Combined forced and natural convection in a square cavity is analyzed. Vertical walls are maintained at differnt temperatures and the horizontal walls are adiabatic. The mass flow is induced by a shear force resulting form the motion of th eupper wall combined with buoyancy force due to lateal wall heating. Laminar and two-dimensional flow is assumed and the problem is solved numerically by using the Finite Volume-OOLAmethod. Numerical results are obtained for the Grasof number ranging from 10~2 to 10~7 and th Reynolds number values of 100,400 and 1000. The effect of the Prandtl number, varying from 0.01 to 7.0, is also investigated. The average Nusselt number is reported for differnt values of the above parameters in order to ascertan the relative importance of natural and forced convection. The proper scaling of the heat transfer (Nusselt number) in the differnt asymptotic regions leads to the criterion for the transition from one convec-tion mechanism to another, represented by the Richardson number (Ri) for Pr< 1 and RiPr~1/3 for Pr>1.
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