Experimental Investigation of Corner Flows in Rectangular Supersonic Inlets with 3D Shock-Boundary Layer Effects

Abstract

In a rectangular supersonic inlet the first oblique shock wave will interact with both the sidewall boundary layers and with the corner flows. This can create large, complex 3-D separation zones that reduce the effective flow area and can lead to the unstart of the inlet. Experiments were conducted in the Michigan Glass Wind Tunnel at Mach 2.75 and at Mach 2.0 to quantify these flow separation patterns. Video was recorded of the unsteady formation of separation zones as the inlet starts. Oil streak patterns and Schlieren images indicate that the downward flow caused by the oblique shock forces some of the flow near the corner to move upstream. This flow moving upstream in the corner creates a sidewall separation bubble, which significantly deflects the free stream upstream of the shock wave. Using a six-degree wedge, a "small" corner flow-shock boundary layer interaction (CF-SBLI) separated region was created which was found to be optimum for CFD simulation. Using a ten-degree wedge generated a stronger shock and a "large" CF-SBLI separated region, but the flow area was reduced so much that the inlet was too close to unstart to allow for stable experimental measurements or CFD simulation.

Relationship Between Intermittent Separation and Vortex Structure in a Three-Dimensional Shock/Boundary-Layer Interaction

“…The flow recirculation structure visualized by the oilflow visualization of a stronger interaction (Mach 2.0, 10 deg deflection SBLI; study by Eagle et al [29]) in the same wind tunnel corresponds to a case of smaller L (owing to larger representative blockage or d caused by the stronger interaction) and is similar to the structure of the vortex cross section observed by Chou and Chao [68] for a case of L 5.33, where they observed no branching. However, no quantitative data are available from the stronger interaction study [29] to confirm the nonexistence of D − D 0 in the case with a stronger interaction.…”

“…Bruce and Babinsky [8], Bermejo-Moreno et al [9], Reda and Murphy [11], Benek et al [13], Helmer et al [17], Burton and Babinsky [26], Eagle et al [29], and Morgan et. al.…”

“…[30] established the importance of the sidewall in three-dimensional low-aspect-ratio duct flows. Previous studies describing the importance of corners in SBLIs have been reported for various configurations, such as those by Bruce et al [12], Burton and Babinsky [26], Eagle et al [29], Batcho and Sullivan [31], and Cresci et al [32], whereas recently, the oilflow studies conducted by Doerffer and Dallmann [33] have given an insight into the flow structure resulting from a shock/corner flow interaction. Reda and Murphy [11] were among the first to note the regions of separations observed near the corners in such flows.…”

Reynolds-stress Budgets in an Impinging Shock Wave/Boundary-layer Interaction

“…Also, it is important to address the fact that the majority of experimental configurations involving compression ramp and incident/reflected shock exhibit some level of corner influence due to corner separation, which renders portions of the flow near corners 3D, while the centerline remains two-dimensional (2D). Due to such a prevalence and coupling, corner influence has become an area of active research as shown by the works of Babinsky et al, 6 Benek et al, 7,8 and Eagle at al., 9 which includes experimental as well as numerical investigations.…”

Turbulence characteristics of supersonic corner flows in a low aspect ratio rectangular channel

“…This design was selected to produce an equilibrium flat plate boundary layer [19] in an attempt to minimize pressure gradients history effects and Görtler vortices on the boundary layer developing on the bottom-wall (floor) of the wind tunnel. Since our previous work has focused on a 3D SBLI configuration and this work is an effort to better understand it, we use the same coordinate system of our previous SBLI work [3,20,21,22]. In particular, the origin of the coordinate system is centered at the location of the leading edge of the full-span 6 o shock generator wedge (which is about 481.5mm downstream of the nozzle throat) used in our previous work on 3D SBLI.…”