Shock wave propagation across the column of dusted glow discharge in different gases. A.S.Baryshnikov, I.V.Basargin, M.V.Chistyakova Ioffe Physico-Technical Institute Russia

PROBLEM Reducing a drag of air vehicles (due to destabilization and destruction of bow shock wave ), Moreover, Temperature and Heat Flux to surface are dropping!!! Controlling a flight of them, Without great energy deposition TMB

EFFECT OF SHOCK WAVE INSTABILITY DUE TO ENDOTHEMIC REACTION EARLIER: well known instability due to exothermic reaction: detonation combustion. Gas Temperature increases! NOW: Dissociation, Ionization, Excitation of inner degrees of energy. Gas Temperature drops! TMB

Problem When velocity of body riches the amount at which Chemical dissociation (not exothermic reaction) takes the place Just a disturbances on bow shock wave are arising. The flow behind body becomes disturbed in such manner as for turbulent flow. It’s important that such ”turbulence” is outside the wake flow region Flow of the chemically reacting stable polyatomic gases (CF 2 Cl 2 ), TMB

Fig.1. Instability of bow shock wave in front of segmental body. Flow Mach number: М 0 =3,9; Gas: CF 2 Cl 2. Pressure in flow: Р 0 =3,8·10 4 Pа. Wake turbulence Single vortex Disturbance on bow shock wave М 0 =3,9 5 TMB 2010

Fig.2. Instability of bow shock wave in front of segmental body. Flow Mach number: М 0 =6,1; Gas: CF 2 Cl 2. Pressure in flow: Р 0 =4,3·10 4 Pа. М0=6,1М0=6,1 6 TMB 2010

Could! - for Air for high Mach number (2-5) ( Mach number defined to the speed of sound of the uncharged heavy particles) 2. Plasma is active medium! Could energy release to translation freedom degrees? TMB

Behind fast shock wave pressure growth is proportional to  +1 (  –ratio of specific thermo capacities which in plasma is close to 1) Temperature grows much less because its growth is proportional to  -1. Electron concentration arises with temperature much faster but it drops with the pressure growth TMB 2010

in according the Huguenot laws: Derivative will take the form: Equilibrium concentration of binary reaction: equilibrium constant : α TMB 2010

If for any Mach number   will be < than calculation curve, electron concentration will be reducing with rising of M which could correspond to recombination behind shock wave or to the flash of radiation  power index of temperature of preexponential factor in equilibrium constant 3 Mach number Region of instability Cp/Cv in plasma TMB 2010

Here is a stationary plasma of glow discharge. Experiments was made in the installation of electromagnetic shock tube for low transonic Mach number in plasma (hot region) (Mach number is defined to the speed of sound of the slight disturbances of the density of the uncharged heavy particles in hot plasma region) 3. Low speed plasma flow TMB

Installation 1- camera; 2- electromagnetic shock tube (EMST), 3- central electrode of EMST; 4- flanges from organic glass, 5- the anode, 6- cathode; 7- receiver; 8 - rod; 9- piezoelectric pickup; 10- quartz rod; 11- gate of evacuation; 12- pump; 13- gate of gas inlet; 14- manometers. Experimental camera Electromagnetic shock tube piezoelectric pickup PUMP anode TMB

Regimes Maximum of shock wave speed = 2 km/s The gas pressure in camera was 4·10 3 Pa (36 Torr) In experiments we have a time distribution of signal from piezo pickup oriented towards the shock wave (It corresponds to pressure distribution behind the shock wave ) Electrical current in discharge = 1 A up to 2.5A Voltage of discharge = 1 kV up to 10 kV TMB

Usual electron temperature distribution across the positive column of glow discharge /cm 3 Electron temperature has the same profile – plate – 1 eV TMB

Usual gas temperature distribution across the positive column of 1200 K TMB

Signal from piezo pickup without the plasma in hot air (usual triangular form) TMB

Signal from piezo pickup in the plasma (two wave form) TMB

Low dustiness - preliminary results. Dust concentration is about 20 mg per cubic meter, that is comparable with natural concentration TMB

Weak influence of dustiness for the small concentration (in ten times less) of dust ( 20mg in m 3 ; emission of laser as absorbed by 4% ), 2- maximum dustiness (solid gradient line), 1- dustiness is two times lower (dashed line), 0 - without the dust (solid line). in the center of discharge column, the initial velocity of shock wave Is the same 1.6 km/s Air N2 TMB

High dustiness - refined results Dust concentration is about 200 mg per cubic meter Refined: with increased measurement precision by reducingof time discretness at signal recording to order from 200 ns to 20 ns. It enables to average number experiments at each registration point (In this study there was an averaging of 10 experiments). TMB

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1)For carbon dust: Weak influence of dustiness for the small concentration of dust ( 20mg per m 3 ; ), as for Air and for N 2 and Ar 2) BUT! THERE IS INFLUENCE for great concentration( in ten time greater)! 2.1) No influence for Air without plasma 2.2) No appreciable influence in Air plasma 2.3) Great influence for Argon plasma Summary TMB

Further Investigation: A) Strange strong dust dependence on the type of gas B) Dust dependence on the kind of dust C) Dust dependence in course of time after disconnection of discharge TMB

Some part of this work was made under the financial support of Russian Foundation for Basic Research project N а TMB

Thank you very much! TMB