Influence Of Limnoperna Fouling On Hydraulic Characteristics Of Aqueduct Structure In Long-Distance Diversion Project

Limnoperna fouling is the phenomenon that some mussels(such as Limnoperna fortunei,etc.)attach to the water transport structure in high density,resulting in the deterioration of structural performance.Whether this phenomenon will affect the hydraulic characteristics of water transmission structure,and then affect the normal operation of the whole water diversion system,there is no systematic research conclusion.This paper USES the field investigation and model test and numerical simulation,the method of combining the based on site investigation for different aqueduct wall Limnoperna fortunei inspection image,using image recognition technology reveals the Limnoperna fortunei space distribution,on this basis,promotes the scale model test,explores the hydrodynamic performance of the aqueduct structure under different test conditions,At the same time,three dimensional numerical simulation technology was used to analyze the distribution law of velocity and finally revealed the influence law of Limnoperna fouling on the hydraulic characteristics of aqueduct structure.The main work contents and conclusions are as follows:(1)Study on the spatial distribution of Limnoperna fortunei.The inspection images of different aqueduct inner walls were obtained through field investigation,and the geometric characteristics and distribution rules of Limnoperna fortunei were obtained by image recognition technology.On this basis,scale model tests were carried out under different adhesion densities of Limnoperna fortune.The results showed as follows:1)The body length distribution and area proportion of Limnoperna fortunei obtained by automatic image recognition and field empting observation were basically consistent;2)The area proportion of Limnoperna fortunei per square meter on the side wall of aqueduct is in the range of 0.0137～0.07.(2)Study on the influence of Limnoperna fouling on the hydrodynamic performance of aqueduct structure.Through scale model tests,the variation of water depth,average velocity of section,roughness of aqueduct wall,vertical velocity,shear stress of wall and velocity of friction were analyzed under different adhesion densities.The results showed that wall roughness would increase significantly with the increase of adhesion density.When the density increased from 100ind/m~2 to 620ind/m~2,the maximum increment of wall roughness coefficient was more than 0.004,and when the adhesion density was more than 300ind/m~2,the change of wall roughness coefficient tended to be stable.The influence of Limnoperna fortunei attachment on the flow velocity was concentrated in the range of 0～0.111 in the aqueduct.(3)Study on the influence of Limnoperna fouling on aqueduct structure water carrying capacity.Three-dimensional numerical simulation was carried out based on the scale model to verify the feasibility of the numerical simulation method from two aspects of water surface line and velocity distribution.Finally,based on an aqueduct project,the influence of Limnoperna fouling on its water transport capacity under different adhesion thickness was studied.The results show that the wall roughness only affects the flow velocity near the wall surface,and has little effect on the flow velocity along the vertical line in the aqueduct.In the absence of Limnoperna fortunei attachment,the velocity distribution of aqueduct section is relatively uniform.With the increase of Limnoperna fortunei attachment density,the low-velocity area near the wall gradually expands,while the high-velocity area in the center becomes smaller and smaller,which means that the greater the density of Limnoperna fortunei attachment,the greater the impact on the aqueduct structure water transport capacity.