Linear stability properties of lifting vortices over delta wings

You are here: Homepage > Search

Linear stability properties of lifting vortices over delta wings

Renac, Florent / Jacquin, Laurent

The purpose of this study is to apply existing theories of linear temporal instability and critical-state concept on realistic delta wing flows. Three-dimensional laser Doppler velocimetry measurements are performed on two delta wings with different geometries in transverse planes both upstream and downstream of the vortex breakdown. Representative models of the velocity fields in the leading-edge vortices are deduced from these measurements and allow us to examine the stability properties of such flows. As expected, helical modes are destabilized downstream of the breakdown with characteristics that agree with generalized centrifugal instability theory for large azimuthal wave numbers. Upstream of the breakdown, the perturbations are stabilized or weakly amplified. Moreover, a simple criticality criterion is shown to efficiently describe the conditions of breakdown in the experiments. These results suggest that inviscid and linear stability analysis based on the mean velocity field is sufficient to account for the linear stability behavior of delta wing flows at high Reynolds numbers.