Comparison of DES and URANS for Unsteady Vortical Flows over Delta Wings

Abstract

The unsteady behaviour of delta wing vortical flows is still a subject which is a challenge for numerical methods, such as computational fluid dynamics. New approaches to turbulence modelling, such as detached eddy simulation (DES) have been proposed which allow for greater accuracy of the numerical predictions. However, this increase in accuracy comes with a considerable increase in computational expense compared to traditional turbulence modelling. This investigation considers the use of both DES and unsteady Reynolds averaged Navier-Stokes (URANS) turbulence methods in the prediction of unsteady vortical flows. Calculations using DES are initially considered for two test cases and the predicted behaviour and resolution of the flow are considered. These results are then validated against existing experimental data, before the URANS calculations are considered with respect to the DES results. From this investigation it is determined that URANS turbulence models are able to predict the dominant features of the low frequency phenomenon present in the vortex system and in the post-breakdown region. Consideration is also given to the effect of grid refinement for both methods and the effect of temporal resolution for the DES calculations.