Numerical Study on Transverse Jet Mixing Enhanced by High Frequency Energy Deposition

The mixing mechanism of a transverse jet enhanced by high-frequency plasma energy deposition is investigated at Ma = 6.13 using both experimental measurements and improved delayed detached eddy simulation. The test configuration is a flat plate with argon gas injected vertically at its center. The plasma actuator driven by 20 and 50 kHz pulsed discharge is used as a mixing enhancement device, which is located upstream of the jet. The schlieren and planar laser scattering visualization show that the interaction between the hot bubbles induced by the plasma energy deposition and the bow shock caused by the jet generates large scale vortices that diffuse the jet components, and improve the penetration depth of the jet. These large-scale vortices augment the vorticity and turbulence intensity, thus enhancing the jet component mixing. The vortex analysis indicated that the jet vorticity increases due to the stronger baroclinic torque induced by Richtmyer–Meshkov (R–M) instability around the bubble/shock interaction region, which promotes the turbulent kinetic energy and the production of the large-scale vortex structures. The baroclinic torque and the resulting large-scale vortices are the physical origin of the enhanced mixing of the transverse jet.

Mechanism of a transverse jet mixing enhanced by high-frequency plasma energy deposition

Wang,

Yang,

et al. 2023

Experimental study on control of transverse jet mixing by arrayed plasma energy deposition

Chao,

Gao,

Wang

et al. 2024

The efficient and prompt mixing of fuel is crucial in the operation of scramjet engines. This paper presents the findings from wind tunnel experiments that examined the influence of plasma energy deposition on transverse jets at a Mach number of 6.13. The study took into account various inlet flow total pressures and momentum flux ratios between the jet and the main flow. Utilizing a database containing time-resolved intensities from instantaneous schlieren images, we perform turbulence analysis employing various techniques such as the root mean square, fast Fourier transform, proper orthogonal decomposition, and the two-point correlation method. Specifically, we aim to compare and analyze the pulsation characteristics and spatial self-organization of the jet flow field, both with and without energy deposition control. The findings reveal that intermittent “hot bubbles” created by plasma energy deposition interact with the bow shock induced by the jet, resulting in the formation of an array of large-scale vortices. These vortices emerge as the dominant structures within the jet, effectively amplifying its pulsations. At low inlet flow pressures, energy deposition primarily disrupts the jet, causing large-scale vortices to propagate primarily within the jet plume region. However, at high inlet flow pressures, the impact of energy deposition extends to both the jet and the turbulent boundary layer, encompassing their respective disturbance ranges. Increasing the inlet flow pressure constraints the evolution of large-scale vortices, thus limiting the efficacy of energy deposition in governing the mixing process.

Experimental study of arc plasma energy deposition flow control on supersonic cavity combustor

Wang,

Chen,

Feng

et al. 2024

This investigation conducted an experimental study of flow control in a Mach 2.5 cavity combustor using arc plasma energy deposition (APED), implemented both with and without injection. APED was produced by a pulsed arc discharge plasma actuator at frequencies of 5, 10, 15, and 20 kHz. The objective is to elucidate the influence and underlying mechanisms of APED on the flow dynamics by statistically evaluating time-resolved schlieren images and monitoring pressure fluctuations throughout the control process. The findings indicate that APED significantly modifies the energy distribution across unsteady modes and alters the pressure distribution within the flow field. In scenarios without injection, high-frequency discharge triggers oscillations in the shear layer; the impact of precursor shocks and thermal bubbles diminishes the magnitude and fluctuations of both shear layer-induced and internal shocks. Conversely, in the injection scenario, high-frequency discharge, in conjunction with oscillations of the boundary layer and bow shocks, amplifies the oscillation amplitude and frequency of jet vortex shedding. Additionally, APED intensifies the pulsation and penetration depth of the jet, which is essential for enhancing the mixing efficiency of the incoming flow with fuel. The effectiveness of the control is positively correlated with the actuator's discharge frequency, or its average power, within the confines of this study.