natural convection problem
 

Friends, I am trying to solve a natural convection problem in FLUENT (natural convection from a horizontal flat plate) with prescribed wall heat flux.
For the problem I have given the boundary conditions as: left and right control volume: pressure inlet and top control volume pressure outlet, wall prescribed heat flux.The fluid is air with Pr=0.7
After 1300 iterations also my solution is not converging. Kindly help me if possible.