Numerical modeling of high aspect ratio flexible fibers in inertial flows

A numerical model for the behavior of flexible fibers under inertial flows was developed by coupling discrete element method and finite volume method. The fibers were discretized into several beam segments, and the equations of motion were integrated with a 2nd order accurate explicit scheme. The 3D Navier-Stokes equations were discretized by a 4th order accurate (space and time) unstructured finite volume scheme. Momentum exchange between the fluid and fibers was enforced by including a source term of the fiber hydrodynamic force in the Navier-Stokes equations. The choice of an appropriate model for the hydrodynamic force on a fiber in a fluid flow depending on the Reynolds number is discussed and covers a range of Reynolds number between 10(-2) and 10(2). The current numerical model is validated against different experimental studies, including deflection of fiber in uniform flow, fibers in isotropic turbulent flow, and concentrated fiber suspension in channel flow. The numerical model was able to reproduce the damping/enhancement phenomena of turbulence in a channel flow as a consequence of the micro-structural evolution of the fibers. Published by AIP Publishing.