Laminar Channel CFD - Three-Mesh Verification

Self-initiated, AI-assisted OpenFOAM v2512 demonstration of steady laminar flow between parallel plates. The model starts from zero fields and uses a prescribed pressure difference. Numerical velocity and flow rate are compared with the analytical Poiseuille solution on 320, 1,280 and 5,120 cells. The finest mesh gives 0.146% velocity RMS error relative to the reference mean speed and 0.195% flow-rate error. Both mesh refinements show second-order velocity accuracy. Mesh checks, field stationarity, inlet/outlet mass balance and cell continuity are documented; residual histories are retained, including the near-zero transverse-velocity residual behavior. Includes a 50 x 10 x 1 mm STEP fluid domain with verified units and round-trip dimensions, a three-page report, plots, runnable source, OpenFOAM cases, CSVs and logs. The 1 mm depth is a 2D extrusion for flow-rate scaling. Numerical verification only: no experimental or client validation, turbulence, thermal coupling, rotating frames or certification. This is not a paid client project.