摘要:

The exact solution of the Navier‐Stokes equations originated by von Ka´rma´n is shown to apply even when a stagnation‐point flow is added. The numerical integration is carried through in five special cases, chosen for their relevance to previous work of Ho¨mann, of Hannah, and of Benton as well as the “coffee‐tin experiment” which started the investigation.

ISSN:0031-9171    

DOI:10.1063/1.1694711

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An asymptotic theory is developed for the study of three‐dimensional nonlinear surface waves on an incompressible, viscous fluid with surface tension in an inclined channel of arbitrary cross section. The method used here is based upon a multiparameter singular perturbation scheme within the framework of long‐wave approximation. The nonlinear problem is reduced to a sequence of linear elliptic mixed boundary‐value problems, which may be solved by means of known methods. Their solutions are then used to determine the wave speed and evolution equations governing the nonlinear wave motion. The results obtained give a quantitative description of a three‐dimensinnal bore structure in an inclined channel of arbitrary cross section, and a critical Reynolds number is also defined as a criterion for the instability of the wave motion.

ISSN:0031-9171    

DOI:10.1063/1.1694712

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The theoretical analysis of the velocity distribution within a lenticular liquid filament flowing down an inclined plane is presented. The solution based on a series expansion, whose validity depends on the smallness of the filament's height to width ratio, is compared graphically with an exact numerical solution. The gas‐liquid lenticular interface is determined in such a way that all constants are known directly in terms of measurable physical parameters.

ISSN:0031-9171    

DOI:10.1063/1.1694713

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Results are presented of computer simulations of particle diffusion on a numerically integrated, decaying isotropic turbulent flow field. The diffusion of both fluid particles and “small” spherical particles is studied. Comparisons are made of the various temporal autocorrelation coefficients. It is found that for “short” times, the Lagrangian (fluid point) velocity correlation is larger than the Eulerian correlation, while for longer times the opposite is true. It is also found in the “small” spherical particle case that as the response time of the particle is increased, the velocity autocorrelation coefficient increases.

ISSN:0031-9171    

DOI:10.1063/1.1694714

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Velocity similarity laws based on a four‐layer mean velocity profile model are deduced for turbulent boundary layers with dilute polymer solutions by means of pipe‐flow experiments. Measured drag reduction is found to have three domains: Undersaturated, optimal, and oversaturated. The drag reduction does not increase with increasing concentration in the oversaturated domain where a strong interactive layer dominates the entire logarthmic region of the boundary layer. Drag reduction increases with increasing concentration in the undersaturated domain where the four‐layer profile exists in the boundary layer. The boundary between the two domains gives optimal drag reduction, and is determined by the polymer type and concentration, and by a Reynolds number based on shear velocity and boundary‐layer thickness. Pipe‐flow experiments were made to study the drag‐reduction characteristics in the undersaturated domain. The effects of solvent temperature, pipe diameter, polymer type and concentration, and wall shear stress on the measured drag reduction were investigated.

ISSN:0031-9171    

DOI:10.1063/1.1694715

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The problem of steady supersonic level flight in a stratified and sheared atmosphere is considered. The flow away from the body is shown to be governed by a Burgers‐type equation. Under the inviscid limit exact analytical solutions are obtained showing the effects of shearing, the temperature, and the pressure variation. The solutions are in agreement with all known results under appropriate conditions.

ISSN:0031-9171    

DOI:10.1063/1.1694716

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The phenomenon of one‐dimensional steady condensation of pure vapor at the plane surface of a liquid is considered from the kinetic theory viewpoint. The vapor is treated as a perfect gas without internal degrees of freedom. For the description of this problem the full nonlinear BGK model equation is used. For the solution of the BGK model equation the method of discrete ordinates is applied. The calculations are carried out for water vapor. As a result the temperature and density distributions in the vapor phase are obtained and also for a given temperature difference the net condensation molecular flux rate is determined, depending on the condensation and evaporation coefficients which are treated as parameters.

ISSN:0031-9171    

DOI:10.1063/1.1694717

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Thet−3/2decay of the velocity autocorrelation function has recently been obtained from a non‐Markovian Langevin equation by a number of authors. This approach is extended here to yield the probability distributions for both position and velocity of the Brownian particle. The terms leading to thet−3/2decay in the velocity autocorrelation function are discussed with regard to spatial diffusion.

ISSN:0031-9171    

DOI:10.1063/1.1694718

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A general procedure has been developed for solving the equations governing the electron gas in a breakdown wave. The procedure has been carried out in detail for shock fronted waves. Profiles of the controlling variables are given. A comparison of the calculation of the wave velocity from first principles with the most recent experimental data show excellent agreement even without arbitrary normalization.

ISSN:0031-9171    

DOI:10.1063/1.1694719

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The propagation of subsonic waves supported by laser energy addition is considered. The propagation velocity is modified to account for radiation diffusion by vacuum ultraviolet photons. A simplified two‐band radiation transport model is formulated.

ISSN:0031-9171    

DOI:10.1063/1.1694720

出版商:AIP    

年代:1974

数据来源: AIP