Junction and Drop-Shaft Boundary Conditions for Modeling Free-Surface, Pressurized, and Mixed Free-Surface Pressurized Transient Flows
Publication: Journal of Hydraulic Engineering
Volume 136, Issue 10
Abstract
A junction and drop-shaft boundary conditions (BCs) for one-dimensional modeling of transient flows in single-phase conditions (pure liquid) are formulated, implemented and their accuracy are evaluated using two computational fluid dynamics (CFD) models. The BCs are formulated in the case when mixed flows are simulated using two sets of governing equations, the Saint-Venant equations for the free-surface regions and the compressible water hammer equations for the pressurized regions. The proposed BCs handle all possible flow regimes and their combinations. The flow in each pipe can range from free surface to pressurized flow and the water depth at the junction or drop shaft can take on all possible levels. The BCs are applied to the following three cases: (1) a three-way merging flow; (2) a three-way dividing flow; and (3) a drop shaft connected to a single-horizontal pipe subjected to a rapid variation of the water surface level in the drop shaft. The flow regime for the first two cases range from free surface to pressurized flows, while for the third case, the flow regime is pure pressurized flow. For the third case, laboratory results as well as CFD results were used for evaluating its accuracy. The results suggest that the junction and drop-shaft BCs can be used for modeling transient free-surface, pressurized, and mixed flow conditions with good accuracy.
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Acknowledgments
This work was conducted at the University of Illinois at Urbana-Champaign as part of the studies for the Tunnel and Reservoir Plan (TARP) Modeling Project in Chicago, Illinois. The writers gratefully acknowledge the Metropolitan Water Reclamation District of Greater Chicago for their financial support. The third writer wishes to acknowledge the Hong Kong Research Grant Council Project No. UNSPECIFIED613407. Special thanks to MSc. Andrew Waratuke and Dr. Octavio Sequeiros for their assistance on the experimental work and to Engineer Nils Oberg for his assistance on the video image processing analysis. Last but not least, our special thanks to the anonymous manuscript reviewers for their insightful comments and suggestions.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 136 • Issue 10 • October 2010
Pages: 705 - 715
Copyright
© 2010 ASCE.
History
Received: Feb 26, 2009
Accepted: Mar 27, 2010
Published online: Mar 30, 2010
Published in print: Oct 2010
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