New Strategies for Mitigating the Gray Area in Delayed-Detached Eddy Simulation Models

This paper presents a new approach for mitigating the unphysical delay in Reynolds-averaged Navier–Stokes (RANS) to large-eddy simulation (LES) transition, often referred as gray area, which is common issue hybrid RANS–LES turbulence models such delayed-detached eddy simulation. An existing methodology designed improving LES performance complex flows adapted and tested. based on reducing numerical diffusion critical areas permitting more accurate development of turbulence. The formulation comprises both two-dimensional sensitive velocity gradient model an alternative definition subgrid length scale, are tested individually tandem, compared with other formulations commonly used addressing area. Four test cases examined, flat plate, two variants incompressible backward-facing step, open jet compressible case, all selected expose adverse impact that this study seeks address. Furthermore, proposed changes implemented different codes purpose cross-validation. Encouraging results observed, supporting suitability candidate area kind.