FloEFD Heatsink Mesh

Sometimes the temperatures look fine on the fins, but the flow field is patchy or just wrong. The first idea is to refine the mesh, yet no one wants to sit there guessing how many more cells are enough.

FLOEFD has a shortcut called thin-channel mode. It steps in when the gap between two fins is spanned by less than 7 cells. Instead of solving the usual wall functions, it pulls shear-stress and heat-flux values from test data. The result is a fast, steady temperature map that is usually within a few degrees of a full-blown fine mesh.

The switch is automatic. You do not have to count cells by hand; just plot the parameter Thin channel mode (add it from the Boundary Layer group). A value of 1 means the engineering model is active on that wall; 0 means the solver is running full CFD right up to the surface.

Keep the mode on while you only care about how much heat the sink can dump; it saves hours of mesh tuning. Once fan curves, pressure drop, or separation points matter, refine until you have at least ten cells across the channel and let the normal CFD equations take over.

Remember that the cell count is based on the near-wall cell size, not the average. Big cells in the middle of the channel are ignored, so a mesh can still trigger thin-channel mode even if it looks coarse at first glance. Also, if the fins are heavily tapered the gap is no longer seen as a flat channel and the model will not activate—plan on extra refinement from the start.

Use thin-channel mode as a speed tool for thermal sign-off, then swap to a fine grid when the flow details finally count.