Shock Wave Reflection from Plasma Array
Creators: name:  S. LEONOV 
name:   S. ELLIOTT 
name:   P. LAX 
name:   P. ANDREWS 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: FLOW CONTROL
AEROSPACE

description: This work is focused on shock wave - boundary layer interaction (SWBLI), pressure redistribution along a rectangular duct, and dynamics of a supersonic airflow structure under the impact of surface generated, transient energy deposition in a shock-dominated airflow. The power deposition is provided by means of a Quasi-DC electrical discharge [1], which generates a filamentary plasma between flush mounted surface electrodes in a spanwise array. Test arrangement includes a shock wave (SW) generator installed on one wall of the test section and the plasma generator installed on opposite wall. The SW generated from the bottom wall impinges the significantly disturbed boundary layer (BL) generated by the plasma array. The effect of reflected SW mitigation is demonstrated due to the interaction with the plasma-modified BL. The model of interaction is discussed and supported by results of numerical simulations. The experiments were performed in the supersonic blow-down wind tunnel SBR-50 at the University of Notre Dame. The test section is arranged inline with a Mach 2 nozzle. In the current experimental series the conditions were as follows: initial Mach number M=2; total pressure P0 = 1-3 bar; stagnation temperature T0 = 300 K; duration of steady-state aerodynamic operation t = 1-2 s. Instrumentation included pressure sensors, schlieren system, fast camera, and PSP visualization of the SW footprint. The electrical discharge shape appears in the form of a loop of a constricted (filamentary) oscillating plasma connecting the neighboring electrodes. Details of plasma - flow interaction strongly depend on the spatial distribution of discharge energy coupling. The shape of the plasma is controlled by discharge contraction and by convection with the flow [2]. A combination of discharge contraction and convection with the flow results in formation of complex filamentary plasmas. With a high local gas temperature, the multi-filamentary plasma zone presents an array of longitudinal subsonic jets surrounded by a supersonic flow. The volumetrically expanded zone produces a long cone of subsonic flow, where the physical velocity is close to the gas speed in the supersonic core flow. Such an uncommon gasdynamic structure produces a near-surface stratified zone, which enables a significant redistribution of the gas pressure. The important feature of the external SW interaction with the plasma-based displacement layer is that the reflected wedge-based SW is no longer visible or is detected as a very weak compression wave [3]. The pressure measurements prove the effect of the reflected shock mitigation visible on the schlieren images: the pressure peak, caused by an impinging SW, is reduced significantly. The second feature of this type of interaction is that the plasma-related SW is amplified by the impinging SW due to the pressure augmentation in the zone of plasma filaments. This technique demonstrates feasible potential for the control of shock wave boundary layer interaction and, in general, a shock-dominated flows. References [1] A. Houpt, B. Hedlund, S. Leonov, T. Ombrello and C. Carter, \" Quasi-DC Electrical Discharge Characterization in a Supersonic Flow,\" Experiments in Fluids, vol. 58, no. 4, p. 25, 2017. [2] Y. P. Raizer, Gas Discharge Physics, Berlin: Springer, 1991. [3] S. B. Leonov, C. D. Carter, B. E. Hedlund, A. W. Houpt, T. Ombrello and A. A. Firsov, \"Control of Amplitude and Position of Reflected Shock Wave by Stripwise Plasma,\" in Paper AIAA 2018-0683, 2018.