摘要:

The heat conduction in binary gas mixtures of monatomic gases between concentric cylinders is investigated theoretically using Maxwell's moment method. By using Maxwell's force law, analytical results are obtained for small temperature differences. The heat conduction coefficient obtained in the present analysis for the continuum region agrees with the Chapman‐Enskog well known result for binary mixtures. In order to check the theoretical results, the heat loss from a fine wire in investigated experimentally for different He‐Ar and He‐Kr mixtures. The measured heat conduction agrees well with the results of the present analysis.

ISSN:0031-9171    

DOI:10.1063/1.1694431

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The nonlinear wave propagation in a high Mach number, low‐density region of a spherically symmetric expanding gas flow is considered. It is well known that classical inviscid gas dynamics is inadequate in describing such flow regimes and consequently the investigation is initiated with Boltzmann's equation. The asymptotic theory describing such a flow has the effect of truncating any order moment equation. This and other simplifications inherent in the approach enable the time dependent moment equations to be integrated and the solutions used in the study of boundary and initial value problems. The theory is applied to the study of a pulse propagating along the centerline of a steady axially symmetric free jet exhausting into vacuum.

ISSN:0031-9171    

DOI:10.1063/1.1694432

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The sharp leading edge problem has been studied for both monatomic and diatomic gases using the Boltzmann equation with the Bhatnagar‐Gross‐Krook type models as the governing equation and the discrete ordinate method with a closed‐boundary value approach as a tool. Plate length relative to the freestream mean free path is taken to be 52. The gas‐surface interaction law is assumed to be diffuse reflection. The local distribution functions of molecular velocities and internal energies (for the diatomic gas) for the entire flow field have been calculated forM ∞ = 6.1; thus, the complete flow field has been determined forTw/T0 = 0.11 and 0.18. Comparisons are made between the calculated results and experimental data. It should be pointed out that the present theory provides a technique to calculate not only gasdynamic variables such as density, flow velocity, pressure, and temperature, but also the nonequilibrium distributions of molecular velocities and internal energies that are very useful in the determination of nonequilibrium radiation intensities.

ISSN:0031-9171    

DOI:10.1063/1.1694433

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A method is developed to reduce the problem of steady relativistic gasdynamics to an equivalent Newtonian flow. The basic theorems, and laws of the steady relativistic gases are established. Numerical studies of the flow fields of a relativistic shock wave, nozzle flow, and Prandtl‐Meyer flow are also presented. The aspects of photon gasdynamics and the basic experiments for the justification of the relativistic photon gas theory are suggested.

ISSN:0031-9171    

DOI:10.1063/1.1694434

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Two kinds of effective collision frequencies are considered for electrons in a gas. They are shown to be useful in the study of various transport properties of electrons. From the best available data on the momentum‐transfer cross section, those effective collision frequencies are calculated and tabulated as functions of the electron temperature for H, He, O, Ne, Ar, Kr, Xe, Cs, Hg, H2, N2, O2, CO, NO, H2O, CO2, N2O, NH3, and CH4. Mobilities and diffusion coefficients obtained from the resulting effective collision frequencies are compared with experimental data.

ISSN:0031-9171    

DOI:10.1063/1.1694435

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The neoclassical plasma transport coefficients for axisymmetric toroidal magnetic confinement systems are calculated in the regime of low‐to‐intermediate collision frequency. The problem of solving the linearized drift kinetic equations, and calculating the transport coefficients, is formulated as a variational principle. A maximal form of the variational principle, which is valid in the low‐to‐intermediate collision frequency regime, is used in a numerical solution of the finite dfiference equations, to obtain the distribution function at points on a mesh in phase space. A new analytical result is used to check the accuracy of the numerical calculation for small collision frequencies; this is a correction to the asymptotic banana regime result, obtained from a Wiener‐Hopf analysis of the boundary layer in phase space between the trapped and untrapped particle regions. An analytical correction to the plateau regime analtyical result is also obtained. The transport coefficients are found to be monotonic functions of collision frequency, with a gradual transition from the banana regime to the plateau regime. Analytical formulas have been fitted to the numerically computed results.

ISSN:0031-9171    

DOI:10.1063/1.1694436

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Some simple one‐dimensional model equations for instability saturation by resonant mode coupling which are of the general form∂u/∂t; + &sgr;1 u ∂u/∂x + M[u] = O, whereM[u] = i/2&pgr;∫ d k &ohgr;(k)∫ d x ′ u(x ) exp [k(x − x′)]are examined theoretically and numerically. For nondispersive&ohgr;(k), it is found the temporal evolution is characterized by the formation and merging of shocks. Also, the level of saturation can depend on the physical size of the unstable system. If disperisive effects are strong, the solution is characterized by the formation of solitons.

ISSN:0031-9171    

DOI:10.1063/1.1694437

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

For a resistive plasma of stellarator or low‐temperature tokamak type, the quasistationary equilibrium is rotating at the reduced sound speedB&thgr;&ngr;th/Bz, and has a slow (acoustic branch) shock fixed in space. Dissipation in the shock can increase plasma loss by an order of magnitude over the Pfirsch‐Schlu¨ter rate. For a very weak shock, the loss rate scales with the resistivity as&eegr;4/3; for a stronger (but still weak) shock, it scales as&eegr;3/2. On the diffusion time scale, flow along the lines of force must develop.

ISSN:0031-9171    

DOI:10.1063/1.1694438

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The ion‐acoustic instability of the helium positive column in the pressure regime 0.05 to 0.25 Torr is studied. Instability of the column is predicted by a kinetic theory which includes the effects of collisions with neutrals, but not by a hydrodynamic theory. In the regime of the experiment the ion‐acoustic instability arises from the resonant interaction of those electrons having velocities close to the phase velocities of the ion‐acoustic waves (inverse Landau damping) even though the electron‐neutral collision frequency exceeds the ion‐acoustic frequency. The helium positive column is well suited to the study of this instability mechanism because the important velocity hierarchy ion thermal velocity≪ion‐acoustic phase velocity≪electron drift velocity≪electron thermal velocity is naturally well established. The detection of the spontaneously excited waves is found to be crucially dependent on the bias of the detecting probe. The onset characteristics, spectral properties, spatial distribution, and saturation intensity are measured and compared with theoretical predictions.

ISSN:0031-9171    

DOI:10.1063/1.1694439

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

From numerical and analytical solutions of the normal mode equation for drift waves in a sheared magnetic field, the critical shearS cfor the onset of instability and the normal mode growth rates at subcritical shear are obtained. At low beta and without a parallel current it is shown that approximately twice the previously indicated shear is required for stability and the(m e / m i)1/3scaling ofS cis confirmed. The addition of a parallel plasma current is shown to increase initially the critical shear quadratically with current and then linearly at larger currents. The effect of electron and ion temperature gradients is studied with equal density and temperature gradients resulting in aproximately a 50% reduction inS c. Finally, the effect of finite beta on the critical shear is studied.

ISSN:0031-9171    

DOI:10.1063/1.1694440

出版商:AIP    

年代:1973

数据来源: AIP