Outflow velocity for SIMPLE algorithm for unsteady forced convection flows with variable density

The SIMPLE algorithm for the pressure-velocity coupling has been adopted by many commercial and non-commercial CFD codes. The SIMPLE algorithm requires all normal velocities at the boundaries before solving the pressure correction equation. These velocities must imply an overall mass balance. In this paper, a new procedure to recalculate the outflow velocity for the Neumann type outflow boundary for forced convection with variable density is proposed. As an example of the utilization of this procedure, the outflow normal velocity of a circular duct was computed and the results were compared with the results using the new modified procedure.