Study of the unsteady flow around a delta wing at high incidence using detached eddy simulation

We developed an effective Detached Eddy Simulation (DES) method for simulating the vortex breakdown over a delta wing at high incidence. A finite-volume flow solver based on the hybrid unstructured grids was developed to solve the compressible Navier-Stokes equations, and the full implicit dual-time method was introduced to achieve second-order time accuracy. The DES method was modified by replacing the distance to the nearest wall in the wall destruction term by the local grid length in the Spalart-Allmaras turbulence model. This modification makes the Spalart-Allmaras RANS turbulence model act like the standard RANS models in the near wall region and like a Smagorinski LES turbulence model outside of the boundary layer. The unsteady separated flow field around ONERA 70° delta wing at high incidence was simulated by using RANS and DES methods respectively. Comparisons of the numerical results with the results from the references and wind tunnel tests were also presented. Numerical results show that both RANS and DES methods are capable of predicting the vortex breakdown location quite accurately; DES method can capture the complex post breakdown vortex structure correctly, but RANS cannot.