Newsletter  2020.2  Index

Theme : "The Conference of Fluid Engineering Division (February issue)” Preface T. HASHIMOTO，S. MATSUDA，H.J. PARK Moving-boundary problems in rarefied gas dynamics Tetsuro TSUJI (Kyoto University) Flow Control of Jets and Separated Flows Toshihiko SHAKOUCHI (Mie University) Machine-learned three-dimensional super-resolution analysis of turbulent channel flow Kai FUKAMI, Koji FUKAGATA (Keio University), and Kunihiko TAIRA (UCLA) Flow control around an oscillating square cylinder by using plasma actuators Chihiro ONAHA (Toyohashi University of Technology) Dream to Sounds Takumi FUKUSHIMA (Tokyo University of science)

 

Flow control around an oscillating square cylinder by using plasma actuators

Chihiro ONAHA, Toyohashi University of Technology

Abstract

The final goal of this study is to control the flow field around the collector head of pantograph for Shinkansen using PA and to investigate the possibility of industrial use of PA for the flow control. In the current study, as a first step, we tried to control the flow field around the oscillating square cylinder and examined the effects of the electrode shape and arrangement on the flow field. The flow field around the stationary cylinder control was visualized by the smoke-wire method. Then, the optimal electrode arrangement for the stationary cylinder was applied to an oscillating cylinder, and the effects of PA on the flow separation were evaluated by flow visualization and measurements with a hot-wire anemometer. Fig. 1 shows a schematic diagram of the electrode shape of PA, and Table 1 shows a specification of the electrode arrangement of PA.

The flow pattern around the stationary square cylinder with different PA shapes is shown in Fig. 2. The boundary layer separation around the stationary cylinder was suppressed depends on the electrode shape. In this setup, the opposite arrangement of PA introduced vertical vortices into the separated boundary layer and had the biggest suppression effect, which reduces the thickness of the separated boundary layer up to 37%. Fig. 3 and 4 show that the thickness of the separating boundary layer around the oscillating cylinder was reduced by the PA. Fig. 5 shows that the vortex shedding frequency associated with the oscillation can be halved and the velocity fluctuation intensity can be suppressed by 24%.

Key words

Plasma actuators, square cylinder, oscillating, Flow visualization

Figures

Table 1 Specification of electrode arrangement of PA .

PA type	Distance of characteristic length[mm]
(a) Straight	d	3, 5
(b) Intermittent	s	4, 6, 8
(c) Opposite	p	3, 5, 7, 9

Fig. 1 Schematics of PA electrode shape and arrangement of PA

Fig. 2 Flow pattern around the stationary square cylinder with different PA shapes.

Fig. 3 Flow pattern around the oscillating square cylinder.

Fig. 4 Velocity distribution in the wake of the square cylinder with and without PA control.

Fig. 5 Spectra of velocity fluctuations at the wake of the square cylinder.