Calculation of the drag and lift coefficients on a flat plate in a gas in the free molecular regime

Abstract

The present project aims to calculate the drag and lift coefficients on a flat plate in a free molecular rarefied gas flow with zero angle of attack. Firstly, the linearized Boltzmann equation (subsonic regime) will be solved under the assumption of diffuse scattering at the surface, and the physical quantities which determine the coefficients of interest will be calculated as moments of the distribution function of molecular velocities. Subsequently, to analyze the influence of the gas-surface interaction on the drag and lift coefficients, the scattering kernel proposed by Cercignani and Lampis for descrbing the gas-surface interaction will be applied in the boundary condition. In order to consider arbitrary Mach number, the non-linear equation will be solved. The coefficients of interest will be calculated and tabulated as functions of the Mach number and acommodation coefficients of tangential momentum and energy which appear in the gas-surface interaction model applied in the calculations. Moreover, the macroscopic characteristics of the gas flow around the plate, such as bulk velocity, temperature and pressure, will be calculated and their graphical profiles presented.