Inverted velocity profiles in rarefied cylindrical Couette gas flow and the impact of the accommodation coefficient

Cylindrical Couette gas flow in the noncontinuum regime has been investigated using the boundary treatment derived from Maxwell's slip-flow model. It is shown that the tangential momentum accommodation coefficient plays an important role in determining the predicted velocity profile. The present analysis is in close agreement with previous analytical studies and shows good qualitative agreement with available direct simulation Monte Carlo data. The results predict the presence of an inverted velocity profile for the case where the inner cylinder rotates and the outer cylinder is stationary. However, our analysis further shows that the phenomenon of velocity inversion is only dependent on the accommodation coefficient of the outer cylinder. From the analysis, we derive specific criteria for the accommodation coefficient of the outer cylinder under which (i) no velocity inversion will take place, (ii) a partially inverted velocity profile will be observed, and (iii) a fully inverted velocity profile will be present. In contrast, when the outer cylinder rotates and the inner cylinder is stationary, it is shown that velocity inversion does not occur. (C) 2005 American Institute of Physics.