Experimental Research And Numerical Analysis On Wave Load Of Long Forecastle Ship

During the new ship design process, reasonable determination of design wave load is the significant premise and basis. The existing rules have nearly completed calculating methods or regression formulae for the ordinary ships, but for those not apply to the rules, exceptive considerations need to be taken into, like direct calculation method and model test method.The bottom lines of long forecastle ship change enormously while stern lines are flat. The block coefficient is small enough to over the scope of application of the design rule. Both bow flare and the slamming area of the long forecastle ship are large. Slamming and the waveloads arising from it cannot be ignored while slamming is harmful to local structural strength and total longitudinal bending strength of hull girder. Therefore, reasonable analysis of the design wave loads on the long forecastle ship has been to be comprised of both numerical prediction and wave load experimental investigation. The main contents of the research are as follows:(1) Numerical prediction of the long forecastle ship under different loading conditions with three dimensional linear wave loads calculation software is carried out,included frequency response and long term statistical analysis of wave loads. The long term statistical analysis was modified to include nonlinear effects using the revision method from the rule.Analysis of waveloads in the time domain with the three dimensional nonlinear calculation software is needed according to the slamming. The largest loading condition is selected. The numerical prediction provides a reference when design wave load is determined.(2) By the method of segmented model test, experiments were performed for long forecastle ship in regular waves in head sea to verify the numerical prediction. Design of shell and backbone was based on similitude principle and test in regular waves in head sea were included in wave load experimental investigation. Analysis of the experimental results of waveloads was done under different factors. The features of waveloads were summarized.(3) Make comparisons between the low frequency part of experimental results and linear theoretical predictions. To compare the experimental time history results with nonlinear theoretical predictions. The effect of slamming arising from bow flare of long forecastle ship was analyzed and summarized.(4) Wave loads and slamming loads of long forecastle ship were calculated and compared to each other on the basis of the three marine design rules. According to the wave load experimental investigation, theoretical predictions and calculation methods, a comprehensive study was pursued in selecting reasonable design wave loads. Recommended values of design wave load of the long forecastle ship were provided finally.