Valery Lashkov

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.

Interaction of Microwave-Generated Plasma with a Hemisphere Cylinder at Mach 2.1

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.

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.

Investigation of Plasma Jets Generated by Quasi -Stationary Magneto -Plasma Compres sor under the High Static P ressu re

Experimental investigations of pla sma jets, generated by Magneto -Plasma Compressor (MPC), operated in the Residual Gas Regime (RGR) in air are performed. It was shown, that MPC in RGR allows to create plasma jets with high penetration ability both in to quiescent gas under the static press ures 30 -90 Torr and in neutral supersonic gas flows with M=2 and static pressure 20 Torr. The velocity of the plasma jet front propagation in quiescent air under the pressure 30 Torr is about 4,3 -4,5 km/s, the Mach number of this jet is estimated as 3,5 -4, 0. The life time of quasi -stationary state of generated plasma jets is about 75 -80 µs. For these experiments, the new construction of MPC was created. It uses the additional disch arge electrode for initiating an auxiliary discharge in the area of critical section of quasi -Laval nozzle of MPC. This discharge allows realize the stable operation of MPC in wide diapason of residual gas pressure with upper level 100 Torr and possibl y more . Results of the presented work demonstrate the possibilities of MPC genera ted jets in applied plasma dynamic s.

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.

Effect of Mach number on the efficiency of microwave energy deposition in supersonic flow

The article is devoted to experimental and numerical studies of the efficiency of microwave energy deposition into a supersonic flow around the blunt cylinder at different Mach numbers. Identical conditions for energy deposition have been kept in the experiments, thus allowing to evaluate the pure effect of varying Mach number on the pressure drop. Euler equations are solved numerically to model the corresponding unsteady flow compressed gas. The results of numerical simulations are compared to the data obtained from the physical experiments. It is shown that the momentum, which the body receives during interaction of the gas domain modified by microwave discharge with a shock layer before the body, increases almost linearly with rising of Mach number and the efficiency of energy deposition also rises.

Investigation of heat flux on aerodynamic body in supersonic gas flow with local energy deposition

Existence and intensive growth of heat flux on a vehicle is one of the main problems in hypersonic flight. Experimental study of heat flux in the stagnation point of a blunt cylinder in supersonic flow was made using gradient heat flux sensor. It was found that a transfer function of the measuring system should be used for obtaining data at fast-changing heat flux measurements. It was established that it was possible to produce a short-term heat transfer from the surface of streamlined body with the help of microwave discharge. Numerical simulation showed that it is possible to change nature of the flow by means of local energy deposition in case of streamlined wedge.Existence and intensive growth of heat flux on a vehicle is one of the main problems in hypersonic flight. Experimental study of heat flux in the stagnation point of a blunt cylinder in supersonic flow was made using gradient heat flux sensor. It was found that a transfer function of the measuring system should be used for obtaining data at fast-changing heat flux measurements. It was established that it was possible to produce a short-term heat transfer from the surface of streamlined body with the help of microwave discharge. Numerical simulation showed that it is possible to change nature of the flow by means of local energy deposition in case of streamlined wedge.

Microwave Energy Deposition in Supersonic Flows on Laser-Initiated Dipole Structures

The results of feasibility study of organization axially-elongated MW discharges in high density supersonic flow (up to atmospheric static pressure) are reported. The laser-ignited structures in test flow are creating with using of double pulse laser. The test flow has Mach number 1,35, static pressure 173 Torr., static temperature 215 K and stagnation temperature300 K. Experimental setup contains the double – pulse YAG laser (2×145 mJ, 10 ns, 532 nm) and microwave system. The last based on impulse high-power magnetron, (3,125 sm, 1.5 mks, peak power 250 KW) and quasi-optical focusing system with axial orientation of electric field. The maximal MW electric field strength on the focus area of focusing system (quasi – optical cylindrical paraboloid) is about 4,6-4,7 kV/sm. This level allows to realize MW discharge in gas flows with static pressure diapason less than 110 Torr. The focusing laser lens has a focus length 23,3 mm and permits to achieve in the focus area the electric field strength (optical diapason) about 7,3*10 6 V/sm. This level is sufficient for laser spark creation in gas with static pressure diapason 760-70 Torr. The first and the second laser pulses could have the tuning time shift. Results of our experiments clearly show that laser initiation technique permits to realize the stable MW energy deposition in high-density supersonic flows (up to atmospheric static pressure) under comparatively weak electrical MW field (substantially less than threshold level for tested flow). This kind of Laser-MW discharge could be realized as to single laser initiation, as for double (dipole, or multipoint) laser initiation. At the last case, the elongation of plasmoid in tested flow could be essentially increased.

Laser-induced MW discharge

In the present work the properties of laser-induced MW discharge was investigated experimentally. For these purpose both Slieren and interferometry techniques has been developed. Laser spark is created by impulse Ruby laser (6943 A, 0.22 J pulse energy and 25 ns-pulse duration) in focal point of short-focus lens (12 mm). This point is placed in the vicinity of the main maximum of MW-field in the focal area of parabolic mirror. The X-range impulse MW generator with output power 180 kW and pulse duration 1,2 μs via radiating system illuminates the focal area. Digital synchronous Schlieren system is used for visualisation of shock wave structures, exciting by laser spark and initiated MW discharge. The temporal evolution of optical density fields for breakdown plasma and thermal well, arising on this place are studied using the high-sensitive intro-chamber Fabry-Perot interferometer. Investigation area of supersonic flow is placed between the interferometer mirrors, which is installed inside the test chamber. In this case the chamber windows are not included in the optical path of the interferometer and it sensitivity for intro-cavity phase objects becomes very high. Intro-chamber plane interferometer Fabry-Perot has fineness about 14, light orifice diameter 86 mm and distance between mirrors 650 mm. Interferometer operates with single - frequency, stabilising (σλ/λ≤10-10)He-Ne laser with output power 1 mW . The interference picture is analysing by the high-sensitive gated (exposition time 1-500 μs) CCD camera.