Plasma Flow Control Research Articles

Influence of Mach number and static pressure on plasma flow control of supersonic and rarefied flows around a sharp flat plate

This paper presents an experimental investigation, carried out at the Icare Laboratory by the FAST team, focusing on plasma flow control in supersonic and rarefied regime. The study analyzes how the Mach number as well as the ambient pressure modify the repercussions of the plasma actuator on the shock wave. It follows previous experiments performed in the MARHy (ex–SR3) wind tunnel with a Mach 2 flow interacting with a sharp flat plate, where modifications induced by a plasma actuator were observed. The flat plate was equipped with a plasma actuator composed of two aluminum electrodes. The upstream one was biased with a negative DC potential and thus, created a glow discharge type plasma. Experimental measurements showed that the boundary layer thickness and the shock wave angle increased when the discharge was ignited. The current work was performed with two nozzles generating Mach 4 flows but at two different static pressures: 8 and 71 Pa. These nozzles were chosen to study independently the impact of the Mach number and the impact of the pressure on the flow behavior. In the range of the discharge current considered in this experimental work, it was observed that the shock wave angle increased with the discharge current of $$+15\%$$ for the Mach 2 flow but the increase rate doubled to $$+28\%$$ for the Mach 4 flow at the same static pressure, showing that the discharge effect is even more significant when boosting the flow speed. When studying the effect of the discharge on the Mach 4 flow at higher static pressure, it was observed that the topology of the plasma changed drastically and the increase in the shock wave angle with the discharge current of $$+21 \%$$ .

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.

Simple frigate shape plasma flow control

This experimental investigation presents a new active flow control technique based on plasma actuators applied to a backward facing step whose structure is similar to that formed by the hangar and flight deck of small naval vessels. These experiments were carried out by testing a simple frigate shape model settled at 0° wind over deck in a low-speed wind tunnel. Two different configurations of dielectric barrier discharge plasma actuator have been used to modify the flow downstream of the step. Results obtained investigating the flow by particle image velocimetry prove the capacity of plasma actuators by reducing instabilities and turbulence over the simple frigate shape model.

Helical mirrors for active plasma flow suppression in linear magnetic traps

A novel concept of helical mirror confinement with active axial and radial plasma flow control is discussed. The idea relies on the retarding force that appears when biased plasma experiences rotation in crossed electrical and helical mirror magnetic fields. Preparations for its experimental study started in Budker Institute of Nuclear Physics, Novosibirsk. Possible parameter space for a concept-exploration-class device SMOLA is identified. Details of numerical optimization of the magnetic structure of the device are presented. The main physical task for the SMOLA experiment will be direct demonstration of the helical mirror performance in simple experimental conditions at reasonably low plasma parameters.

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.

Wind tunnel experiments on flow separation control of an Unmanned Air Vehicle by nanosecond discharge plasma aerodynamic actuation**Project supported by the National Natural Science Foundation of China (Grant Nos. 61503302, 51207169, and 51276197), the China Postdoctoral Science Foundation (Grant No. 2014M562446), and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2015JM1001).

Plasma flow control (PFC) is a new kind of active flow control technology, which can improve the aerodynamic performances of aircrafts remarkably. The flow separation control of an unmanned air vehicle (UAV) by nanosecond discharge plasma aerodynamic actuation (NDPAA) is investigated experimentally in this paper. Experimental results show that the applied voltages for both the nanosecond discharge and the millisecond discharge are nearly the same, but the current for nanosecond discharge (30 A) is much bigger than that for millisecond discharge (0.1 A). The flow field induced by the NDPAA is similar to a shock wave upward, and has a maximal velocity of less than 0.5 m/s. Fast heating effect for nanosecond discharge induces shock waves in the quiescent air. The lasting time of the shock waves is about 80 μs and its spread velocity is nearly 380 m/s. By using the NDPAA, the flow separation on the suction side of the UAV can be totally suppressed and the critical stall angle of attack increases from 20° to 27° with a maximal lift coefficient increment of 11.24%. The flow separation can be suppressed when the discharge voltage is larger than the threshold value, and the optimum operation frequency for the NDPAA is the one which makes the Strouhal number equal one. The NDPAA is more effective than the millisecond discharge plasma aerodynamic actuation (MDPAA) in boundary layer flow control. The main mechanism for nanosecond discharge is shock effect. Shock effect is more effective in flow control than momentum effect in high speed flow control.

Lift Augmentation Based on Flap Deflection With Dielectric Barrier Discharge Plasma Flow Control Over Multi-Element Airfoils

The effect of the lift augmentation of multi-element airfoils with increased flap deflection and dielectric barrier discharge (DBD) plasma flow control on the flap at several angles of attack (AOAs) is investigated numerically and experimentally. A phenomenological body force model is employed to simulate the DBD actuators at Re = 1.03 × 106. The simulation results show that the atmospheric plasma generated by the DBD actuators completely suppresses the flow separation over the flap at several AOAs, and consequently, the lift augmentation of a multi-element airfoil can be achieved over the entire prestall AOA range. A corresponding flow control experiment on a multi-element airfoil performed in a low-speed wind tunnel at a freestream velocity of 30 m/s is presented; in this experiment, particle image velocimetry (PIV) was employed for flow visualization over the upper surface of the flap. The PIV results demonstrate that the flow separation on the flap is suppressed completely by the same DBD actuators used in the simulation.

Two-stage energy thermalization mechanism in nanosecond pulse discharges in air and hydrogen–air mixtures

Time-resolved and spatially resolved temperature measurements, by pure rotational picosecond broadband coherent anti-Stokes Raman spectroscopy (CARS), and kinetic modeling calculations are used to study kinetics of energy thermalization in nanosecond pulse discharges in air and hydrogen–air mixtures. The diffuse filament, nanosecond pulse discharge (pulse duration ∼100 ns) is sustained between two spherical electrodes and is operated at a low pulse repetition rate to enable temperature measurements over a wide range of time scales after the discharge pulse. The experimental results demonstrate high accuracy of pure rotational ps CARS for thermometry measurements in highly transient non-equilibrium plasmas. Rotational–translational temperatures are measured for time delays after the pulse ranging from tens of ns to tens of ms, spanning several orders of magnitude of time scales for energy thermalization in non-equilibrium plasmas. In addition, radial temperature distributions across the plasma filament are measured for several time delays after the discharge pulse. Kinetic modeling calculations using a state-specific master equation kinetic model of reacting hydrogen–air plasmas show good agreement with experimental data. The results demonstrate that energy thermalization and temperature rise in these plasmas occur in two clearly defined stages, (i) ‘rapid’ heating, caused by collisional quenching of excited electronic states of N2 molecules by O2, and (ii) ‘slow’ heating, caused primarily by N2 vibrational relaxation by O atoms (in air) and by chemical energy release during partial oxidation of hydrogen (in H2–air). The results have major implications for plasma assisted combustion and plasma flow control.

Numerical investigation of tandem-cylinder noise reduction using plasma-based flow control

AbstractThe noise of flow over tandem cylinders at $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{\mathit{Re}}_D= 22\, 000$ and its reduction using single dielectric barrier discharge (SDBD) plasma actuators are simulated numerically both to confirm and extend experimental results. The numerical approach is based on large-eddy simulation (LES) for the turbulent flow field, a semi-empirical plasma actuation model, and Lighthill’s theory for acoustic calculation. Excellent agreement between LES and experimental results is obtained for both the baseline flow and flow with plasma control in terms of wake velocity profiles, turbulence intensity, and frequency spectra of pressure fluctuations on the downstream cylinder. The validated flow-field results allow an accurate acoustic analysis based on Lighthill’s equation, which is solved using a boundary-element method. The effectiveness of plasma actuators for reducing noise is clearly demonstrated. In the baseline flow, the acoustic field is dominated by the interaction between the downstream cylinder and the upstream wake. Through suppression of vortex shedding from the upstream cylinder, the interaction noise is reduced drastically by the plasma flow control, and the vortex-shedding noise from the downstream cylinder becomes equally important. At a free-stream Mach number of 0.2, the peak sound pressure level is reduced by approximately 16 dB. This suggests the viability of plasma actuation for active aeroacoustic control of airframe noise.

Flow Control Over a Circular Cylinder Using Pulsed Dielectric Barrier Discharge Actuators

Abstract Immersed bodies such as struts, vanes, and instrumentation probes in gas turbine flow systems will, except at the lowest of flow velocities, shed separated wakes. These wakes can have both upstream and downstream effects on the surrounding flow. In most applications, surrounding components are designed to be in the presence of a quasi-steady or at least nonvariant flow field. The presence of unsteady wakes has both aerodynamic and structural consequences. Active flow control of wake generation can therefore be very valuable. One means to implement active flow control is by the use of plasma actuation. Plasma actuation is the use of strong electric fields to generate ionized gas that can be actuated and controlled using the electric fields. The controlling device can be based on AC, DC, or pulsed-DC actuation. The present research was conducted using pulsed-DC from a capacitive discharge power supply. The study demonstrates the applicability of, specifically, pulsed-DC plasma flow control of the flow on a circular cylinder at high Reynolds numbers. The circular cylinder was selected because its flow characteristics are related to gas turbine flowpath phenomena, and are well characterized. Further, the associated pressure gradients are some of the most severe encountered in fluid applications. The development of effective plasma actuators at high Reynolds numbers under the influence of severe pressure gradients is a necessary step toward developing useful actuators for gas turbine applications beyond laboratory use. The reported experiments were run at Reynolds numbers varying from 50,000 to 97,000, and utilizing various pulse frequencies. Further the observed performance differences with varying electric field strengths are discussed for these Reynolds numbers. The results show that flow behaviors at high Reynolds numbers can be influenced by these types of actuators. The actuators were able to demonstrate a reduction in both wake width and momentum deficit.

Design and Application of Multichannel Peristaltic Acceleration Pulsed Plasma Power Supply

Based on the continuous and microsecond pulsed plasma power supply, a multichannel peristaltic acceleration pulsed plasma power supply is developed. The overall design ideas and system block diagram are proposed. Additional modulation functions of pulsed phase angle, duty cycle ratio, and pulsed frequency are implemented to improve the control capability of the plasma actuation for flow control. Long time running results show that this power supply can generate good waveform and smooth plasma discharge. It meets the requirements of plasma discharge for various means of flow control, such as continuous, pulsed, duty cycle, and peristaltic acceleration plasma actuation. Finally, successful wind-tunnel experiments for plasma flow control over a slender body at high angle of attack by using this power supply is conducted. It shows that the plasma actuation excited by the power supply provides the highly needed lateral force and moment control on slender body at high angles of attack, without the unpredictable onset of asymmetric aerodynamic loads.

Effects of Plasma Aerodynamic Actuation on Corner Separation in a Highly Loaded Compressor Cascade

This paper reports experimental results on the effects of plasma aerodynamic actuation (PAA) on corner separation control in a highly loaded, low speed, linear compressor cascade. Total pressure loss coefficient distribution was adopted to evaluate the corner separation control effect in wind tunnel experiments. Results of pressure measurements and particle image velocimetry (PIV) show that the control effect of pitch-wise PAA on the endwall is much better than that of stream-wise PAA on the suction surface. When both the pitch-wise PAA on the endwall and stream-wise PAA on the suction surface are turned on simultaneously, the control effect is the best among all three PAA types. The mechanisms of nanosecond discharge and microsecond discharge PAA are different in corner separation control. The control effect of microsecond discharge PAA turns out better with the increase of discharge voltage and duty cycle. Compared with microsecond discharge PAA, nanosecond discharge PAA is more effective in preventing corner separation when the freestream velocity increases. Frequency is one of the most important parameters in plasma flow control. The optimum excitation frequency of microsecond discharge PAA is 500 Hz, which is different from the frequency corresponding to the case with a Strouhal number of unity.

Physical principle dealing with development of vortices formed by DBD actuator

Several configurations of vortex trains generated by plasma dielectric barrier discharge were measured by method of time-resolved PIV with application of phase-averaging of data. Mainly dynamics of vortical structures was studied in terms of vortex core trajectory, convective velocity, vortex diameter and vortex circulation. The generally valid physical mechanism of such vortices based on gained information will be introduced and presented. This mechanism will be considered with regards to the use for active flow control thus it could be very helpful in the future works dealing with plasma flow control.

Numerical Study on Propeller Flow-Separation Control by DBD-Plasma Aerodynamic Actuation

The process of dielectric barrier discharge (DBD) plasma flow-separation control on screw propeller is numerically simulated based on the unsteady compressible Navier-Stokes equations loosely with DBD-plasma body force aerodynamic actuation mechanism. The effect and the mechanism of plasma flow control to enhance the propeller aerodynamic characteristics are discussed. The results show that the propeller aerodynamic characteristics will decrease as the altitude increase without plasma flow control, but it will first increase and then decrease as the altitude increases with plasma flow control. The effect of DBD-plasma flow control on the distribution of pressure is small at ground condition, and the difference of pressure distribution between general propeller and plasma efficiency-enhance propeller will be increased as the altitude increases. The effect of DBD-plasma flow-separation control will increase as the altitude increases. Mainly, the mechanism of the plasma flow control to enhance the propeller aerodynamic is obtained as follows. The flow separation on the propeller blade surface could be effectually controlled by DBD-plasma aerodynamic actuation, thereby increasing the efficiency of the propeller. The pressure of the windward surface of the blade will decrease by the plasma body force, which will increase the thrust of the propeller.

A temporal proper decomposition (TPOD) for closed-loop flow control

Motivated by closed-loop flow control appli- cations, a formulation of the proper orthogonal decomposition (POD) is demonstrated, which is capable of characterizing not only the controlled and natural states of a given flow, but also the transient behavior between these states. This approach, which is termed temporal POD (TPOD), extracts the optimum frame of reference and the temporal infor- mation regarding the dynamics of the flow in the natural, controlled and transient states. In this paper, the TPOD concept is developed and is subsequently demonstrated in two experiments using dielectric barrier discharge plasma flow control: (1) flow over a circular cylinder at subcritical Reynolds number and (2) flow over a NACA 0015 airfoil at a large post-stall angle of attack. Both flows exhibit well- defined and distinct natural and controlled flow states. For the cylinder flow, the TPOD technique is used to develop a low-order dynamical systems model that is shown to properly capture the dynamics of the first TPOD mode, including the natural, forced and transient regimes. In the airfoil experiment, the TPOD approach is shown to provide the unique ability to conditionally examine the families of flow trajectories between natural and controlled states for user-selected initial conditions. This can be extremely useful in order to understand the physical mechanisms of flow control in complex flows where there may be very little a priori knowledge regarding the system behavior.

Measurements and kinetic modeling of energy coupling in volume and surface nanosecond pulse discharges

Nanosecond pulse discharge plasma imaging, coupled pulse energy measurements, and kinetic modeling are used to analyze the mechanism of energy coupling in high repetition rate, spatially uniform, nanosecond pulse discharges in air in plane-to-plane geometry. Under these conditions, coupled pulse energy scales nearly linearly with pressure (number density), with energy coupled per molecule being nearly constant, in good agreement with the kinetic model predictions. In spite of high-peak reduced electric field reached before breakdown, E/N ∼ 500–700 Td, the reduced electric field in the plasma after breakdown is much lower, E/N ∼ 50–100 Td, predicting that a significant fraction of energy coupled to the air plasma, up to 30–40%, is loaded into nitrogen vibrational mode.A self-similar, local ionization kinetic model predicting energy coupling to the plasma in a surface ionization wave discharge produced by a nanosecond voltage pulse has been developed. The model predicts key discharge parameters such as ionization wave speed and propagation distance, electric field, electron density, plasma layer thickness, and pulse energy coupled to the plasma, demonstrating good qualitative agreement with experimental data and two-dimensional kinetic modeling calculations. The model allows an analytic solution and lends itself to incorporation into existing compressible flow codes, at very little computational cost, for in-depth analysis of the nanosecond discharge plasma flow control mechanism. The use of the model would place the main emphasis on coupling of localized thermal perturbations produced by the discharge with the flow via compression waves and would provide quantitative insight into the flow control mechanism on a long time scale.

A REVIEW ON DIELECTRIC BARRIER DISCHARGE PLASMA FLOW CONTROL

Dielectric barrier discharge (DBD) plasma flow control is suited to the low velocity condition. It has a simple structure without mechanical parts, and has thus attracted much attention in research and industry institutions all over the world. DBD plasma flow control has been researched by many scholars in the recent 20 years, and there were a wealth of significant results on both plasma aerodynamic actuation mechanism and applications. In this paper, the physical process of dielectric barrier discharge and the essential mechanism of plasma aerodynamic actuation have been analyzed. Then the DBD plasma flow control, both the aerodynamic actuation mechanism and its applications in recent years, have been reviewed, and the plasma aerodynamic actuation mechanism was generalized in 3 main items. And the paper ends with a discussion about future development of the DBD plasma flow control.

Numerical Investigation of Plasma Plume Deflection with MHD Control

At present, NASA is engaged in research to develop Plasma flow control technology on aeronautic and astronautic scopes. This article presents a compositive MHD(magnetohydrodynamics) method to control high-velocity Plasma flow generate by alkali salts in combustion gas, demonstrates that MHD system can make the jet plume to deflect, and realizes the aeroengine thrust-vector purpose. By analyzing and applying the MHD mathematical model, the author performs the numerical simulation of plasma flows-field with the MHD condition，shows that the jet plume in plasma state can deflect with MHD.

Topological analysis of plasma flow control on corner separation in a highly loaded compressor cascade

In this paper, flow behavior and topology structure in a highly loaded compressor cascade with and without plasma aerodynamic actuation (PAA) are investigated. Streamline pattern, total pressure loss coefficient, outlet flow angle and topological analysis are considered to study the effect and mechanism of the plasma flow control on corner separation. Results presented include the boundary layer flow behavior, effects of three types of PAA on separated flows and performance parameters, topology structures and sequences of singular points with and without PAA. Two separation lines, reversed flow and backflow exist on the suction surface. The cross flow on the endwall is an important element for the corner separation. PAA can reduce the underturning and overturning as well as the total pressure loss, leading to an overall increase of flow turning and enhancement of aerodynamic performance. PAA can change the topology structure, sequences of singular points and their corresponding separation lines. Types II and III PAA are much more efficient in controlling corner separation and enhancing aerodynamic performances than type I.

Plasma flow control simulations of a low-Reynolds number low-aspect-ratio wing

Large-eddy simulation (LES) is employed to investigate use of plasma-based control in order to improve aerodynamic performance of a flat-plate wing. The wing has a rectangular planform, a thickness to chord ratio of 0.016, and an aspect ratio of 2.0. Computations are carried out at a chord-based Reynolds number of 20,000, such that the configuration and flow conditions are typical of those commonly utilized in micro air vehicle (MAV) applications. Solutions are obtained to the Navier–Stokes equations, that were augmented by source terms used to represent body forces imparted by plasma actuators on the fluid. A simple phenomenological model provided these body forces resulting from the electric field generated by the plasma. The numerical method is based upon a high-fidelity time-implicit scheme and an implicit LES approach, which are applied to obtain solutions on an overset mesh system. The control strategy explores plasma actuators that are distributed in the spanwise direction along the wing leading edge, and actuators extending in the chordwise direction along the wing tip. The investigation considers plasma-induced forces that are imposed in either the co-flowing or counter-flow directions for the former arrangement, and directed inboard or outboard for the latter. Both continuous and pulsed operation of actuators are simulated, and the magnitude of the plasma force is varied in order to establish the most efficient means of control. Computations are carried out at angles of attack that are below (8.0deg) and above (25.0deg) the stall value. Control solutions are compared with baseline results without actuation to determine the most beneficial control strategies. It was found that actuation is effective only for sufficiently large values of the plasma force. A favorable comparison is shown with the limited available experimental data.