Numerical Simulation And Scour Prevention Of Flow Around Yuhong Bridge’s Double Cutwater Pier

The flow around piers is a very common phenomenon in life and engineering.In history,many small and medium size river-crossing bridges were built in the western Sichuan region centered on the Chengdu Plain according to the engineering experiences.Due to the requirements of construction technology,material acquisition,transportation,engineering quantities and beautiful shape,many of these Bridges piers is double cutwater piers.Up to now,most of these Bridges are old Bridges that have been in service for more than 30 years,and some of them have become historical relics.The study of the flow around the piers is beneficial to the analysis of the characteristics of the flow field around the piers.and also provides basic data for foundation scour protection of Yuhong Bridge and other cutwater pier bridges.This study is based on the double cutwater piers of Yuhong Bridge in Pujiang County,Chengdu City,and according to the basic equations of incompressible fluid flow.The flow around model pier under three conditions of low,medium and high water levels is numerically simulated.By visualization of the calculation results,the pressure,velocity and vector distribution of the flow field around the piers in different directions are obtained,and the qualitative characteristics and quantitative comparative analysis are carried out.The formation mechanism and development process of local scour of bridge piers are analyzed.Corresponding scour prevention and treatment suggestions are put forward according to the actual engineering situation of Yuhong Bridge.The results show that the double cutwater piers has excellent hydraulic characteristics,and the influence of the flow field around the pier is slight,which can better ensure the smooth and effective flow of the river.The flow field around the pier is relatively uniform in front of the pier,at the pier side,or at the pier wake field.There is no wake vortex street and the flow field has obvious layered distribution.In front of the piers,a circular low velocity zone appears at the top point of the cutwater,and a "horsetail" low velocity zone appears behind the pier.While the flow velocity at the pier side is higher,and the maximum flow velocity appears at the position of about 45° on both sides of the tail of front pier cutwater,showing a "petal-shaped" shape.The coincidence degree of wall shear distribution and velocity distribution is high coincidence rate.The flow field is the most complicated in high water level condition due to the different section forms.