Sedimentation of flexible fiber suspensions and large cluster formation at finite Reynolds number

In this work, we numerically study suspensions of flexible fibers sedimenting in an otherwise quiescent fluid. The Navier-Stoke equations are solved as the governing equations for the fluid phase. The fibers are modeled using an incompressible hyperelastic Mooney–Rivlin material description. The governing equations of both phases are coupled together using the immersed boundary method. The fibers are initially distributed homogenously in the domain under the action of gravity. The hydrodynamic interaction of fibers and surrounding fluid modifies the initial structure of fibers, and regions of low and high concentration of fibers are generated within the domain. In this work, we focus on the effect of Galileo number and the initial concentration and flexibility of fibers on the system's behavior. We present results regarding the sedimentation velocity of the suspension, the changes in local concentration, and the orientation of fibers. Finally, the statistics of clusters in the system are discussed.