Effect of dielectric barrier discharge plasma actuators on vortical structures in a mixing layer

Abstract

The influence of spanwise-uniform electro-fluid-dynamic forcing applied by a dielectric barrier discharge (DBD) plasma actuator on the growth of a plane mixing layer and the dynamics of large-scale spanwise vortices are investigated experimentally. A two-dimensional mixing layer formed between two streams of air with different velocities is employed for this study. Quantitative spatio-temporal measurement of the flow field is acquired using high-speed planar particle image velocimetry. The DBD actuator was constructed such that it imparts perturbations into the splitter-plate boundary layer formed by the high-velocity fluid stream, close to the trailing edge. Through this, the fundamental Kelvin–Helmholtz instability of the current mixing layer and its first sub-harmonic are forced. Forcing the fundamental instability results in the inhibition of vortex pairing due to the attenuation of sub-harmonic instabilities, and thus, mixing layer growth is halted in the vicinity of the trailing edge. With sub-harmonic instability forcing, neighboring vortices interact with each other and amalgamate together through mutual induction. This results in a higher growth rate compared to the unforced mixing layer at the streamwise location of this vortex interaction. Eventually, the growth rate of the forced mixing layers becomes similar to that of the unforced case. These results demonstrate the influence of the applied forcing on the spectral signature, growth, and stability characteristics of the plane mixing layer and the dynamics of the coherent vortical structures.

Spatial and temporal dynamics of a supersonic mixing layer with a blunt base

“…Centroids are reconstructed using the POD method's reverse process, as described in Eq. (32). Each centroid has two components in this study: streamwise velocity and transverse velocity.…”

“…23 The engineering development of combined cycle engines has reignited the research interest in the fundamental studies [24][25][26][27] and mixing enhancement techniques 28,29 in the supersonic mixing layer. However, the splitter plate with a relatively thin trailing edge is generally included in the experiments [30][31][32] for the study convenience, especially in the supersonic regimes since the flow structures are pure at this moment. The velocity inlet in simulations is assigned as a tanh-type profile without taking into account a splitter plate.…”

Identification of flow structures in a closed chamber in the presence of a needle plasma actuator

“…12 NTPs are produced through a variety of electrical plasma discharges, for example, radio frequency discharge, direct current glow discharge (DCGD), corona discharge, microwave discharge, atmospheric pressure discharge, surface discharge, pulsed corona discharge, and dielectric barrier discharge (DBD). [12][13][14] DBD plasma actuators have gained much attention due to their wide effectiveness to control the ignition and combustion characteristics, 9 flow structures in a mixing layer, 14 boundary layer control from transition to turbulence, 13,15 flow separation control, [16][17][18] and landing gear noise reduction. 19 In comparison with other flow control techniques, DBD plasma actuators have lower power consumption; are easy to handle; no movement of mechanical parts; lightweight; inexpensive to build, implement, and maintain; and have high-frequency response permitting real-time operating parameters.…”

“…Previously, several experimental demonstrations have been carried out on the effective control of flow dynamics using different DBD plasma actuator configurations 14,16,[24][25][26][27] and actuation types. 28,29 Adding to this, Bernard et al 4,5 performed an experimental study to analyze the impacts of AC-DBDPA on turbulent air jets by using an high voltage (HV) sinusoidal generator with or without pulsation mode.…”