Research On The Multidisciplinary Optimization Of Ro-Pax Trimaran

As a type of high performance craft, high-speed trimaran has great advantages no matter in stability, resistance, seakeeping or other aspects. However, in the process of ship designoptimization, the various performances of trimaran are not harmonious and unified in the same direction. Therefore, it will be the trend of modern ship design to enhance the overall performance of the ship according to the actual demand. Multidisciplinary design optimization method is suitable for solving complicated system engineering, and it is used to optimize a Ro-Pax trimaran, combined with its performance analysis.Based on the characteristics and design requirements of the high-speed Ro-Pax trimaran,design variables are selected which are related to the outrigger layout. Stability, resistance,seakeeping and general arrangement are determined as the sub-disciplines in MDO, and the MDF optimization framework with approximate models is constructed.Each sub-discipline has a mathematical model for multidisciplinary optimization analysis. Under typical loading conditions, trimaran’s stability is checked according to the HSC code. The GZ criterion in dangerous loading condition is chosen as the stability model.Based on FLUENT, the total resistance of trimaran model is calculated and transformed into real ship data with three-dimensional conversion. The real ship resistance calculating is the sub-discipline model. Based on AQWA, frequency domain analysis is carried on, and the meaningful value of rolling response in the transverse wave of 6 level sea state becomes the simplified seakeeping index. Otherwise, the deck area changes with ship hull transformation,the loading capacity of vehicles and passengers is used to set up a piecewise function as the analysis model of general arrangement.In the multidisciplinary analysis, system layer is an economic model, which has the transportation costs as an index, including the analysis of resistance and general arrangement.Building a MDF framework, system analysis and sub-discipline approximation models are integrated in Isighf software. NSGA- II algorithm is used to optimize the multidisciplinary and multi-objective problem of the high-speed Ro-Pax trimaran which has the economy and seakeeping index as the objective function.The single objective optimization of the minimum total resistance and transportation cost and another multi-objective optimization with layout model changed are designed. With comparison and analysis, an optimized ship form is selected and compared to the hull form ofthe original trimaran. The result indicates that the optimized hull form has the integral improvement in economy and seakeeping with the expense of the optimal resistance performance.