Hydraulic Jet Control for River Junction Design of Yuen Long Bypass Floodway, Hong Kong
Publication: Journal of Hydraulic Engineering
Volume 134, Issue 1
Abstract
The Yuen Long Bypass Floodway (YLBF) was designed to collect flows from the Sham Chung River (SCR) and the San Hui Nullah (SHN) and to serve as a diversion channel of the Yuen Long Main Nullah (YLMN). Under a 200-year return period design condition, the floodway was designed (1) to divert a flow of approximately from the supercritical YLMN flow and (2) to convey a total combined flow of to downstream within acceptable flood levels. The success of the design depends critically on complicated junction flow interactions that cannot be resolved by 1D unsteady flow models. These features include the supercritical-subcritical flow transition at the San Hui-Floodway (SHN-YLBF) junction and the diversion of part of the supercritical flow from the Main Nullah (YLMN). A laboratory Froude scale physical model was constructed to study water stages and flow characteristics in the floodway and to investigate optimal design arrangements at channel junctions and transitions. This paper summarizes the main features of the unique river junction network, in particular the use of the hydraulic jet principle at the SHN-YLBF junction to lower flood levels. In addition, a numerical flow model is employed to study flow details at the river junctions. The model is based on the general 2D shallow water equations in strong conservation form. The equations are discretized using the total variation diminishing finite-volume method which captures the discontinuity in hydraulic jumps. The numerical model predictions are well supported by the laboratory data, and the theoretical and experimental results offer useful insights for the design of urban flood control schemes under tight space constraints.
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Acknowledgments
The first writer acknowledges Professor Brett Sanders for the useful numerical technique Prof. Sanders taught him during his tenure as a postdoc and for helpful discussions related to this application. The discussions with Ir W. C. Chan and G. Wilson on the YLBF project are gratefully acknowledged.
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Information
Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 1 • January 2008
Pages: 23 - 33
Copyright
© 2008 ASCE.
History
Received: Mar 23, 2006
Accepted: Jun 25, 2007
Published online: Jan 1, 2008
Published in print: Jan 2008
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