# Control of transitional shock wave boundary layer interaction using surface morphing

The potential of surface morphing techniques, including passive shock control bumps (SCB) and active surface morphing is explored to control transitional shock wave boundary layer interactions (SWBLI). In addition to reduction of the size of the separation bubble, a key objective is to mitigate the low-frequency unsteadiness that can cause detrimental structural response. To this end, three-dimensional flow simulations are performed using direct numerical simulations (DNS) at Mach 2 and Reynolds number based on inflow boundary layer thickness Re_δin = 996. An incident oblique shock at the shock angle of σ = 35 deg and shock strength of p2/p1= 1.4 impinges on a laminar boundary layer that evolves from a Blasius profile. The boundary layer separation due to the shock impingement leads to G ̈ortler-like instability, where the nominally two-dimensional and steady inflow undergoes flow transition, giving rise to a three-dimensional and unsteady interaction. An aero-structural solver framework is developed and employed to examine surface morphing control. To avoid unrealistic structural deformation in the transient or final states, the structural integrity is concurrently monitored so that the intermediate morphing solutions are restricted to achievable elastic deformation. The results indicate that the transitional SWBLI can be controlled in this manner, to essentially eliminate the three-dimensionality and unsteadiness associated with the G ̈ortler-like vortices. Both passive SCB and active surface morphing reduce separation by modulating the sharp increases in surface pressure at separation and shock-impingement points encountered in uncontrolled SWBLI, without incurring additional loss of the stagnation pressure.

The video shows the effect of active surface morphing on the flow transition exhibited in a shock wave boundary layer interaction, in terms of Q criterion isosurface, completely eliminating the flow separation and transition. The vertical axis is scaled for clarity.