Modeling Study of Free Overfall in a Rectangular Channel with Strip Roughness
Publication: Journal of Hydraulic Engineering
Volume 134, Issue 5
Abstract
Results from combined laboratory experimental and turbulent numerical modeling studies are presented to investigate the effects of bed roughness (discrete square strips) and slope on the flow over a free overfall in a rectangular channel. A broad range of model parameters such as the bed roughness, channel slope, and incoming upstream Froude number is investigated. The water surface profiles upstream of the brink of the channel, the velocity fields in cavity between two strips, and end depth (water depth at the brink of the channel) are simulated, measured, and discussed for various input conditions. The results show that for a given dimension of bed roughness the relative spacing of roughness (defined as the ratio of the center to center distance to the height of the strip) has a significant effect on the flow. The computational results are in good agreement with the experimental measurements.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The writers are grateful for the support of this work by the National Natural Science Foundation of China (Grant No. NNSFC50579025), the National Basic Research (973) Program of China (Grant No. UNSPECIFIED2005CB724202), and Carnegie Trust for the Universities of Scotland. The discussions with Professor V. Nikora, Dr. L Campbell and Dr. Pokrajac are acknowledged. The constructive comments and suggestions made by three anonymous reviewers, the associate editor, and editor greatly improved the quality of the technical node.
References
Campbell, L. (2005). “Double-averaged open-channel flow over regular rough beds.” Ph.D. thesis, Univ. of Aberdeen, Aberdeen, U.K.
Clarke, N. S. (1965). “On the two-dimensional inviscid flow in a waterfall.” J. Fluid Mech., 22(II), 359–369.
Davis, A. C., Ellett, B. G. S., and Jacob, R. P. (1998). “Flow measurement in sloping channels with rectangular free overfall.” J. Hydraul. Eng., 124(7), 760–763.
Delleur, J. W., Dooge, J. C., and Gent, K. W. (1956). “Influence of slope and roughness on the overfall.” J. Hydr. Div., 82(4), 1038/30–35.
Dey, S. (1998). “Free overfall in rough rectangular channels: A computational approach.” Proc. Inst. Civ. Eng., Waters. Maritime Energ., 130(3), 51–54.
Dey, S. (2000). “End depth in steeply sloping rough rectangular channels.” Proc., Engineering Sciences, Vol. 25, Indian Academy of Sciences, Sadhana, India, 1–10.
Dey, S. (2002). “Free overfall in open channel: State-of-the-art review.” Flow Meas. Instrum., 13, 247–264.
Ferziger, J. H., and Perić, M. (1999). Computational methods for fluid dynamics, 2nd Ed., Springer, Berlin.
Guo, Y. K. (2005). “Numerical modeling of free overfall.” J. Hydraul. Eng., 131(2), 134–138.
Hager, W. H. (1983). “Hydraulics of plane free overfall.” J. Hydraul. Eng., 109(12), 1683–1697.
Khan, A. A., and Steffler, P. M. (1996). “Modeling overfalls using vertically averaged and momentum equations.” J. Hydraul. Eng., 122(7), 397–402.
Knight, D., and MacDonald, J. A. (1979). “Hydraulic resistance of artificial strip roughness.” J. Hydr. Div., 105(6), 675–690.
Kraijenhoff, D. A., and Dommerholt, A. (1977). “Brink depth method in rectangular channel.” J. Irrig. and Drain. Div., 103(2), 171–177.
Marchi, E. (1993). “On the free overfall.” J. Hydraul. Res., 31(6), 777–790.
Naghdi, P. M., and Rubin, M. B. (1981). “On inviscid flow in a waterfall.” J. Fluid Mech., 103, 375–387.
Perry, A. E., Schofield, W. H., and Joubert, P. N. (1969). “Rough wall turbulent boundary layers.” J. Fluid Mech., 37(2), 383–413.
Rajaratnam, N., and Muralidhar, D. (1968). “Characteristics of the rectangular free overfall.” J. Hydraul. Res., 6(3), 233–258.
Rajaratnam, N., Muralidhar, D., and Beltaos, S. (1976). “Roughness effects on rectangular free overfall.” J. Hydr. Div., 102(5), 599–614.
Raju, K. G. R., and Garde, R. J. (1970). “Resistance to flow over two-dimensional strip roughness.” J. Hydr. Div., 96(3), 815–834.
Rodi, W. (1993). Turbulence models and their application in hydraulics: A state-of-the-art review, 3rd Ed., Balkema, Rotterdam, The Netherlands.
Rouse, H. (1936). “Discharge characteristics of the free overfall.” Civ. Eng. (N.Y.), 6(4), 257–260.
Southwell, R., and Vaisey, G. (1946). “Relaxation methods applied to engineering problems. XII. Fluid motions characterized by ‘free’ streamline.” Philos. Trans. R. Soc. London, Ser. A, 240, 117–161.
Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 5 • May 2008
Pages: 664 - 667
Copyright
© 2008 ASCE.
History
Received: May 22, 2006
Accepted: Apr 9, 2007
Published online: May 1, 2008
Published in print: May 2008
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.