摘要:

Convection, production, diffusion, and dissipation of temperature fluctuations have been measured in the dynamically similar turbulent wake behind an optically heated sphere 136 sphere diameters downstream and at a Reynolds number 4300. The measurements show strong convection and dissipation and moderate diffusion and production. In addition, the dependence of one‐dimensional spectra of temperature fluctuations on wake parameters, intermittency, and the skewness of temperature and velocity derivatives have been measured in a Reynolds number range 1000‐38 000. The skewness of temperature derivative exhibits locally nonisotropic behavior especially at low Reynolds numbers.

ISSN:0031-9171    

DOI:10.1063/1.1694309

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The nature of equilibrium states of inviscid two‐dimensional “turbulence” is discussed. Results of numerical simulations are presented to clarify the theory.

ISSN:0031-9171    

DOI:10.1063/1.1694310

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Two representative spectral energy transfer models of turbulence are tested by comparison with recent numerical simulations of three‐dimensional, homogeneous, isotropic turbulence. Heisenberg's eddy viscosity gives generally good results, while Leith's diffusion approximation is less satisfactory, at least for decay from the Gaussian initial conditions of the computer experiments.

ISSN:0031-9171    

DOI:10.1063/1.1694311

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The structure of the turbulent interface is studied by means of several eddy viscosity models. A detailed analysis results in boundary conditions across the interface. These are applied to the solution of the turbulent Rayleigh shear flow problem.

ISSN:0031-9171    

DOI:10.1063/1.1694312

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Turbulent fluctuation data in a Mach 9.4 boundary layer are presented. Velocity and temperature fluctuations computed from this experiment are not much different from those in the Mach 2‐5 range, but are found to be smaller than the pressure fluctuations.

ISSN:0031-9171    

DOI:10.1063/1.1694313

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The Hamiltonian of a system ofNvortex lines moving in an incompressible fluid contained in a circular cylinder is given. The equilibrium state of vortices is constructed through minimization of the energy of the system with the constraints of constancy of number of vortices and their total angular momentum. One and only one assumption is usedthroughout this work, that pair correlation between vortices is neglected. In equilibrium, the system of vortices rotates uniformly with respect to the central axis of the cylinder. The fluid does not rotate as a solid body, only approaches solid rotation asN→∞. Continuous distribution functions of vortices are found for allN > 1. ForN = 1, the distribution is a delta function at the central axis of the cylinder. AsNincreases the distribution spreads out; in the limitN→∞, it becomes uniform throughout except for a thin layer of orderN−1/2approaching the wall where the density goes to zero rapidly but continuously and remains zero up to the wall. The vortex‐free region next to the wall has a thickness varying from1 − 1/√2forN = 2to1/√Nfor largeN.

ISSN:0031-9171    

DOI:10.1063/1.1694314

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A localized perturbation technique is used to study the stability of a paraboloidal interface. Surface tension effects are considered but viscosity is neglected in the analysis. It is found that instability can occur for certain displacements of the interface. The results of this theoretical analysis are applied to the stability of the interface of a gas jet impinging on a liquid. A linear relationship between the critical jet strength and surface tension is obtained. This agrees with the experimental observations.

ISSN:0031-9171    

DOI:10.1063/1.1694315

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Computations of the breakup length of a liquid jet in a gaseous atmosphere are simplified and accelerated. No approximations need to be made, and the range of the parameters is left unrestricted. Comparison between theory and experiment is made.

ISSN:0031-9171    

DOI:10.1063/1.1694316

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

It is well known that the steady‐state flow of a gas past a solid obstacle immersed in a space filled with isotropic scattering centers can be represented by an integral equation for the collision density distribution. Asymptotic expansions are developed for the gas flux in the form of a power series in the mean free path&lgr;, the leading term representing the continuum diffusion limit. The method replaces the original integral equation with a series of problems, each requiring the solution of a Poisson equation with inhomogeneous terms of increasing complexity. The case of a spherical obstacle of radiusRis treated explicitly; two iterations give the reduction in the flux correct to order&lgr;2. It is found that at moderate&lgr;the sphere acts as though its radius had increased by3&lgr;/16R.

ISSN:0031-9171    

DOI:10.1063/1.1694317

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Experimental observations of the electron temperature profile along a stagnation point streamline have been found to be in good agreement with the theory developed for the case where the interaction between an electron thermal layer and a viscous shock layer was considered. The electron temperature measurements have been carried out with the Langmuir probe technique in an argon plasma flow.

ISSN:0031-9171    

DOI:10.1063/1.1694318

出版商:AIP    

年代:1973

数据来源: AIP