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Session B01 - Fluids.
session, Monday morning, June 5, 11:00
Urban Room, Westin William Penn Hotel
We have found a convective phenomenon which is neither a hydrodynamic intability like free thermal convection nor macroscopically forced convection. This phenomenon takes place when there is a temperature gradient parallel to a thermalizing wall and it is related to the variation of the temperature field in one mean free path \ell through the adimensional parameter \ell\nabla T/T .
We have made simulations of a two dimensional gas of hard disks in a square box with fixed and different temperatures in the upper and lower walls while in the vertical walls there is an imposed temperature profile identical to the one that stabilices if the vertical walls were periodical. The main observation is that a convective current stabilizes in the neighborhood of the vertical wall moving towards the warmer zone.
This kind of convective motion cannot be derived from the usual frame of NS hydrodynamics because it does not follow from the a priori BCs that one would impose on this problem. The effect of the thermalizing wall is (from a microscopic analysis) to produce a net non trivial velocity field tangential to the wall that provides a new macroscopic BC.