Numerical simulation of nanosecond pulsed dielectric barrier discharge actuator in a quiescent flow

Abstract

We present a numerical study of nanosecond pulsed dielectric barrier discharge (DBD) actuator operating in quiescent air at atmospheric condition. Our study concentrates on plasma discharge induced fluid dynamics and on exploration of parametric space of interest for voltage pulse in an attempt to shed some light into elucidation of the mechanisms whereby the generated shock wave propagates through and affects the external flow. Specifically, a one-dimensional, self-similar, local ionization kinetic model recently developed to predict key parameters of nanosecond pulsed plasma discharge is coupled with the compressible Navier-Stokes equations possibly for the first time. Within the considered range of parameters of the plasma model which is justified for the modeling of surface nanosecond pulsed discharge at atmospheric pressure, our coupled method is able to provide satisfactory prediction of the shock structure generated by the actuator for comparison with experiment, not only in the qualitative shock wave shape but also in quantitative shock front displacement. We provide a comprehensive analysis of the gas heating, shock wave initiation and evolution processes. For example, the characteristic time of the rapid localized heating responsible for shock wave generation, which is yet to be quantified experimentally, is found to be ∼350 ns. We conduct a parametric investigation by varying the peak voltage from 10 kV to 50 kV and rise time from 5 ns to 150 ns. The pressure wave whose behavior is found to be dominated by input voltage amplitude, introduces highly transient, localized disturbance to the quiescent air. In addition, the vortex induced by the shock passage is relatively weak. The interplay of the induced flows by a few successive plasma discharges operating at continuous mode does not appear to be significant, especially at low voltage amplitude.

Numerical Study of Control of Flow Separation Over a Ramp With Nanosecond Plasma Actuator

“…Therefore, the shock seems to have no lasting effect on the flow and contribute little to flow control. This is consistent with conclusion reached for the discharge in quiescent air 7 . To examine the impact of residual heat on the flow, the temperature contour images at two times are illustrated in Fig.…”

“…Obviously, a through characterization study of nanosecond plasma discharge is desired. The authors have conducted both numerical and experimental investigation into the fluid dynamics arising from the plasma discharge in quiescent air [7][8] . It is found that the generated shock wave can induce highly transient and localized perturbation in fluid properties, whose intensity depends mainly on the pulse voltage.…”

Energy deposition characteristics of nanosecond dielectric barrier discharge plasma actuators: Influence of dielectric material

“…However, recent investigations gave numerical and experimental evidences that the flow control authority shown by ns-DBD plasma actuator does not purely rely on the formation of the shockwave. Rather, the effect can be due to a combination of pressure, viscosity, and density gradients produced by the residual heat deposited within the discharge volume by the discharge 9,10,14 (same conclusion was reported 13 and later acknowledged 29 by others). In recent work by the authors, 9,10 evidence was given of the existence of a strong thermal effect due to nanosecond plasma actuation using Schlieren imaging.…”

“…7,8,11,12 Using pulse widths of several microseconds, Benard et al 12 were able to demonstrate that, in fact, the compression wave is a superposition of two individual waves emanating from both the rising and falling portions of the high voltage pulse. Zheng et al 13 have reproduced numerically the experiments of Benard et al 12 investigating parameters, such as voltage amplitude, rising time, and pulse length of a shockwave. They concluded that a disturbance induced by those compression waves was unable to justify the control authority shown by ns-DBD, as verified by Popov and Hulshoff.…”

“…It has been observed that each single pulse contributes to the formation of this "hotspot," and after the end of the discharge, thermal expansion takes place. 10,13 An estimate of the heated region is obtained via an inhouse image-processing algorithm, developed with Matlab, which isolates the region of interest in the image (where density gradient is located) based on a threshold criterion. Such threshold is set based on the average shade of grey of the image background, thus it is able to set a specific threshold accordingly to the light intensity of the image itself.…”