Multiple zonal jets and convective heat transport barriers in a quasi-geostrophic model of planetary cores

NASA Astrophysics Data System (ADS)

Guervilly, C.; Cardin, P.

2017-10-01

We study rapidly rotating Boussinesq convection driven by internal heating in a full sphere. We use a numerical model based on the quasi-geostrophic approximation for the velocity field, whereas the temperature field is 3-D. This approximation allows us to perform simulations for Ekman numbers down to 10-8, Prandtl numbers relevant for liquid metals (˜10-1) and Reynolds numbers up to 3 × 104. Persistent zonal flows composed of multiple jets form as a result of the mixing of potential vorticity. For the largest Rayleigh numbers computed, the zonal velocity is larger than the convective velocity despite the presence of boundary friction. The convective structures and the zonal jets widen when the thermal forcing increases. Prograde and retrograde zonal jets are dynamically different: in the prograde jets (which correspond to weak potential vorticity gradients) the convection transports heat efficiently and the mean temperature tends to be homogenized; by contrast, in the cores of the retrograde jets (which correspond to steep gradients of potential vorticity) the dynamics is dominated by the propagation of Rossby waves, resulting in the formation of steep mean temperature gradients and the dominance of conduction in the heat transfer process. Consequently, in quasi-geostrophic systems, the width of the retrograde zonal jets controls the efficiency of the heat transfer.

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.

Mechanism of ultrasonic energy-assisted formation of V-, Y-shaped nano-structures in conjugated polymers.

PubMed

Majumdar, D; Maiti, R P; Basu, S; Saha, S K

2009-12-01

Recently, hydrocarbon-nanostructures from organic solvent using ultrasonic energy were reported. However, their formation-dynamics remained unexplored. Here, we describe a new technique to synthesize controlled nanostructures (V-, Y-shape) from nanorods of conducting polyaniline applying ultrasonic energy. To characterize the conducting state (emaraldine) of these polyaniline nanorods, electrical measurements have been carried out from which it is seen that there is a crossover from metallic to semiconductor as temperature increases. The observed crossover has been explained by the core-shell structure of the nanorods with core resistivity much higher than the shell resistivity. The nonlinear current-voltage behavior is attributed to the formation of alternate ordered/disordered chain segments along the length of the nanorods. We also propose a model to explore the mechanism of formation of these V-, Y-shaped nanostructures. It is believed that bubble-formation occurs in liquid due to ultrasonic vibration; and asymmetry in the bubble is created when formed near the solid surface leading to jet formation. Liquid jets of collapsing bubble move with incredible velocity (400 km/h); collide with the nanorod to cause fragmentations followed by V-, Y-shaped structure formation when the imparted kinetic energy of jets is comparable with elastic energy of fragments.

Microencapsulation of curcumin in PLGA microcapsules by coaxial flow focusing

NASA Astrophysics Data System (ADS)

Lei, Fan; Si, Ting; Luo, Xisheng; Xu, Ronald X.

2014-03-01

Curcumin-loaded PLGA microcapsules are fabricated by a liquid-driving coaxial flow focusing device. In the process, a stable coaxial cone-jet configuration is formed under the action of a coflowing liquid stream and the coaxial liquid jet eventually breaks up into microcapsules because of flow instability. This process can be well controlled by adjusting the flow rates of three phases including the driving PVA water solution, the outer PLGA ethyl acetate solution and the inner curcumin propylene glycol solution. Confocal and SEM imaging methods clearly indicate the core-shell structure of the resultant microcapsules. The encapsulation rate of curcumin in PLGA is measured to be more than 70%, which is much higher than the tranditional methods such as emulsion. The size distribution of resultant microcapsules under different conditions is presented and compared. An in vitro release simulation platform is further developed to verify the feasibility and reliability of the method.

Deformation and Breakup of Two Fluid Jets

NASA Astrophysics Data System (ADS)

Doshi, Pankaj; Ramkrishna, Doraiswamy; Basaran, Osman

2001-11-01

Two fluid jets consists of an inner liquid core surrounded by an annulus of outer immiscible liquid. The perturbation in the inner and outer interphase could cause capillary instability resulting in large deformation and breakup of the jet into drops. The jet breakup and drop size distribution is largely influenced by the properties of inner and outer fluid phases. Out of the various jet breakup phenomena one with most technological importance is the one in which inner interphase ruptures followed by the outer interphase resulting in the formation of compound drops. The compound drop formation is very useful for the microencapsulation technology, which find use in diverse pharmaceutical and chemical industry applications. In this paper we present a computational analysis of non-linear deformation and breakup of two fluid jets of Newtonian fluids. The analysis involves study of capillary instability driven deformation of a free jet with periodic boundary conditions. Although small amplitude deformation of two fluid jets have previously been studied, large amplitude deformation exhibiting interesting nonlinear dynamics and eventual breakup of the two fluid jets have been beyond the reach of previously used analytical and computational techniques. The computational difficulties result from the facts that (1) the inner and outer interphase can overturn during the motion and (2) pressure and normal stress are discontinuous at the inner interphase. We overcome both of these difficulties by using a new Galerkin/finite element algorithm that relies on a powerful elliptic mesh generation technique. The results to be presented includes jet deformation and breakup time as a function of inner and outer fluid phase properties. The highlight of the results will be prediction of drop size distribution which is of critical importance for microencapsulation technology.

Production of microbubbles from axisymmetric flow focusing in the jetting regime for moderate Reynolds numbers.

PubMed

Vega, E J; Acero, A J; Montanero, J M; Herrada, M A; Gañán-Calvo, A M

2014-06-01

We analyze both experimentally and numerically the formation of microbubbles in the jetting regime reached when a moderately viscous liquid stream focuses a gaseous meniscus inside a converging micronozzle. If the total (stagnation) pressure of the injected gas current is fixed upstream, then there are certain conditions on which a quasisteady gas meniscus forms. The meniscus tip is sharpened by the liquid stream down to the gas molecular scale. On the other side, monodisperse collections of microbubbles can be steadily produced in the jetting regime if the feeding capillary is appropriately located inside the nozzle. In this case, the microbubble size depends on the feeding capillary position. The numerical simulations for an imposed gas flow rate show that a recirculation cell appears in the gaseous meniscus for low enough values of that parameter. The experiments allow one to conclude that the bubble pinch-off comprises two phases: (i) a stretching motion of the precursor jet where the neck radius versus the time before the pinch essentially follows a potential law, and (ii) a final stage where a very thin and slender gaseous thread forms and eventually breaks apart into a number of micron-sized bubbles. Because of the difference between the free surface and core velocities, the gaseous jet breakage differs substantially from that of liquid capillary jets and gives rise to bubbles with diameters much larger than those expected from the Rayleigh-type capillary instability. The dependency of the bubble diameter upon the flow-rate ratio agrees with the scaling law derived by A. M. Gañán-Calvo [Phys. Rev. E 69, 027301 (2004)], although a slight influence of the Reynolds number can be observed in our experiments.

One-step production of multilayered microparticles by tri-axial electro-flow focusing

NASA Astrophysics Data System (ADS)

Si, Ting; Feng, Hanxin; Li, Yang; Luo, Xisheng; Xu, Ronald

2014-03-01

Microencapsulation of drugs and imaging agents in the same carrier is of great significance for simultaneous detection and treatment of diseases. In this work, we have developed a tri-axial electro-flow focusing (TEFF) device using three needles with a novel concentric arrangement to one-step form multilayered microparticles. The TEFF process can be characterized as a multi-fluidic compound cone-jet configuration in the core of a high-speed coflowing gas stream under an axial electric field. The tri-axial liquid jet eventually breaks up into multilayered droplets. To validate the method, the effect of main process parameters on characteristics of the cone and the jet has been studied experimentally. The applied electric field can dramatically promote the stability of the compound cone and enhance the atomization of compound liquid jets. Microparticles with both three-layer, double-layer and single-layer structures have been obtained. The results show that the TEFF technique has great benefits in fabricating multilayered microparticles at smaller scales. This method will be able to one-step encapsulate multiple therapeutic and imaging agents for biomedical applications such as multi-modal imaging, drug delivery and biomedicine.

Analysis of stratified and closely spaced jets exhausting into a crossflow. [aerodynamic characteristics of lift-jet, vectored thrust, and lift fan V/STOL aircraft

NASA Technical Reports Server (NTRS)

Ziegler, H.; Woller, P. T.

1973-01-01

Procedures have been developed for determining the flow field about jets with velocity stratification exhausting into a crossflow. Jets with three different types of exit velocity stratification have been considered: (1) jets with a relatively high velocity core; (2) jets with a relatively low velocity core; and (3) jets originating from a vaned nozzle. The procedure developed for a jet originating from a high velocity core nozzle is to construct an equivalent nozzle having the same mass flow and thrust but having a uniform exit velocity profile. Calculations of the jet centerline and induced surface static pressures have been shown to be in good agreement with test data for a high velocity core nozzle. The equivalent ideal nozzle has also been shown to be a good representation for jets with a relatively low velocity core and for jets originating from a vaned nozzle in evaluating jet-induced flow fields. For the singular case of a low velocity core nozzle, namely a nozzle with a dead air core, and for the vaned nozzle, an alternative procedure has been developed. The internal mixing which takes place in the jet core has been properly accounted for in the equations of motion governing the jet development. Calculations of jet centerlines and induced surface static pressures show good agreement with test data these nozzles.

Particle separating apparatus and method

DOEpatents

Van den Engh, Gerrit J.

1998-01-01

A disposable first tube (68) extends axially through, and is detachably connected to, an annular main body (10'). An input piezo electric element (38) is attached to a first end of the tubular main body (10'). A second, sensor piezo electric element (40) is attached to the opposite end of the main body (10'). A nozzle (20') having a nozzle passageway (110) and a discharge opening (112) is detachably secured to an outlet end of the first tube (68). A second tube (102) within the first tube (68) delivers a core liquid to the nozzle passageway (110). A sheath liquid is delivered through a space in the first tube (68) surrounding the second tube (102). The nozzle passageway (110) forms the core and sheath liquids into a small diameter jet stream. Electrical energy is delivered to the input piezo electric element (38), to vibrate the nozzle (20') and break the jet stream into droplets. The sensor element (40) determines the amplitude of vibration at the nozzle (20') and delivers this information to a control circuit that adjusts the electrical energy input to the input piezo electric element (38) for maintaining a desired amplitude of vibration at the nozzle (20'). The frequency of vibration is determined by the length of the main body (10') between the two piezo electric elements (38, 40). The first and second tubes (68, 102) are disposable and are replaced after a use rather than being cleaned and sterilized.

Particle separating apparatus and method

DOEpatents

Van den Engh, Gerrit J.

1999-01-01

A disposable first tube (68) extends axially through, and is detachably connected to, an annular main body (10'). An input piezo electric element (38) is attached to a first end of the tubular main body (10'). A second, sensor piezo electric element (40) is attached to the opposite end of the main body (10'). A nozzle (20') having a nozzle passageway (110) and a discharge opening (112) is detachably secured to an outlet end of the first tube (68). A second tube (102) within the first tube (68) delivers a core liquid to the nozzle passageway (110). A sheath liquid is delivered through a space in the first tube (68) surrounding the second tube (102). The nozzle passageway (110) forms the core and sheath liquids into a small diameter jet stream. Electrical energy is delivered to the input piezo electric element (38), to vibrate the nozzle (20') and break the jet stream into droplets. The sensor element (40) determines the amplitude of vibration at the nozzle (20') and delivers this information to a control circuit that adjusts the electrical energy input to the input piezo electric element (38) for maintaining a desired amplitude of vibration at the nozzle (20'). The frequency of vibration is determined by the length of the main body (10') between the two piezo electric elements (38, 40). The first and second tubes (68, 102) are disposable and are replaced after a use rather than being cleaned and sterilized.

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.

Initial instability of round liquid jet at subcritical and supercritical environments

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

Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in

2016-07-15

In the present experimental work, the behavior of laminar liquid jet in its own vapor as well as supercritical fluid environment is conducted. Also the study of liquid jet injection into nitrogen (N{sub 2}) environment is carried out at supercritical conditions. It is expected that the injected liquid jet would undergo thermodynamic transition to the chamber condition and this would alter the behavior of the injected jet. Moreover at such conditions there is a strong dependence between thermodynamic and fluid dynamic processes. Thus the thermodynamic transition has its effect on the initial instability as well as the breakup nature ofmore » the injected liquid jet. In the present study, the interfacial disturbance wavelength, breakup characteristics, and mixing behavior are analysed for the fluoroketone liquid jet that is injected into N{sub 2} environment as well as into its own vapor at subcritical to supercritical conditions. It is observed that at subcritical chamber conditions, the injected liquid jet exhibits classical liquid jet characteristics with Rayleigh breakup at lower Weber number and Taylor breakup at higher Weber number for both N{sub 2} and its own environment. At supercritical chamber conditions with its own environment, the injected liquid jet undergoes sudden thermodynamic transition to chamber conditions and single phase mixing characteristics is observed. However, the supercritical chamber conditions with N{sub 2} as ambient fluid does not have significant effect on the thermodynamic transition of the injected liquid jet.« less

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.

A PIV Study of Slotted Air Injection for Jet Noise Reduction

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Wernet, Mark P.

2012-01-01

Results from acoustic and Particle Image Velocimetry (PIV) measurements are presented for single and dual-stream jets with fluidic injection on the core stream. The fluidic injection nozzles delivered air to the jet through slots on the interior of the nozzle at the nozzle trailing edge. The investigations include subsonic and supersonic jet conditions. Reductions in broadband shock noise and low frequency mixing noise were obtained with the introduction of fluidic injection on single stream jets. Fluidic injection was found to eliminate shock cells, increase jet mixing, and reduce turbulent kinetic energy levels near the end of the potential core. For dual-stream subsonic jets, the introduction of fluidic injection reduced low frequency noise in the peak jet noise direction and enhanced jet mixing. For dual-stream jets with supersonic fan streams and subsonic core streams, the introduction of fluidic injection in the core stream impacted the jet shock cell structure but had little effect on mixing between the core and fan streams.

Coaxial gas-liquid jet: Dispersion and dynamics

NASA Astrophysics Data System (ADS)

Poplavski, S. V.; Boiko, V. M.; Lotov, V. V.; Nesterov, A. Yu.

2018-03-01

The aim of the work was to study the pneumatic spraying of liquids in a gas jet with reference to the creation of high-flow nozzles. A complex experimental study of a coaxial jet was performed with a central supply of liquid beyond the cutoff of the confusor nozzle at subsonic and supersonic flow conditions. A set of optical methods for flows diagnostics that can function in dense gas-liquid jets provides new data on the structure of the spray: the gas velocity field without liquid, shadow visualization of the geometry and wave structure of the jet with and without fluid, the velocity profiles of the liquid phase, size distribution of the droplets. The key parameters of the liquid breakup processes for the We numbers are obtained. A dynamic approach to the determination of average droplet sizes is considered. A physical model of a coaxial gas-liquid jet with a central fluid supply is proposed.

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.

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.

Coupling modes between liquid/gas coaxial jets and transverse acoustic waves

NASA Astrophysics Data System (ADS)

Helland, Chad; Hilliker, Cullen; Forliti, David; University of St. Thomas Team

2017-11-01

The interactions between shear flows and acoustic disturbances plays a very important role in many propulsion and energy applications. Liquid jets, either independent or air assisted, respond to acoustic disturbances in a manner that alters the primary and secondary atomization processes. The current study focused on the response of an air-assisted liquid jet to disturbances associated with a transverse acoustic wave. The jet is placed in the pressure node (velocity antinode) region of the resonant mode shape. It has been shown in previous studies, under certain conditions, that the acoustic forces can cause the jet flow to distort and atomize. Both liquid and coaxial gas/ liquid jet flows have been shown to distort via acoustic forces. The purpose of the current study is to understand the predictive characteristics that cause the distortion behaviors of a liquid and coaxial jet flow, and how a how a coaxial flow affects the behavior.

On the Surface Breakup of a Non-turbulent Round Liquid Jet in Cross-flow

NASA Astrophysics Data System (ADS)

Behzad, Mohsen; Ashgriz, Nasser

2011-11-01

The atomization of a non-turbulent liquid jet injected into a subsonic cross-flow consists of two parts: (1) primary breakup and (2) secondary breakup. Two distinct regimes for the liquid jet primary breakup have been recognized; the so called column breakup and surface breakup. In the column breakup mode, the entire liquid jet undergoes disintegration into large liquid lumps. Quiet differently in the surface breakup regime, liquid fragments with various sizes and shapes are separated from the surface of the jet. Despite many experimental studies the mechanisms of jet surface breakup is not fully understood. Thus this study aims at providing useful observations regarding the underlying physics involving the surface breakup mechanism of a liquid jet in cross-flow, using detailed numerical simulations. The results show that a two-stage mechanism can be responsible for surface breakup. In the first stage, a sheet-like structure extrudes towards the downstream, and in the second stage it disintegrates into ligaments and droplets due to aerodynamic instability.

On the dispersion of liquid in coaxial supersonic gas jet

NASA Astrophysics Data System (ADS)

Poplavski, S. V.; Boiko, V. M.; Lotov, V. V.; Nesterov, A. U.

2017-10-01

The aim of this work was to study the dispersion of liquids in gas jets in connection with the creation of high productivity nozzles. For effective combustion of fuel, systems with intensive air supply to the spray of a liquid are promising. In connection with this, a supersonic coaxial jet was experimentally studied with a central supply of liquid beyond the slit of the confuser nozzle at the modes Npr = 4 and Npr = 6. New data are obtained on the structure of the gas-liquid jet: the gas velocity field, the shadow visualization of the geometry and wave structure of the jet with and without liquid, the velocity profiles of the liquid phase, the dispersion of the droplets. The spatial distribution of the concentration of the spray was first determined. From these data, the parameters of the dispersion processes are obtained in terms the We numbers. A physical model of a supersonic coaxial gas-liquid jet with a central fluid supply is proposed.

Stable Liquid Jets Bouncing off Soft Gels

NASA Astrophysics Data System (ADS)

Daniel, Dan; Yao, Xi; Aizenberg, Joanna

2018-01-01

A liquid jet can stably bounce off a sufficiently soft gel by following the contour of the dimple created upon impact. This new phenomenon is insensitive to the wetting properties of the gels and was observed for different liquids over a wide range of surface tensions, γ =24 -72 mN /m . In contrast, other jet rebound phenomena are typically sensitive to γ : only a high γ jet rebounds off a hard solid (e.g. superhydrophobic surface) and only a low γ jet bounces off a liquid bath. This is because an air layer must be stabilized between the two interfaces. For a soft gel, no air layer is necessary and the jet rebound remains stable even when there is direct liquid-gel contact.

Influence of spatial curvature of a liquid jet on the rainbow positions: Ray tracing and experimental study

NASA Astrophysics Data System (ADS)

Duan, Qingwei; Zhong, Ruliang; Han, Xiang'e.; Ren, Kuan Fang

2017-07-01

Rainbow refractometry is largely used in optical metrology of particles thanks to its advantages of being non-intrusive, precise and fast. Many authors have contributed to its development and the application in the characterization of liquid jets/droplets. The researches reported in the literature are mainly for the spherical droplets or the liquid jets which can be considered as a cylinder of constant section. However, the section of a real liquid jet, even in the simplest configuration, varies with distance from the exit. The influence of the spatial curvature of the jets must, therefore, be taken into account. In this paper, we report experimental measurements of the shifts of the rainbow positions in the horizontal and vertical directions of a liquid jet and the theoretical investigation with the vectorial complex ray model. It is shown that the shifts of rainbow positions are very sensitive to the spatial curvature of the jets. This work is hoped to provide a new approach to characterizing the structure and the instability of liquid jets.

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.

An Experimental Study of Characteristic Combustion-Driven Flow for CFD Validation

NASA Technical Reports Server (NTRS)

Santoro, Robert J.

1997-01-01

A series of uni-element rocket injector studies were completed to provide benchmark quality data needed to validate computational fluid dynamic models. A shear coaxial injector geometry was selected as the primary injector for study using gaseous hydrogen/oxygen and gaseous hydrogen/liquid oxygen propellants. Emphasis was placed on the use of nonintrusive diagnostic techniques to characterize the flowfields inside an optically-accessible rocket chamber. Measurements of the velocity and species fields were obtained using laser velocimetry and Raman spectroscopy, respectively. Qualitative flame shape information was also obtained using laser-induced fluorescence excited from OH radicals and laser light scattering studies of aluminum oxide particle seeded combusting flows. The gaseous hydrogen/liquid oxygen propellant studies for the shear coaxial injector focused on breakup mechanisms associated with the liquid oxygen jet under subcritical pressure conditions. Laser sheet illumination techniques were used to visualize the core region of the jet and a Phase Doppler Particle Analyzer was utilized for drop velocity, size and size distribution characterization. The results of these studies indicated that the shear coaxial geometry configuration was a relatively poor injector in terms of mixing. The oxygen core was observed to extend well downstream of the injector and a significant fraction of the mixing occurred in the near nozzle region where measurements were not possible to obtain. Detailed velocity and species measurements were obtained to allow CFD model validation and this set of benchmark data represents the most comprehensive data set available to date. As an extension of the investigation, a series of gas/gas injector studies were conducted in support of the X-33 Reusable Launch Vehicle program. A Gas/Gas Injector Technology team was formed consisting of the Marshall Space Flight Center, the NASA Lewis Research Center, Rocketdyne and Penn State. Injector geometries studied under this task included shear and swirl coaxial configurations as well as an impinging jet injector.

An Experimental Study of Characteristic Combustion-Driven Flow for CFD Validation

NASA Technical Reports Server (NTRS)

Santoro, Robert J.

1997-01-01

A series of uni-element rocket injector studies were completed to provide benchmark quality data needed to validate computational fluid dynamic models. A shear coaxial injector geometry was selected as the primary injector for study using gaseous hydrogen/oxygen and gaseous hydrogen/liquid oxygen propellants. Emphasis was placed on the use of non-intrusive diagnostic techniques to characterize the flowfields inside an optically-accessible rocket chamber. Measurements of the velocity and species fields were obtained using laser velocimetry and Raman spectroscopy, respectively Qualitative flame shape information was also obtained using laser-induced fluorescence excited from OH radicals and laser light scattering studies of aluminum oxide particle seeded combusting flows. The gaseous hydrogen/liquid oxygen propellant studies for the shear coaxial injector focused on breakup mechanisms associated with the liquid oxygen jet under sub-critical pressure conditions. Laser sheet illumination techniques were used to visualize the core region of the jet and a Phase Doppler Particle Analyzer was utilized for drop velocity, size and size distribution characterization. The results of these studies indicated that the shear coaxial geometry configuration was a relatively poor injector in terms of mixing. The oxygen core was observed to extend well downstream of the injector and a significant fraction of the mixing occurred in the near nozzle region where measurements were not possible to obtain Detailed velocity and species measurements were obtained to allow CFD model validation and this set of benchmark data represents the most comprehensive data set available to date As an extension of the investigation, a series of gas/gas injector studies were conducted in support of the X-33 Reusable Launch Vehicle program. A Gas/Gas Injector Technology team was formed consisting of the Marshall Space Flight Center, the NASA Lewis Research Center, Rocketdyne and Penn State. Injector geometries studied under this task included shear and swirl coaxial configurations as well as an impinging jet injector.

Separation Of Liquid And Gas In Zero Gravity

NASA Technical Reports Server (NTRS)

Howard, Frank S.; Fraser, Wilson S.

1991-01-01

Pair of reports describe scheme for separating liquid from gas so liquid could be pumped. Designed to operate in absence of gravitation. Jet of liquid, gas, or liquid/gas mixture fed circumferentially into cylindrical tank filled with liquid/gas mixture. Jet starts liquid swirling. Swirling motion centrifugally separates liquid from gas. Liquid then pumped from tank at point approximately diametrically opposite point of injection of jet. Vortex phase separator replaces such devices as bladders and screens. Requires no components inside tank. Pumps for gas and liquid outside tank and easily accessible for maintenance and repairs.

Liquid atomization in supersonic flows

NASA Astrophysics Data System (ADS)

Missoum, Azzedine

An experimental investigation of the atomization of a round liquid jet by coaxial, costream injection into a supersonic, Mach 1.5 air flow is reported. Extensive flow visualization was conducted using schlieren/shadowgraph, flash photography, and short duration (ns) laser imaging. The finer details of the jet were revealed when viewed under high magnification with the help of a microscope. The liquid and air pressures were varied individually. Photographic evidence indicates the presence of three regions within the liquid jet: a primary region enclosed by the first shock cell where the primary breakup occurs, a secondary region in which the jet is totally broken because of its interaction with the supersonic wave structure, and a third, subsonic region further downstream. It was found that the breakup mechanism of liquid jets in supersonic airstreams is quite complex. The breakup seems to be initiated by the growth of the turbulent structure on the liquid surface and the subsequent detachment of the three-dimensional structure as fine droplets by the intense shear at the liquid-gas interface. This seems to confirm the boundary layer stripping mechanism. The liquid jet expands into a bubble like formation as it interacts with the first set of waves. Higher liquid injection pressures resulted in higher initial spray angles. The liquid jet displayed a geometry strongly dependent on the pressure distribution resulting from the wave structure present in the supersonic jet. Droplet size and velocity distributions were measured by the P/DPA (Phase/Doppler Particle Analyzer) system. The Sauter Mean Diameter (SMD) was measured at several axial and radial locations at various liquid and air pressures. The SMD shows a decrease with increase in both the air-to-liquid mass flow ratio and the Weber number. The drop size decreased towards the outer edges of the jet. The results lead one to conclude that the coaxial, coflowing configuration is very attractive for atomizing scramjet liquid fuels.

Swirl effect on flow structure and mixing in a turbulent jet

NASA Astrophysics Data System (ADS)

Kravtsov, Z. D.; Sharaborin, D. K.; Dulin, V. M.

2018-03-01

The paper reports on experimental study of turbulent transport in the initial region of swirling turbulent jets. The particle image velocimetry and planar laser-induced fluorescence techniques are used to investigate the flow structure and passive scalar concentration, respectively, in free air jet with acetone vapor. Three flow cases are considered, viz., non-swirling jets and swirling jets with and without vortex breakdown and central recirculation zone. Without vortex breakdown, the swirl is shown to promote jet mixing with surrounding air and to decrease the jet core length. The vortex core breakdown further enhances mixing as the jet core disintegrates at the nozzle exit.

Rich phenomenology encountered when two jets collide in microgravity

NASA Astrophysics Data System (ADS)

Suñol, 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.

Liquid Spray Characterization in Flow Fields with Centripetal Acceleration

DTIC Science & Technology

2014-03-27

25 2.4.1 Atomization of Liquid Jets ...volumetric heat release rates, easier light-up, wider burning range, and lower exhaust pollutant emissions [11]. 26 2.4.1 Atomization of Liquid Jets ...Atomization involves the interaction of consolidating and disruptive forces acting on a jet of liquid . The process of atomization can be further

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 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 μm. However, few studies have been devoted to small bubbles (R<100 μm) 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

Comparative analysis of core heat transport of JET high density H-mode plasmas in carbon wall and ITER-like wall

NASA Astrophysics Data System (ADS)

Kim, Hyun-Tae; Romanelli, M.; Voitsekhovitch, I.; Koskela, T.; Conboy, J.; Giroud, C.; Maddison, G.; Joffrin, E.; contributors, JET

2015-06-01

A consistent deterioration of global confinement in H-mode experiments has been observed in JET [1] following the replacement of all carbon plasma facing components (PFCs) with an all metal (‘ITER-like’) wall (ILW). This has been correlated to the observed degradation of the pedestal confinement, as lower electron temperature (Te) values are routinely measured at the top of the edge barrier region. A comparative investigation of core heat transport in JET-ILW and JET-CW (carbon wall) discharges has been performed, to assess whether core confinement has also been affected by the wall change. The results presented here have been obtained by analysing a set of discharges consisting of high density JET-ILW H-mode plasmas and comparing them against their counterpart discharges in JET-CW having similar global operational parameters. The set contains 10 baseline ({βN}=1.5∼ 2 ) discharge-pairs with 2.7 T toroidal magnetic field, 2.5 MA plasma current, and 14 to 17 MW of neutral beam injection (NBI) heating. Based on a Te profile analysis using high resolution Thomson scattering (HRTS) data, the Te profile peaking (i.e. core Te (ρ = 0.3) / edge Te (ρ = 0.7)) is found to be similar, and weakly dependent on edge Te, for both JET-ILW and JET-CW discharges. When ILW discharges are seeded with N2, core and edge Te both increase to maintain a similar peaking factor. The change in core confinement is addressed with interpretative TRANSP simulations. It is found that JET-ILW H-mode plasmas have higher NBI power deposition to electrons and lower NBI power deposition to ions as compared to the JET-CW counterparts. This is an effect of the lower electron temperature at the top of the pedestal. As a result, the core electron energy confinement time is reduced in JET-ILW discharges, but the core ion energy confinement time is not decreased. Overall, the core energy confinement is found to be the same in the JET-ILW discharges compared to the JET-CW counterparts.

Domain-adaptive finite difference methods for collapsing annular liquid jets

NASA Astrophysics Data System (ADS)

Ramos, J. I.

1993-01-01

A domain-adaptive technique which maps a time-dependent, curvilinear geometry into a unit square is used to determine the steady state mass absorption rate and the collapse of annular liquid jets. A method of lines is used to solve the one-dimensional fluid dynamics equations written in weak conservation-law form, and upwind differences are employed to evaluate the axial convective fluxes. The unknown, time-dependent, axial location of the downstream boundary is determined from the solution of an ordinary differential equation which is nonlinearly coupled to the fluid dynamics and gas concentration equations. The equation for the gas concentration in the annular liquid jet is written in strong conservation-law form and solved by means of a method of lines at high Peclet numbers and a line Gauss-Seidel method at low Peclet numbers. The effects of the number of grid points along and across the annular jet, time step, and discretization of the radial convective fluxes on both the steady state mass absorption rate and the jet's collapse rate have been analyzed on staggered and non-staggered grids. The steady state mass absorption rate and the collapse of annular liquid jets are determined as a function of the Froude, Peclet and Weber numbers, annular jet's thickness-to-radius ratio at the nozzle exit, initial pressure difference across the annular jet, nozzle exit angle, temperature of the gas enclosed by the annular jet, pressure of the gas surrounding the jet, solubilities at the inner and outer interfaces of the annular jet, and gas concentration at the nozzle exit. It is shown that the steady state mass absorption rate is proportional to the inverse square root of the Peclet number except for low values of this parameter, and that the possible mathematical incompatibilities in the concentration field at the nozzle exit exert a great influence on the steady state mass absorption rate and on the jet collapse. It is also shown that the steady state mass absorption rate increases as the Weber number, nozzle exit angle, gas concentration at the nozzle exit, and temperature of the gases enclosed by the annular liquid jet are increased, but it decreases as the Froude and Peclet numbers, and annular liquid jet's thickness-to-radius ratio at the nozzle exit are increased. It is also shown that the annular liquid jet's collapse rate increases as the Weber number, nozzle exit angle, temperature of the gases enclosed by the annular liquid jet, and pressure of the gases which surround the jet are increased, but decreases as the Froude and Peclet numbers, and annular liquid jet's thickness-toradius ratio at the nozzle exit are increased. It is also shown that both the ratio of the initial pressure of the gas enclosed by the jet to the pressure of the gas surrounding the jet and the ratio of solubilities at the annular liquid jet's inner and outer interfaces play an important role on both the steady state mass absorption rate and the jet collapse. If the product of these ratios is greater or less than one, both the pressure and the mass of the gas enclosed by the annular liquid jet decrease or increase, respectively, with time. It is also shown that the numerical results obtained with the conservative, domain-adaptive method of lines technique presented in this paper are in excellent agreement with those of a domain-adaptive, iterative, non-conservative, block-bidiagonal, finite difference method which uncouples the solution of the fluid dynamics equations from that of the convergence length.

Additively manufactured MEMS multiplexed coaxial electrospray sources for high-throughput, uniform generation of core-shell microparticles.

PubMed

Olvera-Trejo, D; Velásquez-García, L F

2016-10-18

This study reports the first MEMS multiplexed coaxial electrospray sources in the literature. Coaxial electrospraying is a microencapsulation technology based on electrohydrodynamic jetting of two immiscible liquids, which allows precise control with low size variation of the geometry of the core-shell particles it generates, which is of great importance in numerous biomedical and engineering applications, e.g., drug delivery and self-healing composites. By implementing monolithic planar arrays of miniaturized coaxial electrospray emitters that work uniformly in parallel, the throughput of the compound microdroplet source is greatly increased, making the microencapsulation technology compatible with low-cost commercial applications. Miniaturized core-shell particle generators with up to 25 coaxial electrospray emitters (25 emitters cm -2 ) were fabricated via stereolithography, which is an additive manufacturing process that can create complex microfluidic devices at a small fraction of the cost per device and fabrication time associated with silicon-based counterparts. The characterization of devices with the same emitter structure but different array sizes demonstrates uniform array operation. Moreover, the data demonstrate that the per-emitter current is approximately proportional to the square root of the flow rate of the driving liquid, and it is independent of the flow rate of the driven liquid, as predicted by the theory. The core/shell diameters and the size distribution of the generated compound microparticles can be modulated by controlling the flow rates fed to the emitters.

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

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

Steinke, I.; Lehmkühler, F., E-mail: felix.lehmkuehler@desy.de; Schroer, M. A.

2016-06-15

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

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

DOE PAGES

Steinke, I.; Walther, M.; Lehmkühler, F.; ...

2016-06-01

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

Stretched Inertial Jets

NASA Astrophysics Data System (ADS)

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

2015-11-01

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

Jet dynamics post drop impact on a deep pool

NASA Astrophysics Data System (ADS)

Michon, Guy-Jean; Josserand, Christophe; Séon, Thomas

2017-02-01

We investigate experimentally the jet formed by the collapse of a cavity created by the impact of a drop on a pool of the same aqueous liquid. We show that jets can emerge with very different shapes and velocities, depending on the impact parameters, thus generating droplets with various initial sizes and velocities. After presenting the jet velocity and top drop radius variation as a function of the impact parameters, we discuss the influence of the liquid parameters on the jet velocity. This allows us to define two different regimes: the singular jet and the cavity jet regimes, where the mechanisms leading to the cavity retraction and subsequent jet dynamics are drastically different. In particular, we demonstrate that in the first regime, a singular capillary wave collapse sparks the whole jet dynamics, making the jet's fast, thin, liquid parameters dependent and barely reproducible. On the contrary, in the cavity jet regime, defined for higher impact Froude numbers, the jets are fat and slow. We show that jet velocity is simply proportional to the capillary velocity √{γ /ρlDd }, where γ is the liquid surface tension, ρl the liquid density, and Dd the impacting drop diameter, and it is in particular independent of viscosity, impact velocity, and gravity, even though the cavity is larger than the capillary length. Finally, we demonstrate that capillary wave collapse and cavity retraction are correlated in the singular regime and decorrelated in the cavity jet regime.

Novel Techniques for Quantification of Correlation Between Primary Liquid Jet Breakup and Downstream Spray Characteristics

DTIC Science & Technology

2016-05-08

unlimited. 5 1. Introduction Several liquid -fuelled combustion systems, such as liquid propellant rocket engines and gas turbines...AFRL-AFOSR-JP-TR-2016-0084 Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray characteristics...to 17 Apr 2016 4.  TITLE AND SUBTITLE Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray

Novel Techniques for Quantification of Correlation Between Primary Liquid Jet Breakup and Downstream Spray Characteristics

DTIC Science & Technology

2016-10-05

unlimited. 5 1. Introduction Several liquid -fuelled combustion systems, such as liquid propellant rocket engines and gas turbines...AFRL-AFOSR-JP-TR-2016-0084 Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray characteristics...to 17 Apr 2016 4.  TITLE AND SUBTITLE Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray

Impact of Azimuthally Controlled Fluidic Chevrons on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Norum, Thomas D.

2008-01-01

The impact of azimuthally controlled air injection on broadband shock noise and mixing noise for single and dual stream jets was investigated. The single stream experiments focused on noise reduction for low supersonic jet exhausts. Dual stream experiments included high subsonic core and fan conditions and supersonic fan conditions with transonic core conditions. For the dual stream experiments, air was injected into the core stream. Significant reductions in broadband shock noise were achieved in a single jet with an injection mass flow equal to 1.2% of the core mass flow. Injection near the pylon produced greater broadband shock noise reductions than injection at other locations around the nozzle periphery. Air injection into the core stream did not result in broadband shock noise reduction in dual stream jets. Fluidic injection resulted in some mixing noise reductions for both the single and dual stream jets. For subsonic fan and core conditions, the lowest noise levels were obtained when injecting on the side of the nozzle closest to the microphone axis.

Characterization of Three-Stream Jet Flow Fields

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Wernet, Mark P.

2016-01-01

Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10 percent) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50 percent of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65 percent of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

Characterization of Three-Stream Jet Flow Fields

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Wernet, Mark P.

2016-01-01

Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10%) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50% of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65% of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

Physics of liquid jets

NASA Astrophysics Data System (ADS)

Eggers, Jens; Villermaux, Emmanuel

2008-03-01

Jets, i.e. collimated streams of matter, occur from the microscale up to the large-scale structure of the universe. Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids. Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology. Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup. In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology. They also arise from the last but one topology change of liquid masses bursting into sprays. Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium. The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects.

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.

Sharp Interface Algorithm for Large Density Ratio Incompressible Multiphase Magnetohydrodynamic Flows

DTIC Science & Technology

2013-01-01

experiments on liquid metal jets . The FronTier-MHD code has been used for simulations of liquid mercury targets for the proposed muon collider...validated through the comparison with experiments on liquid metal jets . The FronTier-MHD code has been used for simulations of liquid mercury targets...FronTier-MHD code have been performed using experimental and theoretical studies of liquid mercury jets in magnetic fields. Experimental studies of a

[Development of a novel liquid injection system].

PubMed

Chen, Kai; Lv, Yong-Gui

2009-11-01

A liquid jet injector employs compressed gas or spring to produce a high-velocity stream to deliver liquid drug into human body through skin. There are many clinical jet injection products available, none of which is domestic. A new liquid jet injector is designed based on a comprehensive analysis of the current products. The injector consists of an ejector, trigger and a re-positioning mechanism. The jets characteristics of sample injector are tested, and the results show that the maximum exit pressure is above 15 MPa, a threshold value for penetrating into the skin.

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

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

Lü, Ming; Ning, Zhi, E-mail: zhining@bjtu.edu.cn; Lu, Mei

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,more » (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.« less

Atomization of liquids in a Pease-Anthony Venturi scrubber. Part I. Jet dynamics.

PubMed

Gonçalves, J A S; Costa, M A M; Henrique, P R; Coury, J R

2003-02-28

Jet dynamics, in particular jet penetration, is an important design parameter affecting the collection efficiency of Venturi scrubbers. A mathematical description of the trajectory, break-up and penetration of liquid jets initially transversal to a subsonic gas stream is presented. Experimental data obtained from a laboratory scale Venturi scrubber, operated with liquid injected into the throat through a single orifice, jet velocities between 6.07 and 15.9 m/s, and throat gas velocities between 58.3 and 74.9 m/s, is presented and used to validate the model.

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.

Large Eddy Simulation of Cryogenic Injection Processes at Supercritical Pressure

NASA Technical Reports Server (NTRS)

Oefelein, Joseph C.; Garcia, Roberto (Technical Monitor)

2002-01-01

This paper highlights results from the first of a series of hierarchical simulations aimed at assessing the modeling requirements for application of the large eddy simulation technique to cryogenic injection and combustion processes in liquid rocket engines. The focus is on liquid-oxygen-hydrogen coaxial injectors at a condition where the liquid-oxygen is injected at a subcritical temperature into a supercritical environment. For this situation a diffusion dominated mode of combustion occurs in the presence of exceedingly large thermophysical property gradients. Though continuous, these gradients approach the behavior of a contact discontinuity. Significant real gas effects and transport anomalies coexist locally in colder regions of the flow, with ideal gas and transport characteristics occurring within the flame zone. The current focal point is on the interfacial region between the liquid-oxygen core and the coaxial hydrogen jet where the flame anchors itself.

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.

Liquid sampling system

DOEpatents

Larson, Loren L.

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.

Deformations of free jets

NASA Astrophysics Data System (ADS)

Paruchuri, Srinivas

This thesis studies three different problems. First we demonstrate that a flowing liquid jet can be controllably split into two separate subfilaments through the applications of a sufficiently strong tangential stress to the surface of the jet. In contrast, normal stresses can never split a liquid jet. We apply these results to observations of uncontrolled splitting of jets in electric fields. The experimental realization of controllable jet splitting would provide an entirely novel route for producing small polymeric fibers. In the second chapter we present an analytical model for the bending of liquid jets and sheets from temperature gradients, as recently observed by Chwalek et al. [Phys. Fluids, 14, L37 (2002)]. The bending arises from a local couple caused by Marangoni forces. The dependence of the bending angle on experimental parameters is presented, in qualitative agreement with reported experiments. The methodology gives a simple framework for understanding the mechanisms for jet and sheet bending. In chapter 4 we address the discrepancy between hydrodynamic theory of liquid jets, and the snap-off of narrow liquid jets observed in molecular dynamics (MD) simulations [23]. This has been previously attributed to the significant role of thermal fluctuations in nanofluidic systems. We argue that hydrodynamic description of such systems should include corrections to the Laplace pressure which result from the failure of the sharp interface assumption when the jet diameter becomes small enough. We show that this effect can in principle give rise to jet shapes similar to those observed in MD simulations, even when thermal fluctuations are completely neglected. Finally we summarize an algorithm developed to simulate droplet impact on a smooth surface.

Plasma-Spray Metal Coating On Foam

NASA Technical Reports Server (NTRS)

Cranston, J.

1994-01-01

Molds, forms, and other substrates made of foams coated with metals by plasma spraying. Foam might be ceramic, carbon, metallic, organic, or inorganic. After coat applied by plasma spraying, foam left intact or removed by acid leaching, conventional machining, water-jet cutting, or another suitable technique. Cores or vessels made of various foam materials plasma-coated with metals according to method useful as thermally insulating containers for foods, liquids, or gases, or as mandrels for making composite-material (matrix/fiber) parts, or making thermally insulating firewalls in automobiles.

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.

Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid MICR

DTIC Science & Technology

2014-12-23

Detailed discussions of the microjet technique are carried out in the following publications. Nozzle Liquid Jet Chopper Wheel Cold Collector Cold...process is shown in the picture below; heating and evaporation occur within 1 ms of fuel leaving the fuel injector . This atomization proves is often...liquid jet. This analysis leads to criteria for selecting the temperature and nozzle radius for producing stable jets in vacuum. Figure 4 depicts the

Acoustically Forced Coaxial Hydrogen/Liquid Oxygen Jet Flames

DTIC Science & Technology

2016-05-15

Briefing Charts 3. DATES COVERED (From - To) 25 April 2016 - 15 May 2016 4. TITLE AND SUBTITLE Acoustically Forced Coaxial Hydrogen / Liquid Oxygen Jet...area code) N/A Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 1 Acoustically Forced Coaxial Hydrogen / Liquid Oxygen Jet Flames...propellants be stored in condensed form – e.g., kerosene, liquid oxygen in rockets • Combustion systems can no longer be designed to meet modern

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.

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.

New quasi-geostrophic flow estimations for the Earth's core

NASA Astrophysics Data System (ADS)

Pais, M. Alexandra

2014-05-01

Quasi-geostrophic (QG) flows have been reported in numerical dynamo studies that simulate Boussinesq convection of an electrical conducting fluid inside a rapidly rotating spherical shell. In these cases, the required condition for columnar convection seems to be that inertial waves should propagate much faster in the medium than Alfvén waves. QG models are particularly appealing for studies where Earth's liquid core flows are assessed from information contained in geomagnetic data obtained at and above the Earth's surface. Here, they make the whole difference between perceiving only the core surface expression of the geodynamo or else assessing the whole interior core flow. The QG approximation has now been used in different studies to invert geomagnetic field models, providing a different kinematic interpretation of the observed geomagnetic field secular variation (SV). Under this new perspective, a large eccentric jet flowing westward under the Atlantic Hemisphere and a cyclonic column under the Pacific were pointed out as interesting features of the flow. A large eccentric jet with similar characteristics has been explained in recent numerical geodynamo simulations in terms of dynamical coupling between the solid core, the liquid core and the mantle. Nonetheless, it requires an inner core crystallization on the eastern hemisphere, contrary to what has been proposed in recent dynamical models for the inner core. Some doubts remain, as we see, concerning the dynamics that can explain the radial outward flow in the eastern core hemisphere, actually seen in inverted core flow models. This and other puzzling features justify a new assessment of core flows, taking full advantage of the recent geomagnetic field model COV-OBS and of experience, accumulated over the years, on flow inversion. Assuming the QG approximation already eliminates a large part of non-uniqueness in the inversion. Some important non-uniqueness still remains, inherent to the physical model, given our present inability to distinguish the small length scales of the internal geomagnetic field when measuring it at the Earth's surface and above. This can be dealt with in the form of a parameterization error. We recalculated flow models for the whole 1840-2010 period of COV-OBS, using the covariance matrices provided by the authors and an iterative estimation of the parameterization error. Results are compared with previous estimations. We then apply standard tools of Empirical Orthogonal Functions/ Principal Components Analysis to sort out variability modes that, hopefully, can also be identified with dynamical modes.

Size of the top jet drop produced by bubble bursting

NASA Astrophysics Data System (ADS)

Berny, Alexis; Deike, Luc; Popinet, Stéphane; Seon, Thomas

2017-11-01

When a bubble is located on a liquid-air interface, it eventually bursts. First, the bubble cap shatters and produces film drops. Then, the cavity collapses, a tiny liquid jet rises and, depending on bubble radius and liquid parameters, it can eventually break-up and release the so-called jet drops. We perform numerical simulations, using the free software basilisk, to determine and discuss the regime of existence and the size of the first liquid jet droplets. We first validate the numerical scheme by comparing our results with recent experimental data. We then extend our numerical study to a wider range of control parameters in order to enrich our knowledge of the jet drops production. Finally, we show and interpret our results using a scaling law approach and basic physical arguments. This allows us to untangle the intricate roles of viscosity, gravity, and surface tension in the end pinching of the bubble bursting jet.

Effects of forward motion on jet and core noise

NASA Technical Reports Server (NTRS)

Low, J. K. C.

1977-01-01

A study was conducted to investigate the effects of forward motion on both jet and core noise. Measured low-frequency noise from static-engine and from flyover tests with a DC-9-30 powered by JT8D-109 turbofan engines and with a DC-10-40 powered by JT9D-59A turbofan engines was separated into jet- and core noise components. Comparisons of the static and the corresponding in-flight jet- and core-noise components are presented. The results indicate that for the DC-9 airplane at low power settings, where core noise is predominant, the effect of convective amplification on core-noise levels is responsible for the higher in-flight low-frequency noise levels in the inlet quadrant. Similarly, it was found that for the DC-10 airplane with engines mounted under the wings and flaps and flap deflection greater than 30 degrees, the contribution from jet-flap-interaction noise is as much as 5 dB in the inlet quadrant and is responsible for higher in-flight low-frequency noise levels during approach conditions. Those results indicate that to properly investigate flight effects, it is important to consider the noise contributions from other low-frequency sources, such as the core and the jet-flap interaction.

ACCELERATION OF COMPACT RADIO JETS ON SUB-PARSEC SCALES

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

Lee, Sang-Sung; Lobanov, Andrei P.; Krichbaum, Thomas P.

2016-08-01

Jets of compact radio sources are highly relativistic and Doppler boosted, making studies of their intrinsic properties difficult. Observed brightness temperatures can be used to study the intrinsic physical properties of relativistic jets, and constrain models of jet formation in the inner jet region. We aim to observationally test such inner jet models. The very long baseline interferometry (VLBI) cores of compact radio sources are optically thick at a given frequency. The distance of the core from the central engine is inversely proportional to the frequency. Under the equipartition condition between the magnetic field energy and particle energy densities, themore » absolute distance of the VLBI core can be predicted. We compiled the brightness temperatures of VLBI cores at various radio frequencies of 2, 8, 15, and 86 GHz. We derive the brightness temperature on sub-parsec scales in the rest frame of the compact radio sources. We find that the brightness temperature increases with increasing distance from the central engine, indicating that the intrinsic jet speed (the Lorentz factor) increases along the jet. This implies that the jets are accelerated in the (sub-)parsec regions from the central engine.« less

Numerical Investigation on Sensitivity of Liquid Jet Breakup to Physical Fuel Properties with Experimental Comparison

NASA Astrophysics Data System (ADS)

Kim, Dokyun; Bravo, Luis; Matusik, Katarzyna; Duke, Daniel; Kastengren, Alan; Swantek, Andy; Powell, Christopher; Ham, Frank

2016-11-01

One of the major concerns in modern direct injection engines is the sensitivity of engine performance to fuel characteristics. Recent works have shown that even slight differences in fuel properties can cause significant changes in efficiency and emission of an engine. Since the combustion process is very sensitive to the fuel/air mixture formation resulting from disintegration of liquid jet, the precise assessment of fuel sensitivity on liquid jet atomization process is required first to study the impact of different fuels on the combustion. In the present study, the breaking process of a liquid jet from a diesel injector injecting into a quiescent gas chamber is investigated numerically and experimentally for different liquid fuels (n-dodecane, iso-octane, CAT A2 and C3). The unsplit geometric Volume-of-Fluid method is employed to capture the phase interface in Large-eddy simulations and results are compared against the radiography measurement from Argonne National Lab including jet penetration, liquid mass distribution and volume fraction. The breakup characteristics will be shown for different fuels as well as droplet PDF statistics to demonstrate the influences of the physical properties on the primary atomization of liquid jet. Supported by HPCMP FRONTIER award, US DOD, Office of the Army.

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.

A combined Eulerian-volume of fraction-Lagrangian method for atomization simulation

NASA Technical Reports Server (NTRS)

Seung, S. P.; Chen, C. P.; Ziebarth, John P.

1994-01-01

The tracking of free surfaces between liquid and gas phases and analysis of the interfacial phenomena between the two during the atomization and breakup process of a liquid fuel jet is modeled. Numerical modeling of liquid-jet atomization requires the resolution of different conservation equations. Detailed formulation and validation are presented for the confined dam broken problem, the water surface problem, the single droplet problem, a jet breakup problem, and the liquid column instability problem.

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.

Large-Scale Flows and Magnetic Fields Produced by Rotating Convection in a Quasi-Geostrophic Model of Planetary Cores

NASA Astrophysics Data System (ADS)

Guervilly, C.; Cardin, P.

2017-12-01

Convection is the main heat transport process in the liquid cores of planets. The convective flows are thought to be turbulent and constrained by rotation (corresponding to high Reynolds numbers Re and low Rossby numbers Ro). Under these conditions, and in the absence of magnetic fields, the convective flows can produce coherent Reynolds stresses that drive persistent large-scale zonal flows. The formation of large-scale flows has crucial implications for the thermal evolution of planets and the generation of large-scale magnetic fields. In this work, we explore this problem with numerical simulations using a quasi-geostrophic approximation to model convective and zonal flows at Re 104 and Ro 10-4 for Prandtl numbers relevant for liquid metals (Pr 0.1). The formation of intense multiple zonal jets strongly affects the convective heat transport, leading to the formation of a mean temperature staircase. We also study the generation of magnetic fields by the quasi-geostrophic flows at low magnetic Prandtl numbers.

Numerical simulation of liquid jet impact on a rigid wall

NASA Astrophysics Data System (ADS)

Aganin, A. A.; Guseva, T. S.

2016-11-01

Basic points of a numerical technique for computing high-speed liquid jet impact on a rigid wall are presented. In the technique the flows of the liquid and the surrounding gas are governed by the equations of gas dynamics in the density, velocity, and pressure, which are integrated by the CIP-CUP method on dynamically adaptive grids without explicitly tracking the gas-liquid interface. The efficiency of the technique is demonstrated by the results of computing the problems of impact of the liquid cone and the liquid wedge on a wall in the mode with the shockwave touching the wall by its edge. Numerical solutions of these problems are compared with the analytical solution of the problem of impact of the plane liquid flow on a wall. Applicability of the technique to the problems of the high-speed liquid jet impact on a wall is illustrated by the results of computing a problem of impact of a cylindrical liquid jet with the hemispherical end on a wall covered by a layer of the same liquid.

Superheated liquid carbon dioxide jets: setting up and phenomena

NASA Astrophysics Data System (ADS)

Engelmeier, Lena; Pollak, Stefan; Peters, Franz; Weidner, Eckhard

2018-01-01

We present an experimental investigation on liquid, superheated carbon dioxide jets. Our main goal is to identify the setting up requirements for generating coherent jets because these raise expectations on applications in the cleaning and cutting industry. The study leads us through a number of phenomena, which are described, categorized and explained. The experiments are based on compressed (350 MPa) and cooled carbon dioxide, which expands through a cylindrical nozzle into the atmosphere. The nozzle provokes hydraulic flip by a sharp-edge inlet leading to separation and constriction. Upstream-temperature and pressure are varied and the jet's structure and phase state are monitored by a high-speed camera. We observe coherent, liquid jets far from equilibrium, which demands the solid or gaseous state. Therefore, these jets are superheated. Carbon dioxide jets, like water jets, below certain nozzle diameters are subject to fluid dynamic instabilities resulting in breakup. Above certain diameters flashing jet breakup appears, which is associated with nucleation.

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...

Distortion of liquid film discharging from twin-fluid atomizer

NASA Astrophysics Data System (ADS)

Mehring, C.; Sirignano, W. A.

2001-11-01

The nonlinear distortion and disintegration of a thin liquid film exiting from a two-dimensional twin-fluid atomizer is analyzed numerically. Pulsed gas jets impacting on both sides of the discharging liquid film at the atomizer exit generate dilational and/or sinuous deformations of the film. Both liquid phase and gas phase are inviscid and incompressible. For the liquid phase the so-called long-wavelength approximation is employed yielding a system of unsteady one-dimensional equations for the planar film. Solution of Laplace's equation for the velocity potential yields the gas-phase velocity field on both sides of the liquid stream. Coupling between both phases is described through kinematic and dynamic boundary conditions at the phase interfaces, and includes the solution of the unsteady Bernoulli equation to determine the gas-phase pressure along the interfaces. Both gas- and liquid-phase equations are solved simultaneously. Solution of Laplace's equation for the gas streams is obtained by means of a boundary-element method. Numerical solutions for the liquid phase use the Lax-Wendroff method with Richtmyer splitting. Sheet distortion resulting from the stagnation pressure of the impacting gas jets and subsequent disturbance amplification due to Kelvin-Helmholtz effects are studied for various combinations of gas-pulse timing, gas-jet impact angles, gas-to-liquid-density ratio, liquid-phase Weber number and gas-jet-to-liquid-jet-momentum ratio. Dilational and sinuous oscillations of the liquid are examined and film pinch-off is predicted.

Numerical modeling of the interaction of liquid drops and jets with shock waves and gas jets

NASA Astrophysics Data System (ADS)

Surov, V. S.

1993-02-01

The motion of a liquid drop (jet) and of the ambient gas is described, in the general case, by Navier-Stokes equations. An approximate solution to the interaction of a plane shock wave with a single liquid drop is presented. Based on the analysis, the general system of Navier-Stokes equations is reduced to two groups of equations, Euler equations for gas and Navier-Stokes equations for liquid; solutions to these equations are presented. The discussion also covers the modeling of the interaction of a shock wave with a drop screen, interaction of a liquid jet with a counterpropagating supersonic gas flow, and modeling of processes in a shock layer during the impact of a drop against an obstacle in gas flow.

Experimental and numerical investigation of liquid jet impingement on superhydrophobic and hydrophobic convex surfaces

NASA Astrophysics Data System (ADS)

Kibar, Ali

2017-02-01

Experiments and numerical simulations were carried out to examine the vertical impingement a round liquid jet on the edges of horizontal convex surfaces that were either superhydrophobic or hydrophobic. The experiments examine the effects on the flow behaviour of curvature, wettability, inertia of the jet, and the impingement rate. Three copper pipes with outer diameters of 15, 22, and 35 mm were investigated. The pipes were wrapped with a piece of a Brassica oleracea leaf or a smooth Teflon sheet, which have apparent contact angles of 160° and 113°. The Reynolds number ranged from 1000 to 4500, and the impingement rates of the liquid jets were varied. Numerical results show good agreement with the experimental results for explaining flow and provide detailed information about the impingement on the surfaces. The liquid jet reflected off the superhydrophobic surfaces for all conditions. However, the jet reflected or deflected off the hydrophobic surface, depending on the inertia of the jet, the curvature of the surface, and the impingement rate. The results suggest that pressure is not the main reason for the bending of the jet around the curved hydrophobic surface.

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.

Effects of core turbulence on jet excitability

NASA Technical Reports Server (NTRS)

Mankbadi, Reda R.; Raman, Ganesh; Rice, Edward J.

1989-01-01

The effects of varying freestream core turbulence on the evolution of a circular jet with and without tonal excitation are examined. Measurements are made on an 8.8 cm diameter jet at a Mach number of 0.3. The jet is excitated by plane waves at Strouhal number 0.5. For the excited and unexcited cases the turbulence level is varied by screens and grids placed upstream of the nozzle exit. The experiment results are compared with a theoretical model which incorporates a variable core turbulence and considers the energy interactions between the mean flow, the turbulence and the forced component. Both data and theory indicate that increasing the freestream turbulence diminishes the excitability of the jet and reduces the effect of excitation on the spreading rate of the jet.

Exact Solution of the Two-Dimensional Problem on an Impact Ideal-Liquid Jet

NASA Astrophysics Data System (ADS)

Belik, V. D.

2018-05-01

The two-dimensional problem on the collision of a potential ideal-liquid jet, outflowing from a reservoir through a nozzle, with an infinite plane obstacle was considered for the case where the distance between the nozzle exit section and the obstacle is finite. An exact solution of this problem has been found using methods of the complex-variable function theory. Simple analytical expressions for the complex velocity of the liquid, its flow rate, and the force of action of the jet on the obstacle have been obtained. The velocity distributions of the liquid at the nozzle exit section, in the region of spreading of the jet, and at the obstacle have been constructed for different distances between the nozzle exit section and the obstacle. Analytical expressions for the thickness of the boundary layer and the Nusselt number at the point of stagnation of the jet have been obtained. A number of distributions of the local friction coefficient and the Nusselt number of the indicated jet are presented.

Parallel and Perpendicular Alignment of Anisotropic Particles in Free Liquid Microjets and Emerging Microdroplets.

PubMed

Schlenk, Mathias; Hofmann, Eddie; Seibt, Susanne; Rosenfeldt, Sabine; Schrack, Lukas; Drechsler, Markus; Rothkirch, Andre; Ohm, Wiebke; Breu, Josef; Gekle, Stephan; Förster, Stephan

2018-04-24

Liquid microjets play a key role in fiber spinning, inkjet printing, and coating processes. In all of these applications, the liquid jets carry dispersed particles whose spatial and orientational distributions within the jet critically influence the properties of the fabricated structures. Despite its importance, there is currently no knowledge about the orientational distribution of particles within microjets and droplets. Here, we demonstrate a microfluidic device that allows to determine the local particle distribution and orientation by X-ray scattering. Using this methodology, we discovered unexpected changes in the particle orientation upon exiting the nozzle to form a free jet, and upon jet break-up into droplets, causing an unusual biaxial particle orientation. We show how flow and aspect ratio determine the flow orientation of anisotropic particles. Furthermore, we demonstrate that the observed phenomena are a general characteristic of anisotropic particles. Our findings greatly enhance our understanding of particle orientation in free jets and droplets and provide a rationale for controlling particle alignment in liquid jet-based fabrication methodologies.

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

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

Wang, Zhen-guo, E-mail: wangzhenguo-wzg@163.com; Wu, Liyin; Li, Qinglian

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. Themore » 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.« less

Numerical study of ambient pressure for laser-induced bubble near a rigid boundary

NASA Astrophysics Data System (ADS)

Li, BeiBei; Zhang, HongChao; Han, Bing; Lu, Jian

2012-07-01

The dynamics of the laser-induced bubble at different ambient pressures was numerically studied by Finite Volume Method (FVM). The velocity of the bubble wall, the liquid jet velocity at collapse, and the pressure of the water hammer while the liquid jet impacting onto the boundary are found to increase nonlinearly with increasing ambient pressure. The collapse time and the formation time of the liquid jet are found to decrease nonlinearly with increasing ambient pressure. The ratios of the jet formation time to the collapse time, and the displacement of the bubble center to the maximal radius while the jet formation stay invariant when ambient pressure changes. These ratios are independent of ambient pressure.

Experimental study of elliptical jet from sub to supercritical conditions

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

Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in

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 weremore » 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.« less

The imprints of the last jets in core collapse supernovae

NASA Astrophysics Data System (ADS)

Bear, Ealeal; Grichener, Aldana; Soker, Noam

2017-12-01

We analyse the morphologies of three core collapse supernova remnants (CCSNRs) and the energy of jets in other CCSNRs and in Super Luminous Supernovae (SLSNe) of type Ib/Ic/IIb, and conclude that these properties are well explained by the last jets' episode as expected in the jet feedback explosion mechanism of core collapse supernovae (CCSNe). The presence of two opposite protrusions, termed ears, and our comparison of the CCSNR morphologies with morphologies of planetary nebulae strengthen the claim that jets play a major role in the explosion mechanism of CCSNe. We crudely estimate the energy that was required to inflate the ears in two CCSNRs and assume that the ears were inflated by jets. We find that the energies of the jets which inflated ears in 11 CCSNRs span a range that is similar to that of jets in some energetic CCSNe (SLSNe) and that this energy, only of the last jets' episode, is much less than the explosion energy. This finding is compatible with the jet feedback explosion mechanism of CCSNe, where only the last jets, which carry a small fraction of the total energy carried by earlier jets, are expected to influence the outer parts of the ejecta. We reiterate our call for a paradigm shift from neutrino-driven to jet-driven explosion models of CCSNe.

Mechanics of Micro- and Nano-Textured Systems: Nanofibers, Nanochannels, Nanoparticles and Slurries

NASA Astrophysics Data System (ADS)

Sinha Ray, Suman

The first chapter of this work deals with bundles of microscopically long carbon nanochannels, which were assembled as a nanofluidic device to study bi-layer flows of n-decane and air. These experiments were accompanied and supported by theoretical considerations. The study paradoxically showed that it is possible to deliver more liquid through the nanochannels if they are partially filled with liquid in comparison to those which are completely filled with liquid. In the following chapter these nanochannels were used to produce thermoresponsive nanoparticles (˜400 nm in diameter) at a very high production rate of 107 particles/sec. These nanoparticles were loaded with a low molecular weight dye to study the thermoresponsive release profile experimentally. The experiments were accompanied and guided by theoretical work. In the third part of the work, a rigorous electron microscopy revealed the 2-nm islands of thermoresponsive hydrogels nanofibers produced by electrospinning and cross-linking of electropun PNIPAM-containing nanofibers. These islands were found to be responsible for positive thermosensitivity in dye release experiments. In the following chapters meltblowing was studied both experimentally and theoretically. The role of air turbulence in this process was elucidated experimentally by blowing a solid flexible threadline in high-speed gas flow. Using this information, theoretical understanding of polymer jet/gas jet turbulent interactions was achieved and a theory of small (linearized) and large (nonlinear) bending perturbations of polymer jets was developed. This theory was extended to simulate numerically multiple polymer jets being deposited on a screen moving normally to the blowing direction. In the subsequent chapter, a novel method, solution blowing, for producing monolithic and core-shell nanofibers was developed. The core-shell fibers were also converted into hollow carbon nanotubes. The carbon nanofiber mats produced by this method were used as an electrode in a microbial fuel cell, which showed a higher current density in comparison to standard polycrystalline graphite rods. In addition, solution blowing was used to form soy-protein-containing biodegradable nanofibers. In the next chapter, a novel method of intercalating wax and butter en masse into carbon nanotubes was demonstrated. It was shown that by manipulating the intercalated solute the working temperature range of phase-change materials (PCM) can be significantly widened, while the response time reduced to minimum. In the final part of the work the elongational rheology of gypsum slurries was also studied and corroborated using the data from the corresponding shear rheological studies. It was shown that the gypsum slurries approximately follow the tensorial Ostwald-de-Waele (power law) constitutive equation.

The Effect of Orifice Eccentricity on Instability of Liquid Jets

NASA Astrophysics Data System (ADS)

Amini, Ghobad; Dolatabadi, Ali

2011-11-01

The hydrodynamic instability of inviscid jets issuing from elliptic orifices is studied. A linear stability analysis is presented for liquid jets that includes the effect of the surrounding gas and an explicit dispersion equation is derived for waves on an infinite uniform jet column. Elliptic configuration has two extreme cases; round jet when ratio of minor to major axis is unity and plane sheet when this ratio approaches zero. Dispersion equation of elliptic jet is approximated for large and small aspect ratios considering asymptotic of the dispersion equation. In case of aspect ratio equal to one, the dispersion equation is analogous to one of the circular jets derived by Yang. In case of aspect ratio approaches zero, the behavior of waves is qualitatively similar to that of long waves on a two dimensional liquid jets and the varicose and sinuous modes are predicted. The growth rate of initial disturbances for various azimuthal modes has been presented in a wide range of disturbances. PhD Candidate.

Liquid jet response to internal modulated ultrasonic radiation pressure and stimulated drop production.

PubMed

Lonzaga, Joel B; Osterhoudt, Curtis F; Thiessen, David B; Marston, Philip L

2007-06-01

Experimental evidence shows that a liquid jet in air is an acoustic waveguide having a cutoff frequency inversely proportional to the jet diameter. Ultrasound applied to the jet supply liquid can propagate within the jet when the acoustic frequency is near to or above the cutoff frequency. Modulated radiation pressure is used to stimulate large amplitude deformations and the breakup of the jet into drops. The jet response to the modulated internal ultrasonic radiation pressure was monitored along the jet using (a) an optical extinction method and (b) images captured by a video camera. The jet profile oscillates at the frequency of the radiation pressure modulation and where the response is small, the amplitude was found to increase in proportion to the square of the acoustic pressure amplitude as previously demonstrated for oscillating drops [P.L. Marston and R.E. Apfel, J. Acoust. Soc. Am. 67, 27-37 (1980)]. Small amplitude deformations initially grow approximately exponentially with axial distance along the jet. Though aspects of the perturbation growth can be approximated from Rayleigh's analysis of the capillary instability, some detailed features of the observed jet response to modulated ultrasound are unexplained neglecting the effects of gravity.

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.

Core shifts, magnetic fields and magnetization of extragalactic jets

NASA Astrophysics Data System (ADS)

Zdziarski, Andrzej A.; Sikora, Marek; Pjanka, Patryk; Tchekhovskoy, Alexander

2015-07-01

We study the effect of radio-jet core shift, which is a dependence of the position of the jet radio core on the observational frequency. We derive a new method of measuring the jet magnetic field based on both the value of the shift and the observed radio flux, which complements the standard method that assumes equipartition. Using both methods, we re-analyse the blazar sample of Zamaninasab et al. We find that equipartition is satisfied only if the jet opening angle in the radio core region is close to the values found observationally, ≃0.1-0.2 divided by the bulk Lorentz factor, Γj. Larger values, e.g. 1/Γj, would imply magnetic fields much above equipartition. A small jet opening angle implies in turn the magnetization parameter of ≪1. We determine the jet magnetic flux taking into account this effect. We find that the transverse-averaged jet magnetic flux is fully compatible with the model of jet formation due to black hole (BH) spin-energy extraction and the accretion being a magnetically arrested disc (MAD). We calculate the jet average mass-flow rate corresponding to this model and find it consists of a substantial fraction of the mass accretion rate. This suggests the jet composition with a large fraction of baryons. We also calculate the average jet power, and find it moderately exceeds the accretion power, dot{M} c^2, reflecting BH spin energy extraction. We find our results for radio galaxies at low Eddington ratios are compatible with MADs but require a low radiative efficiency, as predicted by standard accretion models.

Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karles Fellowship

DTIC Science & Technology

2015-11-30

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6750--15-9650 Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL... Plasma Physics Division i REPORT DOCUMENTATION PAGE Form ApprovedOMB No. 0704-0188 3. DATES COVERED (From - To) Standard Form 298 (Rev. 8-98...ABSTRACT Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karle’s Fellowship Sandra (Hernandez) Hangarter Naval Research Laboratory 4555

Jets from pulsed-ultrasound-induced cavitation bubbles near a rigid boundary

NASA Astrophysics Data System (ADS)

Brujan, Emil-Alexandru

2017-06-01

The dynamics of cavitation bubbles, generated from short (microsecond) pulses of ultrasound and situated near a rigid boundary, are investigated numerically. The temporal development of the bubble shape, bubble migration, formation of the liquid jet during bubble collapse, and the kinetic energy of the jet are investigated as a function of the distance between bubble and boundary. During collapse, the bubble migrates towards the boundary and the liquid jet reaches a maximum velocity between 80 m s-1 and 120 m s-1, depending on the distance between bubble and boundary. The conversion of bubble energy to kinetic energy of the jet ranges from 16% to 23%. When the bubble is situated in close proximity to the boundary, the liquid jet impacts the boundary with its maximum velocity, resulting in an impact pressure of the order of tens of MPa. The rapid expansion of the bubble, the impact of the liquid jet onto the nearby boundary material, and the high pressure developed inside the bubble at its minimum volume can all contribute to the boundary material damage. The high pressure developed during the impact of the liquid jet onto the biological material and the shearing forces acting on the material surface as a consequence of the radial flow of the jet outward from the impact site are the main damage mechanisms of rigid biological materials. The results are discussed with respect to cavitation damage of rigid biological materials, such as disintegration of renal stones and calcified tissue and collateral effects in pulsed ultrasound surgery.

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.

Growth rate measurement in free jet experiments

NASA Astrophysics Data System (ADS)

Charpentier, Jean-Baptiste; Renoult, Marie-Charlotte; Crumeyrolle, Olivier; Mutabazi, Innocent

2017-07-01

An experimental method was developed to measure the growth rate of the capillary instability for free liquid jets. The method uses a standard shadow-graph imaging technique to visualize a jet, produced by extruding a liquid through a circular orifice, and a statistical analysis of the entire jet. The analysis relies on the computation of the standard deviation of a set of jet profiles, obtained in the same experimental conditions. The principle and robustness of the method are illustrated with a set of emulated jet profiles. The method is also applied to free falling jet experiments conducted for various Weber numbers and two low-viscosity solutions: a Newtonian and a viscoelastic one. Growth rate measurements are found in good agreement with linear stability theory in the Rayleigh's regime, as expected from previous studies. In addition, the standard deviation curve is used to obtain an indirect measurement of the initial perturbation amplitude and to identify beads on a string structure on the jet. This last result serves to demonstrate the capability of the present technique to explore in the future the dynamics of viscoelastic liquid jets.

Pulsed laser-induced liquid jet: evolution from shock/bubble interaction to neurosurgical application

NASA Astrophysics Data System (ADS)

Nakagawa, A.; Kumabe, T.; Ogawa, Y.; Hirano, T.; Kawaguchi, T.; Ohtani, K.; Nakano, T.; Sato, C.; Yamada, M.; Washio, T.; Arafune, T.; Teppei, T.; Atsushi, K.; Satomi, S.; Takayama, K.; Tominaga, T.

2017-01-01

The high-speed liquid (water) jet has distinctive characteristics in surgical applications, such as tissue dissection without thermal damage and small blood vessel preservation, that make it advantageous over more conventional instruments. The continuous pressurized jet has been used since the first medical application of water jets to liver surgery in the 1980s, but exhibited drawbacks partly related to the excess water supply required and unsuitability for application to microsurgical instruments intended for deep, narrow lesions (endoscopic instrumentation and catheters) due to limitations in miniaturization of the device. To solve these issues, we initiated work on the pulsed micro-liquid jet. The idea of the pulsed micro-liquid jet originated from the observation of tissue damage by shock/bubble interactions during extracorporeal shock wave lithotripsy and evolved into experimental application for recanalization of cerebral embolisms in the 1990s. The original method of generating the liquid jet was based on air bubble formation and microexplosives as the shock wave source, and as such could not be applied clinically. The air bubble was replaced by a holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced bubble. Finally, the system was simplified and the liquid jet was generated via irradiation from the Ho:YAG laser within a liquid-filled tubular structure. A series of investigations revealed that this pulsed laser-induced liquid jet (LILJ) system has equivalent dissection and blood vessel preservation characteristics, but the amount of liquid usage has been reduced to less than 2 μ l per shot and can easily be incorporated into microsurgical, endoscopic, and catheter devices. As a first step in human clinical studies, we have applied the LILJ system for the treatment of skull base tumors through the transsphenoidal approach in 9 patients (7 pituitary adenomas and 2 chordomas), supratentorial glioma (all high grade glioma) in 8 patients, including one with fine perforating vessel involvement, and cerebrovascular disease (1 arteriovenous malformation and 2 intracerebral hemorrhages) in 3 patients. Precise dissection and mass reduction of the tumor were obtained in all tumor cases except for one chordoma with significant fibrosis. Small arteries down to 100 μ m were preserved, allowing subsequent microsurgical devascularization. Veins were also preserved occasionally. The arachnoid membrane and the tumor capsule were resistant to the LILJ except for one case with prolonged exposure. No complications related to use of the LILJ system were observed. No disturbance of the surgical field by splashing, aerosol, or dissemination of pathological tissue occurred with placement of the optimal suction system. The Ho:YAG LILJ system enhances the advantages of commercialized pressure-driven continuous liquid jet instrumentation in terms of small vessel preservation and accessibility in confined spaces for minimally invasive neurosurgery, and solves some of the drawbacks involved with excessive liquid use and size.

Flow Field and Acoustic Predictions for Three-Stream Jets

NASA Technical Reports Server (NTRS)

Simmons, Shaun Patrick; Henderson, Brenda S.; Khavaran, Abbas

2014-01-01

Computational fluid dynamics was used to analyze a three-stream nozzle parametric design space. The study varied bypass-to-core area ratio, tertiary-to-core area ratio and jet operating conditions. The flowfield solutions from the Reynolds-Averaged Navier-Stokes (RANS) code Overflow 2.2e were used to pre-screen experimental models for a future test in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center (GRC). Flowfield solutions were considered in conjunction with the jet-noise-prediction code JeNo to screen the design concepts. A two-stream versus three-stream computation based on equal mass flow rates showed a reduction in peak turbulent kinetic energy (TKE) for the three-stream jet relative to that for the two-stream jet which resulted in reduced acoustic emission. Additional three-stream solutions were analyzed for salient flowfield features expected to impact farfield noise. As tertiary power settings were increased there was a corresponding near nozzle increase in shear rate that resulted in an increase in high frequency noise and a reduction in peak TKE. As tertiary-to-core area ratio was increased the tertiary potential core elongated and the peak TKE was reduced. The most noticeable change occurred as secondary-to-core area ratio was increased thickening the secondary potential core, elongating the primary potential core and reducing peak TKE. As forward flight Mach number was increased the jet plume region decreased and reduced peak TKE.

Metal and polymer melt jet formation by the high-power laser ablation

NASA Astrophysics Data System (ADS)

Yoh, Jack J.; Gojani, Ardian B.

2010-02-01

The laser-induced metal and polymer melt jets are studied experimentally. Two classes of physical phenomena of interest are: first, the process of explosive phase change of laser induced surface ablation and second, the hydrodynamic jetting of liquid melts ejected from a beamed spot. We focus on the dynamic link between these two distinct physical phenomena in a framework of forming and patterning of metallic and polymer jets using a high-power Nd:YAG laser. The microexplosion of ablative spot on a target first forms a pocket of hot liquid melt and then it is followed by a sudden volume change of gas-liquid mixture leading to a pressure-induced spray jet ejection into surrounding medium.

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

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

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

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

Baek, Eun Jeong; Joh, Hea Min; Kim, Sun Ja

2016-07-15

In this work, an atmospheric pressure plasma jet was fabricated and studied for plasma–liquid interactions. The plasma jet consists of a quartz-covered pin electrode and outer quartz tube with a tapered nozzle. Using the current–voltage (I-V) and optical emission characteristics of the plasma jet, the plasma density and the speed of the plume were investigated. The optical emission spectra clearly indicated the excited NO, O, OH, N{sub 2}, and N{sub 2}{sup +} in the plasma plumes. Then the plasma jets were applied to the deionized water. We investigated the effects of the operating parameters such as applied voltage, pulse frequency,more » and gas flow rate on the generation of reactive species in the gas and liquid phases. The densities of reactive species including OH radicals were obtained at the plasma–liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. The nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of reactive oxygen and nitrogen species (RONS) in the plasmas and liquids.« less

Transverse liquid fuel jet breakup, burning, and ignition

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

Li, Hsi-shang

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 flamemore » 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.« less

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.

Explosive fragmentation of liquids in spherical geometry

NASA Astrophysics Data System (ADS)

Milne, A.; Longbottom, A.; Frost, D. L.; Loiseau, J.; Goroshin, S.; Petel, O.

2017-05-01

Rapid acceleration of a spherical shell of liquid following central detonation of a high explosive causes the liquid to form fine jets that are similar in appearance to the particle jets that are formed during explosive dispersal of a packed layer of solid particles. Of particular interest is determining the dependence of the scale of the jet-like structures on the physical parameters of the system, including the fluid properties (e.g., density, viscosity, and surface tension) and the ratio of the mass of the liquid to that of the explosive. The present paper presents computational results from a multi-material hydrocode describing the dynamics of the explosive dispersal process. The computations are used to track the overall features of the early stages of dispersal of the liquid layer, including the wave dynamics, and motion of the spall and accretion layers. The results are compared with new experimental results of spherical charges surrounded by a variety of different fluids, including water, glycerol, ethanol, and vegetable oil, which together encompass a significant range of fluid properties. The results show that the number of jet structures is not sensitive to the fluid properties, but primarily dependent on the mass ratio. Above a certain mass ratio of liquid fill-to-explosive burster ( F / B), the number of jets is approximately constant and consistent with an empirical model based on the maximum thickness of the accretion layer. For small values of F / B, the number of liquid jets is reduced, in contrast with explosive powder dispersal, where small F / B yields a larger number of particle jets. A hypothetical explanation of these features based on the nucleation of cavitation is explored numerically.

The effect of liquid target on a nonthermal plasma jet—imaging, electric fields, visualization of gas flow and optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Kovačević, Vesna V.; Sretenović, Goran B.; Slikboer, Elmar; Guaitella, Olivier; Sobota, Ana; Kuraica, Milorad M.

2018-02-01

The article describes the complex study of the interaction of a helium plasma jet with distilled water and saline. The discharge development, spatial distribution of the excited species, electric field measurement results and the results of the Schlieren imaging are presented. The results of the experiments showed that the plasma-liquid interaction could be prolonged with the proper choice of the gas composition between the jet nozzle and the target. This depends on the gas flow and the target distance. Increased conductivity of the liquid does not affect the discharge properties significantly. An increase of the gas flow enables an extension of the plasma duration on the liquid surface up to 10 µs, but with a moderate electric field strength in the ionization wave. In contrast, there is a significant enhancement of the electric field on the liquid surface, up to 30 kV cm-1 for low flows, but with a shorter time of the overall plasma liquid interaction. Ignition of the plasma jet induces a gas flow modification and may cause turbulences in the gas flow. A significant influence of the plasma jet causing a mixing in the liquid is also recorded and it is found that the plasma jet ignition changes the direction of the liquid circulation.

Evaluation of the potential of laser-induced breakdown spectroscopy for detection of trace element in liquid.

PubMed

Yueh, Fang-Yu; Sharma, Ramesh C; Singh, Jagdish P; Zhang, Hansheng; Spencer, William A

2002-11-01

The analytical figure of merit of the potential of laser-induced breakdown spectroscopy (LIBS) has been evaluated for detection of trace element in liquid. LIBS data of Mg, Cr, Mn, and Re were studied. Various optical geometries, which produce the laser spark in and at the liquid sample, were tested. The calibration curves for Mg, Cr, Mn, and Re were obtained at the optimized experimental conditions with bulk liquid and in liquid jet. It was found that measurements using a liquid jet provide better detection limits than bulk liquid measurements. The limits of detection (LOD) of Mg, Cr, Mn, and Re in the present liquid jet measurement are found to be 0.1, 0.4, 0.7, and 8 ppm, respectively. The LOD of Mg using Mg 279.55 nm was compared with the values found in other liquid work.

X-Ray Radiography Measurements of Shear Coaxial Rocket Injectors

DTIC Science & Technology

2013-02-01

turbofan engine exhaust, air blast furnaces, and liquid rocket engines) shear coaxial jets have been stud- ied for over sixty years [1]. In all applications...fluids as either single or multiple phases. Most of the fundamental coaxial jet research has been done using a single phase (either gas-gas or liquid ... liquid mixing). A brief review of single-phase coaxial jet research can be found in Schumaker and Driscoll [5]. Single-phase cases also include work

Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karle’s Fellowship

DTIC Science & Technology

2015-11-30

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6750--15-9650 Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL... Plasma Physics Division i REPORT DOCUMENTATION PAGE Form ApprovedOMB No. 0704-0188 3. DATES COVERED (From - To) Standard Form 298 (Rev. 8-98...ABSTRACT Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karle’s Fellowship Sandra (Hernandez) Hangarter Naval Research Laboratory 4555

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.

Capillary instability of elliptic liquid jets

NASA Astrophysics Data System (ADS)

Amini, Ghobad; Dolatabadi, Ali

2011-08-01

Instability of a liquid jet issuing from an elliptic nozzle in Rayleigh mode is investigated and its behavior is compared with a circular jet. Mathematical solution of viscous free-surface flow for asymmetric geometry is complicated if 3-D analytical solutions are to be obtained. Hence, one-dimensional Cosserat (directed curve) equations are used which can be assumed as a low order form of Navier-Stokes equations for slender jets. Linear solution is performed using perturbation method. Temporal dispersion equation is derived to find the most unstable wavelength responsible for the jet breakup. The obtained results for a circular jet (i.e., an ellipse with an aspect ratio of one) are compared with the classical results of Rayleigh and Weber for inviscid and viscous cases, respectively. It is shown that in the Rayleigh regime, which is the subject of this research, symmetric perturbations are unstable while asymmetric perturbations are stable. Consequently, spatial analysis is performed and the variation of growth rate under the effect of perturbation frequencies for various jet velocities is demonstrated. Results reveal that in comparison with a circular jet, the elliptic jet is more unstable. Furthermore, among liquid jets with elliptical cross sections, those with larger ellipticities have a larger instability growth rate.

Hybrid Analysis of Engine Core Noise

NASA Astrophysics Data System (ADS)

O'Brien, Jeffrey; Kim, Jeonglae; Ihme, Matthias

2015-11-01

Core noise, or the noise generated within an aircraft engine, is becoming an increasing concern for the aviation industry as other noise sources are progressively reduced. The prediction of core noise generation and propagation is especially challenging for computationalists since it involves extensive multiphysics including chemical reaction and moving blades in addition to the aerothermochemical effects of heated jets. In this work, a representative engine flow path is constructed using experimentally verified geometries to simulate the physics of core noise. A combustor, single-stage turbine, nozzle and jet are modeled in separate calculations using appropriate high fidelity techniques including LES, actuator disk theory and Ffowcs-Williams Hawkings surfaces. A one way coupling procedure is developed for passing fluctuations downstream through the flowpath. This method effectively isolates the core noise from other acoustic sources, enables straightforward study of the interaction between core noise and jet exhaust, and allows for simple distinction between direct and indirect noise. The impact of core noise on the farfield jet acoustics is studied extensively and the relative efficiency of different disturbance types and shapes is examined in detail.

Physics on Tap

ERIC Educational Resources Information Center

Wheeler, Andrew P. S.

2012-01-01

This article aims to describe how to visualize surface tension effects in liquid jets. A simple experiment is proposed using the liquid jet flow from a mains water tap/faucet. Using a modern digital camera with a high shutter speed, it is possible to visualize the instabilities (capillary waves) that form within the jet due to the action of…

Investigation of Jet Impingement Cooling Using High Prandtl Number Fluids and Ammonia for Military Applications

DTIC Science & Technology

2004-03-01

interesting application of liquid jets impinging over a surface is for the cooling of microelectronics. Wadsworth and Mudawar [29] performed an...and I. Mudawar , Cooling of a Multiple Electronic Module by Means of Confined Two-Dimensional Jets of Dielectric Liquid, Journal of Heat Transfer, vol

Instability of elliptic liquid jets: Temporal linear stability theory and experimental analysis

NASA Astrophysics Data System (ADS)

Amini, Ghobad; Lv, Yu; Dolatabadi, Ali; Ihme, Matthias

2014-11-01

The instability dynamics of inviscid liquid jets issuing from elliptical orifices is studied, and effects of the surrounding gas and the liquid surface tension on the stability behavior are investigated. A dispersion relation for the zeroth azimuthal (axisymmetric) instability mode is derived. Consistency of the analysis is confirmed by demonstrating that these equations reduce to the well-known dispersion equations for the limiting cases of round and planar jets. It is shown that the effect of the ellipticity is to increase the growth rate over a large range of wavenumbers in comparison to those of a circular jet. For higher Weber numbers, at which capillary forces have a stabilizing effect, the growth rate decreases with increasing ellipticity. Similar to circular and planar jets, increasing the density ratio between gas and liquid increases the growth of disturbances significantly. These theoretical investigations are complemented by experiments to validate the local linear stability results. Comparisons of predicted growth rates with measurements over a range of jet ellipticities confirm that the theoretical model provides a quantitatively accurate description of the instability dynamics in the Rayleigh and first wind-induced regimes.

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

NASA Astrophysics Data System (ADS)

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

2015-11-01

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

Liquid inflow to initially empty cylindrical tanks in low gravity

NASA Technical Reports Server (NTRS)

Spuckler, C. M.

1972-01-01

An experimental investigation was performed to determine the characteristics of liquid inflow to initially empty cylindrical tanks in a low gravity environment. The acceleration was varied so that Bond numbers based on the inlet radius varied from 0.059 to 2.80. The liquid entered the tank as a jet that grew to a maximum height and then decreased in height with respect to the bottom of the tank, with the liquid from the jet collecting in the bottom of the tank. The maximum jet heights were correlated in terms of the Weber number and the Bond number.

Characterization of a Heated Liquid Jet in Crossflow

NASA Astrophysics Data System (ADS)

Wiest, Heather K.

The liquid jet in crossflow (LJICF) is a widely utilized fuel injection method for airbreathing propulsion devices such as low NO x gas turbine combustors, turbojet afterburners, scramjet/ramjet engines, and rotating detonation engines (RDE's). This flow field allows for efficient fuel-air mixing as aerodynamic forces from the crossflow augment atomization. Additionally, increases in the thermal demands of advanced aeroengines necessitates the use of fuel as a primary coolant. The resulting higher fuel temperatures can cause flash atomization of the liquid fuel as it is injected into a crossflow, potentially leading to a large reduction in the jet penetration. While many experimental works have characterized the overall atomization process of a room temperature liquid jet in an ambient temperature and pressure crossflow, the aggressive conditions associated with flash atomization especially in an air crossflow with elevated temperatures and pressures have been less studied in the community. A successful test campaign was conducted to study the effects of fuel temperature on a liquid jet injected transversely into a steady air crossflow at ambient as well as elevated temperature and pressure conditions. Modifications were made to an existing optically accessible rig, and a new fuel injector was designed for this study. Backlit imaging was utilized to record changes in the overall spray characteristics and jet trajectory as fuel temperature and crossflow conditioners were adjusted. Three primary analysis techniques were applied to the heated LJICF data: linear regression of detected edges to determine trajectory correlations, exploratory study of pixel intensity variations both temporally as well as spatially, and modal decomposition of the data. The overall objectives of this study was to assess the trajectory, breakup, and mixing of the LJICF undery varying jet and crossflow conditions, develop a trajectory correlation to predict changes in jet penetration due to fuel temperature increases, and characterize the changes in underlying physics in the LJICF flow field. Based on visual inspection, the increase in fuel temperature leads to a finer and denser fuel spray. With increasingly elevated liquid temperatures, the penetration of the jet typically decreases. At or near flashing conditions, the jet had a tendency to penetrate upstream before bending over in the crossflow as well as experiences a rapid expansion causing the jet column to increase in width. Two trajectory correlations were determined, one for each set of crossflow conditions, based on normalized axial distance, normalized liquid viscosity, and normalized jet diameter as liquid is vaporized. The pixel intensity analysis showed that the highest temperature jet in the ambient temperature and pressure crossflow exhibited periodic behavior that was also found using various modal techniques including proper orthogonal decomposition and dynamic mode decomposition. Dominant frequencies determined for most test cases were associated with the bulk or flapping motion of the jet. Most notably, the DMD analysis in this study was successful in identifying robust modes across different subgroupings of the data even though the modes identified were not the highest power modes in each DMD spectrum.

Blowout Jets: Hinode X-Ray Jets that Don't Fit the Standard Model

NASA Technical Reports Server (NTRS)

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

2010-01-01

Nearly half of all H-alpha macrospicules in polar coronal holes appear to be miniature filament eruptions. This suggests that there is a large class of X-ray jets in which the jet-base magnetic arcade undergoes a blowout eruption as in a CME, instead of remaining static as in most solar X-ray jets, the standard jets that fit the model advocated by Shibata. Along with a cartoon depicting the standard model, we present a cartoon depicting the signatures expected of blowout jets in coronal X-ray images. From Hinode/XRT movies and STEREO/EUVI snapshots in polar coronal holes, we present examples of (1) X-ray jets that fit the standard model, and (2) X-ray jets that do not fit the standard model but do have features appropriate for blowout jets. These features are (1) a flare arcade inside the jet-base arcade in addition to the small flare arcade (bright point) outside that standard jets have, (2) a filament of cool (T is approximately 80,000K) plasma that erupts from the core of the jetbase arcade, and (3) an extra jet strand that should not be made by the reconnection for standard jets but could be made by reconnection between the ambient unipolar open field and the opposite-polarity leg of the filament-carrying flux-rope core field of the erupting jet-base arcade. We therefore infer that these non-standard jets are blowout jets, jets made by miniature versions of the sheared-core-arcade eruptions that make CMEs

Simple and double emulsions via electrospray

NASA Astrophysics Data System (ADS)

Barrero, Antonio; Loscertales, Ignacio G.

2005-11-01

Generation of nanoemulsions is of great interest in medical and pharmaceutical applications; drug delivery or antiviral emulsions are typical examples. The use of electrosprays for dispersing liquids inside liquid insulator baths have been recently reported, (Barrero et al. J. Colloid Interf. Sci. 272, 104, 2004). Capsules, nanotubes and coaxial nanofibers have been obtained from electrified coaxial jets (Loscertales et al. Science 295, n. 5560, 1695, 2002; J. American Chem. Soc. 126, 5376, 2004). Here we present a method for making double emulsions (both water-oil-water and o/w/o) based on the generation of compound electrosprays inside insulator liquid baths. Basically, a conducting liquid injected throughout a capillary needle is electroatomized in cone-jet mode inside a dielectric liquid bath. A third insulating liquid is injected inside the Taylor cone to form a second meniscus. Then, a steady coaxial jet, in which the insulating liquid is coated by the conducting one, develops. A double emulsion forms as a result of the jet breaking up into compound droplets electrically charged. Experimental results carried out with glycerine and different oils in a bath of heptane are reported.

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.

Linear Polarization Properties of Parsec-Scale AGN Jets

NASA Astrophysics Data System (ADS)

Pushkarev, Alexander; Kovalev, Yuri; Lister, Matthew; Savolainen, Tuomas; Aller, Margo; Aller, Hugh; Hodge, Mary

2017-12-01

We used 15 GHz multi-epoch Very Long Baseline Array (VLBA) polarization sensitive observations of 484 sources within a time interval 1996--2016 from the MOJAVE program, and also from the NRAO data archive. We have analyzed the linear polarization characteristics of the compact core features and regions downstream, and their changes along and across the parsec-scale active galactic nuclei (AGN) jets. We detected a significant increase of fractional polarization with distance from the radio core along the jet as well as towards the jet edges. Compared to quasars, BL Lacs have a higher degree of polarization and exhibit more stable electric vector position angles (EVPAs) in their core features and a better alignment of the EVPAs with the local jet direction. The latter is accompanied by a higher degree of linear polarization, suggesting that compact bright jet features might be strong transverse shocks, which enhance magnetic field regularity by compression.

Exotic interactions among C-jets and Pb-jets

NASA Technical Reports Server (NTRS)

1985-01-01

The C-jets and Pb-jets were surveyed on the part of Chacaltaya emulsion chamber No.19 amounting to an exposure of 28.8 sq m yr. It is shown that the adopted events make up an unbiased sample of C-jets for sigma sub E gamma TeV. Mini-Centauro interaction gives the most natural explanation for the eight pinaught-less C-jets with three or more constituent shower core. Out of the eight double-cored pinaught-less events, three are found to have visible invariant masses 1.8 GeV/c. Three Pb-jets-lower are composed of double cores whose respective visible transverse momenta are greater than 0.5 GeV/c, suggesting that they are of Geminion origin or chiron origin. The energies of the parent particles are estimated to be 100 to 200 TeV for all three kinds of events. The implications of this energy estimate and the frequency of observed exotic events are discussed.

Three-dimensional printing-based electro-millifluidic devices for fabricating multi-compartment particles.

PubMed

Chen, Qiu Lan; Liu, Zhou; Shum, Ho Cheung

2014-11-01

In this work, we demonstrate the use of stereolithographic 3D printing to fabricate millifluidic devices, which are used to engineer particles with multiple compartments. As the 3D design is directly transferred to the actual prototype, this method accommodates 3D millimeter-scaled features that are difficult to achieve by either lithographic-based microfabrication or traditional macrofabrication techniques. We exploit this approach to produce millifluidic networks to deliver multiple fluidic components. By taking advantage of the laminar flow, the fluidic components can form liquid jets with distinct patterns, and each pattern has clear boundaries between the liquid phases. Afterwards, droplets with controlled size are fabricated by spraying the liquid jet in an electric field, and subsequently converted to particles after a solidification step. As a demonstration, we fabricate calcium alginate particles with structures of (1) slice-by-slice multiple lamellae, (2) concentric core-shells, and (3) petals surrounding the particle centers. Furthermore, distinct hybrid particles combining two or more of the above structures are also obtained. These compartmentalized particles impart spatially dependent functionalities and properties. To show their applicability, various ingredients, including fruit juices, drugs, and magnetic nanoparticles are encapsulated in the different compartments as proof-of-concepts for applications, including food, drug delivery, and bioassays. Our 3D printed electro-millifluidic approach represents a convenient and robust method to extend the range of structures of functional particles.

Cryogenic Impinging Jets Subjected to High Frequency Transverse Acoustic Forcing in a High Pressure Environment

DTIC Science & Technology

2016-07-27

for liquid propellant atomization in rocket engines1- 2. Liquid rocket engines like the F-1 have successfully used like-on-like impinging jet...impingement of the two cylindrical jets. Another drawback, perhaps the most critical, is that rocket engine using impinging jets sacrifice performance in...The experimental results also suggested that impact waves seem to dominate the atomization process over most of the conditions relevant to rocket

The influence of cavitation in the breakup of liquid free jets

NASA Astrophysics Data System (ADS)

Bode, Juergen

1991-03-01

The interaction between a diesel injection nozzle flow and the atomizing jet was investigated over a wide range of Reynolds numbers. If the pressure gradient towards the centerline of the injection nozzle, generated by the curved streamlines, becomes too large, cavitation occurs at the inlet corner. The cavitation region grows in length and boundary surface with increasing Reynolds number. The instability of the reentry flow causes unsteady fluctuations of the cavitation which influences the breakup of the liquid jet, whereby liquid films are generated which take off from the jet. Cavitation amplifies the mechanism of the atomization, based on the interaction between the jet and surrounding gas. The influence of the cavitation on the atomization is restricted to the region directly behind the nozzle exit. The injection pressure and the temperature of the gas hardly affect the atomization. The jet angle depends mainly on the density of the surrounding gas.

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.

Axial and radial nanostructures in electrospun polymer fibers

NASA Astrophysics Data System (ADS)

Greenfeld, Israel; Camposeo, Andrea; Tantussi, Francesco; Pagliara, Stefano; Fuso, Francesco; Allegrini, Maria; Pisignano, Dario; Zussman, Eyal

2013-03-01

The high tensional stresses during electrospinning of semidilute polymer solutions affect the dynamic conformation of the polymer network within the liquid jet, leaving a distinctive trace in the molecular structure after solidification. We investigated such effects in electrospun nanofibers made of conjugated polymers. Modeling the polymer network evolution during electrospinning showed that as the network stretches axially, it contracts towards the jet core. The model represents the semi-flexible conjugated polymer chains as flexible freely-jointed chains, whose joints are bonding defects. Using the conjugated polymer MEH-PPV dissolved in a mixture of THF and DMF solvents, and taking advantage of its unique photophysical characteristics, we investigated optically the variations in the density and orientation of the polymer macromolecules in electrospun nanofibers. In agreement with our model, we found higher density and axial orientation at the fiber core, while lower density and radial orientation closer to the fiber surface. The non-uniformity of the resulting molecular structure can be tuned and exploited in diverse optical and structural applications. We acknowledge: V. Fasano, G. Potente, S. Girardo and E. Caldi for assistance in measurements; United States-Israel BSF, RBNI Institute, and the Israel Science Foundation for financial support.

Acoustically Forced Coaxial Hydrogen / Liquid Oxygen Jet Flames

DTIC Science & Technology

2016-05-15

serious problems in the development of liquid rocket engines. In order to understand and predict them, it is necessary to understand how representative...liquid rocket injector flames react to acoustic waves. In this study, a representative coaxial gaseous hydrogen / liquid oxygen (LOX) jet flame is...Combustion instabilities can pose serious problems in the development of liquid rocket engines. In order to under- stand and predict them, it is

Impact of Fluidic Chevrons on Supersonic Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Norum, Thomas

2007-01-01

The impact of fluidic chevrons on broadband shock noise and mixing noise for single stream and coannular jets was investigated. Air was injected into the core flow of a bypass ratio 5 nozzle system using a core fluidic chevron nozzle. For the single stream experiments, the fan stream was operated at the wind tunnel conditions and the core stream was operated at supersonic speeds. For the dual stream experiments, the fan stream was operated at supersonic speeds and the core stream was varied between subsonic and supersonic conditions. For the single stream jet at nozzle pressure ratio (NPR) below 2.0, increasing the injection pressure of the fluidic chevron increased high frequency noise at observation angles upstream of the nozzle exit and decreased mixing noise near the peak jet noise angle. When the NPR increased to a point where broadband shock noise dominated the acoustic spectra at upstream observation angles, the fluidic chevrons significantly decreased this noise. For dual stream jets, the fluidic chevrons reduced broadband shock noise levels when the fan NPR was below 2.3, but had little or no impact on shock noise with further increases in fan pressure. For all fan stream conditions investigated, the fluidic chevron became more effective at reducing mixing noise near the peak jet noise angle as the core pressure increased.

Plasma flow patterns in and around magnetosheath jets

NASA Astrophysics Data System (ADS)

Plaschke, Ferdinand; Hietala, Heli

2018-05-01

The magnetosheath is commonly permeated by localized high-speed jets downstream of the quasi-parallel bow shock. These jets are much faster than the ambient magnetosheath plasma, thus raising the question of how that latter plasma reacts to incoming jets. We have performed a statistical analysis based on 662 cases of one THEMIS spacecraft observing a jet and another (second) THEMIS spacecraft providing context observations of nearby plasma to uncover the flow patterns in and around jets. The following results are found: along the jet's path, slower plasma is accelerated and pushed aside ahead of the fastest core jet plasma. Behind the jet core, plasma flows into the path to fill the wake. This evasive plasma motion affects the ambient magnetosheath, close to the jet's path. Diverging and converging plasma flows ahead and behind the jet are complemented by plasma flows opposite to the jet's propagation direction, in the vicinity of the jet. This vortical plasma motion results in a deceleration of ambient plasma when a jet passes nearby.

Development of a Jet Noise Prediction Method for Installed Jet Configurations

NASA Technical Reports Server (NTRS)

Hunter, Craig A.; Thomas, Russell H.

2003-01-01

This paper describes development of the Jet3D noise prediction method and its application to heated jets with complex three-dimensional flow fields and installation effects. Noise predictions were made for four separate flow bypass ratio five nozzle configurations tested in the NASA Langley Jet Noise Laboratory. These configurations consist of a round core and fan nozzle with and without pylon, and an eight chevron core nozzle and round fan nozzle with and without pylon. Predicted SPL data were in good agreement with experimental noise measurements up to 121 inlet angle, beyond which Jet3D under predicted low frequency levels. This is due to inherent limitations in the formulation of Lighthill's Acoustic Analogy used in Jet3D, and will be corrected in ongoing development. Jet3D did an excellent job predicting full scale EPNL for nonchevron configurations, and captured the effect of the pylon, correctly predicting a reduction in EPNL. EPNL predictions for chevron configurations were not in good agreement with measured data, likely due to the lower mixing and longer potential cores in the CFD simulations of these cases.

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.

Supersonic Injection of Aerated Liquid Jet

NASA Astrophysics Data System (ADS)

Choudhari, Abhijit; Sallam, Khaled

2016-11-01

A computational study of the exit flow of an aerated two-dimensional jet from an under-expanded supersonic nozzle is presented. The liquid sheet is operating within the annular flow regime and the study is motivated by the application of supersonic nozzles in air-breathing propulsion systems, e.g. scramjet engines, ramjet engines and afterburners. The simulation was conducted using VOF model and SST k- ω turbulence model. The test conditions included: jet exit of 1 mm and mass flow rate of 1.8 kg/s. The results show that air reaches transonic condition at the injector exit due to the Fanno flow effects in the injector passage. The aerated liquid jet is alternately expanded by Prandtl-Meyer expansion fan and compressed by oblique shock waves due to the difference between the back (chamber) pressure and the flow pressure. The process then repeats itself and shock (Mach) diamonds are formed at downstream of injector exit similar to those typical of exhaust plumes of propulsion system. The present results, however, indicate that the flow field of supersonic aerated liquid jet is different from supersonic gas jets due to the effects of water evaporation from the liquid sheet. The contours of the Mach number, static pressure of both cases are compared to the theory of gas dynamics.

Impact of a single drop on the same liquid: formation, growth and disintegration of jets

NASA Astrophysics Data System (ADS)

Agbaglah, G. Gilou; Deegan, Robert

2015-11-01

One of the simplest splashing scenarios results from the impact of a single drop on on the same liquid. The traditional understanding of this process is that the impact generates a jet that later breaks up into secondary droplets. Recently it was shown that even this simplest of scenarios is more complicated than expected because multiple jets can be generated from a single impact event and there are bifurcations in the multiplicity of jets. First, we study the formation, growth and disintegration of jets following the impact of a drop on a thin film of the same liquid using a combination of numerical simulations and linear stability theory. We obtain scaling relations from our simulations and use these as inputs to our stability analysis. We also use experiments and numerical simulations of a single drop impacting on a deep pool to examine the bifurcation from a single jet into two jets. Using high speed X-ray imaging methods we show that vortex separation within the drop leads to the formation of a second jet long after the formation of the ejecta sheet.

Columnar Transitions in Microscale Evaporating Liquid Jets

NASA Astrophysics Data System (ADS)

Hunter, Hanif; Glezer, Ari

2007-11-01

Microscale evaporating liquid jets that are injected into a quiescent gaseous medium having adjustable ambient pressure are investigated over a range of jet speeds using a shadowgraph technique. The jets are formed by a laser-drilled 10 μm nozzle from a small-scale pressurized reservoir, and sub-atmospheric ambient pressure is maintained using a controllable, metered Venturi pump. The near-field jet features are captured by shadowgraph imaging using a pulsed ND-Yag laser and a 12 bit CCD camera where the field of view measured 200 μm on the side. As the ambient pressure is reduced, the jet column undergoes a series of spectacular transitions that are first marked by the appearance of vapor bubbles within the jet column. The transitions progress from columnar instabilities to series of column bifurcations to high-order branching and film formation and culminate in conical atomization of the jet column. In addition to the effects of the ambient pressure, the present investigation also considers effects of the liquid surface tension and vapor pressure on the onset, evolution, and hysteresis of the columnar transitions.

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...

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

PubMed

Guo, Yuchen; Green, Sheldon

2015-04-17

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.

Control of ROS and RNS productions in liquid in atmospheric pressure plasma-jet system

NASA Astrophysics Data System (ADS)

Uchida, Giichiro; Ito, Taiki; Takenaka, Kosuke; Ikeda, Junichiro; Setsuhara, Yuichi

2016-09-01

Non-thermal plasma jets are of current interest in biomedical applications such as wound disinfection and even treatment of cancer tumors. Beneficial therapeutic effects in medical applications are attributed to excited species of oxygen and nitrogen from air. However, to control the production of these species in the plasma jet is difficult because their production is strongly dependent on concentration of nitrogen and oxygen from ambient air into the plasma jet. In this study, we analyze the discharge characteristics and the ROS and RNS productions in liquid in low- and high-frequency plasma-jet systems. Our experiments demonstrated the marked effects of surrounding gas near the plasma jet on ROS and RNS productions in liquid. By controlling the surround gas, the O2 and N2 main plasma jets are selectively produced even in open air. We also show that the concentration ratio of NO2- to H2O2 in liquid is precisely tuned from 0 to 0.18 in deionized water by changing N2 gas ratio (N2 / (N2 +O2)) in the main discharge gas, where high NO2- ratio is obtained at N2 gas ratio at N2 / (N2 +O2) = 0 . 8 . The low-frequency plasma jet with controlled surrounding gas is an effective plasma source for ROS and RNS productions in liquid, and can be a useful tool for biomedical applications. This study was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ``Plasma Medical Innovation'' (24108003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

PubMed Central

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

Analytical and experimental studies of impinging liquid jets

NASA Technical Reports Server (NTRS)

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

1994-01-01

Impinging injectors are a common type of injector used in liquid propellant rocket engines and are typically used in engines where both propellants are injected as a liquid, e.g., engines using LOX/hydrocarbon and storable propellant combinations. The present research program is focused on providing the requisite fundamental understanding associated with impinging jet injectors for the development of an advanced a priori combustion stability design analysis capability. To date, a systematic study of the atomization characteristics of impinging liquid jets under cold-flow conditions have been completed. Effects of orifice diameter, impingement angle, pre-impingement length, orifice length-to-diameter ratio, fabrication procedure, jet flow condition and jet velocity under steady and oscillating, and atmospheric- and high-pressure environments have been investigated. Results of these experimental studies have been compared to current models of sheet breakup and drop formation. In addition, the research findings have been scrutinized to provide a fundamental explanation for a proven empirical correlation used in the design of stable impinging injector-based rocket engines.

An optical technique for detecting minute-amplitude standing waves on a liquid jet

NASA Astrophysics Data System (ADS)

Takahashi, I.; Mori, Y. H.

1995-10-01

A liquid jet emerging from a nozzle or an orifice whose outlet is slightly elliptic has a series of minute-amplitude waves on its surface. A quite simple technique is proposed which enables detecting such waves even if they are no longer recognizable with the aid of ordinary backlighting of the jet.

Jet Propellant 8 versus Alternative Jet Fuels: A Life-Cycle Perspective

DTIC Science & Technology

2011-01-01

United States imports.26 The CBTL process uses three existing technologies to convert coal and biomass into liquid fuel: gasification , FT synthesis...and carbon capture and storage. Gasification converts coal and biomass into CO and H2, a mixture commonly referred to as “syngas.” FT synthesis...com- pare petroleum-derived jet fuel (i.e., JP-8) to an alternative jet fuel derived from a coal- biomass -to-liquid (CBTL) process. The EIO- LCA

Experimental study of elliptical jet from supercritical to subcritical conditions using planar laser induced fluorescence

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

Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in

2015-03-15

The study of fluid jet dynamics at supercritical conditions involves strong coupling between fluid dynamic and thermodynamic phenomena. Beyond the critical point, the liquid-vapor coexistence ceases to exist, and the fluid exists as a single phase known as supercritical fluid with its properties that are entirely different from liquids and gases. At the critical point, the liquids do not possess surface tension and latent heat of evaporation. Around the critical point, the fluid undergoes large changes in density and possesses thermodynamic anomaly like enhancement in thermal conductivity and specific heat. In the present work, the transition of the supercritical andmore » near-critical elliptical jet into subcritical as well as supercritical environment is investigated experimentally with nitrogen and helium as the surrounding environment. Under atmospheric condition, a liquid jet injected from the elliptical orifice exhibits axis switching phenomena. As the injection temperature increases, the axis switching length also increases. Beyond the critical temperature, the axis switching is not observed. The investigation also revealed that pressure plays a major role in determining the thermodynamic transition of the elliptical jet only for the case of supercritical jet injected into subcritical chamber conditions. At larger pressures, the supercritical jet undergoes disintegration and formation of droplets in the subcritical environment is observed. However, for supercritical jet injection into supercritical environment, the gas-gas like mixing behavior is observed.« less

Constraining high-energy neutrino emission from choked jets in stripped-envelope supernovae

NASA Astrophysics Data System (ADS)

Senno, Nicholas; Murase, Kohta; Mészáros, Peter

2018-01-01

There are indications that γ-ray dark objects such as supernovae (SNe) with choked jets, and the cores of active galactic nuclei may contribute to the diffuse flux of astrophysical neutrinos measured by the IceCube observatory. In particular, stripped-envelope SNe have received much attention since they are capable of producing relativistic jets and could explain the diversity in observations of collapsar explosions (e.g., gamma-ray bursts (GRBs), low-luminosity GRBs, and Type Ibc SNe). We use an unbinned maximum likelihood method to search for spatial and temporal coincidences between Type Ibc core-collapse SNe, which may harbor a choked jet, and muon neutrinos from a sample of IceCube up-going track-like events measured from May 2011–May 2012. In this stacking analysis, we find no significant deviation from a background-only hypothesis using one year of data, and are able to place upper limits on the total amount of isotropic equivalent energy that choked jet core-collapse SNe deposit in cosmic rays Script Ecr and the fraction of core-collapse SNe which have a jet pointed towards Earth fjet. This analysis can be extended with yet to be made public IceCube data, and the increased amount of optically detected core-collapse SNe discovered by wide field-of-view surveys such as the Palomar Transient Factory and All-Sky Automated Survey for Supernovae. The choked jet SNe/high-energy cosmic neutrino connection can be more tightly constrained in the near future.

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.

Experimental Characterization of the Jet Wiping Process

NASA Astrophysics Data System (ADS)

Mendez, Miguel Alfonso; Enache, Adriana; Gosset, Anne; Buchlin, Jean-Marie

2018-06-01

This paper presents an experimental characterization of the jet wiping process, used in continuous coating applications to control the thickness of a liquid coat using an impinging gas jet. Time Resolved Particle Image Velocimetry (TR-PIV) is used to characterize the impinging gas flow, while an automatic interface detection algorithm is developed to track the liquid interface at the impact. The study of the flow interaction is combined with time resolved 3D thickness measurements of the liquid film remaining after the wiping, via Time Resolved Light Absorption (TR-LAbs). The simultaneous frequency analysis of liquid and gas flows allows to correlate their respective instability, provide an experimental data set for the validation of numerical studies and allows for formulating a working hypothesis on the origin of the coat non-uniformity encountered in many jet wiping processes.

Micrometer-thickness liquid sheet jets flowing in vacuum

NASA Astrophysics Data System (ADS)

Galinis, Gediminas; Strucka, Jergus; Barnard, Jonathan C. T.; Braun, Avi; Smith, Roland A.; Marangos, Jon P.

2017-08-01

Thin liquid sheet jet flows in vacuum provide a new platform for performing experiments in the liquid phase, for example X-ray spectroscopy. Micrometer thickness, high stability, and optical flatness are the key characteristics required for successful exploitation of these targets. A novel strategy for generating sheet jets in vacuum is presented in this article. Precision nozzles were designed and fabricated using high resolution (0.2 μm) 2-photon 3D printing and generated 1.49 ± 0.04 μm thickness, stable, and <λ /20-flat jets in isopropanol under normal atmosphere and under vacuum at 5 × 10-1 mbar. The thin sheet technology also holds great promise for advancing the fields of high harmonic generation in liquids, laser acceleration of ions as well as other fields requiring precision and high repetition rate targets.

Discharge characteristics and hydrodynamics behaviors of atmospheric plasma jets produced in various gas flow patterns

NASA Astrophysics Data System (ADS)

Setsuhara, Yuichi; Uchida, Giichiro; Nakajima, Atsushi; Takenaka, Kosuke; Koga, Kazunori; Shiratani, Masaharu

2015-09-01

Atmospheric nonequilibrium plasma jets have been widely employed in biomedical applications. For biomedical applications, it is an important issue to understand the complicated mechanism of interaction of the plasma jet with liquid. In this study, we present analysis of the discharge characteristics of a plasma jet impinging onto the liquid surface under various gas flow patterns such as laminar and turbulence flows. For this purpose, we analyzed gas flow patters by using a Schlieren gas-flow imaging system in detail The plasma jet impinging into the liquid surface expands along the liquid surface. The diameter of the expanded plasma increases with gas flow rate, which is well explained by an increase in the diameter of the laminar gas-flow channel. When the gas flow rate is further increased, the gas flow mode transits from laminar to turbulence in the gas flow channel, which leads to the shortening of the plasm-jet length. Our experiment demonstrated that the gas flow patterns strongly affect the discharge characteristics in the plasma-jet system. This study was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ``Plasma Medical Innovation'' (24108003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

Fabrication of micro/nano-structures by electrohydrodynamic jet technique

NASA Astrophysics Data System (ADS)

Wang, Dazhi; Zhao, Xiaojun; Lin, Yigao; Ren, Tongqun; Liang, Junsheng; Liu, Chong; Wang, Liding

2017-12-01

Electrohydrodynamic jet (E-Jet) is an approach to the fabrication of micro/nano-structures by the use of electrical forces. In this process, the liquid is subjected to electrical and mechanical forces to form a liquid jet, which is further disintegrated into droplets. The major advantage of the E-Jet technique is that the sizes of the jet formed can be at the nanoscale far smaller than the nozzle size, which can realize high printing resolution with less risk of nozzle blockage. The E-Jet technique, which mainly includes E-Jet deposition and E-Jet printing, has a wide range of applications in the fabrication of micro/nano-structures for micro/nano-electromechanical system devices. This technique is also considered a micro/nano-fabrication method with a great potential for commercial use. This study mainly reviews the E-Jet deposition/printing fundamentals, fabrication process, and applications.

Jet impact on a soap film

NASA Astrophysics Data System (ADS)

Kirstetter, Geoffroy; Raufaste, Christophe; Celestini, Franck

2012-09-01

We experimentally investigate the impact of a liquid jet on a soap film. We observe that the jet never breaks the film and that two qualitatively different steady regimes may occur. The first one is a refractionlike behavior obtained at small incidence angles when the jet crosses the film and is deflected by the film-jet interaction. For larger incidence angles, the jet is absorbed by the film, giving rise to a new class of flows in which the jet undulates along the film with a characteristic wavelength. Besides its fundamental interest, this paper presents a different way to guide a micrometric flow of liquid in the inertial regime and to probe foam stability submitted to violent perturbations at the soap film scale.

Jet impact on a soap film.

PubMed

Kirstetter, Geoffroy; Raufaste, Christophe; Celestini, Franck

2012-09-01

We experimentally investigate the impact of a liquid jet on a soap film. We observe that the jet never breaks the film and that two qualitatively different steady regimes may occur. The first one is a refractionlike behavior obtained at small incidence angles when the jet crosses the film and is deflected by the film-jet interaction. For larger incidence angles, the jet is absorbed by the film, giving rise to a new class of flows in which the jet undulates along the film with a characteristic wavelength. Besides its fundamental interest, this paper presents a different way to guide a micrometric flow of liquid in the inertial regime and to probe foam stability submitted to violent perturbations at the soap film scale.

The liquid fuel jet in subsonic crossflow

NASA Technical Reports Server (NTRS)

Nguyen, T. T.; Karagozian, A. R.

1990-01-01

An analytical/numerical model is described which predicts the behavior of nonreacting and reacting liquid jets injected transversely into subsonic cross flow. The compressible flowfield about the elliptical jet cross section is solved at various locations along the jet trajectory by analytical means for free-stream local Mach number perpendicular to jet cross section smaller than 0.3 and by numerical means for free-stream local Mach number perpendicular to jet cross section in the range 0.3-1.0. External and internal boundary layers along the jet cross section are solved by integral and numerical methods, and the mass losses due to boundary layer shedding, evaporation, and combustion are calculated and incorporated into the trajectory calculation. Comparison of predicted trajectories is made with limited experimental observations.

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).

Fluid sampling system

DOEpatents

Houck, Edward D.

1994-01-01

An fluid sampling system allows sampling of radioactive liquid without spillage. A feed tank is connected to a liquid transfer jet powered by a pumping chamber pressurized by compressed air. The liquid is pumped upwardly into a sampling jet of a venturi design having a lumen with an inlet, an outlet, a constricted middle portion, and a port located above the constricted middle portion. The liquid is passed under pressure through the constricted portion causing its velocity to increase and its pressure to decreased, thereby preventing liquid from escaping. A septum sealing the port can be pierced by a two pointed hollow needle leading into a sample bottle also sealed by a pierceable septum affixed to one end. The bottle is evacuated by flow through the sample jet, cyclic variation in the sampler jet pressure periodically leaves the evacuated bottle with lower pressure than that of the port, thus causing solution to pass into the bottle. The remaining solution in the system is returned to the feed tank via a holding tank.

Fluid sampling system

DOEpatents

Houck, E.D.

1994-10-11

An fluid sampling system allows sampling of radioactive liquid without spillage. A feed tank is connected to a liquid transfer jet powered by a pumping chamber pressurized by compressed air. The liquid is pumped upwardly into a sampling jet of a venturi design having a lumen with an inlet, an outlet, a constricted middle portion, and a port located above the constricted middle portion. The liquid is passed under pressure through the constricted portion causing its velocity to increase and its pressure to be decreased, thereby preventing liquid from escaping. A septum sealing the port can be pierced by a two pointed hollow needle leading into a sample bottle also sealed by a pierceable septum affixed to one end. The bottle is evacuated by flow through the sample jet, cyclic variation in the sampler jet pressure periodically leaves the evacuated bottle with lower pressure than that of the port, thus causing solution to pass into the bottle. The remaining solution in the system is returned to the feed tank via a holding tank. 4 figs.

Electric-field driven jetting from dielectric liquids

NASA Astrophysics Data System (ADS)

Jayasinghe, S. N.; Edirisinghe, M. J.

2004-11-01

Three dielectric (electrical conductivity ˜10-13Sm-1) Newtonian liquids with viscosity in the range 1-100 mPa s were passed through a needle at a controlled flow rate under the influence of an electric field. At an electric field strength of 1.5kV/mm, the liquid exiting the needle instantaneously transformed from dripping droplets to an elliptically pendent droplet from the apex of which a fine jet evolved. Thus, a jet can be obtained on demand, and in this letter we define this phenomenon and explain a basis for it.

A new method of producing local enhancement of buoyancy in liquid flows

NASA Astrophysics Data System (ADS)

Bhat, G. S.; Narasimha, R.; Arakeri, V. H.

1989-11-01

We describe here a novel method of generating large volumetric heating in a liquid. The method uses the principle of ohmic heating of the liquid, rendered electrically conducting by suitable additives if necessary. Electrolysis is prevented by the use of high frequency alternating voltage and chemically treated electrodes. The technique is demonstrated by producing substantial heating in an initially neutral jet of water. Simple flow visualisation studies, made by adding dye to the jet, show marked changes in the growth and development of the jet with heat addition.

Stabilizing effect of elasticity on the inertial instability of submerged viscoelastic liquid jets

NASA Astrophysics Data System (ADS)

Keshavarz, Bavand; McKinley, Gareth

2017-11-01

The stability of submerged Newtonian and viscoelastic liquid jets is studied experimentally using flow visualization. Precise control of the amplitude and frequency of the imposed linear perturbations is achieved through a piezoelectric actuator attached to the nozzle. By illuminating the jet with a strobe light driven at a frequency slightly less than the frequency of the perturbation we slow down the apparent motion by large factors ( 100 , 000) and capture the phenomena with high temporal and spatial resolution. Newtonian liquid jets become unstable at moderate Reynolds numbers (Rej 150) and sinuous or varicose patterns emerge and grow in amplitude. As the jet moves downstream, the varicose waves gradually pile up in the sinuous ones due to the difference in their corresponding wave speeds, leading to a unique chevron-like morphology. Experiments with model viscoelastic polymer solutions show that this inertial instability is fully stabilized sufficiently large levels of elasticity. We compare our experimental results with the theoretical predictions of an elastic Rayleigh equation for an axisymmetric jet and show that the presence of streamline tension is indeed the stabilizing effect for inertioelastic jets.

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.

Closed-form model for the analysis of W-type shaped charges

NASA Astrophysics Data System (ADS)

Mahdian, A.; Ghayour, M.; Liaghat, G. H.

2013-09-01

This paper presents a closed-form model for the analysis of symmetric planar W-type shaped charges (WSCs) with two V-sections, which produce two primary cores and two primary jets. If these two V-sections have proper asymmetry, these primary cores will force two primary jets into a secondary core formed on the axis of symmetry of a planar symmetric WSC. For the analysis of such a planar WSC, a complete generalized model for an asymmetric planar V-shaped charge (VSC) with any desired order of asymmetry is mandatory. In this paper, the model is applied to describe the secondary jet formation in the WSC. By presenting a closed-form analysis of the WSC, the secondary jet specifications can be easily evaluated and, thus, can be compared with respect to the jet quantities in symmetric or asymmetric VSCs. Finally, for the primary and secondary jets, the coherency conditions are investigated, and the critical parameters responsible for these conditions are determined.

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.

Radio jets in NGC 4151: where eMERLIN meets HST

NASA Astrophysics Data System (ADS)

Williams, D. R. A.; McHardy, I. M.; Baldi, R. D.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Fenech, D. M.; Mundell, C. G.; Muxlow, T. W. B.; Panessa, F.; Rampadarath, H.; Westcott, J.

2017-12-01

We present high-sensitivity eMERLIN radio images of the Seyfert galaxy NGC 4151 at 1.51 GHz. We compare the new eMERLIN images to those from archival MERLIN observations in 1993 to determine the change in jet morphology in the 22 yr between observations. We report an increase by almost a factor of 2 in the peak flux density of the central core component, C4, thought to host the black hole, but a probable decrease in some other components, possibly due to adiabatic expansion. The core flux increase indicates an active galactic nucleus (AGN) that is currently active and feeding the jet. We detect no significant motion in 22 yr between C4 and the component C3, which is unresolved in the eMERLIN image. We present a spectral index image made within the 512 MHz band of the 1.51 GHz observations. The spectrum of the core, C4, is flatter than that of other components further out in the jet. We use HST emission-line images (H α, [O III] and [O II]) to study the connection between the jet and the emission-line region. Based on the changing emission-line ratios away from the core and comparison with the eMERLIN radio jet, we conclude that photoionization from the central AGN is responsible for the observed emission-line properties further than 4 arcsec (360 pc) from the core, C4. Within this region, a body of evidence (radio-line co-spatiality, low [O III]/H α and estimated fast shocks) suggests additional ionization from the jet.

Numerical modelling of heat transfer in a cavity due to liquid jet impingement for liquid supported stretch blow moulding

NASA Astrophysics Data System (ADS)

Smyth, Trevor; Menary, Gary; Geron, Marco

2018-05-01

Impingement of a liquid jet in a polymer cavity has been modelled numerically in this study. Liquid supported stretch blow moulding is a nascent polymer forming process using liquid as the forming medium to produce plastic bottles. The process derives from the conventional stretch blow moulding process which uses compressed air to deform the preform. Heat transfer away from the preform greatly increases when a liquid instead of a gas is flowing over a solid; in the blow moulding process the temperature of the preform is tightly controlled to achieve optimum forming conditions. A model was developed with Computational Fluid Dynamics code ANSYS Fluent which allows the extent of heat transfer between the incoming liquid and the solid preform to be determined in the initial transient stage, where a liquid jet enters an air filled preform. With this data, an approximation of the extent of cooling through the preform wall can be determined.

[Study on the fluctuation phenomena of arc plasma spraying jet].

PubMed

Zhao, Wen-hua; Liu, Di; Tian, Kuo

2002-08-01

The turbulence phenomenon is one of the most attractive characteristics of a DC arc plasma spraying jet. Most of the previous investigations believe that there is a laminar flow region in core of the jet. A spectrum diagnostic system has been built up in this paper to investigate these effects with the aid of high-speed digital camera. The FFT method has been applied to the analysis on the arc voltage and light signals. The influence of the arc behavior and the power supply on the jet is full-scale. It seems that there is not a laminar flow region in core of the jet. Moreover, from the light dynamic variation graph, the jet fluctuation due to the arc voltage behavior maybe is the dominant characteristic of the jet behavior.

Interfacial condensation induced by sub-cooled liquid jet

NASA Astrophysics Data System (ADS)

Rame, Enrique; Balasubramaniam, R.

2016-11-01

When a sub-cooled liquid jet impinges on the free surface between a liquid and its vapor, vapor will condense at a rate dependent on the sub-cooling, the jet strength and fluid properties. In 1966 and during the examination of a different type of condensation flow, Shekriladeze found an approximate result, valid at large condensation rates, that decouples the flow in the liquid phase from that of the vapor, without putting it in the context of a formal asymptotic approximation. In this talk we will develop an asymptotic approximation that contains Shekriladze's result, and extend the calculations to the case when a non-condensable gas is present in the vapor phase.

Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

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

Nishikawa, K.-I.; Hardee, P. E.; Duţan, I.

2014-09-20

We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shearmore » surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.« less

In situ x-ray diffraction measurements of the capillary fountain jet produced via ultrasonic atomization.

PubMed

Yano, Yohko F; Douguchi, Junya; Kumagai, Atsushi; Iijima, Takao; Tomida, Yukinobu; Miyamoto, Toshiaki; Matsuura, Kazuo

2006-11-07

In situ x-ray diffraction measurements were carried out for investigating the liquid structure in the ultrasonic fountain jet to consider the mechanism of the "ultrasonic ethanol separation" reported by Sato et al. [J. Chem. Phys. 114, 2382 (2001)]. For pure liquids (water and ethanol), it was found that the high frequency ultrasound does not affect the liquid structure microscopically. For the 20 mol % ethanol-water mixture, the estimated ethanol mole fraction in the ultrasonic fountain jet by using the position of the main maximum in the x-ray diffraction profile coincided with that in the reservoir. This result suggests that the ethanol separation is not caused by any distorted liquid structure under the ultrasound irradiation and occurs when or after the generation of the liquid droplet mist.

In situ x-ray diffraction measurements of the capillary fountain jet produced via ultrasonic atomization

NASA Astrophysics Data System (ADS)

Yano, Yohko F.; Douguchi, Junya; Kumagai, Atsushi; Iijima, Takao; Tomida, Yukinobu; Miyamoto, Toshiaki; Matsuura, Kazuo

2006-11-01

In situ x-ray diffraction measurements were carried out for investigating the liquid structure in the ultrasonic fountain jet to consider the mechanism of the "ultrasonic ethanol separation" reported by Sato et al. [J. Chem. Phys. 114, 2382 (2001)]. For pure liquids (water and ethanol), it was found that the high frequency ultrasound does not affect the liquid structure microscopically. For the 20mol% ethanol-water mixture, the estimated ethanol mole fraction in the ultrasonic fountain jet by using the position of the main maximum in the x-ray diffraction profile coincided with that in the reservoir. This result suggests that the ethanol separation is not caused by any distorted liquid structure under the ultrasound irradiation and occurs when or after the generation of the liquid droplet mist.

The mechanism of liquid metal jet formation in the cathode spot of vacuum arc discharge

NASA Astrophysics Data System (ADS)

Gashkov, M. A.; Zubarev, N. M.; Mesyats, G. A.; Uimanov, I. V.

2016-08-01

We have theoretically studied the dynamics of molten metal during crater formation in the cathode spot of vacuum arc discharge. At the initial stage, a liquid-metal ridge is formed around the crater. This process has been numerically simulated in the framework of the two-dimensional axisymmetric heat and mass transfer problem in the approximation of viscous incompressible liquid. At a more developed stage, the motion of liquid metal loses axial symmetry, which corresponds to a tendency toward jet formation. The development of azimuthal instabilities of the ridge is analyzed in terms of dispersion relations for surface waves. It is shown that maximum increments correspond to instability of the Rayleigh-Plateau type. Estimations of the time of formation of liquid metal jets and their probable number are obtained.

Leaping shampoo glides on a lubricating air layer

NASA Astrophysics Data System (ADS)

Lee, S.; Li, E. Q.; Marston, J. O.; Bonito, A.; Thoroddsen, S. T.

2013-06-01

When a stream of shampoo is fed onto a pool in one's hand, a jet can leap sideways or rebound from the liquid surface in an intriguing phenomenon known as the Kaye effect. Earlier studies have debated whether non-Newtonian effects are the underlying cause of this phenomenon, making the jet glide on top of a shear-thinning liquid layer, or whether an entrained air layer is responsible. Herein we show unambiguously that the jet slides on a lubricating air layer. We identify this layer by looking through the pool liquid and observing its rupture into fine bubbles. The resulting microbubble sizes suggest this air layer is of submicron thickness. This thickness estimate is also supported by the tangential deceleration of the jet during the rebounding.

Leaping shampoo glides on a lubricating air layer.

PubMed

Lee, S; Li, E Q; Marston, J O; Bonito, A; Thoroddsen, S T

2013-06-01

When a stream of shampoo is fed onto a pool in one's hand, a jet can leap sideways or rebound from the liquid surface in an intriguing phenomenon known as the Kaye effect. Earlier studies have debated whether non-Newtonian effects are the underlying cause of this phenomenon, making the jet glide on top of a shear-thinning liquid layer, or whether an entrained air layer is responsible. Herein we show unambiguously that the jet slides on a lubricating air layer. We identify this layer by looking through the pool liquid and observing its rupture into fine bubbles. The resulting microbubble sizes suggest this air layer is of submicron thickness. This thickness estimate is also supported by the tangential deceleration of the jet during the rebounding.

Mixing and transient interface condensation of a liquid hydrogen tank

NASA Technical Reports Server (NTRS)

Lin, C. S.; Hasan, M. M.; Nyland, T. W.

1993-01-01

Experiments were conducted to investigate the effect of axial jet-induced mixing on the pressure reduction of a thermally stratified liquid hydrogen tank. The tank was nearly cylindrical, having a volume of about 0.144 cu m with 0.559 m in diameter and 0.711 m long. A mixer/pump unit, which had a jet nozzle outlet of 0.0221 m in diameter was located 0.178 m from the tank bottom and was installed inside the tank to generate the axial jet mixing and tank fluid circulation. The liquid fill and jet flow rate ranged from 42 to 85 percent (by volume) and 0.409 to 2.43 cu m/hr, respectively. Mixing tests began with the tank pressure ranging from 187.5 to 238.5 kPa at which the thermal stratification results in 4.9 to 6.2 K liquid sub cooling. The mixing time and transient vapor condensation rate at the liquid-vapor interface are determined. Two mixing time correlations, based on the thermal equilibrium and pressure equilibrium, are developed. Both mixing time correlations are expressed as functions of system and buoyancy parameters and compared well with other experimental data. The steady state condensation rate correlation of Sonin et al. based on steam-water data is modified and expressed as a function of jet subcooling. The limited liquid hydrogen data of the present study shows that the modified steady state condensation rate correlation may be used to predict the transient condensation rate in a mixing process if the instantaneous values of jet sub cooling and turbulence intensity at the interface are employed.

Effects of irradiation distance on supply of reactive oxygen species to the bottom of a Petri dish filled with liquid by an atmospheric O{sub 2}/He plasma jet

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

Kawasaki, Toshiyuki, E-mail: kawasaki@nbu.ac.jp; Kusumegi, Shota; Kudo, Akihiro

The impact of irradiation distances on plasma jet-induced specific effects on the supply of reactive oxygen species (ROS) to the bottom of a Petri dish filled with liquid was investigated using a KI-starch gel reagent that can be employed as a ROS indicator even in water. O{sub 3} exposure experiments without plasma irradiation were also performed to elucidate the specific effects of the plasma jet. Relative concentrations of ROS transported to the bottom were evaluated using absorbance measurements. The results indicated that ROS supply to the bottom is markedly enhanced by the plasma jet irradiation at shorter irradiation distances, whereasmore » similar results could not be obtained for the O{sub 3} exposure. In these cases, the liquid mixing in the depth direction was also enhanced by the plasma jet irradiation only, and the supply of reactive atomic oxygen to the liquid surface was markedly increased as well.« less

AC electrified jets in a flow-focusing device: Jet length scaling

PubMed Central

García-Sánchez, Pablo; Alzaga-Gimeno, Javier; Baret, Jean-Christophe

2016-01-01

We use a microfluidic flow-focusing device with integrated electrodes for controlling the production of water-in-oil drops. In a previous work, we reported that very long jets can be formed upon application of AC fields. We now study in detail the appearance of the long jets as a function of the electrical parameters, i.e., water conductivity, signal frequency, and voltage amplitude. For intermediate frequencies, we find a threshold voltage above which the jet length rapidly increases. Interestingly, this abrupt transition vanishes for high frequencies of the signal and the jet length grows smoothly with voltage. For frequencies below a threshold value, we previously reported a transition from a well-behaved uniform jet to highly unstable liquid structures in which axisymmetry is lost rather abruptly. These liquid filaments eventually break into droplets of different sizes. In this work, we characterize this transition with a diagram as a function of voltage and liquid conductivity. The electrical response of the long jets was studied via a distributed element circuit model. The model allows us to estimate the electric potential at the tip of the jet revealing that, for any combination of the electrical parameters, the breakup of the jet occurs at a critical value of this potential. We show that this voltage is around 550 V for our device geometry and choice of flow rates. PMID:27375826

AC electrified jets in a flow-focusing device: Jet length scaling.

PubMed

Castro-Hernández, Elena; García-Sánchez, Pablo; Alzaga-Gimeno, Javier; Tan, Say Hwa; Baret, Jean-Christophe; Ramos, Antonio

2016-07-01

We use a microfluidic flow-focusing device with integrated electrodes for controlling the production of water-in-oil drops. In a previous work, we reported that very long jets can be formed upon application of AC fields. We now study in detail the appearance of the long jets as a function of the electrical parameters, i.e., water conductivity, signal frequency, and voltage amplitude. For intermediate frequencies, we find a threshold voltage above which the jet length rapidly increases. Interestingly, this abrupt transition vanishes for high frequencies of the signal and the jet length grows smoothly with voltage. For frequencies below a threshold value, we previously reported a transition from a well-behaved uniform jet to highly unstable liquid structures in which axisymmetry is lost rather abruptly. These liquid filaments eventually break into droplets of different sizes. In this work, we characterize this transition with a diagram as a function of voltage and liquid conductivity. The electrical response of the long jets was studied via a distributed element circuit model. The model allows us to estimate the electric potential at the tip of the jet revealing that, for any combination of the electrical parameters, the breakup of the jet occurs at a critical value of this potential. We show that this voltage is around 550 V for our device geometry and choice of flow rates.

Fabrication and Characterization of Miniaturized Thermocouples

NASA Astrophysics Data System (ADS)

Munzel, Marco; Peinke, Joachim; Kittel, Achim

2002-11-01

The measurement of thermal fluctuations is important for discovering transport features of a passive scalar in fluids. We present a thermal sensor based on a miniaturized thermocouple. Its coaxial setup results from the fabrication as a micropipette normally used in neurobiology. The glass micropipettes contain a core of gold, antimony, or resistance wire and are coated with platinum. The core material is inserted as molten metal or wire and thinned during the fabrication process. The achieved tip diameters are 1μm and less which enhance the spatial and temporal resolution significantly. Because of its chemically inert coating, these sensors are applicative for detecting temperature fluctuations in large variety of liquids and gases. In addition, such thermocouples are intrinsically suitable for applications in scanning probe microscopy. The characterization of these sensors and first results from turbulent free-jet measurements are presented.

Electrical Properties of Reactive Liquid Crystal Semiconductors

NASA Astrophysics Data System (ADS)

McCulloch, Iain; Coelle, Michael; Genevicius, Kristijonas; Hamilton, Rick; Heckmeier, Michael; Heeney, Martin; Kreouzis, Theo; Shkunov, Maxim; Zhang, Weimin

2008-01-01

Fabrication of display products by low cost printing technologies such as ink jet, gravure offset lithography and flexography requires solution processable semiconductors for the backplane electronics. The products will typically be of lower performance than polysilicon transistors, but comparable to amorphous silicon. A range of prototypes are under development, including rollable electrophoretic displays, active matrix liquid crystal displays (AMLCD's), and flexible organic light-emitting diode (OLED) displays. Organic semiconductors that offer both electrical performance and stability with respect to storage and operation under ambient conditions are required. This work describes the initial evaluation of reactive mesogen semiconductors, which can polymerise within mesophase temperatures, “freezing in” the order in crosslinked domains. These crosslinked domains offer mechanical stability and are inert to solvent exposure in further processing steps. Reactive mesogens containing conjugated aromatic cores, designed to facilitate charge transport and provide good oxidative stability, were prepared and their liquid crystalline properties evaluated. Both time-of-flight and field effect transistor devices were prepared and their electrical characterisation reported.

Jet-mixing of initially-stratified liquid-liquid pipe flows: experiments and numerical simulations

NASA Astrophysics Data System (ADS)

Wright, Stuart; Ibarra-Hernandes, Roberto; Xie, Zhihua; Markides, Christos; Matar, Omar

2016-11-01

Low pipeline velocities lead to stratification and so-called 'phase slip' in horizontal liquid-liquid flows due to differences in liquid densities and viscosities. Stratified flows have no suitable single point for sampling, from which average phase properties (e.g. fractions) can be established. Inline mixing, achieved by static mixers or jets in cross-flow (JICF), is often used to overcome liquid-liquid stratification by establishing unstable two-phase dispersions for sampling. Achieving dispersions in liquid-liquid pipeline flows using JICF is the subject of this experimental and modelling work. The experimental facility involves a matched refractive index liquid-liquid-solid system, featuring an ETFE test section, and experimental liquids which are silicone oil and a 51-wt% glycerol solution. The matching then allows the dispersed fluid phase fractions and velocity fields to be established through advanced optical techniques, namely PLIF (for phase) and PTV or PIV (for velocity fields). CFD codes using the volume of a fluid (VOF) method are then used to demonstrate JICF breakup and dispersion in stratified pipeline flows. A number of simple jet configurations are described and their dispersion effectiveness is compared with the experimental results. Funding from Cameron for Ph.D. studentship (SW) gratefully acknowledged.

Investigations of needle-free jet injections.

PubMed

Schramm-Baxter, J R; Mitragotri, S

2004-01-01

Jet injection is a needle-free drug delivery method in which a high-speed stream of fluid impacts the skin and delivers drugs. Although a number of jet injectors are commercially available, especially for insulin delivery, they have a low market share compared to needles possibly due to occasional pain associated with jet injection. Jets employed by the traditional jet injectors penetrate deep into the dermal and sub-dermal regions where the nerve endings are abundantly located. To eliminate the pain associated with jet injections, we propose to utilize microjets that penetrate only into the superficial region of the skin. However, the choice of appropriate jet parameters for this purpose is challenging owing to the multiplicity of factors that determine the penetration depth. Here, we describe the dependence of jet injections into human skin on the power of the jet. Dermal delivery of liquid jets was quantified using two measurements, penetration of a radiolabeled solute, mannitol, into skin and the shape of jet dispersion in the skin which was visualized using sulforhodamine B. The dependence of the amount of liquid delivered in the skin and the geometric measurements of jet dispersion on nozzle diameter and jet velocity was captured by a single parameter, jet power.

Radio observations of a few selected blazars

NASA Technical Reports Server (NTRS)

Saikia, D. J.; Salter, C. J.; Neff, S. G.; Gower, A. C.; Sinha, R. P.

1987-01-01

The paper presents total-intensity and linear-polarization observations of four selected blazars, 0716+714, 0752+258, 1156+295 and 1400+162, with the VLA A-array, and MERLIN and EVN observations of 1400+162. The sources 0752+258 and 1400+162 which have nearly constant optical polarization, have well-defined double-lobed radio structure, with relatively weak radio cores, and are likely to be at large viewing angles. In addition, 0752+258 appears to be a twin-jet blazar. The position angle (PA) of the VLBI jet in 1400+162 is close to that of the arcsec-scale jet near the nucleus, as well as the optical and 2-cm core polarization PAs. The blazars 0716+714 and 1156+295, which exhibit strongly variable optical polarization, have a core-dominated radio structure and perhaps have their jet axes close to the line-of-sight. From polarization observations at 20, 18, 6, and 2 cm, it is found that the rotation measure of the radio core in 0716+714 is about -20 rad/sq m. It is suggested that low values of core rotation measure in core-dominated sources could be consistent with the relativistic beaming models.

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.

Thermal bending of liquid sheets and jets

NASA Astrophysics Data System (ADS)

Brenner, Michael P.; Paruchuri, Srinivas

2003-11-01

We present an analytical model for the bending of liquid jets and sheets from temperature gradients, as recently observed by Chwalek et al. [Phys. Fluids 14, L37 (2002)]. The bending arises from a local couple caused by Marangoni forces. The dependence of the bending angle on experimental parameters is presented, in qualitative agreement with reported experiments. The methodology gives a simple framework for understanding the mechanisms for jet and sheet bending.

Combustion and Engine-Core Noise

NASA Astrophysics Data System (ADS)

Ihme, Matthias

2017-01-01

The implementation of advanced low-emission aircraft engine technologies and the reduction of noise from airframe, fan, and jet exhaust have made noise contributions from an engine core increasingly important. Therefore, meeting future ambitious noise-reduction goals requires the consideration of engine-core noise. This article reviews progress on the fundamental understanding, experimental analysis, and modeling of engine-core noise; addresses limitations of current techniques; and identifies opportunities for future research. After identifying core-noise contributions from the combustor, turbomachinery, nozzles, and jet exhaust, they are examined in detail. Contributions from direct combustion noise, originating from unsteady combustion, and indirect combustion noise, resulting from the interaction of flow-field perturbations with mean-flow variations in turbine stages and nozzles, are analyzed. A new indirect noise-source contribution arising from mixture inhomogeneities is identified by extending the theory. Although typically omitted in core-noise analysis, the impact of mean-flow variations and nozzle-upstream perturbations on the jet-noise modulation is examined, providing potential avenues for future core-noise mitigation.

Neutron Star Natal Kick and Jets in Core Collapse Supernovae

NASA Astrophysics Data System (ADS)

Bear, Ealeal; Soker, Noam

2018-03-01

We measure the angle between the neutron star (NS) natal kick direction and the inferred direction of jets according to the morphology of 12 core collapse supernova remnants (SNR), and find that the distribution is almost random, but missing small angles. The 12 SNRs are those for which we could both identify morphological features that we can attribute to jets and for which the direction of the NS natal kick is given in the literature. Unlike some claims for spin-kick alignment, here we rule out jet-kick alignment. We discuss the cumulative distribution function of the jet-kick angles under the assumption that dense clumps that are ejected by the explosion accelerate the NS by the gravitational attraction, and suggest that the jet feedback explosion mechanism might in principle account for the distribution of jet-kick angles.

Interaction of a liquid jet with an oncoming gas stream

NASA Astrophysics Data System (ADS)

Koval', M. A.; Shvets, A. I.

1987-06-01

Wind-tunnel tests were carried out to study the interaction between water jets issuing from various types of nozzles (including cylindrical) and subsonic and supersonic air streams with Mach numbers from 0.3 to 3 and Reynolds numbers from 1 x 10 to the 6th to 3 x 10 to the 7th. The following interaction structure was observed: (1) at moderate outflow velocities, the liquid jet has an extended region, which subsequently expands abruptly as a spherical or mushroom-shaped drop; (2) this drop is atomized in the peripheral region and is carried away as a gas-liquid mixture; (3) a shock wave is formed in front of the jet in the oncoming supersonic stream; and (4) a separated flow region is present in the vicinity of the cylindrical nozzle section.

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.

Atomization of a High Speed Jet

NASA Astrophysics Data System (ADS)

Xu, Zhiliang; Samulyak, Roman; Li, Xiaolin; Tzanos, Constantine

2005-11-01

We present a numerical study of the jet breakup and spray formation in a diesel engine by the Front Tracking method. The mechanisms of jet breakup and spray formation of a high speed diesel jet injected through a circular nozzle are the key to design a fuel efficient, nonpolluting diesel engine. Many parameters such as the nuzzle shape, the velocity and the turbulence of the jet and the thermodynamic states of liquid and gas could be contributing causes for jet breakup. We conduct the simulations for the jet breakup within a 2D axis-symmetric geometry. Our goal is to model the spray at a micro-physical level, with the creation of individual droplets. The problem is multiscale. The droplets are a few microns in size. The nozzle is about 0.2 mm in diameter and 1 mm in length. In order to resolve various physical patterns such as vortex, shock waves, vacuum and track droplets and spray, the Burger-Colella adaptive mesh refinement technique is used. We model mixed vapor-liquid region through a heterogeneous model with dynamic vapor bubble insertion. On the liquid/vapor interface, a phase transition problem is solved numerically.

Wave packet analysis and break-up length calculations for an accelerating planar liquid jet

NASA Astrophysics Data System (ADS)

Turner, M. R.; Healey, J. J.; Sazhin, S. S.; Piazzesi, R.

2012-02-01

This paper examines the process of transition to turbulence within an accelerating planar liquid jet. By calculating the propagation and spatial evolution of disturbance wave packets generated at a nozzle where the jet emerges, we are able to estimate break-up lengths and break-up times for different magnitudes of acceleration and different liquid to air density ratios. This study uses a basic jet velocity profile that has shear layers in both air and the liquid either side of the fluid interface. The shear layers are constructed as functions of velocity which behave in line with our CFD simulations of injecting diesel jets. The non-dimensional velocity of the jet along the jet centre-line axis is assumed to take the form V (t) = tanh(at), where the parameter a determines the magnitude of the acceleration. We compare the fully unsteady results obtained by solving the unsteady Rayleigh equation to those of a quasi-steady jet to determine when the unsteady effects are significant and whether the jet can be regarded as quasi-steady in typical operating conditions for diesel engines. For a heavy fluid injecting into a lighter fluid (density ratio ρair/ρjet = q < 1), it is found that unsteady effects are mainly significant at early injection times where the jet velocity profile is changing fastest. When the shear layers in the jet thin with time, the unsteady effects cause the growth rate of the wave packet to be smaller than the corresponding quasi-steady jet, whereas for thickening shear layers the unsteady growth rate is larger than that of the quasi-steady jet. For large accelerations (large a), the unsteady effect remains at later times but its effect on the growth rate of the wave packet decreases as the time after injection increases. As the rate of acceleration is reduced, the range of velocity values for which the jet can be considered as quasi-steady increases until eventually the whole jet can be considered quasi-steady. For a homogeneous jet (q = 1), the range of values of a for which the jet can be considered completely quasi-steady increases to larger values of a. Finally, we investigate approximating the wave packet break-up length calculations with a method that follows the most unstable disturbance wave as the jet accelerates. This approach is similar to that used in CFD simulations as it greatly reduces computational time. We investigate whether or not this is a good approximation for the parameter values typically used in diesel engines.

Application of a Flip-Flop Nozzle on Plume Mixing Enhancement

NASA Technical Reports Server (NTRS)

Schreck, Stefan; Michaelian, Mark; Ho, Chih-Ming

1999-01-01

Mach wave radiation is a major source of noise in high speed jets. It is created by turbulent eddies which travel at supersonic speed within the shear layer of the jet. Downstream of the potential core, the convection speed of the eddies decays and noise production is reduced. Once the convection speeds drops below the speed of sound, eddy Mach wave radiation ceases. Mach wave radiation may be reduced by shortening the core length of the jet. This requires a faster growth of the shear layer, i.e. enhanced mixing in the jet. We investigated the possibility of mixing enhancement by the excitation of the instability waves in a supersonic rectangular jet.

Effect of Shrouding Gas Temperature on Characteristics of a Supersonic Jet Flow Field with a Shrouding Laval Nozzle Structure

NASA Astrophysics Data System (ADS)

Liu, Fuhai; Sun, Dongbai; Zhu, Rong; Li, Yilin

2018-05-01

Coherent jet technology was been widely used in the electric arc furnace steelmaking process to protect the kinetic energy of supersonic oxygen jets and achieve a better mixing effect. For this technology, the total temperature distribution of the shrouding jet has a great impact on the velocity of the main oxygen jet. In this article, a supersonic shrouding nozzle using a preheating shrouding jet is proposed to increase the shrouding jet velocity. Both numerical simulation and experimental studies were carried out to analyze its effect on the axial velocity, total temperature and turbulence kinetic energy profiles of the main oxygen jet. Based on these results, it was found that a significant amount of kinetic energy was removed from the main oxygen jet when it passed though the shock wave using a high-temperature shrouding jet, which made the average axial velocity of the coherent jet lower than for a conventional jet in the potential core region. However, the supersonic shrouding nozzle and preheating technology employed for this nozzle design significantly improved the shrouding gas velocity, forming a low-density gas zone at the exit of the main oxygen jet and prolonging the velocity potential core length.

The study of the behaviour of a disturbed semi-infinite liquid jet using a spatial instability method

NASA Astrophysics Data System (ADS)

Basu (‧nee De), Shukla

2001-11-01

A study has been made of the behaviour of a disturbed semi-infinite liquid jet using a spatial instability method. A sinusoidal disturbance in the axial component of jet velocity at the nozzle is considered which resulted in an elliptic free surface boundary value problem with two non-linear boundary conditions. The system is linearised using perturbation techniques and the first order solution resulted in the dispersion relation. The jet stability is found to depend explicitly on the frequency of the disturbance and the Weber number. The second and third order solutions have been derived analytically which are used to predict on jet break-up and satellite formation.

Velocimetry of fast microscopic liquid jets by nanosecond dual-pulse laser illumination for megahertz X-ray free-electron lasers.

PubMed

Grünbein, Marie Luise; Shoeman, Robert L; Doak, R Bruce

2018-03-19

To conduct X-ray Free-Electron Laser (XFEL) measurements at megahertz (MHz) repetition rates, sample solution must be delivered in a micron-sized liquid free-jet moving at up to 100 m/s. This exceeds by over a factor of two the jet speeds measurable with current high-speed camera techniques. Accordingly we have developed and describe herein an alternative jet velocimetry based on dual-pulse nanosecond laser illumination. Three separate implementations are described, including a small laser-diode system that is inexpensive and highly portable. We have also developed and describe analysis techniques to automatically and rapidly extract jet speed from dual-pulse images.

Dripping and jetting regimes in co-flowing capillary jets: unforced measurements and response to driving

NASA Astrophysics Data System (ADS)

Baroud, Charles; Cordero, Maria-Luisa; Gallaire, Francois

2011-11-01

We study the breakup of drops in a co-flowing jet, within the confinement of a microfluidic channel. The breakup can occur right after the nozzle (dripping) or through the generation of a liquid jet that breaks up a long distance from the nozzle (jetting). Traditionally, these two regimes have been considered to reflect an absolutely unstable jet or a convectively unstable jet, respectively. We first provide measurements of the frequency of oscillation and breakup of the liquid jet; the dispersion relation thus obtained compares well with existing theories for convective instabilities in the case of the jetting regime. However, the theories in the absolutely unstable mode fail to predict the evolution of the frequency and drop size in the dripping regime. We also test the jet response to an external forcing, using a focused laser to locally heat the jet. The dripping regime is found to be insensitive to the perturbation and the frequency of drop formation remains unaltered. In contrast, the jetting regime locks to the external frequency, which translates into a modification of the drop size in agreement with the dispersion relations. This confirms the convective nature of the jetting regime. Permanent address: Universidad de Chile.

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.

Ion evaporation from the surface of a Taylor cone.

PubMed

Higuera, F J

2003-07-01

An analysis is carried out of the electric field-induced evaporation of ions from the surface of a polar liquid that is being electrosprayed in a vacuum. The high-field cone-to-jet transition region of the electrospray, where ion evaporation occurs, is studied taking advantage of its small size and neglecting the inertia of the liquid and the space charge around the liquid. Evaporated ions and charged drops coexist in a range of flow rates, which is investigated numerically. The structure of the cone-to-jet transition comprises: a hydrodynamic region where the nearly equipotential surface of the liquid departs from a Taylor cone and becomes a jet; a slender region where the radius of the jet decreases and the electric field increases while the pressure and the viscous stress balance the electric stress at the surface; the ion evaporation region of high, nearly constant field; and a charged, continuously strained jet that will eventually break into drops. Estimates of the ion and drop contributions to the total, conduction-limited current show that the first of these contributions dominates for small flow rates, while most of the mass is still carried by the drops.

Jet Power vs. Black Hole Mass in Blazars: Exploring the Relationship in the Context of the B-Z Mechanism

NASA Astrophysics Data System (ADS)

Fernandes, Sunil; Schlegel, E.

2012-01-01

Recently, a tentative negative correlation between jet power and BH mass in a sample of GeV-TeV BL Lac objects(Zhang et al 2011). It was suggested that spin energy extraction could play a significant role in producing the jets and the jets are not purely accretion driven. Broderick et al (2011) recently explored the relationship between jet power and radio core luminosity building on Blanford et al (1979) theoretical work. Using this work we have studied the relationship between radio core luminosity (as a stand in for jet power) and black hole mass and have found a possible positive correlation in a sample of nearby BL Lac objects. The present poster attempts to explore this relationship in the context of the Blanford-Znajek mechanism which predicts jet power increases with black hole mass, spin rate, and accretion rate.

The Properties of Extragalactic Radio Jets

NASA Astrophysics Data System (ADS)

Finke, Justin

2018-01-01

I show that by assuming a standard Blandford-Konigl jet, it is possible to determine the speed (bulk Lorentz factor) and orientation (angle to the line of sight) of self-similar parsec-scale blazar jets by using four measured quantities: the core radio flux, the extended radio flux, the magnitude of the core shift between two frequencies, and the apparent jet opening angle. Once the bulk Lorentz factor and angle to the line of sight of a jet are known, it is possible to compute their Doppler factor, magnetic field, and intrinsic jet opening angle. I use data taken from the literature and marginalize over nuisance parameters associated with the electron distribution and equipartition, to compute these quantities, albeit with large errors. The results have implications for the resolution of the TeV BL Lac Doppler factor crisis and the production of jets from magnetically arrested disks.

The Driving Magnetic Field and Reconnection in CME/Flare Eruptions and Coronal Jets

NASA Technical Reports Server (NTRS)

Moore, Ronald L.

2010-01-01

Signatures of reconnection in major CME (coronal mass ejection)/flare eruptions and in coronal X-ray jets are illustrated and interpreted. The signatures are magnetic field lines and their feet that brighten in flare emission. CME/flare eruptions are magnetic explosions in which: 1. The field that erupts is initially a closed arcade. 2. At eruption onset, most of the free magnetic energy to be released is not stored in field bracketing a current sheet, but in sheared field in the core of the arcade. 3. The sheared core field erupts by a process that from its start or soon after involves fast "tether-cutting" reconnection at an initially small current sheet low in the sheared core field. If the arcade has oppositely-directed field over it, the eruption process from its start or soon after also involves fast "breakout" reconnection at an initially small current sheet between the arcade and the overarching field. These aspects are shown by the small area of the bright field lines and foot-point flare ribbons in the onset of the eruption. 4. At either small current sheet, the fast reconnection progressively unleashes the erupting core field to erupt with progressively greater force. In turn, the erupting core field drives the current sheet to become progressively larger and to undergo progressively greater fast reconnection in the explosive phase of the eruption, and the flare arcade and ribbons grow to become comparable to the pre-eruption arcade in lateral extent. In coronal X-ray jets: 1. The magnetic energy released in the jet is built up by the emergence of a magnetic arcade into surrounding unipolar "open" field. 2. A simple jet is produced when a burst of reconnection occurs at the current sheet between the arcade and the open field. This produces a bright reconnection jet and a bright reconnection arcade that are both much smaller in diameter that the driving arcade. 3. A more complex jet is produced when the arcade has a sheared core field and undergoes an ejective eruption in the manner of a miniature CME/flare eruption. The jet is then a combination of a miniature CME and the products of more widely distributed reconnection of the erupting arcade with the open field than in simple jets.

Method and means for producing solid evacuated microspheres of hydrogen

DOEpatents

Turnbull, Robert J.; Foster, Christopher A.; Hendricks, Charles D.

1976-01-01

A method is provided for producing solid, evacuated microspheres comprised of hydrogen. The spheres are produced by forming a jet of liquid hydrogen and exciting mechanical waves on the jet of appropriate frequency so that the jet breaks up into drops with a bubble formed in each drop by cavitation. The drops are exposed to a pressure less than the vapor pressure of the liquid hydrogen so that the bubble which is formed within each drop expands. The drops which contain bubbles are exposed to an environment having a pressure just below the triple point of liquid hydrogen and they thereby freeze giving solid, evacuated spheres of hydrogen.

Solid evacuated microspheres of hydrogen

DOEpatents

Turnbull, Robert J.; Foster, Christopher A.; Hendricks, Charles D.

1982-01-01

A method is provided for producing solid, evacuated microspheres comprised of hydrogen. The spheres are produced by forming a jet of liquid hydrogen and exciting mechanical waves on the jet of appropriate frequency so that the jet breaks up into drops with a bubble formed in each drop by cavitation. The drops are exposed to a pressure less than the vapor pressure of the liquid hydrogen so that the bubble which is formed within each drop expands. The drops which contain bubbles are exposed to an environment having a pressure just below the triple point of liquid hydrogen and they thereby freeze giving solid, evacuated spheres of hydrogen.

MHD supernova jets: the missing link

NASA Technical Reports Server (NTRS)

Meier, David L.; Nakamura, Masanori

2003-01-01

We review recent progress in the theory of jet production, with particular emphasis on the possibility of 1) powerful jets being produced in the first few seconds after collapse of a supernova core and 2)those jets being responsible for the aysmmetric explosion itself.

Constraints on Saturn's Tropospheric General Circulation from Cassini ISS Images

NASA Technical Reports Server (NTRS)

DelGenio, Anthony D.; Barbara, John M.

2013-01-01

An automated cloud tracking algorithm is applied to Cassini Imaging Science Subsystem high-resolution apoapsis images of Saturn from 2005 and 2007 and moderate resolution images from 2011 and 2012 to define the near-global distribution of zonal winds and eddy momentum fluxes at the middle troposphere cloud level and in the upper troposphere haze. Improvements in the tracking algorithm combined with the greater feature contrast in the northern hemisphere during the approach to spring equinox allow for better rejection of erroneous wind vectors, a more objective assessment at any latitude of the quality of the mean zonal wind, and a population of winds comparable in size to that available for the much higher contrast atmosphere of Jupiter. Zonal winds at cloud level changed little between 2005 and 2007 at all latitudes sampled. Upper troposphere zonal winds derived from methane band images are approx. 10 m/s weaker than cloud level winds in the cores of eastward jets and approx. 5 m/s stronger on either side of the jet core, i.e., eastward jets appear to broaden with increasing altitude. In westward jet regions winds are approximately the same at both altitudes. Lateral eddy momentum fluxes are directed into eastward jet cores, including the strong equatorial jet, and away from westward jet cores and weaken with increasing altitude on the flanks of the eastward jets, consistent with the upward broadening of these jets. The conversion rate of eddy to mean zonal kinetic energy at the visible cloud level is larger in eastward jet regions (5.2x10(exp -5) sq m/s) and smaller in westward jet regions (1.6x10(exp -5) sqm/s) than the global mean value (4.1x10(ep -5) sq m/s). Overall the results are consistent with theories that suggest that the jets and the overturning meridional circulation at cloud level on Saturn are maintained at least in part by eddies due to instabilities of the large-scale flow near and/or below the cloud level.

Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets

DTIC Science & Technology

2014-12-18

themselves. Detailed discussions of the microjet technique are carried out in the following publications. Nozzle Liquid Jet Chopper Wheel...heating and evaporation occur within 1 ms of fuel leaving the fuel injector . This atomization proves is often the limiting process in combustion...This analysis leads to criteria for selecting the temperature and nozzle radius for producing stable jets in vacuum. Figure 4 depicts the

DETERMINATION OF CENTRAL ENGINE POSITION AND ACCRETION DISK STRUCTURE IN NGC 4261 BY CORE SHIFT MEASUREMENTS

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

Haga, Takafumi; Doi, Akihiro; Murata, Yasuhiro

2015-07-01

We report multifrequency phase-referenced observations of the nearby radio galaxy NGC 4261, which has prominent two-sided jets, using the Very Long Baseline Array at 1.4–43 GHz. We measured radio core positions showing observing frequency dependences (known as “core shift”) in both approaching jets and counterjets. The limit of the core position as the frequency approaches infinity, which suggests a jet base, is separated by 82 ± 16 μas upstream in projection, corresponding to (310 ± 60)R{sub s} (R{sub s}: Schwarzschild radius) as a deprojected distance, from the 43 GHz core in the approaching jet. In addition, the innermost component atmore » the counterjet side appeared to approach the same position at infinity of the frequency, indicating that cores on both sides are approaching the same position, suggesting a spatial coincidence with the central engine. Applying a phase-referencing technique, we also obtained spectral index maps, which indicate that emission from the counterjet is affected by free–free absorption (FFA). The result of the core shift profile on the counterjet also requires FFA because the core positions at 5–15 GHz cannot be explained by a simple core shift model based on synchrotron self-absorption (SSA). Our result is apparently consistent with the SSA core shift with an additional disk-like absorber over the counterjet side. Core shift and opacity profiles at the counterjet side suggest a two-component accretion: a radiatively inefficient accretion flow at the inner region and a truncated thin disk in the outer region. We proposed a possible solution about density and temperature profiles in the outer disk on the basis of the radio observation.« less

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

Gilkis, Avishai; Soker, Noam; Papish, Oded, E-mail: agilkis@tx.technion.ac.il, E-mail: soker@physics.technion.ac.il, E-mail: papish@campus.technion.ac.il

We suggest that the energetic radiation from core-collapse super-energetic supernovae (SESNe) is due to a long-lasting accretion process onto the newly born neutron star (NS), resulting from an inefficient operation of the jet-feedback mechanism (JFM). The jets that are launched by the accreting NS or black hole maintain their axis due to a rapidly rotating pre-collapse core and do not manage to eject core material from near the equatorial plane. The jets are able to eject material from the core along the polar directions and reduce the gravity near the equatorial plane. The equatorial gas expands, and part of itmore » falls back over a timescale of minutes to days to prolong the jet-launching episode. According to the model for SESNe proposed in the present paper, the principal parameter that distinguishes between the different cases of core-collapse supernova (CCSN) explosions, such as between normal CCSNe and SESNe, is the efficiency of the JFM. This efficiency, in turn, depends on the pre-collapse core mass, envelope mass, core convection, and, most of all, the angular momentum profile in the core. One prediction of the inefficient JFM for SESNe is the formation of a slow equatorial outflow in the explosion. The typical velocity and mass of this outflow are estimated to be v {sub eq} ≈ 1000 km s{sup −1} and M {sub eq} ≳ 1 M {sub ⊙}, respectively, though quantitative values will have to be checked in future hydrodynamic simulations.« less

Capillary jets in normal gravity: Asymptotic stability analysis and excitation using Maxwell and ultrasonic radiation stresses

NASA Astrophysics Data System (ADS)

Lonzaga, Joel Barci

Both modulated ultrasonic radiation pressure and oscillating Maxwell stress from a voltage-modulated ring electrode are employed to excite low-frequency capillary modes of a weakly tapered liquid jet issuing from a nozzle. The capillary modes are waves formed at the surface of the liquid jet. The ultrasound is internally applied to the liquid jet waveguide and is cut off at a location resulting in a significantly enhanced oscillating radiation stress near the cutoff location. Alternatively, the thin electrode can generate a highly localized oscillating Maxwell stress on the jet surface. Experimental evidence shows that a spatially unstable mode with positive group velocity (propagating downstream from the excitation source) and a neutral mode with negative group velocity are both excited. Reflection at the nozzle boundary converts the neutral mode into an unstable one that interferes with the original unstable mode. The interference effect is observed downstream from the source using a laser-based optical extinction technique that detects the surface waves while the modulation frequency is scanned. This technique is very sensitive to small-amplitude disturbances. Existing linear, convective stability analyses on liquid jets accounting for the gravitational effect (i.e. varying radius and velocity) appear to be not applicable to non-slender, slow liquid jets considered here where the gravitational effect is found substantial at low flow rates. The multiple-scales method, asymptotic expansion and WKB approximation are used to derive a dispersion relation for the capillary wave similar to one obtained by Rayleigh but accounting for the gravitational effect. These mathematical tools aided by Langer's transformation are also used to derive a uniformly valid approximation for the acoustic wave propagation in a tapered cylindrical waveguide. The acoustic analytical approximation is validated by finite-element calculations. The jet response is modeled using a hybrid of Fourier analysis and the WKB-type analysis as proposed by Lighthill. The former derives the mode response to a highly localized source while the latter governs the mode propagation in a weakly inhomogeneous jet away from the source.

CYGNUS A: Hot Spots, Bow Shocks, Core Emission, and Exclusion of Cluster Gas by Radio Lobes

NASA Technical Reports Server (NTRS)

Harris, Daniel E.

1999-01-01

This report covers work preformed on three ROSAT projects: (1) Monitoring the X-ray Intensity of the Core and Jet of M87; (2) The radio-optical jet in 3C-120 and (3) A search for cluster emission at high redshift.

Mixing and transient interface condensation of a liquid hydrogen tank

NASA Technical Reports Server (NTRS)

Lin, C. S.; Hasan, M. M.; Nyland, T. W.

1993-01-01

Experiments were conducted to investigate the effect of axial jet-induced mixing on the pressure reduction of a thermally stratified liquid hydrogen tank. The tank was nearly cylindrical, having a volume of about 0.144 cu m with 0.559 m in diameter and 0.711 m length. A mixer/pump unit, which had a jet nozzle outlet of 0.0221 m in diameter was located 0.178 m from the tank bottom and was installed inside the tank to generate the axial jet mixing and tank fluid circulation. Mixing tests began with the tank pressures at which the thermal stratification results in 4.9-6.2 K liquid subcooling. The mixing time and transient vapor condensation rate at the liquid-vapor interface are determined. Two mixing time correlations, based on the thermal equilibrium and pressure equilibrium, are developed and expressed as functions of system and buoyancy parameters. The limited liquid hydrogen data of the present study shows that the modified steady state condensation rate correlation may be used to predict the transient condensation rate in a mixing process if the instantaneous values of jet sub cooling and turbulence intensity at the interface are employed.

Analysis of High Speed Jets Produced by a Servo Tube Driven Liquid Jet Injector

NASA Astrophysics Data System (ADS)

Portaro, Rocco; Ng, Hoi Dick

2017-11-01

In today's healthcare environment many types of medication must be administered through the use of hypodermic needles. Although this practice has been in use for many years, drawbacks such as accidental needle stick injuries, transmission of deadly viruses and bio-hazardous waste are still present. This study focuses on improving a needle free technology known as liquid jet injection, through the implementation of a linear servo tube actuator for the construction of a fully closed loop liquid jet injection system. This device has the ability to deliver both micro- and macro- molecules, high viscosity fluids whilst providing real time control of the jet pressure profile for accurate depth and dispersion control. The experiments are conducted using a prototype that consists of a 3 kW servo tube actuator, coupled to a specially designed injection head allowing nozzle size and injection volume to be varied. The device is controlled via a high speed servo amplifier and FPGA. The high speed jets emanating from the injector are assessed via high speed photography and through the use of a force transducer. Preliminary results indicate that the system allows for accurate shaping of the jet pressure profile, making it possible to target different tissue depths/types accurately.

A Very Stable High Throughput Taylor Cone-jet in Electrohydrodynamics

PubMed Central

Morad, M. R.; Rajabi, A.; Razavi, M.; Sereshkeh, S. R. Pejman

2016-01-01

A stable capillary liquid jet formed by an electric field is an important physical phenomenon for formation of controllable small droplets, power generation and chemical reactions, printing and patterning, and chemical-biological investigations. In electrohydrodynamics, the well-known Taylor cone-jet has a stability margin within a certain range of the liquid flow rate (Q) and the applied voltage (V). Here, we introduce a simple mechanism to greatly extend the Taylor cone-jet stability margin and produce a very high throughput. For an ethanol cone-jet emitting from a simple nozzle, the stability margin is obtained within 1 kV for low flow rates, decaying with flow rate up to 2 ml/h. By installing a hemispherical cap above the nozzle, we demonstrate that the stability margin could increase to 5 kV for low flow rates, decaying to zero for a maximum flow rate of 65 ml/h. The governing borders of stability margins are discussed and obtained for three other liquids: methanol, 1-propanol and 1-butanol. For a gravity-directed nozzle, the produced cone-jet is more stable against perturbations and the axis of the spray remains in the same direction through the whole stability margin, unlike the cone-jet of conventional simple nozzles. PMID:27917956

A Physical Model Study of Two-Phase Gas-Liquid Flows in a Ladle Shroud

NASA Astrophysics Data System (ADS)

Singh, Prince K.; Mazumdar, Dipak

2018-06-01

Argon-steel flows inside a ladle shroud during teeming from a ladle to a tundish have been modelled physically. To this end, full-scale Perspex models of bloom as well as slab casting shrouds (BCS and SCS), operating with air and water, have been applied. Both open to air as well as immersed conditions were investigated with and without gas injection. Flows inside a ladle shroud under open to air and immersed conditions were found to be substantially different with a strong function of gas and liquid flow rates, collector nozzle and shroud diameters. Depending on the volumetric gas injection rate relative to liquid flow rate, different flow regimes have been observed in an immersed shroud [ i.e., 0 < ( ds/L_{s} ) ≤ 0.24 ]. At extremely low gas flow rates, [ i.e., ( Qg/Q_{L} ) ≤ 0.02 ], injected gas is completely entrained as bubbles by the down-flowing liquid resulting in a bubbly two-phase flow over the entire length of a shroud. However, with an increasing gas flow rate, two distinctly different regions start to develop within the shroud body: a free liquid jet in the upper part and a gas-liquid mixing zone below. The length of the free jet increases with an increasing gas flow rate and at significantly higher gas to liquid flow rates [ viz., ( Qg/Q_{L} )_{BCS} ≥ 0.42 ] and [ viz., ( Qg/Q_{L} )_{SCS} ≥ 0.30 ] , and the free jet is found to prevail over the entire length of the shroud. Within the range of conditions studied, it is observed that the free jet length or the line of demarcation between the jetting and two-phase mixing zone depends on gas and liquid flow rates and is specific to a particular shroud-collector nozzle system. Physical model results further indicate that a sufficiently large free jet length ( shroud length) tends to create a high pressure region inside a shroud and prevent ingression of air. Possible implications of the present findings with reference to industrial teeming practices are also discussed in the text.

The Mechanism of Jet Disintegration

DTIC Science & Technology

1949-08-29

disoharge typ« noul«) th« liquid jet 1« deflected about 90° dlr«otly after leaving th« nettle . Thia banding rapraaanta a stronr singular...thet l y inarintln- a definite wave length on the jet by outer forces, for exa-nple by neohanloal Vibration of the nettle , t>ie liq >ld will...Spray .Hosiles I. IHTRODUCTIOl 1« It It a «»11 know faot that any liquid stream disintegrates into droplet« after leaving a nettle or

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.

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.

A key to improved ion core confinement in the JET tokamak: ion stiffness mitigation due to combined plasma rotation and low magnetic shear.

PubMed

Mantica, P; Angioni, C; Challis, C; Colyer, G; Frassinetti, L; Hawkes, N; Johnson, T; Tsalas, M; deVries, P C; Weiland, J; Baiocchi, B; Beurskens, M N A; Figueiredo, A C A; Giroud, C; Hobirk, J; Joffrin, E; Lerche, E; Naulin, V; Peeters, A G; Salmi, A; Sozzi, C; Strintzi, D; Staebler, G; Tala, T; Van Eester, D; Versloot, T

2011-09-23

New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma, as described by Mantica et al. [Phys. Rev. Lett. 102, 175002 (2009)] results from the combined effect of high rotational shear and low magnetic shear. The observations have important implications for the understanding of improved ion core confinement in advanced tokamak scenarios. Simulations using quasilinear fluid and gyrofluid models show features of stiffness mitigation, while nonlinear gyrokinetic simulations do not. The JET experiments indicate that advanced tokamak scenarios in future devices will require sufficient rotational shear and the capability of q profile manipulation.

Criteria for disintegration of an uncharged conducting liquid jet in a transverse electric field

NASA Astrophysics Data System (ADS)

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

2018-01-01

An uncharged conducting liquid cylindrical column (a jet for applications) placed between a pair of flat electrodes is considered. In the trivial case, when the electric field is absent, the jet with circular cross-section is the only possible equilibrium configuration of the system. In the presence of a potential difference between the electrodes, the jet is deformed by the electrostatic forces: its cross-section stretches along the electric field lines. In the case of the mutual compensation of the electrostatic and capillary forces, a new equilibrium configuration of the jet can appear. In a sufficiently strong field, the balance of the forces becomes impossible, and the jet disintegrates (splits into two separate jets). In the present work, we find the range of the parameters (the applied potential difference and the interelectrode distance), where the problem of finding the equilibrium configurations of the jet has solutions. Also we obtain the conditions under which the solutions do not exist and, consequently, the jet splits. The results are compared with the previously studied limiting case of infinite interelectrode distance.

The production of drops by the bursting of a bubble at an air liquid interface

NASA Technical Reports Server (NTRS)

Darrozes, J. S.; Ligneul, P.

1982-01-01

The fundamental mechanism arising during the bursting of a bubble at an air-liquid interface is described. A single bubble was followed from an arbitrary depth in the liquid, up to the creation and motion of the film and jet drops. Several phenomena were involved and their relative order of magnitude was compared in order to point out the dimensionless parameters which govern each step of the motion. High-speed cinematography is employed. The characteristic bubble radius which separates the creation of jet drops from cap bursting without jet drops is expressed mathematically. The corresponding numerical value for water is 3 mm and agrees with experimental observations.

Thermo-capillary effect on the linear temporal and spatial instability of viscous liquid jets falling under gravity

NASA Astrophysics Data System (ADS)

Alsharif, Abdullah M.; Althubaiti, Shadiah A.

2018-03-01

The thermal modulation of Newtonian liquid jets at the orifice causes a variation in surface tension, which propagates downstream inducing Marangoni instability. Therefore, the linear temporal and spatial instability should be investigated to predict the same size of producing small spherical pellets. In this paper, we consider a viscous liquid jet emerging from a nozzle subject to thermo-capillary effects falling under gravity. Moreover, we use the asymptotic approach to reduce the governing equation into one-dimensional (1-D). The steady state solutions have been found using a modified Newton's method, and then the linear instability analysis has been investigated of the resulting set of equations.

Integrated modelling of H-mode pedestal and confinement in JET-ILW

NASA Astrophysics Data System (ADS)

Saarelma, S.; Challis, C. D.; Garzotti, L.; Frassinetti, L.; Maggi, C. F.; Romanelli, M.; Stokes, C.; Contributors, JET

2018-01-01

A pedestal prediction model Europed is built on the existing EPED1 model by coupling it with core transport simulation using a Bohm-gyroBohm transport model to self-consistently predict JET-ILW power scan for hybrid plasmas that display weaker power degradation than the IPB98(y, 2) scaling of the energy confinement time. The weak power degradation is reproduced in the coupled core-pedestal simulation. The coupled core-pedestal model is further tested for a 3.0 MA plasma with the highest stored energy achieved in JET-ILW so far, giving a prediction of the stored plasma energy within the error margins of the measured experimental value. A pedestal density prediction model based on the neutral penetration is tested on a JET-ILW database giving a prediction with an average error of 17% from the experimental data when a parameter taking into account the fuelling rate is added into the model. However the model fails to reproduce the power dependence of the pedestal density implying missing transport physics in the model. The future JET-ILW deuterium campaign with increased heating power is predicted to reach plasma energy of 11 MJ, which would correspond to 11-13 MW of fusion power in equivalent deuterium-tritium plasma but with isotope effects on pedestal stability and core transport ignored.

Cell Sheet Stiffness Sensing without taking out from culture liquid.

PubMed

Uchida, Ryohei; Tanaka, Nobuyuki; Higashimori, Mitsuru; Tadakuma, Kenjiro; Kaneko, Makoto; Kondo, Makoto; Yamato, Masayuki

2010-01-01

Stiffness could be an important index for evaluating the vitality of cell sheet. This paper challenges the measurement of stiffness of transparent cell sheet in culture liquid without taking it out from petri dish. The system is composed of a micro air nozzle for supplying an air jet and a regular reflective type laser sensor for measuring the the deformation of transparent cell sheet. This system is called as Cell Sheet Stiffness Sensing system (CS(3) system). When an air jet is given to a cell sheet in culture liquid, it pushes away the liquid toward the outer direction at initial phase and reaches the surface of cell sheet. Without any switching motion, the air jet continuously imparts a force to the surface of cell sheet so that the sensor can measure the stiffness of the cell sheet.

Experimental investigation on the effect of liquid injection by multiple orifices in the formation of droplets in a Venturi scrubber.

PubMed

Guerra, V G; Gonçalves, J A S; Coury, J R

2009-01-15

Venturi scrubbers are widely utilized in gas cleaning. The cleansing elements in these scrubbers are droplets formed from the atomization of a liquid into a dust-laden gas. In industrial scrubbers, this liquid is injected through several orifices so that the cloud of droplets can be evenly distributed throughout the duct. The interaction between droplets when injected through many orifices, where opposite clouds of atomized liquid can reach each other, is to be expected. This work presents experimental measurements of droplet size measured in situ and the evidence of cloud interaction within a Venturi scrubber operating with multi-orifice jet injection. The influence of gas velocity, liquid flow rate and droplet size variation in the axial position after the point of the injection of the liquid were also evaluated for the different injection configurations. The experimental results showed that an increase in the liquid flow rate generated greater interaction between jets. The number of orifices had a significant influence on droplet size. In general, the increase in the velocity of the liquid jet and in the gas velocity favored the atomization process by reducing the size of the droplets.

Deformation and breakup of liquid-liquid threads, jets, and drops

NASA Astrophysics Data System (ADS)

Doshi, Pankaj

The formation and breakup of two-fluid jets and drops find application in various industrially important processes like microencapsulation, inkjet printing, dispersion and emulsion formation, micro fluidics. Two important aspects of these problems are studied in this thesis. The first regards the study of the dynamics of a two-fluid jet issuing out of a concentric nozzle and breaking into multiple liquid drops. The second aspect concerns the study of the dynamics of liquid-liquid interface rupture. Highly robust and accurate numerical algorithms based on the Galerkin finite element method (G/FEM) and elliptic mesh generation technique are developed. The most important results of this research are the prediction of compound drop formation and volume partitioning between primary drop and satellite drops, which are of critical importance for microencapsulation technology. Another equally important result is computational and experimental demonstration of a self-similar behavior for the rupture of liquid-liquid interface. The final focus is the study of the pinch-off dynamics of generalized-Newtonian fluids with deformation-rate-dependent rheology using asymptotic analysis and numerical computation. A significant result is the first ever prediction of self-similar pinch-off of liquid threads of generalized Newtonian fluids.

Effects of supercritical environment on hydrocarbon-fuel injection

NASA Astrophysics Data System (ADS)

Shin, Bongchul; Kim, Dohun; Son, Min; Koo, Jaye

2017-04-01

In this study, the effects of environment conditions on decane were investigated. Decane was injected in subcritical and supercritical ambient conditions. The visualization chamber was pressurized to 1.68 MPa by using nitrogen gas at a temperature of 653 K for subcritical ambient conditions. For supercritical ambient conditions, the visualization chamber was pressurized to 2.52 MPa by using helium at a temperature of 653 K. The decane injection in the pressurized chamber was visualized via a shadowgraph technique and gradient images were obtained by a post processing method. A large variation in density gradient was observed at jet interface in the case of subcritical injection in subcritical ambient conditions. Conversely, for supercritical injection in supercritical ambient conditions, a small density gradient was observed at the jet interface. In a manner similar to that observed in other cases, supercritical injection in subcritical ambient conditions differed from supercritical ambient conditions such as sphere shape liquid. Additionally, there were changes in the interface, and the supercritical injection core width was thicker than that in the subcritical injection. Furthermore, in cases with the same injection conditions, the change in the supercritical ambient normalized core width was smaller than the change in the subcritical ambient normalized core width owing to high specific heat at the supercritical injection and small phase change at the interface. Therefore, the interface was affected by the changing ambient condition. Given that the effect of changing the thermodynamic properties of propellants could be essential for a variable thrust rocket engine, the effects of the ambient conditions were investigated experimentally.

Impact of Fluidic Chevrons on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Kinzie, Kevin W.; Whitmire, Julia; Abeysinghe, Amal

2005-01-01

The impact of alternating fluidic core chevrons on the production of jet noise is investigated. Core nozzles for a representative 1/9th scale, bypass ratio 5 model system were manufactured with slots cut near the trailing edges to allow for air injection into the core and fan streams. The injectors followed an alternating pattern around the nozzle perimeter so that the injection alternated between injection into the core stream and injection into the fan stream. For the takeoff condition and a forward flight Mach number of 0.10, the overall sound pressure levels at the peak jet noise angle decrease with increasing injection pressure. Sound pressure levels increase for observation angles less than 110o at higher injection pressures due to increases in high frequency noise. Greater increases in high frequency noise are observed when the number of injectors increases from 8 to 12. When the forward flight Mach number is increased to 0.28, jet noise reduction (relative to the baseline) is observed at aft angles for increasing injection pressure while significant increases in jet noise are observed at forward observation angles due to substantial acoustic radiation at high frequencies. A comparison between inflow and alternating injectors shows that, for equal mass injection rates, the inflow nozzle produces greater low frequency noise reduction (relative to the baseline) than the alternating injectors at 90o and aft observation angles and a forward flight Mach number of 0.28. Preliminary computational fluid dynamic simulations indicate that the spatial decay rate of the hot potential core flow is less for the inflow nozzle than for the alternating nozzles which indicates that gentle mixing may be preferred over sever mixing when fluidic chevrons are used for jet noise reduction.

Principles and applications of laser-induced liquid-phase jet-chemical etching

NASA Astrophysics Data System (ADS)

Stephen, Andreas; Metev, Simeon; Vollertsen, Frank

2003-11-01

In this treatment method laser radiation, which is guided from a coaxially expanding liquid jet-stream, locally initiates a thermochemical etching reaction on a metal surface, which leads to selective material removal at high resolution and quality of the treated surface as well as low thermal influence on the workpiece. Electrochemical investigations were performed under focused laser irradiation using a cw-Nd:YAG laser with a maximum power of 15 W and a simultaneous impact of the liquid jet-stream consisting of phosphoric acid with a maximum flow rate of 20 m/s. The time resolved measurements of the electrical potential difference against an electrochemical reference electrode were correlated with the specific processing parameters and corresponding etch rates to identify processing conditions for temporally stable and enhanced chemical etching reactions. Applications of laser-induced liquid-phase jet-chemical etching in the field of sensor technology, micromechanics and micrmoulding technology are presented. This includes the microstructuring of thin film systems, cutting of foils of shape memory alloys or the generation of structures with defined shape in bulk material.

Preliminary Investigation of Performance and Starting Characteristics of Liquid Fluorine : Liquid Oxygen Mixtures with Jet Fuel

NASA Technical Reports Server (NTRS)

Rothenberg, Edward A; Ordin, Paul M

1954-01-01

The performance of jet fuel with an oxidant mixture containing 70 percent liquid fluorine and 30 percent liquid oxygen by weight was investigated in a 500-pound-thrust engine operating at a chamber pressure of 300 pounds per square inch absolute. A one-oxidant-on-one-fuel skewed-hole impinging-jet injector was evaluated in a chamber of characteristic length equal to 50 inches. A maximum experimental specific impulse of 268 pound-seconds per pound was obtained at 25 percent fuel, which corresponds to 96 percent of the maximum theoretical specific impulse based on frozen composition expansion. The maximum characteristic velocity obtained was 6050 feet per second at 23 percent fuel, or 94 percent of the theoretical maximum. The average thrust coefficient was 1.38 for the 500-pound thrust combustion-chamber nozzle used, which was 99 percent of the theoretical (frozen) maximum. Mixtures of fluorine and oxygen were found to be self-igniting with jet fuel with fluorine concentrations as low as 4 percent, when low starting propellant flow rated were used.

Influence of spray nozzle shape upon atomization process

NASA Astrophysics Data System (ADS)

Beniuga, Marius; Mihai, Ioan

2016-12-01

The atomization process is affected by a number of operating parameters (pressure, viscosity, temperature, etc.) [1-6] and the adopted constructive solution. In this article are compared parameters of atomized liquid jet with two nozzles that have different lifespan, one being new and the other one out. The last statement shows that the second nozzle was monitored as time of operation on the one hand and on the other hand, two dimensional nozzles have been analyzed using laser profilometry. To compare the experimental parameters was carried an experimental stand to change the period and pulse width in injecting liquid through two nozzles. Atomized liquid jets were photographed and filmed quickly. Images obtained were analyzed using a Matlab code that allowed to determine a number of parameters that characterize an atomized jet. Knowing the conditions and operating parameters of atomized jet, will establish a new wastewater nozzle block of parameter values that can be implemented in controller that provides dosing of the liquid injected. Experimental measurements to observe the myriad forms of atomized droplets to a wide range of operating conditions, realized using the electronic control module.

Transition to turbulence and noise radiation in heated coaxial jet flows

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

Gloor, Michael, E-mail: gloor@ifd.mavt.ethz.ch; Bühler, Stefan; Kleiser, Leonhard

2016-04-15

Laminar-turbulent transition and noise radiation of a parametrized set of subsonic coaxial jet flows with a hot primary (core) stream are investigated numerically by Large-Eddy Simulation (LES) and direct noise computation. This study extends our previous research on local linear stability of heated coaxial jet flows by analyzing the nonlinear evolution of initially laminar flows disturbed by a superposition of small-amplitude unstable eigenmodes. First, a baseline configuration is studied to shed light on the flow dynamics of coaxial jet flows. Subsequently, LESs are performed for a range of Mach and Reynolds numbers to systematically analyze the influences of the temperaturemore » and the velocity ratios between the primary and the secondary (bypass) stream. The results provide a basis for a detailed analysis of fundamental flow-acoustic phenomena in the considered heated coaxial jet flows. Increasing the primary-jet temperature leads to an increase of fluctuation levels and to an amplification of far-field noise, especially at low frequencies. Strong mixing between the cold bypass stream and the hot primary stream as well as the intermittent character of the flow field at the end of the potential core lead to a pronounced noise radiation at an aft angle of approximately 35{sup ∘}. The velocity ratio strongly affects the shear-layer development and therefore also the noise generation mechanisms. Increasing the secondary-stream velocity amplifies the dominance of outer shear-layer perturbations while the disturbance growth rates in the inner shear layer decrease. Already for r{sub mic} > 40R{sub 1}, where r{sub mic} is the distance from the end of the potential core and R{sub 1} is the core-jet radius, a perfect 1/r{sub mic} decay of the sound pressure amplitudes is observed. The potential-core length increases for higher secondary-stream velocities which leads to a shift of the center of the dominant acoustic radiation in the downstream direction.« less

Spitting cobras: fluid jets in nature as models for technical applications

NASA Astrophysics Data System (ADS)

Balmert, Alexander; Hess, David; Brücker, Christoph; Bleckmann, Horst; Westhoff, Guido

2011-04-01

Spitting cobras defend themselves by ejecting rapid jets of venom through their fangs towards the face of an offender. To generate these jets, the venom delivery system of spitting cobras has some unique adaptations, such as prominent ridges on the surface of the venom channel. We examined the fluid acceleration mechanisms in three spitting cobra species of the genus Naja. To investigate the liquid-flow through the venom channel we built a three-dimensional 60:1 scale model. First we determined the three-dimensional structure of the channel by using microcomputer tomography. With help of the micro computer tomographical data we then created a negative form out of wax. Finally, silicon was casted around the wax form and the wax removed, resulting in a completely transparent model of the cobrás venom channel. The physical-chemical properties of the cobra venom were measured by micro rheometry and tensiometry. Thereafter, an artificial fluid with similar properties was generated. Particle image velocimetry (PIV) was performed to visualize the flow of the artificial liquid in the three-dimensional model. Our experiments show how the surface structure of the venom channel determines the liquid flow through the channel and ultimately the form of the liquid jet. Understanding the biological mechanisms of venom ejection helps to enhance industrial processes such as water jet cutting and cleaning as well as injection methods in technical and medical sectors, e.g. liquid microjet dissection in microsurgery.

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 ¼″ 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.

Continuous-wave laser generated jets for needle free applications

PubMed Central

Visser, Claas Willem; Schlautmann, Stefan

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 250 μm and chamber size of 700 μm were obtained. The proposed CW laser-based device is potentially a compact option for a practical and commercially feasible needle-free injector. PMID:26858816

Reversing cooling flows with AGN jets: shock waves, rarefaction waves and trailing outflows

NASA Astrophysics Data System (ADS)

Guo, Fulai; Duan, Xiaodong; Yuan, Ye-Fei

2018-01-01

The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains highly debated. Using an idealized simulation of a cool-core cluster, we study the development of central cooling catastrophe and how a subsequent powerful AGN jet event averts cooling flows, with a focus on complex gasdynamical processes involved. We find that the jet drives a bow shock, which reverses cooling inflows and overheats inner cool-core regions. The shocked gas moves outward in a rarefaction wave, which rarefies the dense core and adiabatically transports a significant fraction of heated energy to outer regions. As the rarefaction wave propagates away, inflows resume in the cluster core, but a trailing outflow is uplifted by the AGN bubble, preventing gas accumulation and catastrophic cooling in central regions. Inflows and trailing outflows constitute meridional circulations in the cluster core. At later times, trailing outflows fall back to the cluster centre, triggering central cooling catastrophe and potentially a new generation of AGN feedback. We thus envisage a picture of cool cluster cores going through cycles of cooling-induced contraction and AGN-induced expansion. This picture naturally predicts an anti-correlation between the gas fraction (or X-ray luminosity) of cool cores and the central gas entropy, which may be tested by X-ray observations.

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.

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

PubMed

Larsson, Daniel H; Lundström, Ulf; Westermark, Ulrica K; Arsenian Henriksson, Marie; Burvall, Anna; Hertz, Hans M

2013-02-01

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. 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 ∼7 μm x-ray spots, providing high spatial resolution in absorption imaging and high spatial coherence for the phase-contrast imaging. High-resolution absorption imaging is demonstrated on mice with CT, showing 50 μm 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. 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.

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.

Leaping shampoo glides on a 500-nm-thick lubricating air layer

NASA Astrophysics Data System (ADS)

Li, Erqiang; Lee, Sanghyun; Marston, Jeremy; Bonito, Andrea; Thoroddsen, Sigurdur

2013-11-01

When a stream of shampoo is fed onto a pool in one's hand, a jet can leap sideways or rebound from the liquid surface in an intriguing phenomenon known as the Kaye effect. Earlier studies have debated whether non-Newtonian effects are the underlying cause of this phenomenon, making the jet glide on top of a shear-thinning liquid layer, or whether an entrained air layer is responsible. Herein we show unambiguously that the jet slides on a lubricating air layer [Lee et al., Phys. Rev. E 87, 061001 (2013)]. We identify this layer by looking through the pool liquid and observing its rupture into fine micro-bubbles. The resulting micro-bubble sizes suggest that the thickness of this air layer is around 500 nm. This thickness estimate is also supported by the tangential deceleration of the jet during the rebounding, with the shear stress within the thin air layer sufficient for the observed deceleration. Particle tracking within the jet shows uniform velocity, with no pronounced shear, which would be required for shear-thinning effects. The role of the surfactant may primarily be to stabilize the air film.

Cavitation induced by high speed impact of a solid surface on a liquid jet

NASA Astrophysics Data System (ADS)

Farhat, Mohamed; Tinguely, Marc; Rouvinez, Mathieu

2009-11-01

A solid surface may suffer from severe erosion if it impacts a liquid jet at high speed. The physics behind the erosion process remains unclear. In the present study, we have investigated the impact of a gun bullet on a laminar water jet with the help of a high speed camera. The bullet has a flat front and 11 mm diameter, which is half of jet diameter. The impact speed was varied between 200 and 500 ms-1. Immediately after the impact, a systematic shock wave and high speed jetting were observed. As the compression waves reflect on the jet boundary, a spectacular number of vapour cavities are generated within the jet. Depending on the bullet velocity, these cavities may grow and collapse violently on the bullet surface with a risk of cavitation erosion. We strongly believe that this transient cavitation is the main cause of erosion observed in many industrial applications such as Pelton turbines.

Electric field induced sheeting and breakup of dielectric liquid jets

NASA Astrophysics Data System (ADS)

Khoshnevis, Ahmad; Tsai, Scott S. H.; Esmaeilzadeh, Esmaeil

2014-01-01

We report experimental observations of the controlled deformation of a dielectric liquid jet subjected to a local high-voltage electrostatic field in the direction normal to the jet. The jet deforms to the shape of an elliptic cylinder upon application of a normal electrostatic field. As the applied electric field strength is increased, the elliptic cylindrical jet deforms permanently into a flat sheet, and eventually breaks-up into droplets. We interpret this observation—the stretch of the jet is in the normal direction to the applied electric field—qualitatively using the Taylor-Melcher leaky dielectric theory, and develop a simple scaling model that predicts the critical electric field strength for the jet-to-sheet transition. Our model shows a good agreement with experimental results, and has a form that is consistent with the classical drop deformation criterion in the Taylor-Melcher theory. Finally, we statistically analyze the resultant droplets from sheet breakup, and find that increasing the applied electric field strength improves droplet uniformity and reduces droplet size.

An experimental study of a plunging liquid jet induced air carryunder and dispersion

NASA Astrophysics Data System (ADS)

Bonetto, F.; Drew, D. A.; Lahey, R. T., Jr.

1993-03-01

A good understanding of the air carryunder and bubble dispersion process associated with a plunging liquid jet is vital if one is to be able to quantify such diverse phenomena as sea surface chemistry, the meteorological significance of breaking ocean waves (e.g., mitigation of the greenhouse effect due to the absorption of CO2 by the oceans), the performance of certain type of chemical reactors, and a number of other important maritime-related applications. The absorption of greenhouse gases into the ocean has been hypothesized to be highly dependent upon the air carryunder that occurs due to breaking waves. This process can be approximated with a plunging liquid jet. Moreover, the air entrainment process due to the breaking bow waves of surface ships may cause long (i.e., up to 5 km in length) wakes. Naturally, easily detectable wakes are undesirable for naval warships. In addition, the air carryunder that occurs at most hydraulic structures in rivers is primarily responsible for the large air/water mass transfer that is associated with these structures. Also, air entrainment plays an important role in the slug flow regime. In particular, the liquid film surrounding a Taylor bubble has a flow in the opposite direction from the Taylor bubble. This liquid film can be thought of as a plunging liquid jet that produces a surface depression in the rear part of the Taylor bubble.

Identification of a BrOOO- intermediate species in the ozonolysis of bromide at the liquid/vapor interface from liquid jet XPS

NASA Astrophysics Data System (ADS)

Chen, Shuzhen; Artiglia, Luca; Orlando, Fabrizio; Corral-Arroyo, Pablo; Edebeli, Jacinta; Ammann, Markus

2017-04-01

Oxidation of bromide by gas phase ozone (O3) in the absence of photochemistry is believed to be one of the important dark reactions to produce HOBr as the starting point of the multiphase cycling reaction mechanisms that release bromide out of sea water, sea spray or marine aerosols from aqueous solution that later drive O3 depleting chemistry in the troposphere [1]. The reaction of bromide with O3 occurs through an acid catalyzed mechanism involving a BrOOO- complex as an intermediate [2]. Slow oxidation of bromide by O3 in the bulk aqueous phase is of limited relevance; previous kinetic experiments have suspected the reaction to be enhanced at the surface of aqueous solutions. Thus, identifying BrOOO- at the interface would be a major step to understanding the multiphase oxidation of bromide with O3. Here, we provide a direct experimental evidence for the formation of a BrOOO- reaction intermediate at the surface by investigating the reaction of aqueous solutions NaBr with gas phase O3 after millisecond time scale exposure using the surface sensitive in situ liquid jet X-ray photoelectron spectroscopy (XPS) at the Swiss Light Source (SLS). We acquired Br 3d core level spectra of 0.125 M NaBr solution in presence and absence of ozone in the gas phase. We found a new feature with a peak position shifted towards higher binding energy (by ˜0.7 eV) compared to Br-, which was clearly different from the Br 3d core levels spectra of hypobromite and bromate measured with reference solutions. Our results suggest the appearance of the formation of the BrOOO- reaction intermediate as a new component, in agreement with theoretical calculations of the Br- ozonolysis mechanism [3]. Additionally, by varying the photoelectron kinetic energy and thus probe depth via variation of the probing photon energy, the new feature appears to be present near the liquid/vapor interface. Besides, kinetic experiments for the reaction of O3 with bromide are ongoing to investigate the dependence on the temperature, ozone concentration, which may give further information such as the relative oxidation rate at the liquid/vapor interface versus that in the bulk phase. [1] S. Wang, et al., Proceedings of the National Academy of Sciences, 2015, 112, 9281-9286. [2] Q. Liu, et al., Inorganic Chemistry, 2001, 40, 4436-4442. [3] I. Gladich, et al., The Journal of Physical Chemistry A, 2015, 119, 4482-4488.

Toward jet injection by continuous-wave laser cavitation

NASA Astrophysics Data System (ADS)

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

2017-10-01

This is a study motivated by the need to develop a needle-free device for eliminating major global healthcare problems caused by needles. The generation of liquid jets by means of a continuous-wave laser, focused into a light absorbing solution, was studied with the aim of developing a portable and affordable jet injector. We designed and fabricated glass microfluidic devices, which consist of a chamber where thermocavitation is created and a tapered channel. The growth of a vapor bubble displaces and expels the liquid through the channel as a fast traveling jet. Different parameters were varied with the purpose of increasing the jet velocity. The velocity increases with smaller channel diameters and taper ratios, whereas larger chambers significantly reduce the jet speed. It was found that the initial position of the liquid-air meniscus interface and its dynamics contribute to increased jet velocities. A maximum velocity of 94±3 m/s for a channel diameter of D=120 μm, taper ratio n=0.25, and chamber length E=200 μm was achieved. Finally, agarose gel-based skin phantoms were used to demonstrate the potential of our devices to penetrate the skin. The maximum penetration depth achieved was ˜1 mm, which is sufficient to penetrate the stratum corneum and for most medical applications. A meta-analysis shows that larger injection volumes will be required as a next step to medical relevance for laser-induced jet injection techniques in general.

Kinematics of Parsec-scale Jets of Gamma-Ray Blazars at 43 GHz within the VLBA-BU-BLAZAR Program

NASA Astrophysics Data System (ADS)

Jorstad, Svetlana G.; Marscher, Alan P.; Morozova, Daria A.; Troitsky, Ivan S.; Agudo, Iván; Casadio, Carolina; Foord, Adi; Gómez, José L.; MacDonald, Nicholas R.; Molina, Sol N.; Lähteenmäki, Anne; Tammi, Joni; Tornikoski, Merja

2017-09-01

We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of a sample of γ-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43 GHz. In a total of 1929 images, we measure apparent speeds of 252 emission knots in 21 quasars, 12 BL Lacertae objects (BLLacs), and 3 radio galaxies, ranging from 0.02c to 78c; 21% of the knots are quasi-stationary. Approximately one-third of the moving knots execute non-ballistic motions, with the quasars exhibiting acceleration along the jet within 5 pc (projected) of the core, and knots in BLLacs tending to decelerate near the core. Using the apparent speeds of the components and the timescales of variability from their light curves, we derive the physical parameters of 120 superluminal knots, including variability Doppler factors, Lorentz factors, and viewing angles. We estimate the half-opening angle of each jet based on the projected opening angle and scatter of intrinsic viewing angles of knots. We determine characteristic values of the physical parameters for each jet and active galactic nucleus class based on the range of values obtained for individual features. We calculate the intrinsic brightness temperatures of the cores, {T}{{b},{int}}{core}, at all epochs, finding that the radio galaxies usually maintain equipartition conditions in the cores, while ˜30% of {T}{{b},{int}}{core} measurements in the quasars and BLLacs deviate from equipartition values by a factor >10. This probably occurs during transient events connected with active states. In the Appendix, we briefly describe the behavior of each blazar during the period analyzed.

Formation and crystallisation of a liquid jet in a film exposed to a tightly focused laser beam

NASA Astrophysics Data System (ADS)

Anisimov, S. I.; Zhakhovsky, V. V.; Inogamov, N. A.; Murzov, S. A.; Khokhlov, V. A.

2017-06-01

This paper considers the effect of an ultrashort laser pulse on a thin gold film on a glass substrate at a focal spot size near 1 μm. We analyse the motion and thermal history of a film that has peeled off from the substrate in the heating spot as a consequence of melting. The detached zone is shown to form a domeshaped bump whose motion is hindered by surface tension. After the dome stops and turns back, towards the substrate, a jet begins to grow on its top. Concurrently, because of the heat dissipation in the film, melt recrystallisation begins, involving first the dome and then the jet. The liquid part of the jet elongates and breaks up into droplets because of the Plateau-Rayleigh instability development. The formation of a neck and the detachment of the last droplet occur in the solidification zone between the crystalline and liquid parts of the jet. The propagation of the crystallisation zone in the jet leads the necking process, so neck disruption occurs in the solid phase under nonequilibrium crystallisation conditions (the melt temperature is hundreds of kelvins lower than the melting point), at limiting mechanical stress and at high deformation rates. As a result, the jet transforms into a high needle with an extremely small tip radius (a few nanometres).

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.

Mixing of an Airblast-atomized Fuel Spray Injected into a Crossflow of Air

NASA Technical Reports Server (NTRS)

Leong, May Y.; McDonell, Vincent G.; Samuelsen, G. Scott

2000-01-01

The injection of a spray of fuel droplets into a crossflow of air provides a means of rapidly mixing liquid fuel and air for combustion applications. Injecting the liquid as a spray reduces the mixing length needed to accommodate liquid breakup, while the transverse injection of the spray into the air stream takes advantage of the dynamic mixing induced by the jet-crossflow interaction. The structure of the spray, formed from a model plain-jet airblast atomizer, is investigated in order to determine and understand the factors leading to its dispersion. To attain this goal, the problem is divided into the following tasks which involve: (1) developing planar imaging techniques that visualize fuel and air distributions in the spray, (2) characterizing the airblast spray without a crossflow, and (3) characterizing the airblast spray upon injection into a crossflow. Geometric and operating conditions are varied in order to affect the atomization, penetration, and dispersion of the spray into the crossflow. The airblast spray is first characterized, using imaging techniques, as it issues into a quiescent environment. The spray breakup modes are classified in a liquid Reynolds number versus airblast Weber number regime chart. This work focuses on sprays formed by the "prompt" atomization mode, which induces a well-atomized and well-dispersed spray, and which also produces a two-lobed liquid distribution corresponding to the atomizing air passageways in the injector. The characterization of the spray jet injected into the crossflow reveals the different processes that control its dispersion. Correlations that describe the inner and outer boundaries of the spray jet are developed, using the definition of a two-phase momentum-flux ratio. Cross-sections of the liquid spray depict elliptically-shaped distributions, with the exception of the finely-atomized sprays which show kidney-shaped distributions reminiscent of those obtained in gaseous jet in crossflow systems. A droplet trajectory analysis overpredicts the liquid mass penetration, and indicates a need for a more rigorous model to account for the three-dimensional mixing field induced by the jet-crossflow interaction. Nonetheless, the general procedures and criteria that are outlined can be used to efficiently assess and compare the quality of sprays formed under different conditions.

Numerical study on the splitting of a vapor bubble in the ultrasonic assisted EDM process with the curved tool and workpiece.

PubMed

Shervani-Tabar, M T; Seyed-Sadjadi, M H; Shabgard, M R

2013-01-01

Electrical discharge machining (EDM) is a powerful and modern method of machining. In the EDM process, a vapor bubble is generated between the tool and the workpiece in the dielectric liquid due to an electrical discharge. In this process dynamic behavior of the vapor bubble affects machining process. Vibration of the tool surface affects bubble behavior and consequently affects material removal rate (MRR). In this paper, dynamic behavior of the vapor bubble in an ultrasonic assisted EDM process after the appearance of the necking phenomenon is investigated. It is noteworthy that necking phenomenon occurs when the bubble takes the shape of an hour-glass. After the appearance of the necking phenomenon, the vapor bubble splits into two parts and two liquid jets are developed on the boundaries of the upper and lower parts of the vapor bubble. The liquid jet developed on the upper part of the bubble impinges to the tool and the liquid jet developed on the lower part of the bubble impinges to the workpiece. These liquid jets cause evacuation of debris from the gap between the tool and the workpiece and also cause erosion of the workpiece and the tool. Curved tool and workpiece affect the shape and the velocity of the liquid jets during splitting of the vapor bubble. In this paper dynamics of the vapor bubble after its splitting near the curved tool and workpiece is investigated in three cases. In the first case surfaces of the tool and the workpiece are flat, in the second case surfaces of the tool and the workpiece are convex and in the third case surfaces of the tool and workpiece are concave. Numerical results show that in the third case, the velocity of liquid jets which are developed on the boundaries of the upper and lower parts of the vapor bubble after its splitting have the highest magnitude and their shape are broader than the other cases. Copyright © 2012 Elsevier B.V. All rights reserved.

High-speed monodisperse droplet generation by ultrasonically controlled micro-jet breakup

NASA Astrophysics Data System (ADS)

Frommhold, Philipp Erhard; Lippert, Alexander; Holsteyns, Frank Ludwig; Mettin, Robert

2014-04-01

A liquid jet that is ejected from a nozzle into air will disintegrate into drops via the well-known Plateau-Rayleigh instability within a certain range of Ohnesorge and Reynolds numbers. With the focus on the micrometer scale, we investigate the control of this process by superimposing a suitable ultrasonic signal, which causes the jet to break up into a very precise train of monodisperse droplets. The jet leaves a pressurized container of liquid via a small orifice of about 20 μm diameter. The break-up process and the emerging droplets are recorded via high-speed imaging. An extended parameter study of exit speed and ultrasonic frequency is carried out for deionized water to evaluate the jet's state and the subsequent generation of monodisperse droplets. Maximum exit velocities obtained reach almost 120 m s-1, and frequencies have been applied up to 1.8 MHz. Functionality of the method is confirmed for five additional liquids for moderate jet velocities 38 m s-1. For the uncontrolled jet disintegration, the drop size spectra revealed broad distributions and downstream drop growth by collision, while the acoustic control generated monodisperse droplets with a standard deviation less than 0.5 %. By adjustment of the acoustic excitation frequency, drop diameters could be tuned continuously from about 30 to 50 μm for all exit speeds. Good agreement to former experiments and theoretical approaches is found for the relation of overpressure and jet exit speed, and for the observed stability regions of monodisperse droplet generation in the parameter plane of jet speed and acoustic excitation frequency. Fitting of two free parameters of the general theory to the liquids and nozzles used is found to yield an even higher precision. Furthermore, the high-velocity instability limit of regular jet breakup described by von Ohnesorge has been superseded by more than a factor of two without entering the wind-induced instability regime, and monodisperse droplet generation was always achievable. Thus, the reliable and robust realization of tunable high-speed monodisperse micro-droplet trains is demonstrated. Some implication for applications is discussed.

Ultrahigh throughput microfluidic platform for in-air production of microscale droplets

NASA Astrophysics Data System (ADS)

Tirandazi, Pooyan; Healy, John; Hidrovo, Carlos H.

2017-11-01

In-air droplet formation inside microfluidic networks is an alternative technique to the conventional in-liquid systems for creating uniform, microscale droplets. Recent works have highlighted and quantified the use of a gaseous continuous phase for controlled generation of droplets in the Dripping regime in planar structures. Here we demonstrate a new class of non-planar droplet-based systems which rely on controlled breakup of a liquid microjet within a high speed flow of air inside a confined microfluidic flow-focusing PDMS channel. We investigate the physics of confined gas-liquid flows and the effect of geometry on the behavior of a liquid water jet in a gaseous flow. Droplet breakup in the Jetting regime is studied both numerically and experimentally and the results are compared. We show droplet production capability at rates higher than 100 KHz with droplets ranging from 15-30 μm in diameter and a polydispersity index of less than 15%. This work represents an important investigation into the Jetting regime in confined microchannels. The ability to control jet behavior, generation rate, and droplet size in gas-liquid microflows will further expand the potential applications of this system for high throughput operations in material synthesis and biochemical analysis. We acknowledge funding support from NSF CAREER Award Grant CBET-1522841.

Laser-induced jet formation in liquid films

NASA Astrophysics Data System (ADS)

Brasz, Frederik; Arnold, Craig

2014-11-01

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

Main lines of scientific and technical research at the Soviet Jet Propulsion Research Institute (RNII), 1933 - 1942

NASA Technical Reports Server (NTRS)

Shchetinkov, Y. S.

1977-01-01

The rapid development of rocketry in the U.S.S.R. during the post-war years was due largely to pre-war activity; in particular, to investigations conducted in the Jet Propulsion Research Institute (RNII). The history of RNII commenced in 1933, resulting from the merger of two rocket research organizations. Previous research was continued in areas of solid-propellant rockets, jet-assisted take-off of aircraft, liquid propellant engines (generally with nitric acid as the oxidizer), liquid-propellant rockets (generally with oxgen as the oxidizer), ram jet engines, rockets with and without wings, and rocket planes. RNII research is described and summarized for the years 1933-1942.

Initial drop size and velocity distributions for airblast coaxial atomizers

NASA Technical Reports Server (NTRS)

Eroglu, H.; Chigier, N.

1991-01-01

Phase Doppler measurements were used to determine initial drop size and velocity distributions after a complete disintegration of coaxial liquid jets. The Sauter mean diameter (SMD) distribution was found to be strongly affected by the structure and behavior of the preceding liquid intact jet. The axial measurement stations were determined from the photographs of the coaxial liquid jet at very short distances (1-2 mm) downstream of the observed break-up locations. Minimum droplet mean velocities were found at the center, and maximum velocities were near the spray boundary. Size-velocity correlations show that the velocity of larger drops did not change with drop size. Drop rms velocity distributions have double peaks whose radial positions coincide with the maximum mean velocity gradients.

Formation of liquid-metal jets in a vacuum arc cathode spot: Analogy with drop impact on a solid surface

NASA Astrophysics Data System (ADS)

Gashkov, M. A.; Zubarev, N. M.

2018-01-01

Conditions of the liquid-metal jets formation in a cathode spot of a vacuum arc discharge are studied. Our consideration is based on the analogy between the processes, occurring in the liquid phase of the cathode spot, and the processes, accompanying a liquid drop impact on a flat solid surface. In the latter case there exists a wide variety of experimental data on the conditions under which the spreading regime of fluid motion (i.e., without formation of jets and secondary droplets) changes into the splashing one. In the present work, using the hydrodynamic similarity principle (processes in geometrically similar systems will proceed similarly when their Weber and Reynolds numbers coincide), criteria for molten metal splashing are formulated for different materials of the cathode. They are compared with the experimental data on the threshold conditions for vacuum arc burning.

Keyhole and weld shapes for plasma arc welding under normal and zero gravity

NASA Technical Reports Server (NTRS)

Keanini, R. G.; Rubinsky, B.

1990-01-01

A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

Measurements and Predictions of the Noise from Three-Stream Jets

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Leib, Stewart J.; Wernet, Mark P.

2015-01-01

An experimental and numerical investigation of the noise produced by high-subsonic and supersonic three-stream jets was conducted. The exhaust system consisted of externally-mixed-convergent nozzles and an external plug. Bypass- and tertiary-to-core area ratios between 1.0 and 2.5, and 0.4 and 1.0, respectively, were studied. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated conditions. For axisymmetric configurations, the addition of the third stream was found to reduce peak- and high-frequency acoustic levels in the peak-jet-noise direction, with greater reductions at the lower bypass-to-core area ratios. For the offset configurations, an offset duct was found to decrease acoustic levels on the thick side of the tertiary nozzle relative to those produced by the simulated two-stream jet with up to 8 dB mid-frequency noise reduction at large angles to the jet inlet axis. Noise reduction in the peak-jet-noise direction was greater for supersonic core speeds than for subsonic core speeds. The addition of a tertiary nozzle insert used to divert the third-stream jet to one side of the nozzle system provided no noise reduction. Noise predictions are presented for selected cases using a method based on an acoustic analogy with mean flow interaction effects accounted for using a Green's function, computed in terms of its coupled azimuthal modes for the offset cases, and a source model previously used for round and rectangular jets. Comparisons of the prediction results with data show that the noise model predicts the observed increase in low-frequency noise with the introduction of a third, axisymmetric stream, but not the high-frequency reduction. For an offset third stream, the model predicts the observed trend of decreased sound levels on the thick side of the jet compared with the thin side, but the predicted azimuthal variations are much less than those seen in the data. Also, the shift of the spectral peak to lower frequencies with increasing polar angle is over-predicted. For an offset third stream with a heated core, it is shown that including the enthalpy-flux source terms in the acoustic analogy model improves predictions compared with those obtained using only the momentum flux.

Measurements and Predictions of the Noise from Three-Stream Jets

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Leib, Stewart J.; Wernet, Mark P.

2015-01-01

An experimental and numerical investigation of the noise produced by high-subsonic and supersonic three-stream jets was conducted. The exhaust system consisted of externally-mixed-convergent nozzles and an external plug. Bypass- and tertiary- to-core area ratios between 1.0 and 2.5, and 0.4 and 1.0, respectively, were studied. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated conditions. For axisymmetric configurations, the addition of the third stream was found to reduce peak- and high-frequency acoustic levels in the peak-jet-noise direction, with greater reductions at the lower bypass-to-core area ratios. For the offset configurations, an offset duct was found to decrease acoustic levels on the thick side of the tertiary nozzle relative to those produced by the simulated two-stream jet with up to 8 dB mid-frequency noise reduction at large angles to the jet inlet axis. Noise reduction in the peak-jet-noise direction was greater for supersonic core speeds than for subsonic core speeds. The addition of a tertiary nozzle insert used to divert the third-stream jet to one side of the nozzle system provided no noise reduction. Noise predictions are presented for selected cases using a method based on an acoustic analogy with mean flow interaction effects accounted for using a Green's function, computed in terms of its coupled azimuthal modes for the offset cases, and a source model previously used for round and rectangular jets. Comparisons of the prediction results with data show that the noise model predicts the observed increase in low-frequency noise with the introduction of a third, axisymmetric stream, but not the high-frequency reduction. For an offset third stream, the model predicts the observed trend of decreased sound levels on the thick side of the jet compared with the thin side, but the predicted azimuthal variations are much less than those seen in the data. Also, the shift of the spectral peak to lower frequencies with increasing polar angle is over-predicted. For an offset third stream with a heated core, it is shown that including the enthalpy-flux source terms in the acoustic analogy model improves predictions compared with those obtained using only the momentum- flux.

Effect of Liquid Surface Turbulent Motion on the Vapor Condensation in a Mixing Tank

NASA Technical Reports Server (NTRS)

Lin, C. S.; Hasan, M. M.

1991-01-01

The effect of liquid surface motion on the vapor condensation in a tank mixed by an axial turbulent jet is numerically investigated. The average value (over the interface area) of the root-mean-squared (rms) turbulent velocity at the interface is shown to be linearly increasing with decreasing liquid height and increasing jet diameter for a given tank size. The average rms turbulent velocity is incorporated in Brown et al. (1990) condensation correlation to predict the condensation of vapor on a liquid surface. The results are in good agreement with available condensation data.

High fidelity simulation and analysis of liquid jet atomization in a gaseous crossflow at intermediate Weber numbers

NASA Astrophysics Data System (ADS)

Li, Xiaoyi; Soteriou, Marios C.

2016-08-01

Recent advances in numerical methods coupled with the substantial enhancements in computing power and the advent of high performance computing have presented first principle, high fidelity simulation as a viable tool in the prediction and analysis of spray atomization processes. The credibility and potential impact of such simulations, however, has been hampered by the relative absence of detailed validation against experimental evidence. The numerical stability and accuracy challenges arising from the need to simulate the high liquid-gas density ratio across the sharp interfaces encountered in these flows are key reasons for this. In this work we challenge this status quo by presenting a numerical model able to deal with these challenges, employing it in simulations of liquid jet in crossflow atomization and performing extensive validation of its results against a carefully executed experiment with detailed measurements in the atomization region. We then proceed to the detailed analysis of the flow physics. The computational model employs the coupled level set and volume of fluid approach to directly capture the spatiotemporal evolution of the liquid-gas interface and the sharp-interface ghost fluid method to stably handle high liquid-air density ratio. Adaptive mesh refinement and Lagrangian droplet models are shown to be viable options for computational cost reduction. Moreover, high performance computing is leveraged to manage the computational cost. The experiment selected for validation eliminates the impact of inlet liquid and gas turbulence and focuses on the impact of the crossflow aerodynamic forces on the atomization physics. Validation is demonstrated by comparing column surface wavelengths, deformation, breakup locations, column trajectories and droplet sizes, velocities, and mass rates for a range of intermediate Weber numbers. Analysis of the physics is performed in terms of the instability and breakup characteristics and the features of downstream flow recirculation, and vortex shedding. Formation of "Λ" shape windward column waves is observed and explained by the combined upward and lateral surface motion. The existence of Rayleigh-Taylor instability as the primary mechanism for the windward column waves is verified for this case by comparing wavelengths from the simulations to those predicted by linear stability analyses. Physical arguments are employed to postulate that the type of instability manifested may be related to conditions such as the gas Weber number and the inlet turbulence level. The decreased column wavelength with increasing Weber number is found to cause enhanced surface stripping and early depletion of liquid core at higher Weber number. A peculiar "three-streak-two-membrane" liquid structure is identified at the lowest Weber number and explained as the consequence of the symmetric recirculation zones behind the jet column. It is found that the vortical flow downstream of the liquid column resembles a von Karman vortex street and that the coupling between the gas flow and droplet transport is weak for the conditions explored.

High fidelity simulation and analysis of liquid jet atomization in a gaseous crossflow at intermediate Weber numbers

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

Li, Xiaoyi, E-mail: lixy2@utrc.utc.com; Soteriou, Marios C.

Recent advances in numerical methods coupled with the substantial enhancements in computing power and the advent of high performance computing have presented first principle, high fidelity simulation as a viable tool in the prediction and analysis of spray atomization processes. The credibility and potential impact of such simulations, however, has been hampered by the relative absence of detailed validation against experimental evidence. The numerical stability and accuracy challenges arising from the need to simulate the high liquid-gas density ratio across the sharp interfaces encountered in these flows are key reasons for this. In this work we challenge this status quomore » by presenting a numerical model able to deal with these challenges, employing it in simulations of liquid jet in crossflow atomization and performing extensive validation of its results against a carefully executed experiment with detailed measurements in the atomization region. We then proceed to the detailed analysis of the flow physics. The computational model employs the coupled level set and volume of fluid approach to directly capture the spatiotemporal evolution of the liquid-gas interface and the sharp-interface ghost fluid method to stably handle high liquid-air density ratio. Adaptive mesh refinement and Lagrangian droplet models are shown to be viable options for computational cost reduction. Moreover, high performance computing is leveraged to manage the computational cost. The experiment selected for validation eliminates the impact of inlet liquid and gas turbulence and focuses on the impact of the crossflow aerodynamic forces on the atomization physics. Validation is demonstrated by comparing column surface wavelengths, deformation, breakup locations, column trajectories and droplet sizes, velocities, and mass rates for a range of intermediate Weber numbers. Analysis of the physics is performed in terms of the instability and breakup characteristics and the features of downstream flow recirculation, and vortex shedding. Formation of “Λ” shape windward column waves is observed and explained by the combined upward and lateral surface motion. The existence of Rayleigh-Taylor instability as the primary mechanism for the windward column waves is verified for this case by comparing wavelengths from the simulations to those predicted by linear stability analyses. Physical arguments are employed to postulate that the type of instability manifested may be related to conditions such as the gas Weber number and the inlet turbulence level. The decreased column wavelength with increasing Weber number is found to cause enhanced surface stripping and early depletion of liquid core at higher Weber number. A peculiar “three-streak-two-membrane” liquid structure is identified at the lowest Weber number and explained as the consequence of the symmetric recirculation zones behind the jet column. It is found that the vortical flow downstream of the liquid column resembles a von Karman vortex street and that the coupling between the gas flow and droplet transport is weak for the conditions explored.« less

The rotational shear in pre-collapse cores of massive stars

NASA Astrophysics Data System (ADS)

Zilberman, Noa; Gilkis, Avishai; Soker, Noam

2018-02-01

We evolve stellar models to study the rotational profiles of the pre-explosion cores of single massive stars that are progenitors of core collapse supernovae (CCSNe), and find large rotational shear above the iron core that might play an important role in the jet feedback explosion mechanism by amplifying magnetic fields before and after collapse. Initial masses of 15 and 30 M⊙ and various values of the initial rotation velocity are considered, as well as a reduced mass-loss rate along the evolution and the effect of core-envelope coupling through magnetic fields. We find that the rotation profiles just before core collapse differ between models, but share the following properties. (1) There are narrow zones of very large rotational shear adjacent to convective zones. (2) The rotation rate of the inner core is slower than required to form a Keplerian accretion disc. (3) The outer part of the core and the envelope have non-negligible specific angular momentum compared to the last stable orbit around a black hole (BH). Our results suggest the feasibility of magnetic field amplification which might aid a jet-driven explosion leaving behind a neutron star. Alternatively, if the inner core fails in exploding the star, an accretion disc from the outer parts of the core might form and lead to a jet-driven CCSN which leaves behind a BH.

Receptivity of a precessing vortex core to open-loop forcing in a swirling jet and its predictability by linear stability adjoint theory

NASA Astrophysics Data System (ADS)

Müller, Jens; Lückoff, Finn; Oberleithner, Kilian

2017-11-01

The precessing vortex core (PVC) is a dominant coherent structure which occurs in swirling jets such as in swirl-stabilised gas turbine combustors. It stems from a global hydrodynamic instability caused by an internal feedback mechanism within the jet core. In this work, open-loop forcing is applied to a generic non-reacting swirling jet to investigate its receptivity to external actuation regarding lock-in behaviour of the PVC for different streamwise positions and Reynolds numbers. The forcing is periodically exerted by zero net mass flux synthetic jets which are introduced radially through slits inside the duct walls upstream of the swirling jet's exit plane. Time-resolved pressure measurements are conducted to identify the PVC frequency and stereo PIV combined with proper orthogonal decomposition in the duct and free field is used to extract the mean flow and the PVC mode. The data is used in a global linear stability framework to gain the adjoint of the PVC which reveals the regions of highest receptivity to periodic forcing based on mean flow input only. This theoretical receptivity model is compared with the experimentally obtained receptivity results and the validity and applicability of the adjoint model for the prediction of optimal forcing positions is discussed.

Particle-Laden Liquid Jet Impingement on a Moving Substrate

NASA Astrophysics Data System (ADS)

Rahmani, Hatef; Green, Sheldon

2017-11-01

The impingement of high-speed jets on a moving substrate is salient to a number of industrial processes such as surface coating in the railroad industry. The particular jet fluids studied were dilute suspensions of neutrally buoyant particles in water-glycerin solutions. At these low particle concentrations, the suspensions have Newtonian fluid viscosity. A variety of jet and surface velocities, solution properties, nozzle diameters, mean particle sizes, and volume fractions were studied. It was observed that for jets with very small particles, addition of solids to the jet enhances deposition and postpones splash relative to a particle-free water-glycerin solution with the same viscosity. In contrast, jets with larger particles in suspension were more prone to splash than single phase jets of the same viscosity. It is speculated that the particle diameter, relative to the lamella thickness, is the key parameter to determine whether splash is suppressed or enhanced. An existing splash model for single phase liquid jets was found to be in good agreement with the experimental results, provided that the single fitting parameter in that model is a function of the particle size, volume fraction, and surface roughness.

Initiation of the Worthington jet on the droplet impact

NASA Astrophysics Data System (ADS)

Yamamoto, Ken; Motosuke, Masahiro; Ogata, Satoshi

2018-02-01

The deformation of liquid droplets upon impact induces Worthington jets for a certain range of impact velocities. Although the growth of such a jet and its tip velocity are predicted from cases similar to droplet impact, the mechanism behind jet formation is yet to be understood. The present study uses high-speed visualization of droplet impact on a superhydrophobic surface to understand jet initiation in terms of the collapse of an air cavity. Water droplets with diameters of 2.0 and 3.0 mm are generated with the droplet Weber number varying from 2 to 20. The jet velocity is measured from the captured images, from which the maximum velocity is found to be We ˜ 7. The jet velocity at We ˜ 7 is approximately 15 times greater than the impact velocity. Moreover, surface waves are generated upon impact with the solid surface, and they induce an oscillation of the droplet cap as they propagate from the solid-liquid contact line to the top portion of the droplet. Furthermore, we find that the phase of the oscillation is related to the Weber number and greatly influences the jet velocity because it determines the initial conditions for jet generation.

Influence of elliptical structure on impinging-jet-array heat transfer performances

NASA Astrophysics Data System (ADS)

Arjocu, Simona C.; Liburdy, James A.

1997-11-01

A three-by-three square array of submerged, elliptic, impinging jets in water was used to study the heat transfer distribution in the cooling process of a constant heat flux surface. Tow jet aspect ratios were used, 2 and 3, both with the same hydraulic diameter. The array was tested at Reynolds numbers from 300 to 1500 and impinging distances of 1 to 5 hydraulic diameters. Thermochromic liquid crystals wee used to map the local heat transfer coefficient using a transient method, while the jet temperature was kept constant. The liquid crystal images were recorded through an optical fiber coupled with a CCD camera and a frame grabber and analyzed based on an RGB-temperature calibration technique. The results are reported relative to the unit cell that is used to delimitate the central jet. The heat transfer variation is shown to depend on the impingement distance and Reynolds number. The elliptic jets exhibit axis switching, jet column instability and jet swaying. All of these mechanisms affect the enhancement of the heat transfer rate and its distribution. The results are compared in terms of average and local heat transfer coefficients, for both major and minor planes for the two jet aspect ratios.

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.

PUMPS

DOEpatents

Thornton, J.D.

1959-03-24

A pump is described for conveving liquids, particure it is not advisable he apparatus. The to be submerged in the liquid to be pumped, a conduit extending from the high-velocity nozzle of the injector,and means for applying a pulsating prcesure to the surface of the liquid in the conduit, whereby the surface oscillates between positions in the conduit. During the positive half- cycle of an applied pulse liquid is forced through the high velocity nozzle or jet of the injector and operates in the manner of the well known water injector and pumps liquid from the main intake to the outlet of the injector. During the negative half-cycle of the pulse liquid flows in reverse through the jet but no reverse pumping action takes place.

Measurements of air entrainment by vertical plunging liquid jets

NASA Astrophysics Data System (ADS)

El Hammoumi, M.; Achard, J. L.; Davoust, L.

2002-06-01

This paper addresses the issue of the air-entrainment process by a vertical plunging liquid jet. A non-dimensional physical analysis, inspired by the literature on the stability of free jets submitted to an aerodynamic interaction, was developed and yielded two correlation equations for the laminar and the turbulent plunging jets. These correlation equations allow the volumetric flow rate of the air carryunder represented by the Weber number of entrainment We n to be predicted. The plunging jets under consideration issued from circular tubes long enough to achieve a fully developed flow at the outlet. A sensitive technique based on a rising soap meniscus was developed to measure directly the volumetric flow rate of the air carryunder. Our data are compared with other experimental data available in the literature; they also stand as a possible database for future theoretical modelling.

Ultra-High Resolution Observations Of Selected Blazars

NASA Astrophysics Data System (ADS)

Hodgson, Jeffrey A.

2015-01-01

Active Galactic Nuclei are the luminous centres of active galaxies that produce powerful relativistic jets from central super massive black holes (SMBH). When these jets are oriented towards the observer's line-of-sight, they become very bright, very variable and very energetic. These sources are known as blazars and Very Long Baseline Interferometry (VLBI) provides a direct means of observing into the heart of these objects. VLBI performed at 3 mm with the Global mm-VLBI Array (GMVA) and 7 mm VLBI performed with the Very Long Baseline Array (VLBA), allows some of the highest angular resolution images of blazars to be produced. In this thesis, we present the first results of an ongoing monitoring program of blazars known to emit at γ-ray energies. The physical processes that produce these jets and the γ-ray emission are still not well known. The jets are thought to be produced by converting gravitational energy around the black hole into relativistic particles that are accelerated away at near the speed of light. However, the exact mechanisms for this and the role that magnetic fields play is not fully clear. Similarly, γ-rays have been long known to have been emitted from blazars and that their production is often related to the up-scattering of synchrotron radiation from the jet. However, the origin of seed photons for the up-scattering (either from within the jet itself or from an external photon field) and the location of the γ-ray emission regions has remained inconclusive. In this thesis, we aim to describe the likely location of γ-ray emission in jets, the physical structure of blazar jets, the location of the VLBI features relative to the origin of the jet and the nature of the magnetic field, both of the VLBI scale jet and in the region where the jet is produced. We present five sources that have been monitored at 3 mm using the GMVA from 2008 until 2012. These sources have been analysed with near-in-time 7 mm maps from the Very Long Baseline Array (VLBA), γ-ray light curves from the Fermi/LAT space telescope and cm to mm-wave total-intensity light curves. In one source, OJ 287, the source has additionally been analysed with monthly imaging at 7 mm with the VLBA and near-in-time 2 cm VLBI maps. We use these resources to analyse high angular resolution structural and spectral changes and see if they correlate with flaring (both radio and γ-ray) activity and with VLBI component ejections. By spectrally decomposing sources, we can determine the spatially resolved magnetic field structure in the jets at the highest yet performed resolutions and at frequencies that are near or above the turnover frequency for synchrotron self-absorption (SSA). We compute the magnetic field estimates from SSA theory and by assuming equipartition between magnetic fields and relativistic particle energies. All sources analysed exhibit downstream quasi-stationary features which sometimes exhibit higher brightness temperatures and flux density variability than the VLBI "core", which we interpret as being recollimation or oblique shocks. We find that γ-ray flaring, mm-wave radio flaring and changes in opacity from optically thick to optically thin, is in many cases consistent with component ejections past both the VLBI "core" and these quasi-stationary downstream features. We find decreasing apparent brightness temperatures and Doppler factors as a function of increased "core" separation, which is interpreted as consistent with a slowly accelerating jet over the de-projected inner ˜10-20 pc. Assuming equipartition between magnetic energy and relativistic particle energy, the magnetic field strengths within the jets at these scales are, on average, between B ˜ 0.3 - 0.9 G, with the highest strengths found within the VLBI "core". From the observed gradient in magnetic field strengths, we can place the mmwave "core" ˜1-3 pc downstream of the base of the jet. Additionally, we estimate the the magnetic field is Bapex ˜ 3000 - 18000 G at the base of the jet. We computed theoretical estimates based on jet production under magnetically arrested disks (MAD) and find our estimates to be consistent. In the BL Lac source OJ 287, we included monthly 7 mm and near-in-time 2 cm VLBA maps to provide full kinematics and increased spectral coverage. Following a previously reported radical change in inner-jet PA of ˜100° we find unusually discrepant PAs compared with the previous jet direction, that follow very different trajectories. The source exhibits a downstream quasi-stationary feature that at times has higher brightness temperatures than the "core". The source also exhibited a large change in apparent component speeds as compared with previous epochs, which we propose could be due to changes in jet pressure causing changes in the location of downstream recollimation or oblique shocks and hence their line-of-sight viewing angle. The addition of 2 cm VLBA data allows for a comparison of magnetic fields derived from SSA and equipartition. The magnetic field estimates are consistent within 20%, with BSSA ≥ 1.6 G and Bequi ≥ 1.2 G in the "core" and BSSA ≤ 0.4 G and Bequi ≤ 0.3 G in the stationary feature. Gamma-ray emission appears to originate in the "core" and the stationary feature. The decrease in magnetic field strengths places the mmwave "core' downstream of the jet base by ≤6 pc and likely outside of the broad line region (BLR). This, combined with the results in other sources are consistent with γ-rays being produced in the vicinity of the VLBI "core" of in further downstream stationary features, which are likely over a parsec downstream of the central black hole, favouring the scenario of photons being up-scattered within the relativistic jet.

Surface tension effects on the behavior of a cavity growing, collapsing, and rebounding near a rigid wall.

PubMed

Zhang, Zhen-yu; Zhang, Hui-sheng

2004-11-01

Surface tension effects on the behavior of a pure vapor cavity or a cavity containing some noncondensible contents, which is growing, collapsing, and rebounding axisymmetrically near a rigid wall, are investigated numerically by the boundary integral method for different values of dimensionless stand-off parameter gamma, buoyancy parameter delta, and surface tension parameter beta. It is found that at the late stage of the collapse, if the resultant action of the Bjerknes force and the buoyancy force is not small, surface tension will not have significant effects on bubble behavior except that the bubble collapse time is shortened and the liquid jet becomes wider. If the resultant action of the two force is small enough, surface tension will have significant and in some cases substantial effects on bubble behavior, such as changing the direction of the liquid jet, making a new liquid jet appear, in some cases preventing the bubble from rebound before jet impact, and in other cases causing the bubble to rebound or even recollapse before jet impact. The mechanism of surface tension effects on the collapsing behavior of a cavity has been analyzed. The mechanisms of some complicated phenomena induced by surface tension effects are illustrated by analysis of the computed velocity fields and pressure contours of the liquid flow outside the bubble at different stages of the bubble evolution.

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.

The regimes of twin-fluid jet-in-crossflow at atmospheric and jet-engine operating conditions

NASA Astrophysics Data System (ADS)

Tan, Zu Puayen; Bibik, Oleksandr; Shcherbik, Dmitriy; Zinn, Ben T.; Patel, Nayan

2018-02-01

The "Twin-Fluid Jet-in-Crossflow (TF-JICF)" is a nascent variation of the classical JICF, in which a liquid jet is co-injected with an annular sleeve of gas into a gaseous crossflow. Jet-engine designers are interested in using TF-JICF for liquid-fuel injection and atomization in the next-generation combustors because it is expected to minimize combustor-damaging auto-ignition and fuel-coking tendencies. However, experimental data of TF-JICF are sparse. Furthermore, a widely accepted TF-JICF model that correlates the spray's penetration to the combined liquid-gas momentum-flux ratio (Jeff) is increasingly showing discrepancy with emerging results, suggesting a gap in the current understanding of TF-JICF. This paper describes an investigation that addressed the gap by experimentally characterizing the TF-JICF produced by a single injector across wide ranges of operating conditions (i.e., jet-A injectant, crossflow of air, crossflow Weber number = 175-1050, crossflow pressure Pcf = 1.8-9.5 atm, momentum-flux ratio J = 5-40, and air-nozzle dP = 0%-150% of Pcf). These covered the conditions previously used to develop the Jeff model, recently reported conditions that produced Jeff discrepancies, and high-pressure conditions found in jet-engines. Dye-based shadowgraph was used to acquire high-resolution (13.52 μm/pixel) images of the TF-JICF, which revealed wide-ranging characteristics such as the disrupted Rayleigh-Taylor jet instabilities, air-induced jet corrugations, spray-bifurcations, and prompt-atomization. Analyses of the data showed that contrary to the literature, the TF-JICF's penetration is not monotonically related to Jeff. A new conceptual framework for TF-JICF is proposed, where the flow configuration is composed of four regimes, each having different penetration trends, spray structures, and underlying mechanisms.

Macroscopic analysis of gas-jet wiping: Numerical simulation and experimental approach

NASA Astrophysics Data System (ADS)

Lacanette, Delphine; Gosset, Anne; Vincent, Stéphane; Buchlin, Jean-Marie; Arquis, Éric

2006-04-01

Coating techniques are frequently used in industrial processes such as paper manufacturing, wire sleeving, and in the iron and steel industry. Depending on the application considered, the thickness of the resulting substrate is controlled by mechanical (scraper), electromagnetic (if the entrained fluid is appropriated), or hydrodynamic (gas-jet wiping) operations. This paper deals with the latter process, referred to as gas-jet wiping, in which a turbulent slot jet is used to wipe the coating film dragged by a moving substrate. This mechanism relies on the gas-jet-liquid film interaction taking place on the moving surface. The aim of this study is to compare the results obtained by a lubrication one-dimensional model, numerical volume of fluid-large eddy simulation (VOF-LES) modeling and an experimental approach. The investigation emphasizes the effect of the controlling wiping parameters, i.e., the pressure gradient and shear stress distributions induced by the jet, on the shape of the liquid film. Those profiles obtained experimentally and numerically for a jet impinging on a dry fixed surface are compared. The effect of the substrate motion and the presence of the dragged liquid film on these actuators are analyzed through numerical simulations. Good agreement is found between the film thickness profile in the wiping zone obtained from the VOF-LES simulations and with the analytical model, provided that a good model for the wiping actuators is used. The effect of the gas-jet nozzle to substrate standoff distance on the final coating thickness is analyzed; the experimental and predicted values are compared for a wide set of conditions. Finally, the occurrence of the splashing phenomenon, which is characterized by the ejection of droplets from the runback film flow at jet impingement, thus limiting the wiping process, is investigated through experiments and numerical simulations.

Toward jet injection by continuous-wave laser cavitation.

PubMed

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

2017-10-01

This is a study motivated by the need to develop a needle-free device for eliminating major global healthcare problems caused by needles. The generation of liquid jets by means of a continuous-wave laser, focused into a light absorbing solution, was studied with the aim of developing a portable and affordable jet injector. We designed and fabricated glass microfluidic devices, which consist of a chamber where thermocavitation is created and a tapered channel. The growth of a vapor bubble displaces and expels the liquid through the channel as a fast traveling jet. Different parameters were varied with the purpose of increasing the jet velocity. The velocity increases with smaller channel diameters and taper ratios, whereas larger chambers significantly reduce the jet speed. It was found that the initial position of the liquid-air meniscus interface and its dynamics contribute to increased jet velocities. A maximum velocity of 94±3  m/s for a channel diameter of D=120  μm, taper ratio n=0.25, and chamber length E=200  μm was achieved. Finally, agarose gel-based skin phantoms were used to demonstrate the potential of our devices to penetrate the skin. The maximum penetration depth achieved was ∼1  mm, which is sufficient to penetrate the stratum corneum and for most medical applications. A meta-analysis shows that larger injection volumes will be required as a next step to medical relevance for laser-induced jet injection techniques in general. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

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.

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.

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.

Investigation of coaxial jet noise and inlet choking using an F-111A airplane

NASA Technical Reports Server (NTRS)

Putnam, T. W.

1973-01-01

Measurements of engine noise generated by an F-111A airplane positioned on a thrustmeasuring platform were made at angles of 0 deg to 160 deg from the aircraft heading. Sound power levels, power spectra, and directivity patterns are presented for jet exit velocities between 260 feet per second and 2400 feet per second. The test results indicate that the total acoustic power was proportional to the eighth power of the core jet velocity for core exhaust velocities greater than 300 meters per second (985 feet per second) and that little or no mixing of the core and fan streams occurred. The maximum sideline noise was most accurately predicted by using the average jet velocity for velocities above 300 meters per second (985 feet per second). The acoustic power spectrum was essentially the same for the single jet flow of afterburner operation and the coaxial flow of the nonafterburning condition. By varying the inlet geometry and cowl position, reductions in the sound pressure level of the blade passing frequency on the order of 15 decibels to 25 decibels were observed for inlet Mach numbers of 0.8 to 0.9.

The Primary Break-up Instabilities in a gas-liquid coaxial atomizer combined with electro-spray

NASA Astrophysics Data System (ADS)

Osuna, Rodrigo; Machicoane, Nathanael; Aliseda, Alberto

2017-11-01

We present an experimental study of a canonical coaxial gas-liquid atomizer, balancing the physics of gas-assisted atomization and electro-sprays. The laminar liquid stream is injected through a long straight metallic pipe at the center of the turbulent gas jet. The liquid needle is used as the anode, while the cathode is formed by a ring located on the streamwise face of the coaxial gas chamber. The gas Reynolds number ranges from 104-106, while keeping the liquid Reynolds number constant at 103. The electrospray voltage applied is varied from 100 to 5000 V and the resulting negative charge transferred to the liquid jet spans from O(10-3 - 10-1) Coulomb per cubic meter. The relative influence of the high speed gas to the liquid electric charge on the primary instability and jet break-up is studied. The effect of the electric field on the atomization process is characterized by high speed visualization at the nozzle exit, complemented with the resulting droplet size distribution in the mid field after break-up has ended. The quantitative visualization captures the fast dynamics of the interface de-stabilization and clearly shows the changes in the liquid stream instabilities caused by the electric field. These instabilities control the liquid droplet sizes and their spatio-temporal distribution in the spray, as measured from light interferometry.

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.

Flowing of supersonic underexpanded micro-jets in the range of moderate Reynolds numbers

NASA Astrophysics Data System (ADS)

Mironov, S. G.; Aniskin, V. M.; Maslov, A. A.

2017-10-01

The paper presents new experimental results on the simulation of supersonic underexpanded micro-jets by macro-jet in the range of moderate Reynolds numbers of air outflow from the nozzle. A correlation is shown between the variations in the Pitot pressure in the model micro-jet with variations in the length of the supersonic core of real the micro-jets. The results of experiments on the effect of humidity on the pulsation of mass flow rate in a micro-jet are presented.

Cause and Effect of Feedback: Multiphase Gas in Cluster Cores Heated by AGN Jets

NASA Astrophysics Data System (ADS)

Gaspari, M.; Ruszkowski, M.; Sharma, P.

2012-02-01

Multiwavelength data indicate that the X-ray-emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To a large extent, cooling is offset by heating due to active galactic nuclei (AGNs) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by collimated bipolar AGN jets. Our key conclusion is that spatially extended multiphase filaments form only when the instantaneous ratio of the thermal instability and free-fall timescales (t TI/t ff) falls below a critical threshold of ≈10. When this happens, dense cold gas decouples from the hot intracluster medium (ICM) phase and generates inhomogeneous and spatially extended Hα filaments. These cold gas clumps and filaments "rain" down onto the central regions of the core, forming a cold rotating torus and in part feeding the supermassive black hole. Consequently, the self-regulated feedback enhances AGN heating and the core returns to a higher entropy level with t TI/t ff > 10. Eventually, the core reaches quasi-stable global thermal equilibrium, and cold filaments condense out of the hot ICM whenever t TI/t ff <~ 10. This occurs despite the fact that the energy from AGN jets is supplied to the core in a highly anisotropic fashion. The effective spatial redistribution of heat is enabled in part by the turbulent motions in the wake of freely falling cold filaments. Increased AGN activity can locally reverse the cold gas flow, launching cold filamentary gas away from the cluster center. Our criterion for the condensation of spatially extended cold gas is in agreement with observations and previous idealized simulations.

Effects of Viscosity on the Performance of Air-Powered Liquid Jet Injectors

NASA Astrophysics Data System (ADS)

Portaro, Rocco; Jaber, Hadi; Ng, Hoi Dick

2017-11-01

Drug delivery without the use of hypodermic needles has been a long-term objective within the medical field. This study focuses on observing the effects of drug viscosity on injector performance for air-powered liquid jet injectors, as well as the viability of using this technology for delivering viscous-type medications such as monoclonal antibodies. The experiments are conducted through the use of a prototype injector which allows key parameters such as driver pressure, injection volume and nozzle size to be varied. Different viscosities which range from 0.9 cP to 87 cP are obtained by using a water-glycerol mix. The liquid jets emanating from the injector are assessed using high speed photography as well as a pressure transducer. Experimental findings are then compared to a CFD model which considered experimental geometry and parameters. The results of this study highlight the effect of viscosity on the operating pressure of the injector and the reduction in jet stagnation pressure. It also illustrates improved jet confinement as viscosity is increased, a finding which is in line with the numerical model, and should play a key role in improving the device's characteristics for puncturing skin.

Friction coefficient of an intact free liquid jet moving in air

NASA Astrophysics Data System (ADS)

Comiskey, P. M.; Yarin, A. L.

2018-04-01

Here, we propose a novel method of determining the friction coefficient of intact free liquid jets moving in quiescent air. The middle-size jets of this kind are relevant for such applications as decorative fountains, fiber-forming, fire suppression, agriculture, and forensics. The present method is based on measurements of trajectories created using a straightforward experimental apparatus emulating such jets at a variety of initial inclination angles. Then, the trajectories are described theoretically, accounting for the longitudinal traction imposed on such jets by the surrounding air. The comparison of the experimental data with the theoretical predictions shows that the results can be perfectly superimposed with the friction coefficient {C_{{fd}}}=5R{e_d}^{{ - 1/2 ± 0.05}}, in the 621 ≤ R{e_d} ≤ 1289 range, with Red being the Reynolds number based on the local cross-sectional diameter of the jet. The results also show that the farthest distance such jets can reach corresponds to the initial inclination angle α =35° which is in agreement with already published data.

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.

Stochastic simulation of the spray formation assisted by a high pressure

NASA Astrophysics Data System (ADS)

Gorokhovski, M.; Chtab-Desportes, A.; Voloshina, I.; Askarova, A.

2010-03-01

The stochastic model of spray formation in the vicinity of the injector and in the far-field has been described and assessed by comparison with measurements in Diesel-like conditions. In the proposed mesh-free approach, the 3D configuration of continuous liquid core is simulated stochastically by ensemble of spatial trajectories of the specifically introduced stochastic particles. The parameters of the stochastic process are presumed from the physics of primary atomization. The spray formation model consists in computation of spatial distribution of the probability of finding the non-fragmented liquid jet in the near-to-injector region. This model is combined with KIVA II computation of atomizing Diesel spray in two-ways. First, simultaneously with the gas phase RANS computation, the ensemble of stochastic particles is tracking and the probability field of their positions is calculated, which is used for sampling of initial locations of primary blobs. Second, the velocity increment of the gas due to the liquid injection is computed from the mean volume fraction of the simulated liquid core. Two novelties are proposed in the secondary atomization modeling. The first one is due to unsteadiness of the injection velocity. When the injection velocity increment in time is decreasing, the supplementary breakup may be induced. Therefore the critical Weber number is based on such increment. Second, a new stochastic model of the secondary atomization is proposed, in which the intermittent turbulent stretching is taken into account as the main mechanism. The measurements reported by Arcoumanis et al. (time-history of the mean axial centre-line velocity of droplet, and of the centre-line Sauter Mean Diameter), are compared with computations.

Method and apparatus for cutting, abrading, and drilling with sublimable particles and vaporous liquids

DOEpatents

Bingham, Dennis N.; Swainston, Richard C.; Palmer, Gary L.

1998-01-01

A gas delivery system provides a first gas which is in a liquid state under extreme pressure and in a gaseous state under intermediate pressure. A particle delivery system provides a slurry comprising the first gas in a liquid state and a second gas in a solid state. The second gas is selected so that it will solidify at a temperature at or above the temperature of the first gas in a liquid state. A nozzle assembly connected to the gas delivery system and to the particle delivery system produces a stream having a high velocity central jet comprising the slurry, a liquid sheath surrounding the central jet comprising the first gas in a liquid state and an outer jacket surrounding the liquid sheath comprising the first gas in a gas state.

Method and apparatus for cutting, abrading, and drilling with sublimable particles and vaporous liquids

DOEpatents

Bingham, D.N.; Swainston, R.C.; Palmer, G.L.

1998-03-31

A gas delivery system provides a first gas which is in a liquid state under extreme pressure and in a gaseous state under intermediate pressure. A particle delivery system provides a slurry comprising the first gas in a liquid state and a second gas in a solid state. The second gas is selected so that it will solidify at a temperature at or above the temperature of the first gas in a liquid state. A nozzle assembly connected to the gas delivery system and to the particle delivery system produces a stream having a high velocity central jet comprising the slurry, a liquid sheath surrounding the central jet comprising the first gas in a liquid state and an outer jacket surrounding the liquid sheath comprising the first gas in a gas state. 19 figs.

The complex of optical methods for study of gas-liquid jets

NASA Astrophysics Data System (ADS)

Poplavski, S. V.; Boiko, V. M.

2017-10-01

A set of optical methods for studying the dispersion and dynamics of liquids in high-speed gas jets was realized. Four optical methods were used: shadow imaging, PIV method, Laser Doppler Anemometer (LDA), a method for recording the dispersity of a spray by angular scattering of light. With the example of a supersonic coaxial jet with a central fluid supply, a technique is developed that makes it possible to obtain not only the sum of the data by four methods but new critical data on the structure of the two-phase flow, such as the concentration distributions of the spray.

An accelerating high-latitude jet in Earth's core

NASA Astrophysics Data System (ADS)

Finlay, C. C.; Livermore, P. W.; Hollerbach, R.

2016-12-01

The structure of the core-generated magnetic field, and how it changes in time (its secular variation or SV), supplies an invaluable constraint on the dynamics of the outer core. At high latitude, previous studies have noted distinctive behaviour of secular change, in particular suggesting a polar vortex tied to the dynamics within the tangent cylinder region. Recent high-resolution observational models that include data from the Swarm satellites have refined the structure of observed SV, to a rapidly changing circular daisy-chain configuration centred on the north geographic pole, on or very close to the tangent cylinder itself. Motivated by theoretical considerations of the likely dynamical regime of the core, we demonstrate that this feature can be explained by a localised westwards cylindrical jet of 420 km width centred the tangent cylinder, whose amplitude appears to have increased in strength by a factor of three over the period 2000-2016 to about 40 km/yr. The current accelerating phase may be a short fragment of decadal fluctuations of the jet strength linked to both torsional wave activity and the rotation direction of the inner core.

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.

Mixing liquid-liquid stratified flows using transverse jets in cross flows

NASA Astrophysics Data System (ADS)

Wright, Stuart; Matar, Omar K.; Markides, Christos N.

2017-11-01

Low pipeline velocities in horizontal liquid-liquid flows lead to gravitationally-induced stratification. This results in flow situations that have no point where average properties can be measured. Inline mixing limits the stratification effect by forming unstable liquid-liquid dispersions. An experimental system is used to measure the mixing performance of various jet-in-cross-flow (JICF) configurations as examples of active inline mixers. The test section consists of a 8.5-m long ETFE pipe with a 50-mm diameter, which is refractive index-matched to both a 10 cSt silicone oil and a 51 wt% glycerol solution. This practice allows advanced laser-based optical techniques, namely PLIF and PIV/PTV, to be applied to these flows in order to measure the phase fractions and velocity fields, respectively. A volume of a fluid (VOF) CFD code is then used to simulate simple jet geometries and to demonstrate the breakup and dispersion capabilities of JICFs in stratified pipeline flows by predicting their mixing efficiency. These simulation results are contrasted with the experimental results to examine the effectiveness of these simulations in predicting the dispersion and breakup. Funding from Cameron/Schlumberger, and the TMF Consortium gratefully acknowledged.

An Initial Study of the Fundamentals of Ice Crystal Icing Physics in the NASA Propulsion Systems Laboratory

NASA Technical Reports Server (NTRS)

Struk, Peter; Bartkus, Tadas; Tsao, Jen-Ching; Bencic, Timothy; King, Michael; Ratvasky, Thomas; Van Zante, Judith

2017-01-01

This presentation shows results from an initial study of the fundamental physics of ice-crystal ice accretion using the NASA Propulsion Systems Lab (PSL). Ice accretion due to the ingestion of ice-crystals is being attributed to numerous jet-engine power-loss events. The NASA PSL is an altitude jet-engine test facility which has recently added a capability to inject ice particles into the flow. NASA is evaluating whether this facility, in addition to full-engine and motor-driven-rig tests, can be used for more fundamental ice-accretion studies that simulate the different mixed-phase icing conditions along the core flow passage of a turbo-fan engine compressor. The data from such fundamental accretion tests will be used to help develop and validate models of the accretion process. The present study utilized a NACA0012 airfoil. The mixed-phase conditions were generated by partially freezing the liquid-water droplets ejected from the spray bars. This presentation shows data regarding (1) the freeze out characteristics of the cloud, (2) changes in aerothermal conditions due to the presence of the cloud, and (3) the ice accretion characteristics observed on the airfoil model. The primary variable in this test was the PSL plenum humidity which was systematically varied for two duct-exit-plane velocities (85 and 135 ms) as well as two particle size clouds (15 and 50 m MVDi). The observed clouds ranged from fully glaciated to fully liquid, where the liquid clouds were at least partially supercooled. The air total temperature decreased at the test section when the cloud was activated due to evaporation. The ice accretions observed ranged from sharp arrow-like accretions, characteristic of ice-crystal erosion, to cases with double-horn shapes, characteristic of supercooled water accretions.

An Initial Study of the Fundamentals of Ice Crystal Icing Physics in the NASA Propulsion Systems Laboratory

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Ratvasky, Thomas P.; Bencic, Timothy J.; Van Zante, Judith F.; King, Michael C.; Tsao, Jen-Ching; Bartkus, Tadas P.

2017-01-01

This paper presents results from an initial study of the fundamental physics of ice-crystal ice accretion using the NASA Propulsion Systems Lab (PSL). Ice accretion due to the ingestion of ice-crystals is being attributed to numerous jet-engine power-loss events. The NASA PSL is an altitude jet-engine test facility which has recently added a capability to inject ice particles into the flow. NASA is evaluating whether this facility, in addition to full-engine and motor-driven-rig tests, can be used for more fundamental ice-accretion studies that simulate the different mixed-phase icing conditions along the core flow passage of a turbo-fan engine compressor. The data from such fundamental accretion tests will be used to help develop and validate models of the accretion process. The present study utilized a NACA0012 airfoil. The mixed-phase conditions were generated by partially freezing the liquid-water droplets ejected from the spray bars. This paper presents data regarding (1) the freeze out characteristics of the cloud, (2) changes in aerothermal conditions due to the presence of the cloud, and (3) the ice accretion characteristics observed on the airfoil model. The primary variable in this test was the PSL plenum humidity which was systematically varied for two duct-exit-plane velocities (85 and 135 ms) as well as two particle size clouds (15 and 50 m MVDi). The observed clouds ranged from fully glaciated to fully liquid, where the liquid clouds were at least partially supercooled. The air total temperature decreased at the test section when the cloud was activated due to evaporation. The ice accretions observed ranged from sharp arrow-like accretions, characteristic of ice-crystal erosion, to cases with double-horn shapes, characteristic of supercooled water accretions.

Military utility of very large airplanes and alternative fuels

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

Mikolowsky, W.T.; Noggle, L.W.; Stanley, W.L.

1977-09-01

Synthetic chemical fuels and nuclear fuels were evaluated for use in very large airplanes (VLA's). Candidate fuels included synthetic jet fuel, liquid hydrogen, liquid methane, methanol, ethanol, ammonia, and gasoline. Airplane life-cycle costs and life-cycle energy consumption are estimated, and energy and cost effectiveness are evaluated. It is concluded that a synthetic conventional hydrocarbon jet fuel remains the most attractive for military aircraft. (PMA)

Airport cleanup rises above problems

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

Pressly, N.; Lucas, B.; Frumer, B.

Engineers used a treatment combination to improve the in-situ bioremediation system`s efficiency in removing underground fuel leaks at JFK Airport. John F. Kennedy International Airport, in New York City, on Jamaica Bay, has an above-ground storage capacity of about 32 million gallons of jet fuel, which flow through about 50 miles of high-pressure underground pipe to the central terminal area. EAch terminal`s fuel hydrant system was the major source os subsurface contamination at the site. The site is covered by 1 to 1.5 feet of reinforced concrete pavement. Liquid phase jet fuel (free product) was measured on the water tablemore » with true thickness ranging from less than 1 inch to 1 foot. After analysis of core samples, contamination was found adsorbed to the soil with maximum levels at the water table. This article describes the clean up, covering the following topics: microbial conditions during system operation; above-ground treatment challenges: free product emulsification, presence of biomass; evaluation of enhancements: dissolved air floatation, coagulation and flocculation, retention time adjustments; conclusions.« less

Investigation of the interaction dynamics of a pair of laser-induced bubbles generated at the same time through double-exposure strobe method and numerical simulations

NASA Astrophysics Data System (ADS)

Han, Bing; Liu, Liu; Ni, Xiao-Wu

2017-08-01

In order to understand the interaction dynamics of a pair of laser-induced bubbles, a double-exposure strobe photography experimental setup is build up to study the temporal evolution of the bubble pairs and to measure the transient bubble-interface moving speed. The interaction mechanisms of the bubble pairs are discussed together with the numerical results obtained through OpenFOAM. It is shown that the direction and the velocity of the jetting could be controlled by the relative size and the relative initiation distance of the bubble pair, when the bubbles are generated at the same time, i.e., in-phase. The liquid jet is considered to be a penetrating jet. The jet is originated from the smaller bubble and clearly protruding outside of the bigger bubble. The parameter space of the relative size and the initiation distance of the bubble pair allowing the formation of the penetrating jet are very narrow. It is concluded that the liquid jet induced by the bubble interactions resulted from the collapse and the rebound of the smaller bubble nearby the bigger bubble. This is defined as the "catapult effect." Such a directional liquid transportation is a promising tool as a micro-injector or a micro-pump. The investigation results could be also supplementary to the understandings of the bubble dynamics.

Three-dimensional Magnetohydrodynamical Simulations of the Morphology of Head-Tail Radio Galaxies Based on the Magnetic Tower Jet Model

NASA Astrophysics Data System (ADS)

Gan, Zhaoming; Li, Hui; Li, Shengtai; Yuan, Feng

2017-04-01

The distinctive morphology of head-tail radio galaxies reveals strong interactions between the radio jets and their intra-cluster environment, the general consensus on the morphology origin of head-tail sources is that radio jets are bent by violent intra-cluster weather. We demonstrate in this paper that such strong interactions provide a great opportunity to study the jet properties and also the dynamics of the intra-cluster medium (ICM). By three-dimensional magnetohydrodynamical simulations, we analyze the detailed bending process of a magnetically dominated jet, based on the magnetic tower jet model. We use stratified atmospheres modulated by wind/shock to mimic the violent intra-cluster weather. Core sloshing is found to be inevitable during the wind-cluster core interaction, which induces significant shear motion and could finally drive ICM turbulence around the jet, making it difficult for the jet to survive. We perform a detailed comparison between the behavior of pure hydrodynamical jets and the magnetic tower jet and find that the jet-lobe morphology could not survive against the violent disruption in all of our pure hydrodynamical jet models. On the other hand, the head-tail morphology is well reproduced by using a magnetic tower jet model bent by wind, in which hydrodynamical instabilities are naturally suppressed and the jet could always keep its integrity under the protection of its internal magnetic fields. Finally, we also check the possibility for jet bending by shock only. We find that shock could not bend the jet significantly, and thus could not be expected to explain the observed long tails in head-tail radio galaxies.

Three-dimensional Magnetohydrodynamical Simulations of the Morphology of Head–Tail Radio Galaxies Based on the Magnetic Tower Jet Model

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

Gan, Zhaoming; Yuan, Feng; Li, Hui

The distinctive morphology of head–tail radio galaxies reveals strong interactions between the radio jets and their intra-cluster environment, the general consensus on the morphology origin of head–tail sources is that radio jets are bent by violent intra-cluster weather. We demonstrate in this paper that such strong interactions provide a great opportunity to study the jet properties and also the dynamics of the intra-cluster medium (ICM). By three-dimensional magnetohydrodynamical simulations, we analyze the detailed bending process of a magnetically dominated jet, based on the magnetic tower jet model. We use stratified atmospheres modulated by wind/shock to mimic the violent intra-cluster weather.more » Core sloshing is found to be inevitable during the wind-cluster core interaction, which induces significant shear motion and could finally drive ICM turbulence around the jet, making it difficult for the jet to survive. We perform a detailed comparison between the behavior of pure hydrodynamical jets and the magnetic tower jet and find that the jet-lobe morphology could not survive against the violent disruption in all of our pure hydrodynamical jet models. On the other hand, the head–tail morphology is well reproduced by using a magnetic tower jet model bent by wind, in which hydrodynamical instabilities are naturally suppressed and the jet could always keep its integrity under the protection of its internal magnetic fields. Finally, we also check the possibility for jet bending by shock only. We find that shock could not bend the jet significantly, and thus could not be expected to explain the observed long tails in head–tail radio galaxies.« less

On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation

NASA Astrophysics Data System (ADS)

Archer, Matthew R.; Roughan, Moninya; Keating, Shane R.; Schaeffer, Amandine

2017-11-01

Given the importance of western boundary currents over a wide range of scales in the ocean, it is crucial that we understand their dynamics to accurately predict future changes. For this, we need detailed knowledge of their structure and variability. Here we investigate the jet structure of the East Australian Current (EAC), using observations from HF radars and moorings deployed at 30°S-31°S. Meandering, core velocity, width, and eddy kinetic energy (EKE) are quantified from 4 years of hourly 1.5 km resolution surface current maps (2012-2016), to obtain the most detailed representation of the surface EAC jet to date. The EAC flows predominantly over the ˜1,500 m isobath 50 km offshore but makes large amplitude displacements eastward every 65-100 days—the time scale associated with mesoscale eddy shedding at the EAC separation. Smaller-amplitude, higher-frequency meanders occur every 20-45 days. Using a coordinate frame that follows the jet, we show core velocity and EKE exhibit seasonality in both magnitude and variance, being maximum in summer (1.55 m s-1 mean core velocity), minimum in winter (0.8 m s-1). However, it is the eddy-shedding time scale that dominates jet variability. As the EAC moves shoreward, shelf temperature and along-stream velocity vary linearly with jet movement, within ˜35 km of the core. The EAC is within this range 75% of the time, demonstrating its importance to the shelf circulation. Temperature and velocity fluctuations at the 70 m (100 m) isobath are more influenced by wind (EAC encroachment), with the strongest response occurring when wind and EAC act constructively.

Drop size distribution and air velocity measurements in air assist swirl atomizer sprays

NASA Technical Reports Server (NTRS)

Mao, C.-P.; Oechsle, V.; Chigier, N.

1987-01-01

Detailed measurements of mean drop size (SMD) and size distribution parameters have been made using a Fraunhofer diffraction particle sizing instrument in a series of sprays generated by an air assist swirl atomizer. Thirty-six different combinations of fuel and air mass flow rates were examined with liquid flow rates up to 14 lbm/hr and atomizing air flow rates up to 10 lbm/hr. Linear relationships were found between SMD and liquid to air mass flow rate ratios. SMD increased with distance downstream along the center line and also with radial distance from the axis. Increase in obscuration with distance downstream was due to an increase in number density of particles as the result of deceleration of drops and an increase in the exposed path length of the laser beam. Velocity components of the atomizing air flow field measured by a laser anemometer show swirling jet air flow fields with solid body rotation in the core and free vortex flow in the outer regions.

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.

Injector for liquid fueled rocket engine

NASA Technical Reports Server (NTRS)

Cornelius, Charles S. (Inventor); Myers, W. Neill (Inventor); Shadoan, Michael David (Inventor); Sparks, David L. (Inventor)

2000-01-01

An injector for liquid fueled rocket engines wherein a generally flat core having a frustoconical dome attached to one side of the core to serve as a manifold for a first liquid, with the core having a generally circular configuration having an axis. The other side of the core has a plurality of concentric annular first slots and a plurality of annular concentric second slots alternating with the first slots, the second slots having a greater depth than said first slots. A bore extends through the core for inletting a second liquid into said core, the bore intersecting the second slots to feed the second liquid into the second slots. The core also has a plurality of first passageways leading from the manifold to the first annular slots for feeding the first liquid into said first slots. A faceplate brazed to said other side of the core is provided with apertures extending from the first and second slots through said face plate, these apertures being positioned to direct fuel and liquid oxygen into contact with each other in the combustion chamber. The first liquid may be liquid oxygen and the second liquid may be kerosene or liquid hydrogen.

CYCLAM - Recycling by a Laser-driven Drop Jet from Waste that Feeds AM

NASA Astrophysics Data System (ADS)

Kaplan, Alexander F. H.; Samarjy, Ramiz S. M.

Additive manufacturing of metal parts is supplied by powder or wire. Manufacturing of this raw material causes additional costs and environmental impact. A new technique is proposed where the feeding directly originates from a metal sheet, which can even be waste. When cutting is done by laser-induced boiling, melt is continuously ejected downwards underneath the sheet. The ejected melt is deposited as a track on a substrate, enabling additive manufacturing by substrate movement along a desired path. The melt first flows downwards as a column and after a few millimeters separates into drops, here about 500 micrometer in diameter, as observed by high speed imaging. The drops incorporate sequentially and calmly into a long melt pool on the substrate. While steel drops formed regular tracks on steel and aluminium substrates, on copper substrate periodic drops solidified instead. For this new technique, called CYCLAM, the laser beam acts indirectly while the drop jet becomes the main tool. From imaging, properties like the width or fluctuations of the drop jet can be statistically evaluated. Despite oscillation of the liquid column, the divergence of the drop jet remained small, improving the precision and robustness. The melt leaves the cut sheet as a liquid column, 1 to 4 mm in length, which periodically separates drops that are transferred as a liquid jet to the substrate. For very short distance of 2 to 3 mm between the two sheets this liquid column can transfer the melt continuously as a liquid bridge. This phenomenon was observed, as a variant of the technique, but the duration of the bridge was limited by fluid mechanic instabilities.

Soot and liquid-phase fuel distributions in a newly designed optically accessible DI diesel engine

NASA Astrophysics Data System (ADS)

Dec, J. E.; Espey, C.

1993-10-01

Two-dimensional (2-D) laser-sheet imaging has been used to examine the soot and liquid-phase fuel distributions in a newly designed, optically accessible, direct-injection diesel engine of the heavy-duty size class. The design of this engine preserves the intake port geometry and basic dimensions of a Cummins N-series production engine. It also includes several unique features to provide considerable optical access. Liquid-phase fuel and soot distribution studies were conducted at a medium speed (1,200 rpm) using a Cummins closed-nozzle fuel injector. The scattering was used to obtain planar images of the liquid-phase fuel distribution. These images show that the leading edge of the liquid-phase portion of the fuel jet reaches a maximum length of 24 mm, which is about half the combustion bowl radius for this engine. Beyond this point virtually all the fuel has vaporized. Soot distribution measurements were made at a high load condition using three imaging diagnostics: natural flame luminosity, 2-D laser-induced incandescence, and 2-D elastic scattering. This investigation showed that the soot distribution in the combusting fuel jet develops through three stages. First, just after the onset of luminous combustion, soot particles are small and nearly uniformly distributed throughout the luminous region of the fuel jet. Second, after about 2 crank angle degrees a pattern develops of a higher soot concentration of larger sized particles in the head vortex region of the jet and a lower soot concentration of smaller sized particles upstream toward the injector. Third, after fuel injection ends, both the soot concentration and soot particle size increase rapidly in the upstream portion of the fuel jet.

Multi-scale approach to the modeling of fission gas discharge during hypothetical loss-of-flow accident in gen-IV sodium fast reactor

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

Behafarid, F.; Shaver, D. R.; Bolotnov, I. A.

The required technological and safety standards for future Gen IV Reactors can only be achieved if advanced simulation capabilities become available, which combine high performance computing with the necessary level of modeling detail and high accuracy of predictions. The purpose of this paper is to present new results of multi-scale three-dimensional (3D) simulations of the inter-related phenomena, which occur as a result of fuel element heat-up and cladding failure, including the injection of a jet of gaseous fission products into a partially blocked Sodium Fast Reactor (SFR) coolant channel, and gas/molten sodium transport along the coolant channels. The computational approachmore » to the analysis of the overall accident scenario is based on using two different inter-communicating computational multiphase fluid dynamics (CMFD) codes: a CFD code, PHASTA, and a RANS code, NPHASE-CMFD. Using the geometry and time history of cladding failure and the gas injection rate, direct numerical simulations (DNS), combined with the Level Set method, of two-phase turbulent flow have been performed by the PHASTA code. The model allows one to track the evolution of gas/liquid interfaces at a centimeter scale. The simulated phenomena include the formation and breakup of the jet of fission products injected into the liquid sodium coolant. The PHASTA outflow has been averaged over time to obtain mean phasic velocities and volumetric concentrations, as well as the liquid turbulent kinetic energy and turbulence dissipation rate, all of which have served as the input to the core-scale simulations using the NPHASE-CMFD code. A sliding window time averaging has been used to capture mean flow parameters for transient cases. The results presented in the paper include testing and validation of the proposed models, as well the predictions of fission-gas/liquid-sodium transport along a multi-rod fuel assembly of SFR during a partial loss-of-flow accident. (authors)« less

Investigation of the impact of high liquid viscosity on jet atomization in crossflow via high-fidelity simulations

NASA Astrophysics Data System (ADS)

Li, Xiaoyi; Gao, Hui; Soteriou, Marios C.

2017-08-01

Atomization of extremely high viscosity liquid can be of interest for many applications in aerospace, automotive, pharmaceutical, and food industries. While detailed atomization measurements usually face grand challenges, high-fidelity numerical simulations offer the advantage to comprehensively explore the atomization details. In this work, a previously validated high-fidelity first-principle simulation code HiMIST is utilized to simulate high-viscosity liquid jet atomization in crossflow. The code is used to perform a parametric study of the atomization process in a wide range of Ohnesorge numbers (Oh = 0.004-2) and Weber numbers (We = 10-160). Direct comparisons between the present study and previously published low-viscosity jet in crossflow results are performed. The effects of viscous damping and slowing on jet penetration, liquid surface instabilities, ligament formation/breakup, and subsequent droplet formation are investigated. Complex variations in near-field and far-field jet penetrations with increasing Oh at different We are observed and linked with the underlying jet deformation and breakup physics. Transition in breakup regimes and increase in droplet size with increasing Oh are observed, mostly consistent with the literature reports. The detailed simulations elucidate a distinctive edge-ligament-breakup dominated process with long surviving ligaments for the higher Oh cases, as opposed to a two-stage edge-stripping/column-fracture process for the lower Oh counterparts. The trend of decreasing column deflection with increasing We is reversed as Oh increases. A predominantly unimodal droplet size distribution is predicted at higher Oh, in contrast to the bimodal distribution at lower Oh. It has been found that both Rayleigh-Taylor and Kelvin-Helmholtz linear stability theories cannot be easily applied to interpret the distinct edge breakup process and further study of the underlying physics is needed.

Observed trends in the global jet stream characteristics during the second half of the 20th century

NASA Astrophysics Data System (ADS)

Pena-Ortiz, Cristina; Gallego, David; Ribera, Pedro; Ordonez, Paulina; Alvarez-Castro, Maria Del Carmen

2013-04-01

In this paper, we propose a new method based on the detection of jet cores with the aim to describe the climatological features of the jet streams and to estimate their trends in latitude, altitude, and velocity in the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and 20th Century reanalysis data sets. Due to the fact that the detection method uses a single grid point to define the position of jet cores, our results reveal a greater latitudinal definition allowing a more accurate picture of the split flow configurations and double jet structures. To the best of our knowledge, these results provide the first multiseasonal and global trend analysis of jet streams based on a daily-resolution 3-D detection algorithm. Trends have been analyzed over 1958-2008 and during the post-satellite period, 1979-2008. We found that, in general, trends in jet velocities and latitudes have been faster for the Southern Hemisphere jets and especially for the southern polar front jet which has experienced the fastest velocity increase and poleward shift over 1979-2008 during the austral summer and autumn. Results presented here show an acceleration and a poleward shift of the northern and southern winter subtropical jets over 1979-2008 that occur at a faster rate and over larger zonally extended regions during this latter period than during 1958-2008.

Gas density effect on dropsize of simulated fuel sprays

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1989-01-01

Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, We*Re, and gas-to-liquid density ratio, rho sub g/rho sub l. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.

Maia Mapper: high definition XRF imaging in the lab

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

Ryan, Chris G.; Kirkham, R.; Moorhead, G. F.

Here, Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm 2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keVmore » into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.« less

Maia Mapper: high definition XRF imaging in the lab

DOE PAGES

Ryan, Chris G.; Kirkham, R.; Moorhead, G. F.; ...

2018-03-13

Here, Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm 2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keVmore » into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.« less

Maia Mapper: high definition XRF imaging in the lab

NASA Astrophysics Data System (ADS)

Ryan, C. G.; Kirkham, R.; Moorhead, G. F.; Parry, D.; Jensen, M.; Faulks, A.; Hogan, S.; Dunn, P. A.; Dodanwela, R.; Fisher, L. A.; Pearce, M.; Siddons, D. P.; Kuczewski, A.; Lundström, U.; Trolliet, A.; Gao, N.

2018-03-01

Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keV into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.

The Surface Velocity Structure of the Florida Current in a Jet Coordinate Frame

NASA Astrophysics Data System (ADS)

Archer, Matthew R.; Shay, Lynn K.; Johns, William E.

2017-11-01

The structure and variability of the Florida Current between 25° and 26°N are investigated using HF radar ocean current measurements to provide the most detailed view of the surface jet to date. A 2-D jet coordinate analysis is performed to define lateral displacements of the jet in time (meandering), and associated structural variations over a 2 year period (2005-2006). In the jet coordinate frame, core speed has a median value of ˜160 cm s-1 at the central latitude of the array (25.4°N), with a standard deviation (STD) of 35 cm s-1. The jet meanders at timescales of 3-30 days, with a STD of 8 km, and a downstream phase speed of ˜80 km d-1. Meandering accounts for ˜45% of eddy kinetic energy computed in a fixed (geographical) reference frame. Core speed, width, and shear undergo the same dominant 3-30 day variability, plus an annual cycle that matches seasonality of alongshore wind stress. Jet transport at 25.4°N exhibits a different seasonality to volume transport at 27°N, most likely driven by input from the Northwest Providence Channel. Core speed correlates inversely with Miami sea level fluctuations such that a 40 cm s-1 deceleration is associated with a ˜10 cm elevation in sea level, although there is no correlation of sea level to jet meandering or width. Such accurate quantification of the Florida Current's variability is critical to understand and forecast future changes in the climate system of the North Atlantic, as well as local impacts on coastal circulation and sea level variability along south Florida's coastline.

Study on High Speed Lithium Jet For Neutron Source of Boron Neutron Capture Therapy (BNCT)

NASA Astrophysics Data System (ADS)

Takahashi, Minoru; Kobayashi, Tooru; Zhang, Mingguang; Mák, Michael; Štefanica, Jirí; Dostál, Václav; Zhao, Wei

The feasibility study of a liquid lithium type proton beam target was performed for the neutron source of the boron neutron capture therapy (BNCT). As the candidates of the liquid lithium target, a thin sheet jet and a thin film flow on a concave wall were chosen, and a lithium flow experiment was conducted to investigate the hydrodynamic stability of the targets. The surfaces of the jets and film flows with a thickness of 0.5 mm and a width of 50 mm were observed by means of photography. It has been found that a stable sheet jet and a stable film flow on a concave wall can be formed up to certain velocities by using a straight nozzle and a curved nozzle with the concave wall, respectively.

Unsteady jet in designing innovative drug delivery system

NASA Astrophysics Data System (ADS)

Wang, Cong; Mazur, Paul; Cosse, Julia; Rider, Stephanie; Gharib, Morteza

2014-11-01

Micro-needle injections, a promising pain-free drug delivery method, is constrained by its limited penetration depth. This deficiency can be overcome by implementing fast unsteady jet that can penetrate sub-dermally. The development of a faster liquid jet would increase the penetration depth and delivery volume of micro-needles. In this preliminary work, the nonlinear transient behavior of an elastic tube balloon in providing fast discharge is analyzed. A physical model that combines the Mooney Rivlin Material model and Young-Lapalce's Law was developed and used to investigate the fast discharging dynamic phenomenon. A proof of concept prototype was constructed to demonstrate the feasibility of a simple thumb-sized delivery system to generate liquid jet with desired speed in the range of 5-10 m/s. This work is supported by ZCUBE Corporation.

Singlet oxygen generator for a supersonic chemical oxygen iodine laser: parametric study and recovery of chemicals

NASA Astrophysics Data System (ADS)

Spalek, Otomar; Kodymova, Jarmila

1997-04-01

A jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was studied including singlet delta oxygen, O2(1(Delta) g), and residual chlorine concentration measurements. The investigation was intended mainly for a water vapor measurement in gas effluent of generator in dependence on properties of liquid jets: a chemical composition and temperature of the input liquid (alkaline solution of hydrogen peroxide), a liquid jets diameter and their geometrical arrangement. Effects of these parameters on output power of a small-scale supersonic laser were studied as well. Possible approaches to a chemical fuels management in a chemical oxygen-iodine laser for industrial applications are considered. An 'open loop' cycle with a possible use of sodium hydroxide, and a 'closed loop' cycle with a regeneration of both potassium hydroxide and hydrogen peroxide are discussed.

Progress on coal-derived fuels for aviation systems

NASA Technical Reports Server (NTRS)

Witcofski, R. D.

1978-01-01

Synthetic aviation kerosene (Syn. Jet-A), liquid methane (LCH4), and liquid hydrogen (LH2) appear to be the most promising coal-derived fuels. Liquid hydrogen aircraft configurations, their fuel systems, and their ground requirements at the airport are identified. These aircraft appear viable, particularly for long haul use, where aircraft fueled with coal derived LH2 would consume 9 percent less coal resources than would aircraft fueled with coal derived Syn. Jet-A. Distribution of hydrogen from the point of manufacture to airports may pose problems. Synthetic JET-A would appear to cause fewer concerns to the air transportation industry. Of the three candidate fuels, LCH4 is the most energy efficient to produce, and an aircraft fueled with coal derived LCH4 may provide both the most efficient utilization of coal resources and the least expensive ticket as well.

Velocity field of a round jet in a cross flow for various jet injection angles and velocity ratios. [Langley V/STOL tunnel

NASA Technical Reports Server (NTRS)

Fearn, R. L.; Weston, R. P.

1979-01-01

A subsonic round jet injected from a flat plate into a subsonic crosswind of the same temperature was investigated. Velocity and pressure measurements in planes perpendicular to the path of the jet were made for nominal jet injection angles of 45 deg, 60 deg, 75 deg, 90 deg, and 105 deg and for jet/cross flow velocity ratios of four and eight. The velocity measurements were obtained to infer the properties of the vortex pair associated with a jet in a cross flow. Jet centerline and vortex trajectories were determined and fit with an empirical equation that includes the effects of jet injection angle, jet core length, and jet/cross flow velocity ratios.

Drop Impact Dynamics with Sessile Drops and Geometries: Spreading, Jetting, and Fragmentation

NASA Astrophysics Data System (ADS)

Tilger, Christopher F.

The tendency of surface tension to cause small parcels of fluid to form into drops allows convenient packaging, transport, dispersal of liquid phase matter. Liquid drop impacts with solids, liquids, and other drops have realized and additional future applications in biological, manufacturing, heat transfer, and combustion systems. Experiments were conducted to investigate the dynamics of multiple drop collisions, rather than the most-studied phenomenon of single drop impacts. Additional drop impacts were performed on rigid hemispheres representing sessile drops, angled substrates, and into the vertex of two tilted surfaces arranged into a vee shape. A qualitative inspection of drop-sessile drop impacts shows distinct post-impact shapes depending on the offset distance between the drops. At intermediate offset distances, distinct jets issue from the overlap region between the two drops projected areas. These jets are observed to reach their maximum extent at a critical offset distance ratio, epsilon epsilon ˜ 0.75-0.80, with substrate contact angle and W e having a lesser effect. Capillary waves that traverse the sessile drop after collision cause a lower aspect ratio liquid column to emanate from the sessile drop opposite the impact. In order to better understand the jetting phenomenon seen in the offset drop-sessile drop impacts, simpler solid geometries are investigated that elicit a similar behavior. Solid hemispheres do not show the singular jetting observed in the fluidic case, however, a simple vee formed by two intersection planar substrates do jet in a similar fashion to the fluidic case. A geometric model with partnered experiments is developed to describe the bisymmetric spread of an impacting drop on an angled substrate. This geometric model is used to guide a time of arrival based model for various features of the drop impact, which is used to predict jetting in various vee channel experiments.

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.

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.

Subcritical and supercritical fuel injection and mixing in single and binary species systems

NASA Astrophysics Data System (ADS)

Roy, Arnab

Subcritical and supercritical fluid injection using a single round injector into a quiescent atmosphere comprising single and binary species was investigated using optical diagnostics. Different disintegration and mixing modes are expected for the two cases. In the binary species case, the atmosphere comprised an inert gas of a different composition than that of the injected fluid. In single species case, the atmosphere consisted of the same species as that of the injected fluid. Density values were quantified and density gradient profiles were inferred from the experimental data. A novel method was applied for the detection of detailed structures throughout the entire jet center plane. Various combinations of injectant and chamber conditions were tested and a wide range of density ratios were covered. The subcritical cases demonstrated the importance of surface tension and inertial forces, while the supercritical cases showed no signs of surface tension and, in most situations, resembled the mixing characteristics of a gaseous jet injected into a gaseous environment. A comparison between the single and binary species systems has also been provided. A detailed laser calibration procedure was undertaken to account for the laser absorption through the gas and liquid phases and for fluorescence in the non-linear excitation regime for high laser pulse energy. Core lengths were measured for binary species cases and correlated with visualization results. An eigenvalue approach was taken to determine the location of maximum gradients for determining the core length. Jet divergence angles were also calculated and were found to increase with chamber-to-injectant density ratio for both systems. A model was proposed for the spreading angle dependence on density ratio for both single and binary species systems and was compared to existing theoretical studies and experimental work. Finally, a linear stability analysis was performed for the jet injected into both subcritical and supercritical atmospheres. The subcritical cases showed good correlation with previous and current experimental results. The supercritical solutions, which have not yet been solved earlier by researchers, are found here through an asymptotic solution of the dispersion equation for exceedingly high Weber numbers.

Uncovering Nature’s 100 TeV Particle Accelerators in the Large-Scale Jets of Quasars

NASA Astrophysics Data System (ADS)

Georganopoulos, Markos; Meyer, Eileen; Sparks, William B.; Perlman, Eric S.; Van Der Marel, Roeland P.; Anderson, Jay; Sohn, S. Tony; Biretta, John A.; Norman, Colin Arthur; Chiaberge, Marco

2016-04-01

Since the first jet X-ray detections sixteen years ago the adopted paradigm for the X-ray emission has been the IC/CMB model that requires highly relativistic (Lorentz factors of 10-20), extremely powerful (sometimes super-Eddington) kpc scale jets. R I will discuss recently obtained strong evidence, from two different avenues, IR to optical polarimetry for PKS 1136-135 and gamma-ray observations for 3C 273 and PKS 0637-752, ruling out the EC/CMB model. Our work constrains the jet Lorentz factors to less than ~few, and leaves as the only reasonable alternative synchrotron emission from ~100 TeV jet electrons, accelerated hundreds of kpc away from the central engine. This refutes over a decade of work on the jet X-ray emission mechanism and overall energetics and, if confirmed in more sources, it will constitute a paradigm shift in our understanding of powerful large scale jets and their role in the universe. Two important findings emerging from our work will also discussed be: (i) the solid angle-integrated luminosity of the large scale jet is comparable to that of the jet core, contrary to the current belief that the core is the dominant jet radiative outlet and (ii) the large scale jets are the main source of TeV photon in the universe, something potentially important, as TeV photons have been suggested to heat up the intergalactic medium and reduce the number of dwarf galaxies formed.

Jet outflow and gamma-ray emission correlations in S5 0716+714

DOE PAGES

Rani, B.; Krichbaum, T. P.; Marscher, A. P.; ...

2014-11-06

Here, using millimeter very long baseline interferometry (VLBI) observations of the BL Lac object S5 0716+714 from August 2008 to September 2013, we investigate variations in the core flux density and orientation of the sub-parsec scale jet, i.e. position angle. The γ-ray data obtained by the Fermi Large Area Telescope are used to investigate the high-energy flux variations over the same time period. For the first time in any blazar, we report a significant correlation between the γ-ray flux variations and the position angle variations in the VLBI jet. The cross-correlation analysis also indicates a positive correlation such that themore » mm-VLBI core flux density variations are delayed with respect to the γ-ray flux by 82±32 days. This suggests that the high-energy emission is coming from a region located ≥(3.8±1.9) parsecs upstream of the mm-VLBI core (closer to the central black hole). Lastly, these results imply that the observed inner jet morphology has a strong connection with the observed γ-ray flares.« less

Separating Turbofan Engine Noise Sources Using Auto and Cross Spectra from Four Microphones

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

2008-01-01

The study of core noise from turbofan engines has become more important as noise from other sources such as the fan and jet were reduced. A multiple-microphone and acoustic-source modeling method to separate correlated and uncorrelated sources is discussed. The auto- and cross spectra in the frequency range below 1000 Hz are fitted with a noise propagation model based on a source couplet consisting of a single incoherent monopole source with a single coherent monopole source or a source triplet consisting of a single incoherent monopole source with two coherent monopole point sources. Examples are presented using data from a Pratt& Whitney PW4098 turbofan engine. The method separates the low-frequency jet noise from the core noise at the nozzle exit. It is shown that at low power settings, the core noise is a major contributor to the noise. Even at higher power settings, it can be more important than jet noise. However, at low frequencies, uncorrelated broadband noise and jet noise become the important factors as the engine power setting is increased.

Jet outflow and gamma-ray emission correlations in S5 0716+714

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

Rani, B.; Krichbaum, T. P.; Marscher, A. P.

Here, using millimeter very long baseline interferometry (VLBI) observations of the BL Lac object S5 0716+714 from August 2008 to September 2013, we investigate variations in the core flux density and orientation of the sub-parsec scale jet, i.e. position angle. The γ-ray data obtained by the Fermi Large Area Telescope are used to investigate the high-energy flux variations over the same time period. For the first time in any blazar, we report a significant correlation between the γ-ray flux variations and the position angle variations in the VLBI jet. The cross-correlation analysis also indicates a positive correlation such that themore » mm-VLBI core flux density variations are delayed with respect to the γ-ray flux by 82±32 days. This suggests that the high-energy emission is coming from a region located ≥(3.8±1.9) parsecs upstream of the mm-VLBI core (closer to the central black hole). Lastly, these results imply that the observed inner jet morphology has a strong connection with the observed γ-ray flares.« less

Shock wave absorber having apertured plate

DOEpatents

Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

1983-08-26

The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

Shock wave absorber having apertured plate

DOEpatents

Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

1985-01-01

The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

Models of a partially hydrated Titan interior with a clathrate crust

NASA Astrophysics Data System (ADS)

Lunine, J. I.; Castillo-Rogez, J. C.; Choukroun, M.; Sotin, C.

2012-04-01

We present a model of the interior evolution of Titan over time, assuming the silicate core was hydrated early in Titan’s history and is dehydrating over time. The original model presented in Castillo-Rogez and Lunine (2010) was motivated by a Cassini-derived moment of inertia (Iess et al., 2010) for Titan too large to be accommodated by classical fully differentiated models in which an anhydrous silicate core was overlain by a water ice (with possible perched ocean) mantle. Our model consists of a silicate core still in the process of dehydrating today, a situation made possible by the leaching of radiogenic potassium from the silicates into the perched liquid water ocean. The most recent version of our model accounts for the likely presence of large amounts of methane in the upper crust invoked to explain methane’s persistence at present and through geologic time (Tobie et al. 2006). The methane-rich crust turns out to have essentially no bearing on the temperature of the silicate core and hence the timing of dehydration, but it profoundly affects the thickness of the high-pressure ice layer beneath the ocean. Indeed, the insulating effect of the methane clathrate crust could have delayed the formation of the high-pressure layer, resulting in the interaction of liquid water with the silicate core for extended periods of time. Although a high-pressure ice layer is likely in place today, it is thin enough that plumes of hot water from the dehydrating core probably breach that layer. The implications of such a deep hydrothermal system for the later stages of the evolution of Titan’s interior and surface will be discussed. Part of this work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged. References: Castillo-Rogez, J., Lunine, J.: “Evolution of Titan’s rocky core constrained by Cassini observations”. GRL, Vol. 37, L20205, 2010. Iess, L., et al.: “Gravity field, shape, and moment of inertia of Titan”. Science, Vol. 327, 1367-1369. Tobie, G., et al.: “Episodic outgassing as the origin of atmospheric methane on Titan”. Nature 440: 61-64, 2006.

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.

Rapid microfluidic mixing and liquid jets for studying biomolecular chemical dynamics

NASA Astrophysics Data System (ADS)

Langley, Daniel; Abbey, Brian

2018-01-01

X-ray Free-Electron Lasers (XFELs) offer a unique opportunity to study the structural dynamics of proteins on a femtosecond time-scale. To realize the full potential of XFEL sources for studying time-resolved biomolecular processes however, requires the optimization and development of devices that can both act as a trigger and a delivery mechanism for the system of interest. Here we present numerical simulations and actual devices exploring the conditions required for the development of successful mixing and injection devices for tracking the molecular dynamics of proteins in solution on micro to nanosecond timescales using XFELs. The mechanism for combining reagents employs a threefold combination of pico-liter volumes, lamination and serpentine mixing. Focusing and delivering the sample in solution is achieved using the Gas Dynamic Virtual Nozzle (GDVN), which was specifically developed to produce a micrometer diameter, in-vacuum liquid jet. We explore the influence of parameters such as flow rate and gas pressure on the mixing time and jet stability, and explore the formation of rapid homogeneously mixed jets for `mix-and-inject' liquid scattering experiments at Synchrotron and XFEL facilities.

Core Formation Process and Light Elements in the Planetary Core

NASA Astrophysics Data System (ADS)

Ohtani, E.; Sakairi, T.; Watanabe, K.; Kamada, S.; Sakamaki, T.; Hirao, N.

2015-12-01

Si, O, and S are major candidates for light elements in the planetary core. In the early stage of the planetary formation, the core formation started by percolation of the metallic liquid though silicate matrix because Fe-S-O and Fe-S-Si eutectic temperatures are significantly lower than the solidus of the silicates. Therefore, in the early stage of accretion of the planets, the eutectic liquid with S enrichment was formed and separated into the core by percolation. The major light element in the core at this stage will be sulfur. The internal pressure and temperature increased with the growth of the planets, and the metal component depleted in S was molten. The metallic melt contained both Si and O at high pressure in the deep magma ocean in the later stage. Thus, the core contains S, Si, and O in this stage of core formation. Partitioning experiments between solid and liquid metals indicate that S is partitioned into the liquid metal, whereas O is weakly into the liquid. Partitioning of Si changes with the metallic iron phases, i.e., fcc iron-alloy coexisting with the metallic liquid below 30 GPa is depleted in Si. Whereas hcp-Fe alloy above 30 GPa coexisting with the liquid favors Si. This contrast of Si partitioning provides remarkable difference in compositions of the solid inner core and liquid outer core among different terrestrial planets. Our melting experiments of the Fe-S-Si and Fe-O-S systems at high pressure indicate the core-adiabats in small planets, Mercury and Mars, are greater than the slope of the solidus and liquidus curves of these systems. Thus, in these planets, the core crystallized at the top of the liquid core and 'snowing core' formation occurred during crystallization. The solid inner core is depleted in both Si and S whereas the liquid outer core is relatively enriched in Si and S in these planets. On the other hand, the core adiabats in large planets, Earth and Venus, are smaller than the solidus and liquidus curves of the systems. The inner core of these planets crystallized at the center of the core and it has the relatively Si rich inner core and the S enriched outer core. Based on melting and solid-liquid partitioning, the equation of state, and sound velocity of iron-light element alloys, we examined the plausible distribution of light elements in the liquid outer and solid inner cores of the terrestrial planets.

Numerical investigation on the expansion of supercritical carbon dioxide jet

NASA Astrophysics Data System (ADS)

Lv, Q.; Long, X. P.; Kang, Y.; Xiao, L. Z.; Wu, W.

2013-12-01

Supercritical carbon dioxide (SC-CO2) fluid is characterized by low rock breaking threshold pressure and high rock breaking rate. Meanwhile, SC-CO2 fluid has relatively low viscosity near to gas and high density near to liquid. So, it has great advantages in drilling and rock breaking over water. In this paper, numerical study of SC-CO2 flowing through a nozzle is presented. The purpose of this simulation is to ascertain why the SC-CO2 jet flow has better ability in drilling and rock breaking than the water jet flow. The simulation model was controlled by the RANS equations together with the continuity equation as well as the energy equation. The realizable k-epsilon turbulence model was adopted to govern the turbulent characteristics. Pressure boundary conditions were applied to the inlet and outlet boundary. The properties of carbon dioxide and water were described by UDF. It is found that: (1) under the same boundary conditions, the decay of dimensionless central axial velocity and dynamic pressure of water is quicker than that of the SC-CO2, and the core length of SC-CO2 jet is about 4.5 times of the nozzle diameter, which is 1 times longer than that of the water; (2) With the increase of inlet pressure or the decrease of outlet pressure, the dimensionless central axial velocity and dynamic pressure attenuation of water keeps the same, while the decay of central axial velocity of SC-CO2 turns gentle; (3) the change of central axial temperature of SC-CO2 is more complex than that of the water.

The relation of turbulence to diffusion in open-channel flows

USGS Publications Warehouse

Keefer, Thomas N.

1971-01-01

The exponent in the power-law equation describing the decay of scalar quantities downstream of a jet is a linear function of the shear velocity of the channel. The length of the core region of a jet is a power-law function of the jet strength with the exponent depending on boundary roughness.

Magnetosheath jets: MMS observations of internal structures and jet interactions with ambient plasma

NASA Astrophysics Data System (ADS)

Plaschke, F.; Karlsson, T.; Hietala, H.; Archer, M. O.; Voros, Z.; Nakamura, R.; Magnes, W.; Baumjohann, W.; Torbert, R. B.; Russell, C. T.; Giles, B. L.

2017-12-01

The dayside magnetosheath downstream of the quasi-parallel bow shock is commonly permeated by high-speed jets. Under low IMF cone angle conditions, large scale jets alone (with cross-sectional diameters of over 2 Earth radii) have been found to impact the subsolar magnetopause once every 6 minutes - smaller scale jets occurring much more frequently. The consequences of jet impacts on the magnetopause can be significant: they may trigger local reconnection and waves, alter radiation belt electron drift paths, disturb the geomagnetic field, and potentially generate diffuse throat aurora at the dayside ionosphere. Although some basic statistical properties of jets are well-established, their internal structure and interactions with the surrounding magnetosheath plasma are rather unknown. We present Magnetospheric Multiscale (MMS) observations which reveal a rich jet-internal structure of high-amplitude plasma moment and magnetic field variations and associated currents. These variations/structures are generally found to be in thermal and magnetic pressure balance; they mostly (but not always) convect with the plasma flow. Small velocity differences between plasma and structures are revealed via four-spacecraft timing analysis. Inside a jet core region, where the plasma velocity maximizes, structures are found to propagate forward (i.e., with the jet), whereas backward propagation is found outside that core region. Although super-magnetosonic flows are detected by MMS in the spacecraft frame of reference, no fast shock is seen as the jet plasma is sub-magnetosonic with respect to the ambient magnetosheath plasma. Instead, the fast jet plasma pushes ambient magnetosheath plasma ahead of the jet out of the way, possibly generating anomalous sunward flows in the vicinity, and modifies the magnetic field aligning it with the direction of jet propagation.

Impact of a drop onto a wetted wall: description of crown formation and propagation

NASA Astrophysics Data System (ADS)

Roisman, I. V.; Tropea, C.

2002-12-01

The impact of a drop onto a liquid film with a relatively high impact velocity, leading to the formation of a crown-like ejection, is studied theoretically. The motion of a kinematic discontinuity in the liquid film on the wall due to the drop impact, the formation of the upward jet at this kinematic discontinuity and its elevation are analysed. Four main regions of the drop and film are considered: the perturbed liquid film on the wall inside the crown, the unperturbed liquid film on the wall outside the crown, the upward jet forming a crown, and the free rim bounding this jet. The theory of Yarin & Weiss (1995) for the propagation of the kinematic discontinuity is generalized here for the case of arbitrary velocity vectors in the inner and outer liquid films on the wall. Next, the mass, momentum balance and Bernoulli equations at the base of the crown are considered in order to obtain the velocity and the thickness of the jet on the wall. Furthermore, the dynamic equations of motion of the crown are developed in the Lagrangian form. An analytical solution for the crown shape is obtained in the asymptotic case of such high impact velocities that the surface tension and the viscosity effects can be neglected in comparison to inertial effects. The edge of the crown is described by the motion of a rim, formed due to the surface tension.

Spray nozzle designs for agricultural aviation applications. [relation of drop size to spray characteristics and nozzle efficiency

NASA Technical Reports Server (NTRS)

Lee, K. W.; Putnam, A. A.; Gieseke, J. A.; Golovin, M. N.; Hale, J. A.

1979-01-01

Techniques of generating monodisperse sprays and information concerning chemical liquids used in agricultural aviation are surveyed. The periodic dispersion of liquid jet, the spinning disk method, and ultrasonic atomization are the techniques discussed. Conceptually designed spray nozzles for generating monodisperse sprays are assessed. These are based on the classification of the drops using centrifugal force, on using two opposing liquid laden air jets, and on operating a spinning disk at an overloaded flow. Performance requirements for the designs are described and estimates of the operational characteristics are presented.

A comparative study on liquid core formulation on the diameter on the alginate capsules

NASA Astrophysics Data System (ADS)

Ong, Hui-Yen; Lee, Boon-Beng; Radzi, AkmalHadi Ma'; Zakaria, Zarina; Chan, Eng-Seng

2015-08-01

Liquid core capsule has vast application in biotechnology related industries such as pharmaceutical, medical, agriculture and food. Formulation of different types of capsule was important to determine the performance of the capsule. Generally, the liquid core capsule with different formulations generated different size of capsule.Therefore, the aim of this project is to investigate the effect of different liquid core solution formulations on the diameter of capsule. The capsule produced by extruding liquid core solutions into sodium alginate solution. Three types of liquid core solutions (chitosan, xanthan gum, polyethylene glycol (PEG)) were investigated. The results showed that there is significant change in capsule diameter despite in different types of liquid core solution were used and a series of capsule range in diameter of 3.1 mm to 4.5 mm were produced. Alginate capsule with chitosan formulation appeared to be the largest capsule among all.

Location of γ -ray emission and magnetic field strengths in OJ 287

DOE PAGES

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.; ...

2017-01-06

We report the γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotronmore » self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. Finally, we therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.« less

Evidence for a nuclear radio jet and its structure down to ≲100 Schwarzschild radii in the center of the Sombrero galaxy (M 104, NGC 4594)

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

Hada, Kazuhiro; Giroletti, Marcello; Giovannini, Gabriele

2013-12-10

The Sombrero galaxy (M 104, NGC 4594) is associated with one of the nearest low-luminosity active galactic nuclei (AGNs). We investigated the detailed radio structure of the Sombrero nucleus using high-resolution, quasi-simultaneous, multi-frequency, phase-referencing Very Long Baseline Array observations. We obtained high-quality images of this nucleus at seven frequencies, where those at 15, 24, and 43 GHz are the first clear very long baseline interferometry detections. At 43 GHz, the nuclear structure was imaged on a linear scale under 0.01 pc or 100 Schwarzschild radii, revealing a compact, high-brightness-temperature (≳ 3 × 10{sup 9} K) radio core. We discovered themore » presence of the extended structure emanating from the core on two sides in the northwest and southeast directions. The nuclear radio spectra show a clear spatial gradient, which is similar to that seen in more luminous AGNs with powerful relativistic jets. Moreover, the size and position of the core tend to be frequency dependent. These findings provide evidence that the central engine of the Sombrero is powering radio jets and the jets are overwhelming the emission from the underlying radiatively inefficient accretion flow over the observed frequencies. Based on these radio characteristics, we constrained the following physical parameters for the M 104 jets: (1) the northern side is approaching, whereas the southern one is receding; (2) the jet viewing angle is relatively close to our line-of-sight (≲ 25°); and (3) the intrinsic jet velocity is highly sub-relativistic (≲ 0.2c). The derived pole-on nature of the M 104 jets is consistent with the previous argument that this nucleus contains a true type II AGN, i.e., the broad line region is actually absent or intrinsically weak if the plane of the circumnuclear torus is perpendicular to the jet axis.« less

Location of γ -ray emission and magnetic field strengths in OJ 287

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

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.

We report the γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotronmore » self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. Finally, we therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.« less

Supercritical Mixing in a Shear Coaxial Injector

DTIC Science & Technology

2016-07-27

in the core of the injected fluid emphasizes this observation. Two acoustically excited cases: pressure node and pressure anti-node at the center... acoustically excited cases: pressure node and pressure anti-node at the center plane of the jet are also studied in the same manner. The pressure anti-node...shortens the core flow of the injected jet. I. Introduction OCKET engines present a unique environment for injection of the propellants due to

Numerical simulation of the gas-liquid interaction of a liquid jet in supersonic crossflow

NASA Astrophysics Data System (ADS)

Li, Peibo; Wang, Zhenguo; Sun, Mingbo; Wang, Hongbo

2017-05-01

The gas-liquid interaction process of a liquid jet in supersonic crossflow with a Mach number of 1.94 was investigated numerically using the Eulerian-Lagrangian method. The KH (Kelvin-Helmholtz) breakup model was used to calculate the droplet stripping process, and the secondary breakup process was simulated by the competition of RT (Rayleigh-Taylor) breakup model and TAB (Taylor Analogy Breakup) model. A correction of drag coefficient was proposed by considering the compressible effects and the deformation of droplets. The location and velocity models of child droplets after breakup were improved according to droplet deformation. It was found that the calculated spray features, including spray penetration, droplet size distribution and droplet velocity profile agree reasonably well with the experiment. Numerical results revealed that the streamlines of air flow could intersect with the trajectory of droplets and are deflected towards the near-wall region after they enter into spray zone around the central plane. The analysis of gas-liquid relative velocity and droplet deformation suggested that the breakup of droplets mainly occurs around the front region of the spray where gathered a large number of droplets with different sizes. The liquid trailing phenomenon of jet spray which has been discovered by the previous experiment was successfully captured, and a reasonable explanation was given based on the analysis of gas-liquid interaction process.

Effect of gas mass flux on cryogenic liquid jet breakup

NASA Technical Reports Server (NTRS)

Ingebo, R. D.

1992-01-01

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

A Computational and Experimental Investigation of Shear Coaxial Jet Atomization

NASA Technical Reports Server (NTRS)

Ibrahim, Essam A.; Kenny, R. Jeremy; Walker, Nathan B.

2006-01-01

The instability and subsequent atomization of a viscous liquid jet emanated into a high-pressure gaseous surrounding is studied both computationally and experimentally. Liquid water issued into nitrogen gas at elevated pressures is used to simulate the flow conditions in a coaxial shear injector element relevant to liquid propellant rocket engines. The theoretical analysis is based on a simplified mathematical formulation of the continuity and momentum equations in their conservative form. Numerical solutions of the governing equations subject to appropriate initial and boundary conditions are obtained via a robust finite difference scheme. The computations yield real-time evolution and subsequent breakup characteristics of the liquid jet. The experimental investigation utilizes a digital imaging technique to measure resultant drop sizes. Data were collected for liquid Reynolds number between 2,500 and 25,000, aerodynamic Weber number range of 50-500 and ambient gas pressures from 150 to 1200 psia. Comparison of the model predictions and experimental data for drop sizes at gas pressures of 150 and 300 psia reveal satisfactory agreement particularly for lower values of investigated Weber number. The present model is intended as a component of a practical tool to facilitate design and optimization of coaxial shear atomizers.

Computational Flame Characterization of New Large Aircraft Immersed in Hydrocarbon Pool Fires

DTIC Science & Technology

2013-08-01

hydrocarbon liquid pool fires, their interaction with engulfed bodies, along with a brief overview of pool fire modeling. An industry-accepted...two-dimensional (2-D) horizontal liquid , heavy hydrocarbon fuel surface. A heavy hydrocarbon is characterized by properties consistent with aviation... jet fuels representing common diesel derivatives, such as Jet A and JP-8. Pool diameters are assumed to be much greater than 1 m to coincide with

Method and apparatus for cutting and abrading with sublimable particles

DOEpatents

Bingham, D.N.

1995-10-10

A gas delivery system provides a first gas as a liquid under extreme pressure and as a gas under intermediate pressure. Another gas delivery system provides a second gas under moderate pressure. The second gas is selected to solidify at a temperature at or above the temperature of the liquefied gas. A nozzle assembly connected to the gas delivery systems produces a stream containing a liquid component, a solid component, and a gas component. The liquid component of the stream consists of a high velocity jet of the liquefied first gas. The high velocity jet is surrounded by a particle sheath that consists of solid particles of the second gas which solidifies in the nozzle upon contact with the liquefied gas of the high velocity jet. The gas component of the stream is a high velocity flow of the first gas that encircles the particle sheath, forming an outer jacket. 6 figs.

Method and apparatus for cutting and abrading with sublimable particles

DOEpatents

Bingham, Dennis N.

1995-01-01

A gas delivery system provides a first gas as a liquid under extreme pressure and as a gas under intermediate pressure. Another gas delivery system provides a second gas under moderate pressure. The second gas is selected to solidify at a temperature at or above the temperature of the liquified gas. A nozzle assembly connected to the gas delivery systems produces a stream containing a liquid component, a solid component, and a gas component. The liquid component of the stream consists of a high velocity jet of the liquified first gas. The high velocity jet is surrounded by a particle sheath that consists of solid particles of the second gas which solidifies in the nozzle upon contact with the liquified gas of the high velocity jet. The gas component of the stream is a high velocity flow of the first gas that encircles the particle sheath, forming an outer jacket.

Preliminary Simulations of the Ullage Dynamics in Microgravity During the Jet Mixing Portion of Tank Pressure Control Experiments

NASA Technical Reports Server (NTRS)

Breisacher, Kevin; Moder, Jeffrey

2015-01-01

The results of CFD simulations of microgravity tank pressure control experiments performed on the Space Shuttle are presented. A 13.7 liter acrylic model tank was used in these experiments. The tank was filled to an 83 percent fill fraction with Freon refrigerant to simulate cryogenic propellants stored in space. In the experiments, a single liquid jet near the bottom of the tank was used for mixing the tank. Simulations at a range of jet Weber numbers were performed. Qualitative comparisons of the liquid and gas interface dynamics observed and recorded in the experiments and those computed are shown and discussed. The simulations were able to correctly capture jet penetration of the ullage, qualitatively reproduce ullage shapes and dynamics, as well as the final equilibrium position of the ullage.

Preliminary Simulations of the Ullage Dynamics in Microgravity during the Jet Mixing Portion of Tank Pressure Control Experiments

NASA Technical Reports Server (NTRS)

Breisacher, Kevin; Moder, Jeffrey

2015-01-01

The results of CFD simulations of microgravity tank pressure control experiments performed on the Space Shuttle are presented. A 13.7 liter acrylic model tank was used in these experiments. The tank was filled to an 83 percent fill fraction with Freon refrigerant to simulate cryogenic propellants stored in space. In the experiments, a single liquid jet near the bottom of the tank was used for mixing the tank. Simulations at a range of jet Weber numbers were performed. Qualitative comparisons of the liquid and gas interface dynamics observed and recorded in the experiments and those computed are shown and discussed. The simulations were able to correctly capture jet penetration of the ullage, qualitatively reproduce ullage shapes and dynamics, as well as the final equilibrium position of the ullage.

Reconciling Models of Luminous Blazars with Magnetic Fluxes Determined by Radio Core-shift Measurements

NASA Astrophysics Data System (ADS)

Nalewajko, Krzysztof; Sikora, Marek; Begelman, Mitchell C.

2014-11-01

Estimates of magnetic field strength in relativistic jets of active galactic nuclei, obtained by measuring the frequency-dependent radio core location, imply that the total magnetic fluxes in those jets are consistent with the predictions of the magnetically arrested disk (MAD) scenario of jet formation. On the other hand, the magnetic field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy distribution (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton mechanism. This high Compton dominance may be difficult to reconcile with the MAD scenario, unless (1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or (2) most gamma-ray radiation is produced in jet regions of low magnetization, e.g., in magnetic reconnection layers or in fast jet spines.

RECONCILING MODELS OF LUMINOUS BLAZARS WITH MAGNETIC FLUXES DETERMINED BY RADIO CORE-SHIFT MEASUREMENTS

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

Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek, E-mail: knalew@stanford.edu

2014-11-20

Estimates of magnetic field strength in relativistic jets of active galactic nuclei, obtained by measuring the frequency-dependent radio core location, imply that the total magnetic fluxes in those jets are consistent with the predictions of the magnetically arrested disk (MAD) scenario of jet formation. On the other hand, the magnetic field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy distribution (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton mechanism. This high Comptonmore » dominance may be difficult to reconcile with the MAD scenario, unless (1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or (2) most gamma-ray radiation is produced in jet regions of low magnetization, e.g., in magnetic reconnection layers or in fast jet spines.« less

Multiwaveband Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Correlated Polarization Behavior

NASA Astrophysics Data System (ADS)

Jorstad, Svetlana G.; Marscher, Alan P.; Stevens, Jason A.; Smith, Paul S.; Forster, James R.; Gear, Walter K.; Cawthorne, Timothy V.; Lister, Matthew L.; Stirling, Alastair M.; Gómez, José L.; Greaves, Jane S.; Robson, E. Ian

2007-08-01

We report on multifrequency linear polarization monitoring of 15 active galactic nuclei containing highly relativistic jets with apparent speeds from ~4c to >40c. The measurements were obtained at optical, 1 mm, and 3 mm wavelengths, and at 7 mm with the Very Long Baseline Array. The data show a wide range in degree of linear polarization among the sources, from <1% to >30%, and interday polarization variability in individual sources. The polarization properties suggest separation of the sample into three groups with low, intermediate, and high variability of polarization in the core at 7 mm (LVP, IVP, and HVP, respectively). The groups are partially associated with the common classification of active galactic nuclei as radio galaxies and quasars with low optical polarization (LVP), BL Lacertae objects (IVP), and highly optically polarized quasars (HVP). Our study investigates correlations between total flux, fractional polarization, and polarization position angle at the different wavelengths. We interpret the polarization properties of the sources in the sample through models in which weak shocks compress turbulent plasma in the jet. The differences in the orientation of sources with respect to the observer, jet kinematics, and abundance of thermal matter external to the jet near the core can account for the diversity in the polarization properties. The results provide strong evidence that the optical polarized emission originates in shocks, most likely situated between the 3 and 7 mm VLBI cores. They also support the idea that the 1 mm core lies at the edge of the transition zone between electromagnetically dominated and turbulent hydrodynamic sections of the jet.

Pressure ratio effects on self-similar scalar mixing of high-pressure turbulent jets in a pressurized volume

NASA Astrophysics Data System (ADS)

Ruggles, Adam; Pickett, Lyle; Frank, Jonathan

2014-11-01

Many real world combustion devices model fuel scalar mixing by assuming the self-similar argument established in atmospheric free jets. This allows simple prediction of the mean and rms fuel scalar fields to describe the mixing. This approach has been adopted in super critical liquid injections found in diesel engines where the liquid behaves as a dense fluid. The effect of pressure ratio (injection to ambient) when the ambient is greater than atmospheric pressure, upon the self-similar collapse has not been well characterized, particularly the effect upon mixing constants, jet spreading rates, and virtual origins. Changes in these self-similar parameters control the reproduction of the scalar mixing statistics. This experiment investigates the steady state mixing of high pressure ethylene jets in a pressurized pure nitrogen environment for various pressure ratios and jet orifice diameters. Quantitative laser Rayleigh scattering imaging was performed utilizing a calibration procedure to account for the pressure effects upon scattering interference within the high-pressure vessel.

Experimental verification of the thermodynamic properties for a jet-A fuel

NASA Technical Reports Server (NTRS)

Graciasalcedo, Carmen M.; Brabbs, Theodore A.; Mcbride, Bonnie J.

1988-01-01

Thermodynamic properties for a Jet-A fuel were determined by Shell Development Company in 1970 under a contract for NASA Lewis Research Center. The polynomial fit necessary to include Jet-A fuel (liquid and gaseous phases) in the library of thermodynamic properties of the NASA Lewis Chemical Equilibrium Program is calculated. To verify the thermodynamic data, the temperatures of mixtures of liquid Jet-A injected into a hot nitrogen stream were experimentally measured and compared to those calculated by the program. Iso-octane, a fuel for which the thermodynamic properties are well known, was used as a standard to calibrate the apparatus. The measured temperatures for the iso-octane/nitrogen mixtures reproduced the calculated temperatures except for a small loss due to the non-adiabatic behavior of the apparatus. The measurements for Jet-A were corrected for this heat loss and showed excellent agreement with the calculated temperatures. These experiments show that this process can be adequately described by the thermodynamic properties fitted for the Chemical Equilibrium Program.

Experimental application of pulsed Ho:YAG laser-induced liquid jet as a novel rigid neuroendoscopic dissection device.

PubMed

Ohki, Tomohiro; Nakagawa, Atsuhiro; Hirano, Takayuki; Hashimoto, Tokitada; Menezes, Viren; Jokura, Hidefumi; Uenohara, Hiroshi; Sato, Yasuhiko; Saito, Tsutomu; Shirane, Reizo; Tominaga, Teiji; Takayama, Kazuyoshi

2004-01-01

Although water jet technology has been considered as a feasible neuroendoscopic dissection methodology because of its ability to perform selective tissue dissection without thermal damage, problems associated with continuous use of water and the ensuing fountain-effect-with catapulting of the tissue-could make water jets unsuitable for endoscopic use, in terms of safety and ease of handling. Therefore, the authors experimented with minimization of water usage during the application of a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ), while assuring the dissection quality and the controllability of a conventional water jet dissection device. We have developed the LILJ generator for use as a rigid neuroendoscope, discerned its mechanical behavior, and evaluated its dissection ability using the cadaveric rabbit ventricular wall. The LILJ generator is incorporated into the tip of a stainless steel tube (length: 22 cm; internal diameter: 1.0 mm; external diameter: 1.4 mm), so that the device can be inserted into a commercial, rigid neuroendoscope. Briefly, the LILJ is generated by irradiating an internally supplied water column within the stainless steel tube using the pulsed Ho:YAG laser (wave length: 2.1 microm, pulse duration time: 350 microseconds) and is then ejected through the metal nozzle (internal diameter: 100 microm). The Ho:YAG laser pulse energy is conveyed through optical quartz fiber (core diameter: 400 microm), while cold water (5 degrees C) is internally supplied at a rate of 40 ml/hour. The relationship between laser energy (range: 40-433 mJ/pulse), standoff distance (defined as the distance between the tip of the optical fiber and the nozzle end; range: 10-30 mm), and the velocity, shape, pressure, and average volume of the ejected jet were analyzed by means of high-speed camera, PVDF needle hydrophone, and digital scale. The quality of the dissection plane, the preservation of blood vessels, and the penetration depth were evaluated using five fresh cadaveric rabbit ventricular walls, under neuroendoscopic vision. Jet velocity (7.0-19.6 m/second) and pressure (0.07-0.28 MPa) could be controlled by varying the laser energy, which determined the penetration depth in the cadaveric rabbit ventricular wall (0.07-1.30 mm/shot). The latter could be cut into desirable shapes-without thermal effects-under clear neuroendoscopic vision. The average volume of a single ejected jet could be confined to 0.42-1.52 microl/shot, and there was no accompanying generation of shock waves. Histological specimens revealed a sharp dissection plane and demonstrated that blood vessels of diameter over 100 microm could be preserved, without thermal damage. The present pulsed LILJ system holds promise as a safe and reliable dissection device for deployment in a rigid neuroendoscope. Copyright 2004 Wiley-Liss, Inc.

Discovery of an optical synchrotron jet in 3C 264

NASA Technical Reports Server (NTRS)

Crane, P.; Peletier, R.; Baxter, D.; Sparks, W. B.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Deharveng, J. M.; Disney, M. J.

1993-01-01

Observations with the Faint Object Camera on board the Hubble Space Telescope have revealed a new optical jet in the core of the elliptical galaxy NGC 3862 (3C 264). Morphologically, this jet is similar to the synchrotron jets seen in other galaxies, as it shows knots and bifurcations. The optical spectral index is also similar to that found in other jets. Thus, the nucleus of NGC 3862 appears to contain the fifth known example of an optical synchrotron jet. Since NGC 3862 is a typical radio-loud elliptical galaxy, it seems likely that many nonthermal jets found in the radio continuum may also have optical counterparts.

LeMMINGs - I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

NASA Astrophysics Data System (ADS)

Baldi, R. D.; Williams, D. R. A.; McHardy, I. M.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Muxlow, T. W. B.; Aalto, S.; Alberdi, A.; Bendo, G. J.; Corbel, S.; Evans, R.; Fenech, D. M.; Green, D. A.; Klöckner, H.-R.; Körding, E.; Kharb, P.; Maccarone, T. J.; Martí-Vidal, I.; Mundell, C. G.; Panessa, F.; Peck, A. B.; Pérez-Torres, M. A.; Saikia, D. J.; Saikia, P.; Shankar, F.; Spencer, R. E.; Stevens, I. R.; Uttley, P.; Westcott, J.

2018-05-01

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H II galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H II galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s-1: LINERs and H II galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ˜107 M⊙, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H II galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H II galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

Jetting from impact of a spherical drop with a deep layer

NASA Astrophysics Data System (ADS)

Zhang, Li; Toole, Jameson; Fazzaa, Kamel; Deegan, Robert; Deegan Group Team; X-Ray Science Division, Advanced Photon Source Collaboration

2011-11-01

We performed an experimental study of jets during the impact of a spherical drop with a deep layer of same liquid. Using high speed optical and X-ray imaging, we observe two types of jets: the so-called ejecta sheet which emerges almost immediately after impact and the lamella which emerges later. For high Reynolds number the two jets are distinct, while for low Reynolds number the two jets combine into a single continuous jet. We also measured the emergence time, speed, and position of the ejecta sheet and found simple scaling relations for these quantities.

The First VLBI Detection of a Spiral DRAGN Core

NASA Astrophysics Data System (ADS)

Mao, Minnie Y.; Blanchard, Jay M.; Owen, Frazer; Sjouwerman, Loránt O.; Singh, Vikram; Scaife, Anna; Paragi, Zsolt; Norris, Ray P.; Momjian, Emmanuel; Johnson, Gia; Browne, Ian

2018-05-01

We present the first observation of 0313-192, the archetypal spiral DRAGN, at VLBI resolutions. Spiral DRAGNs are Double Radio Sources Associated with Galactic Nuclei (DRAGNs) that are hosted by spiral galaxies. 0313-192 is an edge-on spiral galaxy that appears to host a 360 kpc double-lobed radio source. The core of this galaxy is clearly detected at L, S, and X-bands using the VLBA, signifying an ongoing active nucleus in the galaxy. This rules out the possibility that the spiral DRAGN is merely a chance alignment. The radio core has L1.4 GHz ˜ 3.0 × 1023 W Hz-1. Radio components are detected to the South-West of the core, but there are no detections of a counterjet. Assuming a symmetric, relativistic jet, we estimate an upper limit to the inclination angle of θ ≲ 72 degrees. The VLBI-detected radio jet components are extremely well-aligned with the larger-scale radio source suggested little to no jet disruption or interaction with the ISM of the host galaxy.

The first VLBI detection of a spiral DRAGN core

NASA Astrophysics Data System (ADS)

Mao, Minnie Y.; Blanchard, Jay M.; Owen, Frazer; Sjouwerman, Loránt O.; Singh, Vikram; Scaife, Anna; Paragi, Zsolt; Norris, Ray P.; Momjian, Emmanuel; Johnson, Gia; Browne, Ian

2018-07-01

We present the first observation of 0313-192, the archetypal spiral DRAGN, at very long baseline interferometry (VLBI) resolutions. Spiral DRAGNs are Double-lobed Radio sources Associated with Galactic Nuclei (DRAGNs) that are hosted by spiral galaxies. 0313-192 is an edge-on spiral galaxy that appears to host a 360 kpc double-lobed radio source. The core of this galaxy is clearly detected at L, S, and X bands using the Very Long Baseline Array, signifying an ongoing active nucleus in the galaxy. This rules out the possibility that the spiral DRAGN is merely a chance alignment. The radio core has L1.4 GHz ˜ 3.0 × 1023 W Hz-1. Radio components are detected to the south-west of the core, but there are no detections of a counterjet. Assuming a symmetric, relativistic jet, we estimate an upper limit to the inclination angle of θ ≲ 72 deg. The VLBI-detected radio jet components are extremely well aligned with the larger scale radio source suggesting little to no jet disruption or interaction with the interstellar medium of the host galaxy.

Characterizing G-Loading, Swirl Direction, and Rayleigh Losses in an Ultra Compact Combustor

DTIC Science & Technology

2013-07-01

temperature, pressure, and emission measurements, and liquid fuel and Jet Cat control. The code layout and functionality was simple in comparison to...84 3.6.4. Cavity Air Jet Diameter Influence on g-Loading...21 Figure 15. Cavity air injection jet diameter relationship to g-loading and tangential velocity [4] 22 Figure

High air volume to low liquid volume aerosol collector

DOEpatents

Masquelier, Donald A.; Milanovich, Fred P.; Willeke, Klaus

2003-01-01

A high air volume to low liquid volume aerosol collector. A high volume flow of aerosol particles is drawn into an annular, centripetal slot in a collector which directs the aerosol flow into a small volume of liquid pool contained is a lower center section of the collector. The annular jet of air impinges into the liquid, imbedding initially airborne particles in the liquid. The liquid in the pool continuously circulates in the lower section of the collector by moving to the center line, then upwardly, and through assistance by a rotating deflector plate passes back into the liquid at the outer area adjacent the impinging air jet which passes upwardly through the liquid pool and through a hollow center of the collector, and is discharged via a side outlet opening. Any liquid droplets escaping with the effluent air are captured by a rotating mist eliminator and moved back toward the liquid pool. The collector includes a sensor assembly for determining, controlling, and maintaining the level of the liquid pool, and includes a lower centrally located valve assembly connected to a liquid reservoir and to an analyzer for analyzing the particles which are impinged into the liquid pool.

From the CMV Oleander Project: A Study of the Shelfbreak Front of the Middle Atlantic Bight From Long-term ADCP and Hydrographic Data

NASA Astrophysics Data System (ADS)

Flagg, C. N.; Dunn, M.; Wang, D.

2004-12-01

Utilizing the first decade of shipboard ADCP data as well as XBT and surface salinity data obtained from the CMV Oleander, this study is focused on the mean structure, and seasonal and interannual variability of the frontal zone at the edge of the shelf of the Middle Atlantic Bight. The early analysis showed that more than half the data in the frontal zone were influenced by warm core rings and that removing the confounding influence of the rings was vital if the true structure of the front was to emerge. From the culled data set of 128 transects of the front with sufficient coverage we have proceeded to generate a velocity description following the core of the frontal jet showing a maximum, surface intensified velocity of more than 0.25 ms-1, a vertical extent of roughly 80 m, a half-amplitude width of about 20 km and an alongshore transport of ~0.34 Sv. The maximum mean relative vorticity of the jet is 0.56*f. The alongshore jet is accompanied by a substantial surface intensified convergent flow that implies a maximum down-welling in the center of the jet of ~30 m/day. The seasonally the shelfbreak jet has its minimal velocities during the summer months, increasing to maximal velocities during the winter before decreasing agin in the spring. An interesting feature that emerges from the ADCP data is that while the shelfbreak frontal jet is usually assumed to consist of a single high-speed core, in fact, the jet often exhibits multiple high velocity extrema, the existence of which appears to undergo a seasonal progression.

The Jet/Disk Connection in AGN: Chandra and XMM-Newton Observations of Three Powerful Radio-Loud Quasars

NASA Technical Reports Server (NTRS)

Sambruna, Rita; Gliozzi, Mario; Tavecchio, F.; Maraschi, L.; Foschini, Luigi

2007-01-01

The connection between the accretion process that powers AGN and the formation of jets is still poorly understood. Here we tackle this issue using new, deep Chandra and XMM-Newton observations of tlie cores of three powerful radio loud quasars: 1136-135, 1150+497 (Chandra), and 0723+679 (XMM-Newton), in the redshift range z=0.3-0.8. These sources are known from our previous Chandra siiapsliot survey to liave kpc-scale X-ray jets. In 1136-135 and 1150-1+497; evidence is found for the presence of diffuse thermal X-ray emission around the cores; on scales of 40-50 kpc and with luminosity L(sub 0.3-2 kev approx. 10(sup 43) erg per second, suggesting thermal emission from the host galaxy or a galaxy group. The X-ray continua of the cores in the three sources are described by an upward-curved (concave) broken power law, with photon indices GAMMA (sub soft) approx. 1.8 - 2.1 and GAMMA (sub hard) approx. 1.7 below and above approx. equal to 2 keV, respectively. There is evidence for an uiiresolved Fe K alpha line with EW approx. 70 eV in the three quasars. The Spectral Energy Distributions of the sources can be well described by a mix of jet and disk emission, with the jet dominating the radio and hard X-rays (via synchrotron and external Compton) and the disk dominating the optical/UV through soft X-rays. The ratio of the jet-to-disk powers is approx. 1, consistent with those derived for a number of gamma ray emitting blazars. This indicates that near equality of accretion and jet power may be common in powerful radio-loud AGN.

Jet Stability and the Generation of Superluminal and Stationary Components

NASA Technical Reports Server (NTRS)

Agudo, Ivan; Gomez, Jose-Luis; Marti, Jose-Maria; Ibanez, Jose-Maria; Marscher, Alan P.; Alberdi, Antonio; Aloy, Miguel-Angel; Hardee, Philip E.

2001-01-01

We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component instead of being ejected from the core. Their oblique nature should also result in distinct polarization properties. Those appearing closer to the core show small apparent motions and a very slow secular decrease in brightness and could be identified as stationary components. Those appearing farther downstream are weaker and can reach superluminal apparent motions. The existence of these trailing components indicates that not all observed components necessarily represent major perturbations at the jet inlet; rather, multiple emission components can be generated by a single disturbance in the jet. While the superluminal component associated with the primary perturbation exhibits a rather stable pattern speed, trailing components have velocities that increase with distance from the core but move at less than the jet speed. The trailing components exhibit motion and structure consistent with the triggering of pinch modes by the superluminal component. The increase in velocity of the trailing components is an indirect consequence of the acceleration of the expanding fluid, which is assumed to be relativistically hot; if observed, such accelerations would therefore favor an electron-positron (as opposed to proton rest mass) dominated jet.

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 μs 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.

Imaging and Variability Studies of CTA 102 during the 2016 January γ-ray Flare

NASA Astrophysics Data System (ADS)

Li, Xiaofeng; Mohan, P.; An, T.; Hong, Xiaoyu; Cheng, Xiaopeng; Yang, Jun; Zhang, Yingkang; Zhang, Zhongli; Zhao, Wei

2018-02-01

The γ-ray-bright blazar CTA 102 is studied using imaging (new 15 GHz and archival 43 GHz Very Long Baseline Array, VLBA data) and time variable optical flux density, polarization degree, and electric vector position angle (EVPA) spanning between 2015 June 1 and 2016 October 1, covering a prominent γ-ray flare during 2016 January. The pc-scale jet indicates expansion with oscillatory features up to 17 mas. Component proper motions are in the range 0.04–0.33 mas yr‑1 with acceleration up to 1.2 mas followed by a slowing down beyond 1.5 mas. A jet bulk Lorentz factor ≥17.5, position angle of 128.°3, inclination angle ≤6.°6 and intrinsic half opening angle ≤1.°8 are derived from the VLBA data. These inferences are employed in a helical jet model to infer long-term variability in flux density, polarization degree, EVPA, and a rotation of the Stokes Q and U parameters. A core distance of r core,43 GHz = 22.9 pc, and a magnetic field strength at 1 pc and the core location of 1.57 G and 0.07 G, respectively, are inferred using the core-shift method. The study is useful in the context of estimating jet parameters and in offering clues to distinguish mechanisms responsible for variability over different timescales.

A new view on the M 87 jet origin: Turbulent loading leading to large-scale episodic wiggling

NASA Astrophysics Data System (ADS)

Britzen, S.; Fendt, C.; Eckart, A.; Karas, V.

2017-05-01

Context. The nearby, giant radio galaxy M 87 hosts a supermassive black hole (BH) and is well-known for a bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large BH mass, M 87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. Many kinematic studies have been performed to determine the proper motions in the jet. Despite M 87 providing all proofs of being an active BH, the apparent jet speed remained puzzling, because proper motion measurements between 15 and 43 GHz for the same region of 1-10 mas core distance provided largely discrepant results. This source is a prime object to be studied in exquisite detail with the upcoming Event Horizon Telescope (EHT) observations because it promises to allow a direct view on the jet launching process itself. Aims: We aim to decipher some of the kinematic puzzles in the pc-scale jet with the analysis we present here. Methods: We re-modeled and re-analyzed 31 VLBA observations at 15 GHz obtained within the MOJAVE program. The data span a time range between Jul. 1995 and May 2011. We performed a detailed investigation of the pc-scale jet kinematics on different timescales, the shortest periods between the observations beeing 10 and 80 days, and in different jet modes, making use of VLBA observations. In addition, we studied the jet ridge line behavior as a function of time. Special care was taken to analyze the region close to the 15 GHz core, and the dynamics and distribution of newly emerging jet features in the jet. Results: We find an indication for apparent superluminal motion in the jet. Moreover, we present evidence for acceleration between 0.5 and 10 mas of core separation. The data suggest that the central part of M 87 at 15 GHz seems to be rotating. Jet components and counter-jet components are ejected in different directions under varying angles, explaining the impression of a broad opening angle. In this paper we present evidence for two different operating modes of the jet of M 87. The jet switches between two phases: I) the jet ridge line is at least double or the jet axis is displaced vertically, and II) an unperturbed phase where the jet ridge line remains almost straight but is smoothly curved and the jet components are aligned along a classical jet axis. The mode change occurs every couple of years. Between the two operating modes, a transition phase is visible. Conclusions: The M 87 jet visible at 15 GHz probes a different physical zone compared to the standard blazar-zone we tend to see in AGN jets. The most likely scenario explaining the observed phenomena is a turbulent mass loading into the jet, most probably due to local, fast reconnection processes driven by turbulence of a tangled magnetic field, which is either generated in the accretion disk or the disk corona. In addition, on large scales, a global magnetic structure is required to channel the turbulent flow into what evolves into a large-scale jet. Large-scale jet instabilities may explain the curved pattern of the observed jet flow.

Study of Mechanisms of Filamentary Pulse Electric Discharge Interaction with Gaseous Flow of Nonuniform Composition

DTIC Science & Technology

2013-06-01

dynamic and localization in subsonic and supersonic airflow also at presence of second gas jet and spray jet of liquid hydrocarbons. The experiments...the specific localization of pulse filamentary discharge in vicinity of boundary between two gases and between liquid spray and gas . The...17, 1, 2010 3. M. A. Deminsky, I. V. Kochetov, S. B. Leonov, А. P. Napartovich, “Modeling of plasma assisted combustion in premixed supersonic gas

Ventless pressure control of two-phase propellant tanks in microgravity.

PubMed

Kassemi, Mohammad; Panzarella, Charles H

2004-11-01

This work studies pressurization and pressure control of a large liquid hydrogen storage tank. A finite element model is developed that couples a lumped thermodynamic formulation for the vapor region with a complete solution of the Navier-Stokes and energy equations for the flow and temperature fields in the liquid. Numerical results show that buoyancy effects are strong, even in microgravity, and can reposition a vapor bubble that is initially at the center of the tank to a region near the tank wall in a relatively short time. Long-term tank pressurization with the vapor bubble at the tank wall shows that after an initial transient lasting about a week, the final rate of pressure increase agrees with a purely thermodynamic analysis of the entire tank. However, the final pressure levels are quite different from thermodynamic predictions. Numerical results also show that there is significant thermal stratification in the liquid due to the effects of natural convection. A subcooled jet is used to provide simultaneous cooling and mixing in order to bring the tank pressure back down to its initial value. Three different jet speeds are examined. Although the lowest jet speed is ineffective at controlling the pressure because of insufficient penetration into the liquid region, the highest jet speed is shown to be quite effective at disrupting thermal stratification and reducing the tank pressure in reasonable time.

Ventless pressure control of two-phase propellant tanks in microgravity

NASA Technical Reports Server (NTRS)

Kassemi, Mohammad; Panzarella, Charles H.

2004-01-01

This work studies pressurization and pressure control of a large liquid hydrogen storage tank. A finite element model is developed that couples a lumped thermodynamic formulation for the vapor region with a complete solution of the Navier-Stokes and energy equations for the flow and temperature fields in the liquid. Numerical results show that buoyancy effects are strong, even in microgravity, and can reposition a vapor bubble that is initially at the center of the tank to a region near the tank wall in a relatively short time. Long-term tank pressurization with the vapor bubble at the tank wall shows that after an initial transient lasting about a week, the final rate of pressure increase agrees with a purely thermodynamic analysis of the entire tank. However, the final pressure levels are quite different from thermodynamic predictions. Numerical results also show that there is significant thermal stratification in the liquid due to the effects of natural convection. A subcooled jet is used to provide simultaneous cooling and mixing in order to bring the tank pressure back down to its initial value. Three different jet speeds are examined. Although the lowest jet speed is ineffective at controlling the pressure because of insufficient penetration into the liquid region, the highest jet speed is shown to be quite effective at disrupting thermal stratification and reducing the tank pressure in reasonable time.

Free-surface liquid jet impingement on rib patterned superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Maynes, D.; Johnson, M.; Webb, B. W.

2011-05-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on hydrophilic, hydrophobic, and superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 1900. The superhydrophobic surfaces are fabricated with both hydrophobically coated silicon and polydimethylsiloxane that exhibit alternating microribs and cavities. For all surfaces a transition from a thin radially moving liquid sheet occurs. This takes the form of the classical hydraulic jump for the hydrophilic surfaces but is markedly different for the hydrophobic and superhydrophobic surfaces, where the transition is significantly influenced by surface tension and a break-up into droplets is observed at high Weber number. For the superhydrophobic surfaces, the transition exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. However, the total projected area of the ellipse exhibits a nearly linear dependence on the jet Weber number, and was nominally invariant with varying hydrophobicity and relative size of the ribs and cavities. For the hydrophobic and superhydrophobic scenarios, the local Weber number based on the local radial velocity and local depth of the radially moving liquid sheet is observed to be of order unity at the transition location. The results also reveal that for increasing relative size of the cavities, the ratio of the ellipse axis (major-to-minor) increases.

Parsec-Scale Kinematic and Polarization Properties of MOJAVE AGN Jets

NASA Astrophysics Data System (ADS)

Lister, Matthew L.

2013-12-01

We describe the parsec-scale kinematics and statistical polarization properties of 200 AGN jets based on 15 GHz VLBA data obtained between 1994 Aug 31 and 2011 May 1. Nearly all of the 60 most heavily observed jets show significant changes in their innermost position angle over a 12 to 16 year interval, ranging from 10° to 150° on the sky, corresponding to intrinsic variations of ~ 0.5° to ~ 2°. The BL Lac jets show smaller variations than quasars. Roughly half of the heavily observed jets show systematic position angle trends with time, and 20 show indications of oscillatory behavior. The time spans of the data sets are too short compared to the fitted periods (5 to 12 y), however, to reliably establish periodicity. The rapid changes and large jumps in position angle seen in many cases suggest that the superluminal AGN jet features occupy only a portion of the entire jet cross section, and may be energized portions of thin instability structures within the jet. We have derived vector proper motions for 887 moving features in 200 jets having at least five VLBA epochs. For 557 well-sampled features, there are sufficient data to additionally study possible accelerations. The moving features are generally non-ballistic, with 70% of the well-sampled features showing either significant accelerations or non-radial motions. Inward motions are rare (2% of all features), are slow (< 0.1 mas per y), are more prevalent in BL Lac jets, and are typically found within 1 mas of the unresolved core feature. There is a general trend of increasing apparent speed with distance down the jet for both radio galaxies and BL Lac objects. In most jets, the speeds of the features cluster around a characteristic value, yet there is a considerable dispersion in the distribution. Orientation variations within the jet cannot fully account for the dispersion, implying that the features have a range of Lorentz factor and/or pattern speed. Very slow pattern speed features are rare, comprising only 4% of the sample, and are more prevalent in radio galaxy and BL Lac jets. We confirm a previously reported upper envelope to the distribution of speed versus beamed luminosity for moving jet features. Below 1026 W Hz-1 there is a fall-off in maximum speed with decreasing 15 GHz radio luminosity. A preliminary analysis of the multi-epoch jet polarization properties indicates a wide range of behavior in the core electric vector position angles over time, with the latter remaining relatively stable in some jets, and varying rapidly in others. The fractional polarization level generally increases down the jet, and high-synchrotron peaked (HSP) blazars tend to have lower core fractional polarization levels. A general trend of decreasing maximum jet speed for higher synchrotron peaked blazars further suggests lower Doppler factors in the radio-emitting jets of HSP BL Lac objects.

Impact of Air Injection on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Norum, Tom

2007-01-01

The objective of this viewgraph presentation is to review the program to determine impact of core fluidic chevrons on noise produced by dual stream jets (i.e., broadband shock noise - supersonic, and mixing noise - subsonic and supersonic). The presentation reviews the sources of jet noise. It shows designs of Generation II Fluidic Chevrons. The injection impacts shock structure and stream disturbances through enhanced mixing. This may impact constructive interference between acoustic sources. The high fan pressures may inhibit mixing produced by core injectors. A fan stream injection may be required for better noise reduction. In future the modification of Gen II nozzles to allow for some azimuthal control: will allow for higher mass flow rates and will allow for shallower injection angles A Flow field study is scheduled for spring, 2008 The conclusions are that injection can reduce well-defined shock noise and injection reduces mixing noise near peak jet noise angle

Air mass origins and troposphere-to-stratosphere exchange associated with mid-latitude cyclogenesis and tropopause folding inferred from Be-7 measurements

NASA Technical Reports Server (NTRS)

Kritz, Mark A.; Rosner, Stefan W.; Danielsen, Edwin F.; Selkirk, Henry B.

1991-01-01

The 1984 extratropical mission of NASA's Stratosphere-Troposphere Exchange Project (STEP) studied cross-jet transport in regions of cyclogenesis and tropopause folding. Correlations of Be-7, ozone, water vapor, and potential vorticity measured on a NASA U-2 research aircraft flying in high shear regions above the jet core are indicative of mixing between the cyclonic and the anticyclonic sides of the jet and are consistent with the hypothesis that small-scale entrainments of upper tropospheric air into the lower stratosphere during cyclogenesis are important in maintaining the vertical gradients of Be-7, ozone, water vapor and other trace constituents in the lower few kilometers of the midlatitude stratosphere. Correlations between Be-7, and ozone suggest a lower tropical stratospheric origin for the ozone-poor lamina observed above the jet core.

A (likely) X-ray jet from NGC6217 observed by XMM-Newton

NASA Astrophysics Data System (ADS)

Falocco, Serena; Larsson, Josefin; Nandi, Sumana

2017-12-01

NGC6217 is a nearby spiral galaxy with a starburst region near its centre. Evidence for a low-luminosity Active Galactic Nucleus (AGN) in its core has also been found in optical spectra. Intriguingly, X-ray observations by ROSAT revealed three knots aligned with the galaxy centre, resembling a jet structure. This paper presents a study of XMM-Newton observations made to assess the hypothesis of a jet emitted from the centre of NGC6217. The XMM data confirm the knots found with ROSAT and our spectral analysis shows that they have similar spectral properties with a hard photon index Γ ∼ 1.7. The core of NGC6217 is well fitted by a model with an AGN and a starburst component, where the AGN contributes at most 46 per cent of the total flux. The candidate jet has an apparent length ∼15 kpc and a luminosity of ∼5 × 1038 erg s- 1. It stands out by being hosted by a spiral galaxy, since jets are more widely associated with ellipticals. To explain the jet launching mechanism we consider the hypothesis of an advection dominated accretion flow with a low accretion rate. The candidate jet emitted from NGC6217 is intriguing since it represents a challenge to the current knowledge of the connection between AGN, jets and host galaxies.

Bubble pinch-off and scaling during liquid drop impact on liquid pool

NASA Astrophysics Data System (ADS)

Ray, Bahni; Biswas, Gautam; Sharma, Ashutosh

2012-08-01

Simulations are performed to show entrapment of air bubble accompanied by high speed upward and downward water jets when a water drop impacts a pool of water surface. A new bubble entrapment zone characterised by small bubble pinch-off and long thick jet is found. Depending on the bubble and jet behaviour, the bubble entrapment zone is subdivided into three sub-regimes. The entrapped bubble size and jet height depends on the crater shape and its maximum depth. During the bubble formation, bubble neck develops an almost singular shape as it pinches off. The final pinch-off shape and the power law governing the pinching, rneck ∝ A(t0 - t)αvaries with the Weber number. Weber dependence of the function describing the radius of the bubble during the pinch-off only affects the coefficient A and not the power exponent α.

Integrated coke, asphalt and jet fuel production process and apparatus

DOEpatents

Shang, Jer Y.

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.

Computer simulation of turbulent jet structure radiography

NASA Astrophysics Data System (ADS)

Kodimer, Kory A.; Parnell, Lynn A.; Nelson, Robert S.; Papin, Patrick J.

1992-12-01

Liquid metal combustion chambers are under consideration as power sources for propulsion devices used in undersea vehicles. Characteristics of the reactive jet are studied to gain information about the internal combustion phenomena, including temporal and spatial variation of the jet flame, and the effects of phase changes on both the combustion and imaging processes. A ray tracing program which employs simplified Monte Carlo methods has been developed for use as a predictive tool for radiographic imaging of closed liquid metal combustors. A complex focal spot is characterized by either a monochromatic or polychromatic emission spectrum. For the simplest case, the x-ray detection system is modeled by an integrating planar detector having 100% efficiency. Several simple geometrical shapes are used to simulate jet structures contained within the combustor, such as cylinders, paraboloids, and ellipsoids. The results of the simulation and real time radiographic images are presented and discussed.

Deformation of a liquid surface induced by an air jet

NASA Astrophysics Data System (ADS)

He, Andong; Belmonte, Andrew

2008-11-01

An experimental and theoretical study is performed to characterize the depression of a liquid surface due to an air jet exiting a nozzle from above. The Reynolds number of the jet is confined to a moderate range(˜100). In order to obtain more stable surface profiles, we use a viscous fluid (silicone oil) instead of water. Based on the data acquired from experiments, we find how the depth and diameter of the cavity are dependent on the radius and height of the nozzle, and the exit velocity of the jet. Theoretical explanations are provided both in the two dimensional (2-D) and three dimensional (3-D) cases. In the 2-D case, a free surface equation and the asymptotic expansion of its solution are obtained by employing a conformal mapping method. In the 3-D case where this technique fails, we propose a different model using an exact axisymmetric solution to Euler's equation.

Terminal velocity of liquids and granular materials dispersed by a high explosive

NASA Astrophysics Data System (ADS)

Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

2018-05-01

The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass ( M/ C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/ C ratio, with larger M/ C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

Terminal velocity of liquids and granular materials dispersed by a high explosive

NASA Astrophysics Data System (ADS)

Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

2018-04-01

The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass (M/C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/C ratio, with larger M/C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

Powder bed binder jet 3D printing of Inconel 718: Densification, microstructural evolution and challenges

DOE PAGES

Nandwana, Peeyush; Elliott, Amy M.; Siddel, Derek; ...

2017-01-03

Traditional manufacturing of Inconel 718 components from castings and thermomechanical processing routes involve extensive post processing and machining to attain the desired geometry. Additive manufacturing (AM) technologies including direct energy deposition (DED), selective laser melting (SLM), electron beam melting (EBM) and binder jet 3D printing (BJ3DP) can minimize scrap generation and reduce lead times. While there is extensive literature on the use of melting and solidification based AM technologies, there has been limited research on the use of binder jet 3D printing. In this paper, a brief review on binder jet additive manufacturing of Inconel 718 is presented. In addition,more » existing knowledge on sintering of Inconel 718 has been extended to binder jet 3D printing. We found that supersolidus liquid phase sintering (SLPS) is necessary to achieve full densification of Inconel 718. SLPS is sensitive to the feedstock chemistry that has a strong influence on the liquid volume fraction at the processing temperature. Based on these results, we discuss an empirical framework to determine the role of powder particle size and liquid volume fraction on sintering kinetics. In conclusion, the role of powder packing factor and binder saturation on microstructural evolution is discussed. The current challenges in the use of BJ3DP for fabrication of Inconel 718, as well as, extension to other metal systems, are presented.« less

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

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

Örley, F., E-mail: felix.oerley@aer.mw.tum.de; Trummler, T.; Mihatsch, M. S.

We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The thermodynamic model is embedded into an implicit large-eddy simulation (LES) environment. The considered configuration follows the general setup of a reference experiment and is a generic reproduction of a scaled-up fuel injector or control valve asmore » found in an automotive engine. Due to the experimental conditions, it operates, however, at significantly lower pressures. LES results are compared to the experimental reference for validation. Three different operating points are studied, which differ in terms of the development of cavitation regions and the jet break-up characteristics. Observed differences between experimental and numerical data in some of the investigated cases can be caused by uncertainties in meeting nominal parameters by the experiment. The investigation reveals that three main mechanisms promote primary jet break-up: collapse-induced turbulent fluctuations near the outlet, entrainment of free gas into the nozzle, and collapse events inside the jet near the liquid-gas interface.« less

Liquid filament instability due to stretch-induced phase separation in polymer solutions

NASA Astrophysics Data System (ADS)

Arinstein, Arkadii; Kulichikhin, Valery; Malkin, Alexander; Technion-Israel Institute of Technology Collaboration; Institute of Petrochemical Synthesis, Russian Academy of Sciences Team

2015-03-01

The instability in a jet of a viscoelastic semi-dilute entangled polymer solution under high stretching is discussed. Initially, the variation in osmotic pressure can compensate for decrease in the capillary force, and the jet is stable. The further evolution of the polymer solution along the jet results in formation of a filament in the jet center and of a near-surface solvent layer. Such a redistribution of polymer seems like a ``phase separation'', but it is related to stretching of the jet. The viscous liquid shell demonstrates Raleigh-type instability resulting in the formation of individual droplets on the oriented filament. Experimental observations showed that this separation is starting during few first seconds, and continues of about 10 -15 seconds. The modeling shows that a jet stretching results in a radial gradient in the polymer distribution: the polymer is concentrated in the jet center, whereas the solvent is remaining near the surface. The key point of this model is that a large longitudinal stretching of a polymer network results in its lateral contraction, so a solvent is pressed out of this polymer network because of the decrease in its volume. V.K. and A.M. acknowledge the financial support of the Russian Scientific Foundation (Grant 4-23-00003).

Alternate Fuels for Use in Commercial Aircraft

NASA Technical Reports Server (NTRS)

Daggett, David L.; Hendricks, Robert C.; Walther, Rainer; Corporan, Edwin

2008-01-01

The engine and aircraft Research and Development (R&D) communities have been investigating alternative fueling in near-term, midterm, and far-term aircraft. A drop in jet fuel replacement, consisting of a kerosene (Jet-A) and synthetic fuel blend, will be possible for use in existing and near-term aircraft. Future midterm aircraft may use a biojet and synthetic fuel blend in ultra-efficient airplane designs. Future far-term engines and aircraft in 50-plus years may be specifically designed to use a low- or zero-carbon fuel. Synthetic jet fuels from coal, natural gas, or other hydrocarbon feedstocks are very similar in performance to conventional jet fuel, yet the additional CO2 produced during the manufacturing needs to be permanently sequestered. Biojet fuels need to be developed specifically for jet aircraft without displacing food production. Envisioned as midterm aircraft fuel, if the performance and cost liabilities can be overcome, biofuel blends with synthetic jet or Jet-A fuels have near-term potential in terms of global climatic concerns. Long-term solutions address dramatic emissions reductions through use of alternate aircraft fuels such as liquid hydrogen or liquid methane. Either of these new aircraft fuels will require an enormous change in infrastructure and thus engine and airplane design. Life-cycle environmental questions need to be addressed.

The Hydrodynamics of Needle-Free Intradermal Jet Injection

NASA Astrophysics Data System (ADS)

Simmons, Jonathan; Marston, Jeremy; Fisher, Paul; Broderick, Kate

2017-11-01

Needle-free methods of drug delivery circumvent the drawbacks associated with the use of hypodermic needles such as needle-stick injuries, needle-phobia, cross contamination and disposal. Furthermore, pioneering DNA-based vaccines that aim to treat cancer and fight infectious diseases, such as HIV, Ebola and Zika, require precise deposition into the skin to target the immune response producing cells found only in the epidermis and dermis. Intradermal (ID) delivery can be achieved using a needle and the Mantoux technique but this requires a highly skilled technician and so extensive use of DNA vaccines calls for an alternative method of delivery. One option is jet injection which has been employed in mass vaccination programs for intramuscular or subcutaneous delivery and is used by some diabetic patients to inject insulin. In this talk I will present results from our ongoing ex-vivo experimental study into ID jet injection. Ultra-high-speed imaging is used to visualize the process of the jet exiting the nozzle and striking excised skin. A skin bleb grows as liquid is deposited within the skin. I will discuss how the control parameters, such as the rheological profile of the liquid and the stand-off distance, influence the volume of liquid successfully delivered intradermally.

Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet

NASA Astrophysics Data System (ADS)

Reddemann, Manuel A.; Mathieu, Florian; Kneer, Reinhold

2013-11-01

Aiming at a maximum spatial resolution and a minimum motion blur, a new simple double-imaging transmitted light microscopy technique is developed in this work enabling a fundamental investigation of primary breakup of a microscale liquid jet. Contrary to conventional far-field visualization techniques, the working distance is minimized to increase the numerical aperture. The resulting images provide information about shapes, length scales and velocities of primary liquid structures. The method is applied to an optically dense spray leaving a 109-μm diesel nozzle at various injection pressures under atmospheric conditions. A phenomenological study on the temporal spray evolution is done with focus on droplet and ligament formation. Different breakup processes are identified and described. It is found that the jet is characterized by long ligaments parallel or angular to the inner jet region. These ligaments result from collapsing films developing at the spray edge. A significant influence of outlet velocity variation on shape and velocity of these ligaments is observed. The experimental results prove that a transmitted light microscopy technique with reduced working distance is an appropriate tool for a better understanding of primary breakup for small-scaled diesel nozzles and a valuable complement to highly complex measurement techniques.

High Resolution Spectroscopy and Dynamics: from Jet Cooled Radicals to Gas-Liquid Interfaces

NASA Astrophysics Data System (ADS)

Sharp-Williams, E.; Roberts, M. A.; Roscioli, J. R.; Gisler, A. W.; Ziemkiewicz, M.; Nesbitt, D. J.; Dong, F.; Perkins, B. G., Jr.

2010-06-01

This talk will attempt to reflect recent work in our group involving two quite different but complementary applications of high resolution molecular spectroscopy for detailed study of intramolecular as well as intermolecular dynamics in small molecules. The first is based on direct infrared absorption spectroscopy in a 100 KHz slit supersonic discharge, which provides a remarkably versatile and yet highly sensitive probe for study of important chemical transients such as open shell combustion species and molecular ions under jet cooled (10-20K), sub-Doppler conditions. For this talk will focus on gas phase spectroscopic results for a series of unsaturated hydrocarbon radical species (ethynyl, vinyl, and phenyl) reputed to be critical intermediates in soot formation. Secondly, we will discuss recent applications of high resolution IR and velocity map imaging spectroscopy toward quantum state resolved collision dynamics of jet cooled molecules from gas-room temperature ionic liquid (RTIL) and gas-self assembled monolayer (SAM) interfaces. Time permitting, we will also present new results on hyperthermal scattering of jet cooled NO radical from liquid Ga, which offer a novel window into non-adiabatic energy transfer and electron-hole pair dynamics at the gas-molten metal interface.

Parsec-scale Faraday rotation and polarization of 20 active galactic nuclei jets

NASA Astrophysics Data System (ADS)

Kravchenko, E. V.; Kovalev, Y. Y.; Sokolovsky, K. V.

2017-05-01

We perform polarimetry analysis of 20 active galactic nuclei jets using the very long baseline array at 1.4, 1.6, 2.2, 2.4, 4.6, 5.0, 8.1, 8.4 and 15.4 GHz. The study allowed us to investigate linearly polarized properties of the jets at parsec scales: distribution of the Faraday rotation measure (RM) and fractional polarization along the jets, Faraday effects and structure of Faraday-corrected polarization images. Wavelength dependence of the fractional polarization and polarization angle is consistent with external Faraday rotation, while some sources show internal rotation. The RM changes along the jets, systematically increasing its value towards synchrotron self-absorbed cores at shorter wavelengths. The highest core RM reaches 16 900 rad m-2 in the source rest frame for the quasar 0952+179, suggesting the presence of highly magnetized, dense media in these regions. The typical RM of transparent jet regions has values of an order of a hundred rad m-2. Significant transverse RM gradients are observed in seven sources. The magnetic field in the Faraday screen has no preferred orientation, and is observed to be random or regular from source to source. Half of the sources show evidence for the helical magnetic fields in their rotating magneto-ionic media. At the same time jets themselves contain large-scale, ordered magnetic fields and tend to align its direction with the jet flow. The observed variety of polarized signatures can be explained by a model of spine-sheath jet structure.

A wide and collimated radio jet in 3C84 on the scale of a few hundred gravitational radii

NASA Astrophysics Data System (ADS)

Giovannini, G.; Savolainen, T.; Orienti, M.; Nakamura, M.; Nagai, H.; Kino, M.; Giroletti, M.; Hada, K.; Bruni, G.; Kovalev, Y. Y.; Anderson, J. M.; D'Ammando, F.; Hodgson, J.; Honma, M.; Krichbaum, T. P.; Lee, S.-S.; Lico, R.; Lisakov, M. M.; Lobanov, A. P.; Petrov, L.; Sohn, B. W.; Sokolovsky, K. V.; Voitsik, P. A.; Zensus, J. A.; Tingay, S.

2018-06-01

Understanding the formation of relativistic jets in active galactic nuclei remains an elusive problem1. This is partly because observational tests of jet formation models suffer from the limited angular resolution of ground-based very-long-baseline interferometry that has thus far been able to probe the structure of the jet acceleration and collimation region in only two sources2,3. Here, we report observations of 3C84 (NGC 1275)—the central galaxy of the Perseus cluster—made with an interferometric array including the orbiting radio telescope of the RadioAstron4 mission. The data transversely resolve the edge-brightened jet in 3C84 only 30 μas from the core, which is ten times closer to the central engine than was possible in previous ground-based observations5 and allows us to measure the jet collimation profile from 102 to 104 gravitational radii (rg) from the black hole. The previously found5, almost cylindrical jet profile on scales larger than a few thousand rg is seen to continue at least down to a few hundred rg from the black hole, and we find a broad jet with a transverse radius of ≳250 rg at only 350 rg from the core. This implies that either the bright outer jet layer goes through a very rapid lateral expansion on scales ≲102 rg or it is launched from the accretion disk.

A wide and collimated radio jet in 3C84 on the scale of a few hundred gravitational radii

NASA Astrophysics Data System (ADS)

Giovannini, G.; Savolainen, T.; Orienti, M.; Nakamura, M.; Nagai, H.; Kino, M.; Giroletti, M.; Hada, K.; Bruni, G.; Kovalev, Y. Y.; Anderson, J. M.; D'Ammando, F.; Hodgson, J.; Honma, M.; Krichbaum, T. P.; Lee, S.-S.; Lico, R.; Lisakov, M. M.; Lobanov, A. P.; Petrov, L.; Sohn, B. W.; Sokolovsky, K. V.; Voitsik, P. A.; Zensus, J. A.; Tingay, S.

2018-04-01

Understanding the formation of relativistic jets in active galactic nuclei remains an elusive problem1. This is partly because observational tests of jet formation models suffer from the limited angular resolution of ground-based very-long-baseline interferometry that has thus far been able to probe the structure of the jet acceleration and collimation region in only two sources2,3. Here, we report observations of 3C84 (NGC 1275)—the central galaxy of the Perseus cluster—made with an interferometric array including the orbiting radio telescope of the RadioAstron4 mission. The data transversely resolve the edge-brightened jet in 3C84 only 30 μas from the core, which is ten times closer to the central engine than was possible in previous ground-based observations5 and allows us to measure the jet collimation profile from 102 to 104 gravitational radii (rg) from the black hole. The previously found5, almost cylindrical jet profile on scales larger than a few thousand rg is seen to continue at least down to a few hundred rg from the black hole, and we find a broad jet with a transverse radius of ≳250 rg at only 350 rg from the core. This implies that either the bright outer jet layer goes through a very rapid lateral expansion on scales ≲102 rg or it is launched from the accretion disk.

Plasma confinement at JET

NASA Astrophysics Data System (ADS)

Nunes, I.; JET Contributors

2016-01-01

Operation with a Be/W wall at JET (JET-ILW) has an impact on scenario development and energy confinement with respect to the carbon wall (JET-C). The main differences observed were (1) strong accumulation of W in the plasma core and (2) the need to mitigate the divertor target temperature to avoid W sputtering by Be and other low Z impurities and (3) a decrease of plasma energy confinement. A major difference is observed on the pedestal pressure, namely a reduction of the pedestal temperature which, due to profile stiffness the plasma core temperature is also reduced leading to a degradation of the global confinement. This effect is more pronounced in low β N scenarios. At high β N, the impact of the wall on the plasma energy confinement is mitigated by the weaker plasma energy degradation with power relative to the IPB98(y, 2) scaling calculated empirically for a CFC first wall. The smaller tolerable impurity concentration for tungsten (<10-5) compared to that of carbon requires the use of electron heating methods to prevent W accumulation in the plasma core region as well as gas puffing to avoid W entering the plasma core by ELM flushing and reduction of the W source by decreasing the target temperature. W source and the target temperature can also be controlled by impurity seeding. Nitrogen and Neon have been used and with both gases the reduction of the W source and the target temperature is observed. Whilst more experiments with Neon are necessary to assess its impact on energy confinement, a partial increase of plasma energy confinement is observed with Nitrogen, through the increase of edge temperature. The challenge for scenario development at JET is to extend the pulse length curtailed by its transient behavior (W accumulation or MHD), but more importantly by the divertor target temperature limits. Re-optimisation of the scenarios to mitigate the effect of the change of wall materials maintaining high global energy confinement similar to JET-C is underway and JET has successfully achieved H 98(y,2)  =  1 for plasma currents up to 2.5 MA at moderate β N.

Multi-Epoch 8.4GHz VLBI Observations of the Nucleus of Centaurus A

NASA Technical Reports Server (NTRS)

Meier, David L.

1992-01-01

We present the results of several 8.4 GHz VLBI observations of the nucleus of Centaurus A. We fing that the source possesses a classical core-jet structure with the inner portion of the jet expanding at a proper motion of 4.o mas yr or an apparet velocity of 0.26c along the jet.

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.

Kelvin-Helmholtz instability of stratified jets.

NASA Astrophysics Data System (ADS)

Hanasz, M.; Sol, H.

1996-11-01

We investigate the Kelvin-Helmholtz instability of stratified jets. The internal component (core) is made of a relativistic gas moving with a relativistic bulk speed. The second component (sheath or envelope) flows between the core and external gas with a nonrelativistic speed. Such a two-component jet describes a variety of possible astrophysical jet configurations like e.g. (1) a relativistic electron-positron beam penetrating a classical electron-proton disc wind or (2) a beam-cocoon structure. We perform a linear stability analysis of such a configuration in the hydrodynamic, plane-parallel, vortex-sheet approximation. The obtained solutions of the dispersion relation show very apparent differences with respect to the single-jet solutions. Due to the reflection of sound waves at the boundary between sheet and external gas, the growth rate as a function of wavenumber presents a specific oscillation pattern. Overdense sheets can slow down the growth rate and contribute to stabilize the configuration. Moreover, we obtain the result that even for relatively small sheet widths the properties of sheet start to dominate the jet dynamics. Such effects could have important astrophysical implications, for instance on the origin of the dichotomy between radio-loud and radio-quiet objects.

Collective Evidence for Inverse Compton Emission from External Photons in High-Power Blazars

NASA Technical Reports Server (NTRS)

Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

2012-01-01

We present the first collective evidence that Fermi-detected jets of high kinetic power (L(sub kin)) are dominated by inverse Compton emission from upscattered external photons. Using a sample with a broad range in orientation angle, including radio galaxies and blazars, we find that very high power sources (L(sub kin) > 10(exp 45.5) erg/s) show a significant increase in the ratio of inverse Compton to synchrotron power (Compton dominance) with decreasing orientation angle, as measured by the radio core dominance and confirmed by the distribution of superluminal speeds. This increase is consistent with beaming expectations for external Compton (EC) emission, but not for synchrotron self Compton (SSC) emission. For the lowest power jets (L(sub kin) < 10(exp 43.5) erg /s), no trend between Compton and radio core dominance is found, consistent with SSC. Importantly, the EC trend is not seen for moderately high power flat spectrum radio quasars with strong external photon fields. Coupled with the evidence that jet power is linked to the jet speed, this finding suggests that external photon fields become the dominant source of seed photons in the jet comoving frame only for the faster and therefore more powerful jets.

High precision laser processing of sensitive materials by Microjet

NASA Astrophysics Data System (ADS)

Sibailly, Ochelio D.; Wagner, Frank R.; Mayor, Laetitia; Richerzhagen, Bernold

2003-11-01

Material laser cutting is well known and widely used in industrial processes, including micro fabrication. An increasing number of applications require nevertheless a superior machining quality than can be achieved using this method. A possibility to increase the cut quality is to opt for the water-jet guided laser technology. In this technique the laser is conducted to the work piece by total internal reflection in a thin stable water-jet, comparable to the core of an optical fiber. The water jet guided laser technique was developed originally in order to reduce the heat damaged zone near the cut, but in fact many other advantages were observed due to the usage of a water-jet instead of an assist gas stream applied in conventional laser cutting. In brief, the advantages are three-fold: the absence of divergence due to light guiding, the efficient melt expulsion, and optimum work piece cooling. In this presentation we will give an overview on several industrial applications of the water-jet guided laser technique. These applications range from the cutting of CBN or ferrite cores to the dicing of thin wafers and the manufacturing of stencils, each illustrates the important impact of the water-jet usage.

Double-peaked Emission Lines Due to a Radio Outflow in KISSR 1219

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

Kharb, P.; Vaddi, S.; Subramanian, S.

We present the results from 1.5 and 5 GHz phase-referenced VLBA and 1.5 GHz Karl G. Jansky Very Large Array (VLA) observations of the Seyfert 2 galaxy KISSR 1219, which exhibits double-peaked emission lines in its optical spectrum. The VLA and VLBA data reveal a one-sided core-jet structure at roughly the same position angles, providing evidence of an active galactic nucleus outflow. The absence of dual parsec-scale radio cores puts the binary black-hole picture in doubt for the case of KISSR 1219. The high brightness temperatures of the parsec-scale core and jet components (>10{sup 6} K) are consistent with thismore » interpretation. Doppler boosting with jet speeds of ≳0.55 c to ≳0.25 c , going from parsec to kiloparsec scales, at a jet inclination ≳50° can explain the jet one-sidedness in this Seyfert 2 galaxy. A blueshifted broad emission line component in [O iii] is also indicative of an outflow in the emission line gas at a velocity of ∼350 km s{sup −1}, while the [O i] doublet lines suggest the presence of shock-heated gas. A detailed line ratio study using the MAPPINGS III code further suggests that a shock+precursor model can explain the line ionization data well. Overall, our data suggest that the radio outflow in KISSR 1219 is pushing the emission line clouds, both ahead of the jet and in a lateral direction, giving rise to the double peak emission line spectra.« less

Nuclear Radio Jet from a Low-luminosity Active Galactic Nucleus in NGC 4258

NASA Astrophysics Data System (ADS)

Doi, Akihiro; Kohno, Kotaro; Nakanishi, Kouichiro; Kameno, Seiji; Inoue, Makoto; Hada, Kazuhiro; Sorai, Kazuo

2013-03-01

The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array at 1.7-43 GHz and the James Clerk Maxwell telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz (α ~ 0.3; F νvpropνα) in time-averaged flux densities, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. Quantitative differences between NGC 4258 and M81 in terms of jet/counter jet ratio, radio loudness, and degree of core shift can be consistently understood by fairly relativistic speeds (Γ >~ 3) of jets and their quite different inclinations. The picture established from the two closest LLAGNs is useful for understanding the physical origin of unresolved and flat/inverted spectrum radio cores that are prevalently found in LLAGNs, including Sgr A*, with starved supermassive black holes in the present-day universe.

Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology

NASA Technical Reports Server (NTRS)

Megaridis, Constantine M.; Bellizia, Giulio; McNallan, Michael; Wallace, David B.

2003-01-01

Surface tension forces play a critical role in fluid dynamic phenomena that are important in materials processing. The surface tension of liquid metals has been shown to be very susceptible to small amounts of adsorbed oxygen. Consequently, the kinetics of oxygen adsorption can influence the capillary breakup of liquid-metal jets targeted for use in electronics assembly applications, where low-melting-point metals (such as tin-containing solders) are utilized as an attachment material for mounting of electronic components to substrates. By interpreting values of surface tension measured at various surface ages, adsorption and diffusion rates of oxygen on the surface of the melt can be estimated. This research program investigates the adsorption kinetics of oxygen on the surface of an atomizing molten-metal jet. A novel oscillating capillary jet method has been developed for the measurement of dynamic surface tension of liquids, and in particular, metal melts which are susceptible to rapid surface degradation caused by oxygen adsorption. The experimental technique captures the evolution of jet swells and necks continuously along the jet propagation axis and is used in conjunction with an existing linear, axisymmetric, constant-property model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated so far focus on a time window of 2-4ms from the jet orifice. The surface properties of the eutectic 63%Sn-37%Pb solder alloy have been investigated in terms of their variation due to O2 adsorption from a N2 atmosphere containing controlled amounts of oxygen (from 8 ppm to 1000 ppm). The method performed well for situations where the oxygen adsorption was low in that time window. The value of surface tension for the 63Sn-37Pb solder in pure nitrogen was found to be 0.49 N/m, in good agreement with previously published work. A characteristic time of O(1ms) or less was determined for the molten-metal surface to be saturated by oxygen at 1000 ppm concentration in N2.

Continuous tuneable droplet ejection via pulsed surface acoustic wave jetting.

PubMed

Castro, Jasmine O; Ramesan, Shwathy; Rezk, Amgad R; Yeo, Leslie Y

2018-05-30

We report a miniaturised platform for continuous production of single or multiple liquid droplets with diameters between 60 and 500 μm by interfacing a capillary-driven self-replenishing liquid feed with pulsed excitation of focussed surface acoustic waves (SAWs). The orifice-free operation circumvents the disadvantages of conventional jetting systems, which are often prone to clogging that eventuates in rapid degradation of the operational performance. Additionally, we show the possibility for flexibly tuning the ejected droplet size through the pulse width duration, thus avoiding the need for a separate device for every different droplet size required, as is the case for systems in which the droplet size is set by nozzles and orifices, as well as preceding ultrasonic jetting platforms where the droplet size is controlled by the operating frequency. Further, we demonstrate that cells can be jetted and hence printed onto substrates with control over the cell density within the droplets down to single cells. Given that the jetting does not lead to significant loss to the cell's viability or ability to proliferate, we envisage that this versatile jetting method can potentially be exploited with further development for cell encapsulation, dispensing and 3D bioprinting applications.

Engineering the Flow of Liquid Two-Phase Systems by Passive Noise Control

NASA Astrophysics Data System (ADS)

Zhang, Zeyi; Kong, Tiantian; Zhou, Chunmei; Wang, Liqiu

2018-02-01

We investigate a passive noise-control approach to engineering the two-phase flow in a microfluidic coflow system. The presence or absence of the jet breakup is studied for two immiscible oil phases, in a straight microchannel (referred to as the J device in the main text), an expansion microchannel (the W device) and a microchannel with the expansion-contraction geometry (the S device), respectively. We show that the jet breaks into droplets, in the jetting regime and the dripping regime (also referred to as the widening-jetting regime) for the straight channel and expansion channel, respectively, while a stable long jet does not break for the expansion-contraction geometry. As the inner phase passes the expansion-contraction functional unit, the random noise on the interface is significantly reduced and the hydrodynamic instability is suppressed, for a range of experimental parameters including flow rates, device geometry, liquid viscosity, and interfacial tension. We further present scale-up devices with multiple noise-control units and achieve decimeter-long yet stable jets. Our simple, effective, and robust noise-control approach can benefit microfluidic applications such as microfiber fabrication, interface chemical reaction, and on-chip distance transportation.

Multiple pulsed hypersonic liquid diesel fuel jetsdriven by projectile impact

NASA Astrophysics Data System (ADS)

Pianthong, K.; Takayama, K.; Milton, B. E.; Behnia, M.

2005-06-01

Further studies on high-speed liquid diesel fuel jets injected into ambient air conditions have been carried out. Projectile impact has been used as the driving mechanism. A vertical two-stage light gas gun was used as a launcher to provide the high-speed impact. This paper describes the experimental technique and visualization methods that provided a rapid series of jet images in the one shot. A high-speed video camera (106 fps) and shadowgraph optical system were used to obtain visualization. Very interesting and unique phenomena have been discovered and confirmed in this study. These are that multiple high frequency jet pulses are generated within the duration of a single shot impact. The associated multiple jet shock waves have been clearly captured. This characteristic consistently occurs with the smaller conical angle, straight cone nozzles but not with those with a very wide cone angle or curved nozzle profile. An instantaneous jet tip velocity of 2680 m/s (Mach number of 7.86) was the maximum obtained with the 40^circ nozzle. However, this jet tip velocity can only be sustained for a few microseconds as attenuation is very rapid.

Noncircular Cross Sections Could Enhance Mixing in Sprays

NASA Technical Reports Server (NTRS)

Bellan, Josette; Abdel-Hameed, Hesham

2003-01-01

A computational study has shown that by injecting drops in jets of gas having square, elliptical, triangular, or other noncircular injection cross sections, it should be possible to increase (relative to comparable situations having circular cross section) the entrainment and dispersion of liquid drops. This finding has practical significance for a variety of applications in which it is desirable to increase dispersion of drops. For example, in chemical-process sprays, increased dispersion leads to increases in chemical- reaction rates; in diesel engines, increasing the dispersion of drops of sprayed fuel reduces the production of soot; and in household and paint sprays, increasing the dispersion of drops makes it possible to cover larger surfaces. It has been known for some years that single-phase fluid jets that enter flow fields through noncircular inlets entrain more fluid than do comparable jets entering through circular inlets. The computational study reported here was directed in part toward determining whether and how this superior mixing characteristic of noncircular single phase jets translates to a similar benefit in cases of two-phase jets (that is, sprays). The study involved direct numerical simulations of single- and two-phase free jets with circular, elliptical, rectangular, square, and triangular inlet cross sections. The two-phase jets consisted of gas laden with liquid drops randomly injected at the inlets. To address the more interesting case of evaporating drops, the carrier gas in the jets was specified to be initially unvitiated by the vapor of the liquid chemical species and the initial temperature of the drops was chosen to be smaller than that of the gas. The mathematical model used in the study was constructed from the conservation equations for the two-phase flow and included complete couplings of mass, momentum, and energy based on thermodynamically self-consistent specification of the enthalpy, internal energy, and latent heat of vaporization of the vapor.

Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. I. Imaging BL Lacertae at 21 Microarcsecond Resolution

NASA Astrophysics Data System (ADS)

Gómez, José L.; Lobanov, Andrei P.; Bruni, Gabriele; Kovalev, Yuri Y.; Marscher, Alan P.; Jorstad, Svetlana G.; Mizuno, Yosuke; Bach, Uwe; Sokolovsky, Kirill V.; Anderson, James M.; Galindo, Pablo; Kardashev, Nikolay S.; Lisakov, Mikhail M.

2016-02-01

We present the first polarimetric space very long baseline interferometry (VLBI) imaging observations at 22 GHz. BL Lacertae was observed in 2013 November 10 with the RadioAstron space VLBI mission, including a ground array of 15 radio telescopes. The instrumental polarization of the space radio telescope is found to be less than 9%, demonstrating the polarimetric imaging capabilities of RadioAstron at 22 GHz. Ground-space fringes were obtained up to a projected baseline distance of 7.9 Earth diameters in length, allowing us to image the jet in BL Lacertae with a maximum angular resolution of 21 μas, the highest achieved to date. We find evidence for emission upstream of the radio core, which may correspond to a recollimation shock at about 40 μas from the jet apex, in a pattern that includes other recollimation shocks at approximately 100 and 250 μas from the jet apex. Polarized emission is detected in two components within the innermost 0.5 mas from the core, as well as in some knots 3 mas downstream. Faraday rotation analysis, obtained from combining RadioAstron 22 GHz and ground-based 15 and 43 GHz images, shows a gradient in rotation measure and Faraday-corrected polarization vector as a function of position angle with respect to the core, suggesting that the jet in BL Lacertae is threaded by a helical magnetic field. The intrinsic de-boosted brightness temperature in the unresolved core exceeds 3× {10}12 K, suggesting, at the very least, departure from equipartition of energy between the magnetic field and radiating particles.

Reducing Propulsion Airframe Aeroacoustic Interactions with Uniquely Tailored Chevrons. 1.; Isolated Nozzles

NASA Technical Reports Server (NTRS)

Mengle, Vinod G.; Elkroby, Ronen; Brunsniak, Leon; Thomas, Russ H.

2006-01-01

The flow/acoustic environment surrounding an engine nozzle installed on an airplane, say, under the wing, is asymmetric due to the pylon, the wing and the interaction of the exhaust jet with flaps on the wing. However, the conventional chevrons, which are azimuthally uniform serrations on the nozzle lip, do not exploit the asymmetry due to these propulsion airframe aeroacoustic interactions to reduce jet noise. In this pioneering study we use this non-axisymmetry to our advantage and examine if the total jet-related noise radiated to the ground can be reduced by using different types of azimuthally varying chevrons (AVC) which vary the mixing around the nozzle periphery. Several scale models of the isolated nozzle, representative of high bypass ratio engine nozzles, were made with a pylon and azimuthally varying chevrons on both fan and core nozzles to enhance mixing at the top (near the pylon) with less mixing at the bottom (away from the pylon) or vice versa. Various combinations of fan and core AVC nozzles were systematically tested at typical take-off conditions inside a free jet wind-tunnel and, here, in Part 1 we analyze the acoustics results for the isolated nozzle with a pylon, with installation effects reported in Parts 2 and 3. Several interesting results are discovered: amongst the fan AVCs the top-enhanced mixing T-fan chevron nozzle is quieter in combination with any core AVC nozzle when compared to conventional chevrons; however, the bottom-mixing B-fan chevrons, as well as the core AVC nozzles, by themselves, are noisier. Further, the low-frequency source strengths in the jet plume, obtained via phased microphone arrays, also corroborate the far field sound, and for the T-fan chevrons such sources move further downstream than those for baseline or conventional chevron nozzles.

System for venting gas from a liquid storage tank

NASA Astrophysics Data System (ADS)

Dugan, Regina E.

1989-07-01

Gas is vented from a non-cryogenic liquid storage tank while discharging pressurized liquid from a tube into the tank through a plurality of inclined jets, circumferentially spaced about an end of a vent tube positioned within the tube. Each jet is directed toward a central axis of the vent tube, such that the end of the vent tube receives gas from the vessel passing between individual jetstreams, which in combination form a conical shaped barrier to liquid droplets which would otherwise also pass to the vent tube and out the tank. Gas is thus vented through the central tube while pressurized liquid flows in an axially opposite direction in the annulus between the inner vent tube and the outer liquid tube. The system of the present invention is prarticularly well suited for venting gas from a tank being replenished with liquid at a zero or near zero gravity environment. A screen-type liquid acquisition device employing surface tension is provided for withdrawing substantially liquid from the tank. The withdrawn liquid may be resupplied to the liquid tube under pressure supplied by a circulating pump, thereby releasing substantially only gas from the storage tank to reduce the pressure in the tank.

Ejector/liquid ring pump provides <0. 30 mm Hg vacuum for polymerization vessel

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

Lockwood, A.; Gaines, A.

1982-03-01

Firestone Fibers and Textiles Company, a division of Firestone Tire and Rubber Company, manufactures tire and industrial yarns of polyester and nylon-6. Nylon-6 molding and extrusion resins are also produced at the plant in Hopewell, Virginia. The process for making polyester requires an extremely low vacuum on the polymerization reactor. A consistent polymerization vessel vacuum of 0.3 mm Hg is needed, but the existing vacuum source, a five-stage steam jet ejector, could only provide a 0.5 mm Hg level. Two options were considered when the company decided to replace the original system with a system designed for 0.15 mm Hgmore » with a non-condensible gas load of 10.8 lb/hr. A new five-stage jet ejector system to meet these requirements would use 1395 lb/hr of 100 psig steam. The other option was a hybrid vacuum source composed of a three-stage steam ejector system and a liquid ring vacuum pump that is more energy efficient than ejectors for low vacuum applications. The hybrid system was selected because the three-stage jet ejector would use only 1240 lb/hr of 100 psig steam. The liquid ring vacuum pump would increase the material and installation cost of the system by about $4000, but the savings in steam consumption would pay back the added cost in less than two years. The jet ejector/liquid ring vacuum pump system has provided both the capacity and the extremely low vacuum needed for the polyester polymerization vessel, after making a small modification. The hybrid vacuum source is reliable, requires only routine maintenance, and will contiue to save substantial amounts of steam each year compared to the five-stage steam jet ejector.« less

Production and correlation of reactive oxygen and nitrogen species in gas- and liquid-phase generated by helium plasma jets under different pulse widths

NASA Astrophysics Data System (ADS)

Liu, Zhijie; Zhou, Chunxi; Liu, Dingxin; Xu, Dehui; Xia, Wenjie; Cui, Qingjie; Wang, Bingchuan; Kong, Michael G.

2018-01-01

In this paper, we present the effects of the pulse width (PW) on the plasma jet's discharge characteristics, particularly focusing on the production and correlation of the reactive oxygen and nitrogen species (RONS) in gas- and liquid-phase. It is found that the length of plasma jet plume first increases before the PW of 10 μs, then gradually decreases and finally almost remains unchanged beyond 150 μs. The plasma bullet disappears after the falling edge of the voltage pulse at low PW, while it terminates far ahead of the falling edge of voltage pulse at high PW. This is mainly attributed to accumulation of space charges that lead to weakening of the reduced electric field with an increase of PW from low to high. More important, it is found that the excited reactive species, the positive and negative ions from plasma jet, and the concentrations of NO2- and NO3- in deionized water exposed to plasma jet also display the first increasing and then decreasing change trend with increase of PW, while the concentration of H2O2 in water almost displays the linearly increasing trend. This mainly results from the formation of the H3O+ and HO2-, as well as their ion water clusters that can produce more OH radicals to be converted into H2O2, while the NO2- and NO3- in gas phase can transport into water and exist most stably in water. The water cluster formation at gas-liquid interface is an important key process that can affect the chemical nature and dose of aqueous RONS in water; this is beneficial for understanding how the RONS are formed in liquid-phase.

Balanced-Rotating-Spray Tank-And-Pipe-Cleaning System

NASA Technical Reports Server (NTRS)

Thaxton, Eric A.; Caimi, Raoul E. B.

1995-01-01

Spray head translates and rotates to clean entire inner surface of tank or pipe. Cleansing effected by three laterally balanced gas/liquid jets from spray head that rotates about longitudinal axis. Uses much less liquid. Cleaning process in system relies on mechanical action of jets instead of contaminant dissolution. Eliminates very difficult machining needed to make multiple converging/diverging nozzles within one spray head. Makes nozzle much smaller. Basic two-phase-flow, supersonic-nozzle design applied to other spray systems for interior or exterior cleaning.

A Numerical Model of Hercules A by Magnetic Tower

NASA Astrophysics Data System (ADS)

Nakamura, Masanori; Tregillis, I. L.; Li, H.; Li, S.

2009-01-01

We apply magnetohydrodynamic (MHD) modeling to the radio galaxy Hercules A for investigating the jet-driven shock, jet/lobe transition, wiggling, and magnetic field distribution associated with this source. The model consists of magnetic tower jets in a galaxy cluster environment. The profile of underlying ambient gas plays an important role in jet-lobe morphology. The balance between the magnetic pressure generated by axial current and the ambient gas pressure can determine the lobe radius. The jet body is confined jointly by the external pressure and gravity inside the cluster core radius, while outside this radius it expands radially to form fat lobes in a steeply decreasing ambient thermal pressure gradient. The current-carrying jets are responsible for generating a strong, tightly wound helical magnetic field. This magnetic configuration will be unstable against the current-driven kink mode and it visibly grows beyond the cluster core radius where a separation between the jet forward and return currents occurs. The reversed pinch profile of global magnetic field associated with the jet and lobes produces projected magnetic-vector distributions aligned with the jet flow and the lobe edge. AGN-driven shock powered by the expanding magnetic tower jet surrounds the jet/lobe structure and heats the ambient ICM. The lobes expand subsonically; no obvious hot spots are produced at the heads of lobes. Several key features in our MHD modeling may be qualitatively supported by the observations of Hercules A. This work was carried out under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. It was supported by the Laboratory Directed Research and Development Program at LANL and by IGPP at LANL.

Curvature singularity and film-skating during drop impact

NASA Astrophysics Data System (ADS)

Duchemin, Laurent; Josserand, Christophe

2011-09-01

We study the influence of the surrounding gas in the dynamics of drop impact on a smooth surface. We use an axisymmetric model for which both the gas and the liquid are incompressible; lubrication regime applies for the gas film dynamics and the liquid viscosity is neglected. In the absence of surface tension a finite time singularity whose properties are analysed is formed and the liquid touches the solid on a circle. When surface tension is taken into account, a thin jet emerges from the zone of impact, skating above a thin gas layer. The thickness of the air film underneath this jet is always smaller than the mean free path in the gas suggesting that the liquid film eventually wets the surface. We finally suggest an aerodynamical instability mechanism for the splash.

A novel metal flow imaging using electrical capacitance tomography

NASA Astrophysics Data System (ADS)

Wondrak, Thomas; Soleimani, Manuchehr

2017-06-01

The measurement of gas-liquid metal two phase flow is a challenging task due to the opaqueness and the high temperatures. For instance, during continuous casting of steel the distribution of argon gas and liquid steel in the submerged entry nozzle is of high interest, since it influences the quality of the produced steel. In this paper we present the results of a feasibility study for applying the electrical capacitance tomography (ECT) to detect the outer surface of a liquid metal stream. The results of this study are the basis for the development of a new contactless sensor which should be able to detect the outer shape of a liquid metal jet using ECT and the bubbles inside the jet at the same time with mutual inductance tomography.

Enhanced Core Noise Modeling for Turbofan Engines

NASA Technical Reports Server (NTRS)

Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J.

2011-01-01

This report describes work performed by MTC Technologies (MTCT) for NASA Glenn Research Center (GRC) under Contract NAS3-00178, Task Order No. 15. MTCT previously developed a first-generation empirical model that correlates the core/combustion noise of four GE engines, the CF6, CF34, CFM56, and GE90 for General Electric (GE) under Contract No. 200-1X-14W53048, in support of GRC Contract NAS3-01135. MTCT has demonstrated in earlier noise modeling efforts that the improvement of predictive modeling is greatly enhanced by an iterative approach, so in support of NASA's Quiet Aircraft Technology Project, GRC sponsored this effort to improve the model. Since the noise data available for correlation are total engine noise spectra, it is total engine noise that must be predicted. Since the scope of this effort was not sufficient to explore fan and turbine noise, the most meaningful comparisons must be restricted to frequencies below the blade passage frequency. Below the blade passage frequency and at relatively high power settings jet noise is expected to be the dominant source, and comparisons are shown that demonstrate the accuracy of the jet noise model recently developed by MTCT for NASA under Contract NAS3-00178, Task Order No. 10. At lower power settings the core noise became most apparent, and these data corrected for the contribution of jet noise were then used to establish the characteristics of core noise. There is clearly more than one spectral range where core noise is evident, so the spectral approach developed by von Glahn and Krejsa in 1982 wherein four spectral regions overlap, was used in the GE effort. Further analysis indicates that the two higher frequency components, which are often somewhat masked by turbomachinery noise, can be treated as one component, and it is on that basis that the current model is formulated. The frequency scaling relationships are improved and are now based on combustor and core nozzle geometries. In conjunction with the Task Order No. 10 jet noise model, this core noise model is shown to provide statistical accuracy comparable to the jet noise model for frequencies below blade passage. This model is incorporated in the NASA FOOTPR code and a user s guide is provided.

Scaling in two-fluid pinch-off

NASA Astrophysics Data System (ADS)

Pommer, Chris; Suryo, Ronald; Subramani, Hariprasad; Harris, Michael; Basaran, Osman

2009-11-01

Two-fluid pinch-off is encountered when drops or bubbles of one fluid are ejected from a nozzle into another fluid or when a compound jet breaks. While the breakup of a drop in a passive environment and that of a passive bubble in a liquid are well understood, the physics of pinch-off when both the inner and outer fluids are dynamically active is inadequately understood. In this talk, the breakup of a compound jet whose core and shell are both incompressible Newtonian fluids is analyzed computationally by a method of lines ALE algorithm which uses finite elements with elliptic mesh generation for spatial discretization and adaptive finite differences for time integration. Pinch-off dynamics are investigated well beyond the limit of experiments set by the wavelength of visible light and that of various algorithms used in the literature. Simulations show that the minimum neck radius r initially scales with time τ before breakup as &αcirc; where α varies over a certain range. However, depending on the values of the governing dimensionless groups, this initial scaling regime may be transitory and, closer to pinch-off, the dynamics may transition to a final asymptotic regime for which r ˜&βcirc;, where β!=α.

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

Volkov, N. B.; Zubarev, N. M., E-mail: nick@iep.uran.ru; Zubareva, O. V.

Exact solutions are obtained for the problem of an equilibrium configuration of an uncharged cylindrical jet of a conducting liquid in a transverse electric field. The transverse cross section of the jet moving between two planar electrodes is deformed under the action of electrostatic forces (capillary forces play a stabilizing role). According to the solutions obtained, the initially circular cross section of the jet may be significantly (formally, unboundedly) stretched along the lines of forces of the field, and the boundaries of the jet asymptotically approach the electrodes.

Investigation of turbulent swirling jet-flames by PIV / OH PLIF / HCHO PLIF

NASA Astrophysics Data System (ADS)

Lobasov, A. S.; Chikishev, L. M.

2018-03-01

The present paper reports on the investigation of fuel-lean and fuel-rich turbulent combustion in a high-swirl jet. Swirl rate of the flow exceeded a critical value for breakdown of the swirling jet’s vortex core and formation of the recirculation zone at the jet axis. The measurements were performed by the stereo PIV, OH PLIF and HCHO PLIF techniques, simultaneously. The Reynolds number based on the flow rate and viscosity of the air was fixed as 5 000 (the bulk velocity was U 0 = 5 m/s). Three cases of the equivalence ratio ϕ of the mixture issuing from the nozzle-burner were considered, viz., 0.7, 1.4 and 2.5. The latter case corresponded to a lifted flame of fuel-rich swirling jet flow, partially premixed with the surrounding air. In all cases the flame front was subjected to deformations due to large-scale vortices, which rolled-up in the inner (around the central recirculation zone) and outer (between the annular jet core and surrounding air) mixing layers.

Modern developments in shear flow control with swirl

NASA Technical Reports Server (NTRS)

Farokhi, Saeed; Taghavi, R.

1990-01-01

Passive and active control of swirling turbulent jets is experimentally investigated. Initial swirl distribution is shown to dominate the free jet evolution in the passive mode. Vortex breakdown, a manifestation of high intensity swirl, was achieved at below critical swirl number (S = 0.48) by reducing the vortex core diameter. The response of a swirling turbulent jet to single frequency, plane wave acoustic excitation was shown to depend strongly on the swirl number, excitation Strouhal number, amplitude of the excitation wave, and core turbulence in a low speed cold jet. A 10 percent reduction of the mean centerline velocity at x/D = 9.0 (and a corresponding increase in the shear layer momentum thickness) was achieved by large amplitude internal plane wave acoustic excitation. Helical instability waves of negative azimuthal wave numbers exhibit larger amplification rates than the plane waves in swirling free jets, according to hydrodynamic stability theory. Consequently, an active swirling shear layer control is proposed to include the generation of helical instability waves of arbitrary helicity and the promotion of modal interaction, through multifrequency forcing.

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.

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

NASA Astrophysics Data System (ADS)

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

2016-05-01

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

Instability of low viscosity elliptic jets with varying aspect ratio

NASA Astrophysics Data System (ADS)

Kulkarni, Varun

2011-11-01

In this work an analytical description of capillary instability of liquid elliptic jets with varying aspect ratio is presented. Linear stability analysis in the long wave approximation with negligible gravitational effects is employed. Elliptic cylindrical coordinate system is used and perturbation velocity potential substituted in the Laplace equation to yield Mathieu and Modified Mathieu differential equations. The dispersion relation for elliptical orifices of any aspect ratio is derived and validated for axisymmetric disturbances with m = 0, in the limit of aspect ratio, μ = 1 , i.e. the case of a circular jet. As Mathieu functions and Modified Mathieu function solutions converge to Bessel's functions in this limit the Rayleigh-Plateau instability criterion is met. Also, stability of solutions corresponding to asymmetric disturbances for the kink mode, m = 1 and flute modes corresponding to m >= 2 is discussed. Experimental data from earlier works is used to compare observations made for elliptical orifices with μ ≠ 1 . This novel approach aims at generalizing the results pertaining to cylindrical jets with circular cross section leading to better understanding of breakup in liquid jets of various geometries.

An investigation of flow-limited field-injection electrostatic spraying (FFESS) and its applications to thin film deposition

NASA Astrophysics Data System (ADS)

Singh, Ravindra Pratap

Electrostatic spraying is the process of controlled disruption of a liquid surface due to excess surface charge density. The technique has found applications in a wide range of fields from agricultural sprays to fuel injectors to colloidal thrusters for space vehicle propulsion. Over the past 20 years, the technique has been intensely studied in material processing for synthesis of ceramic and metal powders, nanoparticles and thin films. The importance of the technique lies in its simple setup, high deposition efficiency, and ambient atmosphere operation. In conventional electrostatic spraying (CESS), one uses a conducting nozzle to charge the liquid, mostly by induction charging. CESS is therefore restricted to the single jet mode of spraying which occurs at low spray currents. It lacks stability and reproducibility in the high current, multiple jet regime, which can generate much finer sprays. In flow-limited field-injection electrostatic spraying (FFESS), one uses a field-injection electrode to stably and controllably inject higher currents into the liquid, a la Fowler-Nordheim, using an otherwise insulating nozzle. This way, it is possible to stably electrospray in the multiple jet mode. In addition to producing much finer sprays, the multi-jet mode atomizes liquids at higher rates, and spreads the spray over a wider region and more uniformly than single jet sprays, thus paving way for large-area uniform thin film deposition. A simple yet comprehensive theory is formulated to describe the multi jet formation. The theory, which is based on the energy minimization principle, takes into account, for the first time, the interactions between charged jets which leads to saturation in the number of jets at high spray currents. The possibility of using an array of nozzles to obtain uniform large-area high-throughput thin film deposition is also investigated. A large number of FFESS nozzles with alternating positive and negative polarities arranged in a periodic 2-dimensional array are found to produce uniform thin films over large areas. Deposition of TiO2 and silver thin films using multi jet FFESS is studied, demonstrating great control on film morphology and properties. TiO2 thin films deposited on high-intensity discharge arc lamps are found to improve the quality of its light output. Silver thin films of high purity and conductivity, and with good adhesion, could be deposited at relatively high deposition rates and high deposition efficiency as compared to CVD techniques.

Hard X-ray Emission from the M87 AGN Detected with NuSTAR

NASA Astrophysics Data System (ADS)

Wong, Ka-Wah; Nemmen, Rodrigo; Irwin, Jimmy; Lin, Dacheng

2018-01-01

M87 hosts a 3–6 billion solar mass black hole with a remarkable relativistic jet that has been regularly monitored in radio to TeV bands. However, hard X-ray emission above 10keV expected to primarily come from the jet or the accretion flow had never been detected from its unresolved X-ray core. We report NuSTAR detection up to 40 keV from the the central regions of M87. Together with simultaneous Chandra observations, we have constrained the dominant hard X-ray emission to be from its unresolved X-ray core, presumably in its quiescent state. The core spectrum is well fitted by a power-law. The measured flux density at 40keV is consistent with a jet origin, although emission from the advection-dominated accretion flow cannot be completely ruled out. The detected hard X-ray emission is significantly lower than that predicted by synchrotron self-Compton models introduced to explain emission above a GeV.

In-liquid arc plasma jet and its application to phenol degradation

NASA Astrophysics Data System (ADS)

Liu, Jing-Lin; Park, Hyun-Woo; Hamdan, Ahmad; Cha, Min Suk

2018-03-01

We present a new method for achieving chemical reactions induced by plasmas with liquids—an in-liquid arc plasma jet system—designed to have a few advantages over the existing methods. High-speed imaging and optical emission spectroscopy were adopted to highlight the physical aspects of the in-liquid arc plasma jet system, and the feasibility of the system was investigated in a wastewater treatment case with phenol as the model contaminant. We found that the specific energy input is a reasonable parameter by which to characterize the overall process. The phenol removal reaction could be modeled as a pseudo-first-order reaction, and the reaction constant became smaller as the phenol concentration increased. However, complete decomposition of the phenol into water and carbon dioxide required very high energy because the final intermediate, oxalic acid, is relatively stable. Detailed chemical and physical analyses, including byproducts, ions, solution acidity, and conductivity, were conducted to evaluate this new method for use in the appropriate applications.

Ceramic micro-injection molded nozzles for serial femtosecond crystallography sample delivery

NASA Astrophysics Data System (ADS)

Beyerlein, K. R.; Adriano, L.; Heymann, M.; Kirian, R.; Knoška, J.; Wilde, F.; Chapman, H. N.; Bajt, S.

2015-12-01

Serial femtosecond crystallography (SFX) using X-ray Free-Electron Lasers (XFELs) allows for room temperature protein structure determination without evidence of conventional radiation damage. In this method, a liquid suspension of protein microcrystals can be delivered to the X-ray beam in vacuum as a micro-jet, which replenishes the crystals at a rate that exceeds the current XFEL pulse repetition rate. Gas dynamic virtual nozzles produce the required micrometer-sized streams by the focusing action of a coaxial sheath gas and have been shown to be effective for SFX experiments. Here, we describe the design and characterization of such nozzles assembled from ceramic micro-injection molded outer gas-focusing capillaries. Trends of the emitted jet diameter and jet length as a function of supplied liquid and gas flow rates are measured by a fast imaging system. The observed trends are explained by derived relationships considering choked gas flow and liquid flow conservation. Finally, the performance of these nozzles in a SFX experiment is presented, including an analysis of the observed background.

Spray visualization of alternative fuels at hot ambient conditions

NASA Astrophysics Data System (ADS)

Kannaiyan, Kumaran; Sadr, Reza

2017-11-01

Gas-to-Liquid (GTL) has gained significant interest as drop-in alternative jet fuel owing to its cleaner combustion characteristics. The physical and evaporation properties of GTL fuels are different from those of the conventional jet fuels. Those differences will have an effect on the spray, and in turn, the combustion performance. In this study, the non-reacting near nozzle spray dynamics such as spray cone angle, liquid sheet breakup and liquid velocity of GTL fuel will be investigated and compared with those of the conventional jet fuel. This work is a follow up of the preliminary study performed at atmospheric ambient conditions where differences were observed in the near nozzle spray characteristics between the fuels. Whereas, in this study the spray visualization will be performed in a hot and inert environment to account for the difference in evaporation characteristics of the fuels. The spray visualization images will be captured using the shadowgraph technique. A rigorous statistical analysis of the images will be performed to compare the spray dynamics between the fuels.

Propagation of gas jet in liquid

NASA Astrophysics Data System (ADS)

Surin, V. A.; Yevchenko, V. N.; Rubin, V. M.

1984-07-01

A comprehensive experimental study was made of discharge of a gas jet from an orifice and its evolution in a liquid medium. Nitrogen, air, helium, chlorine, carbon dioxide, hydrogen chloride, ammonia, and water vapor superheated to 200 to 250 C were discharged vertically up, vertically down, or laterally into water at 18 to 100 C as well as into aqueous solutions of KOH and NaOH, under pressures varied from hydrostatic to 41x10(5) Pa. They were discharged through sonic cylindrical, conical nozzles and supersonic leLaval, axisymmetric, flat nozzles with orifices 2 to 50 mm wide. The discharge velocity varied from 2 to 1000 m/s and the jet underexpansion ratio varied from 1 to 20. The study has yielded data on the mechanisms of gas-liquid interaction, structure and dynamics of the interaction space, and dependence of those on the discharge conditions and on the degree of gas assimilation. Experiments were performed in both continuous and pulse modes, the latter for a study of transients and back shocks.

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

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

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.

Experimental and Theoretical Investigations on Viscosity of Fe-Ni-C Liquids at High Pressures

NASA Astrophysics Data System (ADS)

Chen, B.; Lai, X.; Wang, J.; Zhu, F.; Liu, J.; Kono, Y.

2016-12-01

Understanding and modeling of Earth's core processes such as geodynamo and heat flow via convection in liquid outer cores hinges on the viscosity of candidate liquid iron alloys under core conditions. Viscosity estimates from various methods of the metallic liquid of the outer core, however, span up to 12 orders of magnitude. Due to experimental challenges, viscosity measurements of iron liquids alloyed with lighter elements are scarce and conducted at conditions far below those expected for the outer core. In this study, we adopt a synergistic approach by integrating experiments at experimentally-achievable conditions with computations up to core conditions. We performed viscosity measurements based on the modified Stokes' floating sphere viscometry method for the Fe-Ni-C liquids at high pressures in a Paris-Edinburgh press at Sector 16 of the Advanced Photon Source, Argonne National Laboratory. Our results show that the addition of 3-5 wt.% carbon to iron-nickel liquids has negligible effect on its viscosity at pressures lower than 5 GPa. The viscosity of the Fe-Ni-C liquids, however, becomes notably higher and increases by a factor of 3 at 5-8 GPa. Similarly, our first-principles molecular dynamics calculations up to Earth's core pressures show a viscosity change in Fe-Ni-C liquids at 5 GPa. The significant change in the viscosity is likely due to a liquid structural transition of the Fe-Ni-C liquids as revealed by our X-ray diffraction measurements and first-principles molecular dynamics calculations. The observed correlation between structure and physical properties of liquids permit stringent benchmark test of the computational liquid models and contribute to a more comprehensive understanding of liquid properties under high pressures. The interplay between experiments and first-principles based modeling is shown to be a practical and effective methodology for studying liquid properties under outer core conditions that are difficult to reach with the current static high-pressure capabilities. The new viscosity data from experiments and computations would provide new insights into the internal dynamics of the outer core.

RF cavity using liquid dielectric for tuning and cooling

DOEpatents

Popovic, Milorad [Warrenville, IL; Johnson, Rolland P [Newport News, VA

2012-04-17

A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

Quantitative measurement of binary liquid distributions using multiple-tracer x-ray fluorescence and radiography

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

Halls, Benjamin R.; Meyer, Terrence R.; Kastengren, Alan L.

2015-01-01

The complex geometry and large index-of-refraction gradients that occur near the point of impingement of binary liquid jets present a challenging environment for optical interrogation. A simultaneous quadruple-tracer x-ray fluorescence and line-of-sight radiography technique is proposed as a means of distinguishing and quantifying individual liquid component distributions prior to, during, and after jet impact. Two different pairs of fluorescence tracers are seeded into each liquid stream to maximize their attenuation ratio for reabsorption correction and differentiation of the two fluids during mixing. This approach for instantaneous correction of x-ray fluorescence reabsorption is compared with a more time-intensive approach of usingmore » stereographic reconstruction of x-ray attenuation along multiple lines of sight. The proposed methodology addresses the need for a quantitative measurement technique capable of interrogating optically complex, near-field liquid distributions in many mixing systems of practical interest involving two or more liquid streams.« less

Vibration-Induced Gas-Liquid Interface Breakup

NASA Astrophysics Data System (ADS)

O'Hern, Timothy; Torczynski, John; Romero, Ed; Shelden, Bion

2010-11-01

Gas-liquid interfaces can be forced to break up when subjected to vibrations within critical ranges of frequency and amplitude. This breakup mechanism was examined experimentally using deep layers of silicone oils over a range of viscosity and sinusoidal, primarily axial vibration conditions that can produce dramatic disturbances at the gas-liquid free surface. Although small-amplitude vibrations produce standing Faraday waves, large-amplitude vibrations produce liquid jets into the gas, droplets pinching off from the jets, gas cavities in the liquid from droplet impact, and bubble transport below the interface. Experiments used several different silicone oils over a range of pressures and vibration conditions. Computational simulations exhibiting similar behavior will be included in the presentation. Applications include liquid fuel rockets, inertial sensing devices, moving vehicles, mixing processes, and acoustic excitation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Quantitative measurement of binary liquid distributions using multiple-tracer x-ray fluorescence and radiography

DOE PAGES

Halls, Benjamin R.; Meyer, Terrence R.; Kastengren, Alan L.

2015-01-23

The complex geometry and large index-of-refraction gradients that occur near the point of impingement of binary liquid jets present a challenging environment for optical interrogation. A simultaneous quadruple-tracer x-ray fluorescence and line-of-sight radiography technique is proposed as a means of distinguishing and quantifying individual liquid component distributions prior to, during, and after jet impact. Two different pairs of fluorescence tracers are seeded into each liquid stream to maximize their attenuation ratio for reabsorption correction and differentiation of the two fluids during mixing. This approach for instantaneous correction of x-ray fluorescence reabsorption is compared with a more time-intensive approach of usingmore » stereographic reconstruction of x-ray attenuation along multiple lines of sight. The proposed methodology addresses the need for a quantitative measurement technique capable of interrogating optically complex, near-field liquid distributions in many mixing systems of practical interest involving two or more liquid streams.« less

Conformal mapping technique for two-dimensional porous media and jet impingement heat transfer

NASA Technical Reports Server (NTRS)

Siegel, R.

1974-01-01

Transpiration cooling and liquid metals both provide highly effective heat transfer. Using Darcy's law in porous media and the inviscid approximation for liquid metals, the local fluid velocity in these flows equals the gradient of a potential. The energy equation and flow region are simplified when transformed into potential plane coordinates. In these coordinates, the present problems are reduced to heat conduction solutions which are mapped into the physical geometry. Results are obtained for a porous region with simultaneously prescribed surface temperature and heat flux, heat transfer in a two-dimensional porous bed, and heat transfer for two liquid metal slot jets impinging on a heated plate.

Conformal mapping technique for two-dimensional porous media and jet impingement heat transfer

NASA Technical Reports Server (NTRS)

Siegel, R.

1973-01-01

Transpiration cooling and liquid metals both provide highly effective heat transfer. Using Darcy's law in porous media, and the inviscid approximation for liquid metals, the local fluid velocity in these flows equals the gradient of a potential, The energy equation and flow region are simplified when transformed into potential plane coordinates. In these coordinates the present problems are reduced to heat conduction solutions which are mapped into the physical geometry. Results are obtained for a porous region with simultaneously prescribed surface temperature and heat flux, heat transfer in a two-dimensional porous bed, and heat transfer for two liquid metal slot jets impinging on a heated plate.

Constraints on high-energy neutrino emission from SN 2008D

NASA Astrophysics Data System (ADS)

IceCube Collaboration; Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; Ben Zvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Buitink, S.; Carson, M.; Chirkin, D.; Christy, B.; Clem, J.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; D'Agostino, M. V.; Danninger, M.; Davis, J. C.; De Clercq, C.; Demirörs, L.; Depaepe, O.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Duvoort, M. R.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feusels, T.; Filimonov, K.; Finley, C.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Geisler, M.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Grant, D.; Griesel, T.; Gro, A.; Grullon, S.; Gurtner, M.; Ha, C.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Helbing, K.; Herquet, P.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Homeier, A.; Hoshina, K.; Hubert, D.; Huelsnitz, W.; Hül, J. P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K. H.; Kappes A.; Karg, T.; Karle, A.; Kelley, J. L.; Kemming, N.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J. H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Krings, T.; Kroll, G.; Kuehn, K.; Kuwabara, T.; Labare, M.; Lafebre, S.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lehmann, R.; Lünemann, J.; Madsen, J.; Majumdar, P.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Matusik, M.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nießen, P.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Ono, M.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Prikockis, M.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Rodrigues, J. P.; Roth, P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schlenstedt, S.; Schmidt, T.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Singh, K.; Slipak, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stephens, G.; Stezelberger, T.; Stokstad, R. G.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tarasova, O.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; Turčan, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Voge, M.; Voigt, B.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Wikström, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Woschnagg, K.; Xu, C.; Xu, X. W.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.

2011-03-01

SN 2008D, a core collapse supernova at a distance of 27 Mpc, was serendipitously discovered by the Swift satellite through an associated X-ray flash. Core collapse supernovae have been observed in association with long gamma-ray bursts and X-ray flashes and a physical connection is widely assumed. This connection could imply that some core collapse supernovae possess mildly relativistic jets in which high-energy neutrinos are produced through proton-proton collisions. The predicted neutrino spectra would be detectable by Cherenkov neutrino detectors like IceCube. A search for a neutrino signal in temporal and spatial correlation with the observed X-ray flash of SN 2008D was conducted using data taken in 2007-2008 with 22 strings of the IceCube detector. Events were selected based on a boosted decision tree classifier trained with simulated signal and experimental background data. The classifier was optimized to the position and a "soft jet" neutrino spectrum assumed for SN 2008D. Using three search windows placed around the X-ray peak, emission time scales from 100-10 000 s were probed. No events passing the cuts were observed in agreement with the signal expectation of 0.13 events. Upper limits on the muon neutrino flux from core collapse supernovae were derived for different emission time scales and the principal model parameters were constrained. While no meaningful limits can be given in the case of an isotropic neutrino emission, the parameter space for a jetted emission can be constrained. Future analyses with the full 86 string IceCube detector could detect up to ~100 events for a core-collapse supernova at 10 Mpc according to the soft jet model.

Liquid Water on Enceladus from Observations of Ammonia and Ar-40 in the Plume

NASA Technical Reports Server (NTRS)

Waite, J. H., Jr.; Lewis, W. S.; Magee, B. A.; Lunine, J. I.; McKinnon, W. B.; Glein, C. R.; Mousis, O.; Young, D. T.; Brockwell, T.; Westlake, J.;

Study on the Fluid Flow Characteristics of Coherent Jets with CO2 and O2 Mixed Injection in Electric Arc Furnace Steelmaking Processes

NASA Astrophysics Data System (ADS)

Wei, Guangsheng; Zhu, Rong; Wu, Xuetao; Yang, Lingzhi; Dong, Kai; Cheng, Ting; Tang, Tianping

2018-06-01

As an efficient oxygen supplying technology, coherent jets are widely applied in electric arc furnace (EAF) steelmaking processes to strengthen chemical energy input, speed up smelting rhythm, and promote the uniformity of molten bath temperature and compositions. Recently, the coherent jet with CO2 and O2 mixed injection (COMI) was proposed and demonstrated great application potentiality in reducing the dust production in EAF steelmaking. In the present study, based on the eddy dissipation concept model, a computational fluid dynamics model of coherent jets with COMI was built with the overall and detailed chemical kinetic mechanisms (GRI-Mech 3.0). Compared with one-step combustion reaction, GRI-Mech 3.0 consists of 325 elementary reactions with 53 components and can predict more accurate results. The numerical simulation results were validated by the combustion experiment data. The jet behavior and the fluid flow characteristics of coherent jets with COMI under 298 K and 1700 K (25 °C and 1427 °C) were studied and the results showed that for coherent jets with COMI, the chemical effect of CO2 significantly weakened the shrouding combustion reactions of CH4 and the relative importance of the chemical effect of CO2 increases with CO2 concentration increasing. The potential core length of coherent jet decreases with the volume fraction of CO2 increasing. Moreover, it also can be found that the potential core length of coherent jets was prolonged with higher ambient temperature.

Study on the Fluid Flow Characteristics of Coherent Jets with CO2 and O2 Mixed Injection in Electric Arc Furnace Steelmaking Processes

NASA Astrophysics Data System (ADS)

Wei, Guangsheng; Zhu, Rong; Wu, Xuetao; Yang, Lingzhi; Dong, Kai; Cheng, Ting; Tang, Tianping

2018-03-01

As an efficient oxygen supplying technology, coherent jets are widely applied in electric arc furnace (EAF) steelmaking processes to strengthen chemical energy input, speed up smelting rhythm, and promote the uniformity of molten bath temperature and compositions. Recently, the coherent jet with CO2 and O2 mixed injection (COMI) was proposed and demonstrated great application potentiality in reducing the dust production in EAF steelmaking. In the present study, based on the eddy dissipation concept model, a computational fluid dynamics model of coherent jets with COMI was built with the overall and detailed chemical kinetic mechanisms (GRI-Mech 3.0). Compared with one-step combustion reaction, GRI-Mech 3.0 consists of 325 elementary reactions with 53 components and can predict more accurate results. The numerical simulation results were validated by the combustion experiment data. The jet behavior and the fluid flow characteristics of coherent jets with COMI under 298 K and 1700 K (25 °C and 1427 °C) were studied and the results showed that for coherent jets with COMI, the chemical effect of CO2 significantly weakened the shrouding combustion reactions of CH4 and the relative importance of the chemical effect of CO2 increases with CO2 concentration increasing. The potential core length of coherent jet decreases with the volume fraction of CO2 increasing. Moreover, it also can be found that the potential core length of coherent jets was prolonged with higher ambient temperature.

Extinct Radioactivities and the R-Process Jet

NASA Technical Reports Server (NTRS)

Cameron, A. G. W.

2001-01-01

All extinct radioactive species in the solar nebula were injected from a core-collapse supernova. I discuss primarily the products expected from an r-process jet in this supernova, and various supporting astrophysical observations. Additional information is contained in the original extended abstract.

Elliptic nozzle aspect ratio effect on controlled jet propagation

NASA Astrophysics Data System (ADS)

Aravindh Kumar, S. M.; Rathakrishnan, Ethirajan

2017-04-01

The present study deals with the control of a Mach 2 elliptic jet from a convergent-divergent elliptic nozzle of aspect ratio 4 using tabs at the nozzle exit. The experiments were carried out for rectangular and triangular tabs of the same blockage, placed along the major and minor axes of the nozzle exit, at different levels of nozzle expansion. The triangular tabs along the minor axis promoted superior mixing compared to the other controlled jets and caused substantial core length reduction at all the nozzle pressure ratios studied. The rectangular tabs along the minor axis caused core length reduction at all pressure ratios, but the values were minimal compared to that of triangular tabs along the minor axis. For all the test conditions, the mixing promotion caused by tabs along the major axis was inferior to that of tabs along the minor axis. The waves present in the core of controlled jets were visualized using a shadowgraph. Comparison of the present results with the results of a controlled Mach 2 elliptic jet of aspect ratio 2 (Aravindh Kumar and Sathakrishnan 2016 J. Propulsion Power 32 121-33, Aravindh Kumar and Rathakrishnan 2016 J. Aerospace Eng. at press (doi:10.1177/0954410016652921)) show that for all levels of expansion, the mixing effectiveness of triangular tabs along the minor axis of an aspect ratio 4 nozzle is better than rectangular or triangular tabs along the minor axis of an aspect ratio 2 nozzle.

Study on micro-bend light transmission performance of novel liquid-core optical fiber

NASA Astrophysics Data System (ADS)

Ma, Junyan; Zhao, Zhimin; Wang, Kaisheng; Guo, Linfeng

2007-01-01

With the increasing development of material technology and electronic integration technology, optical fiber and its using in smart structure have become hot in the field of material research. And liquid-core optical fiber is a special kind of optical fiber, which is made using liquid material as core and polymer material as optical layer and protective covering, and it has the characteristics of large core diameter, high numerical aperture, large-scope and efficient spectrum transmission and long life for using. So the liquid-core optical fiber is very suitable for spectrum cure, ultraviolet solidification, fluorescence detection, criminal investigation and evidence obtainment, etc, and especially as light transfer element in some new structures for the measurement of some signals, such as concentration, voltage, temperature, light intensity and so on. In this paper, the novel liquid-core optical fiber is self-made, and then through the test of its light transmission performance in free state, the relation between axial micro-bend and light-intensity loss are presented. When the liquid-core optical fiber is micro-bent axially, along with the axial displacement's increase, output power of light is reducing increasingly, and approximately has linear relation to micro-displacement in a range. According to the results liquid-core fiber-optic micro-bend sensor can be designed to measure micro-displacement of the tested objects. Experimental data and analysis provide experimental basis for further application of liquid-core optical fiber.

Acoustic Investigation of Jet Mixing Noise in Dual Stream Nozzles

NASA Technical Reports Server (NTRS)

Khavaran, Abbas; Dahl, Milo D.

2012-01-01

In an earlier study, a prediction model for jet noise in dual stream jets was proposed that is founded on velocity scaling laws in single stream jets and similarity features of the mean velocity and turbulent kinetic energy in dual stream flows. The model forms a composite spectrum from four component single-stream jets each believed to represent noise-generation from a distinct region in the actual flow. While the methodology worked effectively at conditions considered earlier, recent examination of acoustic data at some unconventional conditions indicate that further improvements are necessary in order to expand the range of applicability of the model. The present work demonstrates how these predictions compare with experimental data gathered by NASA and industry for the purpose of examining the aerodynamic and acoustic performance of such nozzles for a wide range of core and fan stream conditions. Of particular interest are jets with inverted velocity and temperature profiles and the appearance of a second spectral peak at small aft angles to the jet under such conditions. It is shown that a four-component spectrum succeeds in modeling the second peak when the aft angle refraction effects are properly incorporated into the model. A tradeoff of noise emission takes place between two turbulent regions identified as transition and fully mixed regions as the fan stream velocity exceeds that of the core stream. The effect of nozzle discharge coefficients will also be discussed.

Evolution of Photon and Particle Spectra in Compact, Luminous Objects

NASA Technical Reports Server (NTRS)

Eilek, Jean A.; Caroff, Lawrence J.

1995-01-01

Physical conditions in the radiating plasma in the cores of radio-strong quasars and active galactic nuclei cannot be derived from observations until the effects of relativistic aberration are understood. This requires determining both the bulk flow speeds and any wave or signal speed in the parsec-scale nuclear jets. In this project we studied several aspects of such waves. We considered constraints on jet deceleration by mass pickup, and found that bolometric luminosities of the active nuclei cannot constrain core jet speeds usefully. We also simulated observations of ballistic, helical trajectories and helical waves moving directly outwards along the jet. We found that ballistic trajectories are not allowed by the data; the helical features seen are very likely to be helical waves. We believe these are waves propagating in the jet plasma. To this end, we studied waves propagating in relativistic pair plasma jets. In particular, we undertook a program whose goal was to determine the nature of waves which can propagate in relativistic pair plasmas, and how such waves propagating in streaming jet plasma would be observed by an external observer. We developed the possibility of using pulsars as test cases for our models; this takes advantage of new technology in pulsar observations, and the similarity of the physical conditions in the pulsar magnetosphere to the dense, relativistic pair plasmas which exist in radio-strong quasars.

Designing solution-processable air-stable liquid crystalline crosslinkable semiconductors.

PubMed

McCulloch, Iain; Bailey, Clare; Genevicius, Kristijonas; Heeney, Martin; Shkunov, Maxim; Sparrowe, David; Tierney, Steven; Zhang, Weimin; Baldwin, Rodney; Kreouzis, Theo; Andreasen, Jens W; Breiby, Dag W; Nielsen, Martin M

2006-10-15

Organic electronics technology, in which at least the semiconducting component of the integrated circuit is an organic material, offers the potential for fabrication of electronic products by low-cost printing technologies, such as ink jet, gravure offset lithography and flexography. The products will typically be of lower performance than those using the present state of the art single crystal or polysilicon transistors, but comparable to amorphous silicon. A range of prototypes are under development, including rollable electrophoretic displays, active matrix liquid crystal (LC) displays, flexible organic light emitting diode displays, low frequency radio frequency identification tag and other low performance electronics. Organic semiconductors that offer both electrical performance and stability with respect to storage and operation under ambient conditions are required. This work describes the development of reactive mesogen semiconductors, which form large crosslinked LC domains on polymerization within mesophases. These crosslinked domains offer mechanical stability and are inert to solvent exposure in further processing steps. Reactive mesogens containing conjugated aromatic cores, designed to facilitate charge transport and provide good oxidative stability, were prepared and their liquid crystalline properties evaluated. The organization and alignment of the mesogens, both before and after crosslinking, were probed by grazing incidence wide-angle X-ray scattering of thin films. Both time-of-flight and field effect transistor devices were prepared and their electrical characterization reported.

Water entry of cylindrical bodies with various aspect ratios

NASA Astrophysics Data System (ADS)

Kim, Nayoung; Park, Hyungmin

2017-11-01

We experimentally investigate the water entry of cylindrical bodies with different aspect ratio (1.0-8.0), focusing on the deformation of free surface and resulting phenomena over and under the surface. The experiment is performed using a high-speed imaging (upto 10000 fps) and PIV. The head and tail of bodies are hemispherical and the nose part is additionally roughened with a sandpaper to see the effect of roughness as well. The release height is also adjusted to change the impact velocity at the free surface (Reynolds number is order of 105). For smooth surface (without cavity formation), a thin liquid film rises up the body after impacting, gathers at the pole and forms a jet over the free surfaces. The jet is created in the form of a thick and thin jet. The thin jet is produced by a water film riding up the surface of an object, and a thick jet is produced by rising water from underwater as the object sinks. However, as the aspect ratio increases, the liquid film does not fully ride up the body and cannot close, so there is an empty space below the free surface. With roughness (with cavity), the liquid film is detached from the body and splash/dome is formed above the free surface. The splash height and its collapsing time decrease with increasing the aspect ratio. Supported by Grants (MPSS-CG-2016-02, NRF-2017R1A4A1015523) of the Korea government.

Revision of Bubble Bursting: Universal Scaling Laws of Top Jet Drop Size and Speed.

PubMed

Gañán-Calvo, Alfonso M

2017-11-17

The collapse of a bubble of radius R_{o} at the surface of a liquid generating a liquid jet and a subsequent first drop of radius R is universally scaled using the Ohnesorge number Oh=μ/(ρσR_{o})^{1/2} and a critical value Oh^{*} below which no droplet is ejected; ρ, σ, and μ are the liquid density, surface tension, and viscosity, respectively. First, a flow field analysis at ejection yields the scaling of R with the jet velocity V as R/l_{μ}∼(V/V_{μ})^{-5/3}, where l_{μ}=μ^{2}/(ρσ) and V_{μ}=σ/μ. This resolves the scaling problem of curvature reversal, a prelude to jet formation. In addition, the energy necessary for the ejection of a jet with a volume and averaged velocity proportional to R_{o}R^{2} and V, respectively, comes from the energy excess from the total available surface energy, proportional to σR_{o}^{2}, minus the one dissipated by viscosity, proportional to μ(σR_{o}^{3}/ρ)^{1/2}. Using the scaling variable φ=(Oh^{*}-Oh)Oh^{-2}, it yields V/V_{μ}=k_{v}φ^{-3/4} and R/l_{μ}=k_{d}φ^{5/4}, which collapse published data since 1954 and resolve the scaling of R and V with k_{v}=16, k_{d}=0.6, and Oh^{*}=0.043 when gravity effects are negligible.

Disc-jet Coupling in the 2009 Outburst of the Black Hole Candidate H1743-322

NASA Technical Reports Server (NTRS)

Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; Coriat, M.; Corbel, S.; Dhawan, V.; Krimm, H. A.; Remillard, R. A.; Rupen, M. P.; Russell, D. M.;

Binary system and jet precession and expansion in G35.20-0.74N

NASA Astrophysics Data System (ADS)

Beltrán, M. T.; Cesaroni, R.; Moscadelli, L.; Sánchez-Monge, Á.; Hirota, T.; Kumar, M. S. N.

2016-09-01

Context. Atacama Large Millimeter/submillimeter Array (ALMA) observations of the high-mass star-forming region G35.20-0.74N have revealed the presence of a Keplerian disk in core B rotating about a massive object of 18 M⊙, as computed from the velocity field. The luminosity of such a massive star would be comparable to (or higher than) the luminosity of the whole star-forming region. To solve this problem it has been proposed that core B could harbor a binary system. This could also explain the possible precession of the radio jet associated with this core, which has been suggested by its S-shaped morphology. Aims: We establish the origin of the free-free emission from core B and investigate the existence of a binary system at the center of this massive core and the possible precession of the radio jet. Methods: We carried out VLA continuum observations of G35.20-0.74N at 2 cm in the B configuration and at 1.3 cm and 7 mm in the A and B configurations. The bandwidth at 7 mm covers the CH3OH maser line at 44.069 GHz. Continuum images at 6 and 3.6 cm in the A configuration were obtained from the VLA archive. We also carried out VERA observations of the H2O maser line at 22.235 GHz. Results: The observations have revealed the presence of a binary system of UC/HC Hii regions at the geometrical center of the radio jet in G35.20-0.74N. This binary system, which is associated with a Keplerian rotating disk, consists of two B-type stars of 11 and 6 M⊙. The S-shaped morphology of the radio jet has been successfully explained as being due to precession produced by the binary system. The analysis of the precession of the radio jet has allowed us to better interpret the IR emission in the region, which would be not tracing a wide-angle cavity open by a single outflow with a position angle of ~55°, but two different flows: a precessing one in the NE-SW direction associated with the radio jet, and a second one in an almost E-W direction. Comparison of the radio jet images obtained at different epochs suggests that the jet is expanding at a maximum speed on the plane of the sky of 300 km s-1. The proper motions of the H2O maser spots measured in the region also indicate expansion in a direction similar to that of the radio jet. Conclusions: We have revealed a binary system of high-mass young stellar objects embedded in the rotating disk in G35.20-0.74N. The presence of a massive binary system is in agreement with the theoretical predictions of high-mass star formation, according to which the gravitational instabilities during the collapse would produce the fragmentation of the disk and the formation of such a system. For the first time, we have detected a high-mass young star associated with an UC/HC Hii region and at the same time powering a radio jet. The reduced images (FITS files) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A49

Molecular recognition in chiral smectic liquid crystals: the effect of core-core interactions and chirality transfer on polar order.

PubMed

Lemieux, Robert P

2007-12-01

This critical review focuses on the induction of polar order in smectic liquid crystal phases by dopants with axially chiral cores, and should be of interest to all practitioners of supramolecular chemistry. The variations in polarization power of these dopants with the core structure of the liquid crystal hosts is a manifestation of molecular recognition that reflects the nanosegregation of aromatic cores from paraffinic side-chains in smectic phases, and the collective effect of core-core interactions that enable the propagation of chiral perturbations.

VLBI OBSERVATIONS OF THE JET IN M 87 DURING THE VERY HIGH ENERGY {gamma}-RAY FLARE IN 2010 APRIL

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

Hada, Kazuhiro; Giroletti, Marcello; Giovannini, Gabriele

2012-11-20

We report on the detailed radio status of the M 87 jet during the very high energy (VHE) {gamma}-ray flaring event in 2010 April, obtained from high-resolution, multi-frequency, phase-referencing Very Long Baseline Array observations. We especially focus on the properties of the jet base (the radio core) and the peculiar knot HST-1, which are currently favored as the {gamma}-ray emitting sites. During the VHE flaring event, the HST-1 region remains stable in terms of its structure and flux density in the optically thin regime above 2 GHz, being consistent with no signs of enhanced activities reported at X-ray for thismore » feature. The radio core shows an inverted spectrum at least up to 43 GHz during this event. Astrometry of the core position, which is specified as {approx}20 R {sub s} from the central engine in our previous study, shows that the core position is stable on a level of 4 R {sub s}. The core at 43 and 22 GHz tends to show slightly ({approx}10%) higher flux level near the date of the VHE flux peak compared with the epochs before/after the event. The size of the 43 GHz core is estimated to be {approx}17 R {sub s}, which is close to the size of the emitting region suggested from the observed timescale of rapid variability at VHE. These results tend to favor the scenario that the VHE {gamma}-ray flare in 2010 April is associated with the radio core.« less

The Most Compact Bright Radio-loud AGNs. II. VLBA Observations of 10 Sources at 43 and 86 GHz

NASA Astrophysics Data System (ADS)

Cheng, X.-P.; An, T.; Hong, X.-Y.; Yang, J.; Mohan, P.; Kellermann, K. I.; Lister, M. L.; Frey, S.; Zhao, W.; Zhang, Z.-L.; Wu, X.-C.; Li, X.-F.; Zhang, Y.-K.

2018-01-01

Radio-loud active galactic nuclei (AGNs), hosting powerful relativistic jet outflows, provide an excellent laboratory for studying jet physics. Very long baseline interferometry (VLBI) enables high-resolution imaging on milli-arcsecond (mas) and sub-mas scales, making it a powerful tool to explore the inner jet structure, shedding light on the formation, acceleration, and collimation of AGN jets. In this paper, we present Very Long Baseline Array observations of 10 radio-loud AGNs at 43 and 86 GHz that were selected from the Planck catalog of compact sources and are among the brightest in published VLBI images at and below 15 GHz. The image noise levels in our observations are typically 0.3 and 1.5 mJy beam‑1 at 43 and 86 GHz, respectively. Compared with the VLBI data observed at lower frequencies from the literature, our observations with higher resolutions (with the highest resolution being up to 0.07 mas at 86 GHz and 0.18 mas at 43 GHz) and at higher frequencies detected new jet components at sub-parsec scales, offering valuable data for studies of the physical properties of the innermost jets. These include the compactness factor of the radio structure (the ratio of core flux density to total flux density), and core brightness temperature ({T}{{b}}). In all these sources, the compact core accounts for a significant fraction (> 60 % ) of the total flux density. Their correlated flux density at the longest baselines is higher than 0.16 Jy. The compactness of these sources make them good phase calibrators of millimeter-wavelength ground-based and space VLBI.

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

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

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

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 weremore » 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.« less

Acoustics and Trust of Separate-Flow Exhaust Nozzles With Mixing Devices for High-Bypass-Ratio Engines

NASA Technical Reports Server (NTRS)

Saiyed, Naseem H.; Mikkelsen, Kevin L.; Bridges, James E.

2000-01-01

The NASA Glenn Research Center recently completed an experimental study to reduce the jet noise from modern turbofan engines. The study concentrated on exhaust nozzle designs for high-bypass-ratio engines. These designs modified the core and fan nozzles individually and simultaneously. Several designs provided an ideal jet noise reduction of over 2.5 EPNdB for the effective perceived noise level (EPNL) metric. Noise data, after correcting for takeoff thrust losses, indicated over a 2.0-EPNdB reduction for nine designs. Individually modifying the fan nozzle did not provide attractive EPNL reductions. Designs in which only the core nozzle was modified provided greater EPNL reductions. Designs in which core and fan nozzles were modified simultaneously provided the greatest EPNL reduction. The best nozzle design had a 2.7-EPNdB reduction (corrected for takeoff thrust loss) with a 0.06-point cruise thrust loss. This design simultaneously employed chevrons on the core and fan nozzles. In comparison with chevrons, tabs appeared to be an inefficient method for reducing jet noise. Data trends indicate that the sum of the thrust losses from individually modifying core and fan nozzles did not generally equal the thrust loss from modifying them simultaneously. Flow blockage from tabs did not scale directly with cruise thrust loss and the interaction between fan flow and the core nozzle seemed to strongly affect noise and cruise performance. Finally, the nozzle configuration candidates for full-scale engine demonstrations are identified.

Highly Sensitive Liquid Core Temperature Sensor Based on Multimode Interference Effects

PubMed Central

Fuentes-Fuentes, Miguel A.; May-Arrioja, Daniel A.; Guzman-Sepulveda, José R.; Torres-Cisneros, Miguel; Sánchez-Mondragón, José J.

2015-01-01

A novel fiber optic temperature sensor based on a liquid-core multimode interference device is demonstrated. The advantage of such structure is that the thermo-optic coefficient (TOC) of the liquid is at least one order of magnitude larger than that of silica and this, combined with the fact that the TOC of silica and the liquid have opposite signs, provides a liquid-core multimode fiber (MMF) highly sensitive to temperature. Since the refractive index of the liquid can be easily modified, this allows us to control the modal properties of the liquid-core MMF at will and the sensor sensitivity can be easily tuned by selecting the refractive index of the liquid in the core of the device. The maximum sensitivity measured in our experiments is 20 nm/°C in the low-temperature regime up to 60 °C. To the best of our knowledge, to date, this is the largest sensitivity reported for fiber-based MMI temperature sensors. PMID:26512664

The high-resolution structure of the Centaurus A nucleus at 2.3 and 8.4 GHz

NASA Technical Reports Server (NTRS)

Meier, David L.; Preston, Robert A.; Morabito, David D.; Skjerve, Lyle; Slade, Martin A.; Wehrle, Ann E.; Niell, Arthur E.; Jauncey, David L.; Batchelor, Robert; Tzioumis, Anastasios K.

1989-01-01

VLBI observations of the nucleus of Centaurus A have been made at two frequencies with an array of five Australian radio telescopes as part of the Southern Hemisphere VLBI Experiment. Observations were made at 2.3 GHz with all five antennas, while only two were employed at 8.4 GHz. At 2.3 GHz seven tracks in the (u,v) plane with coverage of 6-8 hr each were obtained, yielding significant information on the structure of the nuclear jet. At 8.4 GHz a compact unresolved core was detected as well. It is found that the source consists of the compact self-absorbed core, a jet containing a set of three knots extending from 100 to 160 mas from the core, and a very long, narrow component elongated along the same position angle as the knots. The allowable range for the position angle of the jet is 51 + or - 3 deg, in agreement with that of the radio and X-ray structure on arcsecond and arcminute scales. The jet has brightened at 2.3 GHz by about 4 Jy, a factor of nearly 3, since the early 1970s, 1.8 Jy of which has occurred in the last 2 yr with no discernable changes in structure.

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.

Liquid injection plasma deposition method and apparatus

DOEpatents

Kong, Peter C.; Watkins, Arthur D.

1999-01-01

A liquid injection plasma torch deposition apparatus for depositing material onto a surface of a substrate may comprise a plasma torch for producing a jet of plasma from an outlet nozzle. A plasma confinement tube having an inlet end and an outlet end and a central bore therethrough is aligned with the outlet nozzle of the plasma torch so that the plasma jet is directed into the inlet end of the plasma confinement tube and emerges from the outlet end of the plasma confinement tube. The plasma confinement tube also includes an injection port transverse to the central bore. A liquid injection device connected to the injection port of the plasma confinement tube injects a liquid reactant mixture containing the material to be deposited onto the surface of the substrate through the injection port and into the central bore of the plasma confinement tube.

Simultaneous PLIF and PIV measurement of a near field turbulent immiscible buoyant oil jet fragmentation in water using liquid-liquid refractive index matching

NASA Astrophysics Data System (ADS)

Xue, Xinzhi; Katz, Joseph

2017-11-01

Very little experimental data exits on the flow structure in the near field of a crude oil jet fragmenting in water because of inability to probe dense droplet cloud. Refractive index-matching is applied to overcome this challenge by using silicone oil and sugar water as a surrogate liquid pair. Their density ratio, viscosity ratio, and interfacial tension are closely matched with those of crude oil and seawater. Simultaneous PLIF and PIV measurements are conducted by fluorescently tagging the oil and seeding both phases with particles. With increasing jet Reynolds and Weber numbers, the oil plume breakup occurs closer to the nozzle, the spreading angle of the jet increases, and the droplet sizes decrease. The varying spread rate is attributed to differences in droplet size distributions. The location of primary oil breakup is consistent with the region of high strain rate fluctuations. What one may perceive as oil droplets in opaque fluids actually consists of multi-layers containing water droplets, which sometimes encapsulate smaller oil droplets, creating a ``Russian Doll'' like phenomenon. This system forms as ligaments of oil and water wrap around each other during entrainment. Results include profiles of mean velocity and turbulence parameters along with energy spectra. Gulf of Mexico Research Inititave.

Water Footprint and Land Requirement of Solar Thermochemical Jet-Fuel Production.

PubMed

Falter, Christoph; Pitz-Paal, Robert

2017-11-07

The production of alternative fuels via the solar thermochemical pathway has the potential to provide supply security and to significantly reduce greenhouse gas emissions. H 2 O and CO 2 are converted to liquid hydrocarbon fuels using concentrated solar energy mediated by redox reactions of a metal oxide. Because attractive production locations are in arid regions, the water footprint and the land requirement of this fuel production pathway are analyzed. The water footprint consists of 7.4 liters per liter of jet fuel of direct demand on-site and 42.4 liters per liter of jet fuel of indirect demand, where the dominant contributions are the mining of the rare earth oxide ceria, the manufacturing of the solar concentration infrastructure, and the cleaning of the mirrors. The area-specific productivity is found to be 33 362 liters per hectare per year of jet fuel equivalents, where the land coverage is mainly due to the concentration of solar energy for heat and electricity. The water footprint and the land requirement of the solar thermochemical fuel pathway are larger than the best power-to-liquid pathways but an order of magnitude lower than the best biomass-to-liquid pathways. For the production of solar thermochemical fuels arid regions are best-suited, and for biofuels regions of a moderate and humid climate.

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

Nandwana, Peeyush; Elliott, Amy M.; Siddel, Derek

Traditional manufacturing of Inconel 718 components from castings and thermomechanical processing routes involve extensive post processing and machining to attain the desired geometry. Additive manufacturing (AM) technologies including direct energy deposition (DED), selective laser melting (SLM), electron beam melting (EBM) and binder jet 3D printing (BJ3DP) can minimize scrap generation and reduce lead times. While there is extensive literature on the use of melting and solidification based AM technologies, there has been limited research on the use of binder jet 3D printing. In this paper, a brief review on binder jet additive manufacturing of Inconel 718 is presented. In addition,more » existing knowledge on sintering of Inconel 718 has been extended to binder jet 3D printing. We found that supersolidus liquid phase sintering (SLPS) is necessary to achieve full densification of Inconel 718. SLPS is sensitive to the feedstock chemistry that has a strong influence on the liquid volume fraction at the processing temperature. Based on these results, we discuss an empirical framework to determine the role of powder particle size and liquid volume fraction on sintering kinetics. In conclusion, the role of powder packing factor and binder saturation on microstructural evolution is discussed. The current challenges in the use of BJ3DP for fabrication of Inconel 718, as well as, extension to other metal systems, are presented.« less

Pinching Solutions of Slender Cylindrical Jets

DTIC Science & Technology

1993-06-01

NASA Langley Research Center, Hampton, VA 23681.2This research was supported in part by Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDE...concentrate on inviscid irrotational flows of liquid jets. A review article has been written by Bogy [2]. Of relevance is also the work of Chandrasekhar...equations become elliptic and allow the possibility of admissible pinching solutions described in this article . It is interesting to find that for jets

Endoscope system with plasma flushing and coaxial round jet nozzle for off-pump cardiac surgery.

PubMed

Horiuchi, Tetsuya; Masamune, Ken; Iwase, Yuki; Ymashita, Hiromasa; Tsukihara, Hiroyuki; Motomura, Noboru; Ohta, Yuji; Dohi, Takeyoshi

2011-07-01

To develop a new endoscope for performing simple surgical tasks inside the blood-filled cardiac atrium/chamber, that is, "off-pump" cardiac surgeries. We developed the endoscope system with plasma flushing and coaxial round jet nozzle. The "plasma flushing" system was invented to observe the interior of the blood-filled heart by displacing blood cells in front of the endoscope tip. However, some areas could not be observed with simple flushing of the liquid because the flushed liquid mixed with blood. Further, a large amount of liquid had to be flushed, which posed a risk of cardiac damage caused by excess volume. Therefore, to safely capture high-resolution images of the interior of the heart, an endoscope with a coaxial round jet nozzle through which plasma is flushed has been developed. And to reduce the volume of flushed liquid, the synchronization system of heartbeat and the endoscope system with plasma flushing has been developed. We conducted an in vivo experiment to determine whether we could observe intracardiac tissues in swine without the use of a heart-lung machine. As a result, we successfully observed intracardiac tissues without using a heart-lung machine. By using a coaxial nozzle, we could even observe the tricuspid valve. Moreover, we were able to save up to 30% of the flushed liquid by replacing the original system with a synchronization system. And we evaluated the performance of the endoscope with the coaxial round jet nozzle by conducting fluid analysis and an in vitro experiment. We successfully observed intracardiac tissues without using a heart-lung machine. By using a coaxial nozzle, we could even observe the tricuspid valve. And by replacing an original system to a synchronization system, we were able to save up to 30% of the flushed liquid. As a follow-up study, we plan to create a surgical flexible device for valve disease that can grasp, staple, and repair cardiac valves by endoscopic visualization.

Turbulence Measurements of Separate Flow Nozzles with Mixing Enhancement Features

NASA Technical Reports Server (NTRS)

Bridges, James; Wernet, Mark P.

2002-01-01

Comparison of turbulence data taken in three separate flow nozzles, two with mixing enhancement features on their core nozzle, shows how the mixing enhancement features modify turbulence to reduce jet noise. The three nozzles measured were the baseline axisymmetric nozzle 3BB, the alternating chevron nozzle, 3A12B, with 6-fold symmetry, and the flipper tab nozzle 3T24B also with 6-fold symmetry. The data presented show the differences in turbulence characteristics produced by the geometric differences in the nozzles, with emphasis on those characteristics of interest in jet noise. Among the significant findings: the enhanced mixing devices reduce turbulence in the jet mixing region while increasing it in the fan/core shear layer, the ratios of turbulence components are significantly altered by the mixing devices, and the integral lengthscales do not conform to any turbulence model yet proposed. These findings should provide guidance for modeling the statistical properties of turbulence to improve jet noise prediction.

Artificial plasma jet in the ionosphere

NASA Astrophysics Data System (ADS)

Haerendel, G.; Sagdeev, R. Z.

The dynamics of an artificially injected plasma beam in the near-earth space are analyzed in terms of the beam structure, its propagation across the magnetic field, and the resulting wave phenomena (Porcupine Project, flight 4, March 31, 1979). Out of the four ejectable canisters attached to the main payload, two were instrumented by the U.S., one by the USSR (the Xenon plasma beam experiment), and one by West Germany (carrying a barium ion jet experiment). The propagation of the plasma seems to occur in three stages, with high-frequency broad-band oscillations mainly localized in the 'core' of the jet, while low-frequency oscillations were spatially separated from it. The generation region of LF oscillations was found to be much wider than the jet core. As a result of the interaction between the plasma beam and the ambient medium a heating of electrons, up to energies of about 20 eV, associated with LF noise was observed. The behavior of high-energy ions and the observed HF wave phenomena need further analysis.

Cavitation studies in microgravity

NASA Astrophysics Data System (ADS)

Kobel, Philippe; Obreschkow, Danail; Farhat, Mohamed; Dorsaz, Nicolas; de Bosset, Aurele

The hydrodynamic cavitation phenomenon is a major source of erosion for many industrial systems such as cryogenic pumps for rocket propulsion, fast ship propellers, hydraulic pipelines and turbines. Erosive processes are associated with liquid jets and shockwaves emission fol-lowing the cavity collapse. Yet, fundamental understanding of these processes requires further cavitation studies inside various geometries of liquid volumes, as the bubble dynamics strongly depends the surrounding pressure field. To this end, microgravity represents a unique platform to produce spherical fluid geometries and remove the hydrostatic pressure gradient induced by gravity. The goal of our first experiment (flown on ESA's parabolic flight campaigns 2005 and 2006) was to study single bubble dynamics inside large spherical water drops (having a radius between 8 and 13 mm) produced in microgravity. The water drops were created by a micro-pump that smoothly expelled the liquid through a custom-designed injector tube. Then, the cavitation bubble was generated through a fast electrical discharge between two electrodes immersed in the liquid from above. High-speed imaging allowed to analyze the implications of isolated finite volumes and spherical free surfaces on bubble evolution, liquid jets formation and shock wave dynamics. Of particular interest are the following results: (A) Bubble lifetimes are shorter than in extended liquid volumes, which could be explain by deriving novel corrective terms to the Rayleigh-Plesset equation. (B) Transient crowds of micro-bubbles (smaller than 1mm) appeared at the instants of shockwaves emission. A comparison between high-speed visualizations and 3D N-particle simulations of a shock front inside a liquid sphere reveals that focus zones within the drop lead to a significantly increased density of induced cavitation. Considering shock wave crossing and focusing may hence prove crucially useful to understand the important process of cavitation erosion. The aim of our future microgravity experiment is to assess the direct effects of gravity on cavitation bubble collapse through a comparison of single cavitation bubbles collapsing in mi-crogravity, normal gravity, and hypergravity. In particular, we shall investigate the shape of the bubble in its final collapse stage and the amount of energy dissipated in the dominant collapse channels, such as liquid jet, shock wave, and rebound bubble. The highly spherical bubbles will be produced via a point-like plasma generated by a high power laser beam. One major hypothesis that we will test is an increase in shock wave energy with decreasing gravity as a consequence of the higher final sphericity and suppression of liquid jets. To support this, we introduce an analytical model for the gravity-perturbed asymmetric collapse of spherical bubbles, and demonstrate that all initially spherical bubbles develop a gravity-related vertical jet along their collapse.

Measurement of surface shear stress vector beneath high-speed jet flow using liquid crystal coating

NASA Astrophysics Data System (ADS)

Wang, Cheng-Peng; Zhao, Ji-Song; Jiao, Yun; Cheng, Ke-Ming

2018-05-01

The shear-sensitive liquid crystal coating (SSLCC) technique is investigated in the high-speed jet flow of a micro-wind-tunnel. An approach to measure surface shear stress vector distribution using the SSLCC technique is established, where six synchronous cameras are used to record the coating color at different circumferential view angles. Spatial wall shear stress vector distributions on the test surface are obtained at different velocities. The results are encouraging and demonstrate the great potential of the SSLCC technique in high-speed wind-tunnel measurement.

Liquid lithium target as a high intensity, high energy neutron source

DOEpatents

Parkin, Don M.; Dudey, Norman D.

1976-01-01

This invention provides a target jet for charged particles. In one embodiment the charged particles are high energy deuterons that bombard the target jet to produce high intensity, high energy neutrons. To this end, deuterons in a vacuum container bombard an endlessly circulating, free-falling, sheet-shaped, copiously flowing, liquid lithium jet that gushes by gravity from a rectangular cross-section vent on the inside of the container means to form a moving web in contact with the inside wall of the vacuum container. The neutrons are produced via break-up of the beam in the target by stripping, spallation and compound nuclear reactions in which the projectiles (deuterons) interact with the target (Li) to produce excited nuclei, which then "boil off" or evaporate a neutron.

High-Fidelity Simulations of Electrically-Charged Atomizing Diesel-Type Jets

NASA Astrophysics Data System (ADS)

Gaillard, Benoit; Owkes, Mark; van Poppel, Bret

2015-11-01

Combustion of liquid fuels accounts for over a third of the energy usage today. Improving efficiency of combustion systems is critical to meet the energy needs while limiting environmental impacts. Additionally, a shift away from traditional fossil fuels to bio-derived alternatives requires fuel injection systems that can atomize fuels with a wide range of properties. In this work, the potential benefits of electrically-charged atomization is investigated using numerical simulations. Particularly, the electrostatic forces on the hydrodynamic jet are quantified and the impact of the forces is analyzed by comparing simulations of Diesel-type jets at realistic flow conditions. The simulations are performed using a state-of-the-art numerical framework that globally conserves mass, momentum, and the electric charge density even at the gas-liquid interface where discontinuities exist.

Analysis and Modeling of a Two-Phase Jet Pump of a Flow Boiling Test Facility for Aerospace Applications

NASA Technical Reports Server (NTRS)

Sherif, S. A.; Steadham, Justin M.

1996-01-01

Jet pumps are devices capable of pumping fluids to a higher pressure employing a nozzle/diffuser/mixing chamber combination. A primary fluid is usually allowed to pass through a converging-diverging nozzle where it can accelerate to supersonic speeds at the nozzle exit. The relatively high kinetic energy that the primary fluid possesses at the nozzle exit is accompanied by a low pressure region in order to satisfy Bernoulli's equation. The low pressure region downstream of the nozzle exit permits a secondary fluid to be entrained into and mixed with the primary fluid in a mixing chamber located downstream of the nozzle. Several combinations may exist in terms of the nature of the primary and secondary fluids in so far as whether they are single or two-phase fluids. Depending on this, the jet pump may be classified as gas/gas, gas/liquid, liquid/liquid, two-phase/liquid, or similar combinations. The mixing chamber serves to create a homogeneous single-phase or two-phase mixture which enters a diffuser where the high kinetic energy of the fluid is converted into pressure energy. If the fluid mixture entering the diffuser is in the supersonic flow regime, a normal shock wave usually develops inside the diffuser. If the fluid mixture is one that can easily change phase, a condensation shock would normally develop. Because of the overall rise in pressure in the diffuser as well as the additional rise in pressure across the shock layer, condensation becomes more likely. Associated with the pressure rise across the shock is a velocity reduction from the supersonic to the subsonic range. If the two-phase flow entering the diffuser is predominantly gaseous with liquid droplets suspended in it, it will transform into a predominantly liquid flow containing gaseous bubbles (bubbly flow) somewhere in the diffuser. While past researchers have been able to model the two-phase flow jet pump using the one-dimensional assumption with no shock waves and no phase change, there is no research known to the authors apart from that of Anand (1992) which accounted for condensation shocks. One of the objectives of this research effort is to develop a comprehensive model in which the effects of phase slip and inter-phase heat transfer as well as the wall friction and shock waves are accounted for. While this modeling effort is predominantly analytical in nature and is primarily intended to provide a parametric understanding of the jet pump performance under different operating scenarios, another parallel effort employing a commercial CFD code is also implemented. The latter effort is primarily intended to model an axisymmetric counterpart of the problem in question. The viability of using the CFD code to model a two-phase flow jet pump will be assessed by attempting to recreate some of the existing performance data of similar jet pumps. The code will eventually be used to generate the jet pump performance characteristics of several scenarios involving jet pump geometries as well as flow regimes in order to be able to determine an optimum design which would be suitable for a two-phase flow boiling test facility at NASA-Marshall. Because of the extensive nature of the analytical model developed, the following section will only provide very brief highlights of it, while leaving the details to a more complete report submitted to the NASA colleague. This report will also contain some of the simulation results obtained using the CFD code.

AGN jets under the microscope: A divide? Doctoral Thesis Award Lecture 2011

NASA Astrophysics Data System (ADS)

Karouzos, M.; Britzen, S.; Witzel, A.; Zensus, A. J.; Eckart, A.

2012-06-01

A new paradigm for active galactic jet kinematics has emerged through detailed investigations of BL Lac objects using very long baseline radio interferometry. In this new scheme, most, if not all, jet components appear to remain stationary with respect to the core but show significant non-radial motions. This paper presents results from our kinematic investigation of the jets of a statistically complete sample of radio-loud flat-spectrum active galaxies, focusing on the comparison between the jet kinematic properties of BL Lacs and flat-spectrum radio-quasars. It is shown that there is a statistically significant difference between the kinematics of the two AGN classes, with BL Lacs showing more bent jets, that are wider and show slower movement along the jet axis, compared to flat-spectrum radio-quasars. This is interpreted as evidence for helically structured jets.

Quasi 1-D Analysis of a Circular, Compressible, Turbulent Jet Laden with Water Droplets. Appendix C

NASA Technical Reports Server (NTRS)

2001-01-01

Recent experimental studies indicate that presence of small amount of liquid droplets reduces the Overall Sound Pressure Level (OASPL) of a jet. Present study is aimed at numerically investigating the effect of liquid particles on the overall flow quantities of a heated, compressible round jet. The jet is assumed perfectly expanded. A quasi-1D model was developed for this purpose which uses area-averaged quantities that satisfy integral conservation equations. Special attention is given to represent the early development region since it is acoustically important. Approximate velocity and temperature profiles were assumed in this region to evaluate entrainment rate. Experimental correlations were used to obtain spreading rate of shear layer. The base flow thus obtained is then laden with water droplets at the exit of the nozzle. Mass, momentum and energy coupling between the two phases is represented using empirical relations. Droplet size and mass loading are varied to observe their effect on flow variables.

Cryogenic and Simulated Fuel Jet Breakup in Argon, Helium and Nitrogen Gas Flows

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1995-01-01

Two-phase flow atomization of liquid nitrogen jets was experimentally investigated. They were co-axially injected into high-velocity gas flows of helium, nitrogen and argon, respectively, and atomized internally inside a two-fluid fuel nozzle. Cryogenic sprays with relatively high specific surface areas were produced, i.e., ratios of surface area to volume were fairly high. This was indicated by values of reciprocal Sauter mean diameters, RSMD's, as measured with a scattered- light scanning instrument developed at NASA Lewis Research Center. Correlating expressions were derived for the three atomizing gases over a gas temperature range of 111 to 422 K. Also, the correlation was extended to include waterjet breakup data that had been previously obtained in simulating fuel jet breakup in sonic velocity gas flow. The final correlating expression included a new dimensionless molecular-scale acceleration group. It was needed to correlate RSMD data, for LN2 and H2O sprays, with the fluid properties of the liquid jets and atomizing gases used in this investigation.

Deformation and Breakup of a Stretching Liquid Bridge

NASA Astrophysics Data System (ADS)

Franses, Elias I.; Liao, Ying-Chih; Basaran, Osman

2004-11-01

Surfactants are routinely used to control the breakup of drops and jets in applications as diverse as ink jet printing, crop spraying, and microarraying. While highly accurate algorithms for studying the breakup of surfactant-free drops and jets are well documented and a great deal of information is now available in such situations, little is known about the closely related problem of interface rupture when surfactant effects cannot be neglected. Here we analyze the deformation and breakup of a stretching liquid bridge whose surface is covered with an insoluble surfactant monolayer by means of a two-dimensional (2-d) finite element algorithm using elliptic mesh generation. That the predictions made with the 2-d algorithm are faithful to the physics is confirmed by demonstrating that the computed results accord well with our new high-speed visualization experiments and existing scaling theories. Comparisons are also made to computations made with a one-dimensional (1-d) algorithm based on the slender-jet equations.

A Model for the Vortex Pair Associated with a Jet in a Cross Flow

NASA Technical Reports Server (NTRS)

Sellers, William L.

1975-01-01

A model is presented for the contrarotating vortex pair that is formed by a round, turbulent, subsonic jet directed normally into a uniform, subsonic cross flow. The model consists of a set of algebraic equations that describe the properties of the vortex pair as a function of their location in the jet plume. The parameters of the model are physical characteristics of the vortices such as the vortex strength, spacing, and core size. These parameters are determined by velocity measurements at selective points in the jet plume.

Radio Properties of the BAT AGNs: the FIR-radio Relation, the Fundamental Plane, and the Main Sequence of Star Formation

NASA Astrophysics Data System (ADS)

Smith, Krista Lynne; Mushotzky, Richard F.; Vogel, Stuart; Shimizu, Thomas T.; Miller, Neal

2016-12-01

We conducted 22 GHz 1″ JVLA imaging of 70 radio-quiet active galactic nuclei (AGNs) from the Swift-BAT survey. We find radio cores in all but three objects. The radio morphologies of the sample fall into three groups: compact and core-dominated, extended, and jet-like. We spatially decompose each image into core flux and extended flux, and compare the extended radio emission with that predicted from previous Herschel observations using the canonical FIR-radio relation. After removing the AGN contribution to the FIR and radio flux densities, we find that the relation holds remarkably well despite the potentially different star formation physics in the circumnuclear environment. We also compare our core radio flux densities with predictions of coronal models and scale-invariant jet models for the origin of radio emission in radio-quiet AGNs, and find general consistency with both models. However, we find that the L R/L X relation does not distinguish between star formation and non-relativistic AGN-driven outflows as the origin of radio emission in radio-quiet AGNs. Finally, we examine where objects with different radio morphologies fall in relation to the main sequence (MS) of star formation, and conclude that those AGNs that fall below the MS, as X-ray selected AGNs have been found to do, have core-dominated or jet-like 22 GHz morphologies.

A device for controlled jet injection of large volumes of liquid.

PubMed

Mckeage, James W; Ruddy, Bryan P; Nielsen, Poul M F; Taberner, Andrew J

2016-08-01

We present a needle-free jet injection device controllably actuated by a voice coil and capable of injecting up to 1.3 mL. This device is used to perform jet injections of ~900 μL into porcine tissue. This is the first time that delivery of such a large volume has been reported using an electronically controllable device. The controllability of this device is demonstrated with a series of ejections where the desired volume is ejected to within 1 % during an injection at a predetermined jet velocity.

Tomographic analysis of neutron and gamma pulse shape distributions from liquid scintillation detectors at Joint European Torus.

PubMed

Giacomelli, L; Conroy, S; Gorini, G; Horton, L; Murari, A; Popovichev, S; Syme, D B

2014-02-01

The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world devoted to nuclear fusion experiments of magnetic confined Deuterium (D)/Deuterium-Tritium (DT) plasmas. Neutrons produced in these plasmas are measured using various types of neutron detectors and spectrometers. Two of these instruments on JET make use of organic liquid scintillator detectors. The neutron emission profile monitor implements 19 liquid scintillation counters to detect the 2.45 MeV neutron emission from D plasmas. A new compact neutron spectrometer is operational at JET since 2010 to measure the neutron energy spectra from both D and DT plasmas. Liquid scintillation detectors are sensitive to both neutron and gamma radiation but give light responses of different decay time such that pulse shape discrimination techniques can be applied to identify the neutron contribution of interest from the data. The most common technique consists of integrating the radiation pulse shapes within different ranges of their rising and/or trailing edges. In this article, a step forward in this type of analysis is presented. The method applies a tomographic analysis of the 3-dimensional neutron and gamma pulse shape and pulse height distribution data obtained from liquid scintillation detectors such that n/γ discrimination can be improved to lower energies and additional information can be gained on neutron contributions to the gamma events and vice versa.

Mixing in Shear Coaxial Jets with and without Acoustics

DTIC Science & Technology

2012-03-29

Distribution Unlimited Combustion Instability Lab - Background • Combustion instability is an unsustainable growth of pressure and heat transfer ...beyond liquid, gas states. Shear coaxial injectors are a common choice for cryogenic liquid rocket engines. Interactions of transverse acoustics with...and combustion beyond liquid, gas states • Shear coaxial injectors are a common choice for cryogenic liquid rocket engines • Interactions of

Improved Root Normal Size Distributions for Liquid Atomization

DTIC Science & Technology

2015-11-01

Jackson, Primary Breakup of Round Aerated- Liquid Jets in Supersonic Crossflows, Atomization and Sprays, 16(6), 657-672, 2006 H. C. Simmons, The...Breakup in Liquid - Gas Mixing Layers, Atomization and Sprays, 1, 421-440, 1991 P.-K. Wu, L.-K. Tseng, and G. M. Faeth, Primary Breakup in Gas / Liquid ...Improved Root Normal Size Distributions for Liquid Atomization Distribution Statement A. Approved for public release; distribution is unlimited

America's first long-range-missile and space exploration program: The ORDCIT project of the Jet Propulsion Laboratory, 1943 - 1946: A memoir

NASA Technical Reports Server (NTRS)

Malina, F. J.

1977-01-01

Research and achievements of the wartime Jet Propulsion Laboratory are outlined. Accomplishments included development of the solid-propellant Private A and private R rockets and the liquid-propellant nitric acid-aniline WAC Corporal rocket.

An experimental study of multiple jet mixing

NASA Technical Reports Server (NTRS)

Krothapalli, D.; Baganoff, D.; Karamcheti, K.

1979-01-01

Measurements of an incompressible jet issuing from an array of rectangular lobes, equally spaced with their small dimensions in a line, both as a free jet, and as a confined jet, are carried out in three parts: (1) on a single rectangular free jet, (2) on the same jet in a multiple free jet configuration, and (3) on the same jet in a multiple jet configuration with confining surfaces (two parallel plates are symmetrically placed perpendicular to the long dimension of each lobe covering the entire flow field under consideration). In the case of a single rectangular free jet, the flow field of the jet is characterized by the presence of three distinct regions in the axial mean velocity decay and are referred to as: potential core region, two dimensional type region, and axisymmetric type region. In the case of a multiple free jet, the flow field for downstream distance X greater than 60D (D = width of a lobe) resembles that of a jet exiting from a two dimensional nozzle with its short dimension being the long dimension of the lobe.

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

NASA Astrophysics Data System (ADS)

Dalla Barba, Federico; Picano, Francesco

2018-03-01

The evaporation of droplets within turbulent sprays involves unsteady, multiscale, and multiphase processes which make its comprehension and modeling capabilities still limited. The present work aims to investigate the dynamics of droplet vaporization within a turbulent spatial developing jet in dilute, nonreacting conditions. We address the problem considering a turbulent jet laden with acetone droplets and using the direct numerical simulation framework based on a hybrid Eulerian-Lagrangian approach and the point droplet approximation. A detailed statistical analysis of both phases is presented. In particular, we show how crucial is the preferential sampling of the vapor phase induced by the inhomogeneous localization of the droplets through the flow. Strong droplet preferential segregation develops suddenly downstream from the inflow section both within the turbulent core and the jet mixing layer. Two distinct mechanisms have been found to drive this phenomenon: the inertial small-scale clustering in the jet core and the intermittent dynamics of droplets across the turbulent-nonturbulent interface in the mixing layer, where dry air entrainment occurs. These phenomenologies strongly affect the overall vaporization process and lead to an impressive widening of the droplet size and vaporization rate distributions in the downstream evolution of the turbulent spray.

An Experimental Study of the Near Field Region of a Free Jet with Passive Mixing Tabs

NASA Technical Reports Server (NTRS)

Bohl, D. G.; Foss, J. F.

1997-01-01

An experimental study was performed to determine the flow characteristics of a tabbed free jet. Results were acquired in the near field (nominally 2 tab widths upstream to 2 tab widths downstream of the exit plane) of a tabbed jet. Upstream pressure results showed static pressure distributions in both the x-and y-directions along the top surface of the tunnel. Hot-wire measurements showed rapid expansion of the core fluid into the ambient region. Two counter rotating regions of streamwise vorticity were shown on each side of the primary tab. An enhancement of the tabbed jet concept was proposed and tested. Specifically, two tabs, half the scale of the primary tab, were added to the primary tab to provide attachment surfaces for the normally occurring ejection of fluid. The secondary tabs caused a slight increase in the streamwise vorticity created from the upstream static pressure gradient while significantly increasing the re-oriented boundary layer vorticity. The combined pumping effect of the two counter rotating regions of vorticity caused a significant increase in the transport of the jet core fluid into the surrounding region.