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NUMERICAL SIMULATION OF TWO FLOW CONTROL APPROACHES FOR LOW REYNOLDS NUMBER APPLICATIONSReasor Jr., Daniel A. 01 January 2007 (has links)
Current research in experimental and computational fluid dynamics is focused in the area of flow control. Flow control devices are usually classified as either passive or active. Plasma actuators are active flow control devices that require input from an external power source. Current efforts have modeled the effects of plasma actuators as a body force near the electrode. The research presented herein focuses on modeling the fluid-plasma interaction seen in dielectric barrier discharge plasma actuators as a body force vector in the region above the embedded electrode using computational fluid dynamics (CFD). This body force is modeled as the product of the gradient of the potential due to the electric field and the net charge density. In a passive flow control study, two-dimensional simulations using CFD are done with a smooth and bumpy Eppler 398 airfoil with laminar, transition, and turbulent models in an effort to improve the understanding of the flow over bumpy airfoils and to quantify the advantages or disadvantages of the bumps.
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Development of dielectric barrier discharge plasma actuators and their application at subsonic speedsHale, Craig January 2012 (has links)
Plasma actuators are electrical devices that generate a wall bounded jet without the use of any moving parts. For aerodynamic applications they can be used as flow control devices to delay separation and augment lift on a wing. The aim of this project is to initially develop a system capable of generating and sustaining a plasma that generates a wall bounded jet. The next step is to investigate the effect of varying the number and distribution of encapsulated electrodes in the dielectric layer. Finally the best case design is applied at the leading edge and flap shoulder of a NACA0015 aerofoil with a 20% flap. Utilising a transformer cascade, plasma has been generated for a variety of input voltages. In the quiescent environment of a Faraday cage the velocity flow field is recorded using particle image velocimetry (PIV). Through understanding of the mechanisms involved in producing the wall jet and the importance of the encapsulated electrode a novel actuator design was investigated. The actuator design distributes the encapsulated electrode throughout the dielectric layer. The experiments have shown that actuators with shallow initial encapsulated electrodes induce velocities greater than the baseline case at the same voltage. Actuators with a deep initial electrode are able to induce the highest velocities as they can operate at higher voltages without breakdown of the dielectric. The best actuator case is applied to the aerofoil for Reynolds numbers of 1:97x10⁵, 2:63x10⁵ and 3:29x10⁵. The lift and drag are recorded using pressure measurements around the aerofoil surface and across the aerofoil's wake. PIV is utilised to visualise the flow field. The trailing edge actuator produces a step increase in lift for pre-stall angles of attack and delays stall by 1° at Re = 1:97x10⁵. The leading edge actuator has limited impact on the flow for the no flap deflection case due to the actuator location. As the flap deflection increases the leading edge actuator is able to influence the flow. Repositioning of the leading edge actuator has the ability to reattach the flow around the fore portion of the aerofoil at a post stall angle of alpha = 18°.
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Understanding Flow Physics and Control in an Aggressively Offset High-Speed Inlet/Diffuser ModelO'Neill, Collin James 06 October 2020 (has links)
No description available.
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Unsteady Flow Separation Control over a NACA 0015 using NS-DBD Plasma ActuatorsSinghal, Achal Sudhir 23 May 2017 (has links)
No description available.
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High Subsonic Cavity Flow Control Using Plasma ActuatorsYugulis, Kevin Lee 31 August 2012 (has links)
No description available.
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CHARACTERIZATION AND FLOW PHYSICS OF PLASMA SYNTHETIC JET ACTUATORSSanthanakrishnan, Arvind 01 January 2007 (has links)
Plasma synthetic jet actuators are investigated experimentally, in which the geometrical design of single dielectric barrier discharge (SDBD) plasma actuators is modified to produce zero-mass flux jets similar to those created by mechanical devices. The SDBD plasma actuator consists of two rectangular electrodes oriented asymmetrically and separated by a layer of dielectric material. Under an input of high voltage, high frequency AC or pulsed DC, a region of plasma is created in the interfacial air gap on account of electrical breakdown of the ambient air. A coupling between the electric field in the plasma and the neutral air near the actuator is introduced, such that the latter experiences a net force which results in a horizontal wall jet. This effect of the actuator has been demonstrated to be useful in mitigating boundary layer separation in aerodynamic flows. To increase the impact that a plasma actuator may have on the flow field, this research investigates the development and characterization of a novel flow control device, the plasma synthetic jet actuator, which tailors the residual air in the form of a vertical jet resembling conventional continuous and synthetic jets. This jet can be either three dimensional using annular electrode arrays, or nearly two dimensional using two rectangular strip exposed electrodes and one embedded electrode. Detailed measurements on the isolated plasma synthetic jet reveal that pulsed operation of the actuator results in the formation of multiple counterrotating vortical structures in the flow field. The output jet velocity and momentum are found to be higher for unsteady pulsing as compared to steady operation. In the case of flow over a flat plate, the actuator is observed to create a localized interaction region within which the baseline flow direction and boundary layer characteristics are modified. The efficiency of the actuator in coupling momentum to the neutral air is found to be related to the plasma morphology, pulsing frequency, actuator dimension, and input power. An analytical scaling model is proposed to describe the effects of varying the above variables on the output jet characteristics and actuator efficiency, and the experimental data is used for model validation.
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Experimental Study Of Plasma Actuator Characteristics And Optimization Of ConfigurationPradeep, M 07 1900 (has links) (PDF)
Plasma actuators are devices which function by creating a discharge in air at atmospheric conditions. These devices have been demonstrated to effectively delay flow separation and enhance the lift- drag characteristics of wing sections. They have also been shown to have potential
applications in controlling dynamic stall, flow separation control over turbine blades, flow vectoring, boundary layer manipulation and bluff body flow control.
This study examines the characteristics of the plasma actuator, its working and the optimization of its configuration for its use as a lift enhancing device. A single actuator connected to a high-voltage, high-frequency power supply was studied in quiescent conditions. It was demonstrated by means of flow visualization experiments and hot-wire anemometry that the plasma actuator functions by inducing a flow, thus behaving as a source of momentum flux in any system that it is introduced into. Further, it was inferred that the flow induced is a wall jet and that the magnitude of the velocity achieved is maximum within a few millimeters of the surface of the actuator. A parametric investigation of the actuator was conducted next. The variation of the peak velocity induced in quiescent conditions with the variation of configuration parameters was studied by means of photographic studies and hot-wire anemometry. These experiments
indicated that there is a strong correlation between the visible extent of the plasma along the direction of the induced _ow (plasma width) and the peak velocity achieved. The peak velocity achieved is found to increase with the increase in the plasma width as long as the discharge
created is in the uniform glow discharge regime. The development of localized high intensity streamers, which destroy the uniformity of the plasma, lead to a loss in the peak velocity.
Hot-wire tests indicated that the peak velocity increases with a decrease in the spanwise overlap of the electrodes, with the other parameters kept constant. Also, in the uniform glow discharge regime, the velocity increases with the increase in the thickness of the dielectric placed between the two electrodes. After a particular optimum thickness, further increase of the thickness leads to formation of streamers. The velocity increased with a decrease in streamwise overlap, with the maximum being reached for a overlap of approximately 2mm, after which it remained a constant. It was observed that the absence of overlap leads to a loss of uniformity of the discharge created. The velocity was found to be independent of the variations in the electrode widths. Particle Image Velocimetry (PIV) was conducted to study the characteristics of the jet produced. It was observed that when the actuator is switched on, a low pressure region is created near the
surface of the actuator, vertically above it, leading to a flow towards this region from above the actuator. Furthermore, a vortex is shed, which is convected downstream, after which a wall jet is established close to the dielectric surface.
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Control of Hypersonic High Angle-Of-Attack Re-Entry Flow Using a Semi-Empirical Plasma Actuator ModelAtkinson, Michael D. 11 May 2012 (has links)
No description available.
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Parametric Study of the Effects of the Flapping Mode Excitation on the Near Field Structures of a Mach 1.3 Cold JetSpeth, Rachelle Lea 25 June 2012 (has links)
No description available.
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Simulations of Plasma Creating Electric WindSellerholm, Linnéa, Stenberg, Amanda January 2021 (has links)
Plasma actuators are devices that with two electrodesand a dielectric material can ionize the air around itand thus control the airflow. They have considerable potentialfor a multitude of reasons, one of which being that they haveno moving parts, making them easy to produce and hard tobreak. Using this technology on the front of vehicles like truckscould be revolutionary in increasing fuel efficiency and thusreducing emissions. A model of a plasma actuator in COMSOLMultiphysics was used to simulate the effect it has on the airaround it. The focus of the project has been to optimize thedesign of an actuator for increased velocity in the air around it.This has been done with regards to properties of the appliedvoltage, the distance between the electrodes and material ofthe dielectric. Parametric analyses of all the above propertieswas performed. Close-to-optimal values of some of the abovementioned parameters were successfully calculated. However,other parameters, such as the horizontal distance between theelectrodes, were beyond the model’s capability to determine usingthe described method. / Plasmaställdon är anordningar som medtvå elektroder och ett dielektriskt material kan jonisera luftenrunt sig och på detta sätt styra luftflödet. De har betydandepotential av en mängd anledningar, varav en är att de inte har några rörliga delar, vilket gör dem lätta att producera och ochsvåra att förstöra. Användande av denna teknologi på fronterav fordon som lastbilar skulle kunna vara revolutionerande förökad bränsleeffektivitet och därmed minska utsläpp. En modellav ett plasmaställdon i COMSOL Multiphysics användes för attsimulera effekterna den har på luften runt sig. Projektets fokushar varit på att optimera ett ställdons design för ökad hastigheti luften runt den. Detta har gjorts med avseende på egenskaperhos den tillförda spänningen, avståndet mellan elektroderna ochdielektrikumets material. Parametriska analyser för alla dessaegenskaper har genomförts. Nästintill optimala värden för någraav de ovan nämnda parametrarna beräknades med framgång.Andra parametrar, som det horisontella avståndet mellan elektroderna,var bortom modellens förmåga att bestämma vidanvändande av den beskrivna metoden. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm
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