Numerical simulation study of the fluid-structure coupling effects of Kármán vortex street on airfoil motion with varying thickness

Abstract

This paper examines the fluid-structure interaction of rigid and passive motion of airfoils with different thicknesses in the Kármán vortex street at low Reynolds numbers through numerical simulations. Five NACA airfoils with varying thicknesses (8%, 12%, 16%, 20%, and 24%) were investigated regarding their fluid-structure interaction in the Kármán vortex street. These airfoils were positioned downstream along the centerline of a D-shaped cylinder. Employing a six-degree-of-freedom method, their passive motion was simulated, and the motion grid was generated using the elastic deformation method and local grid reconstruction technique. The analysis included examing alterations in the flow field and forces acting upon airfoils of varying thicknesses in both fixed and released states. The outcomes demonstrate that an increase in airfoil thickness amplified the traction force exerted on the airfoil within the Kármán vortex street, consequently yielding higher lateral force and torque. In the released state, the airfoil exhibited forward motion towards the D-shaped cylinder and deviated from the suction region of the Kármán vortex street due to the influence of lateral force. The study unveils that airfoils of suitable with appropriate thickness, such as NACA0012, achieved an improved equilibrium between forward speed and lateral displacement, thereby covering a more extensive forward distance. These findings provide valuable insights for the designing robotic fish that utilize vortex streets under low-flow conditions.