Ordinary-differential-equation-based nonequilibrium wall modeling for large-eddy simulation

This paper proposes an ordinary-differential-equation (ODE)-based nonequilibrium boundary layer (NEQBL) wall modeling in large-eddy simulation (LES) for accurate prediction of nonequilibrium separated turbulent boundary layers at a high Reynolds number. The proposed ODE-based wall model does not require computational grids with full connectivity. The key to the modeling is to incorporate the nonequilibrium effects into the pressure-gradient term, convective term, and turbulent eddy viscosity consistently. The model is inaccurate if any of these terms are modeled inconsistently from the others, and it is found important to include the nonequilibrium effects into the turbulent eddy viscosity, which has not been discussed in prior studies. The proposed modeling of the three nonequilibrium terms is first analyzed by a priori tests using the wall-resolved LES (WRLES) database of pressure-induced separated and reattached turbulent boundary layer at Reynolds number Re & theta; & AP; 2.0 x 103. Then, the wall-modeled LES using the proposed ODE-based NEQBL wall model is conducted under the same condition as the WRLES database. The proposed ODE-based NEQBL model yields accurate predictions of the resolved turbulence statistics for both equilibrium-attached and nonequilibrium-separated flows.

Automated summary

This paper proposes an ODE-based NEQBL wall model for accurate prediction of nonequilibrium separated turbulent boundary layers at a high Reynolds number in LES. The model incorporates the nonequilibrium effects into the pressure-gradient term, convective term, and turbulent eddy viscosity consistently. The proposed model is validated using a WRLES database and yields accurate predictions of the resolved turbulence statistics.