Accession Number : AD0480131

Title :   A MODEL FOR THE WALL BOUNDARY CONDITION IN KINETIC THEORY.

Descriptive Note : Rept. for 1 Dec 65-15 Jan 66,

Corporate Author : AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS

Personal Author(s) : Epstein, Melvin

Report Date : MAR 1966

Pagination or Media Count : 29

Abstract : To solve the Boltzmann equation for a bounded medium, it is necessary to specify a relation between the distribution functions of the incident and reflected particles at the boundary. In the past, an approximate relation (e. g., assuming specular or diffuse reflection) has been used because of the nonavailability of the exact relation. A model has been developed that retains some of the important features of the exact boundary condition and provides a more realistic boundary condition in an analytically tactable form. The model specifically reflects the dependence on the degree of accommodation of each particle on the velocity with which it impinges on the surface. The general form of the model contains a function that can be determined from experimental data or theoretical calculations. For a selected class of interactions, it has been possible to determine this function without recourse to experimental data. Thermal accommodation coefficients calculated from this form of the model are in good agreement with experimental data. As a result, it is concluded that the model does, in fact, describe the essential physics of gas-solid interactions. Using this model, it is shown that the character of the gas-surface interaction can change significantly between low- and high-speed flow conditions. (Author)

Descriptors :   (*KINETIC THEORY, BOUNDARY VALUE PROBLEMS), WALLS, MATHEMATICAL MODELS, RAREFIED GAS DYNAMICS, SURFACE PROPERTIES, GASES, SOLIDS, BOUNDARY LAYER, FLUID DYNAMICS, GAS FLOW, EQUATIONS.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE