A particle-resolved simulation approach to model the dynamics of cohesive porous sediments.

We present a numerical approach to perform particle resolved Direct Numerical Simulation (pr-DNS) of mobile, porous sediment structures. In environmental flows, porous aggregates represent sediment structures also known as flocs. By comparison with primary sediment grains, flocs are bigger in size but highly porous. The current approach represents a system which includes the Navier - Stokes equations coupled with the equations of particle motion. The porous aggregates are accounted for in the fluid domain via an additional Darcy term inside the porous medium. Together with buoyancy, collision, and cohesion forces, the motion of aggregates also depends on the coupling of the forces between the fluid phase and the porous flocs. These coupling forces are calculated directly via the volume integration of the Darcy term. The current approach also provides the opportunity to simulate scalar fields transport inside porous flocs, which might sufficiently affect the momentum balance of aggregates and further influence the mass transport for the whole system. In our presentation, we will provide a thorough validation of the novel computational approach for single particle motion and demonstrate its first applications to larger scale systems.