Abstract 

Panel based hydrodynamic analysis is well suited for transferring seakeeping loads to 3D FEM structural models. Because panel based hydrodynamic analysis is computationally expensive, and also not very sensitive to the mesh density, it is common to first calculate seakeeping loads from a coarser hydrodynamic mesh, and then to map the panel pressure and inertia loads to the corresponding finer structural model. Various interpolation methods have been proposed to map the loads from one mesh to another. While the pressure integration results in a perfect equilibrium in the hydrodynamic model, it is difficult to get a balanced structural model through any pressure interpolation methods. To re-balance the structural model, artificial accelerations and/or point loads have to be added. Malenica et al. (2008) proposed a method which maps the panel source strength instead of the panel pressure from a hydrodynamic mesh to the structural mesh, and then formulated the equations of motion in the structural mesh. The equations of motion also included a gravity term to account for the change in the coordinate system. The method results in a balanced structural model. In this paper, the cause of the unrealistic sway and surge force due to hydrostatic restoring pressure integration is explained. A method of applying linear seakeeping pressure loads is presented. The method differs from Bureau Veritas’s approach in the following areas: 1. The corrective hydrostatic restoring force due to pressure integration is distributed to element nodes using quadratic programming; 2. There is no need to create and maintain two different models because the method only uses the structural mesh. A coarser hydrodynamic mesh is automatically generated from the structural mesh when the hydrodynamic analysis is performed; 3. The method is fully integrated within one FEA system, comprising modeling, loading, analysis, and evaluation.