3D Numerical Study of the Flow Properties in a Double-Spur Dikes Field during a Flood Process

Xun Han,Pengzhi Lin

doi:10.3390/w10111574

Abstract

A 3D numerical model is developed to study the flow characteristics of a double-spur dikes field on Yangtze River during a flood process, which was presented by the variation of the flow condition. The model is based on Navier–Stokes (NS) equations, the porous medium method (PMM) is employed to treat the solid structures including the river bed surface, the volume of fluid (VOF) method is applied to track the motion of the water surface during the flood process, and large eddy simulation (LES) is adopted to capture the turbulence transport and dissipation. Using this model, the target reach’s flow field before the construction of double-spur dikes is simulated first, while the numerical results are compared to the field measurements on flow velocity and water surface level, and fairly good agreements are shown. Then, the model is applied to reproduce the hydrodynamic evolution during a flood process after double-spur dikes’ constructions, while the detailed 3D flow fields are obtained under some certain states with different submergence rates of the spur dikes; finally, the potential damage positions around these spur dikes are analyzed accordingly.

Highlights

Spur dikes are one of the commonly used hydraulic structures in river engineering
The constructions of spur dikes in navigable waterways will inevitably lead to the change of main flow patterns by narrowing the river width and increasing water depth, and the local area close to the hydraulic structures, at which the flow separation and circumfluence result in strong 3D
We introduced the model firstly, and presented verification against field measurement of the target river reach before the double-spur dikes’ construction, afterwards, this model was applied to investigate the flow characteristics after the construction of double-spur dikes, in which the detailed 3D flow fields during their submergence processes along with the increasing water levels were obtained, while the potential damage positions around these spur dikes were analyzed for engineering purposes

Summary

Introduction

Spur dikes ( known as groynes) are one of the commonly used hydraulic structures in river engineering. The importance of the research on local flow field around spur dikes is significant, either to the development of fundamental hydrodynamic theory, or to the actual design and construction of river navigation, scour prevention and ecosystem preservation projects. The constructions of spur dikes in navigable waterways will inevitably lead to the change of main flow patterns by narrowing the river width and increasing water depth, and the local area close to the hydraulic structures, at which the flow separation and circumfluence result in strong 3D turbulence, while the pressure distribution is non-hydrostatic. When submergence occurs during a flood process, the river stage continues increasing until the spur dikes’ tops are submerged under the water surface

Methods

Discussion

Conclusion