Dynamic Response of Ship Hulls to Slamming Loads in Irregular Waves

[摘要] In this work the dynamic response of a ship to slamming loads in random seas was studied. This study focused only the vertical motions and loads. The motions were obtained using a linear strip method and the hydrodynamic coefficients were obtained by using the multipole expansion technique for circular shapes and a multiparametric conformal transformation which transforms a circle into an arbitrary form. Special attention was given to the common two dimensional methods to obtain the hydrodynamic coefficients and chapter 2 was dedicated to this study. In this research it is assumed that the total vertical bending moment induced by waves is divided into two components: the first one is obtained by the linear theory and the second one is due to the slamming loads which induces whipping stresses. Several formulations for the determination of the slamming pressures and loads were compared in chapter 4. The vibratory response of the ship is calculated by modelling it with two dimensional Timoshenko beam finite elements with a consistent mass formulation, which is used to determine the natural modes and frequencies. The response is obtained by modal superposition using direct integration methods. Experiments to obtain the ship motions and sea loads were carried out in the Hydrodynamics Laboratory of the University of Glasgow with a segmented model of a container ship in the ballast condition. Comparisons between the measurements and the theoretical results were carried out for the vertical motions and bending moments, and satisfactory results were obtained for some of the theoretical methods. Time domain simulations for the low and high frequency vertical bending moments were carried out for irregular seas. Some of the relevant statistical parameters involved in this process were compared in time and frequency domain. Based on the time domain simulations some statistical distributions were obtained for long term analysis for the slamming and total bending moments. The correlation between the several distributions were also analysed.

[发布机构] University:University of Glasgow

[关键词] Naval engineering