摘要:

The potential flow transformation first introduced by Boussinesq is used to transform the generalized Oseen boundary value problem for the heat or mass transfer on a semi−infinite or finite arbitrary symmetric body to an equivalent classical Oseen heat and mass transfer problem for the flow past a semi−infinite or finite flat plate. New and available solutions to this simplified boundary value problem are then used to obtain new heat and mass transfer results for more general boundary shapes. The general formulation is given and new analytic solutions presented for semi−infinite bodies which include the upstream influence of acute angle wedges and blunt half−bodies at uniform surface temperature. Finally a treatment is given of semi−infinite bodies with more varied thermal boundary conditions.

ISSN:0031-9171    

DOI:10.1063/1.861115

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Experimental results concerning secondary flow and torque measurement for low Reynolds number flow in an eccentric spherical annulus are compared with previous theory. The results compare very well, especially for small eccentricities for which the perturbation theory is valid.

ISSN:0031-9171    

DOI:10.1063/1.861116

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The fluctuations of a horizontal fluid layer heated from below are analyzed, based on the hydrodynamic equations in the Boussinesq approximation including thermodynamic fluctuating forces. By means of a formalism, recently developed by Martin, Rose, and Siggia, a system of coupled nonlinear integral equations is derived for a set of correlation functions, response functions, and appropriate ’’self−energies.’’ The equations are solved approximately in several steps of simplification. In addition to results of an earlier linear theory, our results cover a narrow region near the convection threshold, where mode−mode coupling provides the only mechanism of energy dissipation. The fluctuation intensities, and the correlation times and correlation lengths, are calculated in that region. These quantities diverge at the convection threshold in the linearized theory, but remain finite, if mode−mode coupling is taken into account.

ISSN:0031-9171    

DOI:10.1063/1.861117

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Intermittent periods of high momentum transport have been measured in a tidal boundary layer (Re&Vthgr;≈ 2.6×105). The data have been interpreted in terms of the bursting phenomenon reported in laboratory experiments. The experimental period between bursts is consistent with that predicted byT≈k&dgr;*/U∞wherekis the displacement thickness, andU∞is the stream velocity outside the boundary layer.

ISSN:0031-9171    

DOI:10.1063/1.861118

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Theoretical and experimental results are presented which show that the thermal force on an aerosol particle in a temperature gradient depends on the velocity of the particle relative to the gas as well as the temperature gradient in the gas. It is shown that any motion of the particle along a line parallel to the temperature gradient tends to induce a local increase in the temperature gradient and thus an increase in the thermal force. Thermal settling velocity calculations which are made neglecting this motion−induced temperature gradient were found to be as much as fifty percent low when compared with experimental data. Calculations which account for this induced gradient, on the other hand, were able to predict the experimental data within three percent.

ISSN:0031-9171    

DOI:10.1063/1.861119

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The existence of weak shock wave solutions for the higher order theories of gas dynamics generated by the Chapman−Enskog development of Boltzmann’s equation is proved.

ISSN:0031-9171    

DOI:10.1063/1.861120

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A model gas is composed of identical particles with velocities restricted to a given finite set ofpvectors where only binary collisions are considered. The Boltzmann equation is replaced by a system ofpnonlinear coupled differential equations. These equations possess the essential properties of the Boltzmann equation. In particular, the Chapman−Enskog method can be applied. The model with six coplanar velocities is used for the problem of shock structure: The shock structure as given by the associated Navier−Stokes equations is compared with the structure which is known for the exact system. The thickness of the shock structure profile obtained from the associated Navier−Stokes equation is smaller than the thickness obtained from exact equations. These results agree well with those found by other methods.

ISSN:0031-9171    

DOI:10.1063/1.861121

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An analysis is presented relating the radiation intensity time gradient behind shock waves in air to the shock−wave attenuation rate in a shock tube and boundary−layer effects on particle flow time. The analytical results are compared with the experimental data. It is shown that the very large variation of radiation gradient with shock−wave velocity is related to the strong dependency of shocked temperature with shock velocity within the range of 0.6−1.6 cm/&mgr;sec.

ISSN:0031-9171    

DOI:10.1063/1.861122

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The kinetic theory of axially elastic spherocylinder molecules is used for obtaining the shock structure in a vibrationally relaxing diatomic gas. A trimodal and a quadrimodal ansatz are proposed for the distribution function within a shock, and a moment method is used to determine the unknown weight functions in the ansatz. The collision integrals in the moment equations are 22−fold out of which 16−fold integrations are carried out analytically and the remaining integrations are performed numerically using a Monte Carlo technique. The differential equations in the weight functions are solved numerically and shock profiles in nitrogen are obtained for a range of upstream Mach numbers and pressures.

ISSN:0031-9171    

DOI:10.1063/1.861123

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The spatial distribution of free electrons in a stationary, cw, laser−produced air plasma has been measured using single−pulse, two−wavelength holographic interferometry. This measuring technique provided a noncontact method of directly measuring electron density uninfluenced by the other plasma constituents. The general theoretical basis for this type of two−wavelength holography and its application to ionized gases are discussed. Also described are the experimental methods used to implement the technique. Interferograms of the plasma were made at two laser input powers: 3500 W and 6200 W. The electron density was measured as a function of radius and axial position in the plasma, which was oriented vertically to insure cylindrical symmetry. The range of measured values was 1016−1017electrons/cm3for diameters ranging from 0.2 to 0.8 cm.

ISSN:0031-9171    

DOI:10.1063/1.861124

出版商:AIP    

年代:1975

数据来源: AIP