title: Boltzmann equation description of flows at long mean free paths.
abstract: The flow of a gas around a rectangular object is simulated by solving the Boltzmann equation for the gas. The Boltzmann equation is solved by means of a method of characteristics which we refer to as a convective scheme (CS). This paper focuses, first, on two computational issues. We describe how the CS which is presented here is implemented so as to handle reflecting boundary conditions very accurately. Next, a collision operator for the self-collisions of the neutral gas has been developed which conserves momentum and energy "exactly" and which also preserves higher moments of the distribution so as to correctly calculate quantities such as viscosity. Finally, the method is illustrated briefly by calculating flow patterns and drag coefficients for a low Mach-number flow around a rectangular obstacle, over a range of Knudsen numbers which spans the transitional regime, and very accurate values of the drag coefficient are obtained across the whole range.
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53703, USA. fengj@circe.engr.wisc.edu
authors.forename: J
authors.initials: J
authors.lastname: Feng
authors.forename: W N G
authors.initials: WN
authors.lastname: Hitchon