A modelling strategy for log-layer mismatch in channel flows
Résumé
In continuous Hybrid RANS-LES (HRL) methods, the switch from RANS to LES is prescribed by a continuous function that reduces the turbulent viscosity, leading to the development of resolved motion, ideally, sufficiently quickly such that the total turbulent stresses (modelled + resolved) are conserved. However, the reliance of developing unsteady motions only due to flow instabilities is too slow which leads to a large deficit in the total mechanical energy and total stresses, which is at the origin of both the modelled stress depletion and log-layer mismatch issues. In this work, a HRL model is augmented with an active forcing strategy such that these effects are diminished. The proposed active methodology can be applied to any continuous HRL model where a function driving the switch between RANS and LES can be identified.