Naoto Mitsume

MPS–FEM PARTITIONED COUPLING APPROACH FOR FLUID–STRUCTURE INTERACTION WITH FREE SURFACE FLOW

Fluid–structure interaction analysis involving free surface flow has been investigated using mesh-based methods or mesh-free particle methods. While mesh-based methods have several problems in dealing with the fragmentation of geometry and moving interfaces and with the instability of nonlinear advective terms, mesh-free particle methods can deal with free surface and moving boundary relatively easily. In structural analyses, the finite element method, which is a mesh-based method, has been investigated extensively and can accurately deal with not only elastic problems but also plastic and fracture problems. Thus, the present study proposes a partitioned coupling strategy for fluid–structure interaction problems involving free surfaces and moving boundaries that calculates the fluid domain using the moving particle simulation method and the structure domain using the finite element method. As the first step, we apply a conventional serial staggered algorithm as a weak coupling scheme. In addition, for the verification of the proposed method, the problem of a breaking dam on an elastic wall is calculated, and the results are compared with the results obtained by other methods.

A Hybrid Finite Element and Mesh-Free Particle Method for Disaster-Resilient Design of Structures

The MPS-FE method, which is a hybrid method for Fluid-Structure Interaction (FSI) problems adopting the Finite Element method (FEM) for structure computation and Moving Particle Semi-implicit/Simulation (MPS) methods for free surface flow computation, was developed to utilize it in disaster-resilient design of important facilities and structures. In general free-surface flow simulation using the MPS method, wall boundaries are represented as fixed particles (wall particles) set as uniform grids, so the interface of fluid computation does not correspond to the interface structure computation in the conventional MPS-FE method. In this study, we develop an accurate and robust polygon wall boundary model, named Explicitly Represented Polygon (ERP) wall boundary model, in which the wall boundaries in the MPS method can be represented as planes that have same geometries as finite element surfaces.

Inundation Simulation Coupling Free Surface Flow and Structures

Water-related disasters such as tsunamis, storm surges, and floods involve fluid–structure interaction (FSI) problems with free surface flow. Since failures of artifacts are caused due to inundation, water forces and impact forces by floating objects, simulation of such problems has great importance to design for safety and robustness.In this chapter, we present a robust and efficient coupled method for fluid–structure interaction with violent free surface flow, named the MPS-FE method and its improved method. The MPS-FE method adopts the finite element (FE) method for structure computation and the moving particle semi-implicit/simulation (MPS) method for fluid computation involving free surface flow. The conventional MPS-FE method, in which MPS wall boundary particles and finite elements are overlapped in order to exchange information at fluid–structure interface, is not versatile and reduces the advantages of software modularity. We developed a non-overlapping approach in which the interface in the fluid computation corresponds to that in the structure computation through an MPS polygon wall model. The accuracy of the improved MPS-FE method was verified by solving a dam break problem with an elastic obstacle and by comparing the result obtained with that of the conventional MPS-FE method and other methods.

Parallel Analysis System for Fluid–Structure Interaction with Free-Surfaces Using ADVENTURE_Solid and LexADV_EMPS

In this chapter, we present a parallel analysis system for fluid–structure interaction (FSI) analysis with free-surfaces. It is based on a method that uses the moving-particle semi-implicit/simulation (MPS) method for flow computations and the finite element (FE) method for structural computations. The MPS-FE method is an efficient and robust approach for FSI problems involving free-surface flow. To develop the system presented herein, we use two existing open-source software modules: ADVENTURE_ Solid, a large-scale FE solver for structural computations; and LexADV_ EMPS, a library for large-scale MPS computations for free-surface flow. The explicitly represented polygon (ERP) wall boundary model employed in LexADV_ EMPS is accurate and stable, and it expresses wall boundaries as a set of arbitrarily shaped triangular polygons with appropriately imposed boundary conditions. Thus, when the ERP is used, in both the fluid and the structure computations, the fluid–structure interfaces are matched, and therefore, preprocessing of the data for FSI analysis is greatly facilitated. We demonstrate the applicability of the developed system by solving a dam-break problem with an elastic obstacle.