Ryan Durscher

Three-dimensional flow measurements induced from serpentine plasma actuators in quiescent air

This paper presents three-dimensional flow measurements performed on a dielectric barrier discharge (DBD) actuator with the electrodes in a serpentine design. Such a configuration induces a local pinching and a local spreading of the fluid as one follows along the span of the actuator. In this work two different variations on the serpentine configuration are evaluated: one constructed from patterned circular arcs and one from patterned rectangles. The influence of applied voltage is studied for the former case. To quantify these effects stereo particle image velocimetry (PIV) is used to generate time averaged, spatially resolved measurements of the detailed flow structure. The three components of the velocity vector are measured along spanwise and streamwise cuts. These slices are then reconstructed to provide a three-dimensional view of the induced flow field. The results for the induced flow fields are also compared with stereo-PIV measurements made on a standard linear DBD actuator. A truly three-dimensional induced flow field was observed as a result of the serpentine configuration. These designs could be beneficial for rapid mixing of the local fluid.

Three-dimensional effects of curved plasma actuators in quiescent air

This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength (λ) and amplitude (Λ) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators p...

Flow and force inducement using micron size dielectric barrier discharge actuators

Micron size dielectric barrier discharge actuators, designed for minimal footprint area and weight penalty, show a wall jet up to 2.0 m/s consuming 15 W/m of electrode. A torsional balance measures force up to 3 mN/m of electrode and demonstrates equivalent “thrust effectiveness” (induced force/power) to macroscale actuators. Compared with reported macroscale data, the microscale actuator shows a 31% increase in energy conversion efficiency. Per unit actuator mass, both the force and the velocity induced by microscale actuators show an order of magnitude (22.1 and 18.5 times, respectively) increase over macroscale actuators, making them suitable for distributed flow control applications.

Novel Multi-Barrier Plasma Actuators for Increased Thrust

This paper presents experimental measurements performed on multi-barrier plasma actuators (MBPA). The typical dielectric barrier discharge (DBD) plasma actuator consists of two electrodes separated by a dielectric layer. The surrounding air locally ionizes when a radio frequency (RF), high voltage waveform is applied to one of the electrodes. This results in an electrohydrodynamic (EHD) body force on the fluid. MBPAs extend upon the typical configuration of the DBD to incorporate multiple layers of dielectric materials and powered electrodes. This work explores different actuator designs which, through direct force balance measurements, demonstrate that the MBPA configuration effectively increases the EHD body force produced by a plasma actuator. The power consumption of these devices is analyzed and compared with typical actuator configurations. Results show significant increase in thrust over power ratio represented by actuator effectiveness.

Aerogel and ferroelectric dielectric materials for plasma actuators

This paper presents performance evaluation of two thick materials with extreme permittivity as dielectric barrier discharge actuators. Specifically, the use of silica aerogels and ferroelectrics is investigated. Due to high polarizability of the ferroelectric material the supplied power manifests itself primarily as heat generation with no measurable thrust. The silica aerogel, however, has a significant impact on thrust saturation as compared with other dielectrics reported to date. Specifically, the silica aerogel is found to have an order of magnitude better thrust to actuator weight ratio than acrylic and twice than that of Kapton with no power penalty, making it potentially useful for small vehicle applications.

Characterization and manipulation of the “saturation” effect by changing the surface temperature of a dielectric barrier discharge actuator

The thrust produced by a sinusoidally driven dielectric barrier discharge actuator in quiescent air is known to increase with a power law of the applied voltage. For voltages greater than a threshold, the exponent of the power law reduces limiting the thrust increase and the actuator is said to have “saturated,” limiting the actuators usefulness. The onset of saturation is visually correlated by the inception of filamentary discharge events. In this letter, the flow transition to the saturation condition is characterized. Furthermore, the saturation effect can be manipulated by changing the local surface temperature of the dielectric.

Force Measurement Techniques and Preliminary Results Using Aerogels and Ferroelectrics for Dielectric Barrier Discharge Actuators

This paper presents experiments carried out on dielectric barrier discharge plasma actuators. Two areas concerning these actuators are addressed in this work: First, two different experimental techniques used to measure the induced body force are compared. A high precision force balance is used to make a direct measurement of the thrust produced which is then compared with a control volume analysis on data obtained through particle image velocimetry. For the direct measurements the effect of varying the actuator plate length upon which the induced flow acts is also investigated. The results from these tests show that the length of the actuator plate is most influential at higher voltages with the measured force increasing as much as 20% as the length of the plate is decreased. When the two methods are compared against each other, good agreement is found given that the control volume size has a sufficient downstream extent. In the second part of the paper, materials with extreme relative dielectric constants () are investigated for performance. Specifically, the use of silica aerogels ( ~ 1.1) and ferroelectric dielectrics ( = 1750) are examined. The silica aerogel was found to have a strong effect on thrust generation as compared to the other dielectrics tested. However, the power supplied to the ferroelectric actuator manifests itself primarily as heat generation with no noticeable thrust measured. Especially due to its minimal actuator weight penalty and higher thrust, actuators made with silica aerogel may be quite useful for practical applications.

Microscale Dielectric Barrier Discharge Plasma Actuators: Performance Characterization and Numerical Comparison

Dielectric barrier discharge (DBD) plasma devices have been designed and manufactured with microscale dimensions utilizing semiconductor fabrication techniques. Particle image velocimetry (PIV) measurements indicate induced wall jet velocities up to 2.0 m/s. Direct force measurements using a torsional balance indicate thrust values up to 3 mN/m at 5 kVpp and 1 kHz and consume an average power of 15 W/m. The measured thrust data is applied in a numerical model to compare simulated velocity flow fields with experimental PIV data. The model shows good agreement with experimental data for the velocity and wall jet thickness for macro device geometries, but inaccurately predicts the downstream velocity decay. Microscale devices demonstrated equivalent ‘thrust effectiveness’ to macroscale actuators, but with a 31% improvement in mechanical-to-electrical energy conversion efficiency. The microscale DBD actuators occupy an order of magnitude reduction in device footprint and mass, and potentially enable large arrays for distributed flow control applications.

On Multi-Barrier Plasma Actuators

The multi-barrier plasma actuator (MBPA) is an extension on the standard dielectric barrier discharge (DBD) actuator which consists of conducting electrodes placed asymmetrically on a single dielectric substrate. The MBPA design incorporates multiple dielectric layers and phase lagged powered electrodes into the standard design in an effort to create a stronger discharge. The results of this increase could lead to higher induced velocities/resultant forces. In a prior study, the MBPA design was found to outperform the standard actuator in both measured force and effectiveness (ratio of the induced force over consumed power). The present investigation is an extension on this previous work to expound upon the broad design space of the multi-barrier configuration. The resultant force produced by both bi-layer and tri-layer actuators are measured directly using a precision force balance. The results of these experiments are then compared with the standard actuator design. In addition, the influence of mixing dielectric materials is also explored. For all test cases the total power delivered to the actuator is calculated and presented.

Induced Flow from Serpentine Plasma Actuators Acting in Quiescent Air

This paper presents experimental measurements performed on a dielectric barrier discharge (DBD) plasma actuator with the electrodes in a serpentine design. Such a configuration induces a local pinching or local spreading of the fluid as one follows along the span of the actuator. In this work the serpentine configuration is constructed from patterned circular arcs. The influence of applied voltage on the induced flow field is studied. To quantify these effects, stereo particle image velocimetry (PIV) is used to generate time averaged, spatially resolved measurements of the detailed flow structure. The three components of the velocity vector are measured along both spanwise and streamwise cuts. These slices are then reconstructed to provide a 3D view of the induced flow field. The results for the induced flow fields are also compared with 2D PIV measurements made on a standard linear DBD actuator.