Dielectric Barrier Discharge Actuator Research Articles

Numerical simulation of the flow around a square cylinder under plasma actuator control

Navier–Stokes computations are performed, and detailed results are documented on the vortex shedding, lift and drag fluctuations, and their spectra for flow past a square cylinder with the Reynolds number ranging from 1 to 300. A body force model for the dielectric barrier discharge (DBD) plasma actuator is used in the Navier–Stokes computations to study the effectiveness of flow control by a pair of the DBD actuators. Three installation configurations of the actuators are investigated. The effects of the actuator location, actuator input power, and the flow Reynolds number are studied. In the first case, two actuators have been installed on the top and bottom of the cylinder. In the second case, two actuators are installed on the front surface. In the last case, two actuators are installed on the rear surface. It is discovered that the best flow control effect is achieved in the last case. Both the unsteady vortex shedding and the average drag can be significantly reduced by the plasma actuators. Under best conditions, the vortex shedding in the wake can be completely suppressed.

Nanosecond dielectric barrier discharge on a curved surface in atmospheric air: streamer evolution and aerodynamic perturbations

A curved nanosecond-pulsed dielectric barrier discharge actuator is proposed to fit the flexibly complex surface shape of air vehicles. Streamer evolution and aerodynamic perturbations driven by a single-pulse voltage applied on the anode, where the pulse width is 35 ns and the peak voltage is 14 kV, are numerically studied. Continuity equations that consider 15 species and 34 reactions are solved based on the drift–diffusion approximation. The electron temperature is obtained using the local mean energy approximation method. Discharge characteristics during the voltage-rise, plateau and decay stages are discussed, respectively. The streamer is initiated at 2.2 ns. The maximum electric field is progressively located at the head of the streamer, between the electrodes and in the dielectric layer during the three voltage stages, while the maximum value of electron density is settled at the downstream tip of the driven anode. The electron number density at the streamer head increases at the voltage-rise stage, keeps constant during the voltage-plateau stage, decreases at the beginning of the voltage-decay stage and then increases due to the quenching effect of the excited species. Compared with the discharge on a flat surface, the initial discharge propagation velocity is smaller, while it decreases more slowly during the entire applied voltage. The simulated deposited energy matches the analytical solution well. Aerodynamic perturbations are investigated by solving the compressible Navier–Stokes equations. The ambient air is rapidly heated to the maximum temperature of 1883 K within 0.04 μs. The temperature rise remains greater than 1000 K for 0.32 μs and greater than 500 K for 21.6 μs. A ‘semiring-like’ compression wave is formed from the discharge region; the propagation speed decreases as it propagates away from the wall and then converges to 345 m s−1 at 13 μs. High-speed flows are rapidly induced at the beginning, and two vortexes are formed successively due to the interaction between the flow induced by the actuator and the backflow induced by the compression wave.

Investigation on Supersonic Flow Control Using Nanosecond Dielectric Barrier Discharge Plasma Actuators

In this paper, the effects of streamwise Nanosecond Dielectric Barrier Discharge (NS-DBD) actuators on Shock Wave/Boundary Layer Interaction (SWBLI) are investigated in a Mach 2.5 supersonic flow. In this regard, the numerical investigation of NS-DBD plasma actuator effects on unsteady supersonic flow passing a 14° shock wave generator is performed using simulation of Navier-Stokes equations for 3D-flow, unsteady, compressible, and k ‐ ω SST turbulent model. In order to evaluate plasma discharge capabilities, the effects of plasma discharge length on the flow behavior are studied by investigating the flow friction factor, the region of separation bubble formation, velocity, and temperature distribution fields in the SWBLI region. The numerical results showed that plasma discharge increased the temperature of the discharge region and boundary layer temperature in the vicinity of flow separation and consequently reduced the Mach number in the plasma discharge region. Plasma excitation to the separation bubbles shifted the separation region to the upstream around 6 mm, increased SWBLI height, and increased the angle of the separation shock wave. Besides, the investigations on the variations of pressure recovery coefficient illustrated that plasma discharge to the separation bubbles had no impressive effect and decreased pressure recovery coefficient. The numerical results showed that although the NS-DBD plasma actuator was not effective in reducing the separation area in SWBLI, they were capable of shifting the separation shock position upstream. This feature can be used to modify the structure of the shock wave in supersonic intakes in off-design conditions.

Flow Characteristics of Dielectric Barrier Discharge Plasma Actuator Array in Burst Mode

To understand the fundamental physics of dielectric barrier discharge (DBD) actuator array for flow control, the flowfield induced by two successive DBD actuators is investigated under burst-mode actuation. The vortical structures generated by the actuators are revealed using particle image velocimetry (PIV) and high-speed schlieren visualization, allowing their interactions to be explored. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) are used to analyze the plasma-induced flow. Both POD and DMD modes indicate staggered vortical structures, whose dynamic features are associated with the burst frequency of the DBD actuation and its harmonics. The POD–DMD coherence indicates that the most relevant dynamic structure is also the most energetic. Spatial DMD analysis reveals an increase in the convection speeds of the flow structures from the upstream DBD actuator to the downstream DBD actuator. The effects of duty cycle and burst frequency on the coherent structures are explored. For different duty cycle cases, the most energetic mode structures evolve in a similar fashion. As the burst frequency increases, the size of the coherent structures decreases, but their number increases. Both POD and DMD analyses reveal that the burst frequency has a greater effect on the coherent structures than the duty cycle.

Empirical relations for discharge current and momentum injection in dielectric barrier discharge plasma actuators

Dielectric barrier discharge (DBD) plasma actuators with an asymmetric, straight edge electrode configuration generate a wall-bounded jet without moving parts. Mechanistic description of the interaction between the Coulombic forces and fluid motion as a function of DBD parameters remains unclear. This paper presents an experimental investigation of DBD actuators, including electrical current associated with microdischarges, plasma volume and the wall jet momentum over a range of alternating current (AC) frequencies (0.5–2 kHz) and peak-to-peak voltages up to 19.5 kV. Discharge current is measured with a high temporal resolution, plasma volume is characterized optically and the momentum induced by the DBD wall jet is computed based on the axial velocities measured downstream of the actuator using a custom-built pitot tube. Discharge current analysis demonstrated asymmetry between the positive and negative semi-cycle; both currents yielded a power–law relationship with empirical fitting coefficients. Plasma length varies linearly and volume quadratically with voltage. Although plasma length reached an asymptotic value at a higher frequency, the plasma volume grows due to the increasing height of the ionization region. In a simple two-dimensional configuration, the DBD wall jet momentum shows near-linear dependency with discharge current in the range of voltages and frequencies considered in this work. The presented empirical model characterizes the DBD wall jet momentum and the discharge current based only on the AC inputs. With the estimation of plasma volume, the model can be applied for determining more realistic boundary conditions in numerical simulations.

Performance enhancement of single dielectric barrier discharge flow control actuators by means of rear linking tunnels on a reference bluff body using CFD

This paper studies drag reduction on a reference bluff body (Ahmed body) with single dielectric barrier discharge (SDBD) actuators, also called plasma actuators, located at different positions on the model’s rear part with a spanwise arrangement. This active actuator modifies the laminar-to-turbulent transition leading to reattachments of separated flows on the body. A reduction of actuator efficiency when increasing velocity is the main limitation of this method. The main aim of this work is to find a solution for this problem by employing passive flow control to improve the SDBD actuators’ efficiency. For this purpose, rear linking tunnels are added to the model as a novel passive flow control. Numerical simulations were performed to determine the best position of the active actuators on the model. The next step is to study the effect of the passive and active flow control on drag reduction and investigating the combination of these methods for improving the active flow control performance at four different freestream velocities (Re ​= ​0.289 ​× ​106–0.722 ​× ​106). The positive effect of this combination is noticeable (a 59% increase in the SDBD actuator’s efficiency for Re ​= ​0.722 ​× ​106), and the non-linear behaviour of this combination leads to high drag reduction of between 13.29% and 17.96% for different Reynolds numbers.

The Effect of Single Dielectric Barrier Discharge Actuators in Reducing Drag on an Ahmed Body

The feasibility of a single dielectric barrier discharge (SDBD) actuator in controlling flow over an Ahmed body, representing a simplified car model, has been numerically and experimentally investigated at Reynolds numbers of 7.68×105 and 2.25×105. The Ahmed body had slant angles of 25∘ and 35∘. The results showed that SDBD actuators could significantly enhance the aerodynamic performance of the Ahmed body. Several arrangements of the actuators on the slant surface and the rear face of the model were examined to identify the most effective arrangement for drag reduction. This arrangement resulted in an approximately 6.1% drag reduction. This improvement in aerodynamic performance is attributed to the alteration of three-dimensional wake structures due to the presence of SDBD, which coincides with surface pressure variations on the slant and rear faces of the Ahmed body.

Effect of dielectric barrier discharge plasma actuators on vortical structures in a mixing layer

The influence of spanwise-uniform electro-fluid-dynamic forcing applied by a dielectric barrier discharge (DBD) plasma actuator on the growth of a plane mixing layer and the dynamics of large-scale spanwise vortices are investigated experimentally. A two-dimensional mixing layer formed between two streams of air with different velocities is employed for this study. Quantitative spatio-temporal measurement of the flow field is acquired using high-speed planar particle image velocimetry. The DBD actuator was constructed such that it imparts perturbations into the splitter-plate boundary layer formed by the high-velocity fluid stream, close to the trailing edge. Through this, the fundamental Kelvin–Helmholtz instability of the current mixing layer and its first sub-harmonic are forced. Forcing the fundamental instability results in the inhibition of vortex pairing due to the attenuation of sub-harmonic instabilities, and thus, mixing layer growth is halted in the vicinity of the trailing edge. With sub-harmonic instability forcing, neighboring vortices interact with each other and amalgamate together through mutual induction. This results in a higher growth rate compared to the unforced mixing layer at the streamwise location of this vortex interaction. Eventually, the growth rate of the forced mixing layers becomes similar to that of the unforced case. These results demonstrate the influence of the applied forcing on the spectral signature, growth, and stability characteristics of the plane mixing layer and the dynamics of the coherent vortical structures.

Self-consistent modeling of a surface AC dielectric barrier discharge actuator: In-depth analysis of positive and negative phases

We report on a detailed numerical study of the two-phase operation of a surface alternating current dielectric barrier discharge actuator. We showcase that when the quasi-periodic regime has been established, residual volume and surface charges play an important role on the discharge evolution strongly coupling the positive and negative phases. It is shown that the quasi-neutral streamer discharge found on the positive phase serves as both a positive and negative charge generator and acts as a virtual anode. As the streamer is not attached to the dielectric surface, most of the surface charging occurs during its after-burn (relaxation) phase. The positive surface charge leads to an distant zone of high electric field and thus ion drift but also interacts majorly with the negative discharge phase. During the latter, microdischarges form near the active electrode and an intense cathode layer feeds with charges the discharge volume. Each microdischarge is followed by a plasma layer formation attached to the dielectric layer expanding further at each repetition until it occupies a volume linked to the streamer elongation length and positively charged surface portion. The strong coupling between the positive and negative phases along with the strong impact of the streamer discharge on both suggest implications that have been ignored so far in terms of electrohydrodynamic force production and its spatiotemporal distribution.

Effect of forcing the tip-gap of a NACA0065 airfoil using plasma actuators: A proof-of-concept study

A proof-of-concept study is presented to understand the effect of continuous forcing by a dielectric-barrier-discharge (DBD) plasma actuator on the strength of the vortices formed in the tip-gap of a single NACA0065 airfoil. The airfoil was mounted with variable tip gaps in the test-section of a suction-type wind tunnel. Continuous forcing was generated by mounting a straight DBD actuator in the tip gap. The flow field was investigated experimentally by dynamic-pressure measurements, and stereoscopic-particle-image-velocimetry (SPIV). In addition, URANS was performed to investigate the flow field in the tip gap region, where SPIV could not be conducted. The results showed that the effectiveness of forcing decreased with increasing tip-gaps and free-stream velocity. The maximum cancellation of the vortex was observed when the blowing ratio was approximately 0.93, with a tip gap of 0.02c (c=chord) and free stream velocity of 2.7 m/s. Both experimental and numerical results showed that in this particular case, the DBD actuator created a strong reverse flow opposing the direction of tip flow. This reverse flow altered the pressure gradient in the tip gap region and canceled the vortex altogether.

Finding a low cost energy multi-DBD plasma actuator for natural heat transfer enhancement in a vertical duct

Current study is focused on numerically finding an optimal active control system to augment the natural heat transfer through a vertical duct. This control system consists of a multiple set of wall embedded Dielectric-Barrier-Discharge (DBD) plasma actuators, which inherently consume the electric power to push the momentum near their embedded electrodes. On the other hand, in current study which the vertical duct is exposed to a constant heat flux on one side, the enhancement of natural convection by wall momentum pushes cause the upward flow to recirculate through the channel and consequently decelerates the mass flow rate to give higher outflow temperatures. The numerical simulation deals with the effects of variable parameters such as Rayleigh number, number of DBD actuators, and the vertical DBD arrangements. A descriptive enhancement ratio: The ratio of the average Nusselt number affected by plasma actuation to the average Nusselt number without DBD control, is used to evaluate capability of the heat transfer augmentation. The numerical results showed that the enhancement ratio in the presence of the DBD actuator reaches to about 2.75. However, the results briefly show the sensitivity of the heat transfer enhancement to the Number of the actuators and their arrangement. As the main goal and the final step, the overall thermal efficiency (OTE) as a parameter expressed to further clarify the performance of plasma actuator system from the perspective of energy consumption is defined as the rate of the augmented heat transfer by the DBD actuator to the actuation electric power consumption. Also, it can be realized that by increasing the number of DBD actuators from 1 to 4, the La increases, and over 4 it is constant. The results show that the case N = 4 can be a candidate for the optimum design.

An Experimental Study on Segmented-Encapsulated Electrode Dielectric-Barrier-Discharge Plasma Actuator for Mapping Ice Formation on a Surface: A Conceptual Analysis

Abstract A novel design of the dielectric barrier discharge (DBD) actuator/sensor is proposed for mapping the location of icing on a surface. The new design uses segmentation of the embedded electrode of the DBD actuator. Segmented DBD actuator/sensor devices were fabricated and experimentally tested in terms of mechanical, thermal and sensing abilities. The sensing capability of the new actuator was analyzed experimentally. Stationary and dynamic icing tests were conducted and the electrical characteristics of the DBD were measured. A parametric study on the effect of the electrode dimensions on the degree of sensitivity of the device was performed. Experimental results show that by using a segmented configuration it is possible to sense the onset of ice formation and also to detect its location. Furthermore, it is possible to detect the initiation of the melting process and measure the time for the water/ice to be completely expelled from the surface. It is also shown that the segmented actuator has better deicing performance in comparison to the conventional actuators. It is also shown that the thermal and active flow control abilities are not compromised by the segmented configuration and thus this device may perform deicing, ice formation and location detection and active flow control.

Simultaneous ice detection and removal based on dielectric barrier discharge actuators

This paper presents a new technique for ice detection using dielectric barrier discharge (DBD) plasma actuator. The DBD ice sensor consists of a pair of electrodes and a test capacitor. Both numerical simulation and experimental studies were conducted. The electrical characteristics of the DBD actuator were measured in the presence of ice. The presence of ice (or water) leads to an increase of the capacitance compared to air and can thus be detected. Dynamic variation of the actuator capacitance and evolution of ice layer melting process was measured. Moreover, multi-DBD actuator was studied for generating icing map on the surface.

Modeling and theoretical analysis of SDBD plasma actuators driven by fast-rise–slow-decay pulsed-DC voltages

Surface dielectric barrier discharge (SDBD) actuators driven by the pulsed-DC voltages are analyzed. The pulsed-DC SDBD studied in this work is equivalent to a classical SDBD driven by a tailored fast-rise–slow-decay (FRSD) voltage waveform. The plasma channel formation and charge production process in the voltage rising stage are studied at different slopes using a classical 2D fluid model, the thrust generated in the voltage decaying stage is studied based on an analytical approach taking 2D model results as the input. A thrust pulse is generated in the trailing edge of the voltage waveform and reaches maximum when the voltage decreases by approximately the value of cathode voltage fall (≈ 600 V). The time duration of the rising and trailing edge, the decay rate and the amplitude of applied voltage are the main factors affecting the performance of the actuator. Analytical expressions are formulated for the value and time moment of peak thrust, the upper limit of thrust is also estimated. Higher voltage rising rate leads to higher charge density in the voltage rising stage thus higher thrust. Shorter voltage trailing edge, in general, results in higher value and earlier appearance of the peak thrust. The detailed profile of the trailing edge also affects the performance. Results in this work allow us to flexibly design the FRSD waveforms for an SDBD actuator according to the requirements of active flow control in different application conditions.

Parametric investigation of the fluid mechanic performance of an AC dielectric barrier discharge plasma actuator

The aim of this work is to systematically quantify and rank the effects of nine different design parameters on the fluid mechanic abilities of a dielectric barrier discharge (DBD) plasma actuator supplied with an alternating current. The ranking and quantification not only consider the parameters themselves but also their interactions with each other. In order to perform this ranking, a Design of Experiment approach is used. This allows the most significant design parameters for the thrust generation, power consumption and thrust to power consumed ratio (force efficiency) of DBD actuator performance to be determined in a systematic way. The results show that the thrust generation is driven by the voltage, distance between the electrodes, AC frequency, and geometry of the exposed electrode, in that order. A high voltage and high frequency, with a thin dielectric, a narrow inter-electrode gap, and a thin and narrow air-electrode results in an increase in the thrust generation.The thrust to power ratio of a DBD is employed as a proxy for the fluid mechanic efficiency. The analysis of the force efficiency shows that the voltage, frequency, distance between the electrodes, and geometry of the air electrode have significant effects. The higher force efficiency is obtained for a high voltage, low frequency, short inter-electrode gap, thin dielectric of low permittivity with a narrow and thin exposed electrode. Finally, two actuators are investigated to determine the best scaling laws for the power consumption as a function of voltage and frequency. In these experiments, the power consumption was a function of voltage to the power of 2.5 and frequency to the power of 1.5. This systematic study of the parameters and their interactions allows general guidelines to be obtained for the best fluid mechanic performance of a DBD, viz. its thrust generation and force efficiency.

Design and experimental evaluation of a plasma swirler with helical shaped actuators

In order to enhance the flow control effectiveness of the plasma swirl injector, dielectric barrier discharge (DBD) actuators with helical electrodes are developed and the performance is compared with that of straight actuators through flow field measurement. This new design can adjust the plasma distribution and increase the plasma intensity. More importantly, the design can be used to adjust the axial velocity besides the azimuthal velocity, therefore it can be used to mitigate flame blow-off or flashback. In addition, the plasma-induced flow can be aligned with the direction of flow moving out of the vane swirler accurately, which can reduce the pressure loss from the swirler. The helical shaped actuator is more suitable for working in conjunction with traditional mechanical swirlers, providing more flexibility in flow control. By changing the direction of the helical electrodes and their relative positions, four different plasma swirler configurations for flow control are considered, making flexible combinations with the vane swirler possible and providing more options for combustion control. Results of flow field measurement showed that a central recirculation zone (CRZ) appeared under the plasma actuation. Compared with that of the straight electrode actuation, the size of CRZ is increased and the back flow in CRZ is enhanced by the helical electrode actuation. Effect of CRZ on the azimuthal velocity dissipation is also observed.

Central recirculation zone induced by the DBD plasma actuation

Central recirculation zone (CRZ) is commonly formed in the near field of the injector exit by the vane swirler and used to stabilize the flame. In our experiment, a CRZ induced by the DBD plasma actuation was observed in the low swirl burner configuration for the first time, which clearly demonstrated that the mechanism of the combustion control by the plasma swirler is mainly through the aerodynamic effect. Three dielectric barrier discharge (DBD) actuators are placed in a circular array around the axis to generate ionic wind in the circumferential direction of the injector. Characteristics of the flow field have been measured using Laser Doppler Anemometry. It is found that a central recirculation zone with the shape of an ellipsoid is formed in the non-reacting flow field with the plasma actuation. The position of the upstream stagnation point was determined by the strength of the actuation. Although the CRZ disappears in the reacting flow field as the result of combustion heat release, the influence of the discharge on the flame lift-off height is noticeable. The results demonstrate that swirl enhancement by the plasma swirler is feasible, flexible and effective as a non-intrusive measure for flow control.

Quasi-stationary modeling of the DBD plasma flow control around airfoil

This paper presents the results of numerical simulation of a dielectric barrier discharge (DBD) plasma actuator and shows its effectiveness to control air flow around the NACA(National Advisory Committee for Aeronautics)0015 airfoil. The actuator consists of two tape electrodes separated by a dielectric layer, and it is mounted on the suction side of the airfoil at 18% of the chord length. An alternating voltage with 20 kV magnitude and 10 kHz frequency is applied between both electrodes. The physical model of the DBD includes the drift of two ionic species, positive and negative, and the Poisson equation for the electric potential distribution. The spatio-temporal distribution of the electric field, the space charge density in the ambient air, and the surface charge density on the dielectric layer have been determined. The time average electric body force was entered into the air flow model, which was solved using the Spalart–Allmaras turbulence technique. The simulation of the air flow was performed for the free-stream velocities between 5 m/s and 20 m/s (Reynolds numbers 1.65 × 105–6.61 × 105 based on the chord length). The results of computations show the effect of the electrohydrodynamic actuation on the flow pattern, the lift and drag coefficients, the pressure coefficient, and the flow fluctuation near the airfoil. The ability of the DBD actuation to effectively control the aerodynamic airfoil characteristics has been confirmed, and its limitations for the discussed case have been determined.

Numerical research on airfoil transition delay by alternative current dielectric barrier discharge actuation

A Dielectric Barrier Discharge (DBD) plasma actuator can create a body force which locally accelerates the base flow leading to an attenuation of broadband disturbance to delay the transition. In this study, numerical simulation on an NLF0416 airfoil is conducted to investigate transition delay and drag reduction by a DBD plasma actuator. To simulate plasma’s effect more accurately, boundary-layer data is acquired from Reynolds Averaged Navier Stocks (RANS) equations instead of laminar boundary layer equations, although RANS equations need a much finer boundary-layer grid, and the linear stability analysis method is used to analyze the boundary layer and get the transition point. In this study, the influences of different actuation intensities and positions are investigated, and results show that if the actuation intensity is stronger and the actuation position is closer to the base transition point, more drag reduction can be obtained. However, the efficiency of plasma transition delay is really low. For example, when the actuation voltage is 16 kV, the actuation frequency is 1 kHz, and the main Mach number is 0.1, the saved power due to drag reduction is about 5.09 W, but the power consumed is about 32.61 W, and the efficiency is just 15.6%.

A Simplified Model for Simulating Flow Stabilization Behind a Cylinder Using Dielectric Barrier Discharge

This article presents a numerical model and simulation results for the flow stabilization problem behind a solid cylinder. Four dielectric barrier discharge actuators are attached to the cylinder surface, each consisting of two tape electrodes. The surface-exposed electrodes are supplied with a high sinusoidal voltage, whereas the embedded ones are electrically grounded. A surface low-temperature plasma is generated near the edge of the exposed electrode, where the electric field intensity is very high. Ions generated by the discharge drift along the cylinder surface and collide with neutral air molecules, generating airflow. This electrohydrodynamic flow suppresses, or completely eliminates, the flow separation in the downwind part of the cylindrical surface. It can also quench, or mitigate, the von Karman vortices behind the cylinder. The simulation results reasonably agree with the experimental data published in the literature, validating the proposed numerical algorithm.