Numerical Simulation Research On Hydrodynamic Performance Of Ship’s Aft Rim Thruster

Rim-driven Thruster(RDT for short)is a new type of combined thruster,which integrates permanent magnet motors,propellers,thrust bearings and other components,effectively avoiding shafting vibration and seal leakage and other problems.However,as a whole,the structural parameters of RDT are not all independent changes.Optimizing a single structural parameter cannot guarantee the improvement of the overall open water performance of the RDT.At the same time,the research on the rim thruster focuses on its own performance.Further in-depth research is also required on the performance law,flow field distribution and how to optimize the ship-enginepropeller matching design under the nonlinear coupling state of the hull and the rim thruster.Therefore,using a combination of computational fluid dynamics(CFD)and response surface analysis,a multi-objective collaborative optimization method and an analysis of the matching performance under the mutual influence of the hull wake and rim thrusters are proposed,The main research work and conclusions are as follows:(1)The ducted propeller and the RDT have similar structure and flow field distribution.The simulation results of the ducted propeller are compared with the experimental values of the model pool The calculation domain,mesh division and calculation parameter setting method of RDT model are determined.The turbulence model was determined;the grid independence test was carried out,and the number of grids of the RDT model was determined.(2)The single structural parameter of RDT is changed.The simulation results show that: the pitch ratio increases,the thrust coefficient,torque coefficient and efficiency of the RDT increase,and the increase range is obvious;when the paddle to disk ratio or longitudinal inclination angle is reduced,the hydrodynamic performance of the RDT is improved,but The improvement is not large;the hubless type has better open water performance than the hub type.(3)Using the response surface analysis method,the multi-parameter synergistic optimization of RDT is carried out.The results show that the order of the significant influence of each parameter response value(open water performance)is: pitch ratio >longitudinal inclination angle > paddle to disk ratio.The optimal structural parameters corresponding to the maximum efficiency of the RDT model are: the pitch ratio is 1.4,the paddle to disk ratio is 0.65,and the longitudinal inclination angle is 0°.The maximum efficiency can reach 52.53%,and the maximum efficiency is effectively improved by 4.57%.(4)The hull-rim thruster dynamic nonlinear coupling model is established,and the simulation results show that the hydrodynamic performance of the rim thruster under the wake condition is smaller than that under the open water condition due to the influence of the wake at the stern.The higher the flow rate,the bigger the gap.Moreover,the flow field in the stern is non-uniform,and the high pressure area gradually shifts to the right.(5)The influencing factors of the hydrodynamic performance of the rim thruster under the hull wake condition are analyzed,and it is found that: increasing the vertical distance between the hull and the thruster,the hydrodynamic performance of the RDT decreases,but the decline is small,and the maximum change range is not more than1%.By changing the cross-sectional shape of the connecting rod,it is found that the larger the force-bearing area of the connecting rod,the lower the hydrodynamic performance of the RDT.The integrated design of the propeller is studied,and two design schemes of the through-hull and trimaran are proposed.