Jianguo Zheng

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

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.

Study of Shock and Induced Flow Dynamics by Nanosecond Dielectric-Barrier-Discharge Plasma Actuators

The shock wave behavior generated from a single shot of pulsed nanosecond dielectric-barrier-discharge plasma actuator with varying pulse voltages in quiescent air was studied by experiments and numerical simulations. The experiments included using the schlieren technique, a fast response pressure transducer, and a two-velocity-component particle image velocimetry system to measure the propagation of the shock wave, the shock overpressure, and the shock induced flow, respectively. For the numerical simulation, a simple “phenomenological approach” was employed by modeling the plasma region over the encapsulated electrode as a jump-heated and pressurized gas layer. The present investigation revealed that the behaviors of the shock wave generated by the nanosecond pulsed plasma were fundamentally a microblast wave, and their speed and strength were found to increase with higher input voltages. The blast wave occured about 1 to 3u2009u2009μs after the discharge of the nanosecond pulse, which was dependent on the inpu...

Study of shock and induced flow dynamics by pulsed nanosecond DBD plasma actuators

The shock wave behaviour generated from a single shot of nanosecond DBD plasma actuator with varying pulse voltages in quiescent air was studied by experiments and numerical simulations. The experiments includes Schlieren technique, a fast response pressure transducer and a two-velocity-component PIV system to measure the propagation of the shockwave, the shock overpressure and the shock induced flow, respectively. For the numerical simulation, a simple “phenomenological approach” is employed by modelling the plasma region over the covered electrode as a jump-heated and pressurized gas layer. The present investigation reveals that the behaviours of the shock wave generated by the nanosecond pulsed plasma is fundamentally a micro blast wave and its speed and strength is found to be increased with higher input voltages. The blast wave occurs in about 1 to 4 μs after the discharge of the nanosecond pulse, which is dependent on the input voltages, and decays quickly from supersonic to sonic level within about 5μs (2-3mm from the actuator surface). The shock induced burst perturbations (overpressure and induced velocity) is found to be restricted to a very narrow region (about 1mm) behind the shock front and last only for a few microseconds. While a fairly weak induced vortex flow is observed in a relative long time period after the discharge of the plasma. These results imply that the pulsed plasma actuators have stronger local effects in time and spatial domain.

A note on supersonic flow control with nanosecond plasma actuator

A concept study on supersonic flow control using nanosecond pulsed plasma actuator is conducted by means of numerical simulation. The nanosecond plasma discharge is characterized by the generation of a micro-shock wave in ambient air and a residual heat in the discharge volume arising from the rapid heating of near-surface gas by the quick discharge. The residual heat has been found to be essential for the flow separation control over aerodynamic bodies like airfoil and backward-facing step. In this study, novel experiment is designed to utilize the other flow feature from discharge, i.e., instant shock wave, to control supersonic flow through shock-shock interaction. Both bow shock in front of a blunt body and attached shock anchored at the tip of supersonic projectile are manipulated via the discharged-induced shock wave in an appropriate manner. It is observed that drag on the blunt body is reduced appreciably. Meanwhile, a lateral force on sharp-edged projectile is produced, which can steer the body a...

Flow Separation Control Over a Ramp with Nanosecond-Pulsed Plasma Actuators

Recently, much attention has been devoted to the nanosecond pulsed dielectric barrier discharge (ns-DBD) plasma actuators as they demonstrated superior control feature at higher speed regimes as compared to the alternating current (AC) DBD actuators. This type of actuator usually has similar configurations as the AC-DBD device, but is driven by high-voltage repetitive pulses with voltage of up to 50kVs and rise time from a few to tens of nanoseconds. It has been generally agreed that the main control mechanism of the ns-DBD plasma actuator is through Joule heating, causing steep gradients in pressure and temperature inside the heated gas volume. As a result, moving shock waves are generated and interact with the external flow. While previous studies have focused on the effectiveness of the actuators on specific applications, how the generated shock waves influence and interact with the external flow has not been thoroughly investigated. Therefore, this paper is to address this issue through studying the suppression of the separated flow over a ramp with nanosecond pulsed plasma actuators in a wind tunnel using smoke-wire visualization, Schlieren imaging technique and particle imaging velocimetry (PIV).