I set the localized mesh control for heatsink but the resultant mesh didn't reflect my settings (minimum gap size = gaps between fins). Please seee attachment.
A bit more detail on that. I created a block that covers the volume the heatsink occuped, and I set the local mesh on the block.
Here is from the Flow Simulation Help:
By default, Flow Simulation generates the basic mesh in order to have a minimum of two cells per the specified Minimum gap size. The number of cells per the Minimum gap size non-linearly depends on the Level of initial mesh and cannot be less than two.
From my attachment, there is less than one cell in general between the fins.
I used cut plane to show the mesh.