Porous Media Flow — Darcy, Forchheimer & Heat Exchangers
Darcy's law, Forchheimer correction, porous zone modeling in CFD, heat exchangers, filters, fuel cells, and catalytic converters.
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Quick Explainer
What is Darcy's law and when does it break down?
Darcy's law: velocity through porous media is proportional to pressure gradient, v = -(k/mu)*dP. Valid at low Reynolds numbers where inertia is negligible. At higher velocities (Re based on pore diameter > ~1-10), inertial losses become significant and the Forchheimer quadratic velocity term is needed.
How do you represent a heat exchanger as a porous zone in system-level CFD?
Rather than meshing every fin and tube, create a porous zone with effective pressure-drop coefficients (from manufacturer data) and effective thermal conductivity or heat transfer coefficient. This macro-scale approach studies airflow distribution across a heat exchanger bank in minutes rather than days.