Session: 08-06-01 Internal Flows & FIV

Paper Number: 102927

102927 - Dynamics of a Coupled Rigid-Flexible System in Wind Tunnel Experiments 

A novel flow control method, by adding a closed flexible filament to a rigid body, has been proven a significant drag reduction in the two-dimensional flow in a soap film (Phys. Rev. Lett., vol. 125(3), 2020, pp. 034502). In the present study, we extend this method to the three-dimensional rigid bluff body (a flat plate) flows through wind tunnel experiments. The Reynolds numbers based on the free-stream velocity (U) and the flat plate length (L) are 20000, 30000, and 40000. The length of the flexible membrane is in the range of 8/6L~4L. The aerodynamics characteristics of the coupled rigid-flexible system, flow structures behind the plate, and the shape deformation of the flexible membrane are presented. Benefiting from the closed flexible membrane, the coupled rigid-flexible system achieves a significant drag reduction in the three-dimensional flows. The maximum drag reduction of approximately 17% is observed under specific conditions. The flexible membrane self-adapts to a more streamlined shape and substantially changes the flow structures behind the plate, suggesting a strong correlation between deformation of the flexible membrane and the drag reduction. The effect of the length of the flexible membrane on the aerodynamics of the rigid-flexible coupling system is also discussed. The mean drag varies nonmonotonically to flexible membrane lengths. The preliminary results obtained in the present study may shed some light on the closed flexible membrane flow control method towards some real-life situations and potential applications.

Presenting Author: Yakun Zhao State Key Laboratory of Ocean Engineering

Presenting Author Biography: Yakun Zhao received her B.S. degree from South China University of Technology, Guangzhou, China in 2017, and the M.S. degree from Shanghai Jiao Tong University, Shanghai, China in 2020. She is currently working toward the Ph.D. degree with School of Naval Architecture, Ocean and Civil Engineering in Shanghai Jiao Tong University. Her research interest involves a new flow control method by attaching a closed flexible self-adaptive “add-ons” to the rigid bluff bodies, and the corresponding a series of two-dimensional and three-dimensional experiments. This novel flow control method is expected to significantly reduce the drag and obtain other dynamics benefits. This flow control method raises a new kind of FSI problem of the rigid-flexible couple system with respect to the interaction of external and internal fluids, and offers an opportunity for some real-life situations and potential applications.

Authors:

Yakun Zhao State Key Laboratory of Ocean Engineering
Xinliang Tian State Key Laboratory of Ocean Engineering
Huanyu Zhang State Key Laboratory of Ocean Engineering
Shuyue Sun State Key Laboratory of Ocean Engineering
Xiaoxian Guo State Key Laboratory of Ocean Engineering
Tao Peng State Key Laboratory of Ocean Engineering