Control of backward-facing step flow using DBD plasma actuator (Effect of frequency and duty ratio of burst modulation)

Kikuchi, Satoshi; Kozato, Yasuaki; Lee, Keunseob; Imao, Shigeki

doi:10.1299/transjsme.18-00247

Cited by 3 publications

(1 citation statement)

References 15 publications

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“…Furthermore, the PA is beginning to be widely applied in uses other than the suppression of flow separation. In the backward-facing step flow, the burst mode, in which the PA operates intermittently at a certain frequency, promotes the collapse of the periodically shed vortex present in the separated shear layer, and it increases the distance of the reattachment point from the step (Kikuchi et al, 2018).…”

Section: Aerodynamic Drag Reduction Of a Simplified Vehicle Model By mentioning

confidence: 99%

Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator

Shimizu

Nakashima

Sekimoto

et al. 2019

Mechanical Engineering Letters

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In recent years, the dielectric barrier discharge plasma actuator (DBD-PA), which is a fluid control device, has been investigated for achieving both high aerodynamic performance and pleasing styling of transportation equipment. In this study, the authors installed a DBD-PA system on a simplified three-dimensional bluff automobile body to reduce the aerodynamic drag. In particular, the authors focused on the sides of the rear end of the body, where the local shape has high sensitivity regarding both styling and aerodynamic drag. At the rear sides of the automobile-like bluff body, a sharp edge rather than a smooth rounded corner often reduces the aerodynamic drag by promoting airflow separation. Therefore, the authors aimed to reduce the aerodynamic drag by using a DBD-PA system to promote flow separation at the rear end while retaining its rounded shape. Aerodynamic measurements using a one-fifth scale simplified automobile model were conducted in a wind tunnel. Preliminary investigation of the aerodynamic effect at the rear clarified how the longitudinal vortices from the rear pillar and the side edge of the trunk deck cause the drag increase at the rear-end corners. Two parallel DBD-PAs were installed on the rear surface to shift these vortices away from the corners by promoting flow separation. The drag reduction rate reached 3% at the highest applied voltage using the DBD-PA system on a rounded shape, and it achieved approximately half the effect of the sharp-edged shape. The longitudinal vortices were successfully kept away from the rear-end corners by the DBD-PAs. The surface pressure increased with the displacement of the vortices, which led to the drag reduction observed.

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Section: Aerodynamic Drag Reduction Of a Simplified Vehicle Model By mentioning

confidence: 99%

Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator

Shimizu

Nakashima

Sekimoto

et al. 2019

Mechanical Engineering Letters

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

et al. 2022

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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 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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Control of backward-facing step flow using DBD plasma actuator (Effect of frequency and duty ratio of burst modulation)

Cited by 3 publications

References 15 publications

Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator

Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator

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

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

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