Assessment of shielding parameters in conventional DDES method under the presence of alternative turbulence length scales

摘要

Current work investigates the shielding parameters of DES type hybrid methods and their applicability towards turbulence length scales. The accuracy of turbulence length scales available from previous work (SSM length scale) and literature is assessed based on their predictive capabilities in flow involving mild to extensive separation. The simulations are conducted using a compressible, finite volume based GPU accelerated Navier-Stokes solver. A novel shielding formulation is proposed based on the properties of available length scales and the grid requirements in the mildly separated flow. Conventional and the new shielding formulation is tested via static stall flow simulations of the SC1095 airfoil and three-dimensional simulations of S-76 rotor in hover operation. For SC1095 airfoil, two different grids are used to examine the robustness of new shielding with SSM length scale. The combination of new shielding and SSM length scale demonstrated good predictive capabilities in near stall regime for flow over the SC1095 airfoil. The combination also eliminated the need of adverse pressure gradient correction by achieving the reduction in modeled turbulence through SSM length scale definition. S-76 hover simulations demonstrated that new shielding works well in conjunction with laminar-turbulent transition model. New shielding remains robust towards variation in free stream turbulence intensity and provides results comparable to conventional shielding.