Relative face normal velocity

Purpose

Face fluxes use the relative normal velocity so that grid motion (or a stationary mesh with (v_g=0)) is handled uniformly.

Formula

\[v_n = \mathbf{u}\cdot\mathbf{n} - v_g\]

Source map

  • RelativeFaceNormalVelocity in NsInvFluxPolicy

  • Downstream: FaceMachNumber, Euler/Roe/AUSM face flux assembly

  • Tests: tests/solver/inv_flux_policy_test.cpp

  • Theory table: tools/verification/data/relative_face_normal_velocity_theory.csv

  • Contract Workbench id: relative_face_normal_velocity

Relative normal velocity vs grid speed

What this proves / does not prove

Proves: (v_n=mathbf{u}cdotmathbf{n}-v_g) matches the pure API.

Does not prove: full ALE residual or mesh-motion time accuracy.

References

  • Arbitrary Lagrangian–Eulerian finite-volume formulations.

  • Related: Face Mach number.