Physics-based Simulation Of AUV Underwater Docking With A Dock By Self-propulsion

It is necessary to predict the hydrodynamic performance of AUV underwater docking accurately to improve the docking success.In this study,a physics-based simulation of AUV underwater docking by multi-block hybrid grids combined dynamic layer method and UDF(User Defined Function)was presented.This method adopts moving sub-domain substituting for moving boundary used in traditional dynamic mesh method.This method can run fast at a desktop computer for 14 days for this simulation;The research in this paper mainly includes the following results:Firstly,after the improvement of the grid system,the straight sailing numerical simulation of AUV in self?propulsion statement is completed,and the numerical simulation results are compared with the experimental data.It is found that the four groups experimental values are agree well with the results of the physical simulation,which indicates that the results of the numerical simulation is highly accurate.Secondly,the propeller is applied with rotating speed of 450 RPM and 600 RPM.When the uniform speed is approached,the AUV keeps the uniform motion docking.It is found that the higher speed has a greater influence on the surface pressure of the DOCK wall.During the docking process,the speed curve of AUV and the resistance curve of AUV will fluctuate.This kind of fluctuation is caused by the DOCK'S hindrance to AUV at the beginning,and after the AUV head completely enters the DOCK,the DOCK also adsorbs AUV.Finally,The numerical simulation of deceleration docking adopted with physics-based simulation.AUV accelerates sailing in 3.7s respectively at 600RPM.The rotating speed of the propeller is gradually decreased,and the velocity of AUV is reduced from 1.2 m/s to 0.65 m/s in about 7 s.During the brake docking process,the AUV sails to DOCK by inertia.At this time,the propeller has a damping effect,which urges the velocity reduction of the AUV.The velocity of AUV drops from 1.2 m/s to 0.55 m/s in about 8s.The terminal speeds of the two dockings meet the requirements for reducing the docking impact force.The innovative results of this article:(1)Dynamic grid update method uses dynamic layering method.This method adopts moving sub-domain substituting for moving boundary used in traditional dynamic mesh method,which significantly shortens the calculation cycle and improves accuracy(2)The AUV is no longer traditionally applied force or speed,but applied the propeller rotating speed.A physical numerical simulation method is applied to achieve self-propulsion numerical simulation.(3)In the study of underwater docking,the AUV in the self-propulsion state to docking,whch could predict the hydrodynamic around the DOCK accurately.In order to achieve the braking effect,the way of a linear change of the propeller rotating speed and without rotating speed are used to explore the braking effect and the resistance of the AUV.