Microwave energy deposition is a novel method for flow control in high-speed flows. Experiments have demonstrated its capability for beneficial flowfield modification in supersonic flow including, for example, drag reduction for blunt bodies. A fully three-dimensional, time-accurate gas dynamic code has been developed for simulating microwave energy deposition in air and the interaction of the microwave-generated plasma with the supersonic flow past a blunt body. The thermochemistry model includes 23 species and 238 reactions. The code is applied to the simulation of microwave energy deposition in supersonic flow past a hemisphere cylinder. The computed centerline surface pressure is compared with the experiment. The interaction of the microwave-generated plasma with the flowfield structure is examined. Nomenclature c p i = specific heat at constant pressure for species i D = diameter of cylinder E, E o = electric field, maximum electric field H = total enthalpy per unit mass of mixture h o f i = heat of formation of species i at temperature T ref h i = static enthalpy of species i per unit mass of species i h = static enthalpy per unit mass of mixture K k = reaction coefficient for reaction k k = Boltzmann constant, 1:38 10 23 J=K k E = microwave wave number, 2= M = representative mass for ions and neutrals M i = molecular weight of species i, kg=kg mol M i = species i (e.g., M 1 e) M 1 = Mach number m = number of reactions m e = mass of electron N = total concentration of species excluding electrons, cm 3 N e , N crit e = electron concentration, critical electron concentration, cm 3 N i = concentration of species i, cm 3 n = number of species including electrons p = static pressure _ p i k = rate of production of species i from reaction k Fig. 1 Interaction of microwave-generated plasma with cylinder. Fig. 2 Centerline pressure vs time. _ q = rate of heating of gas per unit volume R = universal gas constant, 8314 J=kg mol K T = static (translational) temperature of mixture T e = electron temperature u i = mass-averaged velocity component in i direction V dr = drift velocity x i = Cartesian coordinate Y i = mass fraction of species i, Y i i = i = fraction of h i converted into heating of gas h i = rate of change in enthalpy due to reaction i = 2m e =M " = total energy per unit mass of mixture = wavelength of microwave = rotational relaxation factor, dimensionless e = effective frequency of electron collisions 0 ik , 00 ik
A microwave (MW) plasma channel (filament, plasmoid, and plasma dipole) shows promise for its applications for off-body non-electrode modification of a gas flow (plasma aerodynamics) and in the plasma assisted combustion process. A full-scale study of the plasma channel evolution requires a self-consistent solution of Maxwell's equations, plasma chemical kinetics equations, and gasdynamics equations. An attempt is made to develop a simple electrodynamic (based on the solution of Maxwell's equations) “fast” model for studying the evolution of the plasma channel in conjunction with a fairly complete system of plasma chemical reactions. The model is based on a simplifying assumption about the shape of the channel, which converts a 3D problem into a 1D one. The results of numerical calculations in air within the pressure range P = 20–150 Torr are presented. An experimental study of plasmoid development was carried out to verify the predictions of the model. The calculated results agree well with all available experimental data within the pressure range P = 20–150 Torr. The proposed electrodynamic approach made it possible to reveal (i) the mechanism of self-organization during the development of a MW streamer and (ii) the reason for a sharp decrease in the velocity of its elongation, as well as to obtain relations connecting the main characteristics of the streamer (the amplitude of the electric field in the channel and on its heads, the velocity of ionization waves, and the characteristic scale of their fronts). The proposed model will be useful both for estimating the channel parameters and for deciphering the dynamics of radiation scattered by the plasma dipole. The development of such an approach will allow one to study the evolution of multiplasmoid structures of a high-pressure MW discharge.
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