Generally speaking, multiphysics simulation is much harder than that for individual aspects of the physical processes. The main extra issue is how to integrate the multiple aspects of the processes with proper handling of the interactions among them. Such issue becomes quite difficult when different types numerical methods are used for the simulations of individual physical aspects. For example, when simulating a fluid-structure interaction problem with typical Eulerian finite volume method for flow and Lagrangian finite element method for structure dynamics.