The BGK equation, which is the kinetic model equation of Boltzmann equation, is solved using the technique proposed by Oguchi and Yang to compute the rarefied flow of monatomic gas. Using reduced velocity distribution and discrete ordinate method, the scalar equation is transformed into a system of hyperbolic equations. High resolution ENO(Essentially Non-Oscillatory) scheme based on Harten-Yee's MFA (Modified Flux Approach) method with Strang-type explicit time integration is applied to solve the system equations. Gauss-Hermite quadrature and extended Simpson's rule are used for numerical integration.
The calculated results are well compared with the experimental density field of NACA0012 airfoil, validating the developed computer code. Next, the computed results of circular cylinder flow for various Knudsen numbers are compared with the DSMC(Direct Simulation Monte Carlo) results. The present scheme is found to be useful and efficient for the analysis of two-dimensional rarefied gas flows, especially in the transitional flow regime, when compared with the DSMC method.
