Research On Effective Wake For Twin-propeller Ship In Shallow Water

Twin-propeller ship is famous for his good resistance performance and propulsion performance with high efficience as well as nice speedability and maneuverability in shallow water.When moving,interaction of ship and propeller results in velocity field of propeller differing from propeller in open water.Pressure field and velocity field of ship is also different.There will be error to design propeller based on single ship wake field as wake filed of propeller.That would be of significance to anslysis interaction of ship and propeller to wake field of ship.This paper based on KCS model ship to simulate resistance and Nominal wake field for ship without propeller with CFD method.After confirming the correction,the method is used to simulate twin-propeller ship.Apparent wake field is analylised by simulating ship with propeller moving in water and is applied to have Actual wake field with the help of FORTRAN with Potential Theory.Firstly,this paper simulates KCS model resistance to compare with model test for ship resistance without propeller.It turns out keeping good consistence.And the twin-propeller ship uses this method,too.In the end,this paper analyses size effect influencing on the nominal wake field and Reynolds' law of similitude is introduced to weaken the size effect on nomial field.For apparent wake field analysis,this paper has results of ship resistance,propeller thrust and torque and apparent wake field.The paper reports simulation results and model tests keeping good consistence with error under 3%.Since then the paper can analyse the difference between ship with and without propeller.Panel method is applied to simulate propeller actural wake field.Apparent wake field is taken as initial wake field and simulates the deduce velocity before propeller.Next initial wake field is apparent wake field miniousing the deduce velocity.Propeller torque and thrust are used to tell the convergence.At last,there would be actural wake field which keeps good consistence with propeller in reality.