Flow Control with Electrohydrodynamic Actuators

Abstract

This work analyses the ability of an electrohydrodynamic actuator to modify the characteristics of a flow over a flat plate. The device considered uses flush mounted electrodes and a d.c. power supply to create a plasma sheet on the surface of the plate. We analyze the mechanism of formation of this plasma sheet, which is shown to be similar to the streamer formation. We show flow visualizations at low flow velocities (≈1m/s) and results from Particle Image Velocimetry at higher flow velocities (range 11.0-17.5 m/s). These results show that the discharge can induce an important acceleration of the flow close to the surface.

Study of the flow induced by a sliding discharge

“…The streamers presence in the inter-electrode gap is mainly the responsible of the luminous aspect of this region. The aerodynamic performances of BED plasma sheet actuators have been reported in previous works for different flow conditions [12][13][14][15][16][17][18]. The main drawback of BED plasma actuators is that the electrical discharge becomes unstable under certain atmospheric conditions.…”

Enhancement of external forced convection by ionic wind

“…Equation (1) shows that the body force is proportional to the ion density and the electric field. Assuming that the ion mobility and cross-sectional area are constant, the current is proportional to the body force and thus proportional to the kinetic energy imparted to the flow  i f KE (16) In turn, kinetic energy is proportional to the square of velocity, and it follows that the velocity is proportional to the square-root of current 2 1 i v  (17) The relationship between heat transfer coefficient and free-stream velocity in external, laminar flows is known analytically [29] 2 1 v h  (18) It follows from these relationships that the heat transfer coefficient due to the ionic wind should be proportional to the fourth-root of the corona current, 1 4  ionic h i . This relationship especially holds true if the current is reasonably large and the primary effect of the ionic wind is to add momentum to the bulk flow, in which case the enhancement is hydrodynamic rather than an electrically induced thermal effect (i.e., the impact of Joule heating on pressure and air properties is small and negligible).…”

“…Soetomo [15], and more recently, Léger et al [16] and Artana et al [17], demonstrated the ability of corona discharges to reduce drag by modulating the boundary layer on a flat plate. Using electrodes perpendicular to the flow and either flush or in contact with a flat plate, they demonstrated a near-wall ionic wind that accelerates the local boundary layer, promoting drag reduction.…”

Supersonic Plasma Flow Control Experiments

“…A number of researchers have exploited EHD forces in subsonic boundary layers on flat plates using glow discharges, 41 and corona discharges. 42,43 Glow discharges have been used to delay separation and enhance lift on airfoils 44,45,46,47 and to trip the boundary layer on 3D airfoils. 48 Wilkinson 49 has explored spanwise-oscillating discharges as a means of reducing Reynolds stress and skin friction in turbulent boundary layers.…”