K. Barckmann

Dielectric- Barrier Discharge Plasmas for Flow Control at Higher Mach Numbers

The main aim of this study is to investigate the control authority of Dielectric-Barrier Discharge (DBD) plasma actuators at higher Mach numbers and higher Reynolds numbers. Different strategies are pursued to influence the flow, all attempting to create coherent structures to transport momentum from the freestream into the near-wall region of the boundary-layer. To achieve this various actuator geometries and configurations are used and tested on a NACA0012 airfoil. To obtain a better insight into the effects limiting the actuator performance under high-speed flow conditions, separate investigations on a flat plate are presented.

Competition between pressure effects and airflow influence for the performance of plasma actuators

The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p = 0.1–1 bar) and airflow velocities ( U ∞ = 0 − 100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

Closed-Loop Performance Control of Dielectric-Barrier-Discharge Plasma Actuators

The counteraction of changing environmental conditions (i.e., changes of pressure level and airflow speed) on the resulting plasma-actuator performance is demonstrated in the present work. The impact of these changing (fluctuating and/or transient) airflow conditions on the performance of dielectric-barrier-discharge plasma actuators is suppressed using a novel closed-loop performance-control procedure. The goal of controlling a preset plasma-actuator performance online and in situ is achieved and successfully demonstrated. This novel approach represents the first step toward optimal-discharge-based flow control because, beyond the common purpose of favorably manipulating the airflow, any advanced dielectric-barrier-discharge-based flow-control system will necessarily require an appropriate closed-loop performance control of the discharge device.

Simultaneous Investigation of Pressure Effects and Airflow Influence on DBD Plasma Actuators

The present work addresses the combined influence of pressure variations and different airflow velocities on the performance of plasma actuators. Varying pressure levels (p = 0.1 1 bar) and airflow velocities (U1 = 0 100 m/s) were investigated systematically to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the control authority of plasma actuators for flow control applications.

Evaluating force field induced by a plasma actuator using the Reynolds-Averaged Navier Stokes Equation

This article discusses the suitability of deriving the force density distributions produced by plasma actuators using velocity field data obtained experimentally by Particle Image Velocimetry (PIV). It is argued that the Navier-Stokes equations (NS) are not correct choice, since the requirements for their application are not met by the time-averaged properties of the available velocity field. The Reynolds Averaged Navier Stokes Equation (RANS) are considered more appropriate in which case the Reynolds stress components must also be accounted for in calculating the force density distribution.

Closed-Loop Performance Control of DBD Plasma Actuators

The impact of fluctuating airflow conditions on the performance of dielectric barrier discharge (DBD) plasma actuators is suppressed using a novel closed-loop performance control procedure. The goal of controlling the plasma actuator performance online and in-situ is achieved and successfully demonstrated. This novel approach represents a first step towards optimal discharge based flow control, since beyond the common purpose of favorably manipulating the airflow, any advanced DBD-based flow control system will necessarily require an appropriate closed-loop performance control of the discharge device.