Conference Paper

Plasma Actuator with Arc Breakdown in a Magnetic Field for Active Flow Control Applications

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... This paper summarizes the most recent experimental investigations performed for the development of the cyclotronic plasma actuator, and is a continuation of the recently reported work [32][33][34][35]; the technology was recently patented [36]. Early work evaluated the actuator configuration in low-speed wind tunnel tests using PIV in a zeropressure gradient boundary layer, as well as pressure recovery measurements with the actuator placed upstream of an expansion ramp [32]. ...
... This paper summarizes the most recent experimental investigations performed for the development of the cyclotronic plasma actuator, and is a continuation of the recently reported work [32][33][34][35]; the technology was recently patented [36]. Early work evaluated the actuator configuration in low-speed wind tunnel tests using PIV in a zeropressure gradient boundary layer, as well as pressure recovery measurements with the actuator placed upstream of an expansion ramp [32]. It was observed that the actuator acts to introduce a local velocity defect immediately downstream of the actuator location. ...
... Initial work applied a GBS Minpuls 2.2 system and also a 60 Hz neon sign transformer as high-voltage driver circuits for the actuators [32]. The recent work has focused on more compact circuits that can readily be configured to power arrays of actuators. ...
... This paper summarizes the most recent experimental investigations performed for the development of the cyclotronic plasma actuator. The experiments discussed here are a continuation of the recently reported work [32][33][34] which evaluated the actuator configuration in low-speed wind tunnel tests using PIV in a zero-pressure gradient boundary layer, as well as pressure recovery measurements with the actuator placed upstream of an expansion ramp. It was observed that the actuator acts to introduce a local velocity defect immediately downstream of the actuator location. ...
... By placing this detector above the coaxial actuator, collimated to view one segment of the arc path, and passing the output to an oscilloscope through an amplifier stage, a frequency signal corresponding to the rotation rate of the arc was measured, as the detector responded to the emission from the arc as it passed through the collimated region. This same sensor was used to measure low frequency pulsing of the discharge in preliminary work by viewing the entire actuator [32]. An alternative method applied a ferrite-core (215 H) inductor to sense the disturbance of the magnetic field near the actuator as the arc rotated [33]. ...
... Initial work applied a GBS Minpuls 2.2 system and also a neon sign transformer as a means to power the actuators [32]. Recent work has focused on more compact circuits that can readily be configured to power arrays of actuators. ...
... This paper summarizes the most recent experimental bench tests performed for study of the cyclotronic plasma actuator. The experiments discussed here are a continuation of the recently reported work [32,33]. Earlier studies evaluated the actuator configuration in low-speed wind tunnel tests using PIV in a zero-pressure gradient boundary layer, as well as pressure recovery measurements with the actuator placed upstream of an expansion ramp [32]. ...
... The experiments discussed here are a continuation of the recently reported work [32,33]. Earlier studies evaluated the actuator configuration in low-speed wind tunnel tests using PIV in a zero-pressure gradient boundary layer, as well as pressure recovery measurements with the actuator placed upstream of an expansion ramp [32]. It was observed that the actuator acts to introduce a local velocity defect immediately downstream of the actuator location. ...
... It was observed that the actuator acts to introduce a local velocity defect immediately downstream of the actuator location. Subsequent recovery in near-wall streamwise velocity was then observed, where actuation produces a higher streamwise velocity in the region immediately adjacent to the wind tunnel wall [32]. This velocity defect and recovery is believed to be linked to the formation of streamwise vortex structures induced by the actuation, with similarities to velocity profile development downstream of passive vortex generators [34]. ...
... This paper summarizes the most recent experimental investigations performed for the development of the cyclotronic plasma actuator. The experiments discussed here are a continuation of the recently reported work [32] which evaluated the actuator configuration in low-speed wind tunnel tests using PIV in a zero-pressure gradient boundary layer, as well as pressure recovery measurements with the actuator placed upstream of an expansion ramp. It was observed that the actuator acts to introduce a local velocity defect immediately downstream of the actuator location. ...
... By placing this detector above the coaxial actuator, collimated to view one segment of the arc path, and passing the output to an oscilloscope through an amplifier stage, a frequency signal corresponding to the rotation rate of the arc was measured, as the detector responded to the emission from the arc as it passed through the collimated region. This same sensor was used to measure low frequency pulsing of the discharge in prior work by viewing the entire actuator [32]. An alternative method applied a ferrite-core (215 H) inductor to sense the disturbance of the magnetic field near the actuator as the arc rotated. ...
... Previous work applied a GBS Minpuls 2.2 system and also a neon sign transformer as a means to power the actuators [32]. Recent work has focused on more compact circuits that can readily be configured to power arrays of actuators. ...
... Non-thermal plasma devices can offer strategies for flow control [1][2][3][4][5][6][7]. Amongst active flow control devices, plasma actuators have the potential to control a fluid system while staying silent, instantaneous, and compact [8][9][10]. ...
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Dielectric barrier discharge (DBD) plasma actuators can generate a wall jet without moving parts through interaction between ionized and neutral molecules in an electric field. The coupling between electro-hydrodynamic, turbulence, and viscous effects in the flow boundary layer remains unclear and deserves careful investigation. We present an experimental investigation of momentum injection by DBD actuators in a U_external = 5 m/s and U_external = 11 m/s co-flow and counter-flow configuration over a range of VAC = 12 kV - 19.5 kV peak-to-peak at a frequency of 2 kHz. In the co-flow configuration, the DBD actuator adds momentum to the boundary layer, similar to an electrohydrodynamic (EHD) jet in quiescent conditions. In the counter-flow configuration, flow separation is observed at free stream velocity U_external = 5 m/s. The momentum displacement in the counter-flow configuration is ~ 6x greater than EHD jet momentum in a quiescent environment. Both co-flow and counter-flow momentum injections show diminishing effects with increased external flow speed. This work highlights that the resulting flow pattern is not a simple superposition of the EHD jet and the free stream but is determined by a balance between the inertial, viscous and Coulombic forces of the EHD and the external flow. The velocity profiles and momentum characteristics can be used to validate numerical models and inform the design of DBD actuators for active flow control.
... Over the past decade, there has been a great interest in using non-thermal plasma actuators for active flow control of aerodynamic surfaces [1][2][3][4][5][6][7]. Plasma actuators have the potential to control a fluid system while staying silent, instantaneous, and compact [8][9][10]. ...
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The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single–dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body-force vector field that couples with the momentum in the external flow. The body force can be derived from first principles, and the effect of plasma actuators can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of internal and external flow applications. Although initially considered useful only at low speeds, plasma actuators are effective in a number of applications at high subsonic, transonic, and supersonic Mach numbers, owing largely to more optimized actuator designs that were developed through better understanding and modeling of...
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The control of boundary layer separation on the suction side of an airfoil at high angle of attack has been renewed by the possibilities of active control. Nevertheless, such an active control needs a deep understanding of the flow to manipulate and of the actuating flow, both being 3D and unsteady. For that purpose, a model experiment has been designed in the frame of a coordinated European project called AEROMEMS, with a simpler (2D) geometry and with a dilatation of the scales in order to be able to characterize the actuation flow. This model is a bump in a boundary layer wind tunnel, which mimics the adverse pressure gradient on the suction side of an airfoil at the verge of separation. The present contribution describes preliminary tests done to optimize standard passive devices before testing active systems. The optimization was done with hot film shear stress probes, the characterization with hot wire anemometry and PIV. The results show quantitatively the improvement brought by the passive devices in terms of skin friction. They also show the mechanism which is at the origin of this improvement. The next step of the project is to replace passive devices by synthetic jets.
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An in-depth review of boundary-layer flow-separation control by a passive method using low-profile vortex generators is presented. The generators are defined as those with a device height between 10% and 50% of the boundary-layer thickness. Key results are presented for several research efforts, all of which were performed within the past decade and a half where the majority of these works emphasize experimentation with some recent efforts on numerical simulations. Topics of discussion consist of both basic fluid dynamics and applied aerodynamics research. The fluid dynamics research includes comparative studies on separation control effectiveness as well as device-induced vortex characterization and correlation. The comparative studies cover the controlling of low-speed separated flows in adverse pressure gradient and supersonic shock-induced separation. The aerodynamics research includes several applications for aircraft performance enhancement and covers a wide range of speeds. Significant performance improvements are achieved through increased lift and/or reduced drag for various airfoils—low-Reynolds number, high-lift, and transonic—as well as highly swept wings. Performance enhancements for non-airfoil applications include aircraft interior noise reduction, inlet flow distortion alleviation inside compact ducts, and a more efficient overwing fairing. The low-profile vortex generators are best for being applied to applications where flow-separation locations are relatively fixed and the generators can be placed reasonably close upstream of the separation. Using the approach of minimal near-wall protuberances through substantially reduced device height, these devices can produce streamwise vortices just strong enough to overcome the separation without unnecessarily persisting within the boundary layer once the flow-control objective is achieved. Practical advantages of low-profile vortex generators, such as their inherent simplicity and low device drag, are demonstrated to be critically important for many applications as well.
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The paper demonstrates several ways of use of the UV–vis optical emission spectroscopy of medium resolution for the diagnostics of atmospheric pressure air and nitrogen plasmas relevant to bio-medical and environmental applications. Plasmas generated by DC discharges (streamer corona, transient spark, and glow discharge), AC microdischarges in porous ceramics, and microwave plasma were investigated. Molecular (OH, NO, CN) and atomic (H, O, N) radicals, and other active species, e.g. N2 (C, B, A), (B), were identified. The composition of the emission spectra gives insight in the ongoing plasma chemistry. Rotational, i.e. gas, and vibrational temperatures were evaluated by fitting experimental with simulated spectra. Streamer corona, transient spark and microdischarges generate cold, strongly non-equilibrium plasmas (300–550 K), glow discharge plasma is hotter, yet non-equilibrium (1900 K), and microwave plasma is very hot and thermal (∼3000–4000 K). Electronic excitation temperature and OH radical concentration were estimated in the glow discharge assuming the chemical equilibrium and Boltzmann distribution (9800 K, 3 × 1016 cm−3). Optical emission also provided the measurement of the active plasma size of the glow discharge, and enabled calculating its electron number density (1012 cm−3).
Pulsed-DC Plasma Actuator Characteristics and Application in Compressor Stall Control
  • R Mcgowan
  • T C Corke
  • E Matlis
  • R Kaszeta
  • C Gold
McGowan, R., Corke, T.C., Matlis, E., Kaszeta, R., and Gold, C., "Pulsed-DC Plasma Actuator Characteristics and Application in Compressor Stall Control," AIAA Paper 2016-0394, 2016.
Simulations of Plasma-Assisted Combustion Flames in Coaxial Microwave Reactors
  • J Zimmerman
  • A Palla
  • D King
  • D Carroll
  • C Mitsingas
  • S Hammack
Zimmerman, J., Palla, A., King, D., Carroll, D., Mitsingas, C., Hammack, S., and Lee T., "Simulations of Plasma-Assisted Combustion Flames in Coaxial Microwave Reactors," 54 th AIAA Aerospace Sciences Meeting, 4-8 January 2016, San Diego, CA (AIAA 2016-0190).
automatic three-dimensional finite element mesh generator, Software Package, Ver. 2.8.5, copyright C
  • Gmsh
Gmsh, automatic three-dimensional finite element mesh generator, Software Package, Ver. 2.8.5, copyright C. Geuzaine and J.-F. Remacle, 2014