B. V. Postnikov

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.

Plasma Control Of Vortex Flow On Delta-Wing At High Angles Of Attack

Nomenclature AR = wing aspect ratio b = wing thickness Cp = pressure coefficient, (p-p0)/q+1 c = wing root chord length Cxa = drag coefficient Cya = lift coefficient Cza = side force coefficient K = lift-drag ratio, mxa = roll moment coefficient mza = pitching moment coefficients p = static pressure on the model surface Tu = free-stream turbulence level, % of U∞ U∞ = mean free-stream velocity q = dynamic pressure x = vortex breakdown position along the wing chord z = transversal direction along the wing span α = angle of attack χ = delta-wing leading edge sweep angle

Plasma Control of Flow Separation on Swept Wing at High Angles of Attack

Experimental study of separation control on the model of swept wing by means of dielectric barrier discharge plasma was carried out at subsonic flow speed. Surface pressure measurements, flow visualization and hot-wire anemometry data show that global flow separation on the airfoil can be mitigated and controlled by means of plasma actuators. Experimental results were obtained for wide range of angle of attack, flow speed, plasma excitation frequency and power. Several kinds of plasma excitation were tested, including continuous and burst modes. It was found that control efficiency demonstrates strong dependence on duty cycle and frequency of discharge.

Changing the regime of supersonic flow past a rectangular step using gas-permeable inserts

It is experimentally established that gas-permeable inserts arranged in front of a finite rectangular step can reduce the characteristic size of the recirculation region for oncoming flow with Mach numbers within M = 2–5.

Suppressing intensive self-oscillations of shock waves by electric discharge

It is experimentally established that intensive self-oscillations of shock wave fronts, which arise in a supersonic jet impinging onto a solid or permeable obstacle of finite dimensions, can be suppressed under the action of an electric discharge operating at the periphery of the jet.

Electric Discharge Control of Flow Separation on Oblique Airfoil

The possibility of controlling flow separation on an oblique airfoil using dielectric-barrier discharge has been experimentally studied. The experiments were performed at subsonic flow velocities in a broad range of the angle of attack. The results of measurements of the velocity and surface pressure fields and an analysis of the flow patterns show that the application of electric discharge allows the interval of the angles of attack for separation-free flow past the airfoil to be significantly increased. Various discharge regimes have been studied, including those with continuous activation by single voltage pulses with a frequency of 0.5–5 kHz and by pulse trains at a repetition rate of 1–100 Hz. The efficiency of the flow separation control has been studied as dependent on the electrical parameters, frequency characteristics, and position of the discharge relative to the flow separation line.

Electric-discharge control over a vortex flow around bodies of revolution

The key feature of a flow around axisymmetric bodies at large angles of attack is the formation of a conic vortex flow, where a pair of primary vortices dominates (Fig. 1). With an increase in the ratio of the angle of attack α to the half-apex angle θ of the model vertex, the initial attached flow is transformed to a detached flow with the formation of a pair of symmetric stationary vortices. With a further increase in the parameter

Effect of the electric discharge on nonstationary processes during supersonic air and methane jet flow over a flat obstacle

The features of supersonic air and methane jet flows over a flat obstacle, accompanied by an electric discharge, were studied. The flow under consideration is characterized by a number of unsteady effects appearing as oscillations of shock-wave fronts with various amplitudes and frequencies depending on the nozzle-obstacle system configuration and jet gas-dynamic parameters. The oscillation frequency of the bow shock wave increases as the obstacle becomes closer to the nozzle edge and the relative obstacle diameter and the supersonic jet stagnation pressure increase. Initiation of the energy release region at the supersonic jet edge causes a change in the oscillation frequency of the bow shock wave; under certain conditions, it causes a change in the entire shock-wave flow pattern.