Study On Hydrodynamic Performances Of Multi-propeller System With Ship Hull

In recent years,with the rapid development of the national economy,the demand for transportation of personnel and cargoes in various industries has grown vigorously and the transportation business,including water transportation has flourished.In order to satisfy the large thrust demand and reduce the pressure pulsation on the propeller,the multi-propeller propulsion system is adopted in large ships.However,with the increase of propeller number,the hydrodynamic performances of propeller is more and more significant.At the same time,when the propeller interferes with each other,the efficiency is also different from the efficiency of a single propeller.For this reason,the research on hydrodynamic performances of multi-propeller system has gained the attention of domestic and foreign scholars.After consulting the relevant literatures and referring to the previous research,this paper decided to use the method of combining numerical simulation and model test to study the varies trend of the multi-propeller system’s hydrodynamic performances under different working state.In the numerical simulation,first of all,the geometric model is constructed in CATIA,secondly,the mesh model is divided in ICEM and the propeller rotation is simulated by the sliding mesh,last but not least,the calculation parameters are set in ANSYS,the boundary conditions are defined by UDF,the free surface is traced by the VOF method and the numerical simulations are carried out.In the model test,the frame line plan is drawn in AutoCAD;after the scale model is processed,the draught and attitude of the model are adjusted in the towing pool and the self-propulsion test is carried out.Therefore,this paper has done the following work:(1)In simluations,ship goes forward without changing the direction.Besides the working state of normal rotation,the working state of rest(free rotating)and dragged(locked)are selected.When the propeller is in the same working state,the greater the propellers’ rotation speed,the higher the speed.Under the same propeller working state,changing the speed of the ship the rotation speed of propellers to analyze the interaction between the propeller’s hydrodynamic performances.Under the same speed,changing the propellers’ working state to analyze the interaction between the propeller’s hydrodynamic performances.(2)In simluations,ship turns a corner and giving the rudders a rudder angle.Selecting the working state of normal rotation,rest(free rotating)and dragged(locked)to carry out numerical simulations.When the propeller working state is same,the speed increases with the increase of propeller rotation speed.Under the same propeller working state,changing the rudder angle to analyze the interaction between the propeller’s hydrodynamic performances.(3)In engineering practice,ships should avoid the propellers’ working state of rest(free rotating)and dragged(locked)as much as possible;after the propellers are rest,the working state of locked can be used to replace the working state of free rotating;after the propellers are rest or dragged;the ship should decrease the speed to reduce the propellers’ thrust fluctuation and torque fluctuation;in addition,it can also reduce the thrust fluctuation and torque fluctuation of the propeller by changing rudder angle.