On the potential of sensitized RANS approaches for unsteady turbulent wall-bounded flows

An improved Scale Adaptive Simulation (SAS) hybrid URANS/LES framework that leverages a sensitized RANS (i.e., k-ε-ξ-f) model to allow for departure-from-equilibrium dynamics is itroduced, primarily to enable the model to transition from URANS to scale resolving mode in attached/mildly separated flows, a known shortcoming of the classical SAS formulations.

Additionally, a transport equation for the length scale of energy-containing eddies is introduced that allows an appropriate transition of length scale from URANS to LES mode. The modified framework is shown to trigger a transition from URANS to LES in stable attached stationary turbulent channel flow and mitigate the log-layer mismatch problem to a great extent. When applied to flows that feature boundary layer separation, i.e., flow over a periodic hill and flow over the wall-mounted hump, the current hybrid framework delivers results in agreement with existing experimental data and comparable to high fidelity LES calculations.