Flow Field Characteristics And Fluid-structure Interaction Simulation Analysis Of The Rudder System Of The Ship

Rudder system is a very important and indispensable special outfitting equipment for ships.If a ship does not have a rudder system,or if the rudder fails,it will be impossible to drive,just like a car without a steering wheel,at the mercy of the wind and waves in the sea.The rudder is a flat plate or airfoil structure,located at the stern end of the ship,usually behind the propeller.The rudder will deform and vibrate under the action of fluid,which will affect its life.Therefore,it is of great significance to study the inherent vibration characteristics and fluid-structure interaction characteristics of the rudder system.In this paper,the viscous flow field around the rudder of the ship is simulated numerically by using the CFD method of solving the RANS equation and the STT turbulence model.Firstly,the grid independence is verified,and a set of grids with moderate number and high accuracy is selected.Then the viscous flow field around the rudder blade is simulated numerically.The hydrodynamic coefficients,pressure nephograms and streamline nephograms of the rudder blade at different velocities and rudder angles are calculated,and the flow field is analyzed.The calculation results show that the lift coefficient increases with the increase of the angle of attack of the rudder.When the angle of attack is greater than a certain degree,the boundary layer separation occurs,and the vortex occurs at the tail end of the rudder.At this time,the lift coefficient begins to decrease.Modal calculation is one of the key steps in structural design of the rudder.Based on the finite element method(FEM),the natural vibration characteristics of the rudder system are simulated,and the inherent vibration characteristics of the rudder system are analyzed.The results show that the first vibration mode of rudder system is torsional mode and the second vibration mode is bending mode.It shows that the rudder is more prone to twist than the rudder bending.The vibration response of ship rudder system is analyzed based on CFD / CSD two-way fluid-structure interaction method.The effects of different inflow velocities and angles of attack on the vibration response of ship rudder system with free-play and the effects of separated flow at high angles of attack on the vibration response of rudder system are studied.The results show that the unreasonable matching of dynamic parameters may induce the linear vibration of rudder system,and the existence of free-play between transmission mechanisms may induce the non-linear vibration of ship rudder system,which may lead to fatigue damage of rudder system structure.The simulation results in this paper can provide reference for the design of fluid performance and structure of the ship rudder.