Numerical Simulation Of Local Scour Around A Pier Under Steady Current Condition

Local scour around piers has always been an important issue in the study of instability factors of piers.Scholars at home and abroad have done lots of research on the flow structure and local scour characteristics around the column,and achieved fruitful results.However,there is relatively little concern on the local scour of other structural types such as square column,rectangular column,especially the widely used round end column,open-hole column and compound column in water conservancy projects in recent years.Based on LES turbulence model and sediment scour module in FLOW-3 D software,a three-dimensional numerical simulation model of local scour round a cylinder under steady current condition is established in this paper.The characteristics of local scour morphological and the time-varying process of scour depth under steady current condition are studied.the research can enrich the existing research results of scour of piers and provide some references.for the design and construction of hydraulic structures in the future,which has very important practical significance.Firstly,each three-dimensional numerical model of local scour around square column,rectangular column,round end column and round end open-hole column under steady current condition is established respectively.Based on the numerical simulation results,the change characteristics of local scour hole around different column structure are studied,and the three-dimensional shape characteristics of local scour hole around different types of column in xy plane,longitudinal symmetry plane and transverse section are obtained.By comparing and analyzing the scouring depth of column,the differences of the scouring depth in the water-front side and the water-back side and the maximum scouring depth of piers with different structures are obtained.By comparing and analyzing the scouring depth of compound circular column with equal section column,compound round end column with equal section round end column,three stages of local scouring process of compound column are found,and different development stages were elaborated in detail.Secondly,based on the numerical model of local scour,the influencing factors of local scour are studied.By comparing and analyzing the development process of local scour hole around round end column under different Reynolds numbers(Re = 34000?75000),the influence of Reynolds number on the development rate of scour hole around round end column and the trend of local scour depth around round end column are obtained.Then,the local scour depth around round end column under different water depth(H = 1?4 times the effective diameter)is discussed.It is found that the influence of water depth on the local scour depth around round end column is weak under Re = 46000.Finally,based on the numerical model,the influence of the opening position on the scour depth around round end open-hole column is preliminarily discussed,and it is concluded that the local scour depth weakening effect is best when the opening position is at the surface of the sand bed.