benard convection

samik

hi all i am trying to model benard convection (2D) in fluent. i am supposed to get the nusselt number ( ratio of heat transfer when the fluid is undisturbed to that of in the instable case) greater than one. to obtain the ratio i first solved the energy eqn without solving the flow eqns and later solved both. but heat transfer rate in the ls later case came much less than the first. so can anyone tell me what is the exact way for getting the nusselt number? thanking you samik