Large-eddy simulation study of turbulent flow around a rectangular spur dike

Seokkoo Kang,A Paquier,N Rivière

doi:10.1051/e3sconf/20184005013

Abstract

High-resolution large-eddy simulation (LES) is carried out for investigating three-dimensional flow fields around a rectangular spur dike installed in an open-channel flume. The LES showed good agreement with the measurement obtained using Acoustic Doppler Velocimetry. Analysis of the LES result shows that the flow structure around and in the wake of the spur dike is highly complex and three-dimensional. Namely, flow upstream of the spur dike is featured by a vortex system near the bed, another vortex system beneath the free surface, and a recirculation region in front of the spur dike. All of these flow structures are laterally oriented. Moreover, flow in the wake region consists of a large vertically oriented recirculation region and a smaller laterally oriented recirculation region near the bottom corner downstream of the spur dike.

Highlights

One of the widely used approaches for restoring a stream from the point view of fluvial hydraulics and geomorphology has been the installation of instream structures near the streambank, in such a way that they alter the flow and sediment transport processes to improve water quality, to increase biodiversity, to enhance fish habitat, or to improve channel and bank stability
Many of the early studies on this structure have focused on the observation of scour and deposition patterns instream structures, but recent studies have been directed toward understanding the turbulent flow characteristics and three-dimensional flow fields using laboratory experiments or numerical simulations
A number of experimental studies have been conducted for measuring mean velocities and turbulence statistics around a spur dike using Acoustic Doppler Velocimetry (ADV) [9, 10] or Particle Image Velocimetry (PIV) [11]

Summary

Introduction

One of the widely used approaches for restoring a stream from the point view of fluvial hydraulics and geomorphology has been the installation of instream structures near the streambank, in such a way that they alter the flow and sediment transport processes to improve water quality, to increase biodiversity, to enhance fish habitat, or to improve channel and bank stability. Most of the previous experimental studies failed to present the detailed structure of three-dimensional velocity fields and associated turbulence statistics in both near and far wakes. This kind of experiment has been conducted only recently by Jeon et al [12] They investigated the flow around a spur dike installed in a laboratory flume by measuring the three-dimensional velocity field and free surface elevations in the whole of the recirculation region that is formed downstream of the spur dike. This study, as the continuation of the research performed by Jeon et al [12], aims to further elucidate the structure of the threedimensional flow fields around and in the whole wake of the spur dike and their associated turbulence characteristics by investigating the same flow configuration using numerical simulation

Computational model

Description of flow problem

Computational details

LES results

Summary and conclusions