Study On Flow Characteristics Around Continuous Arrangement Of Pier

Turbulent flow width is an important research issues for determining navigateon conditions of brige and the width of building crossing river. Especially in recent years with the rapid developpment of transportation, the Channel level is rising more and more higher and many dense buildings across the river. It is In-evitably that an impact had producted on navigation safety. Althrough there are some experiments on the width of single-pier turbulent area, researches on mult-i-pier are few.Thus,it is essemial to study on the multi-pier turbulent width and reasonable calculation of bridge spans in order to take effective measures to prevent ship-crashing accidents.The characteristic and its width of the turbulence around the round-ended pier have been studied in this paper.Then use mathematical model to simulate the instantaneous flow field. With the condition that multi-pier are arranged along the flow direction Continuously, Disscusing the relevant hydraulic characteristics and the difference between single pier, analysis the diffirence of water flow around the pier structure and turbulence intensity between different spacing of the piers, the velocity and depth infront of the brige . The main conclusions are the following:(1) Periodic vortex shedding behind the pier is ne of the main factors that caused flow turbulence on both sides. Closer the vortex shedding area, turbulent indensity become bigger, and the smaller the time average velocity, fluctuating velocity probability density distribution curve is flat and the bigger the difference with the normal distribution. It explains that in turbulent region the turbulent indensity become more strength and the flow structure more disordering.(2) With the increase of velocity, turbulence intensity and width are increased accordingly. When L/D <6, with the spacing decreases, turbulence intensity and width behand the pier increase rapidly. When L/D>6, As the distance decreases, it's increase rate is smaller.(3) The point in which the turbulence intensity begins to increase is regarded as the critical point of turbulence width. The turbulence width is 0.5 ~ 1.0D when there is a single pier, and 1.0～2.5D when two piers. As for the mathematicalmodel results, it is regarded that the cross-sectional velocity behand the pier changes greater than 1cm/s as sphere of turbulent influence region, and finally Physical model test results are compared with good agreement.