Hydraulics of the developing flow region of stepped spillways. I: Physical modeling and boundary layer development

Zhang, Gangfu and Chanson, Hubert (2016) Hydraulics of the developing flow region of stepped spillways. I: Physical modeling and boundary layer development. Journal of Hydraulic Engineering, 142 7: . doi:10.1061/(ASCE)HY.1943-7900.0001138

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Author Zhang, Gangfu
Chanson, Hubert
Title Hydraulics of the developing flow region of stepped spillways. I: Physical modeling and boundary layer development
Journal name Journal of Hydraulic Engineering   Check publisher's open access policy
ISSN 0733-9429
1943-7900
Publication date 2016-07-01
Year available 2016
Sub-type Article (original research)
DOI 10.1061/(ASCE)HY.1943-7900.0001138
Open Access Status Not Open Access
Volume 142
Issue 7
Total pages 8
Place of publication Reston, United States
Publisher American Society of Civil Engineers
Language eng
Formatted abstract
On a stepped spillway, the steps act as macroroughness elements, contributing to enhanced energy dissipation and significant aeration. In a skimming flow, the upstream flow motion is nonaerated, and the free surface appears smooth and glossy up to the inception point of free-surface aeration. In this developing flow region, a turbulent boundary layer grows until the outer edge of the boundary layer interacts with the free surface and air entrainment takes place. The flow properties in the developing flow region were documented carefully in a large stepped spillway model (1V:1H; h=0.10  mh=0.10  m). The upstream flow was controlled by a broad-crested weir and critical flow conditions were observed along most of the weir crest, although the pressure distributions were not hydrostatic at the upstream and downstream ends. Downstream of the broad crest and upstream of the inception point, the free surface was smooth, although some significant free-surface curvature was observed for all discharges. The boundary layer growth was faster than on a smooth chute for identical flow conditions. The inception point of free-surface aeration was observed when the boundary layer thickness reached 80% of the flow depth: δ/di≈0.8. The location of the inception point of free-surface aeration and the flow depth at inception were compared successfully to previous laboratory and prototype results.
Keyword Stepped spillways
Developing flow region
Developing boundary layer
Inception point of free-surface aeration
Physical modelling
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
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Citation counts: TR Web of Science Citation Count  Cited 3 times in Thomson Reuters Web of Science Article | Citations
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Created: Thu, 16 Jun 2016, 22:28:13 EST by Hubert Chanson on behalf of School of Civil Engineering