Hydraulic Performance of Flow over Normal and Inclined Compound Crested Weir Models

  • M. M. Muhammad
  • A. Ismail
  • J. A. Otun
  • D. B. Adie
  • S. B. Igboro
  • S. A. Abdullahi
Keywords: Laboratory flume, Compound crested weir, Angle of weir inclination, Hydraulic Performance, Flow Magnification Factor.


The overflow characteristics of Compound crested weir models were investigated experimentally using a laboratory flume. The crests of these weir models consist of two parts; the upstream part has a quarter round shape while the downstream part has standard sharp crested weir shape. Series of experiments were conducted by measuring discharges and water heads over the weir models for different weir crest radii of R = 2.5 cm, 3.5 cm, 4.5 cm and angles of weir inclination α = 300, 45°, 600 and 90° respectively to the direction of flow with a constant weir height P = 15 cm. It was observed that increase in the ratio of water head over the crest (h) to weir height (P) resulted in the corresponding increase in the discharge coefficient for all the weir models. The hydraulic performance for each of the weirs was determined in terms of the flow magnification factor. Hence, the model with R = 2.5 cm and α = 300 was selected as the best model because it had the highest discharge coefficient and flow magnification factor of 1.326 and 1.555 respectively.


Abid-Ali, H.S. (1986). Characteristics of Flow Over the Round Crested Weirs. M.Sc. Thesis. University of Basrah, Iraq.
Bhzad M. A. N and Tahssen A. H. C (2005). Characteristics of flow over Normal and Inclined weirs with Semicircular crests. Al_Rafidain Engineering Journal, 1 (13): 49 – 61.
Borghei, S. M., Vatannia, Z., Ghodsian, M., Jalili, M. R. (2003). Oblique Rectangular Sharp-Crested Weir. Water & Maritime Engineering 156, Issue WM2, pages 185- 191.
British Standard Institute (1965). Methods of Measurement of Liquid Flow in Open Channels. Part 4A, BS3680, BSI, London, England.
Chow, V.T. (1959). Open Channels Hydraulics. McGraw Hill Book Company. Inc., New York, N.Y.
Franzini, J. B. and Finnemore, E. J. (1997). Fluid Mechanics with Engineering Applications. McGraw-Hill Company Inc.
Ibrahim, Gh.M., Ibrahim, A.S. and Hassan, Y.M. (1988). Discharge and Flow Characteristics Over Inclined Weirs. Journal of Engineering and Technology. Proceeding of the Second Iraqi Conference Engineering. Special Issue, Pg 82.
Kabiri-Samani, A., Ansari, A. and Borghei, S. M. (2010). Hydraulic behaviour of flow over an oblique weir. Journal of Hydraulic Research,. 5 (48): 669-673.
Thair M. A. and Tahssen A. H. C. (2006). Hydraulic characteristics of flow over Compound crested weir. Al-Rafidain Journal of Engineering, 2 (14): 81 - 87