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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Scour measurement around a square obstacle with supercritical inflow
Scour measurement around a square obstacle with supercritical inflow
Author : THOMAS MOYNE, EMMANUEL MIGNOT & NICOLAS RIVIERE
ABSTRACT
Scour around obstacles has been deeply investigated for flows in subcritical regime and the originality of the present
work is to consider an inflow in supercritical regime, occurring in rivers with high slopes. The specificity of such flow is
that a detached hydraulic jump takes place in the near-surface region. The present work aims at understanding the
impact of such flow structure on the scour taking place around the obstacle in a mobile bed configuration. A specific
experimental flume was set-up with a mobile bed and water recirculation. At initial stage with no obstacle the flow is
uniform in supercritical regime, the Shields number is just below the critical one, thus the bed is stable and no sediment
motion takes place. The impervious obstacle is suddenly introduced and the flow and the bed become affected: the
hydraulic jump appears and the sediment starts to be eroded on the side and in front of the obstacle and to be deposited
downstream in the wake. The 2D fields of bed morphology and free-surface elevation are measured at specific times
using a specially developed measuring device. These measurements permit to understand and quantify the dynamics of
the bed and flow modifications: with time i) the hydraulic jump appears to slowly move towards the obstacle, ii) the
spatial extension and depth of the scour increase, iii) the spatial extension and elevation of deposition area behind the
obstacle increase. At final stage, after more than two hours of experiments, a specific bed morphology takes place.
File Size : 355,085 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 12/08/2015
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