Comprehensive Study On Side Hull’s Position And Resistance & Seakeeping Performance Of Maintenance Trimaran In Offshore Wind Farms

Trimaran has excellent resistance performance and seakeeping performance at high speed. Therefore trimaran is getting more and more attention in the maintenance aspect of offshore wind farms. As a maintenance vessel in offshore wind farms, maintenance trimaran usually sails and works in the large waves. At this time, the impact of added resistance on the resistance performance of maintenance trimaran can’t be ignored. And the motion performance of pitch and heave is an important index to evaluate the seakeeping performance of maintenance trimaran. At present, there is still a lack of numerical simulation of the added resistance of high speed trimaran at home and abroad. In addition,the studies of side hull’s position of trimaran are focused on the optimization of reducing resistance in calm water, and multidisciplinary and multiobjective optimization of resistance and seakeeping performance in real sea area needs to be probed into.According to the model test data of trimaran, using CFD software FINE/Marine to study the numerical simulation method of trimaran’s resistance in calm water and added resistance and motion in regular heading waves. The accuracy of the numerical simulation method is verified by comparing the calculation results with the model test data. So as to establish multi schemes of side hull’s position of maintenance trimaran, conducting numerical calculation of each scheme’s calm water resistance and added resistance and motion response of pitch and heave. And the influence of side hull’s longitudinal position and transverse position is analyzed.In this paper, the focus is using multidisciplinary design optimization platform ISIGHT to optimize the side hull’s position of maintenance trimaran based on the performance of resistance and seakeeping in real sea. Firstly, using the CFD calculation results of each side hull’s position scheme as the sample points, and combining the specific working condition of maintenance trimaran to predict each scheme’s average added resistance and total resistance and motion significant value of pitch and heave by the spectrum method, in order to establish the approximation model of above parameters varying with side hull’s position,instead of numerical calculation. Secondly, setting the minimization of the total resistance and the motion significant value of pitch and heave as the optimization target, and setting the side hull’s longitudinal position and transverse position as the design variable. The objective function is determined by setting weight and scale factor. The approximation model is used as the database, and the multiobjective genetic algorithm NSGA-II is used tooptimize the side hull’s position. The results show that when the longitudinal position of side hull is a=0.00m(the sterns of side hull and main hull alignment) and the transverse position of side hull is b=3.50 m, the maintenance trimaran has the optimal comprehensive performance of resistance and seakeeping. So as to provide a reference for the design and the performance prediction of relevant ship type.