Effect of Crest Roughness on Flow Characteristics over Circular Weirs

Document Type : Research Papers

Authors

1 Hydraulic Structures

2 Water Resource Engineering

3 Young Researchers Club, Kermanshah Branch, Islamic Azad University

4 Water Civil Engineering

Abstract

Different construction materials with different roughness used to make circular weirs highly affect surface roughness and, in turn, flow hydraulics passing over these structures.  In the present research, numerous experiments under different hydraulic conditions were performed on a physical model to study the effects of roughness on flow hydraulics over a circular weir. The flow hydraulics included velocity profile, discharge coefficient and longitudinal water surface profile. The actual water surface elevation and velocity profile at different cross sections were measured using a point gauge and micro current meter, respectively. About 200 experimental tests were performed on a circular weir made of polyethylene with 29.5 cm height, 30cm wide, and 7.5 cm radius. The results showed that for a constant discharge, as the weir surface roughness increases the upstream water level over the weir increases and the discharge coefficient reduces. The velocity profile at upstream sections of the weir crest is extremely different from that over the weir crest while the velocity profile at downstream sections of the weir crest follows the same pattern as those experienced at the weir crest. Also, the increased roughness makes the velocity profile over the weir more uniform, with a higher average velocity. Finally the effects of roughness on velocity values are less near weir in comparison with water surface.

Keywords

References

Bazin, H. (1898). “Recent experiments on the flow of water over weirs”, Mémoireset Documents, Annales des Ponts et Chaussées, Paris, France, Sér. 7, 15, 2nd Sem, 151-264.
Chanson, H. and Montes, J.S. (1998). “Overflow characteristics of circular weir: effect of inflow conditions”, Journal of Irrigation and Drainage Engineering, ASCE, 124(3), 152-162.
Creager, W.P. (1917). Engineering of masonry dams, John Wiley and Sons, New York, USA.
Escande, L. and Sananes, F. (1959). “Etudes des Seuils Déversants à Fente Aspiratrice. ('Weirs with suction slots.')”, Journal La Houille Blanche, Dec., No. Special B, 892-902 (in French).
Esmaili, K., Naghavi, B., KouroshVahid, F. and Yazdi, J. (2010). “Experimental and numerical modeling of flow pattern on circular weir”, Journal of Water and Soil, 24(1), 166-179.
Fawer, C. (1937). “Etude de quelques ecoulements permanents a filets courbes (Study of some steady flows with curved streamlines)”, Thesis, Lausanne, Switzerland, Imprimerie La Concorde (in French).
Heidarpour, M., Afzalimehr, H. and Khorami, E. (2002). “Applied of flow function around cylindrical weir crest”, Journal of Technical and Natural Resource, 6(3), 51-61.
Heidarpour, M., Chamani, M.R. and Khorami, E. (2006). “Characteristics of circular-crested and cylindrical weirs”, Journal of Agriculture Science and Natural Resource, 12(6), 21-30
Othman, Kh.I., Tahsen, A.Ch. and Ibrahim, A.I.Al-H. (2010). “Effect of size and surface roughness of cylindrical weirs on overflow characteristics”, Al-Rafidian Engineering Journal, 19(2), 77-89.
Ramamurthy, A.S. and VO, N.D. (1993). “Characteristics of circular crested weir”, Journal of Hydraulic Engineering. ASCE, 119(9), 1055-1063.
Raupach, M.R., Antonia, R.A. and Rajagopalan, S. (1991). “Rough-wall turbulent boundary layers”, Applied Mechanics Reviews, 44(1), 1-25
Rehbok, T. (1929). “The river hydraulic laboratory of the Technical University of Karlsruhe, hydraulic laboratory practice”, ASME, New York, N.Y, 111-242.
Rouve, G. and Indlekofer, H. (1974). “Discharge over Straight Weirs with Semi cylindrical Crest”, Der Bauinge nieur, 49(7), 250-256, (in Germany).
Sarginson, E.J. (1972). “The influence of surface tension on weir flow”, Hydraulic Research Delft, The Netherlands, 10(4), 431-446.
Tahmassebii, S. (2010). “Experimental Study of effect of weir crest roughness on separation region in broad crested weir”, MSc. Thesis, University of Shahid Chamran, Ahvaz, Iran.
Civil Engineering Infrastructures Journal
Volume 46, Issue 2 - Serial Number 2
December 2013
Pages 199-207

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History

  • Receive Date: 16 May 2012
  • Revise Date: 11 November 2012
  • Accept Date: 25 May 2013

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