OpenFSI: A highly efficient and portable fluid–structure simulation package based on immersed-boundary method

Abstract

We have developed a highly efficient and portable fluid–structure interaction (FSI) simulation package, so-called OpenFSI. Within this package, the structure dynamics is accounted by a lattice model (LM) implemented in the framework of Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), demonstrating the same accuracy as finite element analysis. The fluid flow is resolved by Palabos, which adopts the Lattice Boltzmann method (LBM) to efficiently solve the Boltzmann equation that can recover the Navier–Stokes equation in mesoscale. Additionally, the immersed boundary method (IBM) is employed to couple LM and LBM together, therefore endowing the flexibility to choose alternative solid and fluid solvers. The whole simulation is fulfilled within the framework of Palabos, and the LAMMPS framework is called in Palabos as an external library and coupled through IBM. To demonstrate the capability and accuracy of the proposed package, the validations for the LM are first performed by conducting the deflections of two-dimensional (2D) and three-dimensional (3D) beams in LAMMPS, and comparing the results with those in finite element analysis. Followed are the classical benchmarks of flow passing 2D flexible beam behind a cylinder and 3D flow passing a fixed cylinder. In the results, the free-falling of spheres and flapping of a deformable plate in cross-flow are investigated. Furthermore, the possibility to study complex FSI phenomena is demonstrated by the cases of spheres passing a dam and swimming of microswimmers. Lastly, the efficiency of this simulation package is explored by examining an extremely large system with thousands of red blood cells in blood flow. The OpenFSI package is found to have excellent linear scalability up to 8192 processors, due to the particle-based LM and LBM for structure and fluid flow respectively, as well as advanced cyberinfrastructure of LAMMPS package. Therefore, OpenFSI presents an alternative option to efficiently solve large scale FSI problems, hence to facilitate the unveiling of underlying physical mechanisms.