Non-intrusive model reduction for open-loop control of shock dynamics in scramjet isolators

Scramjet engines may experience performance degradation and unstart when operating off-design, primarily due to shock-wave/boundary-layer interactions (SWBLI) and combustion-driven instabilities. Recent experiments have shown that open-loop control by means of electrical energy deposition can mitigate instabilities within the scramjet isolator duct through modification of the isolator shock train. We are interested in studying how the actuator placement and input power should be selected to produce a desired shock train configuration. To reduce computational cost relative to solving the full compressible Navier-Stokes equations, we develop a reduced-order model (ROM) to capture the input-output dynamics of the shock-laden flow in response to different actuator configurations. The ROM is constructed using NiTROM (Padovan et al., SIADS, 2024), a non-intrusive model reduction formulation that leverages high-fidelity data to simultaneously compute optimal oblique projection operators and reduced-order dynamics. We then use the ROM to solve the control problem of moving the shock isolator system from its natural state to a target state. This framework is demonstrated on a simple rectangular shock-laden duct fitted with a fixed shock-generating wedge, and a target wall pressure distribution. Our approach reliably predicts the optimal actuator profile while achieving significant computational savings relative to full-order nonlinear control.