Dmitry Roupassov

SDBD plasma actuator with nanosecond pulse-periodic discharge

This paper presents a detailed explanation of the physical mechanism of the nanosecond pulsed surface dielectric barrier discharge (SDBD) effect on the flow. Actuator-induced gas velocities show near-zero values for nanosecond pulses. The measurements performed show overheating in the discharge region on fast (? 1??s) thermalization of the plasma input energy. The mean values of such heating of the plasma layer can reach 70?K, 200?K and even 400?K for 7?ns, 12?ns and 50?ns pulse durations, respectively. The emerging shock wave together with the secondary vortex flows disturbs the main flow. The resulting pulsed-periodic disturbance causes an efficient transversal momentum transfer into the boundary layer and further flow attachment to the airfoil surface. Thus, for periodic pulsed nanosecond dielectric barrier discharge, the main mechanism of impact is the energy transfer and heating of the near-surface gas layer. The following pulse-periodic vortex movement stimulates redistribution of the main flow momentum.

Nanosecond-Pulsed Discharges for Plasma-Assisted Combustion and Aerodynamics

The efficiency of nanosecond discharges as an active-particle generator for plasma-assisted combustion and ignition has been shown. The kinetics of alkane oxidation have been investigated from methane to decane in stoichiometric and lean mixtures with oxygen and air at room temperature under the action of high-voltage nanosecond unform discharge. The study of nanosecond barrier discharge influence on a flame propagation and flame blowoff velocity has been carried out. A significant increase of the flame blowoff velocity has been demonstrated. A decrease of 2-3 orders of magnitude of the plasma-assisted ignition delay time in comparison with the autoignition has been registered. Detonation initiating by high-voltage gas discharge has been demonstrated. The energy deposition in the discharge ranging from 70 mJ to 12 J for propane-oxygen-nitrogen mixtures leads to the transition to detonation at a distance of less than one diameter of the detonation tube. The influence of pulsed surface dielectric discharge on the flow separation for airfoils at a high angle of attack has been investigated within the velocity range from 20 to 110 m/s for the power consumption less than 1 W/cm of the wing span. The conclusion has been made that the main mechanism of plasma impact is the boundary-layer turbulization rather than acceleration.

Pulsed Discharge Actuators for Rectangular Wing Separation Control

Separation control experiments on a rectangular wing were carried out using dielectric barrier discharge plasma at subsonic speed for chord Reynolds numbers between 0.35 and 0.875·10. Surface pressure measurements and flow visualization show that global flow separation on the wing can be mitigated or eliminated with the plasma actuators. The data were obtained for a wide range of angle of attack, flow speed, plasma excitation frequency and power. New applications of several kinds of voltage pulses for plasma excitation are discussed including microsecond and nanosecond pulses. It was found that control efficiency strong depends on discharge frequency.

Boundary Layer Separation Plasma Control Using Low-Temperature Non-Equilibrium Plasma of Gas Discharge

The influence of pulsed sliding discharge on the flow separation has been investigated. The high efficiency of pulsed discharge was shown within the velocity range from 20 to 110 m/s. The dynamics of discharge propagation with nanosecond time resolution was obtained. The influence of electrodes geometry was investigated. It was found that discharge affects flow separation while the electrodes were placed in parallel to the gas flow so the streamers propagated perpendicular to the flow. The conclusion was made that main mechanism of plasma influence is the boundary layer turbulization.

Development of Nanosecond Surface Discharge in “Actuator” Geometry

Subsequent images of surface nanosecond barrier discharge development were obtained with nanosecond time resolution. Intensified charge-coupled device camera gate was equal to tau = 0.5 ns. The velocities of discharge propagation were obtained, whereas the discharge uniformity and filling ratio of the gap by plasma have been investigated. It was proved that two discharge flashes start during one voltage pulse on the leading and trailing pulse edges.

Hypersonic Flow and Shock Wave Structure Control by Low Temperature Nonequilibrium Plasma of Gas Discharge

Shock wave -non-equilibrium plasma interaction is investigated and analysis of possible gas dynamics drag reduction under such conditions is provided. Experiments with controlled excitation of the translation-rotational and vibration electronic degrees of freedom of the gas by non-equilibrium glow discharge stabilized by gas flow in the hypersonic nozzle and investigations of the possibility of shock wave structure control by non-equilibrium plasma were performed. Stagnation pressure decrease up to 15%was determined for air flow at M=8.2. Temperature measurements shows the temperature increase due to gas excitation in the discharge and internal degrees of freedom relaxation. The conclusion was made that the gas discharge affects the flow mainly by thermal heating in the investigated range of parameters. Calculations support the conclusion about the thermal nature of the shock wave-plasma interaction.

Hypersonic Shock Wave - Low Temperature Nonequilibrium Plasma Interaction

Experimental data on the non-equilibrium plasma gas flow interaction for hypersonic flows and the gas parameters during shock wave non-equilibrium plasma interaction were obtained. The numerical code that describes interaction of the shock wave and non-equilibrium plasma for different mixtures was constructed. Basic factors that determine the interaction process in such a system and the effect of charged and excited particles on the interaction dynamics were revealed. An experimental data for the gas discharge influence on the flow pattern around the model in the wind channel with Mach number M ∼ 8 were obtained. The measurements of the drag force for different gas discharge parameters were performed. The conclusion was made that the gas discharge affects the flow mainly by thermal heating in the investigated range of parameters. Calculations support the conclusion about the thermal nature of the shock wave-plasma interaction.