Dielectric Barrier Discharge Plasma Actuator Research Articles

Theoretical breakthrough in the dynamics of a jet in a free-stream flow around a corner

For the first time, the laminar jet in a free-stream flow around a corner with/without a moving wall condition (as it assists the flow) is studied theoretically. The corner may contract the streamlines or expand them depending on the angle of inclination. In the context of incompressibility, it is presented a composite non-similar transformation of the Navier-Stokes (N-S) equations in Cartesian space to approximately decipher the nature of the boundary layer flow over the entire physical domain; i.e. 0 ≤ x, y < ∞. The transformed Partial Differential Equations (PDEs) are then solved by an in-house MATLAB code, which employs an implicit algorithm of a tridiagonal form with quasi-linearization technique. For a stationary wall, as the negative angle of the corner meets Falkner-Skan (F-S) limitation and expands beyond, the predictive model starts to show a critical location, which reveals directly the flow separation point. This critical location moves toward the jet origin as the angle of inclination becomes more negative. Here, these locations are extracted as a function of the inclination parameter in order to manifest the suitability of a jet to delay boundary layer separation. A similar scenario also applies to the moving wall case. In this case, it was recorded that a moving wall condition delays separation for a considerable distance. It should be pointed out that up to date, there is no theoretical investigation on this specific flow geometry despite the many associated applications; and the limited available reports on an analogous flow geometry are those from the Computational Fluid Dynamics (CFD) and on a case by case basis. More specifically, the present geometry is quite similar to the flow passing the way down to the trailing edge of an airfoil, with a jet generator mechanism such as Dielectric Barrier Discharge (DBD) plasma actuator to delay flow separation on the backside of the airfoil.Here, by the use of the theoretical non-similarity concept empowered by some recent advancements (see Jafarimoghaddam, 2020 and Jafarimoghaddam, 2021), the fundamental problem of a jet discharged in the lower boundary of a freestream flow over a wedge is successfully solved.This theoretical breakthrough suggests promising avenues for the future design of airfoils with moving parts/flaps as an innovative step forward to enhance maneuverability of the flying objects.

Supersonic compressor cascade flow control using plasma actuation at low Reynolds number

To control the supersonic compressor cascade flow at low Reynolds numbers, this paper describes the use of nanosecond dielectric barrier discharge (NS-DBD) plasma actuation for flow control, and presents the results of large-eddy simulations conducted to investigate the corresponding flow control effects. NS-DBD plasma actuation on both the blade pressure surface and suction surface induces a distorted flow structure (DFS) within the blade passage. In the case of NS-DBD plasma actuation on the blade pressure surface, the influence of the DFS on the flow is suppressed by a shock wave. Even so, the DFS can still trigger the instability in the shear layer between the separated flow and the mainstream flow. Shock-wave-induced large-scale flow separation on the blade pressure surface is then suppressed, and the overall total pressure loss of the blade passage is reduced by 7.4%, despite the increased shock wave loss from the reduced flow blockage within the blade passage. In the case of NS-DBD plasma actuation on the blade suction surface, the DFS is less effective in suppressing the shock-wave-induced small-scale flow separation on the blade suction surface. However, the DFS on the blade suction surface enhances the shock wave oscillations within the blade passage, and this suppresses the flow separation on the blade pressure surface.

Visualization of the Electrohydrodynamic and Thermal Effects of AC-DBD Plasma Actuators of Plate- and Wire-Exposed Electrodes

The dielectric barrier discharge plasma actuator is a promising flow control device that uses surface discharge. The actuator generates an electrohydrodynamic force and Joule heating that contribute to the flow control. Thus, it is important to investigate the electrohydrodynamic and thermal effects on the air flow. To this end, the flow velocity field, density field, and surface temperature distribution induced by an alternating current dielectric barrier discharge plasma actuator were experimentally examined, adopting particle image velocimetry, the background oriented schlieren technique, and an infrared camera. These experiments were conducted for plate- and wire-exposed electrode plasma actuators to investigate the effect of the shape of the exposed electrode. It was confirmed that the topology of the discharge is different between the two types of plasma actuators. This results in a difference in the spatial distributions of the velocity and density fields between the two actuators. In particular, we clarified that there is an obvious difference in the peak position of the density and temperature distribution between the two actuators. We also confirmed that the difference in the spatial distribution of the vertical velocity makes the above difference.

Parametric optimization of surface dielectric barrier discharge actuators for ice sensing application

In this paper a parametric optimization of the dielectric barrier discharge (DBD) plasma actuator is conducted in order to achieve better ice sensing and deicing performance. For this purpose, different DBD plasma actuators were tested by changing the main geometrical dimension of the DBD plasma actuator and dielectric material. Both the ice sensing and thermal characteristics of the DBD plasma actuator were analyzed and compared. The results reveal that there exists two separate set of optimum parameters that lead to best ice sensing and thermal behavior. For both the sensing and thermal characteristics, the thinnest DBD showed the best performance. Kapton DBD plasma actuator showed the highest surface temperature while PMMA (poly methyl methacrylate) had the best performance for ice sensing. In the end, the deicing performance of a DBD actuator that had in average better thermal and ice sensing performance was tested for deicing an ice layer and a frost layer. The progress of the deicing process and the ice sensing measure on the surface were recorded and analyzed.

Flow characteristics of a rectangular jet with DBD plasma actuators at nozzle exit

The objective of this study is to establish an active flow control method for a 2:1 rectangular jet using a dielectric barrier discharge plasma actuator (DBD-PA) installed at the exit of a nozzle. These additional devices are able to change the velocity distribution of a jet stream by adding an induced flow to the airflow ejected from a rectangular nozzle. These DBD-PA were placed on the short and long sides, and on the four corners of the nozzle exit. The rectangular nozzle had a height of 30 mm and a width of 60 mm. The Reynolds number of the jet was 9,000. The flow field was measured by particle image velocimetry (PIV). The flow field was visualized by tracer injection method. The DBD-PA has an influence on the formation of the large-scale vortical structure in the share layers of the rectangular jet. For the jet with DBD-PA on the long sides of the nozzle, the length of potential core increases more than that with DBD-PA on the short sides and the four corners of the nozzle. The spread of a rectangular jet in the x-z cross-section is significantly affected by the DBD-PA installed at the short sides and the four corners of the nozzle.

Визуализация потока в каверне с активным управлением с помощью актуатора диэлектрического барьерного разряда

The results of hydrodynamic pressure fluctuations control by means of dielectric barrier discharge plasma actuator in a rectangular cavity with sharp edges are presented. The study was carried out at the free flow velocity V∞=37 m/s. The discharge was organized near the leading edge of the cavity. The average energy of the discharge pulse was 0.03 J, its duration was 1 ms, and frequency modulation was implemented at the natural resonant frequencies of 500, 817, 1317 Hz of the cavity and a high frequency of 2160 Hz, which did not correspond to the natural resonant pressure peak. Pressure pulsations were measured with a Kulite pressure transducer. It is established that the discharge regime affects the pressure fluctuations in the cavity. The pressure amplitude at the downstream wall of the cavity can be increased from 117 dB to 128 dB or decreased to 110 dB, respectively, if the dominant or higher modes are pumped by the discharge. The PIV visualization was organized in phase-locked mode. The pressure spectrum corresponds to the magnitude of coherent structures in the shear layer of the cavity.

Flow visualization in cavity with dielectric barrier discharge actuator control

The results of hydrodynamic pressure fluctuations control by means of a dielectric barrier discharge plasma actuator in a rectangular cavity with sharp edges are presented. The study was carried out at the free flow velocity V=37 m/s. The discharge was organized near the leading edge of the cavity. The average energy of the discharge pulse was 0.03 J, its duration was 1 ms, and frequency modulation was implemented at the natural cavity resonant frequencies of 500, 817, 1317 Hz and at a high frequency of 2160 Hz which did not correspond to the natural resonant pressure peak. Pressure pulsations were measured with a Kulite pressure transducer. It is established that the discharge regime affects the pressure fluctuations in the cavity. The pressure amplitude at the downstream wall of the cavity can be either increased from 117 dB to 128 dB or decreased to 110 dB if, respectively, if either the dominant or higher modes are pumped by the discharge. The PIV visualization was organized in the phase-locked mode. The pressure spectrum corresponds to the magnitude of coherent structures in the shear layer of the cavity. Keywords: plasma actuator, cavity, active control, DBD, boundary layer, mixing layer, closed loop.

Experimental Study for Separated Flow Control around Rotor Blades Using Highly Integrated Dielectric Barrier Discharge Plasma Actuator

Highly integrated dielectric barrier discharge (DBD) plasma actuators can be driven with a voltage one order of magnitude lower than that of conventional plasma actuators by properly arranging multiple electrodes, and can generate induced flow velocities of equal or greater magnitude. In addition, it is possible to control the large scale separation that occurs around the wings of aircraft and other devices, and thus to improve aerodynamic characteristics. In this study, a highly integrated DBD plasma actuator with multiple 20 electrodes was fabricated and applied to the wing surface to control the airflow from the leading edge to the trailing edge, and the aerodynamic characteristics of the NACA4412 airfoil were experimentally investigated. When the highly integrated DBD plasma actuator was driven, the lift coefficient was found to be improved compared to that with a conventional plasma actuator.

Characteristics of a nanosecond pulsed dielectric barrier plasma actuator with a surface water film

Aircraft icing is one of the most serious hazards for airflight operations. The nanosecond pulsed surface dielectric barrier discharge (NSDBD) plasma actuator is recognized as an extremely promising anti-icing technology. In this paper, a multi-physics coupling simulation is used to study the plasma-discharge characteristics and responses of the air–water flow field generated by an NSDBD plasma actuator with a surface water film. The computational model describes air flows through an NSDBD plasma actuator with a water film at the center of two upper powered electrodes. The multi-physics model is solved using the drift-diffusion and energy-conservation equations for the plasma discharge and the mass, momentum, energy, and concentration equations for the air–water flow. The results show that, at the beginning of the voltage pulse, the surface water film has no effect on the plasma discharge. Then, during the pulse plateau time, the film leads to a longer plasma-discharge time and a larger plasma-discharge region. Furthermore, the film causes the plasma-actuator surface to develop a virtual positive electrode that would otherwise be absent and results in the plasma actuator generating more intense shock waves, higher gas temperatures, and larger heated regions.

Improved performance of polyimide Cirlex‐based dielectric barrier discharge plasma actuators for flow control

AbstractDielectric barrier discharge (DBD) plasma actuators are simple electrohydrodynamic devices, which are able to provide effective aerodynamic control. One of the main components of these devices is the thin dielectric layer, which allows to separate and prevent the arc between the high‐voltage electrodes. Different materials can be used as dielectric layer to reduce the power consumption or boost the flow controlling effect of the actuators. In this context, this report presents a comparative study of two commercial polyimides, Kapton and Cirlex, used as dielectric layer of surface DBD plasma actuators. The electrical, dielectric, mechanical, electromechanical, and thermal properties were obtained to evaluate overall performance. It was verified that Cirlex (8.3 W) consumes less power than Kapton (21.3 W) to generate higher induced flow velocity of ≈3.4 m/s for an input voltage of 11 kVpp and 24 kHz. During one AC cycle at 11 kVpp the charge transferred for Cirlex (70 nC) is lower than for Kapton (100 nC), as well as the dielectric breakdown voltage to ignite the plasma discharge, 1.5 and 2.2 kVpp, respectively. The Cirlex DBD presents a higher voltage operation limit (at least 14 kVpp) and a more regular plasma discharge, which results in a more homogenous thermal profile and temperature distribution during its operation. The Cirlex actuator delivered higher mechanical power (6.2 mW) and achieved higher electromechanical efficiency (0.004%). The polyimide Cirlex proved to be a suitable alternative for Kapton to fabricate DBD plasma actuators for flow control with improved performance.

Dynamic Burst Actuation to Enhance the Flow Control Authority of Plasma Actuators

A computational study was conducted on flows over an NACA0015 airfoil with dielectric barrier discharge (DBD) plasma. The separated flows were controlled by a DBD plasma actuator installed at the 5% chord position from the leading edge, where operated AC voltage was modulated with the duty cycle not given a priori but dynamically changed based on the flow fluctuations over the airfoil surface. A single-point pressure sensor was installed at the 40% chord position of the airfoil surface and the DBD plasma actuator was activated and deactivated based on the strength of the measured pressure fluctuations. The Reynolds number was set to 63,000 and flows at angles of attack of 12 and 16 degrees were considered. The three-dimensional compressible Navier–Stokes equations including the DBD plasma actuator body force were solved using an implicit large-eddy simulation. Good flow control was observed, and the burst frequency proven to be effective in previous fixed burst frequency studies is automatically realized by this approach. The burst frequency is related to the characteristic pressure fluctuation; our approach was improved based on the findings. This improved approach realizes the effective burst frequency with a lower control cost and is robust to changing the angle of attack.

Highly responsive multi-flow pattern generation by multi-electrode plasma actuator using a single power supply

A dielectric-barrier-discharge plasma actuator (DBD-PA) is an active flow-control device that uses ionic wind generated by electrohydrodynamic forces. A DBD-PA controls fluid motion and offers quick response without the need for moving parts. Previous studies have proposed methods for generating various flow patterns with a DBD-PA for fluid control. This paper presents a method for generating multiple flow patterns using a multi-electrode DBD-PA that is driven by a single-channel high-voltage power supply with a relay circuit. In contrast, conventional methods of realizing multiple flow patterns involve the use of a multi-channel power supply. Hence, they have the disadvantage of requiring a complicated power supply system. The proposed method succeeded in realizing several induced-flow modes involving the generation of a directionally controllable wall jet, various sizes of vortices, and an upward jet by altering the switching frequency and switching ratio. In addition, our experimental results indicate that the proposed method can control the flow pattern with a significantly short response time. The direction of the wall jet can be switched within tens to hundreds of milliseconds. Therefore, the proposed method combines simplicity and versatility and is expected to facilitate the realization of multifunctional active flow control in various flow fields, such as flow turbulent boundary layer control, thermal diffusion control, gas mixing, and flame-stability enhancement.

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.

Drag reduction of circular cylinder using linear and sawtooth plasma actuators

The flow around a single circular cylinder modified by the Dielectric Barrier Discharge (DBD) plasma actuator is investigated experimentally at a Reynolds number Re = 5.25 × 103. The main purpose of the present study is to establish a comprehensive understanding of the effects of linear and sawtooth DBD plasma actuators (under steady and unsteady actuation modes, with different applied voltage Va, normalized modulation frequency F+, and duty cycle DC) on the time-averaged drag coefficient CD and flow characteristics of the cylinder. Extensive measurements are performed in the near wake of the cylinder using a load cell, hotwire anemometer, flow visualization, and particle image velocimetry techniques. The maximum drag reductions are 58% and 22.8% under the steady and unsteady actuation modes of the linear actuators, respectively, when a voltage of Va = 11 kV is applied. On the other hand, the maximum drag reductions achieved by the steady and unsteady actuation modes of the sawtooth actuators are 51.8% and 53.0%, respectively. The corresponding power efficiencies are 1.6%, 0.9%, 1.4%, and 2.1%, respectively. A detailed examination of the near wake dynamics unveils that the mechanisms behind the substantial drag reductions are quite different for the two different actuators, which account for the difference in drag reduction and efficiency.

Ice shape modulation with nanosecond pulsed surface dielectric barrier discharge plasma actuator towards flight safety

Ice accretion on aircraft wings seriously damage the aerodynamic performance and flight safety of an aircraft. To deal with this issue, a leading-edge ice shape modulation method using nanosecond pulsed surface dielectric barrier discharge (nSDBD) is proposed, featuring the merit of less energy consumption when compared to full-wing de-icing. A set of wind tunnel experiments are conducted for verification purposes. Results show that the dangerous continuous ice can be modulated into periodically segmented ice pieces by nSDBD, forming a wavy leading edge, and the energy consumption of ice shape modulation is less than 50% of that of complete deicing. In the case of NACA0012 airfoil, ice shape modulation can improve the lift noticeably at each angle of attack (0° to 22°), delay the stall angle by 2°, and reduce the drag coefficient by more than 50% compared to full ice condition. The duration of ice shape modulation with plasma actuators lasts for about 4 min to 6 min. For flow separation control, the coherent streamwise vortices generated by the wavy leading edge are able to enhance the mixing between the boundary layer and the freestream, resulting in an increase of the ability to resist the adverse pressure gradient above the airfoil. Since both ice shape modulation and flow separation control benefit the aerodynamic performance of icing airfoils, the flight safety is improved.

Plasma-Based Dynamic Stall Control and Modeling on an Aspect-Ratio-One Wing

Quasi-static and dynamic stall control experiments, using dielectric barrier discharge plasma actuators, were performed on a square-tipped aspect-ratio-one wing, with a NACA 0015 profile, under harmonic pitching, at a Reynolds number of . Relatively low and relatively high pulse-modulated reduced excitation frequencies were introduced at the leading edge; the former produced the largest poststall lift improvements, whereas the latter produced the highest maximum lift. A reduced frequency, based on laminar separation bubble shedding, was enlisted to explain the differences between the two results. Under conditions of dynamic pitching, evidence of a dynamic stall vortex was absent, due to its interaction with the strong tip vortices, consistent with prior experimental and numerical investigations. As a general rule, performance benefits produced by excitation under quasi-static conditions were reproduced under harmonic pitching. Low-order dynamic stall and dynamic stall control models, based on a modified version of the Goman–Khrabrov delta-wing concept, were evaluated. Model constants were obtained from quasi-static data sets, and a single baseline dynamic case was employed to determine the time constants. The model produced excellent results for both baseline and controlled cases, which was attributed to similar lift and stall mechanisms exhibited by delta and rectangular low-aspect-ratio planforms.

Characteristics of a dielectric barrier discharge plasma actuator driven by pulsed-DC high voltage

Dielectric barrier discharge using pulsed-DC high voltage (pulsed-DC DBD) have been proven to be capable of effectively reducing skin friction drag in turbulent boundary layers with limited power consumption, thus producing significant net power savings. In this work, the characteristics of pulsed-DC DBD, including power consumption, induced flow structure, thermal effect, and body force, are investigated sequentially. Both the power consumption and pressure waves produced by pulsed-DC DBD are similar to that of DBD using nanosecond pulses (ns-DBD), whereas the wall-bounded jet structure resembles that of DBD using sinusoidal high voltage (ac-DBD). A curved wall jet is induced at a small pulse width, which turns into a straight one due to the combined effect of momentum and thermal addition when the pulse width increases. With increasing pulse width, the induced body force goes up while the thermal effect weakens. Although pulse frequency has no impact on the wall-bounded jet topology, the body force increases with pulse frequency because of the enhanced energy entrainment. With these results, four parameters that affect the performance of pulsed-DC DBD are extracted, including the pulse leading edge, pulse width, frequency, and amplitude, which lays the foundation for the optimization of pulsed-DC DBD.

Experimental study on the plasma actuators for the tip leakage flow control in a turbine cascade

In this paper, the effects of dielectric barrier discharge (DBD) plasma actuators (PAs) on the leakage flow structures and loss in a turbine cascade have been experimental studied. Two group cases have been conducted to evaluate the performance of the DBD plasma actuators and its effect varied with the attack angle (α). By measuring the static pressure on the casing and the flow field at the exit section, the effects of the DBD PAs have been illustrated. Results show that the DBD plasma actuators on the tip of turbine cascade could make effect on the tip leakage flow by weaken the strength of the TLV near the casing. Rising the actuation strength, this effect would be enhanced. Besides, this effect on the flow structure mainly focuses on the TLV near the casing, changes in the blade passage could be ignored with the action of the DBD PAs. In the study on the attack angle, the largest loss reduction of 7.8% is noticed with the inflow Re=0.64×105 and α=5°.

Flow separation control in S-shaped ∼inlet with a nanosecond pulsed surface dielectric barrier discharge plasma actuator

A nanosecond pulsed surface dielectric barrier discharge (nSDBD) plasma actuator is proposed to eliminate the complex 3D flow separation in an S-shaped ∼engine inlet. A set of wind tunnel experiments based on pressure measurements are conducted to verify the flow control effectiveness and obtain the influence laws of actuation voltage, pulse frequency, actuator layout and coverage area. The results show that nSDBD can effectively eliminate flow separation, leading to a noticeable improvement in the total pressure distribution at the outlet, manifested as a reduction in the low-pressure zone and an extension of the high-pressure zone. The spanwise layout nSDBD delivers a better flow control effect compared to the streamwise layout. For the same geometrical layout, the flow control effect improves with increasing voltage, and the optimal actuation frequency corresponds to a Strouhal number of approximately F + = 0.5. In particular, with a spanwise array of nSDBD plasma actuators operating at V p-p = 10 kV and F + = 0.5, the flow separation region is completely suppressed. The mechanism of flow separation with nSDBD can be ascribed to the mixing enhancement between the boundary layer and the main flow, which improves the boundary layer’s ability to resist the adverse pressure gradient.

Experimental investigation of induced velocity by dielectric barrier discharge plasma actuator in different configurations

This paper aims to study the effect of different geometrical and electrical parameters, including the voltage, frequency, dielectric thickness, gap width between electrodes, length of electrodes, number of electrodes, and shapes of electrodes, on the induced velocity by the Dielectric Barrier Discharge (DBD) plasma actuators in quiescent air. In addition, the effect of the course of induced velocity evolution in the downstream of actuators has been investigated for different geometries. The streamwise velocity was obtained through the total and static pressure measurement using silicon tubes. The model is a flat plate equipped with a DBD plasma actuator. These experiments were performed for the peak-to-peak voltage range between 8 and 15 kV, and two values of frequency are equivalent to 5 and 10 kHz. The results showed that the multilinear DBD plasma actuator has a maximal induced velocity in the same voltage and frequency as of a single DBD plasma actuator. Evaluation of the induced velocity along the streamwise direction for multilinear, serpentine, and horseshoe actuators showed that these actuators had more than one induced velocity peak.