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Numerical simulation of oscillating-cylinder effects on a downstream cylinder wake using lattice Boltzmann method

Z. Guo
National Laboratory of Coal Combustion, Huazhong University of Science and Technology Wuhan 430074, P.R. China

Yu Zhou
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong; Institute for Turbulence-Noise-Vibration Interaction and Control Shenzhen Graduate School, Harbin Institute of Technology Shenzhen, 518055, China

Chuguang Zheng
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, China

Sinopsis

This paper proposes to use a newly developed lattice Boltzmann technique to simulate the wake of a streamwise oscillating cylinder in the presence of a downstream stationary cylinder. The oscillating frequency ratio fe/fs, varies between 0 and 1.8, where fe is the oscillating frequency of the upstream cylinder and fs is the natural vortex shedding frequency of an isolated stationary cylinder, and the oscillating amplitude A is fixed at 0.5 cylinder diameter, D. Three typical flow structures, depending on fe/fs have been identified at the cylinder center-to-center spacing L/D = 3.5, which are in excellent agreement with experimental data. The flow structure remains unchanged for the same fe/fs as L/D is increased to 6.0, but changes drastically at a low fe/fs for L/D = 2.0. It is proposed that, beyond a critical L/D, vortices are formed between the cylinders and the flow structure is independent of L/D. But, below the critical L/D, the free shear layers separated from the upstream cylinder may reattach on the downstream cylinder, thus leading to a different flow structure from that above the critical L/D despite of the same fe/fs and A/D. The lift and drag coefficients associated with the two cylinders are examined in detail for each flow structure.