Quasi-direct current (Q-DC) filamentary electrical discharges are used to control the shock train in a back-pressured Mach 2 duct flow. The coupled interaction between the plasma filaments and the shock train leading edge (STLE) is studied for a variety of boundary conditions. Electrical parameters associated with the discharge are recorded during actuation, demonstrating a close correlation between the STLE position and dynamics. High-speed self-aligned focusing schlieren (SAFS) and high frame-rate color camera imaging are the primary optical diagnostics used to study the flowfield and plasma morphology. Shock tracking and plasma characterization algorithms are employed to extract time-resolved quantitative data during shock–plasma interactions. Four distinct shock–plasma interaction types are identified and outlined, revealing a strong dependence on the spacing between the uncontrolled STLE and discharge electrodes and a moderate dependence on flow parameters.

Quasi-direct-current near-wall filamentary electrical discharges were used to control Mach 2 shock trains within two different geometries. Experiments were conducted over variable flow stagnation conditions and downstream blockage settings. During flow control, the shock train leading edge was observed to transition from a symmetric shock to an asymmetric shock with a reduced normal portion. The control-side leg of the shock train was biased upstream from the opposite leg, becoming anchored at the discharge electrodes. Whether the leg opposite the control-side wall was repositioned upstream or downstream depended on flowpath geometry. Electrical discharge control significantly reduced the pressure gradient through the isolator, which resulted in a decrease in exit pressure. High-speed pressure sensors were used to study the local flowfield at the actuator location. The flow control effectively stabilized the pressure gradient along the isolator wall via the removal of discrete shocks. A continuous wavelet transform analysis revealed that flow control reduced high-amplitude broadband pressure fluctuations while introducing a flowpath-specific 100 Hz mode. Finally, a quasi-one-dimensional model was constructed and indicated that plasma-based control enables a reduction in total pressure losses depending on shock train length.

An adaptive control volume (ACV) is developed to model pseudoshock properties as a function of the backpressure for supersonic internal flows. The formulation accounts for outlet Mach number nonuniformity using two primary independent variables and can be formulated under either attached or separated flow assumptions. The model is applied to a Mach 2 pseudoshock in a rectangular duct with area change and is validated against computational fluid dynamics solutions. Results demonstrate accurate prediction of the area-averaged Mach number and mass-averaged total pressure over a wide range of backpressures. Sensitivity analyses show that the solution is weakly dependent on the nonuniformity parameter once sufficiently large, while the turbulent momentum transport parameter strongly influences total pressure losses. Beyond validation, the ACV model provides insight into pseudoshock physics, permits reliable prediction of outlet quantities using only wall static pressure measurements, and offers potential for low-cost system monitoring and control in high-speed vehicle applications.