Hi, Is it possible to model fairly accurately low reynolds number turbulence of a tall enclosed cavity undergoing buoyancy convection on fluent 6.0/6.1 using the k-epsilon model? Joe

Unfortunately, the answer is "it depends". In some cases it might be OK and in others not. If you go into the transitional regime, all bets are off. You will need to compare your results with test data for some sort of similar condition no matter what you do if you want to concretely confirm your results.