Olga Azarova

BASICS IN BEAMED MW ENERGY DEPOSITION FO R FLOW/FLIGHT CONTRO L

Present investigation is focused on formulation of valid and realistic physical basis in exploration of the challenging phenomenon in plasma aerodynamics - interference of MW discharge with gas dy namic structures in supersonic flow. We now distinguish three basic phenomena, reflecting the main features of such interference. These phenomena - drag reduction via discharge -induced vortex creation in a shock layer, regular -Mach discharge -induced transi tion in intersecting shocks and radical change in flow separation in streamlining of spike -tipped bodies through discharge -affecting of viscous interaction - cover the most impressive areas of plasma aerodynamics and at the same time form its basis. Each o f these examples demonstrates wide abilities of MW energy deposition method and presents the complicated physics, which is not fully understood yet. Also discharge structure plays a key role in effective interaction with gas dynamic discontinuities. The pa rameters of MW plasmoid internal structure are quantified, the principle of information extraction from spectra of strongly inhomogeneous plasma objects is proposed. Discharge performance requirements are formulated. Beamed energy deposition as a principle tool for plasma aerodynamic phenomena realization seems both claimed and inherent and in general demands application combined MW and laser techniques.

Numerical Prediction of Dynamics of Interaction of Laser Discharge Plasma with a Hemisphere-Cylinder in a Supersonic Flow

The effect of a laser discharge onto supersonic flow past a hemisphere-cylinder at Mach 3.45 is considered. Flow details accompanying supersonic streamlining for three values of energy of a laser impulse 13 mJ, 127 mJ and 258 mJ are simulated numerically on the basis of the Euler equations. The energy deposition is modeled via the combining heated rarefied channels. Complex unsteady vortex contact structures caused by the Richtmyer-Meshkov instability together with a rarefaction wave reflection are shown to be the reason for the reduction of the stagnation pressure. Optimization of the characteristics of the energy sources has been realized taking into account the flow analysis and the comparison of the computational and experimental data. Energy estimations are provided for the three considered parameters of the laser impulse.

Numerical Simulation of Energy Deposition in a Viscous Supersonic Flow Past a Hemisphere

In this work the interaction of a laser-discharged plasma with a hemisphere at Mach 3.45 is simulated by solving the Navier-Stokes equations with the assumption of a viscous perfect gas model and no chemical reaction in the laser discharge. The instantaneous laser discharge creates a plasma region which in this study is assumed to be spherical. From this spherical plasma region a blast wave and an expansion wave form which propagate radially outward and inward, respectively. The heated region convects with the flow and interacts with the blunt body shock in the upstream of the hemisphere and changes the flow structure and parameters in that region. The impact of the blast wave with the hemisphere surface momentarily raises the pressure on the hemisphere. When the heated region reaches the blunt body shock lensing of the shock wave occurs and a toroidal vortex forms due to the Richtmyer-Meshkov instability; as a result, the pressure on the hemisphere drops momentarily. Later on, the flow parameters converge to their steady state condition as the heated region convects to the downstream of the hemisphere. The results are compared with experimental data of Adelgren et al. and our previous study using an inviscid perfect gas model. The peak pressure on the hemisphere due to the impact of the blast wave is matched with the experimental data to estimate the thermal efficiency (i.e., the fraction of the laser discharge energy resulting in heating of the gas). The predicted non-dimensional centerline pressure vs time on the hemisphere is compared with the experimental data and inviscid perfect gas simulation. The objective of this study is to find the effect of viscosity on the flow field structure and the accuracy of the prediction of the flow parameters with this model.

Characterization of Flowfield Types Initiated by Interaction of Microwave Filament with Supersonic Body

Symmetrical and asymmetrical flows accompanying the interaction of a microwave filament (regarded as a heated rarefied channel) and an aerodynamic body in supersonic flow are examined numerically using the Euler equations. Two qualitatively different kinds of flowfields are observed depending on the magnitude of the filament radius, with domination of the large scale pulsations of flow parameters or stochastic phenomena. For the case of asymmetrical filament location relative to the body, the dynamics of drag and lift/pitch forces is presented. Flow modes characterized by periodical steady structures are examined, also. The mechanisms of the formation of these types of flowfield are discussed. The problems are considered in both plane and cylindrical configurations for blunt and pointed bodies and a set of filament characteristics. Freestream Mach numbers are varied from 1.89 to 3.

Flow control via instabilities, vortices and steady structures under the action of external microwave energy release

The details of flow dynamics during the interaction of a microwave filament (regarded as heated rarefied channel) with an aerodynamic body in supersonic flow are considered. Flow control via the effect on the frontal drag force is discussed. The mechanisms of the drag force reduction for a symmetrically located filament and temporary drag force enhancement for an asymmetrically located filament are established. These mechanisms are attributable to the vortex structures forming via the instabilities in front of the body and inside the shock layer. Three kinds of flow instabilities inside the shock layer are analyzed numerically. These are the Richtmeyer–Meshkov instability, the shear layer instability of Kelvin–Helmholtz type and the instability of a flat-parallel tangential discontinuity. The last instability is shown to be accompanied by generation of steady flow structures. A comparative analysis of the resultant vortices and structures is conducted. Limited length and infinite length filaments are considered. The flowfields are investigated for freestream Mach numbers equal to 1.89 and 3, and a wide range of filament characteristics.

Gas -dynamic Effects Around the Body Under Energy Deposition in Supersonic Flow

[Abstract] The paper is devoted to theoretical and experimental investigation of aerodynamic drag of a body when energy release domain appears near the body. The results of numerical modeling on a basis of Euler equations of a thin low -density channel – shock layer interaction for the Mach number 3 of the oncoming flow are presented. New flow structure effects concerning generation and dynamics of shock waves and contact discontinuities have been obtaine d. Dynamics of front drag force, stagnation parameters and bow shock wave coordinate has been researched. Combination of microwave discharge with counter flow and its influence on body’s drag are discussed. Experimental results of interaction of microwave discharge with aerodynamic bodies of different shape (sphere, sphere with a spike) are presented.

Method of Vortex Flow Intensification under MW Filament Interaction with Shock Layer on Supersonic Body

Gas vortex motion caused by the interaction of microwave discharge and shock layer on the body is the principal mechanism, leading to the bodys aerodynamical character istics change. A simplified analysis of gas motion at the beginning of the decay of discontinuity, taking place when the plasmoid contacts the shock layer on the blunted body, is offered. The list of main dimensionless parameters of this motion is discusse d. Energy deposition into the gas during the microwave discharge is evaluated in the experiments. The results of numerical modeling on a basis of Euler equations of a thin limited length low -density channel effect upon supersonic flow past cylindrical AD b ody with complicated cavity are presented. Examination of a possibility to intensify the vortex motion of gas in front of the body with the purpose to manage the latter’s aerodynamic characteristics is presented. Special models, the front surface of which is formed to support gas vortex motion, have been investigated.

Numerical Prediction of Dynamics of Microwave Filament Interaction with Supersonic Combined Cylinder Bodies

The model of microwave (MW) filament is used for consideration of the effect of MW discharge energy deposition on supersonic flows past combined cylinder bodies. Flow details accompanying streamlining bodies “hemisphere-cylinder” and “hemisphere-conecylinder” are simulated numerically for an inviscid perfect gas at Mach 2.1. Attempts for optimization of the shapes and parameters of the area of heated gas resulting from MW energy deposition have been realized taking into account the flow analysis and the comparison with the experimental data. Mechanisms of the stagnation pressure decrease are discussed. Estimations of the value of MW energy needed for generating filaments with the obtained parameters are provided.