Analysis Of The Hydrodynamic Performance Of AUV During Direct Navigation In Narrow Waters

China has a vast territory and is severely restricted by the uneven distribution of water resources in time and space.The construction of long-distance and cross-regional water transfer projects such as water transfer tunnels can effectively regulate the distribution of water resources.After a long-distance water conveyance tunnel is used for a period of time,there will be safety problems such as leakage of the tunnel wall and local collapse.Autonomous underwater vehicle(AUV)can navigate freely in tunnels because they are not limited by cables,which has huge advantages over traditional detection methods.In order to take clear wall photos,AUV usually needs to sail close to the wall when the water quality is not good enough,and is easily affected by wall disturbance.If it is a pressureless tunnel,it may also be disturbed by the free liquid surface,and the inhomogeneity of the tunnel flow field will also have a certain impact on the hydrodynamic performance of the AUV.Therefore,it is of great significance to study the hydrodynamic performance of AUV in the tunnel flow field.The tunnel flow field is a typical narrow water area for AUV in operation.In this paper,the main research objects are the flow fields of the large,medium and small three-scale ellipsoidal revolving body AUV,rectangular cross-section open channels and horseshoe-shaped non-pressure tunnels,and the following studies are done:(1)Hydrodynamic experiment of AUV in circulating water tank.A small-scale ellipsoid revolving body AUV model experiment was carried out in a rectangular cross-section circulating water tank to observe the changes of the hydrodynamic force of the AUV under different flow rates and angles of attack in the center of the flow field,and numerical simulation calculations were carried out for the working conditions in the experiment,and the comparison experiments were carried out.The results and simulation results verify the accuracy of the numerical calculation.(2)Simulation calculation of hydrodynamic performance of AUV in rectangular open channel.Firstly,the situation of different scales of AUV centroids hovering at different attitudes in the center of the open channel with flow velocity was numerically calculated,and the changes of the hydrodynamic performance of the three scales of AUV affected by the boundary were compared,and the influence of the clogging effect was studied and the appropriate choice for the follow-up research was made.The AUV scale,that is,the large scale.Then,the forces and moments of the large-scale AUV when hovering near the free liquid surface or the wall surface in a rectangular open channel with a flow velocity were numerically calculated,and the change law of the hydrodynamic performance of the AUV when hovering at different positions in the open channel was studied.Then,using the control variable method to change the distance between one boundary and the AUV at a time,the influence of various boundary forms such as free liquid surface,bottom wall surface and side wall surface on the hydrodynamic performance of the AUV and the relationship between the AUV and the boundary were studied respectively.Dimensional distance relationship.After that,the working conditions of the self-propelled AUV in the still water open channel at different initial positions in the open channel section were numerically calculated,and the calculation results were compared with the force and moment of the AUV in the open channel with flow velocity.Then,the self-propelled condition of the AUV in the open channel with flow velocity was numerically calculated,and the relationship between the respective proportions of the flow field velocity and the AUV speed and the degree of the AUV being disturbed by the flow field boundary was analyzed when the relative velocity of the AUV and the flow field was the same.(3)Simulation calculation of the hydrodynamic performance of AUV in a horseshoeshaped unpressurized tunnel.The flow field of the rectangular open channel is replaced by the flow field of the horseshoe-shaped unpressurized tunnel with the same section size,and the hydrodynamic performance of the large and small AUV when sailing in it is numerically calculated,and the effect of the change of boundary form on the hydrodynamic performance of the AUV is studied Affect the law.