Effect of novel synthetic jet on wake vortex shedding modes of a circular cylinder |
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| Authors: | Li Hao Feng Jin Jun Wang Chong Pan |
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| Institution: | 1. Dept. of Industrial Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy;2. AWEP Dept., Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands;1. School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China;2. Department of Aerospace Engineering, Iowa State University, Ames, IA 50011, USA;3. School of Civil and Environment Engineering, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518055, China;4. School of Civil and Hydraulic Engineering, Dalian University of Technology 116024, China;1. School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore 639798, Republic of Singapore;2. Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China;3. Singapore Institute of Technology, Singapore 179104, Republic of Singapore;1. School of Energy and Power Engineering, Xi''an Jiaotong University, 710049 Xi''an, People''s Republic of China;2. Faculty of Engineering and Physical Sciences, University of Southampton, SO17 1BJ Southampton, United Kingdom |
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| Abstract: | A novel actuator signal achieved by changing the ratio of the suction duty cycle to the blowing duty cycle is adopted to enhance the control effect of the synthetic jet for the flow around a circular cylinder. The suction duty cycle factor k defined as the ratio between the time duration of the suction cycle and the blowing cycle and the equivalent momentum coefficient Cμ are introduced as the determining parameters. The synthetic jet is positioned at the rear stagnation point in order to introduce symmetric perturbations upon the flow field. The proper orthogonal decomposition (POD) technique is applied for the analysis of the spanwise vorticity field. Increasing the suction duty cycle factor, the momentum coefficient is enhanced, and thus a stronger and larger scale synthetic jet vortex pair with a higher convection velocity is generated. The synthetic jet vortex pair interacts with the spanwise vorticity shear layers behind both sides of the cylinder, resulting in the variations of the wake vortex shedding modes at Re=950: for k=0.25, Cμ=0.148, vortex synchronization at the subharmonic excitation frequency with antisymmetric shedding mode; for 0.50≤k≤1.00, 0.213≤Cμ≤0.378, vortex synchronization at the excitation frequency with the symmetric or antisymmetric shedding modes; for 2.00≤k≤4.00, 0.850≤Cμ≤2.362, vortex synchronization at the excitation frequency with symmetric shedding mode. Hence, the control effect of the synthetic jet upon the wake vortex of a circular cylinder can be enhanced by increasing the suction duty cycle factor so as to increase the momentum coefficient. This is also validated at a higher Reynolds number Re=1600. |
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