fanPressure Boundary Condition in chtMultiregionSimpleFoam
 

I am tyring to simulate the air flow through a heat sink fin and the thermal distribution inside the fin. My case is set up is as follows (see caseSetup images):

• An inlet supplies the air flow
• The air from the inlet passes through a channel without any obstruction, then the air passes through a heat sink fin (which is heated from the underside), then again pases through a channel without obstruction.
• The air exits the domain from an outlet at the end of the second channel.
• The underside (min_y plane) of the solid region is the heat source
• The z_max and z_min walls are symmetry faces (assuming more fins)
• The y_max and y_min planes for the air region are adiabatic walls.

When I run the simulation using a constant inlet speed, the simulation runs well and the results are in agreement with test results. (see result_ConstantSpeed) However when I define the inlet as a fanPressure BC, then there seems to be no air flow through the domain originating from the inlet. The flow in the result seems to be due buoyancy of the air which gets heated due to the fin (see result_fanBC).

Basic information regarding the case:

• Solver: chtMultiRegionSimpleFoam
• Flow: laminar
• Solid: Aluminum
• Fluid: Air

I am attaching the case files, which include both simulations (different boundary conditions can be defined in the 0/air/p and 0/air/U files by commenting out relevant parts)

Note: I am an electronics engineer with limited fluid dynamics and CFD experience. I have been modifiying tutorials to match my problem so any help directing me in the right direction is welcome.