Study On The Influence Of Branch Inflow On Navigation Of Main Channel

The phenomenon of tributary stream inflow main stream is widespread in natural rivers.Due to the inflow of tributaries,they mix with the main stream in the confluence area,changing the original flow pattern and forming a complex flow structure,which has a certain impact on the maneuverability and safety of inland ship navigation.In this paper,the main flow field in the confluence area under different confluence angles 6,confluence ratio RQ and channel width ratio B*is systematically studied by means of numerical simulation.On the basis of this,the ship navigation experiment in the confluence area is further carried out by using the ship navigation mathematical model.The maneuvering motion is simulated under different conditions,and the variation rules of the rudder angle,drift angle and offset distance of the ship under different confluence angle,confluence ratio and channel width ratio of main and tributary channels are explored.The main conclusions of this paper are as follows:(1)The inflow of tributaries will cause obvious changes in the flow field in the confluence area.Under different working conditions,the maximum transverse velocity and elliptical contour of transverse velocity centered appear at the downstream connecting points of the main and tributary.Along the flow direction,the transverse velocity increases first and then decreases,and gradually decreases perpendicular to the direction of the opposite side of the interchange.As for the longitudinal velocity,it increases gradually along the direction of the main stream first,and also reaches the maximum value near the stagnation point in the downstream,and then gradually tends to the same value in the downstream.However,the size and range of flow velocity change in transverse and longitudinal directions of the confluence area are different with different confluence angles,confluence ratios and channel width ratios.(2)Based on the separate(MMG)hydrodynamic model,a three degree of freedom mathematical model was established to simulate the maneuvering motion of a thousand-ton ship in class III channel under different confluence angles,confluent ratios and channel width rations.With the increase of confluence angle,confluence ratio and wideband ratio,the ship needs to start steering earlier when sailing to the vicinity of the confluence area,and the steering time changes correspondingly,and the maximum drift angle increases gradually.At the same time,due to the inflow of tributaries,the upstream of the main stream is deflected,and the ship begins to deviate from the course in the upstream and reaches its maximum value in the downstream of the confluence area.With the increase of confluence angle,confluence ratio and width ratio,the maximum yaw distance increases gradually.(3)Response surface test design was established for the maximum deviation distance of class III channel navigation of 1000-ton ships in the confluence area and three influencing factors including confluence angle,confluence ratio and channel width ratio of main and tributary channels.The corresponding regression formula was fitted.After testing,the formula passed significance test and could be used as theoretical guidance for ship navigation...