Experimental And Numerical Simulation Of Longitudinal Bridge Flow Field In A Straight River Section Of Mountainous Area

Considering the ecological protection and other factors in the West Han Expressway,the longitudinal bridge plan is used in the mountainous areas along the river to replace the high fill embankment.Due to the large number of piers laid along the river,problems such as poor water flooding,severe foundation erosion,and pile abrasion have become a threat to the safety of the bridge foundation.Based on the longitudinal bridge of the Shunzhi section of the Xihan Expressway,this paper combines the indoor model test and the numerical simulation based on FLUENT software to study the characteristics of the flow field during the oblique crossing of the longitudinal bridge and the water flow in the straight section of the mountainous area,mainly for the pier group.When the water flow is at an angle of about 4°,when the double bridge piers with the spans of 0.52 m,0.8m,1.2m,1.6m and 2m are arranged in the test section,the longitudinal bridge flow field of the straight section of the mountainous area is studied.The main research results are as follows:(1)Through theoretical analysis and field investigation,the influence of various factors on the morphological characteristics of water flow is analyzed from the aspects of natural factors,river form,section shape,pier characteristics,pier group layout and the angle between the pier group and the water flow.(2)Through the indoor fixed bed model test,the characteristics of the flow field without piers are studied.The test results show that the flow field without piers appears parabolic in the test section.When the pier group exists,the direction of the water flow is changed,and the water flow is forced to move to the non-bridge pier area.At this time,the water flow between the right side wall and the first row of piers first increases and then decreases,and the left side wall and the fourth side.The flow velocity of the bridge piers tends to increase gradually.(3)Based on the angle of each working condition,it is close to 4°.Overall,the smaller the span of the pier,the more the number of rows of piers,the greater the variation of the water depth along the path.(4)According to the geometric scale,when the standard span of the bridge is 13 m,the influence between the pier groups is large,and the flow velocity between the piers is obviously changed.When the standard span of the bridge is 20 m,between the piers There is a certain degree of influence;when the standard span of the bridge is greater than 30 m,the mutual influence between the pier groups is almost non-existent and can be regarded as a single row of piers.(5)Through the comparison of the test and numerical simulation results,the three working conditions are in good agreement,and the simulation and experiment have obtained similar conclusions,indicating that the FLUENT software has good applicability and reliability to the longitudinal bridge flow field simulation and other issues.