Detached eddy simulations an economical tool for CFD

Abstract

Flow field around high speed vehicles is very complex and difficult to simulate. The boundary layers are squeezed between shock layer and body surface. Resolution of boundary layer, shock wave and turbulent regions where the flow field has high values is difficult to capture. DNS and Large eddy simulation (LES) are very good CFD techniques but these are computationally expensive. The latter allows to generate useful solutions to transient flows, while still maintaining computationally realistic problems. Detached eddy simulation (DES) is a modification of a RANS model in which the model switches to a subgrid scale formulation in regions fine enough for LES calculations. Regions near solid body boundaries and where the turbulent length scale is less than the maximum grid dimension are assigned the RANS mode of solution. As the turbulent length scale exceeds the grid dimension, these regions are solved using the LES mode. Therefore the grid resolution is not as demanding as pure LES, thereby considerably cutting down the cost of the computation. In this research study supersonic flow is simulated at Mach 4 and different angle of attacks to calculate aerodynamics characteristics. The results are compared with experimental as well as turbulence model (K-ω SST Model). The results achieved with DES simulation have very good resolution as well as have reasonable agreement with experimental and available data at low cost.