scholarly journals Temporal and Spatial Flow Variations over a Movable Scour Hole Downstream of a Grade-Control Structure with a PIV System

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1002 ◽  
Author(s):  
Shi-Yan Lu ◽  
Jau-Yau Lu ◽  
Dong-Sin Shih
Keyword(s):  
Turbulent Flow ◽  
Diffusion Region ◽  
Control Structures ◽  
Intensity Measurements ◽  
Scour Hole ◽  
Sophisticated Equipment ◽  
Grade Control ◽  
Scour Holes ◽  
Scouring Process ◽  
Temporal And Spatial

Weirs or grade-control structures (GCSs) are frequently adopted to protect bridges or control riverbed degradation. Scour holes may develop downstream of these hydraulic structures. Laboratory experiments have been performed in this study, using sophisticated equipment and newly developed procedures. The purpose was to investigate important characteristics of the turbulent flow in the movable scour hole. The results of these experiments demonstrated the significance of instantaneous shear stress in the scouring process. The measured Reynolds stress can be fitted with the theoretical equation reasonably well. Furthermore, the results revealed that the normalized mean vertical velocity profiles in the diffusion region of the scour hole can be fitted with a Gaussian curve. An analysis of the turbulence intensity measurements showed that the turbulent flow is anisotropic in the scour hole. The turbulence intensities also decreased with time as the scour hole gradually approached equilibrium.

Simulation of Open Channel Turbulent Flow Over Bridge Decks and Formation of Scour Hole Beneath the Bridge Under Flooding Conditions

2009 ◽  
Author(s):  
Bishwadipa Adhikary ◽  
Pradip Majumdar ◽  
Milivoje Kostic ◽  
Steven A. Lottes
Keyword(s):  
Shear Stress ◽  
Turbulent Flow ◽  
Open Channel ◽  
Moving Boundary ◽  
Bridge Decks ◽  
Critical Shear Stress ◽  
Navier Stokes ◽  
Scour Hole ◽  
Scour Holes ◽  
Bed Roughness

This study is focused on the simulation of open channel turbulent flow over flooded laboratory scale bridge decks and formation of scour holes under various flooding conditions. Solutions for turbulent flow field are based on Reynolds Averaged Navier-Stokes (RANS) equations and turbulence closure models using the STAR-CD commercial computational fluid dynamics (CFD) software. An iterative computational methodology is developed for predicting equilibrium scour profiles using the single-phase flow model with a moving boundary formulation. The methodology relies on an empirical correlation for critical bed shear stress that is used to characterize the condition for onset of sediment motion and an effective bed roughness that is a function of sediment particle size. The computational model and iterative methodology were stable and converged to an equilibrium scour hole shape and size that compares reasonably well with experiment using a constant critical shear stress value.

Evolution of scouring process downstream of grade-control structures under steady and unsteady flows

2012 ◽  
Vol 27 (19) ◽  
pp. 2699-2709 ◽  
Author(s):  
Jau-Yau Lu ◽  
Jian-Hao Hong ◽  
Kai-Po Chang ◽  
Tai-Fang Lu
Keyword(s):  
Unsteady Flows ◽  
Control Structures ◽  
Grade Control ◽  
Scouring Process ◽  
Steady And Unsteady Flows

scholarly journals Evolution of Hydrodynamic Characteristics with Scour Hole Developing around a Pile Group

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1632 ◽  
Author(s):  
Yilin Yang ◽  
Meilan Qi ◽  
Jinzhao Li ◽  
Xiaodong Ma
Keyword(s):  
Flow Field ◽  
Turbulence Intensity ◽  
Large Scale ◽  
Pile Group ◽  
Horseshoe Vortex ◽  
Hydrodynamic Characteristics ◽  
Small Scale ◽  
Scour Hole ◽  
Scour Holes ◽  
Scouring Process

This study concerns the evolution of flow field and hydrodynamic characteristics within the developing scour hole around a four-pile group with 2 × 2 arrangement. The instantaneous velocities in scour holes at four typical stages during the scouring process were measured by an acoustic Doppler velocimeter (ADV). The evolution and spatial distribution of the time-averaged flow field, turbulence, and the corresponding hydrodynamic characteristics within scour holes were compared. The time-averaged flow field shows that the reverse flow, downward flow, and horseshoe vortex are formed in the upstream of the pile group. During the scouring process, the mean components of flow characteristics (i.e., mean velocity, vorticity, and bed shear stress) around the pile group decrease while the fluctuating components (i.e., turbulence intensity) intensify simultaneously. Similarity of turbulence intensity profiles was found within different scour holes. The horseshoe vortex at upstream of each pile merges and the shear layer in the gap region extends when the dimension of the scour hole increases to that of equilibrium scour status, indicating that the four piles behave more like a single bluff body. With the development of scour holes, the large-scale horseshoe vortex system becomes more stable and the dissipation of small-scale eddies becomes more significant.

scholarly journals Secondary Currents with Scour Hole at Grade Control Structures

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 319
Author(s):  
Mouldi Ben Meftah ◽  
Diana De Padova ◽  
Francesca De Serio ◽  
Michele Mossa
Keyword(s):  
Secondary Flow ◽  
Control Structure ◽  
Scour Depth ◽  
Control Structures ◽  
Secondary Currents ◽  
Scour Hole ◽  
Grade Control ◽  
Flow Motion ◽  
The Cross ◽  
Equilibrium Scour Depth

Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of flow velocities in clear water scours downstream of a grade control structure in a channel with non-cohesive sediments, in this study, we attempted to investigate the generation and turbulence properties of secondary currents across a scour hole at equilibrium condition. The flow velocity distributions through the cross-sectional planes at the downstream location of the maximum equilibrium scour depth clearly show the development of secondary current cells. The secondary currents form a sort of helical-like motion, occurring in both halves of the cross-section in an axisymmetric fashion. A detailed analysis of the turbulence intensities and Reynolds shear stresses was carried out and compared with previous studies. The results highlight considerable spatial heterogeneities of flow turbulence. The anisotropy term of normal stresses dominates the secondary shear stress, giving the impression of its crucial role in generating secondary flow motion across the scour hole. The anisotropy term shows maximum values near both the scour mouth and the scour bed, caused, respectively, by the grade control structure and the sediment ridge formation, which play fundamental roles in maintaining and enhancing the secondary flow motion.

scholarly journals Scour Downstream of Grade‐Control Structures

1991 ◽  
Vol 117 (5) ◽  
pp. 579-594 ◽  
Author(s):  
Noel E. Bormann ◽  
Pierre Y. Julien
Keyword(s):  
Control Structures ◽  
Grade Control

Equilibrium Scour Downstream of Three-Dimensional Grade-Control Structures

2012 ◽  
Vol 138 (2) ◽  
pp. 167-176 ◽  
Author(s):  
S. Michael Scurlock ◽  
Christopher I. Thornton ◽  
Steven R. Abt
Keyword(s):  
Three Dimensional ◽  
Control Structures ◽  
Grade Control
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