Research On The Method For Calculating The Ship Hydrodynamic Interaction Based On Acceleration Potential

With the development of ships in the direction of large-scale and intelligence,the autonomous navigation of ships in shallow water such as ports and waterways has become a difficult problem to be solved urgently.In order to solve the problem of real-time calculation of hydrodynamic interaction forces of ships in shallow water,improve the reliability of autonomous navigation and autonomous decision-making systems,provide more accurate external load input for ship control and intelligent navigation system,and ensure the navigation safety of large ships in shallow water.In this thesis,a method for calculating ship hydrodynamic interaction forces based on acceleration potential is devised.Firstly,this method uses the potential flow theory and the panel method to solve the velocity potential boundary value problem.Secondly,it solves the acceleration potential boundary value problem based on the acceleration potential theory.Finally,the hydrodynamic interaction force is obtained through the unsteady Bernoulli integral equation.In order to validate of this method,verification is carried out against the analystic solutions for the sphere and ellipsoid.By comparing the added masses,pressure distribution,hydrodynamic force,etc.,and with relatively finer eometric approximations,the relative error is in general less than 5%.Secondly,compared with the experimental data for hydrodynamic interaction forces,it is found that the hydrodynamic error under different working conditions is less than 25%,which is within the acceptable range,and the feasibility of the method for complex flow problems is verified.Therefore,this method can be applied to real-time calculation of hydrodynamic interaction forces in shallow water,and can be potentially integrated with control and/or decision support system.In order to explore the influence of various parameters on hydrodynamic interaction forces on ships moving in shallow water,the influence of time step,number of surface elements,number of mirror images,etc.on the calculation accuracy and calculation efficiency are investigated,and the choices of relevant parameters are optimized to ensure that the results for ship-ship hydrodyanmic hydrodynamics can be obtained in real time to meet the requirements of online calculation.Finally,a case of hydrodynamic interaction between two ships in shallow water is analyzed,and the effects of different water depths,lateral distances and sailing speeds on ship hydrodynamic interaction forces are explored separately under the circumstances of head-on encounter and overtaking.The time histories of the lateral force,longitudinal force and yaw moment of the ship during the interacting processs is obtained,and the extrema of hydrodynamic forces are analyzed,and it is found that the peak lateral force usually appears when the two ships are aligned at midship,while the surge force and the peak yaw moment usually appear when the longituadinal clearance is zero,and the overtake maneuver is often more dangerous than the encounter condition.Due to its computational efficiency,the acceleration potential method meets the requirements of real-time calculation,and can effectively overcome the numerical oscillation phenomenon of the traditional constant panel method,which is of great significance in calculating the hydrodynamic interaction forces of ships in shallow water.At the same time,the drawbacks of this study are also summarized in several prospects,in the hope of providing references for the development of intelligent navigation systems.