Abstract
The paper describes re-meshing techniques used for modelling computational domains with moving boundaries. The techniques are applied in a case study of accurate finite element modelling of droplet motion. The simulation takes place in a 3D domain. Locally the mesh is divided into two parts – a droplet and its surroundings. The part of a mesh around the droplet is composed of prismatic elements forming a thin layer to resolve better the boundary layer around the moving droplet. The rest of the domain is split into tetrahedrons using Delaunay triangulation. Nodes on the surface of the droplet, during the FE simulation, move relatively to the surrounding material creating a moving boundary of the domain. The quality of the mesh deteriorates in the vicinity of the moving boundary. At each stage of numerical simulation the quality of the mesh is monitored and certain measures, like smoothing, are used to improve it. At certain moment it becomes impossible to retain the quality of the mesh without deleting some elements and creating new ones. The re-meshing is first done locally, and if it does not suffice, it is spread over a larger part of the domain. The meshing algorithm, used in the whole process, is based on the Delaunay triangulation. Some modifications are done using the concept of the layer of prismatic elements around the droplet. The objective of the newly developed software is to provide proper mesh management for process simulations with moving boundaries and, possibly, boundary layers. A welding process formulated with consideration of energy and mass transfer to the weld pool is analysed as an example. The process modelling requires the proper consideration of a filler material flow to the weld pool and involves transport of filler material droplets through the welding arc, i.e. plasma beam, to the weld pool.