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Control of shock-vortex interaction through leading edge blowing
thesisposted on 2021-09-25, 21:59 authored by Francisco Jesus Lozano VazquezFrancisco Jesus Lozano Vazquez
Shock structures such as the bow shock and shock wave-boundary layer interactions (SWBLI) are a major cause of aerodynamic performance abatement and heating in supersonic flows. Which makes them a major concern for designers dealing with aerodynamic bodies in this regime. Furthermore, the leading edge is the most critical point of these bodies as it experiences the highest thermo-mechanical loads. In the present dissertation, a three-dimensional (3D) shock-vortex interaction appearing at the junction of an airfoil geometry bounded by a wall was studied. As well as the implications of applying flow control to it via leading edge injection.
The two-fold character of this interaction was used to divide the appoach in 2 steps: firstly study of the two-dimensional bow shock away from the wall and secondly tackle the full 3D SWBLI. In these 2 phases, a combination of numerical an experimantal tools were employed: steady and unsteady Reynolds-Averaged Navier-Stokes simulations, Detached-
Eddy Simulations and experiments at the PETAL wind tunnel facility. For the 2D bow shock control, a systematic parametric study was carried out, varying the injection boundary conditions, injection slot geometry and frequency during pulsating blowing. Drag and thermal load reductions were achieved thanks to the leading edge injection, together with modification of the shock topology that were reported. The variation of the injection port size allowed the identification of a novel Coanda effect that makes the leading edge flow topology non-symmetric in spite of the perfect symmetry of the problem.
RANS and DES simulations were employed to study the mean and unsteady flow topology of the 3D SWBLI, respectively, both with and without leading edge injection. The effect of flow control on wall variables and flow structures was deeply analyzed, doing it for different thicknesses of the incoming boundary layer. The DES cases allowed to identify the low frequency shock motion for cases with and without flow control, linking it to the breathing mode of the horseshoe vortex system. To complete the analysis of the 3D SWBLI, the same geometries previously studied numerically were experimentally assessed in a newly designed Mach 4 wind tunnel test section. Both static pressure measurements and Schlieren imaging were obtained for the cases with and without leading edge injection. The expected trends and flow structures based on the literature and the previous numerical work were found, with some differences in the size of these structures as predicted by CFD and those found experimentally.