TY - JOUR
T1 - Physical study of the 3-dimensional characteristics and free-surface properties of a breaking roller in bores and surges
AU - Wüthrich, Davide
AU - Shi, Rui
AU - Chanson, Hubert
PY - 2020/4/1
Y1 - 2020/4/1
N2 - Breaking surges and bores are observed during flood events, tidal bores and tsunamis propagating in rivers. The sudden increase in water depth generates an aerated and recirculating region, called the roller, whose turbulent behaviour is poorly understood. Based on ensemble-average analyses with multiple repetitions, this experimental work processed high-speed videos from multiple locations to characterise the spatial and temporal dynamics of the bore's roller. The results showed different air entrainment mechanisms for increasing Froude numbers, providing adapted formulae to predict the extension of the shear layer and the air-water boundary. Seen from above, the roller toe perimeter had an indented profile rapidly evolving in time, revealing a certain level of periodicity. A statistical analysis in terms of position of the roller toe, longitudinal fluctuations and instantaneous celerities allowed for a detailed characterisation of the turbulent surface fluctuations and three-dimensional properties of the breaking bore roller, leading to a better understating of the governing process.
AB - Breaking surges and bores are observed during flood events, tidal bores and tsunamis propagating in rivers. The sudden increase in water depth generates an aerated and recirculating region, called the roller, whose turbulent behaviour is poorly understood. Based on ensemble-average analyses with multiple repetitions, this experimental work processed high-speed videos from multiple locations to characterise the spatial and temporal dynamics of the bore's roller. The results showed different air entrainment mechanisms for increasing Froude numbers, providing adapted formulae to predict the extension of the shear layer and the air-water boundary. Seen from above, the roller toe perimeter had an indented profile rapidly evolving in time, revealing a certain level of periodicity. A statistical analysis in terms of position of the roller toe, longitudinal fluctuations and instantaneous celerities allowed for a detailed characterisation of the turbulent surface fluctuations and three-dimensional properties of the breaking bore roller, leading to a better understating of the governing process.
KW - Aeration
KW - Bore celerity
KW - Breaking bore
KW - Open channel
KW - Positive surge
KW - Roller toe
UR - http://www.scopus.com/inward/record.url?scp=85075739763&partnerID=8YFLogxK
U2 - 10.1016/j.expthermflusci.2019.109980
DO - 10.1016/j.expthermflusci.2019.109980
M3 - Article
AN - SCOPUS:85075739763
SN - 0894-1777
VL - 112
JO - Experimental Thermal and Fluid Science
JF - Experimental Thermal and Fluid Science
M1 - 109980
ER -