Shock Boundary Layer Interactions

The interactions of shockwaves with boundary layers, termed Shock-Boundary Layer Interactions (SBLI or SWBLI), are ever-present for vehicles operating in the supersonic regime. Depending on the state of the incoming boundary layer, these interactions can be unsteady and lead to significant thermomechanical loads on the surface of the vehicle. An example of how destructive these interactions can be is shown in the images from an X-15 test flight, were shock-shock and shock-boundary layer interactions significantly damage the body and a control surface of the aircraft at Mach 6.7. To this day, SBLI are a source of uncertainty in vehicle design and interest has grown in interactions with an incoming boundary layer state that is transitional (i.e. boundary layer transition from laminar to turbulent is happening in proximity to the shockwave).

The HORIZON group is currently funded by the Office of Naval Research to perform shock wave/transitional boundary layer interaction research. The goal of the research is to characterize the structure and dynamic behavior, and identify any scaling parameters of the interaction as a function of the incoming boundary layer state. This work uses a variety of diagnostic techniques in our on-campus facilities, and has led to collaborations with Texas A&M University and NASA Langley Research Center. Check out the publications page to see the data resulting from this work.

Surface oil flow visualization of the mean separation structure development of a cylinder-induced shock wave-boundary layer interaction as the boundary layer evolves from laminar to turbulent.

Surface oil flow visualization of the mean separation structure, comparing a cylinder-induced shock wave-boundary layer interaction in a transitional and fully turbulent boundary layer. 

Schlieren animation of a typical cylinder-induced shock wave/transitional boundary layer interaction. Images were captured at 25 kHz.

We extract quantitative data on the shock position and dynamics using an in-house developed MATLAB script. This animation is a demonstration of how it works.

Interaction dynamics and scaling across Schlieren (top), unsteady Pressure-Sensitive Paint (middle), and surface oil flow visualization (bottom). The probability density function of the upstream influence shock and forward shock foot derived from the Schlieren images is also shown.

Shown here is a Mach number contour for a turbulent shock wave-boundary layer interaction simulation using RANS. Separation is overpredicted, resulting in a higher triple point than seen in a turbulent experiment. Secondary vortex structures are relatively small compared to what is expected.