Abstract. In this note, we consider preconditioned Krylov subspace methods for discrete fluid-structure interaction problems with a nonlinear hyperelastic material model and covering a large range of flows, e.g, water, blood, and air with highly varying density. Based on the complete LDU factorization of the coupled system matrix, the preconditioner is constructed in form ofLDÛ , whereL, D andÛ are proper approximations to L, D and U , respectively. The inverse of the corresponding Schur complement is approximated by applying one cycle of a special class of algebraic multigrid methods to the perturbed fluid sub-problem, that is obtained by modifying corresponding entries in the original fluid matrix with an explicitly constructed approximation of the exact perturbation coming from the sparse matrix-matrix multiplications.
MotivationDuring the past years, robust and efficient monolithic fluid-structure interaction (FSI) solvers attract a lot of interests from many researchers; see, e.g., [13,29,18,16,4,9,6], that are mainly based on algebraic multigrid (AMG) [30] , geometry multigrid (GMG) [15], preconditioned Krylov subspace [32] and domain decomposition (DD) [28,35] methods. In our previous work [23], we implemented FSI monolithic AMG solvers with the W-cycle and with a variant of the W-cycle, i.e., a recursive Krylov-based multigrid cycle, somehow related to the algebraic multilevel method, see, e.g., [2,3,20,22,37,27,1] , as well as their corresponding preconditioners for the coupled FSI problem using the AMG preconditioners [21,14,38,24] for each sub-problem in the smoothing steps. In addition, we also considered the preconditioned GMRES method (see [33]), using a class of block-wise Gauss-Seidel type preconditioners (see the earlier work in [13]), that are based on the aforementioned AMG methods for the sub-problems. As well known, such block-wise Gauss-Seidel preconditioned Krylov subspace methods may lose the robustness with respect to the mesh size, i.e., the iteration numbers for solving the coupled FSI system nearly double, 1 arXiv:1412.6845v1 [math.NA]