摘要:

It is shown analytically and numerically on the basis of the kinetic theory that the heat‐conduction equation is not suitable for describing the temperature field of a gas in the continuum limit around bodies at rest in a closed domain or in an infinite domain without flow at infinity, where the flow vanishes in this limit. The behavior of the temperature field is first discussed by asymptotic analysis of the time‐independent boundary‐value problem of the Boltzmann equation for small Knudsen numbers. Then, simple examples are studied numerically: as the Knudsen number of the system approaches zero, the temperature field obtained by the kinetic equation approaches that obtained by the asymptotic theory and not that of the heat‐conduction equation, although the velocity of the gas vanishes. ©1996 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.868846

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The energy method, which gives the sufficient condition for the stability, is developed for the convection problem induced by an applied inclined temperature gradient in a shallow horizontal layer. A nonlinear stability analysis, which is valid for any Prandtl number, is carried out for the case of rigid conducting horizontal boundaries. The eigenvalue problem is solved by compound matrix method and the nonlinear stability results are compared with the results of the linear stability method. ©1996 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.868847

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The implications of the eddy‐damped quasinormal Markovian (EDQNM) approximation for the separation of particle pairs in (three‐dimensional) inertial subrange turbulence are explored. In particular the EDQNM equations are solved for the particle separation probability distribution, without making the usual approximation of replacing the damping time scales by their large time asymptotic form. A number of properties of the separation probability distribution that are of significance for the prediction of concentration fluctuations are calculated. The values show quite large departures from the values obtained with the large time form of the damping time scales. ©1996 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.868848

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:1070-6631    

DOI:10.1063/1.869132

出版商:AIP    

年代:1996

数据来源: AIP