HEAT TRANSFER TO A SPHERE AT THE TRANSITION FROM FREE MOLECULE FLOW
AVCO EVERETT RESEARCH LAB INC EVERETT MA
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The high speed flow of a rarified gas about a sphere is considered. In such a flow the reflected molecules are moving relatively slowly and form a region near the body whose density is greater than the free stream density. The presence of the denser layer near the body introduces the possibility of collisions with the incident stream which can alter the expected momentum and energy transfer. The important role of surface temperature in these results is noted. For lower surface temperature the emitted particles move away more slowly. By continuity their density is increased and their mean-free path is decreased. This makes scattering events occur closer to the surface and leads to greater breakdown of free molecule flow.