Experimental Investigation Into SWATH Ship Motions and Loadings

The main objectives of this thesis are firstly to present experimental data of SWATH (Small Waterplane Area Twin-Hull) ship motions and dynamic loadings, and secondly to compare the experimental data with the existing numerical modellings for validation purposes. The experiments were conducted by employing a model of tandem strut per hull configuration (SWATH1) . The basic idea of using this configuration is as the SWATH ship is a relatively new concept of advanced marine vehicle, and as there can be a wide range of configurations, experimental data on any particular configuration, such as the SWATH1 model, is very limited. The first and second chapters of this thesis will overview the basic concept of SWATH ships development and the theoretical background of SWATH ship motions. SWATH1 model motions in three different sea heading, namely beam, quartering and head seas are investigated. The experimental results are then presented together with the theoretical predictions based on two-dimensional strip theory and three-dimensional sink-source technique. The agreement amongst the three sources is then discussed. The usefulness of the experimental data from the previous work in improving SWATHL computer program is briefly described. Further experiments are set up to investigate the dynamic loads on the SWATH1 model in regular beam and quartering seas. The investigations are focused on the bending moment on the cross structure and vertical forces on the struts. The data generated is important for a study of SWATH structures. From a practical point of view, the motion and structural loading characteristics of a SWATH ship in regular seas are meaningful if the data generated can be used for predicting the motions and loadings in random seas. The only reliable method to accomplish this task is the application of spectral analysis. This is outlined in chapter seven, including evaluation by making use of SWATH seakeeping criteria. Recommendations for future experiments on SWATH model motions and loadings are outlined in the conclusions