Determination of heave and pitch motions for Wigley III hull using program pdstrip and CFD approach

Ships are built in order to carry cargo, passenger, etc. upon the sea. A ship is expected to complete her mission suitably when encountering heavy weather and wave conditions. The general performance of ship and achievement of a ship design depends on having a good seakeeping performance. For this reason, estimation of ship motions is quite important in the design stage. Ship motions, which is vitally important for a safe and effective navigation of a ship, are predicted with different ways. In this dissertation, ship motions are investigated using computational methods and experimental data. Program PDStrip which is based on Strip Theory Method and publicy available and Star CCM+ as a CFD code, which is based on finite volume method, are used in order to compare experimental results. Results of the experiments, which were carried out at the Ship Hydromechanics Laboratory of the Delft University of Technology for Wigley model III are used for validation of both methods. The Program PDStrip, which is a open source software developed by H. Söding and V. Bertram based on potential approach can calculate ship motions and forces. To use Program PDStrip, firstly, input and geometry files are prepared in .txt format. Then Response Amplitude Operator (RAO) data are obtained for heave and pitch motions in output file in .txt format. The Star CCM+ is one of the popular commercial code and powerfull tool to simulate engineering problems based on viscous flow approach. In this study, geometry creation of ship model is done and discretized, boundary condition is determined, ship and wave properties are specified in this software and then ship motions are calculated and plotted. These responses have multiple peaks for time series of heave and pitch thus fast fourier transform is used to obtain corresponding response spectrum and only exact value of ship motion. For this purpose, Fast Fourier Transform analyzer is performed for every plots with a special software which is called FFT Properties. In this paper, the prediction the motion and seakeeping performance was presented at Fr= 0.2, 0.3 and 0.4 with a single wave condition. In the results of study, heave RAOs were calculated by PDStrip showed a better agreement compared to obtained by Star CCM+ as the Froude numbers increases. In other respect, Star CCM+ results had much more aligment with experimental data than PDStrip results for pitching motion with increasing Froude number and wave length / length of model. Furthermore, the maximum value of pitch RAOs were predicted with high level of accuracy via Star CCM+ in comparison with the experiments at three Froude numbers. Increase speed by higher Froude numbers causes heave and pitch peak values occured in further place of chart.