Simulating FSI Problems via the Curvilinear Immersed Boundary Method: From Biofluids to Wind Turbines

In the curvilinear/immersed boundary (CURVIB) method developed by our group the background computational domain could be discretized with a curvilinear grid within which immersed bodies are treated as sharp-interface boundaries discretized with an unstructured triangular mesh (Fig. 1). The effect of moving immersed bodies is accounted for by reconstructing boundary conditions at the nodes in the immediate vicinity of the fluid/solid interface (IB nodes) using a quadratic interpolation (Fig. 1). The reconstruction method has been shown to be 2 nd order accurate [6]. The grid nodes inside the solid immersed body (solid nodes) are blanked out and do not affect the solution on the fluid nodes. The background grid nodes are first classified into either fluid, solid, and IB nodes using an efficient ray-tracing algorithm [1]. The curvilinear background mesh is adopted to enhance algorithmic flexibility and efficiency for internal flow problems in which the background domain can be efficiently discretized with a boundary-conforming curvilinear mesh [5]. The fluid equations are integrated in time using an efficient, second-order accurate fractional step methodology coupled with a Jacobian-free, Newton–Krylov solver for the momentum equations and a GMRES solver enhanced with multigrid as pre-conditioner for the Poisson equation [5]. The flow solver is parallelized using MPI and PETSc libraries. The fluid/structure interaction (FSI) problem is handled by the partitioned approach, i.e. the FSI problem is partitioned into two separated domains: one fluid and one structural domain [1]. Each domain is treated computationally as an isolated entity and is separately advanced in time [1]. The interaction effects are accounted for through the boundary condition at the fluid/structure interface. Both the loose and strong coupling strategies are implemented to resolve the interaction between the fluid flow and the structure's motions [1]. The CURVIB method has been applied to simulate a broad range of engineering and biological flows, including: vortex-induced vibrations [4]; pulsatile, physiologic, transitional flow in mechanical heart valves (Fig. 2) [1]; aquatic swimming [2, 3] (Fig. 3); turbulent flow in meandering rivers with hydraulic structures mounted as immersed bodies (Fig. 4); and flows past wind turbine rotors (Fig. 5). In the conference presentation, we will review major algorithmic developments of the CURVIB method and present results from the application of the method to the aforementioned problems. We will also present a recent extension of the method aimed at integrating it with overset Chimera grids, i.e. the background mesh can be discretized using several overlapping …