Smoothed particle hydrodynamics and element bending group modeling of flexible fibers interacting with viscous fluids.

This paper presents a smoothed particle hydrodynamics (SPH) and element bending group (EBG) coupling method for modeling the interaction of flexible fibers with moving viscous fluids. SPH is a well-developed mesh-free particle method for simulating viscous fluid flows. EBG is also a particle method for modeling flexible bodies. The interaction of flexible fibers with moving viscous fluids is rendered through the interaction of EBG particles for flexible fiber and SPH particles for fluid. In numerical simulation, flexible fibers of different lengths are immersed in a moving viscous fluid driven by a body force. The drag force on the fiber obtained from SPH-EBG simulation agrees well with experimental observations. It is shown that the flexible fiber demonstrates three typical bending modes, including the U-shaped mode, the flapping mode, and the closed mode, and that the flexible fiber experiences a drag reduction due to its reconfiguration by bending. It is also found that the U4/3 drag scaling law for a flexible fiber is only valid for the U-shaped mode, but not valid for the flapping and closed modes. The results indicate that the reconfiguration of a flexible fiber is caused by the fluid force acting on it, while vortex shedding is of importance in the translations of bending modes.