Computational Investigation of Unsteady Compressible Flow over a Fixed Delta Wing Using Detached Eddy Simulation

Unsteady compressible flows over a stationary 60-degree swept delta wing with a sharp leading edge were computationally simulated at different Mach numbers and moderate angles of the attack. An unstructured grid, Spalart-Allmaras Detached Eddy Simulation turbulence model, and a dual-time implicit time integration were used. Vortical flow structures associated with various freestream conditions are displayed and their variations versus time are studied. Variations of flow field parameters, such as u velocity component and pressure coefficient with the flow time are demonstrated at several point probes in the flow field. A Power Spectral Density frequency analysis is performed for such unsteady behaviours to identify the dominant frequencies which exist in each flow condition. The frequency analyses show that low frequencies associated with vortex breakdown oscillation are the most dominant frequencies in all cases where vortex breakdown occurs. Dominant frequencies associated with helical mode instability are also present at the probes downstream of breakdown. Dominant frequencies related to the shear layer instabilities were observed for the low subsonic regime.