The present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.

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Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control

The relationship between the upstream boundary layer and the low-frequency, large-scale unsteadiness of the separated flow in a Mach 2 compression ramp interaction is investigated by performing wide-field particle image velocimetry (PIV) and planar laser scattering (PLS) measurements in streamwise–spanwise planes. Planar laser scattering measurements in the upstream boundary layer indicate the presence of spanwise strips of elongated regions of uniform momentum with lengths greater than 40?. These long coherent structures have been observed in a Mach 2 supersonic boundary layer (Ganapathisubramani, Clemens & Dolling 2006) and they exhibit strong similarities to those that have been found in incompressible boundary layers (Tomkins & Adrian 2003; Ganapathisubramani, Longmire & Marusic 2003). At a wall-normal location of y/?=0.2, the inferred instantaneous separation line of the separation region is found to oscillate between x/?=?3 and ?1 (where x/?=0 is the ramp corner). The instantaneous spanwise separation line is found to respond to the elongated regions of uniform momentum. It is shown that high- and low-momentum regions are correlated with smaller and larger size of the separation region, respectively. Furthermore, the instantaneous separation line exhibits large-scale undulations that conform to the low- and high-speed regions in the upstream boundary layer. The low-frequency unsteadiness of the separation region/shock foot observed in numerous previous studies can be explained by a turbulent mechanism that includes these elongated regions of uniform momentum

Effects of upstream boundary layer on the unsteadiness of shock induced separation

A novel technique is proposed and investigated for the estimation of the body force field resulting from the operation of a dielectric barrier discharge plasma actuator. The technique relies on the measurement of the spatio-temporal evolution of the induced velocity field using high-speed particle image velocimetry (PIV). The technique has the advantage of providing spatial distribution of the body force vector field. A full Navier–Stokes term decomposition is applied on the evolving field along with additional closure norms in order to decouple the pressure gradient and body force terms. Results are compared with load-cell measurements of the direct reaction force and also momentum balance calculations based on the PIV field. Agreement between the different methods is observed. The data can easily be incorporated in computational flow solvers and also be used for validation and calibration of numerical plasma models.

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Measurement of the body force field of plasma actuators

Towards In-Flight Applications? A Review on Dielectric Barrier Discharge-Based Boundary-Layer Control

The popularity of plasma actuators as flow control devices has sparked a flurry of diagnostic efforts towards their characterisation. This review article presents an overview of experimental investigations employing diagnostic techniques specifically aimed at AC dielectric barrier discharge, DC corona and nanosecond pulse plasma actuators. Mechanical, thermal and electrical characterisation techniques are treated. Various techniques for the measurement of induced velocity, body force, heating effects, voltage, current, power and discharge morphology are presented and common issues and challenges are described. The final part of this report addresses the effect of ambient conditions on the performance of plasma actuators.

https://iopscience.iop.org/article/10.1088/0957-0233/26/9/092001/pdf

Diagnostics for characterisation of plasma actuators

The effects of micro-ramp height and location on a shock induced separation bubble were quantified using planar particle image velocimetry measurements. Conditional averaging was used to show that the amount of separation is related to the momentum flux in the near-wall region (< 0.5?) of the incoming boundary layer. The momentum flux added to this region scales linearly with micro-ramp height and larger microramps are shown to be more effective in stabilizing the interaction. Full boundary layer mixing is attained 5.? downstream of the micro-ramp and this forms a lower limit on the required distance between microramp and reflected shock foot.

/pdf/flow-control-of-an-oblique-shock-wave-reflection-with-micro-v1ul0bgf0j.pdf

Flow control of an oblique shock wave reflection with micro-ramp vortex generators: effects of location and size

This study investigates the influences of micro-ramp size and location on its effectiveness as a flow control device for oblique shock wave reflections The effectiveness is measured in terms of the size of the shock-induced separation bubble and the reflected shock unsteadiness Particle image velocimetry measurements were carried out on the interaction region and the mixing region between micro-ramp and interaction The separation bubble is shown to be most sensitive to the momentum flux contained in the lower 43% of the incoming boundary layer The momentum flux added to this region scales linearly with micro-ramp height and larger micro-ramps are shown to be more effective in stabilizing the interaction Full boundary layer mixing is attained 57δ downstream of the micro-ramp and this forms a lower limit on the required distance between micro-ramp and the start of the interaction region Typical reductions in the average separated area and the shock unsteadiness of 87% and 51%, respectively, were recorded Results, however, depend strongly upon the spanwise location, with the micro-ramp being most effective along its centerline

/pdf/flow-control-of-an-oblique-shock-wave-reflection-with-micro-27r11225ol.pdf

Flow control of an oblique shock wave reflection with micro-ramp vortex generators: Effects of location and size

A numerical investigation on the use of plasma actuators for transition control is presented. The numerical framework involves the solution of the full unsteady 2D incompressible Navier Stokes equations using a finite volume formulation. The set of equations is formulated by solving for the perturbations in the flow while a mean laminar boundary layer flow is considered fixed and superimposed. The effect of the plasma actuator is represented as an imposed unsteady body force distribution derived from experimental measurements. Furthermore, an adaptive control system based on the filtered-x LMS algorithm is implemented directly into the flow solver. The control system uses pressure signals at the wall in order to compute the frequency, phase and amplitude of the plasma body force which minimizes the intensity of the propagating TS waves. Results show large reductions in wave amplitude for both single and multi frequency cases.

/pdf/numerical-study-on-control-of-tollmien-schlichting-waves-oin894bmn2.pdf

Numerical Study on Control of Tollmien-Schlichting Waves Using Plasma Actuators

This study investigates the effects of boundary layer transition on an oblique shock wave reflection. The Mach number was 1.7, the unit Reynolds number was 35 × 106 m?1, and the pressure ratio over the interaction was 1.35. Particle image velocimetry is used as the main flow diagnostics tool, supported by oil-flow and Schlieren visualizations. At these conditions, the thickness of the laminar boundary layer is only 0.2 mm, and seeding proved to be problematic as practically no seeding was recorded in the lower 40 % of the boundary layer. The top 60 % could, however, still be resolved with good accuracy and is found to be in good agreement with the compressible Blasius solution. Due to the effects of turbulent mixing, the near-wall seeding deficiency disappears when the boundary layer transitions to a turbulent state. This allowed the seeding distribution to be used as an indicator for the state of the boundary layer, permitting to obtain an approximate intermittency distribution for the boundary layer transition region. This knowledge was then used for positioning the oblique shock wave in the laminar, transitional (50 % intermittency) or turbulent region of the boundary layer. Separation is only recorded for the laminar and transitional interactions. For the laminar interaction, a large separation bubble is found, with a streamwise length of 96 ??i,0 . The incoming boundary layer is lifted over the separation bubble and remains in a laminar state up to the impingement point of the shock wave. After the shock, transition starts and a turbulent profile is reached approximately 80–90 ??i,0 downstream of the shock. Under the same shock conditions, the transitional interaction displays a smaller separation bubble (43 ??i,0 ), and transition is found to be accelerated over the separation bubble.

https://link.springer.com/content/pdf/10.1007%2Fs00348-015-1977-8.pdf

High-resolution PIV measurements of a transitional shock wave–boundary layer interaction

The use of plasma actuators for active transition control in a flat-plate boundary layer is studied numerically. The full unsteady two-dimensional incompressible Navier–Stokes equations are solved with a perturbation formulation using a finite volume discretization. The effect of the plasma actuator is modeled using generic as well as experimentally derived body force distributions. An adaptive control system based on the filtered-x least-mean-squares algorithm is included within the simulations. The control system selects the optimum frequency, phase, and amplitude of the body force in order to attenuate Tollmien–Schlichting instability waves. The factors influencing the effectiveness of transition control are discussed. It is shown that the relative size of the instability wavelength and the spatial extent of the body force have a strong influence on control performance. It is also demonstrated that the experimentally derived force distributions produce suboptimal control performance when compared with ...

/pdf/numerical-study-of-the-control-of-tollmien-schlichting-waves-1rh3pfhi9x.pdf

Rogier Giepman

Papers

Flow control of an oblique shock wave reflection with micro-ramp vortex generators: effects of location and size

Flow control of an oblique shock wave reflection with micro-ramp vortex generators: Effects of location and size

Numerical Study on Control of Tollmien-Schlichting Waves Using Plasma Actuators

High-resolution PIV measurements of a transitional shock wave–boundary layer interaction

Numerical Study of the Control of Tollmien-Schlichting Waves Using Plasma Actuators