Study On The Influence Of Intercepter On The Speed Performance Of Waterjet-propulsion Ship And Its Scale Effect

Waterjet is a kind of propulsion device that uses the reaction force generated by high-speed jet-flow to drive the ship forward.It has the advantages of high propulsion efficiency at high speeds,good cavitation performance,and strong maneuverability,so it has been widely used on planing craft,hydrofoil craft and some surface vessels.For medium and high-speed ships,it is generally to reduce the pitch amplitude and resistance of the ship by installing stern appendages such as interceptor and stern flap.With the increasing demand for highperformance ships,the coupling application of waterjet and stern appendages such as interceptor is increasing.At present,the performance prediction of ships equipped with interceptors is mostly based on ship-model resistance test,but its prediction accuracy needs to be improved.On the one hand,the prediction method of ship-model resistance test has obvious scale effect on the flow field and hydrodynamic force around the ship due to the difference of Reynolds number between the model-scale and the full-scale ship.On the other hand,the research method of resistance test does not consider the influence of interceptor on the performance of ship propeller.This paper systematically studies the impact of interceptor on the speed performance of the waterjet-propulsion ship and its scale effect based on the research method of "model test+model simulation+full-scale simulation".The resistance and flow field test and numerical simulation of ship model with interceptor were carried out,and the influence and mechanism of interceptor on ship resistance and flow field were clarified.The speed performance simulation strategy of full-scale ship was established.On this basis,the scale effect mechanism of the resistance reduction effect of interceptor was analyzed,and the full-scale ship extrapolation method suitable for the resistance reduction effect of interceptor was modified.Finally,the model test and multi-scale numerical study of "hull+waterjet+interceptor" were carried out,and the influence of interceptor on the speed performance of waterjet-propulsion ship and its scale effect were summarized.The main contents of this paper are as follows:Firstly,based on the towing tank and the Stereoscopic Particle Image Velocimetry measurement system,the resistance and flow field measurement tests before and after the installation of interceptor were carried out.The resistance tests of ship model with different depths of interceptor were carried out,and the effects of interceptor on ship resistance,sailing attitude and wake field were analyzed.On this basis,the PIV test of the flow capture section of the waterjet-propulsion ship with the inlet closed was carried out,and whether the installation of interceptor can affect the flow capture of the waterjet-propulsion ship and its influence law were discussed.Based on the model-scale numerical simulation,the influence mechanism of interceptor on ship resistance and flow field was further carried out.The selection and convergence of turbulence model,grid number,time step size,and wall y+value were studied respectively,the analysis and validation of ship resistance,attitude and wake flow field were completed,and the numerical simulation strategy of ship resistance and flow field at model-scale was determined.On this basis,the influence degree of interceptor on the ship resistance and resistance components was analyzed,and the mechanism of interceptor on ship resistance and flow field was analyzed from the changes of ship attitude and multi-angle ship flow field.Taking the REGAL ship with international open sea trail test data as the research object,the speed performance simulation strategy of full-scale ships based on RANS method was constructed.Through solving the full-scale ship resistance and self-propulsion characteristics under various conditions,and comparing with the sea trial test data and the published simulation results of the workshop,the verification and validation of the simulation results have been completed,and the important parameters such as time step size,wall y+value,CourantFriedrichs Lewy suitable for full-scale ship simulation were obtained,forming the speed performance simulation strategy of full-scale ship.Based on the speed performance simulation strategy of full-scale ship,the resistance performance of full-scale ship before and after the installation of interceptor was solved.The differences of form factor,wave making resistance and sailing attitude between model-scale and full-scale ship were compared,and the influence law and mechanism of scale effect on different parameters were summarized and analyzed.The difference between the model-scale,full-scale and various extrapolation results of the resistance reduction effect was discussed,the scale effect mechanism of interceptor was clarified,and an extrapolation method suitable for the resistance reduction effect of interceptor was proposed.Based on model tests and model simulation methods,the influence of interceptor on the self-propulsion characteristics of waterjet-propulsion ship was studied.By comparing the experimental and simulation results of the flow capture,self-propulsion and flow field characteristics of the waterjet-propulsion ship model,the cooperative verification of the waterjet-propulsion ship model self-propulsion test and numerical simulation was completed,and the fluctuating pressure characteristics at the tip clearance of the jet pump were analyzed.The focus was on the analysis of the change of the self-propulsion characteristics of the ship model after the installation of interceptor,such as the momentum coefficient,thrust deduction fraction and propulsion efficiency,and the mechanism of the influence of interceptor on the speed performance of the waterjet-propulsion ship was explored.Finally,the self-propulsion simulation of full-scale waterjet-propulsion ship before and after the installation of interceptor was carried out.The influence law of scale effect on ship self-propulsion point,flow coefficient,torque coefficient and other parameters was analyzed,and the mechanism of scale effect was clarified by comparing the difference of internal/external flow field of waterjet-propulsion ship at model-scale and full-scale conditions.The reduction rates of effective power and delivered power of the model-scale and full-scale waterjetpropulsion ship with and without interceptor were compared and analyzed,and the scale effect mechanism of the impact of interceptor on the speed performance of waterjet-propulsion ships was analyzed.