Numerical Study On Hydrodynamic Performance Of Rim Driven Thruster

The Rim Driven Thruster(RDT)is a newly developed combined unconventional propulsor,which has changed the traditional ship transmission approach from shaft driving to shaftless rim driving by the action of current.The RDT has a prominent advantage in reducing shaft construction costs,increasing capacity as well as reducing vibration and noise,which is especially suitable for application objects with limited cabin capacity and high stealthy performance,such as torpedo,submarine,warships,etc.The capturing of hydrodynamic performance plays an important role in the design and application of RDT.In this paper,the hydrodynamic characteristics of RDT and its influencing factors were studied by the combination approach of model test and numerical simulation.The research work is as follows:Considering the geometry similarity between RDT and conventional ducted propeller,the research was started from the numerical simulation of a ducted propeller by a commercial RANS solver(STAR CCM +),the calculation results were agree well with open experimental datas,which provided reliable experience for the subsequent numerical research of RDT hydrodynamic performance.The hydrodynamic performance of hub type RDT was numerical calculated with the verified CFD approach,the influence of different components on the RDT overall hydrodynamic performance was analyzed and compared with the duct propeller with the same geometrical shape blade and duct.The results show that the total thrust of the RDT is almost equal to that of duct propeller,however the rim rotor consumes torque,which lead to that the open water efficiency of RDT is lower than that of duct propeller,especially in the higher advance coefficient.This regular pattern was also confirmed in the subsequent open water tests of RDT and duct propeller,and the test results are also in good agreement with the numerical results.The lnflucing factors of hubless RDT hydrodynamic characteristics were studied by numerical simulation,parameters of with or without hub,hub ration,ring rotor geometry,the gap between motor stator and rotor were emphasized.Results show that:1)the load and efficiency of the hubless RDT are obviously higher than hub RDT.2)With the increasing of hub ratio,the load and efficiency of the RDT are reduced,butthe influence is very little.3)Rim rotor geometry has limited effects on the total thrust of RDT,while influencing the torque and efficiency of RDT.The larger rim rotor area will consume greater torque,and results in lower efficiency.4)With the stator-rotor gap growing,the load and efficiency of RDT reduced.It is suggested to desigh RDT with a small ring rotor and small stator-rotor gap.The relevant research methods and conclusions of this paper have some reference value for the further understanding of RDT hydrodynamic characteristics and its application.