ENCLOSURE GAS-FLOWS DRIVEN BY NONISOTHERMAL WALLS

The phenomenon of thermal creep, according to which a rarefied gas wil l ''slip'' at a fluid/solid interface in the presence of appreciable t emperature gradients along the interface, has been previously treated by analytical techniques in the one-dimensional, semi-infinite, linear ized case. The more general problem of multidimensional gas flows at h igh Delta T/T values typically defies analytical or semi-analytical so lution. We employ a direct simulation Monte Carlo method to a hard-sph ere gas in order to study the characteristics of thermal creep convect ive motion in a Cartesian, two-dimensional, confined flow geometry whi ch captures important features of ampoules used in microgravity experi ments on crystal growth. Vortex roll formation is indeed observed in t hese numerical experiments even for zero-gravity conditions, driven by thermal creep at the non-isothermal boundaries and in close resemblan ce to the classical fluid dynamic problem of the wall-driven cavity. ( C) 1995 American Institute of Physics.