Enhanced delayed detached-eddy simulation with anisotropic minimum dissipation subgrid length scale

Detached-eddy simulation methods are effective for simulating massively separated flows; however, they often predict delayed Kelvin–Helmholtz instabilities, commonly known as the “gray area” issue. Furthermore, their turbulence-resolving capabilities diminish on highly anisotropic grids. This study introduces a novel length scale derived from the anisotropic minimum-dissipation (AMD) subgrid-scale model, which is integrated into the improved delayed detached-eddy simulation (IDDES) framework, resulting in the AMD-IDDES approach. The model is calibrated using decaying isotropic turbulence and a turbulent boundary layer, with validation performed through simulations of decaying isotropic turbulence on anisotropic grids, an axisymmetric near-sonic jet, and a supersonic base flow. The results demonstrate that AMD-IDDES accurately captures eddy dissipation on anisotropic grids and effectively mitigates the “gray area” issue. These improvements stem from the advantages of the AMD subgrid-scale model, derived from a modified Poincaré inequality for anisotropic grids, which enables accurate predictions of Kelvin–Helmholtz instabilities in free shear layers.