Experimental and Computational Studies of Low-Temperature Mach 4 Flow Control by Lorentz Force

The paper presents results of cold magnetohydrodynamics flow deceleration experiments using repetitively pulsed, short pulse duration, high-voltage discharge to produce ionization in a M = 4 nitrogen flow in the presence of mutually perpendicular dc electric and magnetic fields transverse to the flow. Effective flaw conductivity is significantly higher than was previously achieved, sigma(eff) = 0.1 S/m, at the magnetic field of 1.5-1.6 T. Magnetohydrodynamics effect on the flow is detected from the flow static pressure measurements. Retarding Lorentz force applied to the flow produces a static pressure increase of 19%, while accelerating force of the same magnitude applied to the same flow results in static pressure increase of 11%. The effect is produced for two possible combinations of the magnetic field and transverse current directions producing the same Lorentz force direction (both for accelerating and retarding force). The results of static pressure measurements are compared with predictions of a 3-D Navier Stokes/magnetohydrodynamics flow code. The static pressure rise predicted by the code, 20% for the retarding force and 11% for the accelerating force, agrees well with the experimental measurements. The simulations show that at the present conditions, the work done by the accelerating Lorentz force is nearly balanced by Joule heating, resulting in nearly zero net velocity change. On the other hand, the two effects are combined for the retarding Lorentz force, which results in approximately 3.8% flow velocity reduction, by Delta u = 25 m/s. This result provides further evidence of the possibility of cold supersonic flow deceleration by Lorentz force.