Measurement of the body force field of plasma actuators

Kotsonis, Marios; Ghaemi, Sina; Veldhuis, L.L.M.; Scarano, Fulvio

doi:10.1088/0022-3727/44/4/045204

Cited by 146 publications

(102 citation statements)

References 28 publications

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“…For estimatingĨ at each voltage, PIV measurements are carried out in quiescent conditions with the actuator operating continuously atf c = 5kHz.Ĩ is then calculated as described by Kotsonis et al (2011) to the appropriate control volume, assuming uniform pressure distribution. It should be noted here, that the described momentum coefficient is calculated based on continuous operation of the actuator and, as such, pertains to the mechanical power of the actuator.…”

Section: Ac-dbd Forcingmentioning

confidence: 99%

Response of a laminar separation bubble to impulsive forcing

2017

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The spatial and temporal response characteristics of a laminar separation bubble to impulsive forcing are investigated by means of time-resolved particle image velocimetry and linear stability theory. A two-dimensional impulsive disturbance is introduced with an AC dielectric barrier discharge plasma actuator, exciting pertinent instability modes and ensuring flow development under environmental disturbances. Phase-averaged velocity measurements are employed to analyse the effect of imposed disturbances at different amplitudes on the laminar separation bubble. The impulsive disturbance develops into a wave packet that causes rapid shrinkage of the bubble in both upstream and downstream directions. This is followed by bubble bursting, during which the bubble elongates significantly, while vortex shedding in the aft part ceases. Duration of recovery of the bubble to its unforced state is independent of the forcing amplitude. Quasi-steady linear stability analysis is performed at each individual phase, demonstrating reduction of growth rate and frequency of the most unstable modes with increasing forcing amplitude. Throughout the recovery, amplification rates are directly proportional to the shape factor. This indicates that bursting and flapping mechanisms are driven by altered stability characteristics due to variations in incoming disturbances. The emerging wave packet is characterised in terms of frequency, convective speed and growth rate, with remarkable agreement between linear stability theory predictions and measurements. The wave packet assumes a frequency close to the natural shedding frequency, while its convective speed remains invariant for all forcing amplitudes. The stability of the flow changes only when disturbances interact with the shear layer breakdown and reattachment processes, supporting the notion of a closed feedback loop. The results of this study shed light on the response of laminar separation bubbles to impulsive forcing, providing insight into the attendant changes of flow dynamics and the underlying stability mechanisms.

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Section: Ac-dbd Forcingmentioning

confidence: 99%

Response of a laminar separation bubble to impulsive forcing

2017

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“…The technique is based on the periodicity of the plasma forcing effect as proved in numerous previous studies. 16,17 More specifically, the sampling rate f s is kept fixed at 6 kHz while the actuator carrier frequency f ac is chosen such that the ratio r ¼ f s /f ac is not an integer value. In this manner, the phase of every measured point is slightly shifted between successive actuation signal cycles.…”

Section: -2mentioning

confidence: 99%

Forcing mechanisms of dielectric barrier discharge plasma actuators at carrier frequency of 625 Hz

Kotsonis

Ghaemi

2011

Journal of Applied Physics

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The forcing behavior of a dielectric barrier discharge (DBD) actuator is investigated experimentally using a time-resolved particle image velocimetry (PIV) system in conjunction with a phase shifting technique. The spatio-temporal evolution of the induced flowfield is accurately captured within one high voltage (HV) cycle allowing the calculation of the instantaneous velocity and acceleration. Additional voltage and current measurements provide the power consumption for each case. Four different applied voltage waveform shapes are independently tested, namely, sine, square, positive sawtooth, and negative sawtooth at fixed applied voltage (10 kV pp ) and carrier frequency (625 Hz). The instantaneous flowfields reveal the effect of the plasma forcing during the HV cycle. Sine waveform provides large positive forcing during the forward stroke, with minimal but still positive forcing during the backward stroke. Square waveform provides strong and concentrated positive and negative forcing at the beginning of the forward and backward stroke, respectively. Positive sawtooth provides positive but weak forcing during both strokes while the negative sawtooth case produces observable forcing only during the forward stroke. Results indicate the inherent importance of negative ions on the force production mechanisms of DBD's. Furthermore, the revealed influence of the waveform shape on the force production can provide guidelines for the design of custom asymmetric waveforms for the improvement of the actuator's performance.

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“…This point has been discussed in Brauner et al [28] and it was shown that the pressure gradient can contribute to the mean EHD volume force. The contribution of the pressure gradient in the computation of the EHD force has also been partially discussed in the pioneering work of [22]. It was shown that convection and pressure gradient are initially negligible, but the influence of the pressure gradient can increase with time.…”

Section: Iii-1 Principle Of Piv-based Estimation Of the Volume Ehd Forcementioning

confidence: 99%

“…The most straightforward strategy for evaluating the EHD volume force is based on the two-dimensional incompressible Navier-Stokes equations. Assuming that the pressure gradients are much smaller that the force components, they can be neglected as initially proposed in [21] and because all the other components of the Navier-Stokes equations can be computed from the experimental data, the 2D spatial distribution of the mean force component can be evaluated fairly easily [22][23][24][25]. In most of the cases, time-averaged velocity fields are measured, but phase-averaging procedure can also be used to recover the dynamic aspects of the EHD volume force [26][27].…”

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confidence: 99%

PIV-based dynamic model of EHD volume force produced by a surface dielectric barrier discharge

Bénard

Laizet

Moreau

2017

55th AIAA Aerospace Sciences Meeting

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In this paper, an experimental measurement of the flow produced by a surface DBD plasma actuator has been conducted. One original aspect of these measurements by particle image velocimetry is the high acquisition rate for a PIV system (20 kHz). By using these highlyresolved flow measurements, the fluid flow velocity is used to estimate the spatial and temporal evolution of the EHD volume force. A reduced order model of this force has been constructed by proper orthogonal decomposition. Based on the analysis of the time-resolved expansion coefficients and their associated spatial modes, it is shown that the volume force can be reconstructed by using a limited number of POD modes (6 modes). This spatial and temporal filtering of the force fields remains faithful to the original data and it will help in view of an implementation of such a source term in a numerical solver. The resulting dynamic model shows an alternation of positive and negative volume forces. The strong positive EHD force developing in the glow regime of the DBD plasma discharge is visualized in a time-resolved manner. This positive force is immediately followed by a strong negative volume force probably caused by the local flow deceleration.I. Introduction he magnitude, spatial distribution, and time evolution of the body force produced by plasma discharge propagating over dielectric wall are essential mechanical characteristics when these discharges are used to superimpose periodic perturbations to a fluid flow in view of its manipulation. A deep knowledge of these quantities can help in optimizing this type of electrical discharge by experiments and it can provide the information for defining a relevant model of plasma actuator. Here, the proposed study relates to the well-known dielectric barrier discharge plasma actuator where two conductive electrodes are placed asymmetrically on both sides of a dielectric barrier [1][2][3][4]. In a basic view, because of the alternative high amplitude electric field, gas ionization occurs and the displacement of the charged particles under the influence of the electric field transfers fluid momentum through a volume force referred as electrohydrodynamic (EHD) force. In fact, such an electrical discharge involves electrical, mechanical, thermal and chemical mechanisms and is a complex multi-physics problem [5]. Numerical modelling of these discharges is not an easy task. In order to model the physical mechanisms of a plasma actuator first principle based methods can be used. By computing the solution of complex transport equations for both charged and neutral species, the solution of a Poisson equation for the electric field, and finally coupling the EHD force to the fluid by using Navier-Stokes equations, the electromechanical conversion of plasma actuators can be modeled [6][7][8]. This approach is complex and time-consuming for non-parallelized code, limiting its

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Measurement of the body force field of plasma actuators

Cited by 146 publications

References 28 publications

Response of a laminar separation bubble to impulsive forcing

Response of a laminar separation bubble to impulsive forcing

Forcing mechanisms of dielectric barrier discharge plasma actuators at carrier frequency of 625 Hz

PIV-based dynamic model of EHD volume force produced by a surface dielectric barrier discharge

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