The structure of rarefied gas flows past simple aerodynamic shapes

Abstract

The direct-simulation Monte Carlo procedure for the modelling of rarefied gas flows on a digital computer has been used to generate representations of the simulated flows on a computer display unit. Photographs prepared from the displays illustrate the structure of the flows at the molecular level. The method has been applied to the steady hypersonic flow past circular cylinders, spheres, flat plates and blunt cones. These flows are represented either by several hundred typical molecular paths or by several thousand small arrows, each representing the position and velocity of a sample molecule at a particular instant. Colour was used to differentiate between undisturbed free-stream molecules, molecules that had struck the surface of the body and molecules that had been indirectly affected by the presence of the body. The method was also applied to the flow of a binary gas mixture past a circular cylinder, with colour used to differentiate between the components of the mixture.