Numerical Analysis Of Hull-Propeller-Rudder Fully Coupled Flow Field Based On Oversetting Grid Technology

The inland waterway is influenced by the width,curvature,and topography of the river bottom,the direction of water flow is complex and variable,and the majority of ships are in the oblique flow field,which has a certain impact on the safety of ship navigation.In order to improve the economic benefits of shipping,the development trend of large-scale ship main dimensions is gradually formed,and the ratio of navigable water depth to ship draft is decreasing.In addition,the existence of siltation at the bottom of part of the channel will also lead to a further reduction in the navigable depth of the channel,and ships will be more significantly affected by the shallow water effect.Therefore,it is necessary to investigate the propeller-rudder interaction in the oblique flow field and the hull-propeller-rudder system interaction in the shallow water channel.In this thesis,the interaction of propeller-rudder system in oblique flow and the interaction of hull-propeller-rudder system in shallow waterway are studied.Based on the setting grid technology,the SST k-ω turbulence model is introduced to solve the RANS equation.The STAR-CCM+ software is used to simulate the propeller-rudder system in oblique flow,the hull-propeller system in shallow water channels,and the hull-propellerrudder system coupling respectively.The numerical simulation of the propeller-rudder system in oblique flow is carried out with different oblique flow angles and rudder angles as parameters.The effects of oblique flow angle and rudder angle on the hydrodynamic characteristics of the propeller are investigated from four aspects,such as hydrodynamic characteristics,vortex structure evolution,unsteady bearing force,and fluctuating pressure.Compared with the propellerrudder system interaction in open water,the non-uniformity of the flow field behind the ship is more complex and the interaction is more complicated.Therefore,the numerical simulation of hull-propeller and hull-propeller-rudder coupling in shallow waterways is carried out.In the process of analyzing the performance of ships in shallow waterways,the parameters of the hull-propeller system and hull-propeller-rudder system are compared to study the influence of different water depth-draft ratio(h/T)on ship performance and degree of freedom,and the effect of the rudder on the ship is explored.At the same time,the effect of the rudder on the propeller is explored by analyzing the evolution of the vortex structure and excitation force behind the propeller.By analyzing the change of fluctuating pressure on the rudder surface,the effect of the propeller on the rudder is explored.The findings of the study were as follows.(1)In the oblique flow field,the hydrodynamic characteristics of the propeller will be improved,and the lateral force change is particularly obvious.The existence of the rudder will not only promote the hydrodynamic characteristics of the propeller,but also have a rectification effect on the flow field behind the propeller.When the rudder angle is close to the oblique flow angle,the lateral force will be suppressed.Rudder angles and oblique flow angles will affect the frequency domain peak of unsteady bearing force and fluctuating pressure.(2)The existence of the rudder behind the propeller will promote the influence of the shallow water effect on the ship,and the propeller excitation force will increase.With the decrease of water depth draft ratio(h/T),the fluctuating pressure induced by the propeller and the fluctuating pressure of the rudder surface decrease first and then increase.