Low-temperature supersonic flow control using repetitively pulsed MHD force

The dissertation presents results of the low-temperature supersonic flow experiments using magneto-hydrodynamic (MHD) interaction. The M=3 flow in test section was ionized by a high voltage, short pulse duration, high repetition rate pulsed discharge. Transverse electric current was sustained by transverse DC discharge with the electric field applied in the direction perpendicular to the magnetic field direction.; Operation of a crossed discharge (pulser + DC sustainer) in M=3 flows of air and nitrogen at the pulse repetition rate of 40 kHz demonstrated a stable, diffuse, and uniform plasma. The time-average DC current achieved is up to 1.0 A in nitrogen (electrical conductivity of sigma = 0.073 mho/m) and up to 0.8 A in air (sigma = 0.072 mho/m). Flow temperature in the plasma inferred from the N2(C3piu→B 3pig) emission spectra was T=180+/-20 K. The flow temperatures with and without 1.4 kW DC discharge are very close to each other, indicating that 90% of the input power is stored in the nitrogen vibrational energy mode.; Results of flow visualization using Mie scattering, combined with the results of boundary layer density fluctuation spectra measurements using the Laser Differential Interferometry (LDI) diagnostics, suggest that boundary layer turbulent transition occurs at stagnation pressures of P0∼200-250 torr.; LDI measurements detected an MHD effect on the ionized boundary layer density fluctuations. Retarding Lorentz force applied to M=3 nitrogen, air, and N2-He flows produced an increase of the density fluctuation intensity by up to 2 dB (about 25%), compared to the accelerating force of the same magnitude applied to the same flow.; Static pressure measurements in the MHD section showed that a retarding Lorentz force applied to the flow produced a static pressure increase of up to 17-20%, while accelerating force of the same magnitude applied to the same flow resulted in a static pressure increase of up to 5-7%. The fraction of the discharge input power going into Joule heat in nitrogen and dry air, alpha=0.1, has been inferred from the present experiments.; Results of kinetic modeling of the crossed pulser-sustainer discharge in the presence of transverse magnetic field are also presented. The model predictions are compared with the experimental discharge current-voltage characteristics and time-dependent current traces, both in the absence and presence of magnetic field, showing satisfactory agreement. In the presence of magnetic field, the model predicts electron and ion drift due to Lorentz force in the ExB direction (i.e. in the streamwise direction). This effect creates a mechanism for the neutral species flow acceleration or deceleration by collisional momentum transfer from the ions to the neutrals.; The results of the present work demonstrate feasibility of low-temperature MHD flow control in well-characterized laboratory experiments, for the first time.