2-DIMENSIONAL NUMERICAL-ANALYSIS OF THE POISEUILLE-BENARD FLOW IN A RECTANGULAR CHANNEL HEATED FROM BELOW

The Poiseuille-Benard flow (PBF) is studied by a two-dimensional numer ical simulation for a Prandtl number equal to 6.4 (that of water at 23 degrees C) and for a wide range of Rayleigh (Ra) and Reynolds (Re) nu mbers: Ra less than or equal to 6000 and Re less than or equal to 3. T he two observed how configurations are (1) thermally stratified Poiseu ille flow and (2) thermoconvective transversal rolls superimposed to t he basic Poiseuille how. The time evolution of the velocity components , the spatial development of the transversal rolls, their frequency, w avelength and velocity, the Nusselt number, together with the stabilit y map in the Ra-Re plane, are studied in detail. Whenever possible, qu antitative comparisons are made with published results: most of the ex perimental data, based on laser-Doppler anemometry (LDA), are recovere d with amazing accuracy; a good agreement with results of convective s tability deduced from a weakly nonlinear Ginzburg-Landau theory is als o obtained. (C) 1997 American Institute of Physics.