摘要:

The behavior of a nonequilibrium fluid is analyzed on a level intermediate between that of hydrodynamics, where microstructure is totally ignored, and a phase space description, where the completeN‐body problem must be solved. The study of the fluid at this level generally involves solving an appropriate transport equation. For liquids, the primary subject of this investigation, the Fokker‐Planck equation of Kirkwood is accepted as a working model and solutions are found by the methods of Chapman and Enskog and of Grad to terms linear in deviations from local equilibrium. (It is argued, however, for a different form of the pair space force than that suggested by Kirkwood and co‐workers.) The results are similar in form to distributions found with other kinetic models. Variational principles are also considered. It is shown that the one‐ and two‐ particle distribution functions have the property of maximizing the entropy subject to the constraints of given densities and fluxes. Alternatively, these distributions maximize the entropy plus entropy productions in appropriate characteristic times. These variational principles do not depend on the use of the Fokker‐Planck equation but appear to possess general validity.

ISSN:0031-9171    

DOI:10.1063/1.1706037

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A kinetic theory of distribution functions for the condition of subsets of molecules in a classical fluid at two distinct times is developed. The treatment is a natural generalization of the kinetic theories of Yvon, Kirkwood, and Born and Green, and leads to differentio‐integral equations linking distributions forqmolecules and distributions forq+ 1 molecules. A generalization of the usual superposition approximation is suggested to truncate this infinite system of equations. Symmetries and other simple properties of the two‐time distribution functions are explored, and it is shown that the pair correlation that determines inelastic scattering is a reduced form of the two‐body positional distribution function. Explicit distributions are not calculated.

ISSN:0031-9171    

DOI:10.1063/1.1706038

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The theory of harmonic growth for finite‐amplitude sound waves in a nondissipative fluid is discussed. The perturbation analysis of such waves in a dissipative fluid has been extended to higher orders of calculation, so that the location of the maximum of the second harmonic can be ascertained with some accuracy. The results agree well with experimental data. The effective absorption coefficient for finite‐amplitude waves also has been calculated to terms of higher order.

ISSN:0031-9171    

DOI:10.1063/1.1706039

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

It is shown that the Landau collision term is equivalent to the Fokker‐Planck type collision term as derived on the basis of the assumption that binary collisions predominate.

ISSN:0031-9171    

DOI:10.1063/1.1706040

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Recent measurements of the thermal conductivities of all ten possible binary mixtures of the rare gases and of the ternary mixture He&sngbnd;Kr&sngbnd;Xe at 29° and 520°C are compared with theoretical calculations. Three calculations are carried out, based on: (1) rigorous kinetic theory, (2) an approximate formula which uses only conductivities of the pure components, and (3) a new semiempirical formula which also requires knowledge of the conductivity of one composition of binary mixture. The agreement is generally satisfactory and furnishes support for the usefulness and accuracy of the formulas used.

ISSN:0031-9171    

DOI:10.1063/1.1706041

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Analytical solutions are obtained describing the expansion into a vacuum of gas clouds having simple initial configurations. The assumptions employed are free molecular flow and local Maxwellian distribution of velocities initially. By means of a simple transformation in time, equivalence is shown between these solutions and the solutions of some elementary problems in transient heat flow. The initially uniform spherical gas cloud expanding into a vacuum is solved by two methods: (1) by the assumption of free molecular flow; and (2) by programming the conventional equations of gas dynamics. Good agreement is observed between the solutions resulting from the two treatments.

ISSN:0031-9171    

DOI:10.1063/1.1706042

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The stability of an idealized inverted atmosphere is investigated. It is shown that an initial perturbation grows in a manner similar to that found by Taylor for the instability of accelerated fluid surfaces.

ISSN:0031-9171    

DOI:10.1063/1.1706043

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

From recent calculations of the efficiency of rf emission from longitudinal plasma oscillations, and from simple considerations of charge separation in collisionless plasma shocks, it is shown that one can predict a quantitative value for the energy of a type II solar radio burst in agreement with observation. Application of the same methods to the solar corona suggests that the radio spectrum of the quiet sun may be nonthermal below 20 Mc, and that the solar wind may generate at earth as much as a megawatt of power at 1 Mc.

ISSN:0031-9171    

DOI:10.1063/1.1706044

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The propagation of magnetohydrodynamic waves in a compressible fluid is discussed with reference to the ionosphere. An investigation of the damping for a gas of finite conductivity shows that different wave modes may be heavily attenuated in certain directions of propagation. Also, the slow wave of the magneto‐acoustic mode is shown to exhibit preferentially less damping for propagation along the magnetic field lines. An examination of the Hall and electron pressure terms shows that they may be neglected for low enough wave frequencies. The coupling of electromagnetic to magneto‐hydrodynamic waves at a plasma‐vacuum boundary is considered. The coupling coefficient is estimated to be one percent.

ISSN:0031-9171    

DOI:10.1063/1.1706045

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Diffusion effects on the structure of a steady, plane shock in a proton‐electron plasma have been studied using a simplified, two‐fluid, hydrodynamic model in which diffusion is the only shock broadening mechanism. Charge separations occur inside the shock because of the mass difference between protons and electrons. The shock is shown to have electric field and density oscillations as a function of distance through the shock. The peak electric fields are large; the peak electric field inside a weak shock of Mach 1.169 reaches 41 700 v/cm for typical quiescent plasma conditions. The distance in which electric field changes occur is of the order of ten Debye lengths of the quiescent plasma. The present work is limited to shocks of Mach number less than 2.

ISSN:0031-9171    

DOI:10.1063/1.1706046

出版商:AIP    

年代:1960

数据来源: AIP