Dielectric Barrier Discharge Actuator Research Articles

Geometry optimization of linear and annular plasma synthetic jet actuators

The electrohydrodynamic (EHD) interaction induced in atmospheric air pressure by a surface dielectric barrier discharge (DBD) actuator has been experimentally investigated. Plasma synthetic jet actuators (PSJAs) are DBD actuators able to induce an air stream perpendicular to the actuator surface. These devices can be used in the field of aerodynamics to prevent or induce flow separation, modify the laminar to turbulent transition inside the boundary layer, and stabilize or mix air flows. They can also be used to enhance indirect plasma treatment effects, increasing the reactive species delivery rate onto surfaces and liquids. This can play a major role in plasma processing and chemical kinetics modelling, where often only diffusive mechanisms are considered.This paper reports on the importance that different electrode geometries can have on the performance of different PSJAs. A series of DBD aerodynamic actuators designed to produce perpendicular jets has been fabricated on two-layer printed circuit boards (PCBs). Both linear and annular geometries were considered, testing different upper electrode distances in the linear case and different diameters in the annular one. An AC voltage supplied at a peak of 11.5 kV and a frequency of 5 kHz was used. Lower electrodes were connected to the ground and buried in epoxy resin to avoid undesired plasma generation on the lower actuator surface.Voltage and current measurements were carried out to evaluate the active power delivered to the discharges. Schlieren imaging allowed the induced jets to be visualized and gave an estimate of their evolution and geometry. Pitot tube measurements were performed to obtain the velocity profiles of the PSJAs and to estimate the mechanical power delivered to the fluid.The optimal values of the inter-electrode distance and diameter were found in order to maximize jet velocity, mechanical power or efficiency. Annular geometries were found to achieve the best performance.

Investigation of airfoil leading edge separation control with nanosecond plasma actuator

A thorough combined numerical and experimental investigation of nanosecond dielectric barrier discharge actuation provides a description of the dynamics of the flow actuation process and elucidates the associated flow control mechanisms.

Numerical Study of Nanosecond Pulsed Plasma Actuator in Laminar Flat Plate Boundary Layer

AbstractNanosecond (ns) pulsed dielectric barrier discharge (DBD) actuator in a laminar flat plate boundary layer is investigated numerically in an attempt to gain some new insights into the understanding of ns DBD actuation mechanism. Special emphasis is put on the examination, separation and comparison of behaviors of discharge induced micro shock wave and residual heat as well as on the investigation of response of external flow to the two effects. The shock wave is found to introduce highly transient, localized perturbation to the flow and be able to significantly alter the flow pattern shortly after its initiation. The main flow tends to quickly recover to close to its undisturbed state due to the transient nature of perturbation. However, with the shock decay and final disappearance, another perturbation source in the vicinity of discharge region, which contains contribution from both residual heat and shock, becomes increasingly pronounced and eventually develops into a perturbation wave train in the boundary layer. The perturbation is relatively weak and may not be a Tollmien-Schlichting (TS) wave and not trigger the laminar-turbulent transition of boundary layer. Instead, it is more likely to manipulate the flow stability to achieve the strong control authority of this kind of actuation in the case of flow separation control. In addition, a parametric study over the different electrical and hydrodynamic parameters is also conducted.

Film cooling effectiveness enhancement using surface dielectric barrier discharge plasma actuator

The case presented here deals with the enhancement of film cooling effectiveness using plasma flow control. In this experimental study, a jet is injected from an elongated slot into a thermally uniform cross-flow. The influence of a surface plasma dielectric barrier discharge actuator on heat transfer downstream of the slot is investigated. 2D PIV and IR-thermography measurements are performed for three different blowing ratios of M = 0.4, 0.5 and 1. Results show that the effectiveness can be increased when the discharge is switched-on. Whatever the blowing ratio, the actuator induces a deflection of the jet flow towards the wall, increases its momentum and delays its diffusion in the cross-flow. The best results are obtained with a blowing ratio close to 0.5 and an steady actuation without any frequency modulation.

Electrogasdynamic laminar flow control on a swept wing

The possibility of laminar flow control on a swept wing was theoretically estimated. Calculations of a 3D-compressible boundary layer on an infinite-span swept wing, including a simulation of the volumetric force and heat impact of dielectric barrier discharge (DBD) actuators, were performed. The linear stability of the boundary-layer flow with respect to the stationary modes of the cross-flow-type instability was considered. The position of the laminar-to-turbulent transition was estimated using the eN method. Ultimate assessments of the actuator impact necessary for laminar-to-turbulent transition delay were performed for free-stream parameters corresponding to typical cruise flight conditions of subsonic civil airplanes. A simple new design for a multiple-DBD actuator intended for flow control in a thin boundary layer on a lengthy surface was proposed and studied via parametric experiments.

Simulation of DBD plasma actuator effect on aerodynamic performance improvement using a modified phenomenological model

Abstract An improved phenomenological model is presented for numerical simulation of a Dielectric Barrier Discharge (DBD) plasma actuator for separation control of high angle of attack flow over a wind turbine airfoil. Based on existing numerical models and experimental measurements, a new model is proposed for prediction of the length of a plasma extent which is more consistent with previous observations. The electrical and hydrodynamic solvers used in the present study are validated against published experimental data. Then the applicability of a DBD actuator, mounted on a DU 91-W2-250 airfoil is extensively analyzed for a wide range of operating voltages and frequencies. The analysis is completely repeated for various actuator mounting locations to ensure that results reflect the optimum performance of such a flow control mechanism. It is shown that the best location for the actuator is just before the separation point, which moves upstream as the angle of attack increases. Furthermore, the application of a tandem DBD actuator is also addressed, and among four different locations, the most effective tandem configuration is sought. The improved DBD actuator makes it feasible to have acceptable loadings in low wind velocities.

Wing Flow Separation Control Using Asymmetrical and Symmetrical Plasma Actuator

The effectiveness of asymmetrical and symmetrical plasma actuators for enhancing the aerodynamic performances of a wing has been investigated through the flow separation control experiment in a low-speed wind tunnel. The asymmetrical plasma actuator is a typical single dielectric barrier discharge plasma actuator and induces a one-way airflow. Compared with the asymmetrical dielectric barrier discharge actuator, the symmetrical actuator produced a bidirectional tangential jet. The two actuators were mounted on the leading edge of a wing and oriented along the spanwise direction to produce a body force in the streamwise direction. Force measurements show that the symmetrical actuator can effectively delay the flow separation on the wing at the wind speed up to and has a better control performance than that of the asymmetrical actuator. Particle image velocimetry experiments are carried out to identify the different control mechanisms between the two actuators and highlights how the induced airflows by the two plasma actuators interact with the boundary layer. The induced vortex by the symmetrical plasma actuator is found to be the key element for the better control performance.

Circulation control on a rounded trailing-edge wind turbine airfoil using plasma actuators

This experimental study focuses on the implementation via plasma actuators of a circulation control strategy on a wind turbine aerofoil with a rounded trailing-edge with the objective of reducing the aerodynamic load fluctuations on blades. Three sets of multi-DBD (Dielectric Barrier Discharge) actuators with different positions around the trailing-edge are studied. These actuators create a tangential jet that adheres to the blade model wall and diffuses along it. According to the jet direction, lift is increased or decreased. Load and pressure measurements as well as Particle Image Velocimetry (PIV) show respectively the actuation effectiveness in terms of load modification and flow topology alteration.

Numerical Simulation of Stall Flow Control Using a DBD Plasma Actuator in Pulse Mode

A numerical simulation method is employed to investigate the effects of the unsteady plasma body force over the stalled NACA 0015 airfoil at low Reynolds number flow conditions. The plasma body force created by a dielectric barrier discharge actuator is modeled with a phenomenological method for plasma simulation coupled with the compressible Navier-Stokes equations. The governing equations are solved using an efficient implicit finitevolume method. The responses of the separated flow field to the effects of an unsteady body force in various inter-pulses and duty cycles as well as different locations and magnitudes are studied. It is shown that the duty cycle and inter-pulse are key parameters for flow separation control. Additionally, it is concluded that the body force is able to attach the flow and can affect boundary layer grow that Mach number 0.1 and Reynolds number of 45000.

Numerical Simulation of Flow Separation Control using Multiple DBD Plasma Actuators

A numerical simulation method is employed to investigate the effect of the steady multiple plasma body forces on the flow field of stalled NACA 0015 airfoil. The plasma body forces created by multiple Dielectric Barrier Discharge (DBD) actuators are modeled with a phenomenological plasma method coupled with 2-dimensional compressible turbulent flow equations. The body force distribution is assumed to vary linearly in the triangular region around the actuator. The equations are solved using adual-timeimplicit finite volume method on unstructured grids. In this paper, the responses of the separated flow field to the effects of single and multiple DBD actuators over the broad range of angles of attack ( 9^0-〖30〗^0) are studied. The effects of the actuators positions on the flow field are also investigated. It is shown that the DBD have a significant effect on flow separation control in low Reynolds number aerodynamics.

Improving thrust by pulse-induced breakdown enhancement in AC surface dielectric barrier discharge actuators for airflow control

The characteristics of a plate-to-plate AC surface dielectric barrier discharge (SDBD) actuator using the pulse-induced breakdown enhancing method are experimentally investigated. The encapsulated electrode is supplied with a sine high AC voltage, while the exposed electrode is feed by a synchronized pulse voltage. Based on the thrust force and power consumption measurements, a parametric study was performed using a positive pulse applied at the trough phase of the AC cycles in which the thrust force was observed to increase by about 100% to 300% and the efficiency up to about 100% compared with the AC-only supply conditions for different AC voltages within the tested range. The pulse-induced breakdown effect was analyzed from the electrical and light emission waveforms to reveal the underlying mechanism. The surface potential due to the charge deposition effect was also measured using a specially designed corona-like discharge potential probe. It is shown that the pulse-induced breakdown was able to cause a temporarily intensified local electric field to enhance the glow-like discharge and meanwhile increase the time-average surface potential in the region further downstream. The improvement in the force by the enhancement in the pulse-induced breakdown was mainly due to enhancements in the glow-like discharge and the surface potential increment, with the latter being more important when the AC voltage is higher.

Topological structures of vortex flow on a flying wing aircraft, controlled by a nanosecond pulse discharge plasma actuator

Vortex control is a thriving research area, particularly in relation to flying wing or delta wing aircraft. This paper presents the topological structures of vortex flow on a flying wing aircraft controlled by a nanosecond plasma dielectric barrier discharge actuator. Experiments, including oil flow visualization and two-dimensional particle image velocimetry (PIV), were conducted in a wind tunnel with a Reynolds number of 0.5 × 106. Both oil and PIV results show that the vortex can be controlled. Oil topological structures on the aircraft surface coincide with spatial PIV flow structures. Both indicate vortex convergence and enhancement when the plasma discharge is switched on, leading to a reduced region of separated flow.

Active flow control over a backward-facing step using plasma actuation

Due to the more stringent aviation regulations on fuel consumption and noise reduction, the interest for smaller and mechanically less complex devices for flow separation control has increased. Plasma actuators are currently among the most studied typology of devices for active flow control purposes due to their small size and lightweight. In this study, a single dielectric barrier discharge (SDBD) actuator is used on a backward-facing step to assess its effects on the separated turbulent shear layer and its reattachment location. A range of actuating modulation frequencies, related to the natural frequencies of shear layer instability (flapping) and vortex shedding instability, are examined. The particle image velocimetry technique is used to analyse the flow over the step and the reattachment location. The bulk-flow experiments show negligible effects both on the shear layer and on the reattachment location for every frequency considered, and the actuator is not able to induce a sufficient velocity increase at the step separation point.

Investigation on 3D flow field induced by a plasma actuator with serrated electrode

This paper presents an experimental investigation on flow field induced by a dielectric barrier discharge (DBD) plasma actuator with serrated electrodes in still air to further improve its flow control effectiveness. For comparison, the actuator with widely used linear electrodes was also studied. Experiments were carried out using 2D particle image velocimetry. Particular attention was given to the flow topology, discharge phenomenon, and vortex formation mechanism. Results showed that a 2D wall jet was induced by the linear actuators, whereas the plasma actuators with serrated electrode introduced a series of streamwise vorticities, which might benefit flow control (e.g., enhancing the momentum transport in the separated boundary flow). In addition, the mechanism of 3D flow topology induced by the serrated DBD actuator was analyzed in detail.

Flow control of an elongated jet in cross-flow: Film cooling effectiveness enhancement using surface dielectric barrier discharge plasma actuator

The case presented here deals with plasma flow control applied to a cross-flow configuration, more specifically to a film cooling system. The ability of a plasma dielectric barrier discharge actuator for film cooling effectiveness enhancement is investigated through an experimental set-up, including a film injection from an elongated slot into a thermally uniform cross-flow. Two-dimensional particle image velocimetry and infrared-thermography measurements are performed for three different blowing ratios of M = 0.4, 0.5, and 1. Results show that the effectiveness can be increased when the discharge is switched on, as predicted by the numerical results available in literature. Whatever the blowing ratio, the actuator induces a deflection of the jet flow towards the wall, increases its momentum, and delays its diffusion in the cross-flow.

Dielectric barrier discharge actuator for vehicle drag reduction at highway speeds

We propose and demonstrate reduction of aerodynamic drag for a realistic geometry at highway speeds using serpentine dielectric barrier discharge actuators. A comparable linear plasma actuator fails to reduce the drag at these speeds. Experimental data collected for linear and serpentine plasma actuators under quiescent operating conditions show that the serpentine design has profound effect on near wall flow structure and resulting drag. For certain actuator arrangement, the measured drag reduced by over 14% at 26.8 m/s (60 mph) and over 10% at 31.3 m/s (70 mph) opening up realistic possibility of reasonable energy savings for full scale ground vehicles. In addition, the power consumption data and drag reduction effectiveness for different input signals are also presented.

Numerical Modeling of Dielectric Barrier Discharge Plasma Actuation

A computational method has been developed to couple the electrohydrodynamic (EHD) body forces induced by dielectric barrier discharge (DBD) actuation with unsteady Reynolds-Averaged Navier–Stokes (URANS) model or large eddy simulation (LES) for incompressible flows. The EHD body force model is based on solving the electrostatic equations for electric potential and net charge density. The boundary condition for net charge density on the dielectric surface is obtained from a space–time lumped-element (STLE) circuit model or an empirical model. The DBD–URANS/LES coupled solver has been implemented using a multiple-domain approach and a multiple subcycle technique. The DBD plasma-induced flow in a quiescent environment is used to validate the coupled solver, evaluate different EHD body force models, and compare the performance of the actuator driven by voltage with various waveforms and amplitudes.

Investigation of nanosecond pulse dielectric barrier discharges in still air and in transonic flow by optical methods

In the present study the interaction of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators with aerodynamic flow up to transonic velocities was investigated. The primary focus was on the influence of the flow on the discharge and the effects of the discharge itself. In addition, the influence of the ns-DBD on a shock-wave was studied. The aim was to improve the understanding of the plasma-flow interaction, a topic that is not yet fully understood, in particular for ns-DBD. The actuator was integrated in two different models, a NACA 3506 compressor blade profile and a bump geometry at the bottom of the wind tunnel. The effect of the rapid energy deposition close to the discharge was examined with the phase-locked schlieren visualisation technique. Images of the plasma acquired with short exposure times revealed information on the discharge evolution. The results show a significant effect of the flow on the discharge characteristics, in particular due to the drop of static pressure. On the other hand, no significant effect of the ns-DBD on the flow was observed due to unfavourable flow conditions, which underlines the importance of the actuator’s placement.

Airflow acceleration performance of asymmetric surface dielectric barrier discharge actuators at different exposed needle electrode heights

The use of plasma, created by asymmetric surface dielectric barrier discharge (ASDBD), as aerodynamic actuators to control airflows, has been of widespread concern over the past decades. For the single ASDBD, the actuator performance is dependent on the geometry of actuator and the produced plasma. In this work, a new electrode configuration, i.e., a row of needle, is taken as an exposed electrode for the ASDBD plasma actuator, and the electrode height is adjustable. The effects of different electrode heights on the airflow acceleration behavior are experimentally investigated by measuring surface potential distribution, ionic wind velocity, and mean thrust force production. It is demonstrated that the airflow velocity and thrust force increase with the exposed electrode height and the best actuator performance can be obtained when the exposed electrode is adjusted to an appropriate height. The difference, as analyzed, is mainly due to the distinct plasma spatial distributions at different exposed electrode heights.

Study of electrical characterization and induced flow by nanosecond pulsed dielectric barrier discharge actuator

Focusing on the basic issues of nanosecond pulse dielectric barrier discharge (NS DBD), different actuators are used to investigate the electrical properties, induced flows and shock wave by NS DBD. The results indicate that the coupled energy per unit length is basically controlled by the peak voltage and is nearly independent of the actuator length and the pulse frequency. The peak powers can up to several hundred kW, while the average power for the NS DBD is slightly low, on the orders of W. The very small induced flow velocity of NS DBD is on the order of 0.1 m/s. The compression waves are observed after discharge, initially spread faster than the speed of sound. Phenomenological simulation validates that deposited energy at different levels can bring shock wave propagates at different speed. Deposited energy corresponding to the experiment induces compression wave that propagates close to the speed of sound.