cfd-turbulence-modelinglisted

# CFD Turbulence Modeling (aerodynamics/cfd/cfd-turbulence-modeling) Use when the task is CFD turbulence modeling for a wall-bounded flow: sizing the first cell height with y plus, deriving the friction velocity, and selecting the turbulence model and wall treatment. ## Domain quick reference - The dimensionless wall distance is y+ = y * u_tau / nu, with y in meters, u_tau in m/s, and nu in m^2/s; it measures how far the first cell center sits from the wall in wall units. - The friction velocity u_tau = sqrt(tau_w / rho), with tau_w in Pa and rho in kg/m^3, scales the near-wall velocity profile. - From the skin friction coefficient, u_tau = v_inf * sqrt(cf / 2), with v_inf in m/s. - The target y+ drives the model choice: resolve the viscous sublayer at y+ about 1 (k-omega SST), blend at y+ about 30 (realizable k-epsilon), or use wall functions up to y+ about 300 (SA with wall functions). - NACA Report 824 anchors classic airfoil boundary-layer data used to sanity-check skin friction and transition behavior. ## Workflow 1. Collect y, u_tau, and nu (or tau_w and rho, or cf and v_inf). 2. Compute the y plus value with y_plus. 3. Derive the friction velocity with friction_velocity or friction_velocity_from_cf. 4. Choose the turbulence model with turbulence_model_recommendation. 5. Size the first cell height from the target y+. ## Pitfalls - Targeting y+ about 30 while running a low-Reynolds-number model that needs the sublayer resolved; the model an