Turbulence LUSGS scalar sweep kernels

Turbulence implicit sweeps treat each equation as a scalar system with face matrix contributions and a cell spectral radius.

\[\Delta F = M\,\Delta q, \qquad \Delta q = r / \lambda\]

Sweep convergence accumulates \((\Delta q-\Delta q_0)^2\).

References

• Yoon–Jameson LUSGS; turbulence scalar implicit practice.

• See lusgs_flux_increment.rst (NS) and turb_spectrum.rst.

Pure APIs: TurbLusgsPolicy.h. Tests: turb_lusgs_policy_test.