Control of Dynamic Stall of an Airfoil by Using Synthetic Jet Technology
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RESEARCH ARTICLE-MECHANICAL ENGINEERING
Control of Dynamic Stall of an Airfoil by Using Synthetic Jet Technology Jianjun Feng1 · Guojun Zhu1 · Yuan Lin1 · Yunzhe Li2 · Guangkuan Wu1 · Jinling Lu1 Received: 19 April 2020 / Accepted: 17 September 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract In this paper, the dynamic stall characteristics of the S809 airfoil have been numerically predicted, and the flow under dynamic stall condition has been controlled by introducing synthetic jet for enhancing the airfoil aerodynamic performance. In addition, experimental results have been adopted to validate the obtained numerical ones. The results show that the oscillation of the airfoil can delay the occurring of stall, and the stall angle of attack is increased from 9.5° to 13.1°. The introduction of synthetic jet can improve the lift coefficient of airfoil under dynamic stall conditions: The mean lift coefficient in a period of oscillation has been increased by 33%, and the drag coefficient has been reduced by 39%. Moreover, the stall angle of attack is increased from 13.1° to 16.2°. Therefore, the airfoil performance under dynamic stall condition could be greatly improved by the introduction of synthetic jet technology. Keywords S809 Airfoil · Dynamic stall · Synthetic jet · Flow control · Characteristic
List of Symbols α α mean α amp c CL CD FL f1
B B
Angle of attack Mean value of angle of attack Fluctuating amplitude of angle of attack Chord length of the airfoil Lift coefficient Drag coefficient Lift force of the airfoil Frequency of the airfoil oscillation
Jianjun Feng [email protected]
f2 FD Re SJ t T1 T2 U∞ V jet y+ ρ θ
Frequency of the synthetic jet Drag force of the airfoil Reynolds number Synthetic jet Time Period of the angle of attack Period of the synthetic jet, 1/f 2 Incoming flow velocity Velocity of the synthetic jet Dimensionless wall distance Air density Angle of the synthetic jet
Guojun Zhu [email protected] Yuan Lin [email protected] Yunzhe Li [email protected] Guangkuan Wu [email protected] Jinling Lu [email protected]
1
State Key Laboratory of Eco-Hydraulics in Northwest Arid Region of China, Xi’an University of Technology, Xi’an 710048, China
2
Fine Institute of Hydraulic Machinery, Zhejiang Fuchunjiang Hydropower Equipment Co., LTD., Hangzhou 311121, China
1 Introduction For an airfoil, the lift-to-drag ratio increases gradually with angle of attack. However, when the angle of attack reaches a certain critical value, the reverse pressure gradient occurring will inevitably drive the flow separate from the airfoil surface, reducing the lift and increasing the drag. When the lift-to-drag ratio starts to decline due to the increasing extent of flow separation, the stall phenomenon happens [1]. The flow control technology is to intervene the flow by applying external forces or injection quality to the fluid, in order to improve the flow behavior and consequently to increase
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Arabian Journal for Science and Engineering Fig. 1 Computational model a
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