A high-order hybrid turbulence model with implicit large-eddy simulation

A new hybrid turbulence modelling algorithm combining Implicit Large-Eddy Simulation and Reynolds-Averaged Navier-Stokes has been developed. This variable-resolution algorithm consists of a continuous, non-zonal approach with a hybrid blending function operating at the edge of boundary layers and separated flow regions. This algorithm is informed by an auxiliary transport variable B˜, implemented in a compressible, high-order computational solver Flamenco. The model parameters and the hybrid blending mechanisms are developed for a zero-pressure gradient flat plate boundary layer. Secondly, the flow around a NACA4412 aerofoil in a near-stall configuration is used to evaluate its predictive capability in adverse pressure gradients. Finally, a fully turbulent flow around a circular cylinder at a Reynolds number of Re=1.4×105 is simulated at three different grid-refinement levels. Mean and unsteady results were compared to experimental measurements for validation. Results are critically evaluated against state-of-the-art Detached-Eddy Simulation variants (DES, DDES), Partially-Averaged Navier-Stokes (PANS) and Large-Eddy Simulation (LES). The influence of spanwise sizing, resolution and the choice of an effective characteristic length-scale for the blending functions are discussed. The model responds favourably with increased resolution and also agreed well with the experimental measurements for the wake profiles. Predicted cylinder separation angles were within the expected range, despite the challenges in accurately capturing the recirculation lengths.