Transactions of Nanjing University of Aeronautics & Astronautics
Computational Study on Interaction Between Swimming Fish and Drifting Vortices Behind the Cylinder
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Abstract:
To predict the flow evolution of fish swimming problems， a flow solver based on the immersed boundary lattice Boltzmann method is developed. A flexible iterative algorithm based on the framework of implicit boundary force correction is used to save the computational cost and memory， and the momentum forcing is described by a simple direct force formula without complicated integral calculation when the velocity correction at the boundary node is determined. With the presented flow solver， the hydrodynamic interaction between the fish-induced dynamic stall vortices and the incoming vortices in unsteady flow is analyzed. Numerical simulation results unveil the mechanism of fish exploiting vortices to enhance their own hydrodynamic performances. The superior swimming performances originate from the relative movement between the “merged vortex” and the locomotion of the fishtail， which is controlled by the phase difference. Formation conditions of the “merged vortex” become the key factor for fish to exploit vortices to improve their swimming performance. We further discuss the effect of the principal components of locomotion. From the results， we conclude that lateral translation plays a crucial role in propulsion while body undulation in tandem with rotation and head motion reduce the locomotor cost.
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Project Supported:
This work was supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions （PAPD）. The authors realize that the time available for a review of such an ambitious subject are limited and， thus， regretfully， we are unable to cover many important contributions. The authors would like to acknowledge the following people for their assistance： GAO He， YANG Limin， and LI Longfei. They are members of the Key Laboratory of Unsteady Aerodynamics and Flow Control of Ministry of Industry and Information Technology， Nanjing University of Aeronautics and Astronautics.
Clc Number:
TN925
CHINA AERO-SCIENCES
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