A full immersed boundary solution coupled to a Lattice-Boltzmann solver for multiple fluid-structure interactions in turbulent rotating flows

This paper presents a Fluid-Structure Interaction (FSI) model based on an Immersed Boundary Method (IBM) which is applied to the transport of rags in waste water pumps. The IBM is used both to handle the flow in presence of moving rigid solids with arbitrary geometries, and to couple the fluid equations with the structural dynamics of flexible slender solids. The whole FSI model involves the combination of four numerical blocks: (i) a Lattice-Boltzmann solver for the fluid equations, (ii) a solid solver to solve the structural dynamics (if flexible solids are considered), (iii) the IBM to perform the coupling fluid-solid, and (iv) collision models for the coupling solid-solid. The present IBM is based on a direct-forcing approach available in the open-source library Palabos. In the first part of this paper, the accuracy of the IBM is assessed for single-phase flow applications. Particular attention is paid to the prediction of integrated and averaged quantities. The results show good agreements with experimental data. The second part deals with the validation of the proposed FSI-IBM model for solving the interactions between the fluid and flexible slender structures. Quantitative and qualitative comparisons have been carried out against benchmark cases and have demonstrated the good stability and accuracy of the model. The proposed collision models are also assessed in terms of stability and relevance. Finally, simulations of the rag transport in a waste water pump have shown to give stable and consistent results, as well as good insight on the probability of occurrence of clogging. (C) 2019 Elsevier Ltd. All rights reserved.