Horizontal two-dimensional bed-load grain and water surface velocity fields in dam breach experiment
Date Issued
2015
Date
2015
Author(s)
Su, Yuan-Te
Abstract
Dam breaching consists of water flow and sediment transport. The connections between water and bed-load velocity and dam breach topography changes in downstream are the purpose in this study. Previous researches are devoted to observe dam breach phenomenon from side view. From top view, the flow field changed by terrain and the surface flow can be observed. A simplified laboratory experiment is conducted to obtain horizontal two dimensional velocity fields. In order to compare water surface and bed-load velocity, we use two different color and density particles to record water and bed-load motion synchronized. The particle tracking velocimetry (PTV) method is used to analyze velocity fields. The topography is acquired as Digital Elevation Model (DEM) using the software Photoscan, Agisoft. According to the DEM, the changing of topography can be discussed. The flow field can be projected to topography as 3 dimensional flow field. Using this approach, we successfully obtain both water surface velocities and bed-load velocities. We found that water surface velocity will affect the bed-load velocity. Besides, the topography have similar pattern to real dam breach events. Finally, the mass conservation can be used to estimate topography changing rate of bed-load if particles velocities are given.
Subjects
dam breaching
bed-load
water surface flow
particle tracking velocimetry
project
topography changing rate
Type
thesis
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