Abstract

Since 1999, Fraunhofer ITWM develops the so called Generalized Finite Difference Method (GFDM), a purely gridless simulation idea for flows and continuum mechanics. The method bases on moving pointclouds. The points represent numerical nodes, where the differential equations of motion are discretely solved. The points carry no mass, but are purely numerical nodes. As it moves with the flow, the pointcloud’s quality has to be maintained throughout the simulation (point filling, point removal), taking into account local refinement strategies. The moving pointcloud makes it a preferred tool to model free surface flows, FSI, moving geometries. Any partial differential equation can be solved. The central requirement for this is a reliable approximation of spatial derivatives of the discrete functions. The local approximation stencils are established by a local least squares procedure, which allow for desired orders of approximation. This approach represents a generalization of classical Finite Differences. The method is employed in different industrial applications, among them water crossing, rain water management, filling and sloshing, airbag inflation, freezing. In this presentation, we will focus on free surface flow modelling in conjunction with fluid structure interaction (FSI). Usually, FSI is put into praxis by an explicit coupling of a CFD and a structural code. In our particular example, the CFD-method is GFDM, that is coupled to some structural codes, being on the market, or to our own multibody solver (MBS) implementation. Usually, explicit coupling suffers from inherent numerical instabilities, and we show approaches how to neutralize them. As example for the coupling to a structural code, we will show the roll-over simulation of a vehicle in a sand bed, and the interaction of a vehicle with water during water-crossing. The crossing of heavy trucks over a floating bridge will be a demonstration of the coupling of GFDM to our own MBS.