Surface velocity model of the flow caused by a DBD plasma actuator

The control mechanism of a dielectric barrier discharge plasma actuator is investigated via direct numerical simulations in the flow field around a square cylinder. The Reynolds number is 33000. Conditions for the burst frequency of the actuator are explored in terms of the reduction rate of drag and root mean square (RMS) lift coefficients. A good control effect is achieved, and vortex shedding is fairy repressed at Stb (Strouhal number for the burst frequency) = 0.50. The flow induced by the actuator generates two vortices: the first and second vortices. Until the next actuator on-time, the second vortex grows on the upper or lower side of the cylinder. The second vortex collides with the first vortex, and both vortices flow downstream in a straight line. This situation happens almost simultaneously on the upper and lower sides of the cylinder; thus, a high reduction rate of RMS lift and drag coefficients can be obtained. A control effect is obtained at Stb = 2.00, which is lower than that at Stb = 0.50, where a tiny vortex is raised by the flow induced by the small actuator on-time and flows downstream at a small distance away from the cylinder. The least control effect is achieved at Stb = 0.25 because the collision between the first and second vortices does not occur due to a large actuator off-time. The duration of on-time and off-time is important for determining the burst frequency for the most effective control.

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Numerical simulation of flow control around a rectangular cylinder by dielectric barrier discharge plasma actuators

Lee

Kozato

Kikuchi

et al. 2022

Physics of Fluids

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Flow control by dielectric barrier discharge plasma actuators for a rectangular jet with inlet disturbance

Lee,

Kikuchi

2024

Physics of Fluids

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Direct numerical simulations were performed to examine the control mechanism of a plasma actuator using a dielectric barrier discharge in a rectangular jet with an inlet disturbance. The nozzle has a ratio of 75–10 mm, while the Reynolds number is 3300, and the peak frequency near the nozzle exit is 55 Hz. The jet is controlled by the actuators with conditions of 55 Hz burst frequency, 10% duty ratio, and π phase difference between the upper and lower actuators. The flow field spreads downstream more than that without control. Moreover, the controlling mechanism generates a vortex by inducing flow from the actuator, which grows in size by merging with other vortices generated upstream. Furthermore, the induced flows generate vortices on the upper and lower shear layers that grow in opposite phases of π, and these vortices cause upward and downward flow, respectively, thereby accelerating the spread of the jet. The vortex generated by the induced flow can grow due to its low-streamwise velocity. This occurs regardless of the inlet disturbance because the streakline from the induced flow moves downward near the nozzle surface, causing a rapid decrease in the streamwise velocity after the actuator is stopped. Thus, the actuator's control effect can be explained by the momentary change in the location of the streaklines around it.

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Numerical simulation for control effect of backward-facing step flow by a plasma actuator with burst modulation

Lee

Kikuchi

Imao

2020

Transactions of the JSME (In Japanese)

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The backward-facing step channel flow in which the Reynolds number is 1080 is calculated to investigate the control effect by a DBD plasma actuator which is activated with continuous drive or burst modulation. The plasma actuator is located on the edge of the backward-facing step. The conditions for the actuator are 3, 5, 8, and 10 m/s of the surface velocity and 50, 100, 150, and 200 Hz of the burst frequency. When the actuator is activated with the continuous drive, the more the reattachment point moves upstream, the more the induced flow by the actuator is strong. When the burst modulation for the actuator is used, the smaller burst frequency makes the reattachment point move further upstream generally. The reattachment point could travel upstream if a huge vortex has a negative vorticity is generated by merging two vortices near the step. This is because that the huge vortex flows downward with the mainstream flow, on the other hands, if this combining two vortices is not appeared, the reattachment point is little changed. In addition, the mechanism for moving upstream for the reattachment point by the actuator is different for using the continuous drive or the burst modulation. In the continuous drive, the strong enough induced flow by the actuator becomes unstable near the step and flows downward with the mainstream flow, but in the burst modulation, the merged vortex from the mainstream flow appears near the step because a certain period by the burst modulation is introduced in the mainstream flow.

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Surface velocity model of the flow caused by a DBD plasma actuator

Cited by 3 publications

References 17 publications

Numerical simulation of flow control around a rectangular cylinder by dielectric barrier discharge plasma actuators

Numerical simulation of flow control around a rectangular cylinder by dielectric barrier discharge plasma actuators

Flow control by dielectric barrier discharge plasma actuators for a rectangular jet with inlet disturbance

Numerical simulation for control effect of backward-facing step flow by a plasma actuator with burst modulation

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