摘要:

The Enskog kinetic equation for dense hard sphere gases is analyzed by separating the time reversible and time irreversible parts of the collision operator. The reversible part is responsible for the screening of a weak external potential. The short time behavior of the two‐time density correlation function can be calculated or equivalently, the second‐ and fourth‐frequency moments of its Fourier trans form. The Enskog predictions for the second moment agree with the exact microscopic result of de Gennes to the first power of the density. The disagreement for higher powers of the density can be traced to a fundamental defect of the Enskog collision frequency functional. The exact theory yields an infinite value for the fourth‐frequency moment, in contrast to the finite value predicted by the Enskog equation.

ISSN:0031-9171    

DOI:10.1063/1.1692119

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A general variational principle used to solve various problems in kinetic theory, is now applied to the problem of the flow past an axisymmetric body. It is shown that the drag exerted by the flow on the body is closely related to the stationary value of a given functional.

ISSN:0031-9171    

DOI:10.1063/1.1692120

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The drag exerted by the flow on a sphere is explicitly calculated by using the relation between the drag and a certain functional. A comparison of the results with the experimental data of Millikan gives excellent agreement.

ISSN:0031-9171    

DOI:10.1063/1.1692121

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The stability of pipe Poiseuille flow with respect to linear azimuthally periodic disturbances is investigated. It is found that many radial modes of disturbance exist for each azimuthal periodicity. No linear instability is found for the mode sets with azimuthal periodicity of one.

ISSN:0031-9171    

DOI:10.1063/1.1692122

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

In the presence of a large restoring force, an oscillating convective motion is possible in a thin layer of an elasticoviscous liquid.

ISSN:0031-9171    

DOI:10.1063/1.1692123

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A study of hypersonic viscous interaction on a flat plate is presented. It is shown that the numerical solutions develop singular behavior with respect to the initial data employed. Nonsingular solutions are possible only when a parameter in the initial data is fixed at some specific value which is not knowna priori. The origin of this singular dependence is then investigated. It is found that the problem is improperly set as an initial value problem because the interaction dynamics contain upstream influence. If the problem is attacked as an initial value problem, then a constraint must be placed on the initial flow profiles if a bounded solution is to result. Finally, an approximate numerical method is presented to develop this nonsingular solution for the original system of coupled nonlinear equations.

ISSN:0031-9171    

DOI:10.1063/1.1692124

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The steady Oseen equations for an arbitrary gas are considered. The inverse of the Oseen operator is obtained in closed form uniformly through transonic speeds in a certain limit. This limit is the same as the limit under which the Navier‐Stokes equations are derivable from kinetic theory. The far field flow past an arbitrary body in terms of lift, drag, and energy dissipation of the body is obtained. As another application, the supersonic flow field past a semi‐infinite flat plate is explicity obtained. The latter problem serves as the basis for an extension of the Oseen theory which gives an approximation of skin friction for arbitrary bodies.

ISSN:0031-9171    

DOI:10.1063/1.1692125

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The general theory of structured fluids is discussed from a physical standpoint. Two new physical principles are utilized in developing constitutive equations. Restrictions on the phenomenological coefficients imposed by the second law of thermodynamics are obtained.

ISSN:0031-9171    

DOI:10.1063/1.1692126

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The stability of the interface in the presence of a periodic electric field is considered. It is shown that the stability is governed by a Mathieu equation, that the interface can be unstable even if the electric field is at all times weaker than that needed for instability in the case of a steady field, and that, when instability occurs, the waves may either be synchronous with the electric field, or have twice its frequency.

ISSN:0031-9171    

DOI:10.1063/1.1692127

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The vortex flow of a viscous, incompressible, and electrically conducting fluid confined between two finite flat plates (with a net radial mass flow) in the presence of an applied axial magnetic field is considered. The details of the velocity field including boundary‐layer thickness and redistribution of radial mass flow are of primary concern. The analysis is limited to the case of the separation distance between the two end plates being small compared with the radius of the plates; this allows the momentum equations to be uncoupled from the electromagnetic equations. The momentum equations are linearized and solved for the velocities and the pressure as Fourier series. It is found that magnetic effects tend to decrease the boundary‐layer thickness by a small percentage and tend to decrease substantially the mass flow drawn into the boundary layers.

ISSN:0031-9171    

DOI:10.1063/1.1692128

出版商:AIP    

年代:1968

数据来源: AIP