Shock boundary layer interactions in a low aspect ratio duct

Abstract

Experimental data acquired using high resolution two-component particle image velocimetry (PIV) are presented for shock boundary layer interactions (SBLIs) generated by a compression-expansion ramp geometry. The incident oblique shock wave is generated by a sub-boundary layer height ramp inclined 20 • to the M ∞ = 2.05 inflow. Results are presented for two different ramp sizes (h ramp /δ 0 = 0.56 and h ramp /δ 0 = 0.93), and compared to a previously documented h ramp /δ 0 = 0.20 case. For each case, mean velocitiy and turbulent statistics for both the SBLI at the foot of the compression ramp and the incident/reflected SBLI on the opposite wall are analyzed. Data are acquired in several streamwise-vertical planes across the span of the low aspect ratio duct in order to document spanwise non-uniformities and confinement effects, with the specific goal of producing a high quality experimental database for CFD validation. The angles of the incident and reflected shock waves become steeper as the side wall is approached, due to the lower velocities within the side wall boundary layer. Mean flow reversal is observed near the spanwise centerline of the duct, but only instantaneous flow reversal is seen closer to the side walls. These spanwise non-uniformities are more prominent for the stronger interactions caused by the larger ramp geometry. For this case there is no nominally two-dimensional region of the flow, and a Mach stem occurs in the core of the flow, causing a significant subsonic wake. The shock excursion length scale relative to the incoming boundary layer thickness, L ex /δ 0 , is measured for all of the shock features and found to be significantly lower than values reported in the literature for similar flows. Furthermore, L ex /δ 0 for the reflected shock does not depend on the strength of the incident shock or the size of the separated zone.

On the transition between regular and irregular shock patterns of shock-wave/boundary-layer interactions

“…The interaction of shock waves with laminar or turbulent boundary layers (shock-wave/boundary-layer interaction -SWBLI) is thus one of the most prevalent phenomena in high-speed flight and has therefore received much attention in the past few decades (see, for example, the review papers of Dolling 2001 and). Recently, Bermejo-Moreno et al (2014) and Campo & Eaton (2015) investigated experimentally and numerically three-dimensional effects imposed by sidewalls on an oblique shock within a rectangular duct. Their results suggest that confinement effects are responsible for a strengthening of incident and separation shocks, leading to the formation of a Mach reflection that is not observed in the canonical configuration without sidewall boundary layers.…”

Three dimensional CFD investigation of shock train structure in a supersonic nozzle

“…They discussed that, the LES is able to predict the complex flow within the pseudo-shock system reliably and accurately. In addition, a few researchers have examined the controlling conditions of the flow behavior with shock waves [18][19][20][21][22].…”

Sidewall Gap Effects on Oblique Shock-Wave/Boundary-Layer Interactions

“…However, variations in the extent of sidewall interaction exist. For practical reasons of test article movement, some SWBLI studies have employed a small gap between the test article and sidewall [4,[6][7][8], while others (including most numerical investigations due to meshing constraints) perform experiments with full span test articles [5,[9][10][11][12]].…”