Reversed flow Natural Convection
 

Hi all,

I am doing the classical 2-D differentially heated cavity to produce natural convection. I am not using the bousinesque approximation, but I am defining density as a function of temperature. When I use air as the working fluid the flow goes backward. Fluid near the hot wall travels downward and fluid near the cool wall travels upward. I can't seem to figure out why. Can anyone help me with this?