Numerical Prediction On Hydrodynamic Performance Of Contra Propeller

With the increase of energy consumption in the world and the fossil resources becoming more and more less,more attention has been paid to the energy-saving of ships.In recent years,a great deal of work has been done on propulsion devices for ships.During so many kinds of energy-saving equipment,compared with single propeller,directions of rotation of the two propellers of contra rotating propeller(CRP)are opposite,which can effectively reduce noise,improve propulsion efficiency and maintain good stability,so CRP become gradually accepted.At the same time,it should be noticed that due to the violent hydrodynamic interference between the front and aft propellers,higher requirements are put forward on the material and design of the propeller.Therefore,it is very important and necessary to predict the hydrodynamic performance of the CRP.CFD(Computational Fluid Dynamics)technology is booming and growing mature so that it has been widely used in the field of ship building.Based on the CFD technology,this paper uses STAR-CCM + software to study the propeller,which is mainly divided into the following aspects:1.Taking the E779 A propeller as an example,the hydrodynamic performance of the propeller is calculated by using the overlap grid technique.The velocity distribution of the wake field and the generation and development of the tip vortex are simulated,and the axial velocity field distribution characteristics are showed and confirm the accuracy of the simulation by comparing with test values.Comparing the shape of the tip vortex with that of the large-eddy simulation and the separate-eddy simulation,it is confirmed that the large-eddy simulation is the most suitable as the model for numerical calculation.2.Take the CRP6 as an example,this paper calculate the hydrodynamic performance of the propeller,compare the thrust torque coefficient at different time steps and compare with the test value to determine the appropriate time step;The hydrodynamic interference between the front and aft propeller are studied by comparing the thrust torque coefficients of single propeller.The characteristics of the wake field after the paddles are also analyzed.The effects of the evolution mechanism and the time step on the tip vortex of the CRP are studied..3.Taking the CRP6 as an example,the state of CRP under the lateral thrust state is studied,and the hydrodynamic performance is predicted.The approximate relationship between the lateral thrust force and the angle of propeller rotation is given and the changes of flow field after propellers and tip vortex are analyzed.