Two computational models for simulating the tumbling motion of elongated particles in fluids

• Simulation of fibers in low Reynolds number flows with two different methods.
• High performance lattice Boltzmann simulations on advanced supercomputers.
• Physical validation and systematic comparison of LBM and SBF simulations.
• Examines influence of particle shape, walls, and inertia on the fiber motion.
• Visualizations and animation of the flow field around two tumbling spherocylinders.

Suspensions with fiber-like particles in the low Reynolds number regime are modeled by two different approaches that both use a Lagrangian representation of individual particles. The first method is the well-established formulation based on Stokes flow that is formulated as integral equations. It uses a slender body approximation for the fibers to represent the interaction between them directly without explicitly computing the flow field. The second is a new technique using the 3D lattice Boltzmann method on parallel supercomputers. Here the flow computation is coupled to a computational model of the dynamics of rigid bodies using fluid–structure interaction techniques. Both methods can be applied to simulate fibers in fluid flow. They are carefully validated and compared against each other, exposing systematically their strengths and weaknesses regarding their accuracy, the computational cost, and possible model extensions.