Research On Resistance Performance Of A Deep-towing Mothership And Its Hull Form Optimization

A good performance of resistance is the key to improve transportation efficiency and to save energy.And the hull form optimization based on resistance is an effective access to decrease ship resistance.This paper mainly research on a deep-towing mothership in two aspects: first,numerical simulation and model test are carried out to study the resistance performance of the ship;second,the parametric modeling method is used to rebuild the ship model and applied in the hull form optimization based on wave-making resistance.The numerical simulation is carried out in CFD software STAR-CCM+,using RANS equation and RNG k-epsilon turbulence model to simulate the flow field.The model test is carried out in ship towing tank of Shanghai Jiao Tong University.There is a moon pool in the middle of the deep-towing mothership which is used for delivering devices.The moon pool is closed in sailing condition and is opening in working condition.Therefore,the conditions of numerical simulation and model test are divided into sailing condition and working condition.Comparing the results of numerical simulation and model test,it demonstrates that they match well.In addition,the influence of the moon pool on ship resistance is researched and the reasons of added resistance is found,which helps with further research on resistance reduction measures.The parametric modeling processes mainly four steps: setting up characteristic parameters,generating characteristic curves,generating transversal curves and finally generating the hull surfaces.The hull form optimization is carried out in two steps: first,the global searching algorithmsobol algorithm is used for preliminary optimization.Second,the result of preliminary optimization is used as parent model to applied into second optimization using Tsearch algorithm.The results demonstrate that the wave-making resistance of optimized ships are lower than original ones,which indicates that the optimization is successful.Applying the optimized ship hull into STAR-CCM+ to calculate the total resistance and comparing the results with the result of model test,it implies that the total resistance of optimized ship hull is lower than the original ones,which verifies that the hull form optimization based on wave-making resistance is also effective in total resistance reduction.