INovative PLASma actuators for flow control – INOPLAS

The program INOPLAS is an experimental project with objectives toward the definition of innovative surface plasma discharges for flow control applications. Current actuators based on dielectric barrier discharge have demonstrated good control authority at low Reynolds numbers, but an improvement of these actuators is necessary for high speed flow control. The present project relates to the development of active actuators based on electrofluidodynamics conversion and then is an answer to the POS/DGA coordinated call.
The program proposes to explore different routes for enhancing the control authority of usual plasma actuators. Fundamental aspects of plasma physics will be investigated by a complete set of diagnostic including electrical measurements, plasma diagnostic and fluid mechanics measurements.

It is now recognized that the accumulation of charges at the dielectric wall is responsible for saturation in the electrohydrodynamic force produced by dielectric barrier discharge (DBD) actuators. The project proposes to explore the benefit of modifications of surface characteristics in order to mitigate saturation effects. This encompasses nanostructuration of the upper layer of the dielectric wall or the use of semi-conductive materials while the change in surface charge will be measured by non-contact measurements by electrostatic voltmeter and optical diagnostic such as CARS and Pockels. The program also concerns the improvement of nanosecond pulsed DBD, whose use actuators have demonstrated good results at high speed flow (>100 m/s). This actuator can produce pressure wave propagating at sound speed, each of the streamers in the plasma discharge being the support for production of an associated pressure wave. This project aims at precisely localizing the ionized channels and at extending these filaments by applying DC voltage on a third electrode.
Additionally, the program involves the development of novel actuators such as microplasmas based on DBD. By reducing the size of the actuator, strong charge density can be obtained this improving the rate of momentum transfer at the interface of plasma and dielectric wall. Arrangement in arrays will also be investigated, this increasing the scale of the actuator to enhance the surface of interaction between the neutral flow and the discharge. Plasma discharge in microscale gap can be useful for the definition of active plasma-assisted turbulent grid. This original device may help for jet flow control by amplification of the dissipative turbulent scales.
The program also involves developments on an hybrid plasma-assisted pulsed jet that can produce jet velocity larger than 100 m/s with depth modulation of its amplitude by using a volume plasma discharge.
Beyond limiting the investigation to the definition of actuators, plasma discharges can serve as flow sensor due to their high sensitivity to the environment of operation. The drift of the charged particles induced by ionization of the gas could be measured and my help in detecting flow separation.
Finally, the most promising actuators will be studied in situation of flow control with an application dedicated to modification of a separated shear layer (backward facing step configuration) at high speed flow (~90 m/s).

Finally, INOPLAS proposes a fully original approach and diagnostics for the development of innovative surface plasma discharges. This project involves the Institute PPRIME, in which the ElectroFluidoDynamics group occupies a role of strong international leadership in the development, analysis and use of plasma actuators for flow control.