    A detailed design for a simple and inexpensive variable-speed (1.0-5.8 m s-1) pneumatic plunge-freezing device is presented. Cultured cells, grown on Formvar-coated 75-mesh gold finder grids, are pneumatically driven into a stirring mixture of propane/isopentane (3:1) cooled by liquid nitrogen (LN2). Premature freezing of the sample in the cryogenic vapors above the cryogen is prevented by plunging through an entry tube into an insulating box, to which a partial vacuum is applied. The cryogenic vapors are drafted into the box at the level of the liquid cryogen by the vacuum, thereby preventing a layer of cold gas from collecting above the cryogen. To prevent the sample from thawing during transfer from the cryogen to the substitution medium, the box top is removed and compressed air is forced through a corrugated tube running the length of the box. The resulting boiling LN2 creates an atmosphere below -120 degrees C in which the transfer can be accomplished. PMID:2213239

  5. 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 and rupture study, numerical simulations are conducted using an Eulerian-Lagrangian approach with a continuous-interface method. A reconstruction scheme is developed to allow topological changes during plug rupture by altering the connectivity information of the interface mesh. Rupture time is shown to be delayed as the initial precursor film thickness increases. During the plug rupture process, a sudden increase of mechanical stresses on the tube wall is recorded, which can cause tissue damage.

  6. PLUNGE: a computer program for transient event analysis. [PWR; BWR

    SciTech Connect

    Poehlman, B.

    1982-01-01

    PLUNGE is a computer program which performs various searches on a data base of events which lead to reactor fast shutdowns (scrams). The output is in the form of tables which show the frequency of the events. This program is an updated version of SEARCH, which was used to generate the tables shown in the appendices in EPRI NP-801.

  7. Liquid jet breakup characterization with application to melt-water mixing

    SciTech Connect

    Ginsberg, T.

    1986-01-01

    Severe accidents in light-water reactors could lead to the flow of molten core material from the initial core region of the reactor vessel to the lower plenum. Steam explosions have been predicted to occur as a result of the contact of the melt with water available in the plenum. It is presently judged by many workers, that the magnitude of the energy released during such an in-vessel explosion would be insufficient to lead to failure of the containment building (SERG, 1985). A major contributing factor in this judgment is that the mass of melt which would participate in the interaction would be limited by the quantity of melt delivered to the lower plenum to the time of the explosion and by the limited breakup of the molten pour stream as it flows through the plenum prior to the explosion. Limited pour stream breakup would lead to limited melt-water mixing and, in addition, to the existence of ''large-scale'' melt masses which may lead to very inefficient thermal-to-mechanical energy conversion. The objective of this paper is to assess the available literature relevant to liquid jet breakup and to assess its implications with respect to the behavior of molten corium pour streams as they would flow from the core region through the lower plenum. Uncertainties in application of the available literature are discussed. 7 refs., 2 figs.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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™ technology.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Transitions in the vortex wake behind the plunging profile

    NASA Astrophysics Data System (ADS)

    Koz?owski, 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.

  16. 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.

  17. 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.

  18. Mechanisms of bacterial inactivation in the liquid phase induced by a remote RF cold atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    van Gils, C. A. J.; Hofmann, S.; Boekema, B. K. H. L.; Brandenburg, R.; Bruggeman, P. J.

    2013-05-01

    A radio-frequency atmospheric pressure argon plasma jet is used for the inactivation of bacteria (Pseudomonas aeruginosa) in solutions. The source is characterized by measurements of power dissipation, gas temperature, absolute UV irradiance as well as mass spectrometry measurements of emitted ions. The plasma-induced liquid chemistry is studied by performing liquid ion chromatography and hydrogen peroxide concentration measurements on treated distilled water samples. Additionally, a quantitative estimation of an extensive liquid chemistry induced by the plasma is made by solution kinetics calculations. The role of the different active components of the plasma is evaluated based on either measurements, as mentioned above, or estimations based on published data of measurements of those components. For the experimental conditions being considered in this work, it is shown that the bactericidal effect can be solely ascribed to plasma-induced liquid chemistry, leading to the production of stable and transient chemical species. It is shown that HNO2, ONOO- and H2O2 are present in the liquid phase in similar quantities to concentrations which are reported in the literature to cause bacterial inactivation. The importance of plasma-induced chemistry at the gas-liquid interface is illustrated and discussed in detail.

  19. 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.

  20. 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.

  1. An electron jet pump: The Venturi effect of a Fermi liquid

    NASA Astrophysics Data System (ADS)

    Taubert, D.; Schinner, G. J.; Tomaras, C.; Tranitz, H. P.; Wegscheider, W.; Ludwig, S.

    2011-05-01

    A three-terminal device based upon a two-dimensional electron system is investigated in the regime of nonequilibrium transport. Excited electrons scatter with the cold Fermi sea and transfer energy and momentum to other electrons. A geometry analogous to a water jet pump is used to create a jet pump for electrons. Because of its phenomenological similarity we name the observed behavior the "electronic Venturi effect."

  2. Characteristics of impact-driven high-speed liquid jets in water

    NASA Astrophysics Data System (ADS)

    Matthujak, A.; Kasamnimitporn, C.; Sittiwong, W.; Pianthong, K.; Takayama, K.; Milton, B. E.

    2013-03-01

    This paper describes a preliminary investigation of the characteristics of high-speed water jets injected into water from an orifice. The high-speed jets were generated by the impact of a projectile launched by a horizontal single-stage powder gun and submerged in a water test chamber. The ensuing impact-driven high-speed water jets in the water were visualized by the shadowgraph technique, and the images were recorded by a high-speed digital video camera. The processes following such jet injection into water, the jet-induced shock waves, shock wave propagation, the bubble behavior, bubble collapse-induced rebound shock waves and bubble cloud re-generation were observed. Peak over-pressures of about 24 and 35 GPa measured by a Polyvinylidence difluoride (PVDF) piezoelectric film pressure sensor were generated by the jet impingement and the bubble impingement, respectively. The peak over-pressure was found to decrease exponentially as the stand-off distance between the PVDF pressure sensor and the nozzle exit increases.

  3. 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.

  4. Production of jet fuels from coal-derived liquids. Volume 3. Jet fuels potential of liquid by-products from the Great Plains Gasification Project. Interim report, September 1986-December 1987

    SciTech Connect

    Smith, E.B.; Guffey, F.D.; Nickerson, L.G.

    1988-05-01

    Three liquid by-products from the Great Plains Gasification Project, tar oil crude phenols, and naptha, were evaluated as potential sources of military jet fuels. Tar oil, produced at about 3200 barrels per day (BPD), is a highly aromatic lignite-pyrolysis liquid with a typical density of 1.01 and boiling range of about 220-975 F (104-524). Crude phenols, extracted from process water at about 900 BPD, is essentially a mixture of phenols, cresols, dihydric phenols, and naphthols, with an oxygen content averaging over 13 wt %. The naphtha is a low-boiling mixture extracted from syngas at about 725 BPD. Chief components are benzene, alkylbenzenes, sulfur compounds, and highly variable amounts of methanol, acetone, and methylethylketone. Based on these typical by-product characteristics, preliminary assessments were that the tar oil was the most-promising jet-fuel source, that crude phenols was a questionable source because of this high oxygen content, and that naphtha was a poor source because of its low-boiling range.

  5. Use of thermochromic liquid crystals in the study of jet impingement cooling: Sensitivity of transient heating methods

    SciTech Connect

    Owens, R.; Liburdy, J.A.

    1995-12-31

    In the cooling of surfaces jet impingement arrays have been found to provide effective surface heat transfer. Considerable work has been doe in identifying the optimal jet array geometry, including jet diameter, spacing and relative distance to the surface to be cooled. Most all of these studies rely on surface averaged heat transfer results. However, there are applications where the local distribution of the impingement heat transfer is important. The magnitude of the local variations may cause serious problems in terms of surface temperature gradients. Thermochromic liquid crystals provide a means to directly measure the surface temperature which can be used to study the local heat transfer coefficient distribution. Both steady state and transient methods have been identified. The steady state method is a direct application of Newton`s Law of Cooling. The transient method establishes a step change in the surface boundary condition and solves the conduction problem in the surface substrate. This method can have advantages of lower experimental uncertainty. However, there are practical issues of time response that need to be addressed to determine actual local heat transfer coefficient. This paper addresses the issues associated with the transient method and provides results of impingement cooling. Of primary concern is the transient response and how that is related to the actual instantaneous convective condition at the surface. Results show a non-steady convective coefficient which must be corrected based on the experimental design parameters.

  6. Visualization of laser-induced liquid micro-jet disintegration by means of high-speed video stroboscopy

    NASA Astrophysics Data System (ADS)

    Stasicki, Boleslaw; Charvat, Ales; Faubel, Manfred; Abel, Bernd

    2005-03-01

    In the present paper we describe a novel approach to monitor and to investigate laser induced liquid water jet disintegration in air and in vacuum. The features of liquid beam disintegration in vacuum are of importance for pulsed laser induced liquid beam desorption mass spectrometry and micro-calorimetry. Due to the small liquid beam diameter of 12-15 μm, its high speed of 50-100 m/s, and a total event duration of a less than a few microseconds only, the microscopic visualization of the jet disintegration was a challenging task. Good quality video sequences have been recorded with a high-speed video stroboscope system running in the back illumination mode. The light pulses were synchronized carefully with the shutter circuit of the stroboscope camera and the IR-laser pulses. With a continuously changing time delay between the desorption laser pulses and the shutter opening a slow-motion effect has been achieved. The delay was changed in steps of 25 ns which corresponds to an equivalent framing speed of about 40,000,000 fps. With a high-brightness light emitting diode (LED) as a light source an exposure time of about 200 ns an effective time resolution of several hundred nanoseconds could be achieved. Using a pulsed Nd:YAG laser instead, the exposure time and time resolution could be reduced down to about 10 ns and 25 ns, respectively. Due to the well known speckle problem when using coherent light sources for illumination we have finally used a Nd:YAG laser excited dye solution of Rhodamine 6G (10-3 M) in methanol solution in a quartz cuvette placed in front of the liquid beam keeping the short exposure time of about 10 ns. In this nearly speckle free visualization mode the real-time slow-motion imaging of the jet disintegration and the study of the desorption process has been made possible with a time resolution of 25 ns (currently limited by the phase shifter steps) and an exposure time of ~10 ns only. It has been found that the laser induced desorption is so fast that the measurement in the gas phase represents a "snapshot" of the situation (structure, complexation, interaction) in solution. The new desorption technique enables very promising studies of the function, structure and interaction of biopolymers in their natural environment.

  7. 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

  8. Deposit formation in liquid fuels. I - Effect of coal-derived Lewis bases on storage stability of Jet A turbine fuel

    NASA Technical Reports Server (NTRS)

    Dahlin, K. E.; Daniel, S. R.; Worstell, J. H.

    1981-01-01

    The development of reasonably precise techniques for the measurement of storage stability of jet aviation fuel is described. Lewis bases, extracted by ligand-exchange from a coal-derived liquid, are shown to adversely affect storage stability (as determined by an accelerated storage test) when added to Jet A turbine fuel. JFTOT results suggesting slight decreases in thermal stability of fuel 'spiked' (i.e., contaminated with a measured quantity of reagent) with extract are reported. Addition to Jet A turbine fuel of individual heterocyclic nitrogen compounds is shown to produce comparable decreases in storage stability.

  9. 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.

  10. Femtosecond laser-plasma interaction with prepulse-generated liquid metal micro-jets

    SciTech Connect

    Uryupina, D. S.; Ivanov, K. A.; Brantov, A. V.; Savel'ev, A. B.; Bychenkov, V. Yu.; Volkov, R. V.; Tikhonchuk, V. T.

    2012-07-11

    Ultra-short laser pulse interaction with a micro-structured surface of a melted metal is a promising source of hard X-ray radiation. Micro-structuring is achieved by a weak prepulse which produces narrow high density micro-jets. Interaction of the main laser pulse with such jets is shown to be a 100 times more efficient X-ray source than ordinary metal targets. This paper presents the results of optical and x-ray studies of laser-plasma interaction physics under such conditions supported by numerical simulations of fast electron generation.

  11. 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.

  12. 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.

  13. 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.

  14. 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 jet-in-crossflow trajectory correlations, a unique Dual Planar Laser Induced Fluorescence (Dual-PLIF) method was applied for the first time on emulsions at elevated pressure conditions. From the Dual-PLIF results, qualitative observations provided insight into the unique dispersion of oil and water concentrations within a cross-sectional plane down stream of the jet-in-crossflow injection.

  15. The effect of turbulence on the stability of liquid jets and the resulting droplet size distributions. Third quarterly technical report, July 1, 1993--September 30, 1993

    SciTech Connect

    Mansour, A.; Chigier, N.

    1993-12-01

    Laminar and turbulent columns of liquids issuing from capillary tubes were studied in order to determine the effects of turbulence on the stability of liquid jets and to establish the influence of liquid turbulence on droplet size distributions after breakup. Two capillary tubes were chosen with diameters D{sub 1}=3.0mm and D{sub 2}=1.2mm; jet Reynolds numbers were 1000--30000, and 400--7200. For water injection into stagnant air, stability curve is bounded by a laminar portion, where a jet radius and {delta}{sub o} initial disturbance amplitude, and a fully developed turbulent portion characterized by high initial disturbance amplitude (ln(a/{delta}{sub o,T}) {approximately} 4.85). In the transition region, ln(a/{delta}{sub o}) is not single valued; it decreases with increasing Reynolds number. In absence of aerodynamic effects, turbulent jets are as stable as laminar jets. For this breakup mode turbulence propagates initial disturbances with amplitudes orders of magnitude larger than laminar jets ({delta}{sub o,T}=28{times}10{sup 6} {delta}{sub o,L}). Growth rates of initial disturbances are same for both laminar and turbulent columns with theoretical Weber values. Droplet size distribution is bi-modal; the number ratio of large (> D/2), to small (< D/2) droplets is 3 and independent of Reynolds number. For laminar flow optimum wavelength ({lambda}{sub opt}) corresponding to fastest growing disturbance is equal to 4.45D, exactly the theoretical Weber value. For turbulent flow conditions, the turbulent column segments. Typically, segments with lengths of one to several wavelengths, detach from the liquid jet. The long ligaments contract under the action of surface tension, resulting in droplet sizes larger than predicted by Rayleigh and Weber. For turbulent flow conditions, {lambda}{sub opt} = 9.2D, about 2 times the optimum Weber wavelength.

  16. GRB 110328A/SWIFT J164449.3+573451: THE TIDAL OBLITERATION OF A DEEPLY PLUNGING STAR?

    SciTech Connect

    Cannizzo, J. K.

    2011-11-20

    We examine the tidal disruption event (TDE) scenario to explain Sw 1644+57, a powerful and persistent X-ray source which suddenly became active as GRB 110328A. The precise localization at the center of a z = 0.35 galaxy argues for activity of the central engine as the underlying cause. We look at the suggestion by Bloom et al. of the possibility of a TDE. We argue that Sw 1644+57 cannot be explained by the traditional TDE model in which the periastron distance is close to the tidal disruption radius-three independent lines of argument indicate the orbit must be deeply plunging or else the powerful jet we are observing could not be produced. These arguments stem from (1) comparing the early X-ray light curve to the expected theoretical fallback rate, (2) looking at the time of transition to disk-dominated decay, and (3) considering the TDE rate. Due to the extreme excess in the tidal force above that which would be required minimally to disrupt the star in a deeply plunging orbit at periastron, we suggest this scenario might be referred to more descriptively as a tidal obliteration event (TOE) rather than a TDE.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Combustion of liquid fuel in the counter-swirled jets of a gas turbine plant annular combustion chamber

    NASA Astrophysics Data System (ADS)

    Tumanovskii, A. G.; Semichastnyi, N. N.; Sokolov, K. Iu.

    1986-03-01

    Tests were carried out on an annular combustion chamber rig with a stabilizer of the type used in the GTN-25 gas turbine plant to determine the feasibility of burning a liquid fuel (diesel fuel, GOST 4749-73) in a combustion chamber of this type. Very high performance was obtained for a number of important characteristics of the microflame combustion process in counterswirled jets where all the air was supplied through the front unit of the chamber. However, the tests did not make it possible to solve some of the problems which arise when operating under full-scale conditions, such as the required high combustion efficiency under variable operating conditions of a gas turbine plant; elimination of soot formation at the walls of the stabilizer and the internal surfaces of the pipes supplying fuel to the atomizers; and a decrease in smoking under conditions of excess air factor.

  2. Cold blocking of the channel in a gas-liquid mixer by hot fuel jets

    SciTech Connect

    Rudyak, M.E.

    1983-11-01

    This article examines cold blocking in a circular channel with separate feeds for the oxidant and fuel and diffusion burning on the latter. Jets of T-1 kerosene at a temperature of +20/sup 0/C were injected into a gas channel of a mixer with an internal diameter of 21 mm at angles of 60 and 90/sup 0/ and a distance of 28 mm from the lower end of the channel, which terminates in a step expansion into a combustion chamber of diameter 70 mm. The oxidizing gas at about 650/sup 0/C consists of 94% oxygen and 6% of products from the complete combustion of the fuel, and this enters the mixer from a reservoir. It is determined that a mixer blocked by a cold flow has the following advantages: pressure perturbations from the combustion chamber do not penetrate into the mixer and reservoir, and steady-state operation is provided in the mixer; the peripheral flow of cold gas protects the wall of the mixer from overheating and damage; deep jet penetration prevents the accumulation of fuel beyond the step, which reduces the combustion completeness; and the high longitudinal and transverse static-pressure gradients around the step greatly accelerate the mixing and favor a more uniform distribution of the fuel in the oxidant flow. It is concluded that a blocked mixer can be used to improve the working process in a combustion chamber.

  3. Effect of Charge Relaxation in Three-Dimensional Numerical Simulations of Turbulent Primary Atomization of Electrically Charged Liquid Jets

    NASA Astrophysics Data System (ADS)

    Courtine, Emilien; van Poppel, Bret; Daily, John; Desjardins, Olivier

    2012-11-01

    Electrohydrodynamics (EHD) is an interdisciplinary topic that describes the complex interaction between fluid mechanics and electric fields. In the context of combustion applications, EHD may enable improved spray control and finer atomization so that fuel injection schemes can be inexpensively developed for small engines. Moreover, EHD may provide efficient enhancements to hydrocarbon fuel atomization that could benefit a much broader range of engines and non-combustion applications. In this work, high-fidelity numerical simulations of an electrically charged kerosene jet undergoing turbulent atomization are presented. The simulations make use of first-principle-based methods designed to accurately represent the interfacial stresses and discontinuities. Under the assumption of a large electric Reynolds number, it can be appropriate to assume that the charges do not have time to relax to the liquid-gas interface, and that they do not drift within the liquid volume. Alternatively, one can solve a free charge conservation equation to fully account for charge drift. These two approaches are compared in details, and the role of charge drift in EHD atomization is analyzed. The implementation of the charge transport equation, which is discontinuous in nature, is discussed as well.

  4. Microbial Inactivation in the Liquid Phase Induced by Multigas Plasma Jet.

    PubMed

    Takamatsu, Toshihiro; Uehara, Kodai; Sasaki, Yota; Hidekazu, Miyahara; Matsumura, Yuriko; Iwasawa, Atsuo; Ito, Norihiko; Kohno, Masahiro; Azuma, Takeshi; Okino, Akitoshi

    2015-01-01

    Various gas atmospheric nonthermal plasmas were generated using a multigas plasma jet to treat microbial suspensions. Results indicated that carbon dioxide and nitrogen plasma had high sterilization effects. Carbon dioxide plasma, which generated the greatest amount of singlet oxygen than other gas plasmas, killed general bacteria and some fungi. On the other hand, nitrogen plasma, which generated the largest amount of OH radical, killed ? 6 log of 11 species of microorganisms, including general bacteria, fungi, acid-fast bacteria, spores, and viruses in 1-15 min. To identify reactive species responsible for bacterial inactivation, antioxidants were added to bacterial suspensions, which revealed that singlet oxygen and OH radicals had greatest inactivation effects. PMID:26173107

  5. Plain-jet airblast atomization of alternative liquid petroleum fuels under high ambient air pressure conditions

    NASA Astrophysics Data System (ADS)

    Jasuja, A. K.

    1982-04-01

    The effects that air and fuel properties have upon the spray mean drop size characteristics of a plain-jet airblast atomizer of the type employed in the gas turbine engine are investigated. The tests used kerosene, gas oil and a high-viscosity blend of gas oil in residual fuel oil, and covered a wide range of ambient air pressures. Laser light-scattering technique was employed for drop size measurements. It is concluded that the atomizer's measured mean drop size characteristics are only slightly different from those of the pre-filming type, especially when operating on low-viscosity kerosene under higher ambient air pressure. The beneficial effect of increased levels of ambient air pressure on mean drop size is shown to be much reduced in the case of high-viscosity fuels, thus making the attainment of good atomization performance on such fuels difficult. An expression is derived for correlating the obtained mean drop size data.

  6. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Dynamics of formation of the liquid-drop phase of laser erosion jets near the surfaces of metal targets

    NASA Astrophysics Data System (ADS)

    Goncharov, V. K.; Kontsevoi, V. L.; Puzyrev, M. V.

    1995-03-01

    An investigation was made of laser erosion jets formed at 0.1-1.5 mm above the surfaces of Pb, Co, Ni, Sn, and Zn targets. A neodymium laser emitting rectangular pulses of 400 ?s duration and of energy up to 400 J was used. The diameters, as well as the number density and volume fraction of the metal particles present in the jet, were measured. An analysis of the results showed that the metal liquid drops broke up near the surface and experienced additional evaporation because of their motion opposite to the laser beam.

  7. Featured Image: A Galaxy Plunges Into a Cluster Core

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-10-01

    The galaxy that takes up most of the frame in this stunning image (click for the full view!) is NGC 1427A. This is a dwarf irregular galaxy (unlike the fortuitously-located background spiral galaxy in the lower right corner of the image), and its currently in the process of plunging into the center of the Fornax galaxy cluster. Marcelo Mora (Pontifical Catholic University of Chile) and collaborators have analyzed observations of this galaxy made by both the Very Large Telescope in Chile and the Hubble Advanced Camera for Surveys, which produced the image shown here as a color composite in three channels. The team worked to characterize the clusters of star formation within NGC 1427A identifiable in the image as bright knots within the galaxy and determine how the interactions of this galaxy with its cluster environment affect the star formation within it. For more information and the original image, see the paper below.Citation:Marcelo D. Mora et al 2015 AJ 150 93. doi:10.1088/0004-6256/150/3/93

  8. Featured Image: A Galaxy Plunges Into a Cluster Core

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    The galaxy that takes up most of the frame in this stunning image (click for the full view!) is NGC 1427A. This is a dwarf irregular galaxy (unlike the fortuitously-located background spiral galaxy in the lower right corner of the image), and its currently in the process of plunging into the center of the Fornax galaxy cluster. Marcelo Mora (Pontifical Catholic University of Chile) and collaborators have analyzed observations of this galaxy made by both the Very Large Telescope in Chile and the Hubble Advanced Camera for Surveys, which produced the image shown here as a color composite in three channels. The team worked to characterize the clusters of star formation within NGC 1427A identifiable in the image as bright knots within the galaxy and determine how the interactions of this galaxy with its cluster environment affect the star formation within it. For more information and the original image, see the paper below.Citation:Marcelo D. Mora et al 2015 AJ 150 93. doi:10.1088/0004-6256/150/3/93

  9. Temporal analysis of acoustic emission from a plunged granular bed.

    PubMed

    Tsuji, Daisuke; Katsuragi, Hiroaki

    2015-10-01

    The statistical property of acoustic emission (AE) events from a plunged granular bed is analyzed by means of actual-time and natural-time analyses. These temporal analysis methods allow us to investigate the details of AE events that follow a power-law distribution. In the actual-time analysis, the calm-time distribution, and the decay of the event-occurrence density after the largest event (i.e., the Omori-Utsu law) are measured. Although the former always shows a power-law form, the latter does not always obey a power law. Markovianity of the event-occurrence process is also verified using a scaling law by assuming that both of them exhibit power laws. We find that the effective shear strain rate is a key parameter to classify the emergence rate of power-law nature and Markovianity in granular AE events. For the natural-time analysis, the existence of self-organized critical states is revealed by calculating the variance of natural time ?(k), where kth natural time of N events is defined as ?(k)=k/N. In addition, the energy difference distribution can be fitted by a q-Gaussian form, which is also consistent with the criticality of the system. PMID:26565229

  10. Temporal analysis of acoustic emission from a plunged granular bed

    NASA Astrophysics Data System (ADS)

    Tsuji, Daisuke; Katsuragi, Hiroaki

    2015-10-01

    The statistical property of acoustic emission (AE) events from a plunged granular bed is analyzed by means of actual-time and natural-time analyses. These temporal analysis methods allow us to investigate the details of AE events that follow a power-law distribution. In the actual-time analysis, the calm-time distribution, and the decay of the event-occurrence density after the largest event (i.e., the Omori-Utsu law) are measured. Although the former always shows a power-law form, the latter does not always obey a power law. Markovianity of the event-occurrence process is also verified using a scaling law by assuming that both of them exhibit power laws. We find that the effective shear strain rate is a key parameter to classify the emergence rate of power-law nature and Markovianity in granular AE events. For the natural-time analysis, the existence of self-organized critical states is revealed by calculating the variance of natural time ?k, where k th natural time of N events is defined as ?k=k /N . In addition, the energy difference distribution can be fitted by a q -Gaussian form, which is also consistent with the criticality of the system.

  11. Unsteady Aerodynamics on a Pitching Plunging Flat Plate

    NASA Astrophysics Data System (ADS)

    Hart, Adam; Ukeiley, Lawrence

    2010-11-01

    Biology has shown that natural fliers utilize unsteady flow mechanisms to enhance their lift characteristics in low Reynolds number flight regimes. This study will investigate the interaction between the leading edge vortices (LEVs) and tip vortices over a low aspect ratio flat plate being subjected to a pitch-plunge kinematic motion. Previous studies have shown the creation of stable vortices off the leading edge at the three quarter span location between times 0.25 and 0.50 in the kinematic motion. This study furthers previous knowledge by mapping the flow field around these vortex cores. This will allow for an understanding into the interaction of the LEV with tip vortices and how the LEVs convect downstream. Specifically we look to validate the interactions between these vortex systems leading to enhanced lift as has been demonstrated in very low Reynolds number numerical simulations. A combination of two dimensional and stereo Particle Image Velocimetery (PIV) is used to measure the flow field around the flat plate at various spanwise and chordwise locations. The PIV measurements are triggered by the dynamic motion rig allowing for phase averaging at key locations throughout the motion cycle.

  12. Taylor cone and jetting from liquid droplets in electrospinning of nanofibers

    NASA Astrophysics Data System (ADS)

    Yarin, A. L.; Koombhongse, S.; Reneker, D. H.

    2001-11-01

    Sessile and pendant droplets of polymer solutions acquire stable shapes when they are electrically charged by applying an electrical potential difference between the droplet and a flat plate, if the potential is not too large. These stable shapes result only from equilibrium of the electric forces and surface tension in the cases of inviscid, Newtonian, and viscoelastic liquids. In liquids with a nonrelaxing elastic force, that force also affects the shapes. It is widely assumed that when the critical potential ?0* has been reached and any further increase will destroy the equilibrium, the liquid body acquires a conical shape referred to as the Taylor cone, having a half angle of 49.3. In the present work we show that the Taylor cone corresponds essentially to a specific self-similar solution, whereas there exist nonself-similar solutions which do not tend toward a Taylor cone. Thus, the Taylor cone does not represent a unique critical shape: there exists another shape, which is not self-similar. The experiments of the present work demonstrate that the observed half angles are much closer to the new shape. In this article a theory of stable shapes of droplets affected by an electric field is proposed and compared with data acquired in our experimental work on electrospinning of nanofibers from polymer solutions and melts.

  13. Pulse Jets, Rims and Elastic-Liquid Sheets: Rheology at High Strain Rates and Rupture Criteria

    NASA Astrophysics Data System (ADS)

    Mitkin, V. V.; Rozhkov, A. N.; Theofanous, T. G.

    2008-07-01

    We demonstrate the use mm-scale pulse jets in collision with small conical targets (yielding expanding/contracting rim/sheet flow structures) to determine the elastic properties of polymer solutions at high strain rates. The rheology is consistent with that of a simple elastic continuum, as in the Oldroyd model, while the modulus of elasticity is found to be more than one order of magnitude greater, and the relevant relaxation times more than one order smaller, than previous values known from capillary-draining (low strain rate) experiments. For each combination of polymer molecular weight and concentration, there is a critical velocity that yields incipient (single point) rupture of the rim; a phenomenon that escalates rapidly (multiple, simultaneous ruptures in the rim, as well as in the membrane) with further increases in velocity. We show that the onset is consistent with a critical stress level which varies proportionately with polymer concentration but is independent of molecular weight supporting a hypothesis of a molecular bond release mechanism.

  14. Experimental study on instantaneous thrust and lift of two plunging wings in tandem

    NASA Astrophysics Data System (ADS)

    Gong, Wu Qi; Jia, Bo Bo; Xi, Guang

    2016-01-01

    Two tandem wings undergoing a two-dimensional sinusoidal plunging motion are studied in a low Reynolds number water tunnel. The influence of the phase angle and leading-edge vortex (LEV) on the peak value of the instantaneous thrust and lift is studied. The instantaneous lift and thrust are measured by a force sensor; the velocity and vorticity fields are captured by digital particle image velocimetry. For the forewing, noticeable differences at various phase angles are found in the peak value of the instantaneous lift and thrust rather than in their minimum value. The LEV of the hindwing increased the maximum effective angle of attack of the forewing and enhanced the jet-like flow behind the forewing, which accounts for the increase in peak value. For the hindwing, the phase angle determines the sign of the forewing-shed LEV when the hindwing encounters this LEV. If the forewing-shed LEV before the leading edge of the hindwing has the opposite sense of rotation as the LEV of the hindwing, the velocity of the flow on the windward side of the hindwing increases, resulting in high instantaneous thrust and lift. If the two LEVs have the same sense of rotation, the forewing-shed LEV hinders the growth of the hindwing LEV because of the small effective angle of attack, leading to low instantaneous thrust and lift. Non-circulatory forces on the wings are calculated according to a potential flow model. Results show that the non-circulatory force has important effects on the peak value and symmetry of the instantaneous lift and thrust curves.

  15. The Rayleigh-Plateau instability and jet formation during the extrusion of liquid metal from craters in a vacuum arc cathode spot

    NASA Astrophysics Data System (ADS)

    Mesyats, G. A.; Zubarev, N. M.

    2015-01-01

    We consider the displacement of molten metal from a crater being formed on the cathode during the operation of a vacuum arc under the pressure of the cathode plasma and formulate a criterion for the formation of a thin ridge of expelled liquid metal (a sheet-like jet) at the crater edge. When the ridge height is substantially greater than its thickness, conditions arise for the development of the Rayleigh-Plateau capillary instability, which breaks the axial symmetry of the problem. Estimates are presented, which suggest that this instability is responsible for the breakup of the liquid ridge into jets, which play an important role in the self-sustained operation of a discharge.

  16. Interactive graphics system for locating plunge electrodes in cardiac MRI images

    NASA Astrophysics Data System (ADS)

    Laxer, Cary; Johnson, G. A.; Kavanagh, Katherine M.; Simpson, Edward V.; Ideker, Raymond E.; Smith, William M.

    1991-05-01

    Understanding the mechanisms of ventricular fibrillation and defibrillation requires analysis of epicardial and endocardial potentials throughout the heart. Plunge electrodes permit recording of cardiac potentials at epicardial and endocardial sites, and allow determination of electrical gradients. They also enable us to determine the arrhythmia recurrence sites following failed defibrillation; these sites may be epicardial or endocardial. Therefore, it is necessary to relate the position of the plunge electrodes to the cardiac geometry. We have developed an interactive, computer graphics based system that allows us to locate plunge electrodes on digitized MRI slices of a heart. The system, which can work with any type of image, allows us to identify the epicardial and endocardial points of each plunge electrode on the different MRI slices. Up to 128 different plunge electrodes may be identified to the system. Normalized 3-D coordinates for each epicardial and endocardial electrode point are computed and stored in data files on the computer. Geometry information obtained from this system permits a more thorough understanding of the electrical signals recorded by the plunge electrodes. This information can be used in the study of cardiac excitation and arrhythmias and could help in the development of a more effective lead system for ventricular defibrillation.

  17. The eye of the storm: light from the inner plunging region of black hole accretion discs

    NASA Astrophysics Data System (ADS)

    Zhu, Yucong; Davis, Shane W.; Narayan, Ramesh; Kulkarni, Akshay K.; Penna, Robert F.; McClintock, Jeffrey E.

    2012-08-01

    It is generally thought that the light coming from the inner plunging region of black hole accretion discs contributes negligibly to the disc's overall spectrum, i.e. the plunging fluid is swallowed by the black hole before it has time to radiate. In the standard disc model used to fit X-ray observations of accretion discs, the plunging region is assumed to be perfectly dark. However, numerical simulations that include the full physics of the magnetized flow predict that a small fraction of the disc's total luminosity emanates from the plunging region. We investigate the observational consequences of this neglected inner light. We compute radiative-transfer-based disc spectra that correspond to 3D general relativistic magnetohydrodynamic simulated discs (which produce light inside their plunging regions). In the context of black hole spin estimation, we find that the neglected inner light only has a modest effect (this bias is less than typical observational systematic errors). For rapidly spinning black holes, we find that the combined emission from the plunging region produces a weak power-law tail at high energies. This indicates that infalling matter is the origin for some of the 'coronal' emission observed in the thermal dominant and steep power-law states of X-ray binaries.

  18. Effect of exhaust gas recirculation on emissions from a flame-tube combustor using Liquid Jet A fuel

    NASA Technical Reports Server (NTRS)

    Marek, C. J.; Tacina, R. R.

    1976-01-01

    The effects of uncooled exhaust gas recirculation as an inert diluent on emissions of oxides of nitrogen (NO + NO2) and on combustion efficiency were investigated. Ratios of recirculated combustion products to inlet airflow were varied from 10 to 80 percent by using an inlet air ejector nozzle. Liquid Jet A fuel was used. The flame-tube combustor was 10.2 cm in diameter. It was operated with and without a flameholder present. The combustor pressure was maintained constant at 0.5 MPa. The equivalence ratio was varied from 0.3 to 1.0. The inlet air temperature was varied from 590 to 800 K, and the reference velocity from 10 to 30 m/sec. Increasing the percent recirculation from 10 to 25 had the following effects: (1) the peak NOx emission was decreased by 37 percent, from 8 to 5 g NO2/kg fuel, at an inlet air temperature of 590 K and a reference velocity of 15 m/sec; (2) the combustion efficiency was increased, particularly at the higher equivalence ratios; and (3) for a high combustion efficiency of greater than 99.5 percent, the range of operation of the combustor was nearly doubled in terms of equivalence ratio. Increasing the recirculation from 25 to 50 percent did not change the emissions significantly.

  19. Production of jet fuels from coal-derived liquids. Volume 7. GPGP jet-fuels production program. Evaluation of technical uncertainties for producing jet fuels from liquid by-products of the Great Plains gasification plant. Interim report, 2 October 1987-30 September 1988

    SciTech Connect

    Fraser, M.D.; Rossi, R.J.; Wan, E.I.

    1989-01-01

    In September 1986, the Fuels Branch of the Aero Propulsion Laboratory at Wright-Patterson Air Force Base, Ohio, began an investigation of the potential of jet-fuel production from the liquid by-product streams produced by the gasification of lignite at the Great Plains Gasification Plant (GPGP) in Beulah, North Dakota. Funding was provided by the Department of Energy (DOE) Pittsburgh Energy Technology Center (PETC) to administer the experimental portion of this effort. This document reports the results of the effort by Burns and Roe Services Corporation/Science Applications International Corporation (BRSC/SAIC) to analyze GPGP operations and develop correlations for the liquid by-products and plant operating factors such as coal feed rate and coal characteristics.

  20. The final plunge of spinning binary black holes

    NASA Astrophysics Data System (ADS)

    Baker, John; Campanelli, Manuela; Lousto, Carlos; Takahashi, Ryoji

    2003-04-01

    With the goal of bringing theory, particularly numerical relativity, to bear on an astrophysical problem of critical interest to gravitational wave observers we introduce a model for coalescence radiation from binary black hole systems. We build our model using the Lazarus approach, a technique that bridges far and close limit approaches with full numerical relativity to solve Einstein equations applied in the truly nonlinear dynamical regime. We specifically study the post-orbital radiation from a system of equal-mass non-spinning black holes, deriving waveforms which indicate strongly circularly polarized radiation of roughly 3% of the system's total energy and 12% of its total angular momentum in just a few cycles. Supporting this result we first establish the reliability of the late-time part of our model, including the numerical relativity and close-limit components, with a thorough study of waveforms from a sequence of black hole configurations varying from previously treated head-on collisions to representative target for ``ISCO'' data corresponding to the end of the inspiral period. We then complete our model with a simple treatment for the early part of the spacetime based on a standard family of initial data for binary black holes in circular orbit. A detailed analysis shows strong robustness in the results as the initial separation of the black holes is increased from 5.0 to 7.8M supporting our waveforms as a suitable basic description of the astrophysical radiation from this system. Finally, a simple fitting of the plunge waveforms is introduced as a first attempt to facilitate the task of analyzing data from gravitational wave detectors.

  1. On shock driven jetting of liquid from non-sinusoidal surfaces into a vacuum

    SciTech Connect

    Cherne, F. J.; Hammerberg, J. E.; Andrews, M. J.; Karkhanis, V.; Ramaprabhu, P.

    2015-11-09

    Other work employed Richtmyer-Meshkov theory to describe the development of spikes and bubblesfrom shocked sinusoidal surfaces. Here, we discuss the effects of machining different two-dimensional shaped grooves in copper and examine the resulting flow of the material after being shocked into liquid on release. For these simulations, a high performance molecular dynamics code, SPaSM, was used with machined grooves of kh 0 = 1 and kh 0 = 1/8, where 2h 0 is the peak-to-valley height of the perturbation with wavelength λ, and k = 2π/λ. The surface morphologies studied include a Chevron, a Fly-Cut, a Square-Wave, and a Gaussian. Furthermore, we describe extensions to an existing ejecta source model that better captures the mass ejected from these surfaces. We also investigate the same profiles at length scales of order 1 cm for an idealized fluid equation of state using the FLASH continuum hydrodynamics code. Our findings indicate that the resulting mass can be scaled by the missing area of a sinusoidal curve with an effective wavelength, λeff , that has the same missing area. Finally, our extended ejecta mass formula works well for all the shapes considered and captures the corresponding time evolution and total mass.

  2. On shock driven jetting of liquid from non-sinusoidal surfaces into a vacuum

    DOE PAGESBeta

    Cherne, F. J.; Hammerberg, J. E.; Andrews, M. J.; Karkhanis, V.; Ramaprabhu, P.

    2015-11-09

    Other work employed Richtmyer-Meshkov theory to describe the development of spikes and bubblesfrom shocked sinusoidal surfaces. Here, we discuss the effects of machining different two-dimensional shaped grooves in copper and examine the resulting flow of the material after being shocked into liquid on release. For these simulations, a high performance molecular dynamics code, SPaSM, was used with machined grooves of kh 0 = 1 and kh 0 = 1/8, where 2h 0 is the peak-to-valley height of the perturbation with wavelength λ, and k = 2π/λ. The surface morphologies studied include a Chevron, a Fly-Cut, a Square-Wave, and a Gaussian.more » Furthermore, we describe extensions to an existing ejecta source model that better captures the mass ejected from these surfaces. We also investigate the same profiles at length scales of order 1 cm for an idealized fluid equation of state using the FLASH continuum hydrodynamics code. Our findings indicate that the resulting mass can be scaled by the missing area of a sinusoidal curve with an effective wavelength, λeff , that has the same missing area. Finally, our extended ejecta mass formula works well for all the shapes considered and captures the corresponding time evolution and total mass.« less

  3. On shock driven jetting of liquid from non-sinusoidal surfaces into a vacuum

    NASA Astrophysics Data System (ADS)

    Cherne, F. J.; Hammerberg, J. E.; Andrews, M. J.; Karkhanis, V.; Ramaprabhu, P.

    2015-11-01

    Previous work employed Richtmyer-Meshkov theory to describe the development of spikes and bubbles from shocked sinusoidal surfaces. Here, we discuss the effects of machining different two-dimensional shaped grooves in copper and examine the resulting flow of the material after being shocked into liquid on release. For these simulations, a high performance molecular dynamics code, SPaSM, was used with machined grooves of kh0 = 1 and kh0 = 1/8, where 2h0 is the peak-to-valley height of the perturbation with wavelength λ, and k = 2π/λ. The surface morphologies studied include a Chevron, a Fly-Cut, a Square-Wave, and a Gaussian. We describe extensions to an existing ejecta source model that better captures the mass ejected from these surfaces. We also investigate the same profiles at length scales of order 1 cm for an idealized fluid equation of state using the FLASH continuum hydrodynamics code. Our findings indicate that the resulting mass can be scaled by the missing area of a sinusoidal curve with an effective wavelength, λeff, that has the same missing area. Our extended ejecta mass formula works well for all the shapes considered and captures the corresponding time evolution and total mass.

  4. First application of liquid-metal-jet sources for small-animal imaging: High-resolution CT and phase-contrast tumor demarcation

    SciTech Connect

    Larsson, Daniel H.; Lundstroem, Ulf; Burvall, Anna; Hertz, Hans M.

    2013-02-15

    Purpose: Small-animal studies require images with high spatial resolution and high contrast due to the small scale of the structures. X-ray imaging systems for small animals are often limited by the microfocus source. Here, the authors investigate the applicability of liquid-metal-jet x-ray sources for such high-resolution small-animal imaging, both in tomography based on absorption and in soft-tissue tumor imaging based on in-line phase contrast. Methods: The experimental arrangement consists of a liquid-metal-jet x-ray source, the small-animal object on a rotating stage, and an imaging detector. The source-to-object and object-to-detector distances are adjusted for the preferred contrast mechanism. Two different liquid-metal-jet sources are used, one circulating a Ga/In/Sn alloy and the other an In/Ga alloy for higher penetration through thick tissue. Both sources are operated at 40-50 W electron-beam power with {approx}7 {mu}m x-ray spots, providing high spatial resolution in absorption imaging and high spatial coherence for the phase-contrast imaging. Results: High-resolution absorption imaging is demonstrated on mice with CT, showing 50 {mu}m bone details in the reconstructed slices. High-resolution phase-contrast soft-tissue imaging shows clear demarcation of mm-sized tumors at much lower dose than is required in absorption. Conclusions: This is the first application of liquid-metal-jet x-ray sources for whole-body small-animal x-ray imaging. In absorption, the method allows high-resolution tomographic skeletal imaging with potential for significantly shorter exposure times due to the power scalability of liquid-metal-jet sources. In phase contrast, the authors use a simple in-line arrangement to show distinct tumor demarcation of few-mm-sized tumors. This is, to their knowledge, the first small-animal tumor visualization with a laboratory phase-contrast system.

  5. Development of liquid-lithium film jet-flow for the target of (7)Li(p,n)(7)Be reactions for BNCT.

    PubMed

    Kobayashi, Tooru; Miura, Kuniaki; Hayashizaki, Noriyosu; Aritomi, Masanori

    2014-06-01

    A feasibility study on liquid lithium target in the form of a flowing film was performed to evaluate its potential use as a neutron generation target of (7)Li(p,n)(7)Be reaction in BNCT. The target is a windowless-type flowing film on a concave wall. Its configuration was adapted for a proton beam which is 30mm in diameter and with energy and current of up to 3MeV and 20mA, respectively. The flowing film of liquid lithium was 0.6mm in thickness, 50mm in width and 50mm in length. The shapes of the nozzle and concave back wall, which create a stable flowing film jet, were decided based on water experiments. A lithium hydrodynamic experiment was performed to observe the stability of liquid lithium flow behavior. The flowing film of liquid lithium was found to be feasible at temperatures below the liquid lithium boiling saturation of 342C at the surface pressure of 110(-3)Pa. Using a proto-type liquid lithium-circulating loop for BNCT, the stability of the film flow was confirmed for velocities up to 30m/s at 220C and 250C in vacuum at a pressure lower than 10(-3) Pa. It is expected that for practical use, a flowing liquid lithium target of a windowless type can solve the problem of radiation damage and target cooling. PMID:24412425

  6. Effect of nozzle configuration on transport in the stagnation zone of axisymmetric, impinging free-surface liquid jets: Part 2-local heat transfer

    SciTech Connect

    Pan, Y.; Stevens, J.; Webb, B.W. )

    1992-11-01

    This is the second of a two-part study on the flow structure and heat transfer characteristics of turbulent, free-surface liquid jets. Part 2 deals with the effect of selected nozzle configurations on the local heat transfer in the stagnation zone. Infrared techniques have been used to characterize the local heat transfer for the four nozzle configurations whose mean and turbulent flow structure was detailed in Part 1. The results show that for identical jet Reynolds numbers, significant differences exist in the magnitudes of the local Nusselt number for the nozzle types studied. Differences of approximately 40 percent were observed. Local heat transfer results reveal that for already turbulent jets, the mean radial velocity gradient appears to be more influential in determining the heat transfer than incremental changes in the level of turbulence (as measured by the radial component of the fluctuations). An empirical correlation of the experimental data supports this conclusion, and reveals that the stagnation Nusselt number is affected independently by the jet Reynolds number and the dimensionless mean radial velocity gradient. 21 refs., 6 figs.

  7. Effect of nozzle configuration on transport in the stagnation zone of axisymmetric, impinging free-surface liquid jets: Part 1-turbulent flow structure

    SciTech Connect

    Stevens, J.; Pan, Y.; Webb, B.W. )

    1992-11-01

    This study characterized the mean and fluctuating parts of the radial component of the local velocity in the stagnation region of an impinging, free-surface liquid jet striking a smooth flat plate. Four different nozzle exit conditions were studied, including fully developed pipe flow, a contoured nozzle, and turbulence-damped and undamped sharp-edged orifices. Liquid jet Reynolds numbers in the range 30,000 to 55,000 were investigated. Velocities were measured using laser-Doppler velocimetry. Mean velocities were found to vary nearly linearly with radial location, with the slope of the line being a function of distance from the impingement plate. Dimensionless mean velocity gradients, of relevance to the heat transfer, were found to be a strong function of nozzle type, but roughly independent of jet Reynolds number for a given nozzle type. Turbulence levels were also found to be strongly influenced by the nozzle exit-condition. Local heat transfer data corresponding to the flow structure measurements presented here are reported in Part 2 of this study. 22 refs., 9 figs.

  8. Design and Testing of an Automated System using Thermochromatic Liquid Crystals to Determine Local Heat Transfer Coefficients for an Impinging Jet

    NASA Technical Reports Server (NTRS)

    Tan, Benjamin

    1995-01-01

    Using thermochromatic liquid crystal to measure surface temperature, an automated transient method with time-varying free-stream temperature is developed to determine local heat transfer coefficients. By allowing the free-stream temperature to vary with time, the need for complicated mechanical components to achieve a step temperature change is eliminated, and by using the thermochromatic liquid crystals as temperature indicators, the labor intensive task of installing many thermocouples is omitted. Bias associated with human perception of the transition of the thermochromatic liquid crystal is eliminated by using a high speed digital camera and a computer. The method is validated by comparisons with results obtained by the steady-state method for a circular Jet impinging on a flat plate. Several factors affecting the accuracy of the method are evaluated.

  9. Generation of thrust and lift with airfoils in plunging and pitching motion

    NASA Astrophysics Data System (ADS)

    Moriche, M.; Flores, O.; Garca-Villalba, M.

    2015-01-01

    We present fully resolved Direct Numerical Simulations of 2D flow over a moving airfoil, using an in-house code that solves the Navier-Stokes equations of the incompressible flow with an Immersed Boundary Method. A combination of sinusoidal plunging and pitching motions is imposed to the airfoil. Starting from a thrust producing case (Reynolds number, Re = 1000, reduced frequency, k = 1.41, plunging amplitude h0/c = 1, pitching amplitude ?0 = 30, phase shift phi = 90), we increase the mean pitching angle (in order to produce lift) and vary the phase shift between pitching and plunging (to optimize the direction and magnitude of the net force on the airfoil). These cases are discussed in terms of their lift coefficient, thrust coefficient and propulsive efficiency.

  10. CFD based investigation on the impact acceleration when a gannet impacts with water during plunge diving.

    PubMed

    Wang, T M; Yang, X B; Liang, J H; Yao, G C; Zhao, W D

    2013-09-01

    Plunge diving is the most commonly used feeding method of a gannet, which can make the gannet transit from air to water rapidly and successfully. A large impact acceleration can be generated due to the air-to-water transition. However, the impact acceleration experienced by the gannet during plunge diving has not been studied. In this paper, this issue is investigated by using the CFD method. The effect of the dropping height and the water-entry inclination angle on the impact acceleration is considered. The results reveal that the impact acceleration along the longitudinal body axis increases with either of the two parameters. The peak time decreases with the dropping height. A quadratic relation is found between the peak impact acceleration and the initial water-entry velocity. According to the computation, when the dropping height is 30 m (most of gannets plunge from about this height), the peak impact acceleration can reach about 23 times the gravitational acceleration, which will exert a considerable force on the gannet body. Furthermore, the pressure distribution of different water-entry inclination angles indicates that the large pressure asymmetry caused by a small oblique angle may lead to a large impact acceleration in the direction perpendicular to the longitudinal body axis and cause damage to the neck of the gannet, which partly explains the reason why a gannet performing a high plunge diving in nature enters water with a large oblique angle from the perspective of impact mechanics. The investigation on the plunge-diving behavior in this paper will inspire and promote the development of a biomimetic amphibious robot that transits from air to water with the plunge-diving mode. PMID:23851321

  11. Mathematical Modeling And Design Optimization Of Plunge Shaving Cutter For Gears With Tooth Modifications

    NASA Astrophysics Data System (ADS)

    Chang, Shinn-Liang; Liu, Jia-Hung

    2009-10-01

    Gears are the most important components in transmission systems. Modifications of gear teeth can accommodate errors and deformations encountered in the manufacture, assembly, and operation of gear pairs. For plunge shaving gears with tooth modifications, the design criteria of cutter clearance manufactured by protuberance hob cutter is investigated. With this novel design, the cutter has better strength and stiffness to keep the shaved gear profile stable. With the analytical descriptions of crowned gear and hence plunge shaving cutter have been constructed so that the grinding wheel can be optimized to minimized the topographic error. Efficiency is greatly improved by avoiding the traditional trial and error method.

  12. Large Plunging Ranula Presenting as Isolated Neck Swelling: Steps in Diagnosis and Surgical Steps in Management.

    PubMed

    Nilesh, Kumar; Malik, Neelima A; Patil, Pankaj; Chapi, Mouneshkumar Devendrappa

    2015-06-01

    Ranula is a salivary gland cyst which typically present as localized superficial swelling over the floor of mouth. Complex or plunging ranulas develop when the mucus extravasation extends through or around the mylohyoid muscle, deeper into the neck, and present with neck lump along with or without swelling over floor of mouth. We report a case of large plunging ranula presenting as an isolated large neck mass in a 38-year-old female patient. The steps in diagnosis and surgical steps in management of the pathology are systematically described. PMID:26266141

  13. Large Plunging Ranula Presenting as Isolated Neck Swelling: Steps in Diagnosis and Surgical Steps in Management

    PubMed Central

    Malik, Neelima A.; Patil, Pankaj; Chapi, Mouneshkumar Devendrappa

    2015-01-01

    Ranula is a salivary gland cyst which typically present as localized superficial swelling over the floor of mouth. Complex or plunging ranulas develop when the mucus extravasation extends through or around the mylohyoid muscle, deeper into the neck, and present with neck lump along with or without swelling over floor of mouth. We report a case of large plunging ranula presenting as an isolated large neck mass in a 38-year-old female patient. The steps in diagnosis and surgical steps in management of the pathology are systematically described. PMID:26266141

  14. A comprehensive Two-Fluid Model for Cavitation and Primary Atomization Modelling of liquid jets - Application to a large marine Diesel injector

    NASA Astrophysics Data System (ADS)

    Habchi, Chawki; Bohbot, Julien; Schmid, Andreas; Herrmann, Kai

    2015-12-01

    In this paper, a comprehensive two-fluid model is suggested in order to compute the in-nozzle cavitating flow and the primary atomization of liquid jets, simultaneously. This model has been applied to the computation of a typical large marine Diesel injector. The numerical results have shown a strong correlation between the in-nozzle cavitating flow and the ensuing spray orientation and atomization. Indeed, the results have confirmed the existence of an off-axis liquid core. This asymmetry is likely to be at the origin of the spray deviation observed experimentally. In addition, the primary atomization begins very close to the orifice exit as in the experiments, and the smallest droplets are generated due to cavitation pocket shape oscillations located at the same side, inside the orifice.

  15. Parameter dependence of vortex interactions on a two-dimensional plunging plate

    NASA Astrophysics Data System (ADS)

    Eslam Panah, Azar; Buchholz, James H. J.

    2014-03-01

    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 streamwise advancement of the LEV during a plunge cycle and its resulting interaction with the TEV is primarily dependent on reduced frequency; however, for Strouhal numbers above approximately 0.4, significant changes are observed in the formation of vortices shed from the leading and trailing edges, as well as the circulation of the leading-edge vortex. The functional form of the relationship between leading-edge vortex circulation and Strouhal number suggests that the Strouhal number dependence is more specifically a manifestation of the effective angle of attack. 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.

  16. Too Fast, Too Furious: A Galaxy's Fatal Plunge

    NASA Astrophysics Data System (ADS)

    2004-01-01

    Trailing 200,000-light-year-long streamers of seething gas, a galaxy that was once like our Milky Way is being shredded as it plunges at 4.5 million miles per hour through the heart of a distant cluster of galaxies. In this unusually violent collision with ambient cluster gas, the galaxy is stripped down to its skeletal spiral arms as it is eviscerated of fresh hydrogen for making new stars. The galaxy's untimely demise is offering new clues to solving the mystery of what happens to spiral galaxies in a violent universe. Views of the early universe show that spiral galaxies were once much more abundant in rich clusters of galaxies. But they seem to have been vanishing over cosmic time. Where have these "missing bodies" gone? Astronomers are using a wide range of telescopes and analysis techniques to conduct a "CSI" or Crime Scene Investigator-style look at what is happening to this galaxy inside its cluster's rough neighborhood. "It's a clear case of galaxy assault and battery," says William Keel of the University of Alabama. "This is the first time we have a full suite of results from such disparate techniques showing the crime being committed, and the modus operandi." Keel and colleagues are laying out the "forensic evidence" of the galaxy's late life, in a series of presentations today in Atlanta, Ga., at the 203rd meeting of the American Astronomical Society. Astronomers have assembled the evidence by combining a variety of diagnostic observations from telescopes analyzing the galaxy's appearance in X-ray, optical, and radio light. Parallel observations at different wavelengths trace how stars, gas, and dust are being tossed around and torn from the fragile galaxy, called C153. Though such "distressed" galaxies have been seen before, this one's demise is unusually swift and violent. The galaxy belongs to a cluster of galaxies that slammed into another cluster about 100 million years ago. This galaxy took the brunt of the beating as it fell along a trajectory straight through the dense core of the colliding cluster. "This helps explain the weird X-ray and radio emissions we see," says Keel. "The galaxy is a laboratory for studying how gas can be stripped away when it flies through the hot cluster gas, shutting down star birth and transforming the galaxy." The first suggestion of galactic mayhem in this cluster came in 1994 when the Very Large Array radio telescope near Socorro, N.M., detected an unusual number of radio galaxies in the cluster, called Abell 2125. Radio sources trace both star formation and the feeding of central black holes in galaxy clusters. The radio observations also showed that C153 stood out from the other galaxies as an exceptionally powerful radio source. Keel's team began an extensive program of further observations to uncover details about the galaxies. "This was designed to see what the connection could possibly be between events on the 10-million-light-year scale of the cluster merger and what happens deep inside individual galaxies," says Keel. X-ray observations from the ROSAT satellite (an acronym for the Roentgen Satellite) demonstrated that the cluster contains vast amounts of 36-million-degree Fahrenheit (20-million-degree Kelvin) gas that envelops the galaxies. The gas is concentrated into two main lumps rather than smoothly distributed across the cluster, as is more commonly the case. This bolstered the suspicion that two galaxy clusters are actually colliding. In the mid-to-late 1990s astronomers turned the Mayall 4-meter telescope and the WIYN 3.5-meter telescope at the Kitt Peak National Observatory on the cluster to analyze the starlight via spectroscopy. They found many star-forming systems and even active galactic black holes fueled by the collision. The disintegrating galaxy C153 stood out dramatically when the KPNO telescopes were used to photomap the cluster in color. Astronomers then trained NASA's Hubble Space Telescope (HST) onto C153 and resolved a bizarre shape. They found that the galaxy looks unusually clumpy with many young star clusters and chaotic dust features. Besides the disrupted features in the galaxy's disk, HST also showed that the light in the tail is mostly attributed to recent star formation, providing a direct link to the stripping of the galaxy as it passed through the cluster core. Gas compressed along the galaxy's leading edge, like snow before a plow, ignited a firestorm of new star birth. Evidence of recent star formation also comes from the optical spectrum obtained at the 10-meter Gemini North telescope in Hawaii. The spectrum allows the researchers to estimate the time since the most recent burst of star formation. This conclusion was further bolstered when the Mosaic camera on Kitt Peak's Mayall telescope found a very long tail of extended gas coming off the galaxy. The tail was apparently generated in part by a hurricane of stellar winds boiling off the new star-birth regions and being blown backwards as the galaxy streaks through the surrounding hot gas of the cluster. Spectroscopic observations with the Gemini telescope allowed astronomers to age-date the starburst. They find that 90 percent of C153's blue light is from a population of stars that are 100 million years old. This age corresponds to the time the galaxy should have gone careening through the densest gas in the cluster core. The Gemini spectroscopic observations show the stars are in a regular pattern of orbital motion around the center, as usual for disk galaxies. However, there are multiple widespread clouds of gas moving independently of the stars. "This is an important clue that something beyond gravitational forces must be at work, since stars and gas respond the same way to purely gravitational forces," says Keel. "In other words, the galaxy's gas doesn't know what the stars are doing." NASA's Chandra X-ray Observatory discovered that the cooler clouds detected with optical telescopes and an associated radio feature are embedded in a much larger multimillion-degree trail of gas. Chandra's data indicate that this hot gas was probably enriched in heavy elements by the starburst and driven out of the galaxy by its supersonic motion through the much larger cloud of gas that pervades the cluster. Collectively, these observations offer evidence that the ram pressure of external gas in the cluster is stripping away the galaxy's own gas. This process has long been hypothesized to account for the forced evolution of cluster galaxies. Its aftermath has been seen in several ways. Some nearby examples, Seyfert's Sextet and Stefan's Quintet, are tight clusters that show the aftermath of high-velocity collisions. The galaxy C153 is destined to lose the last vestiges of its spiral arms and become a bland S0-type galaxy having a central bulge and disk, but no spiral-arm structure. These types of galaxies are common in the dense galaxy clusters seen today. Astronomers plan to make new observations with Gemini again in 2004 to study the dynamics of the gas and stars in the tail. The science team members are William Keel (University of Alabama), Frazer Owen (National Radio Astronomy Observatory), Michael Ledlow (Gemini Observatory), and Daniel Wang (University of Massachusetts). NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

  17. Comparison of propagation- and grating-based x-ray phase-contrast imaging techniques with a liquid-metal-jet source

    NASA Astrophysics Data System (ADS)

    Zhou, T.; Lundstrm, U.; Thring, Thomas; Rutishauser, S.; Larsson, D. H.; Stampanoni, M.; David, C.; Hertz, H. M.; Burvall, A.

    2014-03-01

    X-ray phase-contrast imaging has been developed as an alternative to conventional absorption imaging, partly for its dose advantage over absorption imaging at high resolution. Grating-based imaging (GBI) and propagation-based imaging (PBI) are two phase-contrast techniques used with polychromatic laboratory sources. We compare the two methods by experiments and simulations with respect to required dose. A simulation method based on the projection approximation is designed and verified with experiments. A comparison based on simulations of the doses required for detection of an object with respect to its diameter is presented, showing that for monochromatic radiation, there is a dose advantage for PBI for small features but an advantage for GBI at larger features. However, GBI suffers more from the introduction of polychromatic radiation, in this case so much that PBI gives lower dose for all investigated feature sizes. Furthermore, we present and compare experimental images of biomedical samples. While those support the dose advantage of PBI, they also highlight the GBI advantage of quantitative reconstruction of multimaterial samples. For all experiments a liquid-metal-jet source was used. Liquid-metal-jet sources are a promising option for laboratory-based phase-contrast imaging due to the relatively high brightness and small spot size.

  18. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    NASA Astrophysics Data System (ADS)

    Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

    2015-12-01

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  19. Twin Jet

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Bozak, Rick

    2010-01-01

    Many subsonic and supersonic vehicles in the current fleet have multiple engines mounted near one another. Some future vehicle concepts may use innovative propulsion systems such as distributed propulsion which will result in multiple jets mounted in close proximity. Engine configurations with multiple jets have the ability to exploit jet-by-jet shielding which may significantly reduce noise. Jet-by-jet shielding is the ability of one jet to shield noise that is emitted by another jet. The sensitivity of jet-by-jet shielding to jet spacing and simulated flight stream Mach number are not well understood. The current experiment investigates the impact of jet spacing, jet operating condition, and flight stream Mach number on the noise radiated from subsonic and supersonic twin jets.

  20. Development of gullies on the landscape: A model of headcut retreat resulting from plunge pool erosion

    NASA Astrophysics Data System (ADS)

    Flores-Cervantes, Javier H.; Istanbulluoglu, Erkan; Bras, Rafael L.

    2006-03-01

    Head advance due to plunge pool erosion is a common process in gullies incising resistant soils. A model of headcut retreat resulting from plunge pool erosion is developed and implemented in the channel-hillslope integrated landscape development (CHILD) model, an existing three-dimensional landscape evolution modeling framework. The model estimates horizontal headcut retreat as a function of discharge, height of the headcut, upstream slope, and relevant land surface and soil properties for soil erosion. We analyze the sensitivity of headcut retreat to flow discharge, upstream slope and surface roughness, and headcut height. CHILD simulations indicate that headcut retreat is most significant in zones with either gentle slopes or large headcut heights. Model parameters have contrasting effects on the retreat rates depending on the size and depth of the pool beneath the headcut and upstream flow hydraulics, making the process difficult to predict as a function of topographic thresholds and simple geomorphic transport laws.

  1. Fault-related folding during extension: Plunging basement-cored folds in the Basin and Range

    USGS Publications Warehouse

    Howard, K.A.; John, Barbara E.

    1997-01-01

    Folds are able to form in highly extended areas where stratified cover rocks respond to basement fault offsets. The response of cover rocks to basement faulting can be studied especially well in plunging structures that expose large structural relief. The southern Basin and Range province contains plunging folds kilometres in amplitude at the corners of domino-like tilt blocks of basement rocks, where initially steep transverse and normal faults propagated upward toward the layered cover rocks. Exposed tilted cross sections, as much as 8 km thick, display transitions from faulted basement to folded cover that validate laboratory models of forced folds. The folded cover masks a deeper extensional style of brittle segmentation and uniform steep tilting.

  2. The manipulation of trailing-edge vortices for an airfoil in plunging motion

    NASA Astrophysics Data System (ADS)

    Prangemeier, T.; Rival, D.; Tropea, C.

    2010-02-01

    Trailing-edge vortex manipulation has been investigated using particle image velocimetry (PIV) for an airfoil undergoing harmonic plunging superimposed with a pitching motion near the bottom of the stroke. The so-called quick-pitch motion has been evaluated through a comparison with a benchmark pure-sinusoidal plunge motion for Re=30000 and k=0.25. It has been shown that the trailing-edge vortex circulation can be reduced by more than 60% for all quick-pitch cases. The reduction in trailing-edge vortex circulation has been achieved without diminishing the strength of the leading-edge vortex, thus maintaining the lift augmentation achieved through dynamic stall. The improvement over the benchmark case is then confirmed through a statistical analysis. Finally, an analysis of the flow separation over the airfoil shows that the various quick-pitch motions facilitate earlier flow reattachment at the bottom of the stroke.

  3. Measurement and analysis of internal stress distributions created in gelatin simulated-brain tissue by a pulsed laser-induced liquid jet.

    PubMed

    Kato, T; Arafune, T; Washio, T; Nakagawa, A; Ogawa, Y; Tominaga, T; Sakuma, I; Kobayashi, E

    2014-01-01

    Transsphenoidal surgery is currently employed to treat complex lesions beyond the sella turcica; however, the procedure can be limited by difficulties encountered in dealing with small blood vessels, deep and narrow working spaces, and awkward working angles. To overcome these problems, we have developed a pulsed laser-induced liquid jet system that can dissect tumor tissue while preserving fine blood vessels within deep and narrow working spaces. We have previously evaluated the utility and safety of this procedure. However, the effects of the pulsejet after being injected into the brain are not yet well understood. Especially, the behavior of the stress distribution created by the jet is important because it has recently been reported that high acoustic pressures can affect the brain. In this study, we measured internal stress distributions in a gelatin simulated-brain using photoelasticity experiments. We used a high-speed camera with an image sensor on which an array of micropolarizers was attached to measure the stresses and the shear wave created when the pulsejet enters the simulated brain. PMID:25570972

  4. X-ray grating interferometry for 9.25 keV design energy at a liquid-metal-jet source

    NASA Astrophysics Data System (ADS)

    Balles, A.; Fella, Ch.; Dittmann, J.; Wiest, W.; Zabler, S.; Hanke, R.

    2016-01-01

    In this paper we present a grating interferometer setup with a liquid-metal-jet source and a high resolution detector. It will be shown that this source is suitable for interferometer setups as it delivers a sufficient spatial coherence that makes a source grating unnecessary. This is confirmed twice by the results of an interferometer setup and a single grating setup, respectively. Both show comparable information on the samples. Furthermore, it was possible to measure the Talbot effect due to the self-built high resolution detector with an effective pixel size of 0.67 µm and due to the coherence of the source, thanks to a small spot size of a few microns. The information on the absorption of a nylon fiber is observed to include inline phase contrast effects. The dark-field signal of a carbon fiber reinforced polymer (CFRP) is not quite well understood because of its inhomogeneity.

  5. Pool-Type Fishways: Two Different Morpho-Ecological Cyprinid Species Facing Plunging and Streaming Flows

    PubMed Central

    Branco, Paulo; Santos, José M.; Katopodis, Christos; Pinheiro, António; Ferreira, Maria T.

    2013-01-01

    Fish are particularly sensitive to connectivity loss as their ability to reach spawning grounds is seriously affected. The most common way to circumvent a barrier to longitudinal connectivity, and to mitigate its impacts, is to implement a fish passage device. However, these structures are often non-effective for species with different morphological and ecological characteristics so there is a need to determine optimum dimensioning values and hydraulic parameters. The aim of this work is to study the behaviour and performance of two species with different ecological characteristics (Iberian barbel Luciobarbus bocagei–bottom oriented, and Iberian chub Squalius pyrenaicus–water column) in a full-scale experimental pool-type fishway that offers two different flow regimes–plunging and streaming. Results showed that both species passed through the surface notch more readily during streaming flow than during plunging flow. The surface oriented species used the surface notch more readily in streaming flow, and both species were more successful in moving upstream in streaming flow than in plunging flow. Streaming flow enhances upstream movement of both species, and seems the most suitable for fishways in river systems where a wide range of fish morpho-ecological traits are found. PMID:23741465

  6. Pool-type fishways: two different morpho-ecological cyprinid species facing plunging and streaming flows.

    PubMed

    Branco, Paulo; Santos, José M; Katopodis, Christos; Pinheiro, António; Ferreira, Maria T

    2013-01-01

    Fish are particularly sensitive to connectivity loss as their ability to reach spawning grounds is seriously affected. The most common way to circumvent a barrier to longitudinal connectivity, and to mitigate its impacts, is to implement a fish passage device. However, these structures are often non-effective for species with different morphological and ecological characteristics so there is a need to determine optimum dimensioning values and hydraulic parameters. The aim of this work is to study the behaviour and performance of two species with different ecological characteristics (Iberian barbel Luciobarbus bocagei-bottom oriented, and Iberian chub Squalius pyrenaicus-water column) in a full-scale experimental pool-type fishway that offers two different flow regimes-plunging and streaming. Results showed that both species passed through the surface notch more readily during streaming flow than during plunging flow. The surface oriented species used the surface notch more readily in streaming flow, and both species were more successful in moving upstream in streaming flow than in plunging flow. Streaming flow enhances upstream movement of both species, and seems the most suitable for fishways in river systems where a wide range of fish morpho-ecological traits are found. PMID:23741465

  7. Elemental Water Impact Test: Phase 3 Plunge Depth of a 36-Inch Aluminum Tank Head

    NASA Technical Reports Server (NTRS)

    Vassilakos, Gregory J.

    2014-01-01

    Spacecraft are being designed based on LS-DYNA water landing simulations. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. Phase 3 featured a composite tank head that was tested at a range of heights to verify the ability to predict structural failure of composites. To support planning for Phase 3, a test series was conducted with an aluminum tank head dropped from heights of 2, 6, 10, and 12 feet to verify that the test article would not impact the bottom of the test pool. This report focuses on the comparisons of the measured plunge depths to LS-DYNA predictions. The results for the tank head model demonstrated the following. 1. LS-DYNA provides accurate predictions for peak accelerations. 2. LS-DYNA consistently under-predicts plunge depth. An allowance of at least 20% should be added to the LS-DYNA predictions. 3. The LS-DYNA predictions for plunge depth are relatively insensitive to the fluid-structure coupling stiffness.

  8. Jet shielding of jet noise

    NASA Technical Reports Server (NTRS)

    Simonich, J. C.; Amiet, R. K.; Schlinker, R. H.

    1986-01-01

    An experimental and theoretical study was conducted to develop a validated first principle analysis for predicting the jet noise reduction achieved by shielding one jet exhaust flow with a second, closely spaced, identical jet flow. A generalized fuel jet noise analytical model was formulated in which the acoustic radiation from a source jet propagates through the velocity and temperature discontinuity of the adjacent shielding jet. Input variables to the prediction procedure include jet Mach number, spacing, temperature, diameter, and source frequency. Refraction, diffraction, and reflection effects, which control the dual jet directivity pattern, are incorporated in the theory. The analysis calculates the difference in sound pressure level between the dual jet configuration and the radiation field based on superimposing two independent jet noise directivity patterns. Jet shielding was found experimentally to reduce noise levels in the common plane of the dual jet system relative to the noise generated by two independent jets.

  9. Deposit formation in liquid fuels. II - The effect of selected compounds on the storage stability of Jet A turbine fuel

    NASA Technical Reports Server (NTRS)

    Worstell, J. H.; Daniel, S. R.

    1981-01-01

    The influence of substituted pyridines, pyrroles, indoles, and quinolines on the storage stability of conventional Jet A turbine fuel is evaluated. Significant increases in the amount of deposit formed in accelerated storage tests are found upon addition of these compounds at levels as low as one ppm nitrogen. While the effect is correlated with basicity of the nitrogen compound within a given compound class, the correlation does not hold between classes (pyridines, quinolines, etc.). Steric hindrance at the nitrogen atom greatly inhibits deposit promotion. The characteristics, but not the elemental composition, of deposits vary with the identity of the added nitrogen compound and with deposition temperature.

  10. Analysis of a Free Surface Film from a Controlled Liquid Impinging Jet over a Rotating Disk Including Conjugate Effects, with and without Evaporation

    NASA Technical Reports Server (NTRS)

    Sankaran, Subramanian (Technical Monitor); Rice, Jeremy; Faghri, Amir; Cetegen, Baki M.

    2005-01-01

    A detailed analysis of the liquid film characteristics and the accompanying heat transfer of a free surface controlled liquid impinging jet onto a rotating disk are presented. The computations were run on a two-dimensional axi-symmetric Eulerian mesh while the free surface was calculated with the volume of fluid method. Flow rates between 3 and 15 1pm with rotational speeds between 50 and 200 rpm are analyzed. The effects of inlet temperature on the film thickness and heat transfer are characterized as well as evaporative effects. The conjugate heating effect is modeled, and was found to effect the heat transfer results the most at both the inner and outer edges of the heated surface. The heat transfer was enhanced with both increasing flow rate and increasing rotational speeds. When evaporative effects were modeled, the evaporation was found to increase the heat transfer at the lower flow rates the most because of a fully developed thermal field that was achieved. The evaporative effects did not significantly enhance the heat transfer at the higher flow rates.

  11. Evaluation of the sensitivity and response of IR thermography from a transparent heater under liquid jet impingement

    NASA Astrophysics Data System (ADS)

    Haustein, H. D.; Rohlfs, W.; Al-Sibai, F.; Kneer, R.

    2012-11-01

    The feasibility of a visible/IR transparent heater and its suitability for IR thermography is experimentally examined. The most common transparent conductive coating, Indium Tin Oxide (ITO), is quite reflective and its optical properties depend on thickness and manufacturing process. Therefore, the optical properties of several thicknesses and types of ITO, coated on an IR window (BaF2), are examined. A highly transparent Cadmium Oxide (CdO) coating on a ZnS window, also examined, is found to be unusable. Transmissivity is found to increase with a decrease in coating thickness, and total emittance is relatively low. A thick ITO coating was examined for IR thermography in the challenging test case of submerged water jet impingement, where temperature differences were characteristically small and distributed. The measurements under steady state conditions were found to agree well with the literature, and the method was validated. Comparison of two IR cameras did not show the LWIR low-temperature advantage, up to the maximal acquisition rate examined, 1.3KHz. Rather the MWIR camera had a stronger signal to noise ratio, due to the higher emissivity of the heater in this range. The transient response of the transparent heater showed no time-delay, though the substrate dampens the thermal response significantly. Therefore, only qualitative transient measurements are shown for the case of pulsating free-surface jet impingement, showing that the motion of the hydraulic jump coincides with thermal measurements. From these results, recommendations are made for coating/window combination in IR thermography.

  12. On the effect of mantle conductivity on the super-rotating jets near the liquid core surface

    NASA Astrophysics Data System (ADS)

    Mizerski, K. A.; Bajer, K.

    2007-03-01

    We consider hydromagnetic Couette flows in planar and spherical geometries with strong magnetic field (large Hartmann number, M?1). The highly conducting bottom boundary is in steady motion that drives the flow. The top boundary is stationary and is either a highly conducting thin shell or a weakly conducting thick mantle. The magnetic field, B+b, is a combination of the strong, force-free background B and a perturbation b induced by the flow. This perturbation generates strong streamwise electromagnetic stress inside the fluid which, in some regions, forms a jet moving faster than the driving boundary. The super-velocity, in the spherical geometry called super-rotation, is particularly prominent in the region where the 'grazing' line of B has a point of tangent contact with the top boundary and where the Hartmann layer is singular. This is a consequence of topological discontinuity across that special field line. We explain why the magnitude of super-rotation already present when the top wall is insulating [Dormy, E., Jault, D., Soward, A.M., 2002. A super-rotating shear layer in magnetohydrodynamic spherical Couette flow. J. Fluid Mech. 452, 263-291], considerably increases when that wall is even slightly conducting. The asymptotic theory is valid when either the thickness of the top wall is small, ?M-1 and its conductivity is high, ?1 or when ?1 and ?M-1. The theory predicts the super-velocity enhancement of the order of ?M in the first case and ?M in the second case. We also numerically solve the planar problem outside the asymptotic regime, for ?=1 and ?=1, and find that with the particular B that we chose the peak super-velocity scales like M0.33. This scaling is different from M0.6 found in spherical geometry [Hollerbach, R., Skinner, S., 2001. Instabilities of magnetically induced shear layers and jets. Proc. R. Soc. Lond. A 457, 785-802].

  13. Jet pump assisted artery

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A procedure for priming an arterial heat pump is reported; the procedure also has a means for maintaining the pump in a primed state. This concept utilizes a capillary driven jet pump to create the necessary suction to fill the artery. Basically, the jet pump consists of a venturi or nozzle-diffuser type constriction in the vapor passage. The throat of this venturi is connected to the artery. Thus vapor, gas, liquid, or a combination of the above is pumped continuously out of the artery. As a result, the artery is always filled with liquid and an adequate supply of working fluid is provided to the evaporator of the heat pipe.

  14. Finite element analysis and computer graphics visualization of flow around pitching and plunging airfoils

    NASA Technical Reports Server (NTRS)

    Bratanow, T.; Ecer, A.

    1973-01-01

    A general computational method for analyzing unsteady flow around pitching and plunging airfoils was developed. The finite element method was applied in developing an efficient numerical procedure for the solution of equations describing the flow around airfoils. The numerical results were employed in conjunction with computer graphics techniques to produce visualization of the flow. The investigation involved mathematical model studies of flow in two phases: (1) analysis of a potential flow formulation and (2) analysis of an incompressible, unsteady, viscous flow from Navier-Stokes equations.

  15. Numerical simulation of a plunging flexible hydrofoil and its experimental validation

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    A monolithic approach for simulation of flexible flapping wings in fully-coupled motion has recently been developed. The methodology is based on a uniform description of fluid and structure in Eulerian framework. Immersed boundary technique is used to represent solid stress, solid-fluid interface, and active flapping motion in an overall Cartesian coordinate. In the current presentation, the focus is to apply the method on a simple two-dimensional problem of plunging flexible hydrofoil and then compare to the experimental results for validation. The three-dimensional results and experimental validations will also be discussed. Supported by Army High Performance Computing Research Center.

  16. Thermal Tolerance Limits of Diamondback Moth in Ramping and Plunging Assays

    PubMed Central

    Nguyen, Chi; Bahar, Md Habibullah; Baker, Greg; Andrew, Nigel R.

    2014-01-01

    Thermal sensitivity is a crucial determinant of insect abundance and distribution. The way it is measured can have a critical influence on the conclusions made. Diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae) is an important insect pest of cruciferous crops around the world and the thermal responses of polyphagous species are critical to understand the influences of a rapidly changing climate on their distribution and abundance. Experiments were carried out to the lethal temperature limits (ULT0 and LLT0: temperatures where there is no survival) as well as Upper and Lower Lethal Temperature (ULT25 and LLT25) (temperature where 25% DBM survived) of lab-reared adult DBM population to extreme temperatures attained by either two-way ramping (ramping temperatures from baseline to LT25 and ramping back again) or sudden plunging method. In this study the ULT0 for DBM was recorded as 42.6°C and LLT0 was recorded as −16.5°C. DBM had an ULT25 of 41.8°C and LLT25 of −15.2°C. The duration of exposure to extreme temperatures had significant impacts on survival of DBM, with extreme temperatures and/or longer durations contributing to higher lethality. Comparing the two-way ramping temperature treatment to that of direct plunging temperature treatment, our study clearly demonstrated that DBM was more tolerant to temperature in the two-way ramping assay than that of the plunging assay for cold temperatures, but at warmer temperatures survival exhibited no differences between ramping and plunging. These results suggest that DBM will not be put under physiological stress from a rapidly changing climate, rather access to host plants in marginal habitats has enabled them to expand their distribution. Two-way temperature ramping enhances survival of DBM at cold temperatures, and this needs to be examined across a range of taxa and life stages to determine if enhanced survival is widespread incorporating a ramping recovery method. PMID:24475303

  17. Higher-Order Spectral Analysis of a Nonlinear Pitch and Plunge Apparatus

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.; Strganac, Thomas W.; Hajj, Muhammad R.

    2005-01-01

    Simulated aeroelastic responses of a nonlinear pitch and plunge apparatus are analyzed using various statistical signal processing techniques including higher-order spectral methods. A MATLAB version of the Nonlinear Aeroelastic Testbed Apparatus (NATA) at the Texas A&M University is used to generate various aeroelastic response data including limit cycle oscillations (LCO). Traditional and higher-order spectral (HOS) methods are applied to the simulated aeroelastic responses. Higher-order spectral methods are used to identify critical signatures that indicate the transition from linear to nonlinear (LCO) aeroelastic behavior.

  18. Membrane damage and active but nonculturable state in liquid cultures of Escherichia coli treated with an atmospheric pressure plasma jet.

    PubMed

    Dolezalova, Eva; Lukes, Petr

    2015-06-01

    Electrical discharge plasmas can efficiently inactivate various microorganisms. Inactivation mechanisms caused by plasma, however, are not fully understood because of the complexity of both the plasma and biological systems. We investigated plasma-induced inactivation of Escherichia coli in water and mechanisms by which plasma affects bacterial cell membrane integrity. Atmospheric pressure argon plasma jet generated at ambient air in direct contact with bacterial suspension was used as a plasma source. We determined significantly lower counts of E. coli after treatment by plasma when they were assayed using a conventional cultivation technique than using a fluorescence-based LIVE/DEAD staining method, which indicated that bacteria may have entered the viable-but-nonculturable state (VBNC). We did not achieve resuscitation of these non-culturable cells, however, we detected their metabolic activity through the analysis of cellular mRNA, which suggests that cells may have been rather in the active-but-nonculturable state (ABNC). We hypothesize that peroxidation of cell membrane lipids by the reactive species produced by plasma was an important pathway of bacterial inactivation. Amount of malondialdehyde and membrane permeability of E. coli to propidium iodide increased with increasing bacterial inactivation by plasma. Membrane damage was also demonstrated by detection of free DNA in plasma-treated water. PMID:25212700

  19. Analytical and computational investigations of airfoils undergoing high-frequency sinusoidal pitch and plunge motions at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    McGowan, Gregory Z.

    Current interests in Micro Air Vehicle (MAV) technologies call for the development of aerodynamic-design tools that will aid in the design of more efficient platforms that will also have adequate stability and control for flight in gusty environments. Influenced largely by nature MAVs tend to be very small, have low flight speeds, and utilize flapping motions for propulsion. For these reasons the focus is, specifically, on high-frequency motions at low Reynolds numbers. Toward the goal of developing design tools, it is of interest to explore the use of elementary flow solutions for simple motions such as pitch and plunge oscillations to predict aerodynamic performance for more complex motions. In the early part of this research, a validation effort was undertaken. Computations from the current effort were compared with experiments conducted in a parallel, collaborative effort at the Air Force Research Laboratory (AFRL). A set of pure-pitch and pure-plunge sinusoidal oscillations of the SD7003 airfoil were examined. Phase-averaged measurements using particle image velocimetry in a water tunnel were compared with computations using two flow solvers: (i) an incompressible Navier-Stokes Immersed Boundary Method and (ii) an unsteady compressible Reynolds-Averaged Navier-Stokes (RANS) solver. The motions were at a reduced frequency of k = 3.93, and pitch-angle amplitudes were chosen such that a kinematic equivalence in amplitudes of effective angle of attack (from plunge) was obtained. Plunge cases showed good qualitative agreement between computation and experiment, but in the pitch cases, the wake vorticity in the experiment was substantially different from that predicted by both computations. Further, equivalence between the pure-pitch and pure-plunge motions was not attained through matching effective angle of attack. With the failure of pitch/plunge equivalence using equivalent amplitudes of effective angle of attack, the effort shifted to include pitch-rate and wake-effect terms through the use of analytical methods including quasi-steady thin-airfoil theory (QSTAT) and Theodorsen's theory. These theories were used to develop three analytical approaches for determining pitch motions equivalent to plunge motions. A study of variation in plunge height was then examined and followed by a study of the effect of rotation point using the RANS solver. For the range of plunge heights studied, it was observed that kinematic matching between plunge and pitch using QSTAT gave outstanding similarities in flow field, while the matching performed using Theodorsen's theory gave the best equivalence in lift coefficients for all cases. The variation of rotation point revealed that, for the given plunge height, with rotation point in front of the mid-chord location, all three schemes matched flow-field vorticity well, and with rotation point aft of the mid-chord no scheme matched vorticity fields. However, for all rotation points (except for the mid-chord location), CFD prediction of lift coefficients from the Theodorsen matching scheme matched the lift time histories closely to CFD predictions for pure-pitch. Combined pitch and plunge motions were then examined using kinematic parameters obtained from the three schemes. The results showed that QSTAT nearly cancels the vortices emanating from the trailing edge. Theodorsen's matching approach was successful in generating a lift that was close to constant over the entire cycle. Additionally this approach showed the presence of the reverse Karman vortex sheet through the wake. Combined pitch/plunge motions were then analyzed, computationally and experimentally, with a non-zero mean angle of attack. All computational results compared excellently with experiments, capturing vorticity production on the airfoil's surface and through the wake. Lift coefficient through a cycle was shown to tend toward a constant using Theodorsen's parameters, with the constant being dependent on the initial angle of attack. This result points to the possibility of designing an unsteady motion to match a given flig

  20. Coal liquefaction to increase jet fuel production

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Processing concept that increases supply of jet fuel has been developed as part of study on methods for converting coal to hydrogen, methane, and jet fuel. Concept takes advantage of high aromatic content of coal-derived liquids to make high-octane gasoline, instead of destroying aromatics to make jet fuel.

  1. Feedback control of a pitching and plunging airfoil via direct numerical simulation

    NASA Astrophysics Data System (ADS)

    Dawson, Scott; Brunton, Steven; Rowley, Clarence

    2012-11-01

    Feedback control is implemented in direct numerical simulations at a Reynolds number of 100 to allow a two-dimensional flat plate airfoil to track desired lift profiles using pitching and plunging motions. Robust controllers are designed using both classical models (Theodorsen) and empirical reduced-order models identified from direct numerical simulations. We investigate the capabilities of a variety of controllers for plunging motion and for pitching about different pitch axis locations. Effective control is achieved across a wide range of angles of attack, despite strongly nonlinear flow physics. The forces caused by rapid airfoil motion may be utilized to achieve high lift coefficients for short periods of time. It is also possible to track periodic lift profiles with average lift coefficients that are significantly greater than those achieved by a steady airfoil. The enhanced lift that arises at certain frequencies appears to be caused by favorable interaction of wake vortices. The ability of the controllers to reject gust disturbances and attenuate sensor noise is also investigated, which is relevant for the implementation of such controllers in an experimental setting. This work is supported by AFOSR grant FA9550-12-1-0075.

  2. Vorticity transport and the leading-edge vortex of a plunging airfoil

    NASA Astrophysics Data System (ADS)

    Eslam Panah, Azar; Akkala, James M.; Buchholz, James H. J.

    2015-08-01

    The three-dimensional flow field was experimentally characterized for a nominally two-dimensional flat-plate airfoil plunging at large amplitude and reduced frequencies, using three-dimensional reconstructions of planar PIV data at a chord-based Reynolds number of 10,000. Time-resolved, instantaneous PIV measurements reveal that secondary vorticity, of opposite sign to the primary vortex, is intermittently entrained into the leading-edge vortex (LEV) throughout the downstroke, with the rate of entrainment increasing toward the end of the stroke when the leading-edge shear layer weakens. A planar vorticity transport analysis around the LEV indicated that, during the downstroke, the surface vorticity flux due to the pressure gradient is consistently about half that due to the leading-edge shear layer for all parameter values investigated, demonstrating that production and entrainment of secondary vorticity is an important mechanism regulating LEV strength. A small but non-negligible vorticity source was also attributed to spanwise flow toward the end of the downstroke. Aggregate vortex tilting is notably more significant for higher plunge frequencies, suggesting that the vortex core is more three-dimensional.

  3. Effects of kinematics on aerodynamic periodicity for a periodically plunging airfoil

    NASA Astrophysics Data System (ADS)

    Wu, Jianghao; Wang, Dou; Zhang, Yanlai

    2015-12-01

    In conventional Micro-Air-Vehicle design inspired by insects, the periodical motion of flapping airfoil usually leads to generation of a periodical aerodynamic force. However, recent studies indicate that time courses of aerodynamic force and flow structure of a flapping airfoil may be non-periodical even though the airfoil undergoes a periodical motion. In this paper, a computational fluid dynamics analysis is employed to investigate the effects of some dimensionless variables, such as Reynolds number, plunging amplitude, advance ratio, and angle of attack, on the periodicity of the flow around a flapping airfoil. The governing equations in an inertial frame of reference are solved to obtain unsteady flow structure and aerodynamic behaviors of the airfoil. It is found in the results that the periodicity of the flow and aerodynamics is greatly dependent on Reynolds number and plunging amplitude. Under given conditions, the product of these two variables may be utilized as a criterion parameter to judge whether the time course of the flow is periodical or not. In addition, a new mechanism that accounts for the non-periodical flow is revealed to explain the flow of airfoil with pre-stall angle of attack.

  4. Lattice Boltzmann simulation of dynamics of plunge and pitch of 3D flexible wing

    NASA Astrophysics Data System (ADS)

    Qi, Dewei; Shyy, Wei

    2008-11-01

    The method of lattice Boltzmann (LB) simulation has been used to simulate fluid structures and motion of a flexible insect wing in a 3D space. In the method, a beam has been discretized into a chain of rigid segments. Each segment is connected through ball and socket joints at its ends. One segment may be bent and twisted with its neighboring segment. A constraint force is applied to each joint to ensure the solid structure moving as a whole flexible elastic body.We have demonstrated that the LB method is suitable for modeling of aerodynamics of insects flight at low Reynolds numbers. First, a simulation of plunging and pitching of a rigid wing is performed at Re=75 in a 2D space and the results of lift forces and flow structures are in excellent agreement with the previous results. Second, plunging and pitching of a flexible wing in span-wise direction is simulated at Re=136 in a 3D space. We found that when twisting elasticity is large enough the twisting angle could be controlled at a level of smaller than 0.2 degree. It is shown that as bending and twisting elasticity is large enough, the motion of flexible wing approaches that of a rigid membrane wing. The simulation results show that the optimization of flexibility in span-wise direction will benefit thrust and an intermediate level is favorable. The results are consistent with experimental finding.

  5. Energy Exchange during Plunge/Surge Motions of a 2D Wing

    NASA Astrophysics Data System (ADS)

    Kerstens, Wesley; Choi, Jeesoon; Colonius, Tim; Williams, David

    2011-11-01

    The rate of energy transfer between an NACA-0006 wing and an unsteady flow is examined at pre-stall and post-stall conditions using numerical simulations and wind tunnel experiments. The plunge and surge motions simulate the fluctuating vertical (wz) and longitudinal (wx) velocity components of a wind gust. In a steady flow the wing loses energy to the flow through the drag power term, but in an unsteady flow the wing may gain energy from the fluctuating lift power and fluctuating drag power terms. The net energy transfer averaged over the period of oscillation depends on the phase angle between the plunge and surge motions. The largest increase of energy occurs when wx and wz are in-phase. When the fluctuations are large enough, then it is possible for the net energy gain to be positive. The numerical simulations conducted at Reynolds numbers near the critical value for vortex shedding show qualitative agreement with the experiments. The simulations highlight the role of vortex shedding in determining the optimal frequency and phase for energy extraction from the gust. Support of the AFOSR through grant FA9550-09-1-0189 managed by Dr. Douglas Smith is gratefully acknnowledged.

  6. Vortex diode jet

    DOEpatents

    Houck, Edward D. (Idaho Falls, ID)

    1994-01-01

    A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

  7. Optimization of anaerobic co-digestion of olive mill wastewater and liquid poultry manure in batch condition and semi-continuous jet-loop reactor.

    PubMed

    Khoufi, Sonia; Louhichi, Assawer; Sayadi, Sami

    2015-04-01

    Anaerobic co-digestion of olive mill wastewater (OMW) with liquid poultry manure (LPM) was investigated in a jet-loop reactor (JLR) as a new approach for upgrading the efficiency of bioprocess. Optimum proportion of LPM was evaluated by determining biochemical methane potential. Methane yields were compared by applying one way ANOVA method followed by post hoc Tukey's test with a 0.05 significance level. Results demonstrated that the addition of LPM at proportion of 10% and 30% (v/v) improved methane yield of OMW digestion but differences between these mixtures and raw OMW are not significant. JLR results confirmed that the proportion 30% LPM gives the optimum condition for excellent stability of digester. Methane production was significantly high until an organic loading rate of 9.5 gCOD/L reactor/day. Overall; this study indicates the technical feasibility and effectiveness of using JLR as one-stage anaerobic system for the co-digestion of OMW and LPM. PMID:25682225

  8. An archival study of eyewitness memory of the Titanic's final plunge.

    PubMed

    Riniolo, Todd C; Koledin, Myriah; Drakulic, Gregory M; Payne, Robin A

    2003-01-01

    A handful of real-life studies demonstrate that most eyewitnesses accurately recall central details (i.e., the gist of what happened) from traumatic events. The authors evaluated the accuracy of archival eyewitness testimony from survivors of the Titanic disaster who witnessed the ship's final plunge. The results indicate that most eyewitness testimony (15 eyewitnesses of 20) is consistent with forensic evidence that demonstrates that the Titanic was breaking apart while it was still on the ocean's surface. Despite the methodological limitations of archival research, the authors provide evidence from a single-occurrence traumatic event (with a large-scale loss of life) that the majority of eyewitnesses accurately recall central details. PMID:12635858

  9. Numerical investigation of the vertical plunging force of a spherical intruder into a prefluidized granular bed

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Padding, J. T.; Kuipers, J. A. M.

    2014-12-01

    The plunging of a large intruder sphere into a prefluidized granular bed with various constant velocities and various sphere diameters is investigated using a state-of-the-art hybrid discrete particle and immersed boundary method, in which both the gas-induced drag force and the contact force exerted on the intruder can be investigated separately. We investigate low velocities, where velocity dependent effects first begin to appear. The results show a concave-to-convex dependence of the plunging force as a function of intruder depth. In the concave region the force fits to a power law with an exponent around 1.3, which is in good agreement with existing experimental observations. Our simulation results further show that the force exerted on the frontal hemisphere of the intruder is dominant. At larger intruder velocities, friction with the granular medium causes a velocity-dependent drag force. As long as the granular particles have not yet closed the gap behind the intruder, this drag force is independent of the actual intruder depth. In this regime, the drag force experienced by intruders of different diameter moving at different velocities all fall onto a single master curve if plotted against the Reynolds number, using a single value for the effective viscosity of the granular medium. This master curve corresponds well to the Schiller-Naumann correlation for the drag force between a sphere and a Newtonian fluid. After the gap behind the intruder has closed, the drag force increases not only with velocity but also with depth. We attribute this to the effect of increasing hydrostatic particle pressure in the granular medium, leading to an increase in effective viscosity.

  10. Experimental study of pitching and plunging airfoils at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Baik, Yeon Sik; Bernal, Luis P.

    2012-12-01

    Measurements of the unsteady flow structure and force time history of pitching and plunging SD7003 and flat plate airfoils at low Reynolds numbers are presented. The airfoils were pitched and plunged in the effective angle of attack range of 2.4-13.6 (shallow-stall kinematics) and -6 to 22 (deep-stall kinematics). The shallow-stall kinematics results for the SD7003 airfoil show attached flow and laminar-to-turbulent transition at low effective angle of attack during the down stroke motion, while the flat plate model exhibits leading edge separation. Strong Re-number effects were found for the SD7003 airfoil which produced approximately 25 % increase in the peak lift coefficient at Re = 10,000 compared to higher Re flows. The flat plate airfoil showed reduced Re effects due to leading edge separation at the sharper leading edge, and the measured peak lift coefficient was higher than that predicted by unsteady potential flow theory. The deep-stall kinematics resulted in leading edge separation that led to formation of a large leading edge vortex (LEV) and a small trailing edge vortex (TEV) for both airfoils. The measured peak lift coefficient was significantly higher (~50 %) than that for the shallow-stall kinematics. The effect of airfoil shape on lift force was greater than the Re effect. Turbulence statistics were measured as a function of phase using ensemble averages. The results show anisotropic turbulence for the LEV and isotropic turbulence for the TEV. Comparison of unsteady potential flow theory with the experimental data showed better agreement by using the quasi-steady approximation, or setting C( k) = 1 in Theodorsen theory, for leading edge-separated flows.

  11. The Cultural Plunge: Cultural Immersion as a Means of Promoting Self-Awareness and Cultural Sensitivity among Student Teachers

    ERIC Educational Resources Information Center

    Nieto, Jesus

    2006-01-01

    Plunges represent a type of education that is experiential, meaningful, interesting, challenging, confidence-building, growth-inducing and rewarding for most students. They represent a significant means towards students' greater understanding and acceptance of others, as well as of enhancing self-awareness; they thus have great potential as a

  12. Visual accommodation and active pursuit of prey underwater in a plunge-diving bird: the Australasian gannet

    PubMed Central

    Machovsky-Capuska, Gabriel E.; Howland, Howard C.; Raubenheimer, David; Vaughn-Hirshorn, Robin; Wrsig, Bernd; Hauber, Mark E.; Katzir, Gadi

    2012-01-01

    Australasian gannets (Morus serrator), like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. Prey are captured underwater either in the momentum (M) phase of the dive while descending through the water column, or the wing flapping (WF) phase while moving, using the wings for propulsion. Detection of prey from the air is clearly visually guided, but it remains unknown whether plunge diving birds also use vision in the underwater phase of the dive. Here we address the question of whether gannets are capable of visually accommodating in the transition from aerial to aquatic vision, and analyse underwater video footage for evidence that gannets use vision in the aquatic phases of hunting. Photokeratometry and infrared video photorefraction revealed that, immediately upon submergence of the head, gannet eyes accommodate and overcome the loss of greater than 45 D (dioptres) of corneal refractive power which occurs in the transition between air and water. Analyses of underwater video showed the highest prey capture rates during WF phase when gannets actively pursue individual fish, a behaviour that very likely involves visual guidance, following the transition after the plunge dive's M phase. This is to our knowledge the first demonstration of the capacity for visual accommodation underwater in a plunge diving bird while capturing submerged prey detected from the air. PMID:22874749

  13. Visual accommodation and active pursuit of prey underwater in a plunge-diving bird: the Australasian gannet.

    PubMed

    Machovsky-Capuska, Gabriel E; Howland, Howard C; Raubenheimer, David; Vaughn-Hirshorn, Robin; Wrsig, Bernd; Hauber, Mark E; Katzir, Gadi

    2012-10-22

    Australasian gannets (Morus serrator), like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. Prey are captured underwater either in the momentum (M) phase of the dive while descending through the water column, or the wing flapping (WF) phase while moving, using the wings for propulsion. Detection of prey from the air is clearly visually guided, but it remains unknown whether plunge diving birds also use vision in the underwater phase of the dive. Here we address the question of whether gannets are capable of visually accommodating in the transition from aerial to aquatic vision, and analyse underwater video footage for evidence that gannets use vision in the aquatic phases of hunting. Photokeratometry and infrared video photorefraction revealed that, immediately upon submergence of the head, gannet eyes accommodate and overcome the loss of greater than 45 D (dioptres) of corneal refractive power which occurs in the transition between air and water. Analyses of underwater video showed the highest prey capture rates during WF phase when gannets actively pursue individual fish, a behaviour that very likely involves visual guidance, following the transition after the plunge dive's M phase. This is to our knowledge the first demonstration of the capacity for visual accommodation underwater in a plunge diving bird while capturing submerged prey detected from the air. PMID:22874749

  14. Water Jetting

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Hi-Tech Inc., a company which manufactures water jetting equipment, needed a high pressure rotating swivel, but found that available hardware for the system was unsatisfactory. They were assisted by Marshall, which had developed water jetting technology to clean the Space Shuttles. The result was a completely automatic water jetting system which cuts rock and granite and removes concrete. Labor costs have been reduced; dust is suppressed and production has been increased.

  15. Gravitomagnetic jets

    SciTech Connect

    Chicone, C.; Mashhoon, B.

    2011-03-15

    We present a family of dynamic rotating cylindrically symmetric Ricci-flat gravitational fields whose geodesic motions have the structure of gravitomagnetic jets. These correspond to helical motions of free test particles up and down parallel to the axis of cylindrical symmetry and are reminiscent of the motion of test charges in a magnetic field. The speed of a test particle in a gravitomagnetic jet asymptotically approaches the speed of light. Moreover, numerical evidence suggests that jets are attractors. The possible implications of our results for the role of gravitomagnetism in the formation of astrophysical jets are briefly discussed.

  16. Test Cases for Flutter of the Benchmark Models Rectangular Wings on the Pitch and Plunge Apparatus

    NASA Technical Reports Server (NTRS)

    Bennett, Robert M.

    2000-01-01

    The supercritical airfoil was chosen as a relatively modem airfoil for comparison. The BOO12 model was tested first. Three different types of flutter instability boundaries were encountered, a classical flutter boundary, a transonic stall flutter boundary at angle of attack, and a plunge instability near M = 0.9 and for zero angle of attack. This test was made in air and was Transonic Dynamics Tunnel (TDT) Test 468. The BSCW model (for Benchmark SuperCritical Wing) was tested next as TDT Test 470. It was tested using both with air and a heavy gas, R-12, as a test medium. The effect of a transition strip on flutter was evaluated in air. The B64AOlO model was subsequently tested as TDT Test 493. Some further analysis of the experimental data for the BOO12 wing is presented. Transonic calculations using the parameters for the BOO12 wing in a two-dimensional typical section flutter analysis are given. These data are supplemented with data from the Benchmark Active Controls Technology model (BACT) given and in the next chapter of this document. The BACT model was of the same planform and airfoil as the BOO12 model, but with spoilers and a trailing edge control. It was tested in the heavy gas R-12, and was instrumented mostly at the 60 per cent span. The flutter data obtained on PAPA and the static aerodynamic test cases from BACT serve as additional data for the BOO12 model. All three types of flutter are included in the BACT Test Cases. In this report several test cases are selected to illustrate trends for a variety of different conditions with emphasis on transonic flutter. Cases are selected for classical and stall flutter for the BSCW model, for classical and plunge for the B64AOlO model, and for classical flutter for the BOO12 model. Test Cases are also presented for BSCW for static angles of attack. Only the mean pressures and the real and imaginary parts of the first harmonic of the pressures are included in the data for the test cases, but digitized time histories have been archived. The data for the test cases are available as separate electronic files. An overview of the model and tests is given, the standard formulary for these data is listed, and some sample results are presented.

  17. Low electrical resistivity associated with plunging of the Nazca flat slab beneath Argentina.

    PubMed

    Booker, John R; Favetto, Alicia; Pomposiello, M Cristina

    2004-05-27

    Beneath much of the Andes, oceanic lithosphere descends eastward into the mantle at an angle of about 30 degrees (ref. 1). A partially molten region is thought to form in a wedge between this descending slab and the overlying continental lithosphere as volatiles given off by the slab lower the melting temperature of mantle material. This wedge is the ultimate source for magma erupted at the active volcanoes that characterize the Andean margin. But between 28 degrees and 33 degrees S the subducted Nazca plate appears to be anomalously buoyant, as it levels out at about 100 km depth and extends nearly horizontally under the continent. Above this 'flat slab', volcanic activity in the main Andean Cordillera terminated about 9 million years ago as the flattening slab presumably squeezed out the mantle wedge. But it is unknown where slab volatiles go once this happens, and why the flat slab finally rolls over to descend steeply into the mantle 600 km further eastward. Here we present results from a magnetotelluric profile in central Argentina, from which we infer enhanced electrical conductivity along the eastern side of the plunging slab, indicative of the presence of partial melt. This conductivity structure may imply that partial melting occurs to at least 250 km and perhaps to more than 400 km depth, or that melt is supplied from the 410 km discontinuity, consistent with the transition-zone 'water-filter' model of Bercovici and Karato. PMID:15164059

  18. Pursuit plunging by northern gannets (Sula bassana) feeding on capelin (Mallotus villosus).

    PubMed

    Garthe, S; Benvenuti, S; Montevecchi, W A

    2000-09-01

    Northern gannets (Sula bassana) are considered to obtain prey usually by rapid, vertical, shallow plunge dives. In order to test this contention and investigate underwater foraging behaviour, we attached two types of data-logging systems to 11 parental northern gannets at Funk Island in the North-Wiest Atlantic. We documented, for the first time to the authors' knowledge, gannets performing long, flat-bottomed, U-shaped dives that involved underwater wing propulsion as well as rapid, shallow, V-shaped dives. The median and maximum dive depths and durations were 4.6 and 22.0 m and 8 and 38 s, respectively. Short, shallow dives were usually V-shaped and dives deeper than 8 m and longer than 10 s were usually U-shaped, including a period at constant depth (varying between 4 and 28s with median 8s). Diving occurred throughout the daylight period and deepest dives were performed during late morning. On the basis of motion sensors in the loggers and food collections from telemetered birds, we concluded that extended, deep dives were directed at deep schools of capelin, a small pelagic fish, and we hypothesized that V-shaped dives were aimed at larger, pelagic fishes and squids. Furthermore, these V-shaped dives allowed the birds to surprise their pelagic prey and this may be critical because the maximum swimming speeds of the prey species may exceed the maximum dive speeds of the birds. PMID:12233767

  19. Volumetric measurements and simulations of the vortex structures generated by low aspect ratio plunging wings

    NASA Astrophysics Data System (ADS)

    Calderon, D. E.; Wang, Z.; Gursul, I.; Visbal, M. R.

    2013-06-01

    Volumetric three-component velocimetry measurements have been performed on low aspect ratio wings undergoing a small amplitude pure plunging motion. This study focuses on the vortex flows generated by rectangular and elliptical wings set to a fixed geometric angle of attack of ? = 20. An investigation into the effect of Strouhal number illustrates the highly three-dimensional nature of the leading edge vortex as well as its inherent ability to improve lift performance. Computational simulations show good agreement with experimental results, both demonstrating the complex interaction between leading, trailing, and tip vortices generated in each cycle. The leading edge vortex, in particular, may deform significantly throughout the cycle, in some cases developing strong spanwise undulations. These are at least both Strouhal number and planform dependent. One or two arch-type vortical structures may develop, depending on the aspect ratio and Strouhal number. At sufficiently high Strouhal numbers, a tip vortex ring may also develop, propelling itself away from the wing in the spanwise direction due to self-induced velocity.

  20. The Development of Gullies on the Landscape: a Model of Headcut Retreat Resulting From Plunge Pool Erosion

    NASA Astrophysics Data System (ADS)

    Flores Cervantes, J. H.; Istanbulluoglu, E.; Bras, R.

    2004-12-01

    Head advance due to plunge-pool erosion is a common process in gullies incising resistant soils. A model of headcut retreat resulting from plunge-pool erosion is developed and implemented in CHILD, an existing 3D landscape evolution modeling framework. The model estimates horizontal headcut retreat as a function of discharge, height of the headcut, upstream slope and relevant land surface and soil properties for soil erosion. The physical model results compare well with the published data from flume experiments. We analyzed the sensitivity of headcut retreat to flow discharge, upstream slope and surface roughness, and headcut height. CHILD simulations indicate that headcut retreat is most significant in zones with either gentle slopes or large headcut heights. Model parameters have contrasting effects on the retreat rates depending on the size and depth of the pool beneath the headcut, and upstream flow hydraulics, making the process difficult to predict as a function of topographic thresholds and simple geomorphic transport laws.

  1. Axial jet mixing of ethanol in cylindrical containers during weightlessness

    NASA Technical Reports Server (NTRS)

    Aydelott, J. C.

    1979-01-01

    An experimental program was conducted to examine the liquid flow patterns that result from the axial jet mixing of ethanol in 10-centimeter-diameter cylindrical tanks in weightlessness. A convex hemispherically ended tank and two Centaur liquid-hydrogen-tank models were used for the study. Four distinct liquid flow patterns were observed to be a function of the tank geometry, the liquid-jet velocity, the volume of liquid in the tank, and the location of the tube from which the liquid jet exited.

  2. Axial jet mixing of ethanol in spherical containers during weightlessness

    NASA Technical Reports Server (NTRS)

    Audelott, J. C.

    1976-01-01

    An experimental program was conducted to examine the liquid flow patterns that result from the axial jet mixing of ethanol in 10-centimeter-diameter spherical containers in weightlessness. Complete liquid circulation flow patterns were easily established in containers that were less than half full of liquid, while for higher liquid fill conditions, vapor was drawn into the inlet of the simulated mixer unit. Increasing the liquid-jet or lowering the position at which the liquid jet entered the container caused increasing turbulence and bubble formation.

  3. Is there a clinical benefit with a smooth compensator design compared with a plunged compensator design for passive scattered protons?

    PubMed

    Tabibian, Art A; Powers, Adam; Dolormente, Keith; Oommen, Sneha; Tiwari, Akhil; Palmer, Matt; Zhu, Xiaorong R; Li, Heng; Sahoo, Narayan; Wisdom, Paul; Velasco, Kyle; Erhart, Kevin; Stanley, Henry; Nguyen, Bao-Ngoc T

    2015-01-01

    In proton therapy, passive scattered proton plans use compensators to conform the dose to the distal surface of the planning volume. These devices are custom made from acrylic or wax for each treatment field using either a plunge-drilled or smooth-milled compensator design. The purpose of this study was to investigate if there is a clinical benefit of generating passive scattered proton radiation treatment plans with the smooth compensator design. We generated 4 plans with different techniques using the smooth compensators. We chose 5 sites and 5 patients for each site for the range of dosimetric effects to show adequate sample. The plans were compared and evaluated using multicriteria (MCA) plan quality metrics for plan assessment and comparison using the Quality Reports [EMR] technology by Canis Lupus LLC. The average absolute difference for dosimetric metrics from the plunged-depth plan ranged from -4.7 to +3.0 and the average absolute performance results ranged from -6.6% to +3%. The manually edited smooth compensator plan yielded the best dosimetric metric, +3.0, and performance, + 3.0% compared to the plunged-depth plan. It was also superior to the other smooth compensator plans. Our results indicate that there are multiple approaches to achieve plans with smooth compensators similar to the plunged-depth plans. The smooth compensators with manual compensator edits yielded equal or better target coverage and normal tissue (NT) doses compared with the other smooth compensator techniques. Further studies are under investigation to evaluate the robustness of the smooth compensator design. PMID:25263491

  4. Waveforms produced by a scalar point particle plunging into a Schwarzschild black hole: Excitation of quasinormal modes and quasibound states

    NASA Astrophysics Data System (ADS)

    Décanini, Yves; Folacci, Antoine; Ould El Hadj, Mohamed

    2015-07-01

    With the possibility of testing massive gravity in the context of black hole physics in mind, we consider the radiation produced by a particle plunging from slightly below the innermost stable circular orbit into a Schwarzschild black hole. In order to circumvent the difficulties associated with black hole perturbation theory in massive gravity, we use a toy model in which we replace the graviton field with a massive scalar field and consider a linear coupling between the particle and this field. We compute the waveform generated by the plunging particle and study its spectral content. This permits us to highlight and interpret some important effects occurring in the plunge regime which are not present for massless fields, such as (i) the decreasing and vanishing, as the mass parameter increases, of the signal amplitude generated when the particle moves on quasicircular orbits near the innermost stable circular orbit; and (ii) in addition to the excitation of the quasinormal modes, the excitation of the quasibound states of the black hole.

  5. Strong transient effects of the flow around a harmonically plunging NACA0012 airfoil at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The flow pattern around a NACA0012 airfoil undergoing harmonic plunging motion corresponding to the deflected wake phenomenon reported by Jones and Platzer (Exp Fluids 46:799-810, 2009) is investigated in detail using direct numerical simulations. An arbitrary Lagrangian-Eulerian formulation based on an unstructured side-centered finite volume method is utilized in order to solve the incompressible unsteady Navier-Stokes equations. The Reynolds number is chosen to be 252, and the reduced frequency of plunging motion ( k = 2π fc/ U ∞) and the plunge amplitude non-dimensionalized with respect to chord are set to be 12.3 and 0.12, respectively, as in the experimental study of Jones and Platzer (2009). The present numerical simulations reveal a highly persistent transient effect, and it takes two orders of magnitude larger duration than the heave period to reach the time-periodic state. In addition, the three-dimensional simulation reveals that the flow field is three-dimensional for the parameters used herein. The calculation reproduces the deflected wake and shows a good agreement with the experimental wake pattern. The instantaneous vorticity contours, finite-time Lyapunov exponent fields and particle traces are presented along with the aerodynamic parameters including the lift and thrust coefficients.

  6. The flow structure in the near field of jets and its effect on cavitation inception, and, Implementation of ferroelectric liquid crystal and birefringent crystal for image shifting in particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Gopalan, Shridhar

    1999-10-01

    Cavitation experiments performed in the near field of a 50-mm diameter (D) jet at ReD = 5 × 105, showed inception in the form of inclined ``cylindrical'' bubbles at axial distances (x/D) less than 0.55, with indices of 2.5. On tripping the boundary layer, cavitation inception occurred at x/D ~ 2, as distorted ``spherical'' bubbles with inception indices of 1.7. To investigate these substantial differences, the near field of the jet was measured using Particle Image Velocimetry (PIV). Data on the primary flow, the strength distribution of the ``streamwise''vortices and the velocity profiles within the initial boundary layers were obtained. The untripped case showed a direct transition to three-dimensional flow in the near field (x/D < 0.7) even before rolling up to distinct vortex rings. Strong ``streamwise'' vortices with strengths up to 25% of the jet velocity times the characteristic wavelength were seen. Cavitation inception occurred in the core of these vortices. In contrast, in the tripped jet the vortex sheet rolled up to the familiar Kelvin- Helmholtz vortex rings with weak secondary vortices. Using the measured nuclei distribution, strengths and straining of the ``streamwise'' structures, the rates of cavitation events were estimated. The estimated results match very well with the measured cavitation rates. Also, the Reynolds stresses in the near field of the jet show similar trends and magnitudes to those of Browand & Latigo (1979) and Bell & Mehta (1990) for a plane shear layer. In the second part of this essay we discuss the implementation of electro-optical image shifting to resolve directional ambiguity in PIV measurements. The technique uses a ferroelectric liquid crystal (FLC) as an electro-optic half wave plate and a birefringent crystal (calcite) as the shifter. The system can be used with non-polarized light sources and fluorescent particles. The minimum shifting time is approximately 100μs. This compact electrooptical device usually is positioned in front of the camera lens, though it has also been mounted inside the lens body. This device extensively was used to acquire data in the near field of the jet, which is discussed in Chapter 2. Sample vector maps from a turbulent multidirectional flow are also included.

  7. Business Jet

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The Citation Jet, developed by Cessna Aircraft Company, Wichita, KS, is the first business jet to employ Langley Research Center's natural laminar flow (NLF) technology. NLF reduces drag and therefore saves fuel by using only the shape of the wing to keep the airflow smooth, or laminar. This reduces friction between the air and wing, and therefore, reduces drag. NASA's Central Industrial Applications Center, Rural Enterprises, Inc., Durant, OK, its Kansas affiliate, and Wichita State University assisted in the technology transfer.

  8. Vortex diode jet performance and theory

    SciTech Connect

    Houck, E.D.

    1993-12-01

    Fluidics is the technology dealing with the use of a flowing liquid or gas in various devices for controls and fluid transfers. Existing fluidic technology transfers fluid at approximately the same rate as air lifts and jets. A vortex diode combined in parallel with a jet (vortex diode jet) produces significantly higher transfer rates` and retains the fluidic system advantages. This paper presents the proof of concept research and gives design parameters for the vortex diode jet. The goal of this research was to develop a vortex diode jet that would improve fluidic system transfer rates, and to develop and verify the,design equations. Proven design equations could then be used to design, and model vortex diode jet systems. This research has shown that vortex diode jets improve fluidic system transfer rate by up to 60 percent and can be modelled with the design equations.

  9. Synthetic jets

    NASA Astrophysics Data System (ADS)

    Glezer, Ari; Amitay, Michael

    The evolution of a synthetic (zero-net mass flux) jet and the flow mechanisms of its interaction with a cross flow are reviewed. An isolated synthetic jet is produced by the interactions of a train of vortices that are typically formed by alternating momentary ejection and suction of fluid across an orifice such that the net mass flux is zero. A unique feature of these jets is that they are formed entirely from the working fluid of the flow system in which they are deployed and, thus, can transfer linear momentum to the flow system without net mass injection across the flow boundary. Synthetic jets can be produced over a broad range of length and timescale, and their unique attributes make them attractive fluidic actuators for a number of flow control applications. The interaction of synthetic jets with an external cross flow over the surface in which they are mounted can displace the local streamlines and induce an apparent or virtual change in the shape of the surface, thereby effecting flow changes on length scales that are one to two orders of magnitude larger than the characteristic scale of the jets. This control approach emphasizes an actuation frequency that is high enough so that the interaction domain between the actuator and the cross flow is virtually invariant on the global timescale of the flow, and therefore, global effects such as changes in aerodynamic forces are effectively decoupled from the operating frequency of the actuators.

  10. Dynamic rhinoplasty for the plunging nasal tip: functional unity of the inferior third of the nose.

    PubMed

    Arregui, J S; Elejalde, M V; Regalado, J; Ezquerra, F; Berrazueta, M

    2000-12-01

    To achieve permanent results for the correction of a drooping nasal tip, it is important to understand the mechanism responsible for the caudal rotation of the tip when a person speaks or smiles. This mechanism can be considered to depend on a "functional unity" formed by three components: (1) the cartilaginous framework (alar cartilages and accessories acting as a single structure); (2) muscular motors (m. levator labii superioris alaeque nasi and depressor septi nasi); and (3) gliding areas (apertura piriformis, the valvular mechanism between the upper lateral cartilages and alar cartilages, the lax tissue of the nasal dorsum, and the membranous septum). We describe a new anatomical and functional concept responsible for the plunging of the nasal tip. When a person smiles, the functional unit is activated by a combination of two forces acting simultaneously in opposite directions that rotate the tip caudally and elevate the nasal base. The levator moves the alar base upward and the depressor pulls the tip caudally. To correct the drooping tip, the transcartilaginous incision is extended laterally, and the lateral portion of the alar arch is dissected free from the skin and the mucosa, thus exposing the accessory cartilages. The arch is then severed at the level of the accessories to allow the cephalad rotation of the domes. The muscle insertions are dissected free from the accessories and a section of the muscle and, if necessary, the accessory cartilages, is removed. From January of 1991 onward, 312 patients have had this ancillary procedure performed in addition to the basic rhinoplasty technique. PMID:11129196

  11. Unsteady Aerodynamic Testing Using the Dynamic Plunge Pitch and Roll Model Mount

    NASA Technical Reports Server (NTRS)

    Lutze, Frederick H.; Fan, Yigang

    1999-01-01

    A final report on the DyPPiR tests that were run are presented. Essentially it consists of two parts, a description of the data reduction techniques and the results. The data reduction techniques include three methods that were considered: 1) signal processing of wind on - wind off data; 2) using wind on data in conjunction with accelerometer measurements; and 3) using a dynamic model of the sting to predict the sting oscillations and determining the aerodynamic inputs using an optimization process. After trying all three, we ended up using method 1, mainly because of its simplicity and our confidence in its accuracy. The results section consists of time history plots of the input variables (angle of attack, roll angle, and/or plunge position) and the corresponding time histories of the output variables, C(sub L), C(sub D), C(sub m), C(sub l), C(sub m), C(sub n). Also included are some phase plots of one or more of the output variable vs. an input variable. Typically of interest are pitch moment coefficient vs. angle of attack for an oscillatory motion where the hysteresis loops can be observed. These plots are useful to determine the "more interesting" cases. Samples of the data as it appears on the disk are presented at the end of the report. The last maneuver, a rolling pull up, is indicative of the unique capabilities of the DyPPiR, allowing combinations of motions to be exercised at the same time.

  12. Soft X-Ray Temperature Tidal Disruption Events from Stars on Deep Plunging Orbits

    NASA Astrophysics Data System (ADS)

    Dai, Lixin; McKinney, Jonathan C.; Miller, M. Coleman

    2015-10-01

    One of the puzzles associated with tidal disruption event candidates (TDEs) is that there is a dichotomy between the color temperatures of a few × 104 K for TDEs discovered with optical and UV telescopes and the color temperatures of a few × 105-106 K for TDEs discovered with X-ray satellites. Here, we propose that high-temperature TDEs are produced when the tidal debris of a disrupted star self-intersects relatively close to the supermassive black hole, in contrast to the more distant self-intersection that leads to lower color temperatures. In particular, we note from simple ballistic considerations that greater apsidal precession in an orbit is the key to closer self-intersection. Thus, larger values of β, the ratio of the tidal radius to the pericenter distance of the initial orbit, are more likely to lead to higher temperatures of more compact disks that are super-Eddington and geometrically and optically thick. For a given star and β, apsidal precession also increases for larger black hole masses, but larger black hole masses imply a lower temperature at the Eddington luminosity. Thus, the expected dependence of the temperature on the mass of the black hole is non-monotonic. We find that in order to produce a soft X-ray temperature TDE, a deep plunging stellar orbit with β > 3 is needed and a black hole mass of ≲5 × 106M⊙ is favored. Although observations of TDEs are comparatively scarce and are likely dominated by selection effects, it is encouraging that both expectations are consistent with current data.

  13. Soft interactions in jet quenching

    NASA Astrophysics Data System (ADS)

    Hidalgo-Duque, Carlos; Llanes-Estrada, Felipe J.

    2015-04-01

    We study the collisional aspects of jet quenching in a high-energy nuclear collision, especially in the final state pion gas. The jet has a large energy, and acquires momentum transverse to its axis more effectively by multiple soft collisions than by few hard scatterings (as known from analogous systems such as J/ψ production at Hera). Such regime of large E and small momentum transfer corresponds to Regge kinematics and is characteristically dominated by the pomeron. From this insight we estimate the jet quenching parameter in the hadron medium (largely a pion gas) at the end of the collision, which is naturally small and increases with temperature in line with the gas density and compare it to the jet quenching parameter obtained within the quark-gluon plasma (QGP) phase in widely known perturbative approximations. The physics in the quark-gluon plasma/liquid phase is less obvious, and here we revisit a couple of simple estimates that suggest indeed that the pomeron-mediated interactions are very relevant and should be included in analysis of the jet quenching parameter. Finally, since the occasional hard collisions produce features characteristic of a Lèvy flight in the q⊥2 plane perpendicular to the jet axis, we suggest one- and two-particle q⊥ correlations as interesting experimental probes sensitive to the nature (softness versus hardness) of the interactions of a jet inside the QGP.

  14. Gas-Jet Levitation Furnace

    NASA Technical Reports Server (NTRS)

    Ethridge, E. C.; Johnson, J. L.; Dunn, S. A.; Paquette, E. G.

    1982-01-01

    Gas jet levitates solid and viscous liquid spheroids at high temperatures in new contactless processing system. System can be used to observe high temperature transformations (for example, crystallization without contact with another solid surface) or in containerless studies to eliminate contamination by crucible.

  15. Synthetic Jets

    NASA Technical Reports Server (NTRS)

    Milanovic, Ivana M.

    2003-01-01

    Current investigation of synthetic jets and synthetic jets in cross-flow examined the effects of orifice geometry and dimensions, momentum-flux ratio, cluster of orifices, pitch and yaw angles as well as streamwise development of the flow field. This comprehensive study provided much needed experimental information related to the various control strategies. The results of the current investigation on isolated and clustered synthetic jets with and without cross-flow will be further analyzed and documented in detail. Presentations at national conferences and publication of peer- reviewed journal articles are also expected. Projected publications will present both the mean and turbulent properties of the flow field, comparisons made with the data available in an open literature, as well as recommendations for the future work.

  16. Shock induced jetting of micron sized bubbles

    NASA Astrophysics Data System (ADS)

    Ohl, Claus-Dieter; Ikink, Roy; Lohse, Detlef; Prosperetti, Andrea

    2002-11-01

    Gas bubbles having a radius between 10 mum and 100 mum and rising freely in water when being subjected to a shock front exhibit a liquid jetting phenomenon. The jet points in the direction of the propagating shock wave. A linear relationship between the jet length and the bubble radius is found and a lower bound of the averaged velocity of the liquid jet can be estimated to be between 50 m/s and 300 m/s increasing linearly for larger bubbles. In a later stage the jet breaks up and releases micron sized bubbles. In the course of shock wave mediated cell permeabilization this observation suggests a microinjection mechanism responsible for cell transfection when minute gas bubbles are present and exposed together with cells to shock waves.

  17. Destruction regimes of Sun-skimming and Sun-plunging comets

    NASA Astrophysics Data System (ADS)

    Brown, J.; Carlson, R.; Toner, M.

    2014-07-01

    We establish and model destruction regimes for close sun-grazers, i.e. comets of small enough perihelia (q ≤ a few R_⊙) and large enough mass (M_o ≥ 10^{13} g) to reach the inner solar corona or below. These can be divided into sun-skimming and sun-plunging according to whether their M_o,q values confine them to atmospheric densities n ≤ 10^{14}cm^{-3} where mass loss is dominated by insolative sublimation, or let them reach n≥ 10^{14}cm^{-3} where hydrodynamic interactions with the dense chromosphere take over (bow-shock-heated ablative mass loss, ram pressure pancaking and deceleration). Being rare, no sun-plungers have yet been detected but they are of potentially great interest. Recent years have seen the first direct monitoring of three sun-skimmers in the low corona by SDO at EUV wavelengths. Both sun-plungers and sun-skimmers offer novel diagnostics of both cometary and solar conditions. We show that, due to their much higher speeds than planetary impacts, sun-plungers are likely dominated by pancaking and ablative mass-loss, rather than deceleration, even for quite inefficient bow-shock heat transfer, but we obtain solutions for ablation- and deceleration-dominated, and for intermediate, cases. All involve rapid local deposition of nucleus kinetic energy and momentum within a few 100 km near the photosphere. This occurs at atmospheric density n_{peak}(cm^{-3})≈3×10^{16}(Xμ_{-2}^3M_{15})^{1/2} for incident mass M_o=10^{15}M_{15} g, incident angle θ = cos^{-1}(10^{-2}μ_{-2}) to the vertical, and parameter X ranges from 0.001 up to 1. Break-up into Y fragments reduces n_{peak} by a factor ≈ Y^{-1/3}. This deposition will drive hot rising 'airburst' plumes and internal helioseismic waves similar to magnetic flare effects. In the normal ablation-dominated case (small X) the hot airburst will exhibit essentially cometary abundances (metallicity Gt; solar). Though sun-skimmer nuclei are vaporized by 5800 K (≈ 0.6 eV/photon) photospheric sunlight, their dissociation, ionization and heating up to EUV temperatures (10-100 eV) have to involve chromospheric EUV (10 eV/photon), 2 MK coronal thermal conduction (200 eV/electron) and conversion of nucleus kinetic energy (2 keV/nucleon). Coronal heat flux may be important in small sun-skimmers with tenuous comae and tails but kinetic energy conversion must dominate in large ones like Lovejoy 2011.

  18. Liquid sampling system

    DOEpatents

    Larson, L.L.

    1984-09-17

    A conduit extends from a reservoir through a sampling station and back to the reservoir in a closed loop. A jet ejector in the conduit establishes suction for withdrawing liquid from the reservoir. The conduit has a self-healing septum therein upstream of the jet ejector for receiving one end of a double-ended cannula, the other end of which is received in a serum bottle for sample collection. Gas is introduced into the conduit at a gas bleed between the sample collection bottle and the reservoir. The jet ejector evacuates gas from the conduit and the bottle and aspirates a column of liquid from the reservoir at a high rate. When the withdrawn liquid reaches the jet ejector the rate of flow therethrough reduces substantially and the gas bleed increases the pressure in the conduit for driving liquid into the sample bottle, the gas bleed forming a column of gas behind the withdrawn liquid column and interrupting the withdrawal of liquid from the reservoir. In the case of hazardous and toxic liquids, the sample bottle and the jet ejector may be isolated from the reservoir and may be further isolated from a control station containing remote manipulation means for the sample bottle and control valves for the jet ejector and gas bleed. 5 figs.

  19. Liquid sampling system

    DOEpatents

    Larson, Loren L. (Idaho Falls, ID)

    1987-01-01

    A conduit extends from a reservoir through a sampling station and back to the reservoir in a closed loop. A jet ejector in the conduit establishes suction for withdrawing liquid from the reservoir. The conduit has a self-healing septum therein upstream of the jet ejector for receiving one end of a double-ended cannula, the other end of which is received in a serum bottle for sample collection. Gas is introduced into the conduit at a gas bleed between the sample collection bottle and the reservoir. The jet ejector evacuates gas from the conduit and the bottle and aspirates a column of liquid from the reservoir at a high rate. When the withdrawn liquid reaches the jet ejector the rate of flow therethrough reduces substantially and the gas bleed increases the pressure in the conduit for driving liquid into the sample bottle, the gas bleed forming a column of gas behind the withdrawn liquid column and interrupting the withdrawal of liquid from the reservoir. In the case of hazardous and toxic liquids, the sample bottle and the jet ejector may be isolated from the reservoir and may be further isolated from a control station containing remote manipulation means for the sample bottle and control valves for the jet ejector and gas bleed.

  20. Absolute instability of a viscous hollow jet.

    PubMed

    Gañán-Calvo, Alfonso M

    2007-02-01

    An investigation of the spatiotemporal stability of hollow jets in unbounded coflowing liquids, using a general dispersion relation previously derived, shows them to be absolutely unstable for all physical values of the Reynolds and Weber numbers. The roots of the symmetry breakdown with respect to the liquid jet case, and the validity of asymptotic models are here studied in detail. Asymptotic analyses for low and high Reynolds numbers are provided, showing that old and well-established limiting dispersion relations [J. W. S. Rayleigh, The Theory of Sound (Dover, New York, 1945); S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Dover, New York, 1961)] should be used with caution. In the creeping flow limit, the analysis shows that, if the hollow jet is filled with any finite density and viscosity fluid, a steady jet could be made arbitrarily small (compatible with the continuum hypothesis) if the coflowing liquid moves faster than a critical velocity. PMID:17358457

  1. A novel needleless liquid jet injection methodology for improving direct cardiac gene delivery: An optimization of parameters, AAV mediated therapy and investigation of host responses in ischemic heart failure

    NASA Astrophysics Data System (ADS)

    Fargnoli, Anthony Samuel

    Heart disease remains the leading cause of mortality and morbidity worldwide, with 22 million new patients diagnosed annually. Essentially, all present therapies have significant cost burden to the healthcare system, yet fail to increase survival rates. One key employed strategy is the genetic reprogramming of cells to increase contractility via gene therapy, which has advanced to Phase IIb Clinical Trials for advanced heart failure patients. It has been argued that the most significant barrier preventing FDA approval are resolving problems with safe, efficient myocardial delivery, whereby direct injection in the infarct and remote tissue areas is not clinically feasible. Here, we aim to: (1) Improve direct cardiac gene delivery through the development of a novel liquid jet device approach (2) Compare the new method against traditional IM injection with two different vector constructions and evaluate outcome (3) Evaluate the host response resulting from both modes of direct cardiac injection, then advance a drug/gene combination with controlled release nanoparticle formulations.

  2. X-ray absorption spectrum for guanosine- 5'-monophosphate in water solution in the vicinity of the nitrogen K-edge observed in free liquid jet in vacuum

    NASA Astrophysics Data System (ADS)

    Ukai, Masatoshi; Yokoya, Akinari; Fujii, Kentaro; Saitoh, Yuji

    2008-10-01

    A new spectroscopy for direct effect of radiation damage to nucleic acids such as DNA and RNA is underway using a liquid beam sample in vacuum combined with soft-X-ray synchrotron radiation. We show the X-ray absorption spectrum (XANES) of liquid phase water at X-ray photon energy in the vicinity of oxygen K-shell absorption edge obtained from total photoelectron yields ejected from a pure water beam. We confirm a "liquid sample in vacuum" for the present experiment by the measurements of the temperature dependence of the XANES spectrum for a liquid beam of pure water. Shown is the first measurement of the XANES spectrum for guanosine- 5'-monophosphate (GMP), which is one of the fundamental nucleotide unit for RNA, in water solution at X-ray photon energy in the vicinity of nitrogen K-shell absorption edge involved in the 'water-window' region, which corresponds to a selective excitation of guanine site.

  3. Helium jet dispersion to atmosphere

    NASA Technical Reports Server (NTRS)

    Khan, Hasna J.

    1986-01-01

    On the event of loss of vacuum guard of superinsulated helium dewar, high rate of heat transfer into the tank occurs. The rapid boiling of liquid helium causes the burst disk to rupture at four atmospheres and consequently the helium passes to the atmosphere through vent lines. The gaseous helium forms a vertical buoyant jet as it exits the vent line into a stagnant environment. Characterization of the gaseous jet is achieved by detailed analysis of the axial and radial dependence of the flow parameters.

  4. Cross-shore and Vertical Distribution of Turbulence Kinetic Energy in the Surf Zone Generated by Plunging Breakers

    NASA Astrophysics Data System (ADS)

    Cheng, J.; Wang, P.

    2012-12-01

    Breaking waves, especially plunging breakers, generate intense turbulence and is crucial in dissipating incident wave energy, and suspending and transporting sediment in the surf zone. Therefore quantifying breaking-induced turbulence kinetic energy (TKE) is essential in understanding surf zone processes. Surf zone experiment data collected at the Large-scale Sediment Transport Facility (LSTF) at the U.S. Army Engineer Research and Development Center were used here. Two LSTF cases, one regular (3 s period) and one irregular (3 s peak period) waves over a movable bed, are examined here. Both cases resulted in dominantly plunging type of breakers. Waves and 3-D currents were measured simultaneously at 10 cross-shore locations and throughout the water column, with a sampling rate of 20 Hz. In order to separate orbital wave motion from turbulent motion, ensemble averaging and moving averaging were conducted for regular and irregular wave cases, respectively. A 5-point moving average, with 3-point averaging at the crest and trough, provided an optimal method to resolve turbulence, while approximately 95% of the incident wave energy being accounted for. The TKE was calculated after removing the averaged motion from the raw data. Large TKE was generated at the surface associated with wave breaking and dissipated rapidly downward. The TKE decreased nearly 2 orders of magnitude downward within 15 cm. The TKE researched a minimum value at approximately 50%-80% of the water depth, and increased thereafter toward the bottom due to the generation of bed-induced turbulence.

  5. Marine Jet

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The marine turbine pump pictured is the Jacuzzi 12YJ, a jet propulsion system for pleasure or commercial boating. Its development was aided by a NASA computer program made available by the Computer Software Management and Information Center (COSMIC) at the University of Georgia. The manufacturer, Jacuzzi Brothers, Incorporated, Little Rock, Arkansas, used COSMIC'S Computer Program for Predicting Turbopump Inducer Loading, which enabled substantial savings in development time and money through reduction of repetitive testing.

  6. Impinging jets atomization

    NASA Technical Reports Server (NTRS)

    Ibrahim, E. A.; Przekwas, A. J.

    1991-01-01

    An analysis of the characteristics of the spray produced by an impinging-jet injector is presented. Predictions of the spray droplet size and distribution are obtained through studying the formation and disintegration of the liquid sheet formed by the impact of two cylindrical jets of the same diameter and momentum. Two breakup regimes of the sheet are considered depending on Weber number, with transition occurring at Weber numbers between 500 and 2000. In the lower Weber number regime, the breakup is due to Taylor cardioidal waves, while at Weber number higher than 2000, the sheet disintegration is by the growth of Kelvin-Helmholtz instability waves. Theoretical expressions to predict the sheet thickness and shape are derived for the low Weber number breakup regime. An existing mathematical analysis of Kelvin-Helmholtz instability of radially moving liquid sheets is adopted in the predictions of resultant drop sizes by sheet breakup at Weber numbers greater than 2000. Comparisons of present theoretical results with experimental measurements and empirical correlations reported in the literature reveal favorable agreement.

  7. DICHOTOMY OF SOLAR CORONAL JETS: STANDARD JETS AND BLOWOUT JETS

    SciTech Connect

    Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.; Falconer, David A.

    2010-09-01

    By examining many X-ray jets in Hinode/X-Ray Telescope coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H{alpha} macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major coronal mass ejections. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jets that were also caught in He II 304 A snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T {approx} 10{sup 4} - 10{sup 5} K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.

  8. Dichotomy of Solar Coronal Jets: Standard Jets and Blowout Jets

    NASA Technical Reports Server (NTRS)

    Moore, R. L.; Cirtain, J. W.; Sterling, A. C.; Falconer, D. A.

    2010-01-01

    By examining many X-ray jets in Hinode/XRT coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H alpha macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major CMEs. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jets that were also caught in He II 304 Angstrom snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T 10(exp 4) - 10(exp 5) K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.

  9. Experimental study of elliptical jet from sub to supercritical conditions

    SciTech Connect

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2014-04-15

    The jet mixing at supercritical conditions involves fluid dynamics as well as thermodynamic phenomena. All the jet mixing studies at critical conditions to the present date have focused only on axisymmetric jets. When the liquid jet is injected into supercritical environment, the thermodynamic transition could be well understood by considering one of the important fluid properties such as surface tension since it decides the existence of distinct boundary between the liquid and gaseous phase. It is well known that an elliptical liquid jet undergoes axis-switching phenomena under atmospheric conditions due to the presence of surface tension. The experimental investigations were carried out with low speed elliptical jet under supercritical condition. Investigation of the binary component system with fluoroketone jet and N{sub 2} gas as environment shows that the surface tension force dominates for a large downstream distance, indicating delayed thermodynamic transition. The increase in pressure to critical state at supercritical temperature is found to expedite the thermodynamic transition. The ligament like structures has been observed rather than droplets for supercritical pressures. However, for the single component system with fluoroketone jet and fluoroketone environment shows that the jet disintegrates into droplets as it is subjected to the chamber conditions even for the subcritical pressures and no axis switching phenomenon is observed. For a single component system, as the pressure is increased to critical state, the liquid jet exhibits gas-gas like mixing behavior and that too without exhibiting axis-switching behavior.

  10. The effect of turbulence on the stability of liquid jets and the resulting droplet size distributions. Fourth quarterly technical report, October 1, 1993--December 31, 1993

    SciTech Connect

    Mansour, A.; Chigier, N.

    1993-12-31

    In this progress report the authors report on progress in making experimental measurements to describe the rheological properties of non-Newtonian fluids. Non-Newtonian liquids exhibit a non linear relationship between the shear stress and the shear rate. A typical time-dependent rheological phenomenon is thixotropy. Thixotropic fluids show a limited decrease in the shear viscosity of the fluid with time under a suddenly applied constant stress. Thixotropic fluids also show a hysteresis loop and a decaying stress on the shear stress-shear rate plot. Here the authors are using a power law model to describe the behavior of such non-Newtonian liquids.

  11. Liquid breakup studies for singlet oxygen generators

    NASA Astrophysics Data System (ADS)

    Schall, Wolfgang O.; Kraft, Daniela

    1996-02-01

    The instability of the liquid jets in a jet singlet oxygen generator for oxygen-iodine lasers may limit the operational conditions and the scalability of such generators. Therefore the type of instability and the breakup behavior of jets is investigated experimentally for varying operational conditions. Jets of basic hydrogen peroxide are simulated by the use of glycerin solutions with different viscosities. Two experimental setups with optical observation of the jet development are described. Transition from laminar to turbulent jets, the associated breakup modes and the beginning of jet dissolution by surface spraying are observed. For generator relevant jet diameters intact jet lengths were found to be limited to approx. 25 cm. Jets with driving pressure of more than 3 bar exhibited strong spraying from their surface. The jet diameter shrinks with increasing driving pressure.

  12. Fluid Mechanics of Liquid-Liquid Systems.

    NASA Astrophysics Data System (ADS)

    Richards, John Reed

    The detailed hydrodynamics of selected liquid -liquid flow systems are investigated to provide a firm foundation for the rational design of separation processes. The implementation of this objective centers on the development of a robust code to simulate liquid-liquid flows. We have applied this code to the realistic simulation of aspects of the complex fluid mechanical behavior, and developed quantitative insight into the underlying processes involved. The Volume of Fluid (VOF) method is combined with the Continuous Surface Force (CSF) algorithm to provide a numerically stable code capable of solving high Reynolds numbers free surface flows. One of the developments during the testing was an efficient method for solving the Young-Laplace equation describing the shape of the meniscus in a vertical cylinder for a constrained liquid volume. The steady-state region near the nozzle for the laminar flow of a Newtonian liquid jet injected vertically into another immiscible Newtonian liquid is investigated for various Reynolds numbers by solving the axisymmetric transient equations of motion and continuity. The analysis takes into account pressure, viscous, inertial, gravitational, and surface tension forces, and comparison with previous experimental measurements shows good agreement. Comparisons of the present numerical method with the numerical results of previous boundary-layer methods help establish their range of validity. A new approximate equation for the shape of the interface of the steady jet, based on an overall momentum balance, is also developed. The full transient from liquid-liquid jet startup to breakup into drops is also simulated numerically. In comparison with experiment, the results of the present numerical method show a greater sensitivity of the jet length to the Reynolds number than the best predictions of previous linear stability analyses. The formation of drops is investigated at low to high Reynolds numbers before and after jet formation. The numerical simulations are satisfactorily compared with n-heptane/water experiments and previous simplified analyses based on drop formation before and after jetting. Although the program and numerical techniques developed in this dissertation have been used mainly to solve problems involving liquid-liquid jets and drops, many features of more complex and general liquid-liquid contacting systems are explored in the process.

  13. Liquid metal fuel combustion mechanics

    NASA Astrophysics Data System (ADS)

    Duvvuri, Tirumalesa

    1990-07-01

    The modeling of the droplet formation at the gas/liquid boundary interface of a gaseous jet injected into a liquid metal bath and the turbulent mixing of the resultant two-phase (gas/liquid) mixture is presented as a preliminary to the analysis of the liquid metal fuel combustion problem. The model is used to predict velocity and liquid droplet fraction distributions across the mixing zone and along the centerline of the jet. These results show that the distribution of the liquid fuel droplets peaks away from the region of maximum oxidizer concentrations.

  14. A multi-function droplet imaging and velocimetry system for spray jets

    NASA Astrophysics Data System (ADS)

    Chen, Tzong H.; Roe, Larry A.; Nejad, Abdi S.

    1993-01-01

    The development of a multifunction instrumentation system capable of scalar imaging and velocity-vector mapping of the dense liquid jet in a crossflow is presented. The system needs solely a single laser that is double pulsed to produce droplet-displacement images. Application of this imaging system to the study of liquid jets transversely injected into a crossflow has provided a greatly enhanced formulation that takes into account multizone jet behavior in describing jet penetration into the crossflow.

  15. Influence of heat transfer on the aerodynamic performance of a plunging and pitching NACA0012 airfoil at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Hinz, Denis F.; Alighanbari, Hekmat; Breitsamter, Christian

    2013-02-01

    The unsteady low Reynolds number aerodynamics phenomena around flapping wings are addressed in several investigations. Elsewhere, airfoils at higher Mach numbers and Reynolds numbers have been treated quite comprehensively in the literature. It is duly noted that the influence of heat transfer phenomena on the aerodynamic performance of flapping wings configurations is not well studied. The objective of the present study is to investigate the effect of heat transfer upon the aerodynamic performance of a pitching and plunging NACA0012 airfoil in the low Reynolds number flow regime with particular emphasis upon the airfoil's lift and drag coefficients. The compressible Navier-Stokes equations are solved using a finite volume method. To consider the variation of fluid properties with temperature, the values of dynamic viscosity and thermal diffusivity are evaluated with Sutherland's formula and the Eucken model, respectively. Instantaneous and mean lift and drag coefficients are calculated for several temperature differences between the airfoil surface and freestream within the range 0-100 K. Simulations are performed for a prescribed airfoil motion schedule and flow parameters. It is learnt that the aerodynamic performance in terms of the lift CL and drag CD behavior is strongly dependent upon the heat transfer rate from the airfoil to the flow field. In the plunging case, the mean value of CD tends to increase, whereas the amplitude of CL tends to decrease with increasing temperature difference. In the pitching case, on the other hand, the mean value and the amplitude of both CD and CL decrease. A spectral analysis of CD and CL in the pitching case shows that the amplitudes of both CD and CL decrease with increasing surface temperature, whereas the harmonic frequencies are not affected.

  16. Fluid mechanic investigations for O2(1Delta) jet generators

    NASA Astrophysics Data System (ADS)

    Franck, Charmaine C.; Schall, Wolfgang O.

    1995-03-01

    The general scalability of jet generators may be limited due to the inevitable breakup of the thin liquid jets. The fluid mechanic theory of liquid jets is reviewed. An experiment was set up to simulate jets of basic hydrogen peroxide and measure their velocity and breakup lengths as a function of the orifice diameter and length, and of the viscosity of the liquid. The experimental setup and its future extensions are described. The jets were run with atmospheric pressure into a chamber at low pressure. The results are compared to predictions from the simple theory and extrapolated to driving pressures of 10 bar.

  17. Plunging Ranulas Revisited: A CT Study with Emphasis on a Defect of the Mylohyoid Muscle as the Primary Route of Lesion Propagation

    PubMed Central

    Lee, Ji Young; Lee, Hee Young; Jeong, Han Sin; Kim, Yi-Kyung; Cha, Jihoon; Kim, Sung Tae

    2016-01-01

    Objective The purpose of this study was to clarify the pathogenesis of plunging ranulas in regard of the pathway of lesion propagation using CT scans. Materials and Methods We retrospectively reviewed CT scans of 41 patients with plunging ranula. We divided plunging ranulas into two types: type 1 was defined as those directly passing through a defect of the mylohyoid muscle with the presence (type 1A) or absence (type 1B) of the tail sign and type 2 as those through the traditional posterior route along the free edge of the mylohyoid muscle. Images were also analyzed for the extent of the lesion in respect to the spaces involved. As for type 1 lesions, we recorded the location of the defect of the mylohyoid muscle and the position of the sublingual gland in relation to the defect. Results CT scans demonstrated type 1 lesion in 36 (88%), including type 1A in 14 and type 1B in 22, and type 2 lesion in 5 (12%). Irrespective of the type, the submandibular space was seen to be involved in all cases either alone or in combination with one or more adjacent spaces. Of the 36 patients with type 1 lesions, the anterior one-third was the most common location of the defect of the mylohyoid muscle, seen in 22 patients. The sublingual gland partially herniated in 30 patients. Conclusion Our results suggest that the majority of plunging ranulas take an anterior shortcut through a defect of the mylohyoid muscle. PMID:26957912

  18. Spatiotemporal instability of a confined capillary jet.

    PubMed

    Herrada, M A; Gañán-Calvo, A M; Guillot, P

    2008-10-01

    Recent experimental studies on the instability of capillary jets have revealed the suitability of a linear spatiotemporal instability analysis to ascertain the parametrical conditions for specific flow regimes such as steady jetting or dripping. In this work, an extensive analytical, numerical, and experimental description of confined capillary jets is provided, leading to an integrated picture both in terms of data and interpretation. We propose an extended, accurate analytic model in the low Reynolds number limit, and introduce a numerical scheme to predict the system response when the liquid inertia is not negligible. Theoretical predictions show remarkable accuracy when compared with the extensive experimental mapping. PMID:18999531

  19. Spray formation processes of impinging jet injectors

    NASA Technical Reports Server (NTRS)

    Anderson, W. E.; Ryan, H. M.; Pal, S.; Santoro, R. J.

    1993-01-01

    A study examining impinging liquid jets has been underway to determine physical mechanisms responsible for combustion instabilities in liquid bi-propellant rocket engines. Primary atomization has been identified as an important process. Measurements of atomization length, wave structure, and drop size and velocity distribution were made under various ambient conditions. Test parameters included geometric effects and flow effects. It was observed that pre-impingement jet conditions, specifically whether they were laminar or turbulent, had the major effect on primary atomization. Comparison of the measurements with results from a two dimensional linear aerodynamic stability model of a thinning, viscous sheet were made. Measured turbulent impinging jet characteristics were contrary to model predictions; the structure of waves generated near the point of jet impingement were dependent primarily on jet diameter and independent of jet velocity. It has been postulated that these impact waves are related to pressure and momentum fluctuations near the impingement region and control the eventual disintegration of the liquid sheet into ligaments. Examination of the temporal characteristics of primary atomization (ligament shedding frequency) strongly suggests that the periodic nature of primary atomization is a key process in combustion instability.

  20. Rich phenomenology encountered when two jets collide in microgravity

    NASA Astrophysics Data System (ADS)

    Suol, Francesc; Gonzalez-Cinca, Ricard

    The collision between two impinging liquid jets has been experimentally studied in the low gravity environment provided by the ZARM drop tower. The effects of impact angle and liquid flow rate on the collision between like-doublet jets have been considered. Tests were carried out with distilled water injected through nozzles with an internal diameter of 0.7 mm into a test cell. Impact angle varied between 10() and 180() (frontal collision), while the liquid flow rate ranged between 20 ml/min and 80 ml/min for each nozzle. Such a large parameter range allowed us to observe different phenomena resulting from the jets collision: oscillating droplets attached to the nozzles, a non-uniform spatial distribution of bouncing droplets, coalescing droplets generating a single central droplet, coalescing jets, bouncing jets, liquid chains and liquid sheets. A map of the different patterns observed has been obtained. We present results on the structure of the jets after collision, the breakup length and the size of the generated droplet. The resulting structure of impinging jets highly depends on the Reynolds and Weber numbers, and the proper alignment of the colliding jets.

  1. Inclusive Jets in PHP

    NASA Astrophysics Data System (ADS)

    Roloff, P.

    Differential inclusive-jet cross sections have been measured in photoproduction for boson virtualities Q^2 < 1 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 300 pb^-1. Jets were identified in the laboratory frame using the k_T, anti-k_T or SIScone jet algorithms. Cross sections are presented as functions of the jet pseudorapidity, eta(jet), and the jet transverse energy, E_T(jet). Next-to-leading-order QCD calculations give a good description of the measurements, except for jets with low E_T(jet) and high eta(jet). The cross sections have the potential to improve the determination of the PDFs in future QCD fits. Values of alpha_s(M_Z) have been extracted from the measurements based on different jet algorithms. In addition, the energy-scale dependence of the strong coupling was determined.

  2. Analysis of maximum pressure attainable by water jet impact

    SciTech Connect

    Reitter, T.A.; Kang, S.W.

    1993-05-01

    The maximum pressure attainable in an impacting jet has been addressed by researchers for jet-cutting technology, notably in rock-drilling operations and the minimization of turbine-blade erosion. The authors have analyzed the maximum pressure attainable in a liquid jet when it impinges on a rigid surface. The CALE hydrodynamics code has been used for this purpose. The calculated maximum pressure for a given jet velocity is higher than the so-called water-hammer value, {rho}{sub 0}C{sub 0}V where the term {rho} denotes the liquid density, C the sound speed, V the flow velocity, and the subscript o the undisturbed (upstream) region in the jet. However, the calculated results agree well with experimental data and with a well-known generalized water hammer pressure expression for high (as well as low) jet velocities.

  3. Analysis of maximum pressure attainable by water jet impact

    SciTech Connect

    Reitter, T.A.; Kang, S.W.

    1993-05-01

    The maximum pressure attainable in an impacting jet has been addressed by researchers for jet-cutting technology, notably in rock-drilling operations and the minimization of turbine-blade erosion. The authors have analyzed the maximum pressure attainable in a liquid jet when it impinges on a rigid surface. The CALE hydrodynamics code has been used for this purpose. The calculated maximum pressure for a given jet velocity is higher than the so-called water-hammer value, [rho][sub 0]C[sub 0]V where the term [rho] denotes the liquid density, C the sound speed, V the flow velocity, and the subscript o the undisturbed (upstream) region in the jet. However, the calculated results agree well with experimental data and with a well-known generalized water hammer pressure expression for high (as well as low) jet velocities.

  4. Centrifugal device separates liquid from gas

    NASA Technical Reports Server (NTRS)

    Handlewich, R. M.; Stroup, K. E.

    1965-01-01

    Liquid-to-gas ratio is reduced from maximum efficiency of jet engine fuel by a centrifugal separator. The amount of liquid removed from the fuel is controlled by the separator-screen mesh size and its rotational speed.

  5. Instability of capillary jets with thermocapillarity

    NASA Technical Reports Server (NTRS)

    Xu, J.-J.; Davis, S. H.

    1985-01-01

    Long axisymmetric liquid zones are subject to axial temperature gradients which induce steady viscous flows driven by thermocapillarity. The approximately parallel flow in a cylindrical zone is examined for linearized instabilities. Capillary, surface-wave and thermal modes are found. Capillary breakup can be retarded or even suppressed for small Prandtl number and large Biot number B, which measures heat transfer from the liquid to the surrounding atmosphere. In the limiting case B approaches infinity the zone becomes an isothermal jet subject to axial 'wind stress' on its interface. It is then possible to suppress capillary breakup entirely so that one can maintain long coherent jets.

  6. A new flow focusing technique to produce very thin jets

    NASA Astrophysics Data System (ADS)

    Acero, A. J.; Rebollo-Muoz, N.; Montanero, J. M.; Gan-Calvo, A. M.; Vega, E. J.

    2013-06-01

    A new technique is proposed in this paper to produce jets, droplets, and emulsions with sizes ranging from tens of microns down to the submicrometer scale. Liquid is injected at a constant flow rate through a hypodermic needle to form a film over the needle's outer surface. This film flows toward the needle tip until a liquid ligament is steadily ejected. Both the film motion and the liquid ejection are driven by the viscous and pressure forces exerted by a coflowing fluid stream. If this stream is a high-speed gas current, the outcome is a capillary jet which breaks up into droplets due to the Rayleigh instability. Micrometer emulsions are also produced by this instability mechanism when the injected liquid is focused by a viscous liquid stream. The minimum flow rates reached with the proposed technique are two orders of magnitude lower than those of the standard flow focusing configuration. This sharp reduction of the minimum flow rate allows one to form steady jets with radii down to the submicrometer scale. The stability of this new configuration is analyzed experimentally for both gas-liquid and liquid-liquid systems. In most of the cases, the loss of stability must be attributed to the liquid source because the critical Weber (capillary) number for the gas-liquid (liquid-liquid) case was significantly greater than the value corresponding to the convective/absolute instability transition in the jet.

  7. Jet energy scale determination in the D0 experiment

    NASA Astrophysics Data System (ADS)

    Abazov, V. M.; Abbott, B.; Acharya, B. S.; Adams, M.; Adams, T.; Agnew, J. P.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Askew, A.; Atkins, S.; Augsten, K.; Avila, C.; Badaud, F.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, S.; Barberis, E.; Baringer, P.; Bartlett, J. F.; Bassler, U.; Bazterra, V.; Bean, A.; Begalli, M.; Bellantoni, L.; Beri, S. B.; Bernardi, G.; Bernhard, R.; Bertram, I.; Besanon, M.; Beuselinck, R.; Bhat, P. C.; Bhatia, S.; Bhatnagar, V.; Blazey, G.; Blessing, S.; Bloom, K.; Boehnlein, A.; Boline, D.; Boos, E. E.; Borissov, G.; Borysova, M.; Brandt, A.; Brandt, O.; Brock, R.; Bross, A.; Brown, D.; Bu, X. B.; Buehler, M.; Buescher, V.; Bunichev, V.; Burdin, S.; Buszello, C. P.; Camacho-Prez, E.; Casey, B. C. K.; Castilla-Valdez, H.; Caughron, S.; Chakrabarti, S.; Chan, K. M.; Chandra, A.; Chapon, E.; Chen, G.; Cho, S. W.; Choi, S.; Choudhary, B.; Cihangir, S.; Claes, D.; Clutter, J.; Cooke, M.; Cooper, W. E.; Corcoran, M.; Couderc, F.; Cousinou, M.-C.; Cutts, D.; Das, A.; Davies, G.; de Jong, S. J.; De La Cruz-Burelo, E.; Dliot, F.; Demina, R.; Denisov, D.; Denisov, S. P.; Desai, S.; Deterre, C.; DeVaughan, K.; Diehl, H. T.; Diesburg, M.; Ding, P. F.; Dominguez, A.; Dubey, A.; Dudko, L. V.; Duperrin, A.; Dutt, S.; Eads, M.; Edmunds, D.; Ellison, J.; Elvira, V. D.; Enari, Y.; Evans, H.; Evdokimov, V. N.; Feng, L.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fortner, M.; Fox, H.; Fuess, S.; Garbincius, P. H.; Garcia-Bellido, A.; Garca-Gonzlez, J. A.; Gavrilov, V.; Geng, W.; Gerber, C. E.; Gershtein, Y.; Ginther, G.; Golovanov, G.; Grannis, P. D.; Greder, S.; Greenlee, H.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grohsjean, A.; Grnendahl, S.; Grnewald, M. W.; Guillemin, T.; Gutierrez, G.; Gutierrez, P.; Haley, J.; Han, L.; Harder, K.; Harel, A.; Hauptman, J. M.; Hays, J.; Head, T.; Hebbeker, T.; Hedin, D.; Hegab, H.; Heinson, A. P.; Heintz, U.; Hensel, C.; Heredia-De La Cruz, I.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hoang, T.; Hobbs, J. D.; Hoeneisen, B.; Hogan, J.; Hohlfeld, M.; Holzbauer, J. L.; Howley, I.; Hubacek, Z.; Hynek, V.; Iashvili, I.; Ilchenko, Y.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffr, M.; Jayasinghe, A.; Jeong, M. S.; Jesik, R.; Jiang, P.; Johns, K.; Johnson, E.; Johnson, M.; Jonckheere, A.; Jonsson, P.; Joshi, J.; Jung, A. W.; Juste, A.; Kajfasz, E.; Karmanov, D.; Katsanos, I.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. N.; Kiselevich, I.; Kohli, J. M.; Kozelov, A. V.; Kraus, J.; Kumar, A.; Kupco, A.; Kur?a, T.; Kuzmin, V. A.; Lammers, S.; Lebrun, P.; Lee, H. S.; Lee, S. W.; Lee, W. M.; Lei, X.; Lellouch, J.; Li, D.; Li, H.; Li, L.; Li, Q. Z.; Lim, J. K.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, H.; Liu, Y.; Lobodenko, A.; Lokajicek, M.; Lopes de Sa, R.; Luna-Garcia, R.; Lyon, A. L.; Maciel, A. K. A.; Madar, R.; Magaa-Villalba, R.; Makovec, N.; Malik, S.; Malyshev, V. L.; Mansour, J.; Martnez-Ortega, J.; McCarthy, R.; McGivern, C. L.; Meijer, M. M.; Melnitchouk, A.; Menezes, D.; Mercadante, P. G.; Merkin, M.; Meyer, A.; Meyer, J.; Miconi, F.; Mondal, N. K.; Mulhearn, M.; Nagy, E.; Narain, M.; Nayyar, R.; Neal, H. A.; Negret, J. P.; Neustroev, P.; Nguyen, H. T.; Nunnemann, T.; Orduna, J.; Osman, N.; Osta, J.; Pal, A.; Parashar, N.; Parihar, V.; Park, S. K.; Partridge, R.; Parua, N.; Patwa, A.; Penning, B.; Perfilov, M.; Peters, Y.; Petridis, K.; Petrillo, G.; Ptroff, P.; Pleier, M.-A.; Podstavkov, V. M.; Popov, A. V.; Prewitt, M.; Price, D.; Prokopenko, N.; Ochando, C.; Qian, J.; Quadt, A.; Quinn, B.; Raja, R.; Ratoff, P. N.; Razumov, I.; Ripp-Baudot, I.; Rizatdinova, F.; Rominsky, M.; Ross, A.; Royon, C.; Rubinov, P.; Ruchti, R.; Sajot, G.; Snchez-Hernndez, A.; Sanders, M. P.; Santos, A. S.; Savage, G.; Sawyer, L.; Scanlon, T.; Schamberger, R. D.; Scheglov, Y.; Schellman, H.; Schwanenberger, C.; Schwienhorst, R.; Sekaric, J.; Severini, H.; Shabalina, E.; Shary, V.; Shaw, S.; Shchukin, A. A.; Simak, V.; Skubic, P.; Slattery, P.; Smirnov, D.; Snow, G. R.; Snow, J.; Snyder, S.; Sldner-Rembold, S.; Sonnenschein, L.; Soustruznik, K.; Stark, J.; Stoyanova, D. A.; Strauss, M.; Suter, L.; Svoisky, P.; Titov, M.; Tokmenin, V. V.; Tsai, Y.-T.; Tsybychev, D.; Tuchming, B.; Tully, C.; Uvarov, L.; Uvarov, S.; Uzunyan, S.; Van Kooten, R.; van Leeuwen, W. M.; Varelas, N.; Varnes, E. W.; Vasilyev, I. A.; Verkheev, A. Y.; Vertogradov, L. S.; Verzocchi, M.; Vesterinen, M.; Vilanova, D.; Vokac, P.; Wahl, H. D.; Wang, M. H. L. S.; Warchol, J.; Watts, G.; Wayne, M.; Weichert, J.; Welty-Rieger, L.; Williams, M. R. J.; Wilson, G. W.; Wobisch, M.; Wood, D. R.; Wyatt, T. R.; Xie, Y.; Yamada, R.; Yang, S.; Yasuda, T.; Yatsunenko, Y. A.; Ye, W.; Ye, Z.; Yin, H.; Yip, K.

    2014-11-01

    The calibration of jet energy measured in the D0 detector is presented, based on p p bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with ? + jet, Z + jet and dijet events, with jet transverse momentum pT > 6 GeV and pseudorapidity range | ? | < 3.6. The corrections are measured separately for data and simulation, achieving a precision of 1.4-1.8% for jets in the central part of the calorimeter and up to 3.5% for the jets with pseudorapidity | ? | = 3.0. Specific corrections are extracted to enhance the description of jet energy in simulation and in particular of the effects due to the flavor of the parton originating the jet, correcting biases up to 3-4% in jets with low pT originating from gluons and up to 6-8% in jets from b quarks.

  8. Visualization of supersonic diesel fuel jets using a shadowgraph technique

    NASA Astrophysics Data System (ADS)

    Pianthong, Kulachate; Behnia, Masud; Milton, Brian E.

    2001-04-01

    High-speed liquid jets have been widely used to cut or penetrate material. It has been recently conjectured that the characteristics of high-speed fuel jets may also be of benefit to engines requiring direct fuel injection into the combustion chamber. Important factors are combustion efficiency and emission control enhancement for better atomization. Fundamental studies of very high velocity liquid jets are therefore very important. The characteristics and behavior of supersonic liquid jets have been studied with the aid of a shadowgraph technique. The high-speed liquid jet (in the supersonic range) is generated by the use of a vertical, single stage powder gun. The performance of the launcher and its relation to the jet exit velocity, with a range of nozzle shapes, has been examined. This paper presents the visual evidence of supersonic diesel fuel jets (velocity around 2000 m/s) investigated by the shadowgraph method. An Argon jet has been used as a light source. With a rise time of 0.07 microseconds, light duration of 0.2 microseconds and the use of high speed Polaroid film, the shadowgraph method can effectively capture the hypersonic diesel fuel jet and its strong leading edge shock waves. This provides a clearer picture of each stage of the generation of hypersonic diesel fuel jets and makes the study of supersonic diesel fuel jet characteristics and the potential for auto-ignition possible. Also, in the experiment, a pressure relief section has been used to minimize the compressed air or blast wave ahead of the projectile. However, the benefit of using a pressure relief section in the design is not clearly known. To investigate this effect, additional experiments have been performed with the use of the shadowgraph method, showing the projectile leaving and traveling inside the nozzle at a velocity around 1100 m/s.

  9. Simulations of dynamics of plunge and pitch of a three-dimensional flexible wing in a low Reynolds number flow

    NASA Astrophysics Data System (ADS)

    Qi, Dewei; Liu, Yingming; Shyy, Wei; Aono, Hikaru

    2010-09-01

    The lattice Boltzmann flexible particle method (LBFPM) is used to simulate fluid-structure interaction and motion of a flexible wing in a three-dimensional space. In the method, a beam with rectangular cross section has been discretized into a chain of rigid segments. The segments are connected through ball and socket joints at their ends and may be bent and twisted. Deformation of flexible structure is treated with a linear elasticity model through bending and twisting. It is demonstrated that the flexible particle method (FPM) can approximate the nonlinear Euler-Bernoulli beam equation without resorting to a nonlinear elasticity model. Simulations of plunge and pitch of flexible wing at Reynolds number Re=136 are conducted in hovering condition by using the LBFPM. It is found that both lift and drag forces increase first, then decrease dramatically as the bending rigidity in spanwise direction decreases and that the lift and drag forces are sensitive to rigidity in a certain range. It is shown that the downwash flows induced by wing tip and trailing vortices in wake area are larger for a flexible wing than for a rigid wing, lead to a smaller effective angle of attack, and result in a larger lift force.

  10. Assessment of external heat transfer coefficient during oocyte vitrification in liquid and slush nitrogen using numerical simulations to determine cooling rates.

    PubMed

    Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J

    2012-01-01

    In oocyte vitrification, plunging directly into liquid nitrogen favor film boiling and strong nitrogen vaporization. A survey of literature values of heat transfer coefficients (h) for film boiling of small metal objects with different geometries plunged in liquid nitrogen revealed values between 125 to 1000 W per per square m per K. These h values were used in a numerical simulation of cooling rates of two oocyte vitrification devices (open-pulled straw and Cryotop), plunged in liquid and slush nitrogen conditions. Heat conduction equation with convective boundary condition was considered a linear mathematical problem and was solved using the finite element method applying the variational formulation. COMSOL Multiphysics was used to simulate the cooling process of the systems. Predicted cooling rates for OPS and Cryotop when cooled at -196 degree C (liquid nitrogen) or -207 degree C (average for slush nitrogen) for heat transfer coefficients estimated to be representative of film boiling, indicated lowering the cooling temperature produces only a maximum 10 percent increase in cooling rates; confirming the main benefit of plunging in slush over liquid nitrogen does not arise from their temperature difference. Numerical simulations also demonstrated that a hypothetical four-fold increase in the cooling rate of vitrification devices when plunging in slush nitrogen would be explained by an increase in heat transfer coefficient. This improvement in heat transfer (i.e., high cooling rates) in slush nitrogen is attributed to less or null film boiling when a sample is placed in slush (mixture of liquid and solid nitrogen) because it first melts the solid nitrogen before causing the liquid to boil and form a film. PMID:22434120

  11. Jet fuels from synthetic crudes

    NASA Technical Reports Server (NTRS)

    Antoine, A. C.; Gallagher, J. P.

    1977-01-01

    An investigation was conducted to determine the technical problems in the conversion of a significant portion of a barrel of either a shale oil or a coal synthetic crude oil into a suitable aviation turbine fuel. Three syncrudes were used, one from shale and two from coal, chosen as representative of typical crudes from future commercial production. The material was used to produce jet fuels of varying specifications by distillation, hydrotreating, and hydrocracking. Attention is given to process requirements, hydrotreating process conditions, the methods used to analyze the final products, the conditions for shale oil processing, and the coal liquid processing conditions. The results of the investigation show that jet fuels of defined specifications can be made from oil shale and coal syncrudes using readily available commercial processes.

  12. Project HyBuJET

    NASA Technical Reports Server (NTRS)

    Ramsay, Tom; Collet, Bill; Igar, Karyn; Kendall, Dewayne; Miklosovic, Dave; Reuss, Robyn; Ringer, Mark; Scheidt, Tony

    1990-01-01

    A conceptual Hypersonic Business Jet (HyBuJet) was examined. The main areas of concentration include: aerodynamics, propulsion, stability and control, mission profile, and atmospheric heating. In order to optimize for cruise conditions, a waverider configuration was chosen for the high lift drag ratio and low wave drag. The leading edge and lower surface of a waverider was mapped out from a known flow field and optimized for cruising at Mach 6 and at high altitudes. The shockwave generated by a waverider remains attached along the entire leading edge, allowing for a larger compression along the lower surface. Three turbofan ramjets were chosen as the propulsion of the aircraft due to the combination of good subsonic performance along with high speed propulsive capabilities. A combination of liquid silicon convective cooling for the leading edges with a highly radiative outer skin material was chosen to reduce the atmospheric heating to acceptable level.

  13. Control of jet noise

    NASA Technical Reports Server (NTRS)

    Schreck, Stefan

    1993-01-01

    This reports describes experiments conducted at the High-Speed Jet Facility at the University of Southern California on supersonic jets. The goal of the study was to develop methods for controlling the noise emitted from supersonic jets by passive and/or active means. Work by Seiner et al (1991) indicates that eddy Mach wave radiation is the dominant noise source in a heated high speed jet. Eddy Mach radiation is caused by turbulent eddies traveling at supersonic speed in the shear layer of the jet. The convection velocity of the eddies decays with increasing distance from the nozzle exit due to the mixing of the jet stream with the ambient fluid. Once the convection speed reaches subsonic velocities, eddy Mach wave radiation ceases. To control noise, a rapid decay of the convection velocity is desired. This may be accomplished by enhanced mixing in the jet. In this study, small aspect ratio rectangular jet nozzles were tested. A flapping mode was noticed in the jets. By amplifying screech components of the jets and destabilizing the jet columns with a collar device, the flapping mode was excited. The result was a rapid decay of the jet velocity. A reduction in eddy Mach radiation in rectangular supersonic jets may be achieved with this device.

  14. Universal scaling law for jets of collapsing bubbles.

    PubMed

    Obreschkow, D; Tinguely, M; Dorsaz, N; Kobel, P; de Bosset, A; Farhat, M

    2011-11-11

    Cavitation bubbles collapsing and rebounding in a pressure gradient ?p form a "microjet" enveloped by a "vapor jet." This Letter presents unprecedented observations of the vapor jets formed in a uniform gravity-induced ?p, modulated aboard parabolic flights. The data uncover that the normalized jet volume is independent of the liquid density and viscosity and proportional to ? ? |?p|R(0)/?p, where R(0) the maximal bubble radius and ?p is the driving pressure. A derivation inspired by "Kelvin-Blake" considerations confirms this law and reveals its negligible dependence of surface tension. We further conjecture that the jet only pierces the bubble boundary if ? ? 4 10(-4). PMID:22181734

  15. A determination of the external forces required to move the benchmark active controls testing model in pure plunge and pure pitch

    NASA Technical Reports Server (NTRS)

    Dcruz, Jonathan

    1993-01-01

    In view of the strong need for a well-documented set of experimental data which is suitable for the validation and/or calibration of modern Computational Fluid Dynamics codes, the Benchmark Models Program was initiated by the Structural Dynamics Division of the NASA Langley Research Center. One of the models in the program, the Benchmark Active Controls Testing Model, consists of a rigid wing of rectangular planform with a NACA 0012 profile and three control surfaces (a trailing-edge control surface, a lower-surface spoiler, and an upper-surface spoiler). The model is affixed to a flexible mount system which allows only plunging and/or pitching motion. An approximate analytical determination of the forces required to move this model, with its control surfaces fixed, in pure plunge and pure pitch at a number of test conditions is included. This provides a good indication of the type of actuator system required to generate the aerodynamic data resulting from pure plunging and pure pitching motion, in which much interest was expressed. The analysis makes use of previously obtained numerical results.

  16. Suppressing the Folding of Flowing Viscous Jets Using an Electric Field

    NASA Astrophysics Data System (ADS)

    Kong, Tiantian; Liu, Zhou; Wang, Liqiu; Shum, Ho Cheung

    2015-03-01

    In this work, we study the folding and unfolding of flowing viscous jets by imposing an electric field. We demonstrate that a folded viscous jet can be induced to unfold through jet widening in a sufficiently strong electric field. The folded jets unfold above a critical slenderness, which increases as the jet capillary number increases. Our systematic elucidation of the mechanisms behind the controlled folding has important implications on processes such as nozzle designs for industrial applications that rely on the manipulation of high-speed viscous jets, including liquid dispensing, printing, and food processing.

  17. Continuous-wave laser generated jets for needle free applications.

    PubMed

    Berrospe-Rodriguez, Carla; Visser, Claas Willem; Schlautmann, Stefan; Ramos-Garcia, Ruben; Fernandez Rivas, David

    2016-01-01

    We designed and built a microfluidic device for the generation of liquid jets produced by thermocavitation. A continuous wave (CW) laser was focused inside a micro-chamber filled with a light-absorbing solution to create a rapidly expanding vapor bubble. The chamber is connected to a micro-channel which focuses and ejects the liquid jet through the exit. The bubble growth and the jet velocity were measured as a function of the devices geometry (channel diameter D and chamber width A). The fastest jets were those for relatively large chamber size with respect to the channel diameter. Elongated and focused jets up to 29?m/s for a channel diameter of [Formula: see text] and chamber size of [Formula: see text] were obtained. The proposed CW laser-based device is potentially a compact option for a practical and commercially feasible needle-free injector. PMID:26858816

  18. NASA Jet Noise Research

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda

    2012-01-01

    The presentation highlights jet-noise research conducted in the Subsonic Fixed Wing, Supersonics, and Environmentally Responsible Aviation Projects in the Fundamental Aeronautics Program at NASA. The research efforts discussed include NASA's updated Aircraft NOise Prediction Program (ANOPP2), acoustic-analogy-based prediction tools, jet-surface-interaction studies, plasma-actuator investigations, N+2 Supersonics Validation studies, rectangular-jet experiments, twin-jet experiments, and Hybrid Wind Body (HWB) activities.

  19. Prewhirl Jet Model

    NASA Technical Reports Server (NTRS)

    Meng, S. Y.; Jensen, M.; Jackson, E. D.

    1985-01-01

    Simple accurate model of centrifugal or rocket engine pumps provides information necessary to design inducer backflow deflector, backflow eliminator and prewhirl jet in jet mixing zones. Jet design based on this model shows improvement in inducer suction performance and reduced cavitation damage.

  20. CALCULATIONS FOR A MERCURY JET TARGET IN A SOLENOID MAGNET CAPTURE SYSTEM.

    SciTech Connect

    GALLARDO, J.; KAHN, S.; PALMER, R.B.; THIEBERGER, P.; WEGGEL, R.J.; MCDONALD, K.

    2001-06-18

    A mercury jet is being considered as the production target for a muon storage ring facility to produce an intense neutrino beam. A 20 T solenoid magnet that captures pions for muon production surrounds the mercury target. As the liquid metal jet enters or exits the field eddy currents are induced. We calculate the effects that a liquid metal jet experiences in entering and exiting the magnetic field for the magnetic configuration considered in the Neutrino Factory Feasibility Study II.

  1. Experimental and theoretical study of fluid-structure interactions in plunging hydrofoils and gravity-driven falling plates

    NASA Astrophysics Data System (ADS)

    Tian, Ruijun

    Two typical unsteady fluid-structure interaction problems have been investigated in the present study. One of them was about actively plunged flexible hydrofoil; the other was about gravity-driven falling plates in water. Real-time velocity field and dynamic response on the moving objects were measured to study these unsteady and highly nonlinear problems. For a long time, scientists have believed that bird and insect flight benefits greatly from the flexibility and morphing facility of their wings via flapping motion. A significant advantage flexible wing models have over quasi-steady rigid wing models is a much higher lift generation capability. Both experimental and computational studies have shown that the leading and trailing edge vortexes (LEV and TEV) play a major role in the efficient generation of such unconventionally high lift force. In this study, two NACA0012 miniature hydrofoils, one flexible and the other rigid, were actively plunged at various frequencies in a viscous glycerol-water solution to study the influence of flexibility. Two-dimensional, phase-locked particle image velocimetry (PIV) measurements were conducted to investigate the temporal and spacial development of LEVs and TEVs. Simultaneous measurements of lift and thrust forces were recorded to reveal the relationship between hydrodynamic force and the evolution of the surrounding flow field. Results from the flexible hydrofoil were compared to those from the rigid one in order to quantitatively analyze the effects of flexibility. The second problem focused on fluid-structure interaction of gravity driven falling plates. Falling leaves and paper cards in air has drawn plenty of research interest in the past decades to investigate the interaction between the fluid flow and the falling object. In this research, time-resolved PIV were employed to experimentally visualize the flow field evolution around the gravity-driven falling plates. The plates were made of different materials with various geometric dimensions, in order to investigate the effects of non-dimensional parameters such as Reynolds number (Re) and dimensionless moment of inertia (I*). Within the range of relative high Reynolds numbers (Re > 500), three types of falling modes were observed: i.e., periodic fluttering, periodic tumbling and marginal chaotic motion. It was found that the nondimensional moment of inertia controlled the falling mode. The flow features through the falling path of the plate were characterized and compared with their corresponding kinematics. Based on theoretical analysis and experimental results, a semi-analytic model was developed to calculate the real-time hydrodynamic force and moment applied on falling plates. With this model, the falling trajectory of 2D plates with arbitrary material/dimension combinations can be predicted. The model yielded a good match for both the dynamic force simulation and trajectory prediction.

  2. Jetting Instability Mechanisms of Particles from Explosive Dispersal

    NASA Astrophysics Data System (ADS)

    Ripley, Robert

    2013-06-01

    The formation of post-detonation ``particle'' jets is widely observed in many problems associated with explosive dispersal of granular materials and liquids. Jets have been shown to form very early, however the mechanism controlling the number of jetting instabilities remains unresolved despite a number of active theories. Recent experiments involving cylindrical charges with a range of central explosive masses for dispersal of dry solid particles and pure liquid are used to formulate macroscopic numerical models for jet formation and growth. The number of jets is strongly related to the dominant perturbation during the shock interaction timescale that controls the initial fracturing of the particle bed and liquid bulk. Perturbations may originate at the interfaces between explosive, shock-dispersed media, and outer edge of the charge due to Richtmyer-Meshkov instabilities. The inner boundary controls the number of major structures, while the outer boundary may introduce additional overlapping structures and microjets that are overtaken by the major structures. In practice, each interface may feature a thin casing material that breaks up, thereby influencing or possibly dominating the instabilities. Hydrocode simulation is used to examine the role of each interface in conjunction with casing effects on the perturbation leading to jet initiation. The subsequent formation of coherent jet structures requires dense multiphase flow of particles and droplets that interact though inelastic collision, agglomeration, and turbulent interaction. Macroscopic multiphase flow simulation shows clustering of particles and merging of smaller instabilities with major jet structures. The methods are further applicable to particles premixed with explosive, which are known to form jets with only an external interface. Late-time dispersal is controlled by particle drag and evaporation of droplets. Numerical results for clustering and jetting evolution are compared with experiments. The work is extended to include interaction of particle and droplet jets with surrounding obstacles and associated combustion phenomena.

  3. Catalytic autothermal reforming of Jet fuel

    NASA Astrophysics Data System (ADS)

    Lenz, Bettina; Aicher, Thomas

    Aircraft manufacturers have to reduce the emissions and the specific fuel consumption of their systems. Fuel cell use in a 'more electric aircraft' can be one possibility. To keep the technology simple only one fuel (Jet A, Jet A-1) shall be used on board the aircraft. Therefore, the catalytic reforming of Jet A-1 fuel was examined in this paper, although the use of fossil fuels causes the production of greenhouse effect promoting gases like carbon dioxide CO 2. The autothermal reforming of desulphurised kerosene is examined with a 15 kW (based on the lower heating value of Jet fuel) test rig. The experiments are performed at steam to carbon ratios of S/C = 1.5-2.5 and air to fuel ratios of ? = 0.24-0.32, respectively. The composition of the product gas, the volumetric flow rate of the product gas at standard conditions and the temperatures in the catalyst are determined as a function of the operating variables. The gas hourly space velocity (GHSV) is varied between 50,000 and 300,000 h -1. The influence of sulphur containing feed streams (real Jet fuel) on reforming behaviour is investigated as well as the influence of the hydrogen concentration on the hydrodesulphurisation process. Another simple way of desulphurisation is the adsorption of liquid sulphur containing hydrocarbons, the influence of the variation of the liquid hourly space velocity (LHSV) is measured at a temperature of 150 C.

  4. Jets at CDF

    SciTech Connect

    Gallinaro, Michele; /Rockefeller U.

    2006-08-01

    Recent jet results in p{bar p} collisions at {radical}s = 1.96 TeV from the CDF experiment at the Tevatron are presented. The jet inclusive cross section is compared to next-to-leading order QCD prediction in different rapidity regions. The b-jet inclusive cross section is measured exploiting the long lifetime and large mass of B-hadrons. Jet shapes, W+jets and W/Z+photon cross sections are also measured and compared to expectations from QCD production.

  5. Two-fluid jets and wakes

    NASA Astrophysics Data System (ADS)

    Herczynski, Andrzej; Weidman, Patrick D.; Burde, Georgy I.

    2004-04-01

    Similarity solutions for laminar two-fluid jets and wakes are derived in the boundary-layer approximation. Planar and axisymmetric fan jets as well as classical and momentumless planar wakes are considered. The interface between the immiscible fluids is stabilized by the action of gravity, with the heavier fluid, taken to be a liquid, placed beneath the lighter fluid. Velocity profiles for the jets and the classical wake depend intimately, but differently, on the parameter ?=?1?1/?2?2, where ?i and ?i are, respectively, the density and absolute viscosity of the fluid in the upper (i=1) and lower (i=2) fluid domains, while the momentumless wake profile depends on the parameter ?=?1?23/?2?13. Generally, all interfaces deflect from horizontal except the fan jet. However, while the interface for the classical planar two-fluid wake is never flat, the interfaces for the planar jet and the momentumless wake become flat in the particular case ?1=?2. Velocity profiles illustrating the strongly asymmetrical jet and wake profiles that arise in air-over-water, oil-over-water, and air-over-oil flows are presented.

  6. High speed liquid impact onto wetted solid surfaces

    SciTech Connect

    Shi, H.H.; Field, J.E.; Pickles, C.S.J. . Dept. of Physics)

    1994-06-01

    The mechanics of impact by a high-speed liquid jet onto a solid surface covered by a liquid layer is described. After the liquid jet contacts the liquid layer, a shock wave is generated, which moves toward the solid surface. The shock wave is followed by the liquid jet penetrating through the layer. The influence of the liquid layer on the side jetting and stress waves is studied. Damage sites on soda-lime glass, PMMA (polymethylmethacrylate) and aluminium show the role of shear failure and cracking and provide evidence for analyzing the impact pressure on the wetted solids and the spatial pressure distribution. The liquid layer reduces the high edge impact pressures, which occur on dry targets. On wetted targets, the pressure is distributed more uniformly. Despite the cushioning effect of liquid layers, in some cases, a liquid can enhance material damage during impact due to penetration and stressing of surface cracks.

  7. Fluid jet electric discharge source

    DOEpatents

    Bender, Howard A. (Ripon, CA)

    2006-04-25

    A fluid jet or filament source and a pair of coaxial high voltage electrodes, in combination, comprise an electrical discharge system to produce radiation and, in particular, EUV radiation. The fluid jet source is composed of at least two serially connected reservoirs, a first reservoir into which a fluid, that can be either a liquid or a gas, can be fed at some pressure higher than atmospheric and a second reservoir maintained at a lower pressure than the first. The fluid is allowed to expand through an aperture into a high vacuum region between a pair of coaxial electrodes. This second expansion produces a narrow well-directed fluid jet whose size is dependent on the size and configuration of the apertures and the pressure used in the reservoir. At some time during the flow of the fluid filament, a high voltage pulse is applied to the electrodes to excite the fluid to form a plasma which provides the desired radiation; the wavelength of the radiation being determined by the composition of the fluid.

  8. Jet Boost Pumps For The Space Shuttle Main Engine

    NASA Technical Reports Server (NTRS)

    Meng, Sen Y.

    1991-01-01

    Brief report proposes use of jet boost pumps in conjunction with main pumps supplying liquid hydrogen and liquid oxygen to main engine of Space Shuttle. Main part of pump has no moving parts. Benefits include increased reliability, simplified ducts, and decreased weight.

  9. Deformation of a Thin Film by a Wall Jet

    NASA Astrophysics Data System (ADS)

    Hammoud, Naima; Al-Housseiny, Talal; Stone, Howard

    2012-11-01

    A variety of industrial processes such as jet stripping or jet wiping involve a high speed stream of gas flowing over a liquid film. In this work, we model this kind of situation by considering a thin viscous liquid film, over which a high Reynolds number laminar wall jet (or Glauert jet) is flowing. We study the shape of the thin liquid film, which is deformed due to the shear stress induced by a jet of a low-viscosity fluid. The mechanics of the jet, which is modeled by boundary-layer theory, is coupled to the mechanics of the thin film, which includes the influence of surface tension and buoyancy. We describe the unsteady shape of the film using the lubrication description to derive a nonlinear PDE that is coupled to the Glauert jet via interfacial stresses. For the steady state, we obtain analytical solutions in different asymptotic regimes. We compare our theoretical findings to numerical simulations conducted with the finite volume solver FLUENT.

  10. Partitioning of Aromatic Constituents into Water from Jet Fuels.

    PubMed

    Tien, Chien-Jung; Shu, Youn-Yuen; Ciou, Shih-Rong; Chen, Colin S

    2015-08-01

    A comprehensive study of the most commonly used jet fuels (i.e., Jet A-1 and JP-8) was performed to properly assess potential contamination of the subsurface environment from a leaking underground storage tank occurred in an airport. The objectives of this study were to evaluate the concentration ranges of the major components in the water-soluble fraction of jet fuels and to estimate the jet fuel-water partition coefficients (K fw) for target compounds using partitioning experiments and a polyparameter linear free-energy relationship (PP-LFER) approach. The average molecular weight of Jet A-1 and JP-8 was estimated to be 161 and 147 g/mole, respectively. The density of Jet A-1 and JP-8 was measured to be 786 and 780 g/L, respectively. The distribution of nonpolar target compounds between the fuel and water phases was described using a two-phase liquid-liquid equilibrium model. Models were derived using Raoult's law convention for the activity coefficients and the liquid solubility. The observed inverse, log-log linear dependence of the K fw values on the aqueous solubility were well predicted by assuming jet fuel to be an ideal solvent mixture. The experimental partition coefficients were generally well reproduced by PP-LFER. PMID:25840956

  11. Jet Substructure Without Trees

    SciTech Connect

    Jankowiak, Martin; Larkoski, Andrew J.; /SLAC /Stanford U., ITP

    2011-08-19

    We present an alternative approach to identifying and characterizing jet substructure. An angular correlation function is introduced that can be used to extract angular and mass scales within a jet without reference to a clustering algorithm. This procedure gives rise to a number of useful jet observables. As an application, we construct a top quark tagging algorithm that is competitive with existing methods. In preparation for the LHC, the past several years have seen extensive work on various aspects of collider searches. With the excellent resolution of the ATLAS and CMS detectors as a catalyst, one area that has undergone significant development is jet substructure physics. The use of jet substructure techniques, which probe the fine-grained details of how energy is distributed in jets, has two broad goals. First, measuring more than just the bulk properties of jets allows for additional probes of QCD. For example, jet substructure measurements can be compared against precision perturbative QCD calculations or used to tune Monte Carlo event generators. Second, jet substructure allows for additional handles in event discrimination. These handles could play an important role at the LHC in discriminating between signal and background events in a wide variety of particle searches. For example, Monte Carlo studies indicate that jet substructure techniques allow for efficient reconstruction of boosted heavy objects such as the W{sup {+-}} and Z{sup 0} gauge bosons, the top quark, and the Higgs boson.

  12. The Middle School Plunge

    ERIC Educational Resources Information Center

    West, Martin; Schwerdt, Guido

    2012-01-01

    Policymakers nationwide continue to wrestle with a basic question: At what grade level should students move to a new school? In the most common grade configuration in American school districts, public school students make two school transitions, entering a middle school in grade 6 or 7 and a high school in grade 9. This pattern reflects the

  13. Vietnam plunges ahead

    SciTech Connect

    Burr, M.T.

    1995-07-01

    Vietnam is moving fast. Facing the need to double its installed power generation capacity by the year 2000, Vietnam is pursuing a range of development alternatives to add an estimated 3,000 MW of new power plants. As part of the country`s progress toward a market economy, Vietnam has relaxed its rules regarding investment in power plants. The country enacted a new electricity law early in 1995, paving the way for private participation in the power sector.

  14. Large-eddy simulation of cavitating nozzle and jet flows

    NASA Astrophysics Data System (ADS)

    Örley, F.; Trummler, T.; Hickel, S.; Mihatsch, M. S.; Schmidt, S. J.; Adams, N. A.

    2015-12-01

    We present implicit large-eddy simulations (LES) to study the primary breakup of cavitating liquid jets. The considered configuration, which consists of a rectangular nozzle geometry, adopts the setup of a reference experiment for validation. The setup is a generic reproduction of a scaled-up automotive fuel injector. Modelling of all components (i.e. gas, liquid, and vapor) is based on a barotropic two-fluid two-phase model and employs a homogenous mixture approach. The cavitating liquid model assumes thermodynamic- equilibrium. Compressibility of all phases is considered in order to capture pressure wave dynamics of collapse events. Since development of cavitation significantly affects jet break-up characteristics, we study three different operating points. We identify three main mechanisms which induce primary jet break-up: amplification of turbulent fluctuations, gas entrainment, and collapse events near the liquid-gas interface.

  15. Separation of gas from liquid in a two-phase flow system

    NASA Technical Reports Server (NTRS)

    Hayes, L. G.; Elliott, D. G.

    1973-01-01

    Separation system causes jets which leave two-phase nozzles to impinge on each other, so that liquid from jets tends to coalesce in center of combined jet streams while gas phase is forced to outer periphery. Thus, because liquid coalescence is achieved without resort to separation with solid surfaces, cycle efficiency is improved.

  16. What ignites optical jets?

    NASA Astrophysics Data System (ADS)

    Jester, S.

    2003-10-01

    The properties of radio galaxies and quasars with and without optical or X-ray jets are compared. The majority of jets from which high-frequency emission has been detected so far (13 with optical emission, 11 with X-rays, 13 with both) are associated with the most powerful radio sources at any given redshift. It is found that optical/X-ray jet sources are more strongly beamed than the average population of extragalactic radio sources. This suggests that the detection or non-detection of optical emission from jets has so far been dominated by surface brightness selection effects, not by jet physics. It implies that optical jets are much more common than is currently appreciated.

  17. Relativistic Jets in Collapsars

    NASA Astrophysics Data System (ADS)

    Zhang, Weiqun; Woosley, S. E.; MacFadyen, A. I.

    2003-04-01

    We examine the propagation of two-dimensional relativistic jets through the stellar progenitor in the collapsar model for gamma-ray bursts. In agreement with previous studies, we find that the jet is collimated by its passage. Moreover, interaction of the jet with the star causes mixing that sporadically decelerates the jet, leading to a highly variable Lorentz factor. The jet that finally emerges has a moderate Lorentz factor, but a very large internal energy loading. In a second series of calculations we follow the emergence of such enegy-loaded jets from the star. For the initial conditions chosen, conversion of the remaining internal energy gives a terminal Lorentz factor of approximately 150. Implications of our calculations for GRB light curves, the luminosity-variability relation, and the GRB-supernova association are discussed.

  18. Relativistic Jets in Collapsars

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Woosley, S.

    2002-05-01

    We examine the propagation of multi-dimensional relativistic jets through the stellar progenitor in the collapsar model for gamma-ray bursts. In agreement with previous studies, we find that the jet is collimated by its passage through the stellar mantle. Interaction of the jet with the star causes mixing with nearly stationary material that sporadically decelerates the jet, leading to a highly variable Lorentz factor. The jet that finally emerges has a moderate Lorentz factor but a very large internal energy loading. Conversion of the remaining internal energy gives terminal Lorentz factors of approximately 150 for the initial conditions chosen. Implications of our calculations for GRB light curves, the luminosity-variablity relation, the GRB-supernova association, and a possible general model for GRB jets are discussed.

  19. What ignites optical jets?

    SciTech Connect

    Sebastian Jester

    2002-12-23

    The properties of radio galaxies and quasars with and without optical or X-ray jets are compared. The majority of jets from which high-frequency emission has been detected so far (13 with optical emission, 11 with X-rays, 13 with both) are associated with the most powerful radio sources at any given redshift. It is found that optical/X-ray jet sources are more strongly beamed than the average population of extragalactic radio sources. This suggests that the detection or non-detection of optical emission from jets has so far been dominated by surface brightness selection effects, not by jet physics. It implies that optical jets are much more common than is currently appreciated.

  20. Cavitating vortex generation by a submerged jet

    SciTech Connect

    Belyakov, G. V.; Filippov, A. N.

    2006-05-15

    The surface geometry of a cavitating vortex is determined in the limit of inviscid incompressible flow. The limit surface is an ovaloid of revolution with an axis ratio of 5: 3. It is shown that a cavitating vortex ring cannot develop if the cavitation number is lower than a certain critical value. Experiments conducted at various liquid pressures and several jet exit velocities confirm the existence of a critical cavitation number close to 3. At cavitation numbers higher than the critical one, the cavitating vortex ring does not develop. At substantially lower cavitation numbers (k {<=} 0.1), an elongated asymmetric cavitation bubble is generated, with an axial reentrant jet whose length can exceed the initial jet length by several times. This flow structure is called an asymmetric cavitating vortex, even though steady motion of this structure has not been observed.

  1. Jet pump assisted arterial heat pipe

    NASA Technical Reports Server (NTRS)

    Bienert, W. B.; Ducao, A. S.; Trimmer, D. S.

    1978-01-01

    This paper discusses the concept of an arterial heat pipe with a capillary driven jet pump. The jet pump generates a suction which pumps vapor and noncondensible gas from the artery. The suction also forces liquid into the artery and maintains it in a primed condition. A theoretical model was developed which predicts the existence of two stable ranges. Up to a certain tilt the artery will prime by itself once a heat load is applied to the heat pipe. At higher tilts, the jet pump can maintain the artery in a primed condition but self-priming is not possible. A prototype heat pipe was tested which self-primed up to a tilt of 1.9 cm, with a heat load of 500 watts. The heat pipe continued to prime reliably when operated as a VCHP, i.e., after a large amount of noncondensible gas was introduced.

  2. Stability of Astrophysical Jets

    NASA Astrophysics Data System (ADS)

    Komissarov, Serguei

    2014-08-01

    Compared to their terrestrial and laboratory counterparts, the astrophysical jets appear to be very stable - for example, the extragalactic jets cross the distances that are up to one billion times larger than their initial radius. Many years after their discovery and numerous theoretical and numerical studies, there is still no consensus as to what is behind this remarkable stability. We argue that this must be a very robust reason, not sensitive to the details of internal jet structure and composition, but rather reflecting their environment. In particular, the astrophysical jets propagate through "atmospheres" with rapidly declining pressure (and density), which results in their rapid sideways expansion - e.g. the radius of the M87 jet increases by the factor close to one million. Such a rapid expansion renders the causal connectivity across jets ineffective and can even suppress it altogether, resulting infree expansion of the jets. When the connectivity is lacking, the jets cannot develop coherent large scale displacements, which otherwise would threaten their integrity and survival. We present the results of new 3D numerical simulations of expanding magnetized relativistic jets, designed to test this idea.

  3. Properties of gluon jets

    SciTech Connect

    Sugano, K.

    1986-09-01

    The properties of gluon jets are reviewed from an experimental point of view. The measured characteristics are compared to theoretical expectations. Although neither data nor models for the gluon jets are in the mature stage, there are remarkable agreements and also intriguing disagreements between experiment and theory. Since much interesting data have begun to emerge from various experiments and the properties of gluon jets are deeply rooted in the basic structure of non-Abelian gauge theory, the study of gluon jets casts further light on our understanding of QCD. Finally, the future prospects are discussed.

  4. On the Evolution of Vorticity in Pulsating Jets in Crossflow

    NASA Astrophysics Data System (ADS)

    Cortelezzi, Luca; Karagozian, Ann R.

    1999-11-01

    Significant alteration of the mixing characteristics of jets in crossflow may be achieved when the jet is pulsed in the case of liquids(Johari, et al., AIAA J., 37:7, pp. 2195-2203, 1999) or acoustically driven in the case of gases(Kelso, et al., JFM, 306, pp. 111-144, 1996). The three-dimensional vortex element simulations performed here focus on exploring the vorticity evolution associated with such jets and the role of vorticity in producing experimentally observed increases in jet spreading and penetration during excitation. Alternative modes of temporal jet excitation are examined, including sinusoidal and square wave variation in jet velocity for a variety of input frequencies, amplitudes, and duty cycles. It is seen that these jet forcing parameters control vortex bending, tilting, and reconnection which in turn are responsible for the overall jet structure as well as enhanced jet mixing and penetration.

  5. Contact Angle Influence on Geysering Jets in Microgravity Investigated

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2004-01-01

    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 liquid-free 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 be used to 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.

  6. Rectangular jets in a crossflow

    NASA Technical Reports Server (NTRS)

    Kavsaoglu, M. S.; Schetz, J. A.; Jakubowski, A. K.

    1989-01-01

    Rectangular jets injected from a flat plate into a crossflow at large angles have been studied. Results were obtained as surface pressure distributions, mean velocity vector plots, turbulence intensities, and Reynolds stresses in the jet plume. The length-to-width ratio of the jets was 4, and the jets were aligned streamwise as single and side-by-side dual jets. The jet injection angles were 90 and 60 deg. Surface pressure distribution results were obtained for jet-to-freestream velocity ratios of 2.2, 4, and 8. Mean flow and turbulence flowfield data were obtained for the side-by-side dual jets, mainly for the jet-to-freestream velocity ratio of 4. The jets featured strong negative pressure peaks near the front nozzle corners. The 60-deg jets produced lower magnitude negative pressures, which are distributed over a lesser area when compared to the 90-deg jets.

  7. Rectangular jets in a crossflow

    SciTech Connect

    Kavsaoglu, M.S.; Schetz, J.A.; Jakubowski, A.K. )

    1989-09-01

    Rectangular jets injected from a flat plate into a crossflow at large angles have been studied. Results were obtained as surface pressure distributions, mean velocity vector plots, turbulence intensities, and Reynolds stresses in the jet plume. The length-to-width ratio of the jets was 4, and the jets were aligned streamwise as single and side-by-side dual jets. The jet injection angles were 90 and 60 deg. Surface pressure distribution results were obtained for jet-to-freestream velocity ratios of 2.2, 4, and 8. Mean flow and turbulence flowfield data were obtained for the side-by-side dual jets, mainly for the jet-to-freestream velocity ratio of 4. The jets featured strong negative pressure peaks near the front nozzle corners. The 60-deg jets produced lower magnitude negative pressures, which are distributed over a lesser area when compared to the 90-deg jets. 26 refs.

  8. High-speed jetting and spray formation from bubble collapse

    NASA Astrophysics Data System (ADS)

    Karri, Badarinath; Avila, Silvestre Roberto Gonzalez; Loke, Yee Chong; O'Shea, Sean J.; Klaseboer, Evert; Khoo, Boo Cheong; Ohl, Claus-Dieter

    2012-01-01

    A method to create impacting jets at the micrometer length scale by means of a collapsing cavitation bubble is presented. A focused shock wave from a lithotripter leads to the nucleation of a cavitation bubble below a hole of 25 μm diameter etched in a silicon plate. The plate is placed at an air-water interface. The expansion and collapse of the bubble leads to two separate jets—an initial slow jet of velocity ˜10 m/s and a later faster jet of velocity ˜50 m/s. The jets subsequently impact coaxially, resulting in a circular sheet of liquid in the plane perpendicular to their axis. The sheet is characterized by a ring of droplets at its rim and breaks up into a spray as the shock pressure is increased. The results demonstrate an approach to create a high-speed jet and fine spray on demand at the micrometer scale.

  9. Global stability of gravitationally stretched capillary jets

    NASA Astrophysics Data System (ADS)

    Rubio-Rubio, Mariano; Sevilla, Alejandro; Gordillo, Jos Manuel

    2013-11-01

    We analyze the global linear stability of capillary jets stretched by gravity both experimentally and theoretically, extending the work by Sauter & Buggisch (J. Fluid Mech. vol. 533, 2005, pp. 237-257). Our results reveal the essential stabilizing role played by the axial curvature of the jet, the latter effect being especially relevant for injectors with a large diameter. The theoretical description, based on the one-dimensional mass and momentum equations retaining the exact expression for the interfacial curvature, accurately predicts the onset of jet self-excited oscillations experimentally observed for wide ranges of liquid viscosity and injector diameter. The marginal self-sustained oscillations observed in the experiments are shown to correspond to the excitation of the leading global mode of the jet. The model developed in the present work shows better agreement with the experimental jetting-dripping transition events than those available in the literature, thus allowing us to conclude that, surprisingly, the size of the steady threads produced at a given distance from the exit can be reduced by increasing the nozzle diameter. The proposed formulation allows to describe the inviscid limit, and experiments are being performed to study this distinguished case. Supported by Spanish MINECO under projects DPI 2011-28356-C03-01 and DPI 2011-28356-C03-02.

  10. Jetting instability mechanisms of particles from explosive dispersal

    NASA Astrophysics Data System (ADS)

    Ripley, R. C.; Zhang, F.

    2014-05-01

    The formation of post-detonation 'particle' jets is widely observed in many problems associated with explosive dispersal of granular materials and liquids. Jets have been shown to form very early, however the mechanism controlling the number of jetting instabilities remains unresolved despite a number of active theories. Recent experiments involving cylindrical charges with a range of central explosive masses for dispersal of dry solid particles and pure liquid are used to formulate macroscopic numerical models for jet formation and growth. The number of jets is strongly related to the dominant perturbation during the shock interaction timescale that controls the initial fracturing of the particle bed and liquid bulk. Perturbations may originate at the interfaces between explosive, shock-dispersed media, and outer edge of the charge due to Richtmyer-Meshkov instabilities. The inner boundary controls the number of major structures, while the outer boundary may introduce additional overlapping structures and microjets that are overtaken by the major structures. In practice, each interface may feature a thin casing material that breaks up, thereby influencing or possibly dominating the instabilities. Hydrocode simulation is used to examine the role of each interface in conjunction with casing effects on the perturbation leading to jet initiation. The subsequent formation of coherent jet structures requires dense multiphase flow of particles and droplets that interact though inelastic collision, agglomeration, and turbulent flow. Macroscopic multiphase flow simulation shows dense particle clustering and major jet structures overtaking smaller instabilities. Late-time dispersal is controlled by particle drag and evaporation of droplets. Numerical results for dispersal and jetting evolution are compared with experiments.

  11. Numerical simulation of jet noise

    NASA Technical Reports Server (NTRS)

    Van Dalsem, W. R.

    1992-01-01

    Jet noise and jet-induced structural loads have become key issues in the design of commercial and military aircraft. Computational Fluid Dynamics (CFD) can be of use in predicting the underlying jet shear-layer instabilities and, in conjunction with classical acoustic theory, jet noise. The computational issues involved in the resolution of high Reynolds number unsteady jet flows are addressed in this paper. Once these jet flows can be accurately resolved, it should be possible to use acoustic theory to extract, for example, the far-field jet noise. An assessment of future work and computational resources required for directly computing far-field jet noise is also presented.

  12. Description of Jet Breakup

    NASA Technical Reports Server (NTRS)

    Papageorgiou, Demetrios T.

    1996-01-01

    In this article we review recent results on the breakup of cylindrical jets of a Newtonian fluid. Capillary forces provide the main driving mechanism and our interest is in the description of the flow as the jet pinches to form drops. The approach is to describe such topological singularities by constructing local (in time and space) similarity solutions from the governing equations. This is described for breakup according to the Euler, Stokes or Navier-Stokes equations. It is found that slender jet theories can be applied when viscosity is present, but for inviscid jets the local shape of the jet at breakup is most likely of a non-slender geometry. Systems of one-dimensional models of the governing equations are solved numerically in order to illustrate these differences.

  13. Modeling confined jet flow

    NASA Astrophysics Data System (ADS)

    Yule, A. J.; Damou, M.; Kostopoulos, D.

    1993-03-01

    The prediction of confined jet mixing, which occurs in many processes from jet pumps to furnaces, is studied by testing and improving turbulence models. Numerical simulations of axisymmetric parabolic jet flows, with the two-equation k-epsilon eddy-viscosity model and the second-moment closure in its algebraic form, are compared with measurements. This leads to the identification of defects that cause high rates of mixing, similar to those shown in earlier work with free jets. Modifications to the dissipation rate equation, proposed for the free jet, are addressed by examining the effects of anisotropy-related proposals and the sensitization to irrotational strains. The involvement of large structures in transport phenomena is also considered via bulk-convection-based models. A combination of 20 percent gradient diffusion and 80 percent bulk convection appears to mimic the transport process for turbulent energy reasonably well.

  14. Jet Lag in Athletes

    PubMed Central

    Lee, Aaron; Galvez, Juan Carlos

    2012-01-01

    Context: Prolonged transmeridian air travel can impart a physical and emotional burden on athletes in jet lag and travel fatigue. Jet lag may negatively affect the performance of athletes. Study Type: Descriptive review. Evidence Acquisition: A Medline search for articles relating to jet lag was performed (1990-present), as was a search relating to jet lag and athletes (1983-January, 2012). The results were reviewed for relevance. Eighty-nine sources were included in this descriptive review. Results: Behavioral strategies are recommended over pharmacological strategies when traveling with athletes; pharmacological aides may be used on an individual basis. Strategic sleeping, timed exposure to bright light, and the use of melatonin are encouraged. Conclusions: There is strong evidence that mood and cognition are adversely affected by jet lag. Some measures of individual and team performance are adversely affected as well. PMID:23016089

  15. Jet physics at CDF

    SciTech Connect

    Melese, P.

    1997-05-01

    We present high E{sub T} jet measurements from CDF at the Fermilab Tevatron Collider. The incfilusive jet cross section at {radical}s = 1800 GeV with {approximately} 5 times more data is compared to the published CDF results, preliminary D0 results, and next-to-leading order QCD predictions. The {summation}E{sub T} cross section is also compared to QCD predictions and the dijet angular distribution is used to place a limit on quark compositeness. The inclusive jet cross section at {radical}s = 630 GeV is compared with that at 1800 GeV to test the QCD predictions for the scaling of jet cross sections with {radical}s. Finally, we present momentum distributions of charged particles in jets and compare them to Modified Leading Log Approximation predictions.

  16. Simple and double emulsions via coaxial jet electrosprays.

    PubMed

    Marín, Alvaro G; Loscertales, Ignacio G; Márquez, M; Barrero, A

    2007-01-01

    We report for the first time the generation of electrified coaxial jets of micrometric diameter in liquid media. Scaling laws to predict the inner and outer diameter of the coaxial jet are given. We show some experiments illustrating the formation process of the coaxial jet, and demonstrate how this process can be used to yield either o/w (oil in water) or o/w/o (oil/water/oil) emulsions of micrometric size. Some interesting analogies with other hydrodynamic focusing processes are also pointed out. PMID:17358479

  17. Dynamics of bouncing-versus-merging response in jet collision

    NASA Astrophysics Data System (ADS)

    Li, Minglei; Saha, Abhishek; Zhu, D. L.; Sun, Chao; Law, Chung K.

    2015-08-01

    A new regime of oblique jet collision, characterized by low impact inertia and jet merging through bridge formation, is observed and thereby completes the entire suite of possible jet collision outcomes of (soft) merging, bouncing, and (hard) merging with increasing inertia. These distinct regimes, together with the observed dependence of the collision outcome on the impact angle and liquid properties, are characterized through scaling analysis by considering the competing effects of impact inertia, surface tension, and viscous thinning of the interfacial air gap leading to merging.

  18. Interaction between jets during laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Hennig, G.; Delaporte, P.; Serra, P.

    2014-07-01

    Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.

  19. Interaction between jets during laser-induced forward transfer

    SciTech Connect

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P.; Hennig, G.; Delaporte, P.

    2014-07-07

    Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.

  20. On the electrospraying of conducting liquids in dielectric liquid baths

    NASA Astrophysics Data System (ADS)

    Gómez-Marín, Álvaro; Loscertales, Ignacio G.; Márquez, Manuel; Barrero, Antonio

    2004-11-01

    Steady cone-jets of conducting liquids inside dielectris liquid baths are easily obtained. In particular water and glycerol have been electrosprayed in either heptane or vaseline oil. Experimental results show that the current emitted from the cone-jet depends on the flow rate and the liquid properties in the same way that it does in air. On the contrary, the effects of the bath inertia plays an important role to determine the size of droplets. Also the addition of small amounts of both water-soluble and lipid-soluble surfactants changes appreciably the spray characteristics. The influence of either lipid-soluble or water soluble surfactants at different concentrations on the droplet size of a water electrospray in oil or heptane has been experimentally obtained. In the case of glycerol, the high viscosity of the fluid gives rise to very long jets presenting kink instabilitiy far from the vertex cone. Much more stable jets are obtained by adding small amounts of lipid or water-soluble surfactants. In those cases, the electric field on the very long jet of glycerol is very small and a big droplet is formed at the end of the jet.

  1. Liquid Wall Chambers

    SciTech Connect

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  2. The effect of jet shape on jet injection.

    PubMed

    Geehoon Park; Modak, Ashin; Hogan, N Catherine; Hunter, Ian W

    2015-08-01

    The effects of the dispersion pattern of a needle-free jet injector are explored. The shape of the jets were compared using a high-speed video camera and jet injections of collimated and dispersed fluid jets with a Lorentz-force actuated jet injector were made into acrylamide gel and post-mortem porcine tissue. A custom-built high-speed X-ray imaging system was used in order to observe the dynamics of the dispersion mechanism for each injection in real time. We show that a collimated jet stream results in greater tissue penetration than a dispersed jet stream. PMID:26737989

  3. Jet noise suppression by swirling the jet flow.

    NASA Technical Reports Server (NTRS)

    Schwartz, I. R.

    1973-01-01

    The effect of swirling flow on jet noise suppression was experimentally investigated in a relatively small, low-thrust, fan-jet engine. Measurements of acoustic properties of the near and far fields, jet-flow characteristics, and engine thrust were made with and without stationary swirl vanes installed in the primary exhaust nozzle. Preliminary test results indicate that substantial reductions in jet overall sound pressure levels and overall acoustic power were obtained with minimal thrust losses. Based on preliminary analysis, present results, and previous experiments with swirling hot jets, it is predicted that even greater jet noise reductions can be obtained in higher thrust engines, particularly with afterburning, by swirling jet exhaust.

  4. Solar coronal jets

    NASA Astrophysics Data System (ADS)

    Dobrzyck, D.

    The solar jets were first observed by SOHO instruments (EIT, LASCO, UVCS) during the previous solar minimum. They were small, fast ejections originating from flaring UV bright points within large polar coronal holes. The obtained data provided us with estimates of the jet plasma conditions, dynamics, evolution of the electron temperature and heating rate required to reproduce the observed ionization state. To follow the polar jets through the solar cycle a special SOHO Joint Observing Program (JOP 155) was designed. It involves a number of SOHO instruments (EIT, CDS, UVCS, LASCO) as well as TRACE. The coordinated observations have been carried out since April 2002. The data enabled to identify counterparts of the 1996-1998 solar minimum jets. Their frequency of several events per day appear comparable to the frequency from the previous solar minimum. The jets are believed to be triggered by field line reconnection between emerging magnetic dipole and pre-existing unipolar field. Existing models predict that the hot jet is formed together with another jet of a cool material. The particular goal of the coordinated SOHO and TRACE observations was to look for possible association of the hot and cool plasma ejections. Currently there is observational evidence that supports these models.

  5. Relativistic jets from supernovae

    NASA Astrophysics Data System (ADS)

    Gomez, Enrique Alberto

    Stars with masses greater than eight times the Sun's explode as supernovae when they fail to extract energy from nuclear fusion. Some of these supernova progenitors shed their outermost hydrogen envelope and acquire high rates of rotation at their cores before they explode. During a supernova collapse phase these stars form a dense disk of material around a degenerate core, which in turn powers energetic jets of material that propagate through the stellar atmosphere outwards. These jets soon acquire bulk speeds close to the speed of light. We perform a detailed analysis of numerical, hydrodynamic simulations of these jets to determine their stability to pressure waves that grow as Kelvin- Helmholtz modes from the interface between the jet and the stellar medium. We have discovered that the pressure profile of the star makes these jets unstable to such modes just before the jet breaks out compared to the region closest to the center. We have also discovered that only the most energetic jets predicted in this theory support such modes over the time it takes for the jet to reach the stellar surface. When we follow the jets in the numerical simulations as they break out, we calculate that they become relativistic winds that carry within them enhancements in their pressure and velocity, which can turn into internal shocks. These shocks could accelerate charged particles that cool through gamma ray emission and thus convert the kinetic energy of the wind into radiation that we can detect as a long gamma-ray burst. However, we have found that the fastest moving core of this wind is unlikely to produce substantial internal shocks. Shocks are most likely to happen at an angle from the center of a conical wind. We present a test of this model for such emission geometry and its corresponding rate for detected gamma ray bursts above a given gamma-ray flux.

  6. Jet Physics at CDF

    SciTech Connect

    Sally Seidel

    2004-06-28

    Jets have been studied by the CDF Collaboration [1] as a means of searching for new particles and interactions, testing a variety of perturbative QCD predictions, and providing input for the global parton distribution function (PDF) fits. Unless otherwise indicated below, the jets were reconstructed using a cone algorithm [2] with cone radius R = 0.7 from data taken at the Fermilab Tevatron collider in Run 2, 2001-2003, with {radical}s = 1.96 TeV. Central jets, in the pseudorapidity range relative to fixed detector coordinates 0.1 < |{eta}| < 0.7, are used.

  7. Relativistic Jets in Collapsars

    NASA Astrophysics Data System (ADS)

    Zhang, Weiqun; Woosley, S. E.; MacFadyen, A. I.

    2003-03-01

    We examine the propagation of two-dimensional relativistic jets through the stellar progenitor in the collapsar model for gamma-ray bursts (GRBs). Each jet is parameterized by a radius where it is introduced and by its initial Lorentz factor, opening angle, power, and internal energy. In agreement with previous studies, we find that relativistic jets are collimated by their passage through the stellar mantle. Starting with an initial half-angle of up to 20°, they emerge with half-angles that, though variable with time, are around 5°. Interaction of these jets with the star and their own cocoons also causes mixing that sporadically decelerates the flow. We speculate that this mixing instability is chiefly responsible for the variable Lorentz factor needed in the internal shock model and for the complex light curves seen in many GRBs. In all cases studied, the jet is shocked deep inside the star following a brief period of adiabatic expansion. This shock converts most of the jet's kinetic energy into internal energy, so even initially ``cold'' jets become hot after going a short distance. The jet that finally emerges from the star thus has a moderate Lorentz factor, modulated by mixing, and a very large internal energy. In a second series of calculations, we follow the escape of that sort of jet. Conversion of the remaining internal energy gives terminal Lorentz factors along the axis of approximately 150 for the initial conditions chosen. Because of the large ratio of internal to kinetic energy in both the jet (>=80%) and its cocoon, the opening angle of the final jet is significantly greater than at breakout. A small amount of material emerges at large angles, but with a Lorentz factor still sufficiently large to make a weak GRB. This leads us to propose a ``unified model'' in which a variety of high-energy transients, ranging from X-ray flashes to ``classic'' GRBs, may be seen depending on the angle at which a standard collapsar is observed. We also speculate that the breakout of a relativistic jet and its collision with the stellar wind will produce a brief transient with properties similar to the class of ``short-hard'' GRBs. Implications of our calculations for GRB light curves, the luminosity-variability relation, and the GRB-supernova association are also discussed.

  8. Status of jet noise

    NASA Technical Reports Server (NTRS)

    Banerian, G.

    1977-01-01

    The fundamentals of jet noise generation and suppression have been studied in great detail over the past twenty-five years. Considerable progress has been made recently in our understanding of this subject, though some aspects of it remain perplexing. The importance of accounting for the influence of the jets mean flow in shrouding acoustic sources is now recognized and the large amount of information obtained on jet noise reduction schemes, e.g., the internal mixer nozzle, the inverted profile nozzle and multi-element suppressors, has helped clarify trends and identify remaining issues. Current understanding of inflight effects is limited and in need of much more attention.

  9. Angular Scaling In Jets

    SciTech Connect

    Jankowiak, Martin; Larkoski, Andrew J.; /SLAC

    2012-02-17

    We introduce a jet shape observable defined for an ensemble of jets in terms of two-particle angular correlations and a resolution parameter R. This quantity is infrared and collinear safe and can be interpreted as a scaling exponent for the angular distribution of mass inside the jet. For small R it is close to the value 2 as a consequence of the approximately scale invariant QCD dynamics. For large R it is sensitive to non-perturbative effects. We describe the use of this correlation function for tests of QCD, for studying underlying event and pile-up effects, and for tuning Monte Carlo event generators.

  10. Numerical simulation of electrospray in the cone-jet mode.

    PubMed

    Herrada, M A; Lpez-Herrera, J M; Gan-Calvo, A M; Vega, E J; Montanero, J M; Popinet, S

    2012-08-01

    We present a robust and computationally efficient numerical scheme for simulating steady electrohydrodynamic atomization processes (electrospray). The main simplification assumed in this scheme is that all the free electrical charges are distributed over the interface. A comparison of the results with those calculated with a volume-of-fluid method showed that the numerical scheme presented here accurately describes the flow pattern within the entire liquid domain. Experiments were performed to partially validate the numerical predictions. The simulations reproduced accurately the experimental shape of the liquid cone jet, providing correct values of the emitted electric current even for configurations very close to the cone-jet stability limit. PMID:23005852

  11. Laser-induced micro-jetting from armored droplets

    NASA Astrophysics Data System (ADS)

    Marston, J. O.; Thoroddsen, S. T.

    2015-07-01

    We present findings from an experimental study of laser-induced cavitation within a liquid drop coated with a granular material, commonly referred to as "armored droplets" or "liquid marbles." The cavitation event follows the formation of plasma after a nanosecond laser pulse. Using ultra-high-speed imaging up to 320,610 fps, we investigate the extremely rapid dynamics following the cavitation, which manifests itself in the form of a plethora of micro-jets emanating simultaneously from the spaces between particles on the surface of the drop. These fine jets break up into droplets with a relatively narrow diameter range, on the order of 10 ?m.

  12. Optimized Parameters for a Mercury Jet Target

    SciTech Connect

    Ding, X.; Kirk, H.

    2010-12-01

    A study of target parameters for a high-power, liquid mercury jet target system for a neutrino factory or muon collider is presented. Using the MARS code, we simulate particle production initiated by incoming protons with kinetic energies between 2 and 100 GeV. For each proton beam energy, we maximize production by varying the geometric parameters of the target: the mercury jet radius, the incoming proton beam angle, and the crossing angle between the mercury jet and the proton beam. The number of muons surviving through an ionization cooling channel is determined as a function of the proton beam energy. We optimize the mercury jet target parameters: the mercury jet radius, the incoming proton beam angle and the crossing angle between the mercury jet and the proton beam for each proton beam energy. The optimized target radius varies from about 0.4 cm to 0.6 cm as the proton beam energy increases. The optimized beam angle varies from 75 mrad to 120 mrad. The optimized crossing angle is near 20 mrad for energies above 5 GeV. These values differ from earlier choices of 67 mrad for the beam angle and 33 mrad for the crossing angle. These new choices for the beam parameters increase the meson production by about 20% compared to the earlier parameters. Our study demonstrates that the maximum meson production efficiency per unit proton beam power occurs when the proton kinetic energy is in the range of 5-15 GeV. Finally, the dependence on energy of the number of muons at the end of the cooling channel is nearly identical to the dependence on energy of the meson production 50 m from the target. This demonstrates that the target parameters can be optimized without the additional step of running the distribution through a code such as ICOOL that simulates the bunching, phase rotation, and cooling.

  13. Comparison of heat transfer in liquid and slush nitrogen by numerical simulation of cooling rates for French straws used for sperm cryopreservation.

    PubMed

    Sansinena, M; Santos, M V; Zaritzky, N; Chirife, J

    2012-05-01

    Slush nitrogen (SN(2)) is a mixture of solid nitrogen and liquid nitrogen, with an average temperature of -207 C. To investigate whether plunging a French plastic straw (commonly used for sperm cryopreservation) in SN(2) substantially increases cooling rates with respect to liquid nitrogen (LN(2)), a numerical simulation of the heat conduction equation with convective boundary condition was used to predict cooling rates. Calculations performed using heat transfer coefficients in the range of film boiling confirmed the main benefit of plunging a straw in slush over LN(2) did not arise from their temperature difference (-207 vs. -196 C), but rather from an increase in the external heat transfer coefficient. Numerical simulations using high heat transfer (h) coefficients (assumed to prevail in SN(2)) suggested that plunging in SN(2) would increase cooling rates of French straw. This increase of cooling rates was attributed to a less or null film boiling responsible for low heat transfer coefficients in liquid nitrogen when the straw is placed in the solid-liquid mixture or slush. In addition, predicted cooling rates of French straws in SN(2) tended to level-off for high h values, suggesting heat transfer was dictated by heat conduction within the liquid filled plastic straw. PMID:22225685

  14. Jet lag prevention

    MedlinePLUS

    ... your internal clock before you travel. While in flight: DO NOT sleep unless it matches the bedtime ... decrease jet lag. If you will be in flight during the bedtime of your destination, take some ...

  15. Jet lag prevention

    MedlinePLUS

    ... time as you begin the trip. While in flight, avoid sleeping at times that wouldn't be ... stores, may help decrease jet lag. While in flight, consider taking some melatonin (generally 3 - 5 milligrams) ...

  16. Dilution jet mixing program

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Coleman, E.; Johnson, K.

    1984-01-01

    Parametric tests were conducted to quantify the mixing of opposed rows of jets (two-sided injection) in a confined cross flow. Results show that jet penetrations for two sided injections are less than that for single-sided injections, but the jet spreading rates are faster for a given momentum ratio and orifice plate. Flow area convergence generally enhances mixing. Mixing characteristics with asymmetric and symmetric convergence are similar. For constant momentum ratio, the optimum S/H(0) with in-line injections is one half the optimum value for single sided injections. For staggered injections, the optimum S/H(0) is twice the optimum value for single-sided injection. The correlations developed predicted the temperature distributions within first order accuracy and provide a useful tool for predicting jet trajectory and temperature profiles in the dilution zone with two-sided injections.

  17. Counterflowing Jet Subsystem Design

    NASA Technical Reports Server (NTRS)

    Farr, Rebecca; Daso, Endwell; Pritchett, Victor; Wang, Ten-See

    2010-01-01

    A counterflowing jet design (a spacecraft and trans-atmospheric subsystem) employs centrally located, supersonic cold gas jets on the face of the vehicle, ejecting into the oncoming free stream. Depending on the supersonic free-stream conditions and the ejected mass flow rate of the counterflowing jets, the bow shock of the vehicle is moved upstream, further away from the vehicle. This results in an increasing shock standoff distance of the bow shock with a progressively weaker shock. At a critical jet mass flow rate, the bow shock becomes so weak that it is transformed into a series of compression waves spread out in a much wider region, thus significantly modifying the flow that wets the outer surfaces, with an attendant reduction in wave and skin friction drag and aerothermal loads.

  18. Jets in hadronic reactions

    SciTech Connect

    Paige, F.E.

    1983-01-01

    Recent experimental data on the properties of jets in hadronic reactions are reviewed and compared with theoretical expectations. Jets are clearly established as the dominant process for high E/sub T/ events in hadronic reactions. The cross section and the other properties of these events are in qualitative and even semiquantitative agreement with expectations based on perturbative QCD. However, we can not yet make precise tests of QCD, primarily because there are substantial uncertainties in the theoretical calculations. 45 references. (WHK)

  19. Jet lag modification.

    PubMed

    Simmons, Emily; McGrane, Owen; Wedmore, Ian

    2015-01-01

    Athletes often are required to travel for sports participation, both for practice and competition. A number of those crossing multiple time zones will develop jet lag disorder with possible negative consequences on their performance. This review will discuss the etiology of jet lag disorder and the techniques that are available to shorten or minimize its effects. This includes both pharmacological and nonpharmacological approaches. PMID:25757008

  20. Investigations of ducted jets

    NASA Astrophysics Data System (ADS)

    Yule, A. J.; Damou, M.

    1991-07-01

    An attempt is made to obtain detailed information on ducted-jet flows for the testing of CFD modeling methods when applied to this type of flow. This goal was achieved for the case of ducted jets developing from a turbulent pipe flow in the nozzle. The results provide useful data that can be interpreted in terms of the physical structure of the turbulent flows.

  1. Free compressible jet investigation

    NASA Astrophysics Data System (ADS)

    De Gregorio, Fabrizio

    2014-03-01

    The nozzle pressure ratio (NPR) effect on a supersonic turbulent jet was investigated. A dedicated convergent/divergent nozzle together with a flow feeding system was designed and manufactured. A nozzle Mach exit of M j = 1.5 was selected in order to obtain a convective Mach number of M c = 0.6. The flow was investigated for over-expanded, correctly expanded and under-expanded jet conditions. Mach number, total temperature and flow velocity measurements were carried out in order to characterise the jet behaviour. The inlet conditions of the jet flow were monitored in order to calculate the nozzle exit speed of sound and evaluate the mean Mach number distribution starting from the flow velocity data. A detailed analysis of the Mach results obtained by a static Pitot probe and by a particle image velocimetry measurement system was carried out. The mean flow velocity was investigated, and the axial Mach decay and the spreading rate were associated with the flow structures and with the compressibility effects. Aerodynamics of the different jet conditions was evaluated, and the shock cells structures were detected and discussed correlating the jet structure to the flow fluctuation and local turbulence. The longitudinal and radial distribution of the total temperature was investigated, and the temperature profiles were analysed and discussed. The total temperature behaviour was correlated to the turbulent phenomena and to the NPR jet conditions. Self-similarity condition was encountered and discussed for the over-expanded jet. Compressibility effects on the local turbulence, on the turbulent kinetic energy and on the Reynolds tensor were discussed.

  2. Radiation from Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Sol, H.; Medvedev, M.; Zhang, B.; Nordlund, A.; Frederiksen, J. T.; Fishman, G. J.; Preece, R.

    2008-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the presence of relativistic jets, instabilities such as the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability create collisionless shocks, which are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons in small-scale magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation, a case of diffusive synchrotron radiation, may be important to understand the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  3. Relativistic Jets from Collapsars

    NASA Astrophysics Data System (ADS)

    Aloy, M. A.; Mller, E.; Ibez, J. M.; Mart, J. M.; MacFadyen, A.

    2000-03-01

    Using a collapsar progenitor model of MacFadyen & Woosley, we have simulated the propagation of an axisymmetric jet through a collapsing rotating massive star with the GENESIS multidimensional relativistic hydrodynamic code. The jet forms as a consequence of an assumed (constant or variable) energy deposition in the range of 1050-1051 ergs s-1 within a 30 deg cone around the rotation axis. The jet flow is strongly beamed (approximately less than a few degrees), spatially inhomogeneous, and time dependent. The jet reaches the surface of the stellar progenitor (R*=2.98x1010 cm) intact. At breakout, the maximum Lorentz factor of the jet flow is 33. After breakout, the jet accelerates into the circumstellar medium, whose density is assumed to decrease exponentially and then become constant, ?ext=10-5 g cm-3. Outside the star, the flow begins to expand laterally also (v~c), but the beam remains very well collimated. At a distance of 2.54 R*, where the simulation ends, the Lorentz factor has increased to 44.

  4. The Jets of Enceladus: Locations, Correlations with Thermal Hot Spots, and Jet Particle Vertical Velocities

    NASA Astrophysics Data System (ADS)

    Porco, C.; Ingersoll, A. P.; Dinino, D.; Helfenstein, P.; Roatsch, T.; Mitchell, C. J.; Ewald, S. P.

    2010-12-01

    High resolution images of Enceladus and its south polar jets taken with the Cassini ISS cameras in the last year have provided an opportunity for detailed study of the jetting phenomenon and its relationship to features and thermal hot spots on the moons south polar terrain. We have identified ~ 30 individual jets in a series of images, ranging from 43 to 100 m per pixel, taken in November 2009. All jets are found to be erupting through `tiger stripe fractures that cross the south polar terrain. The most intense jetting activity generally corresponds to the hottest regions on the fractures. One of the brightest, most prominent jets observed in this image series vents from a region on the Damascus Sulcus fracture that was imaged at 16 m/pixel during Cassinis August 13, 2010 flyby; it is also one of the hottest places found so far on the south polar region. Several jets were selected for dynamical modeling. These were jets whose source regions were on the limb as seen from Cassini, allowing extraction of brightness profiles down to a few hundred meters of the surface. We infer the velocity distribution of the particles as they leave the surface by modeling the integrated brightness vs. altitude. The particles are assumed to follow ballistic trajectories, and their contribution to the brightness in each thin layer is proportional to the time that they spend in the layer. We find slow jets, fast jets, and jets in between. After a rapid ~ 2-km-scale-height decrease near the surface, the most prominent jet (mentioned above) extends with constant integrated brightness to the edge of the image 25 km above the surface; some of the particles in this jet appear to have mean velocities that exceed the 235 m/sec escape speed from Enceladus. Further analysis of higher-altitude images from the November flyby is in progress to verify this result. The integrated brightness of slow jets falls off with a scale height of 5 km or less, implying mean vertical velocities of order 30 m/s or less, much less than either the escape speed or the thermal speed for a temperature of 273 K. From the collimation of the vapor in the jets, the Cassini UVIS team infers vertical velocities of 1000 m/s or more [Hansen et al. (2008) Nature 456, 477-479]. Schmidt et al. [(2008) Nature 451, 685-688] account for the slow particle speeds by invoking collisions with the walls of the vent. Ingersoll and Pankine [(2010) Icarus 206, 594-607] invoke short distances during which the gas velocity is high; the particles dont have time reach escape speed. The third possibility is that the particles are so large that the gas cannot accelerate them to escape speed. This possibility is testable with Cassini ISS high-resolution images, which span phase angles up to 176 degrees and wavelengths from UV to near-IR. Our ultimate goal is to test models of how the jets form. The particles form either by condensing directly from vapor, by spallation from the icy walls of the vent, or by freezing of liquid water droplets. Images collected by Cassini thus far will help us choose among the possibilities.

  5. Dynamics of Transient Liquid Injection

    NASA Astrophysics Data System (ADS)

    Sirignano, William

    2013-11-01

    Start-up transients and steady injection of liquid through round and annular orifices into ambient gas are examined. Various relevant hydrodynamic instabilities are examined together with their synergisms; capillary instability; vortex-ring (Widnall) instability; Kelvin-Helmholtz (i.e., shear-driven) instability; and Rayleigh-Taylor instability. Studies of both full jets and liquid segments of the jet are considered. Different instabilities and synergisms of instabilities produce different wavelengths on the jet interface. Surface waves, cone and sheet formations, and liquid-sheet tearing are examined. The breakdown of axisymmetry is related to the various instabilities. Accelerations of both the exit jet velocity and the liquid in the cones and ligaments are examined for Rayleigh-Taylor instabilities. Identification is sought of the length scales related to eventual breakup and droplet or ligament formation. Cavitation at high pressures is explained. Bubble growth and collapse in the internal orifice flow are discussed. Numerical problems with prediction of liquid stream breaking are discussed. Analysis and computations are emphasized but some experiments are discussed. Support from Army Research Office is acknowledged.

  6. Fake plunges are very eccentric real EMRIs in disguise. they dominate the rates and are blissfully ignorant of angular momentum barriers

    NASA Astrophysics Data System (ADS)

    Amaro-Seoane, P.; Sopuerta, C. F.; Brem, P.

    2012-12-01

    The capture of a compact object in a galactic nucleus by a massive black hole (MBH) is the best way to map space and time around it. Compact objects such as stellar black holes on a capture orbit with a very high eccentricity have been wrongly assumed to be lost for the system after an intense burst of radiation, which has been described as a "direct plunge". We prove that these very eccentric capture orbits spend actually a similar number of cycles in a LISA-like detector as those with lower eccentricities if the central MBH is spinning. Although the rates are higher for high-eccentricity EMRIs, the spin also enhances the rates of lower-eccentricity EMRIs. This last kind have received more attention because of the fact that high-eccentricity EMRIs were thought to be direct plunges and thus negligible. On the other hand, recent work on stellar dynamics has demonstrated that there seems to be a complot in phase space acting on these lower-eccentricity captures, since their rates decrease significantly by the presence of a blockade in the rate at which orbital angular momenta change takes place. This so-called "Schwarzschild barrier" is a result of the impact of relativistic precession on to the stellar potential torques, and thus it affects the enhancement on lower-eccentricity EMRIs that one would expect from resonant relaxation. We confirm and quantify the existence of this barrier using a statitical sample of 2,500 direct-summation N-body simulations using both a post-Newtonian but also, and for the first time, a geodesic approximation for thse relativistic orbits. The existence of the barrier prevents "traditional EMRIs" from approaching the central MBH, but if the central MBH is spinning the rate will be anyway dominated by highly-eccentric extreme-mass ratio inspirals, which insolently ignore the presence of the barrier, because they are driven by two-body relaxation.

  7. Sessile drop deformations under an impinging jet

    NASA Astrophysics Data System (ADS)

    Feng, James Q.

    2015-08-01

    The problem of steady axisymmetric deformations of a liquid sessile drop on a flat solid surface under an impinging gas jet is of interest for understanding the fundamental behavior of free surface flows as well as for establishing the theoretical basis in process design for the Aerosol direct-write technology. It is studied here numerically using a Galerkin finite-element method, by computing solutions of Navier-Stokes equations. For effective material deposition in Aerosol printing, the desired value of Reynolds number for the laminar gas jet is found to be greater than ~500. The sessile drop can be severely deformed by an impinging gas jet when the capillary number is approaching a critical value beyond which no steady axisymmetric free surface deformation can exist. Solution branches in a parameter space show turning points at the critical values of capillary number, which typically indicate the onset of free surface shape instability. By tracking solution branches around turning points with an arc-length continuation algorithm, critical values of capillary number can be accurately determined. Near turning points, all the free surface profiles in various parameter settings take a common shape with a dimple at the center and bulge near the contact line. An empirical formula for the critical capillary number for sessile drops with contact angle is derived for typical ranges of jet Reynolds number and relative drop sizes especially pertinent to Aerosol printing.

  8. Temporal instability analysis of inviscid compound jets falling under gravity

    NASA Astrophysics Data System (ADS)

    Mohsin, Muhammad; Uddin, Jamal; Decent, Stephen P.; Afzaal, Muhammad F.

    2013-01-01

    Compound liquid jets can be used in a variety of industrial applications ranging from capsule production in pharmaceutics to enhance printing methods in ink-jet printing. An appreciation of how instability along compound jets can lead to breakup and droplet formation is thus critical in many fields in science and engineering. In this paper, we perform a theoretical analysis to examine the instability of an axisymmetric inviscid compound liquid jet which falls vertically under the influence of gravity. We use a long-wavelength, slender-jet asymptotic expansion to reduce the governing equations of the problem into a set of one-dimensional partial differential equations, which describe the evolution of the leading-order axial velocity of the jet as well as the radii of both the inner and the outer interfaces. We first determine the steady-state solutions of the one-dimensional model equations and then we perform a linear temporal instability analysis to obtain a dispersion relation, which gives us useful information about the maximum growth rate and the maximum wavenumber of the imposed wave-like disturbance. We use our results to estimate the location and qualitative nature of breakup and then compare our results with numerical simulations.

  9. Method and apparatus for water jet drilling of rock

    DOEpatents

    Summers, David A.; Mazurkiewicz, Marian; Bushnell, Dwight J.; Blaine, James

    1978-01-01

    Rock drilling method and apparatus utilizing high pressure water jets for drilling holes of relatively small diameter at speeds significantly greater than that attainable with existing drilling tools. Greatly increased drilling rates are attained due to jet nozzle geometry and speed of rotation. The jet nozzle design has two orifices, one pointing axially ahead in the direction of travel and the second inclined at an angle of approximately 30.degree. from the axis. The two orifices have diameters in the ratio of approximately 1:2. Liquid jet velocities in excess of 1,000 ft/sec are used, and the nozzle is rotated at speeds up to 1,000 rpm and higher.

  10. Dynamic Characteristics at the Interface of Underwater Round Gas Jets

    NASA Astrophysics Data System (ADS)

    Weiland, Chris; Vlachos, Pavlos

    2009-11-01

    The gas-liquid interface characteristics of round gas-jets submerged in water was studied across a wide range of Mach numbers (0.4-1.9). High speed shadowphotography was used to image the gas jet and the interface was tracked from the digital images for all points in space and time. The results show how the interface characteristics are governed by buoyancy to momentum driven flow as the Mach number increases. The jet penetration, defined as the maximum length a continuous gas jet occupies 99 percent of the time, increases with the injection Mach number. The penetration is related to the compressible jetting length, defined as the distance from the orifice where the momentum and buoyancy forces are balanced, and signifies a change in the jet behavior spatially from a momentum to buoyancy driven flow. The interface motion is computed as a function of the Mach number and the distance downstream from the orifice. These results indicate the most unsteady jetting process near the orifice occurs at Mach 1, presumably due to the formation of a shock cell structures.

  11. Ram-jet Performance

    NASA Technical Reports Server (NTRS)

    Cervenko, A. J.; Friedman, R.

    1956-01-01

    The ram jet is basically one of the most dimple types of aircraft engine. It consists only of an inlet diffuser, a combustion system, and an exit nozzle. A typical ram-jet configuration is shown in figure 128. The engine operates on the Brayton cycle, and ideal cycle efficiency depends only on the ratio of engine to ambient pressure. The increased, engine pressures are obtained by ram action alone, and for this reason the ram jet has zero thrust at zero speed. Therefore, ram-jet-powered aircraft must be boosted to flight speeds close to a Mach number of 1.0 before appreciable thrust is generated by the engine. Since pressure increases are obtained by ram action alone, combustor-inlet pressures and temperatures are controlled by the flight speed, the ambient atmospheric condition, and by the efficiency of the inlet diffuser. These pressures and temperatures, as functions of flight speed and altitude, are shown in figure 129 for the NACA standard atmosphere and for practical values of diffuser efficiency. It can be seen that very wide ranges of combustor-inlet temperatures and pressures may be encountered over the ranges of flight velocity and altitude at which ram jets may be operated. Combustor-inlet temperatures from 500 degrees to 1500 degrees R and inlet pressures from 5 to 100 pounds per square inch absolute represent the approximate ranges of interest in current combustor development work. Since the ram jet has no moving parts in the combustor outlet, higher exhaust-gas temperatures than those used in current turbojets are permissible. Therefore, fuel-air ratios equivalent to maximum rates of air specific impulse or heat release can be used, and, for hydrocarbon fuels, this weight ratio is about 0.070. Lower fuel-air ratios down to about 0.015 may also be required to permit efficient cruise operation. This fuel-air-ratio range of 0.015 to 0.070 used in ram jets can be compared with the fuel-air ratios up to 0.025 encountered in current turbojets. Ram-jet combustor-inlet velocities range from 150 to 400 feet per second. These high linear velocities combined with the relatively low pressure ratios obtainable in ram jets require that the pressure drop through the combustor be kept low to avoid excessive losses in cycle efficiency. It has been estimated that, for a long-range ram-jet engine, an increase in pressure loss of one dynamic head would require a compensating 1-percent increase in combustion efficiency. Therefore, combustor pressure-loss coefficients (pressure drop/impact pressure) of the order of 1 to 4 are found in most current engines. The operating conditions described impose major problems in the design of stable and efficient ram-jet combustion systems. This chapter presents a survey of ram-jet combustor research and, where possible, points out criteria that may be useful in the design of ram-jet combustion systems.

  12. Impulsively started incompressible turbulent jet

    SciTech Connect

    Witze, P O

    1980-10-01

    Hot-film anemometer measurements are presented for the centerline velocity of a suddenly started jet of air. The tip penetration of the jet is shown to be proportional to the square-root of time. A theoretical model is developed that assumes the transient jet can be characterized as a spherical vortex interacting with a steady-state jet. The model demonstrates that the ratio of nozzle radius to jet velocity defines a time constant that uniquely characterizes the behavior and similarity of impulsively started incompressible turbulent jets.

  13. Thermal ink jet: a review

    NASA Astrophysics Data System (ADS)

    Rezanka, Ivan

    1992-05-01

    The first public demonstration of thermal ink jet printing was done by Canon in 1981 and the first thermal ink jet product, ThinkJet, was introduced by the Hewlett-Packard Company in 1984. Since then, this powerful printing technology has assumed a strong presence in the market. In this discussion, we will first briefly review the printer market, the increasing role thermal ink jet is playing in this arena, as well as the reasons for its success. The technology discussion will follow, and will focus on several highlights in thermal ink jet physics, materials, and printing. We will conclude with our comments on future thermal ink jet developments.

  14. Integrated coke, asphalt and jet fuel production process and apparatus

    DOEpatents

    Shang, Jer Y. (McLean, VA)

    1991-01-01

    A process and apparatus for the production of coke, asphalt and jet fuel m a feed of fossil fuels containing volatile carbon compounds therein is disclosed. The process includes the steps of pyrolyzing the feed in an entrained bed pyrolyzing means, separating the volatile pyrolysis products from the solid pyrolysis products removing at least one coke from the solid pyrolysis products, fractionating the volatile pyrolysis products to produce an overhead stream and a bottom stream which is useful as asphalt for road pavement, condensing the overhead stream to produce a condensed liquid fraction and a noncondensable, gaseous fraction, and removing water from the condensed liquid fraction to produce a jet fuel-containing product. The disclosed apparatus is useful for practicing the foregoing process. the process provides a useful method of mass producing and jet fuels from materials such as coal, oil shale and tar sands.

  15. Jet propulsion without inertia

    NASA Astrophysics Data System (ADS)

    Spagnolie, Saverio E.; Lauga, Eric

    2010-08-01

    A body immersed in a highly viscous fluid can locomote by drawing in and expelling fluid through pores at its surface. We consider this mechanism of jet propulsion without inertia in the case of spheroidal bodies and derive both the swimming velocity and the hydrodynamic efficiency. Elementary examples are presented and exact axisymmetric solutions for spherical, prolate spheroidal, and oblate spheroidal body shapes are provided. In each case, entirely and partially porous (i.e., jetting) surfaces are considered and the optimal jetting flow profiles at the surface for maximizing the hydrodynamic efficiency are determined computationally. The maximal efficiency which may be achieved by a sphere using such jet propulsion is 12.5%, a significant improvement upon traditional flagella-based means of locomotion at zero Reynolds number, which corresponds to the potential flow created by a source dipole at the sphere center. Unlike other swimming mechanisms which rely on the presentation of a small cross section in the direction of motion, the efficiency of a jetting body at low Reynolds number increases as the body becomes more oblate and limits to approximately 162% in the case of a flat plate swimming along its axis of symmetry. Our results are discussed in the light of slime extrusion mechanisms occurring in many cyanobacteria.

  16. The Cape Tobin Jet

    NASA Astrophysics Data System (ADS)

    lafsson, H.; Shapiro, M. A.; gstsson, H.; Kristjnsson, J. E.

    2009-04-01

    In northerly flow, a strong jet close to Cape Tobin in E-Greenland is frequently simulated in numerical weather prediction models. To the extent that the late-summer absence of sea-ice permits, Quik-SCAT observations confirm the presence of this jet. During the IPY/THORPEX and GREENEX campaigns in March 2008, observations were made of the Cape Tobin jet with a number of dropsondes. The core of the jet with maximum wind speed of about 45 m/s was located at a strong inversion at about 1 km above the sea ice. The inversion slopes and is at a lower level away from Greenland than closer to the coast. A part of the Tobin jet impinges on the more than 2 km high topography of E-Greenland and flows over it in spite of high static stability. The associated mixing leads to cooling of the layers between 1 and 2 km and the downstream flow at these levels may be characterized as "cold foehn".

  17. Jet penetration in glass

    SciTech Connect

    Moran, B.; Glenn, L.A.; Kusubov, A.

    1991-05-01

    We describe a phenomenological model which accounts for the mechanical response of glass to intense impulsive loading. An important aspect of this response is the dilatancy accompanying fracture. We have also conducted a number of experiments with 38.1-mm diameter precision shaped charges to establish the performance against various targets and to allow evaluation of our model. At 3 charge diameters standoff, the data indicate that both virgin and damaged glass offer better (Bernoulli-scaled) resistance to penetration than either of 4340 steel, or 6061-T6 aluminum alloy. Time-resolved measurements indicate two distinct phases of jet penetration in glass: An initial hydrodynamic phase, and a second phase characterized by a slower penetration velocity. Our calculations show that at early time, a crater is formed around the jet and only the tip of the undisturbed jet interacts with the glass. At late time the glass has collapsed on the jet and degraded penetration continues via a disturbed and fragmented jet.

  18. Nonaxisymmetric Poynting jets

    NASA Astrophysics Data System (ADS)

    Gralla, Samuel E.; Jacobson, Ted

    2015-08-01

    The relativistic plasma jets from a misaligned black hole-accretion disk system will not be axially symmetric. Here we analyze nonaxisymmetric, stationary, translation invariant jets in the force-free approximation where the field energy dominates the particle energy. We derive a stream equation for these configurations involving the flux function ψ for the transverse magnetic field, the linear velocity v (ψ ) of field lines along the jet, and the longitudinal magnetic field Bz(ψ ). The equations can be completely solved when |v |=1 , and when |v |<1 the problem can be reduced to the pure magnetic case v =0 by a "field line dependent boost." We also find a large class of nonaxisymmetric solutions with arbitrary dependence on the longitudinal retarded time. A subclass of these constitutes a novel type of jet that has vanishing electromagnetic pressure 1/2 (B2-E2) and requires no external pressure for confinement. We prove that such self-confinement is impossible when B2>E2. Finally, we write down specific solutions approximating numerical results for the nonaxisymmetric jet produced by a spinning black hole in an external, misaligned magnetic field.

  19. The Twin Jet Nebula

    NASA Technical Reports Server (NTRS)

    1997-01-01

    M2-9 is a striking example of a 'butterfly' or a bipolar planetary nebula. Another more revealing name might be the 'Twin Jet Nebula.' If the nebula is sliced across the star, each side of it appears much like a pair of exhausts from jet engines. Indeed, because of the nebula's shape and the measured velocity of the gas, in excess of 200 miles per second, astronomers believe that the description as a super-super-sonic jet exhaust is quite apt. This is much the same process that takes place in a jet engine: The burning and expanding gases are deflected by the engine walls through a nozzle to form long, collimated jets of hot air at high speeds. M2-9 is 2,100 light-years away in the constellation Ophiucus. The observation was taken Aug. 2, 1997 by the Hubble telescope's Wide Field and Planetary Camera 2. In this image, neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue.

  20. B-jets and z + b-jets at CDF

    SciTech Connect

    Jeans, Daniel; /Rome U.

    2006-06-01

    The authors present CDF cross-section measurements for the inclusive production of b jets and the production of b jets in association with a Z{sup 0} boson. Both measurements are in reasonable agreement with NLO QCD predictions.