Numerische Optimierung von Schiffen mit VSP: automatische Gittergenerierung

Abstract

The project SimuVSP concentrates on the numerical optimization of ship geometries, equipped with a Voith-Schneider-Propeller. The optimization problem is divided into four parts: the parametric modeling of ship hull geometries, the automatic grid generation of these types of vessels, the CFD-computation and the optimization itself. This dissertation focuses on the automatic grid generation, which is essential for the optimization of such geometries. Firstly, foundations and various algorithms for grid generation are described. In particular, the grid quality, paving-algorithm, algorithms to obtain tetrahedrons and meshing methods to obtain hexahedrons are addressed. In the numerical flow simulation, the focus is specifically on the Finite-Volume-Method, which primarily demonstrates the relationship of the results of such a simulation with the underlying grid. The detailed description of the developed mesh generation tool, vmesh, includes the meshing algorithms, the meshing concept and the handling of the program. This tool automatically generates a hybrid quality grid for CFD-calculations for complicated geometries. The grid for the CFD-computation is generated for the complete model of the geometry. The concept for the grid is based on a layer model and the idea of using a hybrid grid, consisting of hexahedrons, tetrahedrons and pyramids. To make this possible, an o-set-algorithm was developed which enables the generation of a volume grid of hexahedrons for the boundary layer out of a surface mesh of quadrangles. Moreover, at this time, there are no documented algorithms. Subsequently, the geometry-based optimization and the mesh-based optimization, which are implemented in vmesh, are presented. Lastly, the grids generated by vmesh for various geometries and the achieved results from the comparative calculations and the optimization are demonstrated.