A numerical study is made of mixed convection in a container with a time-dependent inlet throughflow. Numerical solutions are acquires to the governing two-dimensional Navier-Stokes equations for a Boussinesq fluid.
Inertia force is imposed by pumping a vertically-upward throughflow and buoyancy force is generated as the difference in temperature between the wall and the throughflow. Inertia force dominant regime, comparable regime and buoyancy force dominant regime occur as to increasing $Gr/Re^2$.
In practice, $v=v_{in}[1+\epsilonsin(ft)]$ could arise as a result of temporary non-uniformity embedded in the output from the mechanical device to pump the through flow. Where ε is small but non-zero. The effect of a small pulsating in three regimes is investigated.
The numerical results show that in the inertia force dominant regime the resonance of heat flow rate at outlet occurs and depends on reynolds number. in the comparable regime if the forcing frequency is close to the characteristic system brunt-$v\ddot{a}s\ddot{a}ll\ddot{a}$ frequency the resonance of heat flow rate at outlet occurs. In the buoyancy force dominant regime the velocity fluctuations in the interior core are magnified due to internal gravity wave and this behavior is quite insenstitive to the magnitude of ε.
