bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of the Straight l = 1 Scyllac Configuration
Authors: Freidberg J. P.
Published: February 2004

A theory is presented for the stability of the m = 1 mode in the high β, l = 1 scyllac configuration. The results agree with each of the two fundamental theories previously derived in the appropriate limits and significantly extends the range of parameters over which the theory applies.
Experimental Test of the Quasilinear Theory of the Gentle Bump Instability
Authors: Roberson C. , Gentle K. W.
Published: February 2004

The nonlinear evolution of the instability resulting from a gentle bump on the tail of the electron velocity distribution of a plasma was investigated experimentally. An electron beam with a large velocity spread was injected along the axis of a collisionless plasma column immersed in a strong magnetic field. The equilibrium wave amplitude, spectral shape, and electron velocity distribution were measured and found to be in good agreement with the predictions of quasilinear theory, providing the beam met the requirements of the theory. When the beam was too strong to be a gentle bump, deviations from quasilinear theory appeared.
Modification of Electromagnetic Field in an Underdense Turbulent Plasma
Authors: Shkarofsky I. P. , Ghosh A. K.
Published: February 2004

The modification of a microwave signal propagating transversely through a turbulent jet using a movable antenna receiver within the plasma is observed. The plasma is very underdense. The turbulence produces an additional 15-20% attenuation of the coherent signal with a corresponding buildup of the incoherent energy, in agreement with theoretical predictions based on the turbulent density profile and the scale length as measured by electrostatic probes. The two quadrature components of the field are individually detected as well as their mean square values, their correlation functions, and spectrum functions. There are some details which disagree with theory, in particular, the observation of negative cross correlation between the two quadrature field components. The incoherent signal is observed, as a function of penetration distance, to go through the transition from elliptical, with mainly phase fluctuation, to “crescent” shaped with a stronger preference toward one end, and finally to a quasicircular type of noise.
Verification of Theory on Weak Turbulence Relating to the Sequence of Diffuse Plasma Resonances in Space
Authors: Oya Hiroshi
Published: February 2004

An interpretation of the sequence of diffuse plasma resonances observed by space probes (Alouette 2 and ISIS-1 satellites) is developed in terms of wave-particle nonlinear interaction in a weakly turbulent plasma including the electrostatic electron cyclotron harmonic wave instability. Observations and theory indicate that the center frequency fDn of the diffuse plasma resonance [nfH<fDn<(n+1)fH and fDn<fT] and the center frequency of the electrostatic wave resonance [nfH<fQn<(n+1)fH and fT<fQn] satisfy the condition of the wave-particle nonlinear interaction with the 2fH resonance according to the condition 2π[fH− ( fQn+2−fDn)]=[K(fQn+2)− k (fDn)]·v, where nfH, fT and v are the cyclotron harmonic frequency, the upper hybrid frequency, and the thermal velocity of the plasma, respectively; and k(f) is a wave vector as a function of a frequency f. The weaker diffuse plasma resonance branch observed at fDn1 (where fDn1>fDn) satisfies the condition 2π[fH− (fQn+1−fDn1)] = [k(fQn+1)−k(fDn)]·V. The longest time duration of the fDn resonance coincides with the most favorable condition for the electrostatic electron cyclotron harmonic wave instability which is obtained by solving the dispersion equation obtained for a linear approximation of the kinetic wave equation for the warm magnetoactive plasma. The electrostatic field due to the transmission of the intense rf pulse produces plasma turbulence involving nonlinear wave-wave interaction and temperature anisotropy which leads to the instability; this instability supplies energy to the turbulence. The fH and 2fH nonlinear wave-particle interactions in the turbulence heat the plasma to maintain the temperature anisotropy which lengthens the time over which the cyclotron harmonic wave instability conditions prevail; this process can be thought of as a feedback system. The results also indicate that the fH, 2fH and fQn waves are dependent on the fDn resonance generation.
Signal Dispersion and Faraday Rotation in Hot Plasmas
Authors: Skilling J.
Published: February 2004

The signal dispersion and Faraday rotation of high-frequency radiation passing through a hot, possibly relativistic plasma are investigated. Corrections are found to the formulas given by cold-plasma theory. Results for the damping are compared with synchrotron self-absorption formulas.
Spectrum of Eigenvalues of the Orr Sommerfeld Equation for Blasius Flow
Authors: Jordinson R.
Published: February 2004

Space amplified eigenvalues of a finite difference version of the Orr-Sommerfeld equation have been calculated for Blasius mean flow. If the primary mode is unstable, the remaining eigenvalues in the fourth quadrant of the c plane lie close to a curved line.
Explanation of Thermal Plume Growth Rates
Authors: Lumley J. L.
Published: February 2004

In axisymmetric thermal plumes the tendency of the entrainment strain rate to compress the large eddies horizontally is balanced by the tendency of the stable vertical temperature distribution near the edge to compress the large eddies vertically, producing wake-like (not jet-like) values of RT.
Spectral Calculations of Isotropic Turbulence: Efficient Removal of Aliasing Interactions
Authors: Patterson G. S. , Orszag Steven A.
Published: February 2004

An algorithm is given for the rapid calculation of the convolution sums appearing in the Fourier-transformed Navier-Stokes equations. In three space dimensions, the new algorithm is a factor of 4 more efficient than previously suggested algorithms.
Convergence of the Long-Wavelength Expansions in a Classical Fluid
Authors: Miller Bruce N.
Published: February 2004

The convergence of Irving and Kirkwood's long-wavelength expansion for the stress tensor is examined. The convergence is shown to be only asymptotic for realistic intermolecular potentials.
Initial Ionization in a Helium Shock Wave
Authors: Kalra S. P. , Measures R. M.
Published: February 2004

A comparison has been made between the theoretical two-step collisional ionization model and the observed profile for a helium shock wave using a laser Fabry-Perot interferometer.
Energy Transfer to Ions from an Unneutralized Electron Beam
Authors: Widner M. M. , Guest G. E. , Dory R. A.
Published: February 2004

Simulation studies of the response of an inhomogeneous plasma to an unneutralized electron beam have led to an analytic theory of the energy transfer from the beam to ambient ions. Energy is transferred to the plasma by the ion-hybrid resonance and is retained because of phase-mixing.
Magnetohydrodynamic Mach Cones
Authors: Yen David H. Y.
Published: February 2004

The problem of general fast-hyperbolic magnetohydrodynamic flows past a point source is considered. Questions on the geometry of the magnetohydrodynamic Mach cones and on the nature of the singularities of the disturbances carried on such cones are studied.
Threshold Electric Field for Excitation of Parametric Instabilities in Inhomogeneous Plasmas
Authors: Eubank H. P.
Published: February 2004

Experimental observation of the threshold power required for excitation of the parametric instability is found to be in reasonably good agreement with the theory for inhomogeneous plasmas, and exceeds the threshold for a uniform plasma by an order of magnitude.
Ionization Instability in the Propagation of High-Current Relativistic Electron Beams in Gases
Authors: Andrews M. L. , Davitian H. , Fleischmann H. H. , Nation J. A.
Published: February 2004

Measurements of electron beams propagating in a gas-filled drift tube show pressure-dependent longitudinally periodic variations of light intensity, μ-wave emission, beam head velocity, and net current, which are consistent with an ionization instability.
Viscous Effect on Waves Reflected Nearly Parallel to the Boundary
Authors: Yang Chun-Chuan
Published: February 2004

The anomalous laws of wave reflection from a rigid plane surface in an inviscid, rotating, stratified Boussinesq fluid are due to the anisotropic feature of the wave motion. The singularity of the reflection process in the inviscid linear analysis, where the reflected wave amplitude becomes very large when the ray of the reflected wave is nearly parallel to the reflection boundary, is studied for the limiting cases by considering viscous boundary effect on wave motion. As the angle that the reflected wave (ray) makes with the wall becomes very small, the effect of boundary layer on wave reflection becomes significant. In the nonsingular case, the boundary layer thickness is ∼R−1/2 where R ( = n/νκ2) is the wave Reynolds number. A thicker boundary layer, R−1/3 is needed for the critical wave reflection and only within this layer is singularity removed. Two-dimensional waves were generated in the laboratory by vertically oscillating a small wave-making flap inside a clear Plexiglas container. The wave properties are determined by observing the motions of aluminum particles suspended in the working fluid. Some predictions have been tested and confirmed.
Absorption of Capillary-Gravity Waves in Shallow Water
Authors: Walbridge N. L. , Woodward L. A.
Published: February 2004

Measurements of spatial absorption coefficients in shallow water are presented. The smallest depth was 2.3 times the thickness of the boundary layer. Basset's determinant was evaluated exactly. From the resulting equation, the spatial coefficient was found directly. This direct approach made it possible to calculate theoretical values for small depths. The measured values agreed with the theoretical values within the rather large experimental error.
Structure of Temperature Fluctuations in the Turbulent Wake behind a Heated Cylinder
Authors: Freymuth Peter , Uberoi Mahinder S.
Published: February 2004

Convection, production, diffusion, and dissipation of temperature fluctuations have been measured in the dynamically similar turbulent wake behind a headed circular cylinder 1140 diameters downstream from the cylinder at a Reynolds number of 960. The measurements show strong production and dissipation and moderate convection and diffusion. In addition, the dependence of one-dimensional spectra of temperature fluctuations on wake parameters and the skewness of the temperature derivative have been measured for the Reynolds number range 440-69 000. All measurements are consistent with the assumption of local isotropy except for the skewness of the temperature derivative.
Laser Probing of a Weakly Ionized Turbulent Gas: Comparison of Neutral and Plasma Fluctuations
Authors: Granatstein V. L. , Levine A. M. , Subramanian M.
Published: February 2004

The structure of a turbulent gas flow may be probed by analyzing scintillations of a laser beam which has traversed the turbulent medium. This technique is used to measure the spectrum of neutral gas turbulence in a pipe flow where the gas is nonuniformly heated and weakly ionized by an electrical discharge. First, the usual isotropic analysis relating the spectrum of light scintillations to the fluid turbulence is extended to include strong anisotropy as is appropriate in the present case. Second, the gas turbulence spectrum revealed by the scintillation, as well as by a hot film anemometer, is compared with the spectrum of plasma density fluctuations. It is found that the scale size of the neutral gas turbulence is larger than the scale size of the plasma density fluctuations by a factor of 2 for a case in which the plasma column is constricted to a considerably smaller diameter than the pipe. This indicates that whenever the plasma production process is constricted to dimensions smaller than the gas turbulence scale size, then the spectrum of wind-driven plasma fluctuations will not be representative of the background gas turbulence.
Model for Rotating and Nonuniform Planetary Exospheres
Authors: Hartle R. E.
Published: February 2004

The model neutral exosphere with a uniformly rotating exobase is generalized by allowing variations in exobase density and temperature which characterize the thermosphere just below the base. The corresponding velocity distribution function, satisfying the collisionless Boltzmann equation, is constructed and used to form a general expression for the velocity moments. Resulting density profiles of rotating exospheres with nonuniform densities and temperatures on the exobase are compared with corresponding nonrotating exospheres. Density enhancements due to rotation are found to be greatest above regions of exobase density or temperature minima. Equatorial density enhancements of terrestrial hydrogen, resulting from rotation, are estimated to be 15%-17% at altitudes of 10-20 earth radii. Corresponding increases in terrestrial helium are 30%-50% on the equator at altitudes of 0.7 to 1 earth radii even when there is a polar density bulge in the barosphere.
Velocity Slip Coefficient and the Diffusion Slip Velocity for a Multicomponent Gas Mixture
Authors: Loyalka S. K.
Published: February 2004

Simple and accurate expressions for the velocity slip coefficient and the diffusion slip velocity are obtained by applying a variational technique to the linearized Boltzmann equation for a multicomponent gas mixture.
Rotational Temperature in an Underexpanded Jet
Authors: Repetski Jerry J. , Mates Robert E.
Published: February 2004

The axial rotational temperature distribution in an underexpanded nitrogen jet emitted from a sonic orifice has been investigated. The expansion is from room temperature and the gas possesses negligible vibrational energy. The observed difference between the rotational temperature measured with an electronbeam probe and the isentropic value can be described by a rotational relaxation analysis. The governing flow equations were integrated numerically by the classical fourth-order Runge-Kutta method. The rotational relaxation time developed by Lordi using Wang Chang and Uhlenbeck's formal kinetic theory and Parker's molecular model was employed. Both the easy and difficult energy transfer cases were investigated and the easy case was shown to underestimate nonequilibrium affects. The numerical solutions were very sensitive to the separation between the repulsive force centers, for both energy transfer cases. The rotational temperature distributions obtained in this study are in general agreement with existing experimental data for nitrogen.
Gain Kinetics of CO2 Gasdynamic Laser Mixtures at High Pressure
Authors: Christiansen Walter H. , Tsongas George A.
Published: February 2004

A combined analytical and experimental investigation of rapidly expanded CO2 laser mixtures is described. Study of the vibrational kinetics indicates that population inversions with high vibrational energy density can be produced at high pressures by utilizing low (starved) concentrations of CO2. Scaling laws for predicting the gain of starved systems are developed. A description is given of gain measurements carried out using a CO2 laser to probe the flow in a nozzle at the point where the Mach number is approximately four. Population inversions at static pressures as high as about 1 atm have been observed and found to be in reasonable agreement with predictions.
Population Inversions in an Expanding Gas: Theory and Experiment
Authors: Anderson John D. , Humphrey Richard L. , Vamos John S. , Plummer Michael J. , Jensen Richard E.
Published: February 2004

It is well established that population inversions between the (001) and (100) vibrational energy levels of CO1 can be created by rapid expansions of CO2-N2-H2O or He mixtures through supersonic nozzles. New experimental results are presented for such inversions. These experiments were conducted in both the 3-MW arc tunnel and the 12.7-cm shock tunnel at the Naval Ordnance Laboratory. The results support previously published theoretical predictions obtained with a numerical, time-dependent, nonequilibrium nozzle flow analysis employing a simplified vibrational kinetic model. This theory is also compared with experimental data obtained by other investigators.
Similarity Analysis for Relativistic Flow in One Dimension
Authors: Eltgroth P. G.
Published: February 2004

Transformations and restrictions are applied to the equations of relativistic flow in one space dimension which reduce the problem to a consideration of simpler differential equations. The results are closely related to those of characteristic analysis. It is found that for cases in which one similarity variable describes the system, the fluid has constant velocity along straight lines in the x, ct system. Two special equations of state, p = 13E and p = 13(E−nmc2) are considered in detail. Analytic results are obtained and are applied to the problem of shock propagation into a region of decreasing density.
Radiative Transfer Effects on Reflected Shock Waves I. Transparent Gas
Authors: Su F. Y. , Olfe D. B.
Published: February 2004

Analytical and numerical calculations are carried out for the effects of radiative cooling on the flow field and heat transfer behind a reflected shock wave. The analytical solutions are developed by an expansion procedure about the Newtonian limit; i.e., the flow variables are expanded in the small parameter ε representing the initial density ratio across the shock front. Solutions carried out through the zeroth- and first-orders in ε show an accuracy to the order of ε2; viz., for the specific conditions considered the analytically calculated enthalpy changes agree to within 2% with the numerically computed changes. The numerical procedure consists of a finite difference calculation with pressure gradients neglected. The analytical calculations show that pressure gradient effects may be neglected, except at very long times when the shocked gas has cooled by a large amount. Our calculations show much greater shock-wave attenuation than does a previous numerical computation. This difference is attributed to a better representation of the thermodynamic properties in the present calculations.
Evaluation of Two Statistical Models Using the Shock Structure Problem
Authors: Giddens D. P. , Huang A. B. , Young V. Y. C.
Published: February 2004

The accuracy of two statistical models for the collision integral of the Boltzmann equation has been evaluated by applying the models to the solution of the problem of shock structure in a monatomic gas and then comparing the theoretical results with available experimental data. The two models considered here are the Bhatnagar-Gross-Krook and ellipsoidal statistical models. The Mach number range covered is 1.59-10.7 and profiles for density and, where available, temperature are compared. The method of numerical solution is the discrete ordinate technique which looks quite promising for application to more complicated models. The results indicate that the ellipsoidal statistical model, which gives a correct value for the Prandtl number, gives accurate results for a low Mach number shock. However, the accuracy degenerates as the Mach number increases. The Bhatnagar-Gross-Krook model gives poorer agreement with experimental data in all cases examined.
Structure of Normal Shock Waves in Gas Mixtures
Authors: Harris Wesley L. , Bienkowski George K.
Published: February 2004

A theoretical analysis of steady, normal shock structure in binary gas mixtures of inert, monatomic gases is given. The analysis is based on the moment method of kinetic theory. The governing equations of this two-temperature-two-velocity model are in no way restricted by initial concentration of the species, mass ratio of the species, or Mach number. The system of equations which describes the structure includes the conservation of mass of each species, the conservation of momentum and energy of the mixture, the transfer of momentum and peculiar energy equations, the evolution of the stress moment of each species, and the heat flux moment of each species. The nondimensional parameters which characterize the phenomenon are identified as the number density ratio in the free stream η = (nj/ni)−∞, the mass ratio θ = mi/mj, and the mixture Mach number in the free stream M−∞. By choosing various combinations of these parameters, five different types of structures are proposed. By further restricting the light species and heavy species upstream Mach number, a given type of structure may be shown to require more than one scale for a complete transition. The anomalies resulting from some continuum theories and numerical calculations are investigated. The proper application of the Mott-Smith ansatz to normal shock waves in binary gas mixtures is clarified. Comparison with existing experimental and theoretical results is made.
Dielectrophoretic Effects in Laminar Forced Convection between Two Parallel Plates
Authors: Savkar S. D.
Published: February 2004

The influence of a 60-Hz ac electric field on a thermally stratified flow of a dielectric between two parallel plates is considered. The coupled hydrodynamic problem is first cast as a stability problem and solved for a Poiseuille base flow in the limit of low Reynolds number. Two modes of instability were examined, transverse roll cells and longitudinal roll cells. Of the two, the latter appears to be the more probable mode and the critical dielectrophoretic Rayleigh number seems to be independent of Reynolds number. The transverse modes exhibit an overstability. A crude verification of the theory is to be had from data obtained on a parallel plate test apparatus. The experimental parametric results clearly demonstrate the role of the dielectrophoretic augmentation of heat transfer. It is found that the heat transfer coefficient is a direct function of the heat flux rate and the applied potential difference, and an inverse function of the flow rate.
Laminar Flow in Circular Pipes under the Effect of a Traveling Magnetic Field
Authors: Fawzi T. H. , Burke P. E.
Published: February 2004

The interaction between the flow of a conducting incompressible fluid in an infinitely extended circular pipe and the magnetic field created by an azimuthal traveling wave current sheet surrounding the pipe is studied. Only low magnetic Reynolds number flows are considered. Exact solutions for the magneticfield distribution are obtained. Closed form solutions for the laminar velocity profile are developed. The latter are used to examine the effect of the magnetic field on the friction coefficient and total energy balance. The solutions show that, for positive pressure gradients and strong magnetic fields, secondary flows appear. These flows have previously been observed experimentally. The solutions also show that the stabilizing effect of the magnetic field in general, depends on an equivalent Hartmann number—which is a function of the wavelength of the traveling wave—and on the difference between the wave velocity and the average fluid velocity.
Magnetohydrodynamics of Conical Flows
Authors: Narain Jai Prakash , Uberoi Mahinder S.
Published: February 2004

The effect of diverging or converging electric currents on a stationary, viscous, incompressible, conducting body of fluid, confined in a cone of infinite extent, is investigated. The fluid moves down from upstream infinity near the walls and as it approaches the apex of the cone, it changes its direction in the core of the cone and moves toward upstream infinity near the axis. With increasing currents, the velocity near the axis rises very rapidly. Similar phenomenon have been observed in the laboratory electric arcs and in thermal plasmas of the solar atmosphere. Next, when a fixed amount of fluid is drained from the apex of the cone, the flow divides into two regions far from the apex. The drained fluid reaches the apex only through a narrow region near the walls whereas fluid in the core of the cone executes a secondary motion, similar to the first case of confined flow. There exists a stagnation point on the axis and its location is primarily controlled by current density, fluid drainage rate, and the cone angle of the configuration.
Line Sink in Uniform Magnetic Field
Authors: Narain Jai Prakash , Uberoi Mahinder S.
Published: February 2004

The motion of an inviscid, incompressible, and conducting fluid due to a line sink in a uniform strong magnetic field is considered. The solutions show that motion is confined in a narrow region parallel to the magnetic field. Such a motion for a point sink has erroneously been named as a wake or backward jet flow. Finally, the known solution of a point sink in uniform magnetic field is extended to apply nearer the sink than the original solution.
Argon and Nitrogen Plasma Viscosity Measurements
Authors: Schreiber P. W. , Hunter A. M. , Benedetto K. R.
Published: February 2004

The viscosity of argon and nitrogen is experimentally determined from 10 500 to 12 750°K at atmospheric pressure. The viscosity is shown to be a simple function of the velocity and the axial static pressure gradient in the arc discharge used for this experiment. A unique probe system is used to measure the difference between stagnation and static pressures across the diameter of the plasma column, and the approximate equation which converts the pressure difference to velocity is shown to be valid. The axial static pressure gradient is measured directly. Measured viscosities are compared with the experimental and calculated results of other investigators.
Structure of the Plasma Fireball Produced by a CO2 Laser
Authors: George E. V. , Bekefi G. , Ya'akobi B.
Published: February 2004

The space and time resolved structure of a helium plasma produced with a repetitive CO2 laser is studied during the first 15 μsec of the afterglow period. The spectra of several neutral and ionized helium lines are used in the determination of the density and temperature profiles of the luminous fireball. It is found that the plasma is comprised of a dense, hot core which emits primarily ionic lines, and a well-defined tenuous outer shell which is primarily the source of neutral emission lines. This “two-component” plasma structure develops at ∼0.4 μsec after breakdown, at about the time when the luminous fireball dissipates its expansion energy and comes to a virtual standstill.
Stimulated Scattering and Self-Focusing in Laser-Produced Plasmas
Authors: Palmer A. J.
Published: February 2004

Calculations are presented of the threshold conditions for the onset of stimulated scattering processes and self-focusing within a fully ionized, laser-produced, spark plasma, using a linearized theory. Plasma density fluctuations induced through ponderomotive forces and thermal deposition are found to give rise to net gains for stimulated Thomson scattering for a realizable set of values of plasma parameters and laser power. Also, the results for the self-focusing thresholds are consistent with previously reported conditions for observing filamentation in laser-induced, gas breakdown plasmas.
Nonlinear Surface Waves on an Axisymmetric Magnetohydrodynamic Pinch
Authors: Shen M. C.
Published: February 2004

An asymptotic approach based upon Lundquist equations is developed for the study of nonlinear wave propagation on a pinched cylindrical plasma. Wave speed and asymptotic evolution equations are derived. A comparison between linear stability criteria and results of the nonlinear theory is made and a set of refined stability criteria is obtained.
Ion-Wave Current Instabilities and Anomalous Resistivity
Authors: Kan J. R.
Published: February 2004

A theory of ion-wave current instabilities which takes into account, in a self-consistent manner, the inhomogeneities generated by field-aligned currents in a collisionless plasma is presented. Diamagnetic current associated with the current-produced density gradient is included in the distribution. The theory predicts that for a given frequency, the current threshold for ion-wave current instabilities is, in general, much below the threshold of ion acoustic instability in a uniform plasma as given by Fried and Gould. The current threshold is essentially zero in the limit when the ion Landau damping effect is negligible, or equivalently, the ion-wave current instabilities are absolute if there are no limitations on the wave-length. This is true even in the absence of externally applied density gradients in contrast to Kadomtsev's drift-wave results. For dimensions of interest in laboratory plasmas, the predicted linear growth rate increases with increasing longitudinal wavelength and with decreasing wavelength parallel to the diamagnetic current. Under the conditions of an experiment on anomalous resistivity (the dimensions but not the geometry of the machine have been considered), there is good agreement between the predicted onset of ion-wave current instabilities and the experimental data on the onset of anomalous resistivity.
Convective Motions Due to Trapped Particles of Plasmas Confined in an l = 3 Stellarator Field
Authors: Miyamoto Kenro , Mohri Akihiro , Inoue Nobuyuki , Fujiwara Masami , Yatsu Kiyoshi
Published: February 2004

Confinement of the plasmas in a stellarator of l = 3 is studied. The distribution of density and potential over the plasma cross section shows the existence of convective cells due to the trapped particles at the three corners of the magnetic surfaces, where the magnitude of the field is a minimum along the lines of force. The observed decay time can be explained in an order-of-magnitude discussion by the observed convective motions and the low-frequency fluctuations observed in the boundary region.
Flows with Radiant Energy Absorption and Thermonuclear Reactions behind the Shock Wave
Authors: Rosciszewski Jan , Su Fa Yan
Published: February 2004

Results of numerical calculations of the flow field behind the shock wave with intense laser radiation absorption and laser-triggered thermonuclear reactions are presented. It is shown that, in the case of absorption coefficient increasing with temperature (high Z materials), absorption after a certain time leads to a detonationlike phenomenon. In the case of laser-triggered d-t thermonuclear reaction it is shown that maximum energy release occurs in the distance of one-half the absorption mean free path, and in the one-dimensional case the reaction rate grows to infinity if the initial shock and the laser pulse are strong enough.
General Solution for Perturbed Plane Couette Flow
Authors: Rosen Gerald
Published: February 2004

A closed-form general solution for perturbed plane Couette flow is reported. The solution shows that certain dynamical modes feature an intermediate period of resonance-like growth prior to the final period of viscous decay.
Cross-Hatched Erosion Patterns at the Beach
Authors: Hains F. D.
Published: February 2004

Cross-hatched erosion patterns caused by water waves have been observed on beach sand. An analysis of two-dimensional boundary layer over a sand bed shows that spatially periodic solutions can occur if the outer flow is hyperbolic.
Laser Measurement of the Nitrogen to Carbon Dioxide Vibrational Energy Transfer Time
Authors: Wilson J.
Published: February 2004

An experiment is described in which two cavities are installed on a gasdynamic laser. From the power at the downstream cavity, an evaluation of the cross section for vibrational transfer between nitrogen and carbon dioxide can be made. The result is in agreement with other measurements.
Effects of an External Circuit on the Dispersion of Soluble Matter in a Magnetohydrodynamic Channel Flow
Authors: Soundalgekar V. M.
Published: February 2004

The effective Taylor diffusion coefficient D* decreases more rapidly with increasing Hartmann number, M, in a short-circuited channel flow as compared with an open-circuited case. In the generator, D* is almost negligible for M>20. In an accelerator, an increase in Vg* leads to an increase in D*.
Structure of the Second-Order Plasma Wave Echo
Authors: Goforth R. , Gentle K. W.
Published: February 2004

Second-order electron plasma wave echoes have been experimentally studied in a two-density plasma. The phase velocity of the echo rise is that of the first primary wave, and the echo decay is characteristic of the resonant plasma response at the echo frequency.
Observations of the Beam-Plasma Instability
Authors: Gentle K. W. , Roberson C. W.
Published: February 2004

The nonlinear limit of the instability driven by a low density cold electron beam in a collisionless plasma is experimentally found to be determined by the trapping of the beam by the most rapidly growing wave.
Flutelike Microinstabilities in Mirror-Confined Plasmas with Broad υ⊥ Distributions
Authors: Young T. S. T. , Callen J. D. , McCune J. E.
Published: February 2004

It is demonstrated that it is the width of the positive derivative region of the υ⊥ distribution function which determines whether the flutelike microinstabilities of a magnetized plasma occur at high densities.
Space-Charge Condition and Mach Number in an Electrostatic Shock
Authors: Persson Hans
Published: February 2004

Electrostatic, shock-like Bernstein-Greene-Kruskal equilibria studied by Montgomery and Joyce are considered. If the electron distribution is continuous at the boundary between free and trapped electrons, the Mach number with respect to the ion sound velocity cannot be lower than unity.
Evidence of Density Inhomogeneity Broadening of Plasma Satellites from Light Scattering
Authors: Chan P. W.
Published: February 2004

Light scattering from an argon plasma jet at two values of the plasma current has produced evidence supporting the assumption that the linewidths of the plasma satellites reported previously are due to density inhomogeneity and not due to collisional broadening effects.
Turbulent Wake in a Passively Stratified Field
Authors: Alexopoulos C. C. , Keffer J. F.
Published: February 2004

A two-dimensional turbulent wake superimposed upon a linearly stratified main stream has been examined. The buoyancy forces were negligibly small and the temperature could be treated as a passive scalar contaminant. Mean and fluctuating temperature and velocity distributions were measured across the wake and a self-preserving analysis was developed for the growth of the thermal wake in terms of a length and intensity scale. The results showed that the maximum temperature defect increases in the streamwise direction as the wake spreads laterally.
Turbulent Pipe and Channel Flow
Authors: Lundgren T. S.
Published: February 2004

Turbulent pipe and channel flow and turbulent plane Couette flow are studied by means of turbulent model equations first proposed by Prandtl.
Family of Similarity Flows with Vortex Sheets
Authors: Alexander R. C.
Published: February 2004

Prandtl's two-dimensional, time-dependent similarity solutions are corrected and extended to cases of N-branched vortex sheets possessing a certain central symmetry. For both N = 1 (Prandtl's case) and N = 2 it is found that the similarity parameter m is restricted to the range m ≤ 0.5. When N = 1, multiple solutions are found for a given value of m provided |m| is sufficiently small compared with one. A property of these multiple solutions is that the tangential velocity to the concave side of a vortex sheet is 0[exp( −4π) smaller than the tangential velocity to the convex side. All values of m are found to be admissible for the case N = 3. In all cases it is found that certain features of the flows resemble a classical (but time-dependent) circular vortex. For example, it is found that the circulation in a disk of radius r is proportional to r2. There are also important differences. The flow fields for N = 1, 2, and 3 are described in some detail.
Transient Poiseuille Flow Separation
Authors: Chou F. K. , Sandborn V. A. , Sadeh W. Z.
Published: February 2004

The time varying flow through a pipe is analyzed. Separation velocity profiles obtained under the influence of periodic pressure fluctuations were evaluated. These velocity profiles are compared with relaxed and unrelaxed separation concepts. It is found that a one parameter correlation is too limited to cover all possivle separation cases. In particular, the unsteady unrelaxed separation extends over a relatively wide range of velocity distributions.
Stability of a Cylindrical Viscous Jet Surrounded by a Flowing Gas
Authors: Chow T. S. , Hermans J. J.
Published: February 2004

Using linear perturbation theory, the effect of a slightly viscous gas on the stability of a viscous jet is estimated. The gas flows in the direction of the jet axis. The perturbation in the gas is supposed to be governed by the equations for an inviscid, incompressible fluid, but the gas viscosity is taken into account to a first approximation by means of an energy balance. The method is shown to give correct answers for a viscous jet in a vacuum. For the case of uniform gas velocity the results agree with those of earlier work by Weber and by Levich. In this case the effect of the gas viscosity is very small. For nonuniform gas flow, using a logarithmic velocity profile, solutions are found for the two limiting cases in which the gas velocity is either large or small compared with the wave velocity. The results for these two limiting cases do not differ greatly from each other and predict that the gas flow has a substantial stabilizing effect on the jet when the gas velocity is large.
Instability due to Viscosity and Density Stratification in Axisymmetric Pipe Flow
Authors: Hickox Charles E.
Published: February 2004

The stability of a steady, axisymmetric, laminar, primary flow composed of two fluids flowing concentrically in a straight circular tube is investigated by the method of small perturbations. Both asymmetric and axisymmetric disturbances to the primary flow are considered. It is demonstrated that, regardless of the size of the Reynolds number, no situations are encountered for which the primary flow is stable to both types of disturbances, simultaneously. The primary cause of instability is found to be the difference in viscosities of the two fluids.
Quantum Transport Cross Sections for Ionized Gases
Authors: Hahn Hong-sup , Mason E. A. , Smith Francis J.
Published: February 2004

Transport cross sections and collision integrals are calculated over a wide range of energies and temperatures for the attractive and repulsive screened Coulomb potentials. Results accurate to 1% over the whole range from classical to quantum-mechanical behavior are given in the form of numerical tables. Results of lower accuracy are given as analytical expressions.
Some Analytic Solutions to the Linearized Boltzmann Equation with the Ellipsoidal Model
Authors: Huang A. B. , Giddens D. P.
Published: February 2004

Analytic solutions of the linearized Boltzmann equation with the ellipsoidal model have been developed for several gasdynamic problems based on the discrete ordinate method. The results reduce to those previously reported for the Bhatnagar-Gross-Krook model equation for a special case.
Cylindrical Couette Flow Experiments in the Transition Regime
Authors: Alofs Darryl J. , Springer George S.
Published: February 2004

Density distributions were measured in rarefied argon contained between two concentric cylinders, the inner one rotating, the outer one stationary. The experiments were performed with a Mach number near unity, based on the surface speed and surface temperature of the rotating cylinder. Particular attention was focused on obtaining data in the slip and transition regimes where the Knudsen number, defined as the ratio of the mean free path to the gap size between the cylinders, varied from 0.04 to 1.07. The density distributions were measured by observing the gas luminescence induced by the passage of a narrow beam of high energy electrons through the gas. In addition to the density measurements, heat transfer and drag measurements were also made in order to estimate the values of the thermal accommodation and the tangential momentum accommodation coefficients. The experimental results were compared to solutions of the Navier-Stokes and Burnett equations as given by Schamberg and Lin and Street. The results of the Navier-Stokes and the Burnett equations were found to approximate the density distributions well at Knudsen numbers below ∼0.05 and ∼0.2, respectively. At higher Knudsen numbers the analytical and experimental results differ considerably.
Application of Kinetic Theory to the Problem of Evaporation and Condensation
Authors: Pao Young-ping
Published: February 2004

The motion of a vapor gas in contact with interphase surfaces is studied on the basis of kinetic theory of gases. The mass and energy fluxes are determined from the condition of the vapor far away from the interfaces. The result for a vapor gas between two interfaces shows that the temperature gradient in the vapor is opposite in sign to the externally maintained temperature difference.
Kinetic Theory of Shock Tube Problems for Binary Mixtures
Authors: Wu Yau , Lee C. H.
Published: February 2004

The flow of binary gas mixture in a shock tube is treated according to the kinetic theory as an initial value problem. The model equations of Gross-Krook and Morse are used. The numerical procedure is extended from the method proposed by Chu in his work on shock tube problems for a single-component gas. The formation of shock waves, diffusion of the contact layers and dispersion of expansion waves for both species are clearly indicated in the solutions. The stationary shock structures have been obtained in a relaxation process from initial discontinuity by superposing a shock wave speed. Argon and neon are chosen as the binary mixture. Shock Mach numbers 1.369, 1.5, and 2.07 with equal mole fractions of the mixture are calculated.
Collision Free Ionizing Shock
Authors: Pert G. J.
Published: February 2004

The structure of an ionizing wave propagating into a low density un-ionized gas is considered. It is shown that due to phase mixing of the velocities of ions formed at different points in the wave, the oscillatory nature of the wave is damped and the front may form a shock transition. Only the existence of these waves is demonstrated; their stability is not considered.
Collisionless Sheath near an Electrode in the Presence of a Magnetic Field
Authors: Hassan H. A. , Seals R. K.
Published: February 2004

Magnetic field effects on the structure of a collisionless sheath near a planar electrode are considered. The model assumes the distribution functions normal to the electrode to be Maxwellian. The case where the electric and magnetic fields are mutually perpendicular is discussed in detail. It is shown that, in this case, the sheath is always stable and one need not invoke a sheath criterion. The resulting nonlinear differential equations for the electric and magnetic potentials are solved by an exact numerical scheme for an argon plasma near an anode. The results predict the effect of magnetic fields on anode losses in are jets rather well.
Resistive Plasma Rotation and Shock Formation in Toroidal Geometry
Authors: Hazeltine R. D. , Lee E. P. , Rosenbluth M. N.
Published: February 2004

The rotation of a toroidally confined plasma about its magnetic axis due to resistive diffusion is studied by means of a single fluid model in which the only dissipation occurs through a small scalar resistivity. The time evolution of the rotation is examined by considering the resistivity as inducing first-order time variation on a dissipationless steady state. The known instability of flows with small rotational velocity to rapidly speed up toward a critical speed is confirmed; more importantly, it is found that a shock which develops at the critical speed stabilizes the flow, so that the ultimate state of the system is characterized by steady rotation with a very weak shock front directed radially inward from the magnetic axis. The outward flux of plasma in this state is found to be essentially the Pfirsch-Schlüter flux enhanced by a factor of the square root of the aspect ratio.
Ponderomotive Force on Laser-Produced Plasmas
Authors: Lindl John D. , Kaw Predhiman K.
Published: February 2004

The deconfining ponderomotive force exerted by an intense electromagnetic wave on a linearly inhomogeneous plasma layer has been analytically investigated. Since the ponderomotive force maximizes near the region where the dielectric constant ε′ → 0, an exact solution of the wave equation is required for a correct estimate of the maximum force. For the case of oblique incidence with the electric vector in the plane of incidence, the solution of the exact wave equation leads to an interesting resonance effect which predicts a force higher than that obtained by earlier workers using a WKB procedure. Physically, this enhanced ponderomotive force arises because of the large nonuniform longitudinal fields that are generated in the region ε′ ≈ 0 for this geometry.
Interaction of an Obliquely Incident p-Polarized Plane Electromagnetic Wave with a Hot Plasma Half-Space
Authors: Bolduc P. E. , Klevans E. H.
Published: February 2004

Reflection and penetration of a p-polarized electromagnetic wave obliquely incident on a plasma half-space is investigated. The perturbed plasma is treated by use of the linearized relativistic Vlasov equation. Electrons are assumed to be specularly reflected from the boundary. The Laplace transform technique, recently employed by Ozizmir, is used to obtain the field solutions in the plasma. These field solutions consist of a transverse and a longitudinal part. Power reflection and transmission coefficients are also obtained.
Resonant Interactions between Particles and Normal Modes in a Cylindrical Plasma
Authors: Kaufman Allan N.
Published: February 2004

A plasma configuration with cylindrical symmetry is studied, containing axial and azimuthal magnetic fields and radial electric field, with arbitrary radial variation. The particle motion is parameterized by three exact action invariants: radial action, canonical angular momentum, and canonical axial momentum; in the limit of small gyroradius they are equivalent to magnetic moment, radial guiding-center position, and parallel velocity. The perturbed Vlasov-Maxwell equations lead to a set of normal modes, which can interact resonantly with the particles. The quantum rate equations for this interaction, together with the laws for conservation of energy, angular momentum, and axial momentum, lead (in the classical limit) to a Fokker-Planck equation in action space for the particles, and to an equation of evolution for mode energy. These coupled kinetic equations satisfy an H theorem, which implies a monotonic approach to a canonical distribution: a rigid-rotor distribution for particles, and a generalized Rayleigh-Jeans distribution for the modes. This asymptotic state may, however, be unconfined. The quantum transition probability is deduced from a classical calculation of emissivity. Explicit expressions are obtained for the mode growth rate and for the particle diffusion tensor. Finally, the Vlasov conductivity kernel is deduced from the growth rates, by the use of the Kramers-Kronig relations.
Experimental Check of the Applicability of Single Born Scattering Theory up to Critical Electron Density Fluctuations
Authors: Richard C. , Ghosh A. K. , Johnston T. W. , Shkarofsky I. P.
Published: February 2004

The results of a theory-experiment comparison of the absolute electromagnetic wave backscatter from a neutral gas dominated turbulent argon arc plasma jet are reported. The study is carried out at 16 GHz, for various aspect angles and covers a range of rms electron density fluctuations extending beyond critical. The backscatter power is measured using a homodyne detection system. The calculation, based on the unmodified Born scattering model, consists of a volume weighting of the turbulent plasma properties, 〈δne2 and S(k), by the antenna illumination. The determination of S(k), the three-dimensional spectral density function, makes use of the measured space-time correlation function and frequency spectrum of electron density fluctuations, Taylor hypothesis, and a three-dimensional MacDonald function analysis. The Born theory is found to describe the backscatter within about 3 dB right up to critical. This result is thought to be due in part to attenuation of the coherent antenna field by large density fluctuations being roughly compensated for, both by decreasing wavenumber and by higher order multiple scattering effects.