4th CONFERENCE ON ADVANTAGES AND APPLICATIONS OF GID The Personal Pre and Post Processor Ibiza 2008 PFEM APPLICATIONS IN FLUID-STRUCTURE INTERACTION PROBLEMS M.A. Celigueta, A. Larese and S. Latorre International Center for Numerical Methods in Engineering (CIMNE) Campus Norte UPC, Edifici C1, Gran Capitan, 08034, Barcelona e-mail: maceli@cimne.upc.edu , antoldt@cimne.upc.edu latorre@cimne.upc.edu web page: http://www.cimne.com/pfem Key words: PFEM, Fluid Dynamics, FSI Abstract. In the current paper the Particle Finite Element Method (PFEM), an inno- vative numerical method for solving a wide spectrum of problems involving the interaction of fluid and structures, is briefly presented. Many examples of the use of the PFEM with GiD support are shown. GiD framework provides a useful pre and post processor for the specific features of the method. Its advantages and shortcomings are pointed out in the present work. 1 INTRODUCTION Nowadays there is an increasing interest in the development of robust and efficient numerical methods for the analysis of engineering problems involving the interaction of fluids and structures accounting for large motions of the fluid free surface and the existence of fully or partially submerged bodies. Examples of this kind are common in ship hydrodynamics, off-shore and harbor struc- tures, ocean engineering, modeling of tsunamis, spillways in dams, free surface channel flows, liquid containers, stirring reactors, mould filling processes, etc. The analysis of fluid-structure interaction (FSI) problems using the finite element method (FEM) with either the Eulerian formulation or the Arbitrary Lagrangian Eu- lerian (ALE) formulation encounters a number of serious problems. Among these we list the treatment of the convective terms and the incompressibility constraint in the fluid equations, the modeling and tracking of the free surface in the fluid, the transfer of in- formation between the fluid and solid domains via the contact interfaces, the modeling of wave splashing, the possibility to deal with large rigid body motions of the structure within the fluid domain, the efficient updating of the finite element meshes for both the structure and the fluid, etc. Most of these problems disappear if a Lagrangian description is used to formulate the governing equations of both the solid and the fluid domain. In the Lagrangian formulation the motion of the individual particles are followed and, consequently, nodes in a finite 1