Research On The Simulation Method Of Ship Maneuvering Motion In Waves Based On The Combination Of Viscous And Potential Flow

Maneuverability is one of the important performances of ships,and is closely related to ship navigation performance,safety,second-generation integrity stability and economy,and has always been a hot and difficult research topic.Modern ship construction presents the development trend of large-scale,high-speed and automation,and the requirements for ship maneuverability are becoming higher and higher.When sailing in the ocean,ships are inevitably affected by wind,waves,currents and other environmental forces,which makes ship maneuvering more difficult.In order to ensure the safety of navigation,in-depth research on ship maneuverability,especially for ship maneuverability in waves,has important scientific research value and wide engineering application prospect.This paper is guided by frontier issues such as the applicability of different ship maneuverability prediction methods,the influence of ship-propeller-rudder interaction in the process of maneuvering motion,the computational efficiency of numerical simulation of freerunning maneuvering motion,and the simulation of maneuvering motion in waves considering the nonlinear motion of the ship.Research work has been carried out on the prediction method of three-degree-of-freedom maneuvering motion in calm water,the numerical simulation of six-degree-of-freedom free-running maneuvering motion in calm water considering the influence of navigation attitude,the propeller and rudder propulsion model in waves,and the numerical simulation of six-degree-of-freedom free-running maneuvering motion in waves.The main work of the paper is as follows:(1)Based on the method of captive model test simulation and hydrodynamic derivative regression,combined with the three-degree-of-freedom maneuvering equation and the propeller and rudder propulsion model,the maneuvering motion of the ship in calm water was predicted.Using the viscous flow method,the hydrodynamic force and moment under different drift angles and angular velocities were obtained through the captive model test simulation,and the corresponding hydrodynamic derivative was obtained by using the multiple regression method,and the numerical model was verified by comparing the experimental data.The self-propulsion test simulation in calm water was carried out to obtain the corresponding propeller open-water characteristics and self-propulsion factors.Combined with the obtained hydrodynamic derivatives,the propeller and rudder propulsion model in calm water and the ship’s maneuvering motion equation,the three-degree-of-freedom maneuvering motion of the ship in calm water was predicted.The accuracy and deficiency of the algorithm were compared and analyzed.(2)Based on the open source code OpenFOAM and using the viscous flow method,a numerical simulation method for the 6-DOF self-propulsion maneuvering motion of ships in calm water considering the sailing attitude was proposed.Based on the ship’s six-degree-offreedom equation of motion,the dynamic mesh method and DFBI(Dynamic Fluid Body Interaction)were combined to simulate the change of the ship’s navigation attitude during the maneuvering motion and numerical simulation of the maneuvering motion of a six-degree-offreedom free-running ship was realized.Numerical simulation of turning and zigzag maneuvering motion in calm water under different rudder angles was carried out,and the accuracy of the algorithm was verified by comparing with the experimental results.Different maneuvering motion prediction methods were compared,and the calculation accuracy and applicability of different algorithms were discussed and analyzed.(3)A propeller-rudder propulsion model considering the influence of waves and ship motion was proposed.Based on the viscous flow method and the sliding mesh technology,the self-propulsion test of a propeller-rudder propelled ship in waves was simulated.Through the self-propulsion test simulation under different wave directions and wavelengths conditions,the influence of waves on the self-propulsion factor was studied;the regression analysis was carried out on the numerical simulation results,and the influencing factors that played a decisive role in propeller and rudder propulsion were extracted to establish.The propeller and rudder propulsion model in waves is established.(4)Based on the open source code OpenFOAM,combining the viscous flow method and the potential flow method,a numerical simulation method for the maneuvering motion of a six-degree-of-freedom free-running ship in waves was proposed.In the outer flow field away from the hull,the QALE-FEM(Quasi Arbitrary Lagrangian-Euler Finite Element Method)method based on the fully nonlinear potential flow theory was used to simulate waves.In the inner flow field around the hull,the viscous flow method was used to simulate the interaction between waves and the ship.Through the matching surface and transition area,the connection between the inner and outer fields was realized,and the simulation of ship motion in waves based on the combination of the viscous flow potential flow method was realized.The ship’s maneuvering motion equation was used to realize the numerical simulation of the six-degreeof-freedom free-running maneuvering motion in waves,and the accuracy of the algorithm was verified by comparing the model test results.Furthermore,the turning and zigzag maneuvering motion of the ship under different initial wave directions,initial speed and wavelength conditions were simulated,and the influence of wave direction,wavelength and speed on the ship’s maneuvering motion was studied and analyzed.The research shows that the method based on the hydrodynamic derivative regression has a certain accuracy for the prediction of maneuvering motion in calm water,but the failure to consider the change of the navigation attitude in the process has a certain impact on the calculation accuracy.The free-running ship maneuvering motion simulation method can truly consider the influence of the navigation attitude during the maneuvering motion,and the introduction of the propeller and rudder propulsion model improves the calculation efficiency of the free-running simulation and increases the practicability of the algorithm.The established propeller and rudder propulsion model of ship sailing in waves can better reflect the influence of waves and ship motion on the propulsion efficiency of propeller and rudder,and can provide a propulsion model basis for the prediction of maneuvering motion in waves.The proposed method for simulating the maneuvering motion of a six-degree-of-freedom free-running ship in waves based on the combination of viscous flow and potential flow can greatly improve the calculation efficiency on the basis of ensuring the calculation accuracy.The research results provide means and technical support for maneuvering motion simulation of free-running ships in waves,and provide a reference and basis for algorithm selection for maneuvering performance prediction and maneuvering motion simulation in ship design and hydrodynamic research.