Study On The Force Analysis And Navigation Conditions Of The Ship Bridge Area Navigation

The construction of the bridge makes the river-crossing traffic smoother,but the existence of the pier has also caused many obstacles for the navigation of ship.Some research achievements have indicted already: the existence of the pier changed original water structure of the river when the ship navigated in bridge area.It has caused the flow pattern became more complex and the shipping navigation became more unpredictable,and then result in the ship bridge collision.It is important to accurately determine the real navigable clearance dimensions of the waterway to guarantee the safety and save investment.In recent years the study of flow structure near the piers become one of the hot spots,but when the bridge model test to simulate a ship sailing area is less affected by the outcome of forces and moments.This paper has discussed the navigation safety of ship in bridge area and proposed improvement measures for ship navigation condition,which are of great significance for guarantee the navigation safety of the waters near bridge area and the safety of the bridge.This paper uses the sensor and the corresponding acquisition system to measure the vertical bridge zone in each section of the ship lateral axis stress state at different flow rates It changes the distance between ship and bridge to analysis the changes of stress,and then according to it to analysis the changes of torque.The main conclusions done in this paper are as follows:1.When the ship sailing through the bridge area along the flow direction.Sides of the ship before and after each part of the process that is similar to the forces,it sustains the lateral maximum thrust when the cross-flow position appears in front of the pier.And then the thrust turn into the suction,and the lateral maximum suction occurred in the center of the pier.Along the flow direction,from the center of the pier to the region far away from the pier,all sustained the suction.And the suction is decreased by the increase of the longitudinal distance between the ship and the bridge.For the whole ship,it is unaffected by lateral thrust of the flow away from the bridge,and thrust gradually increases to a peak when the bow get to the front of the pier.Then the thrust turn into the suction,and the suction gradually increases to a peak when the stern get to the center of the peak,and the suction is decreased by increase of the longitudinal distance between the ship and the bridge.And until the ship get to the region away from bridge,the suction gradually disappeared.2.The lateral force of the ship is related to the flow velocity.The lateral force increases with the increases of the flow velocity,and the variation law of peak and lateral force have no correlation with the water depth.Meanwhile,there is a negative correlation between the lateral force and the distance between the ship and bridge.When the distance reaches to a certain value,the lateral force can be neglected.For different flow velocity,the lateral influence distances are different,and the correspondence relationships are as follows: When the Froude number was 0.124 ~ 0.289 when ranged from 1.0 times to 3.0 times the width of the bridge pier wide。3.During the process of the ship going through the bridge area along the flow direction,the rotary head torque has produced by the lateral force around the first half part of the ship,and it reaches to the positive peak and then get to the negative peak.When the bow arrived at the front of the pier,the positive peak appeared at the position where lateral thrust get maximum.And when the stern arrived at central region of the pier,the negative peak appeared.The rotary head torque appeared at the latter half part of the ship is in contrast to the first half part.When the ship went through the bridge area,because of the lateral force on the whole ship,the rotary head torque produced by the force has occurred three maximum.When the bow got to the front of the pier,the positive peak of the torque occurred.And then it decreases and turn into negative value,and the value fluctuated within a certain range,which are related to the vortex and turbulence occurred in bridge area.As the stern get to the central region of the pier,another positive peak occurred,and this second value is larger than the first one.4.The rotary head torque transfer relationship with the size of the flow rate of the lateral force is generated with the flow rate increases,and decreases with increasing lateral spacing.5.According to the existing achievements of the characteristics of ship safety at the bridge area navigation,Different scholars have analyzed different angles,including Pier surrounding flow regime analysis,flow field analysis and statistical analysis of ship motion,so as to determine the safety of the ship at a distance from the pier around different aspects,and proposed a method to determine a safe distance from the view of rotary head torque.