Research On The Effects Of Flow Velocity On Flow Structure Around Bridge And Ship’s Force

Navigation safety is an important problem of riverway that has been very concerned and attention,With the boost of the 13 th Five-Year Plan and the rapid development of small and medium-sized cities,the number of bridge across the river is more and more big,the intensity is higher and higher,the increase of structures across a river reduced the area of effective water channel,the bridge navigable security problems will become more prominent.Via the gradually progressive study before,research the flow characteristics around the single and tandem piers without vessel,the coupling mechanism of single or tandem pier with the motion ship,and have a basic understanding of ship with different velocities through single pier along the stress distribution of the ship,and have no research on different velocity of single or double pier the turbulent flow characteristics around piers and force of the vessel.This paper uses the ships in different flow velocity in the process of the direct torque changes over time,at the same time analysis the mutual influence of ship and bridge,and set for safe distance under different velocity.Considering the mutual influence of water,bridge pier and ship motion,establish research ship motion and the bridge interaction of two dimensional turbulent flow mathematical model:(1)no ship case,research the influence of single flow around piers in different flow rate;(2)with the ship research the flow characteristics around the bridge pier under different velocity,and contrast with no ship analyze the influence of single flow around bridge piers in different flow;(3)when the ship sailing on the bridge area,research the evolution regularity of yawing moment in different flow rate;(4)research the tandem double bridge pier spacing sensitivity under different velocity.1.By the analysis of water flow around the single pier and yawing moment characteristics,the following conclusion:1).With the increasing of flow velocity,trailing vortex shedding core the transverse velocity value and influence range area are increase,in the wake flow wave amplitude increases,and has a linear relation between flow velocity and vortex value.2).In the scope of the v ≤3.5 m/s,St decreases as the speed,with the increase of flow velocity,free shear layer thickness increases before tumbling,cause of the trailing vortex shedding frequency and the St decrease.According to the change trend of St,when 1.5≤v≤2.0m/s,the flow structure has a great change;When 2.5≤v≤3.5m/s,the flow structure changed a little.Turbulence strongly area with the increase of flow velocity extended to the downstream of the bridge pier,and turbulence kinetic energy extending value increased gradually.3).In the process of ship motion force mainly comes from ship and bridge’s increase of velocity gradient and vortex considerate nearly.Under different flow velocity,fore yawing moment of ship evolution processes are similar,there are two peak value and a negative peak,peak torque of positions are not change,fore yawing moment of the most-positive and negative peak will increase as flow velocity increases gradually,the same position of peaks have no obvious linear relationship.2.Through the analysis of the impact on flow velocity around tandem double piers,the following conclusions:1).When L/D≤ 2.0,under different flow conditions,the upstream bridge piers product whirlpool,but did not form a vortex shedding,upstream bridge wake impact directly strike the downstream side walls of the piers.When L/D = 3.0,upstream and downstream bridge piers form trailing vortex shedding phenomenon,with the increase of flow velocity,the trailing vortex strength.Velocity rises and the vortex value have linear correlation.2).Comprehensive analysis the impact of velocity between the trailing vortex vortex and trailing vortex shedding value,under the different velocity,spacing for 2 ~ 3D has the biggest influence on tandem double bridge pier,when pier spacing is 5D,interference effect disappear,and is similar to a single bridge pier.3).From the safe navigation of ships,when v = 2.0 m/s,serial interference effect of double bridge piers has no influence on ship after the 8.0 ≤ L/D,because of the influence of the ship,tandem double bridge pier interference distance will be extended accordingly.