Jochen Kriegseis

Power consumption, discharge capacitance and light emission as measures for thrust production of dielectric barrier discharge plasma actuators

A new procedure of determining the time resolved capacitance of a plasma actuator during operation is introduced, representing a simple diagnostic tool that provides insight into the phenomenological behavior of plasma actuators. The procedure is demonstrated by presenting example correlations between consumed electrical energy, size of the plasma region, and the operating voltage. It is shown that the capacitance of a plasma actuator is considerably increased by the presence of the plasma; hence a system that has previously been impedance matched can be considerably de-tuned when varying the operating voltage of the actuator. Such information is fundamental for any attempts to increase the energy efficiency of plasma-actuator systems. A combined analysis of the capacitance, light emission, size of the plasma region, force production, and power consumption is presented.

Velocity-information-based force-term estimation of dielectric-barrier discharge plasma actuators

Particle image velocimetry measurements in close proximity to dielectric-barrier discharge plasma actuators are conducted to quantify the momentum transfer of the plasma to the surrounding air flow. Based on these data a comparative analysis of six existing approaches to estimate the induced body force is presented. Integral methods calculate an integral value for the actuator force based on the momentum-balance equation. Insight into the spatial distribution of the body force is provided by differential methods, which are based either on the Navier–Stokes equations or on the vorticity equation. It is demonstrated that the intensity as well as the domain of the force increase with increasing operating power levels. Emphasis is also placed on the issue of self-induced drag. It is shown that 30% of the induced momentum is consumed by wall friction. All results are validated with previously obtained balance force data and luminosity analysis of identical actuators.

PIV-based estimation of DBD plasma-actuator force terms

PIV measurements in close proximity to dielectric-barrier discharge plasma actuators have been conducted to quantify the momentum transfer of the plasma to the surrounding air flow. Based on this data a comparative analysis of six existing approaches to estimate the induced body force is presented. Integral methods calculate an integral value for the actuator force based on the momentum balance equation. Insight into the spatial distribution of the body force is provided by differential methods, which are based either on the Navier-Stokes equations or on the vorticity equation. It is demonstrated that the intensity as well as the domain of the force increase with increasing operating power levels. Emphasis is also placed on the issue of self-induced drag. It is shown that 30% of the induced momentum is consumed by wall friction. All results are validated with previously obtained balance force data and luminosity analysis of the identical actuators.

On the classification of dielectric barrier discharge plasma actuators: A comprehensive performance evaluation study

The increasing popularity and maturity of plasma actuators for many flow control applications requires a common standard for plasma actuator performance evaluation. In the present work, a comprehensive comparative study of existing and new evaluation measures is presented, based on results from identical plasma-actuator configurations. A power-flow diagram is introduced that covers the entire range of power stages from the energy source to the flow-control success. All individual power stages are explained, existing controversial definitions are clarified, and an evaluation guideline is applied to previously obtained data. Finally, the defined systematic analysis is applied to the results of a recently conducted plasma-actuator in-flight experiment.

Airflow influence on the discharge performance of dielectric barrier discharge plasma actuators

In the present work, the effect of the airflow on the performance of dielectric barrier discharge plasma-actuators is investigated experimentally. In order to analyze the actuator’s performance, luminosity measurements have been carried out simultaneously with the recording of the relevant electrical parameters. A performance drop of about 10% is observed for the entire measured parameter range at a flow speed of M = 0.145 (U∞=50 m/s). This insight is of particular importance, since the plasma-actuator control authority is already significantly reduced at this modest speed level. The results at higher Mach numbers (0.4<M<0.8) reveal an even more pronounced reduction of about 30%. From the combined analysis, the conclusion is drawn that the decreasing electrical performance PA correlates closely with the decreasing luminosity peak intensity G for increasing airflow velocities. Two non-dimensional scaling numbers are proposed to characterize and quantify the airflow influence. It is demonstrated that these...

Linear Stability Analysis for Manipulated Boundary-Layer Flows using Plasma Actuators

This paper presents the implementation of a method for linear stability analysis (LSA) and its application to investigate transitional boundary-layer flows affected by dielectric-barrier discharge (DBD) actuators. These flow-control devices are used to influence the process of boundary-layer transition by electrohydrodynamic coupling of momentum to the surrounding fluid molecules. The boundarylayer profile and its stability characteristics are changed. Linear stability analysis is applied to numerical and experimental data and helps to understand the effective mechanisms of these flow-control actuators when applied for transition control. Amplification rates in the linear growth stage are diminished and the critical as well as the local Reynolds number are affected by DBD actuation, leading to considerable delay of transition.

Common-base proper orthogonal decomposition as a means of quantitative data comparison

The method of common-base proper orthogonal decomposition (CPOD) is introduced as a tool for processing data—numerical simulations or experiments—acquired over a selection of operating parameters, for the purpose of quantitative comparison and/or optimization. In the present work, a review of the standard proper orthogonal decomposition (POD) is presented to explain the need and the nomenclature of the new approach. In order to illustrate the capabilities of CPOD, both POD and CPOD are applied to spatial velocity fields obtained experimentally from immediately above dielectric barrier discharge plasma actuators operated in quiescent air.

Scaling of maximum velocity, body force, and power consumption of dielectric barrier discharge plasma actuators via particle image velocimetry

This study presents Particle Image Velocimetry (PIV) measurements of the induced flow characteristics generated by single dielectric barrier discharge (DBD) actuators in quiescent conditions. The primary aim is to establish accurate empirical trends for model development on both the maximum induced velocity and body force with voltage and consumed power. The results reveal a power law variation for the maximum velocity at low voltages which is followed by an asymptotic behavior. In contrast, the body force is characterized by two power law regions. The power law exponent is shown to be a function of the dielectric thickness, frequency and dielectric constant. Reducing the former or increasing the latter two result in a higher coefficient and lower voltage at which the trend changes. The onset of the second region occurs at a Re ∼ 100 (based on the maximum velocity, um, and corresponding half height, y1/2) and is characterized by a velocity profile which no longer agrees with the laminar profile of Glauert...

Online-characterization of dielectric barrier discharge plasma actuators for optimized efficiency of aerodynamical flow control applications

The impact of fluctuating and transient kinematic and thermodynamic airflow conditions on the performance of dielectric barrier discharge (DBD) plasma actuators is demonstrated. A novel online-characterization and control approach is introduced, revealing the possibility of compensating for impaired discharge performance due to changing airflow scenarios during actuator operation. The goal of controlling the plasma actuator performance online and in situ is achieved and successfully demonstrated.

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.