A coupled flow and beam model for fluid–slender body interaction

Abstract

In this study, a coupled numerical model for simulation of 3D flow interacting with a slender body is proposed. A discrete-forcing immersed boundary method is implemented to couple the fluid motion and structure deformation. To model the dynamic response of a slender structure, an efficient nonlinear beam model is developed. A new surface reconstruction method is proposed to accurately represent the occupation of the moving structure with different cross-sections in the fixed Cartesian grids of the fluid domain. A quadratic interpolation based on the least-squares method is proposed to realize the local fluid velocity near the relocated solid surface. To validate the model, several fluid–structure interaction problems including a flexible plate attached to a circular cylinder in a flow, a flexible flag in a flow, etc. are simulated. The numerical results are in good agreement with reference results from either experiments or numerical modelling. The model is further employed to investigate the vortex-induced vibration of a flexible riser under unidirectional and oscillatory flow conditions as well as impulse force analysis for a swinging carangiform swimmer in different swing frequencies, the latter has a varying cross-sectional shape along the body’s central axis.