Impact of Vertically Constricted Entrance on Hydraulic Characteristics of Vertical Drop (Numerical Investigation)

Document Type : Technical Note


1 University of Zanjan, Zanjan, 45371 - 38791, Iran

2 Department of Civil Engneering, Faculty of Engneering, University Of Maragheh, Iran

3 Department of Civil Engg., University of Zanjan


Vertical drops are used in irrigation and drainage networks and surface run-off collection channels. In
the present study, the impact of vertically constricted entrance on hydraulic characteristics of drops is
numerically study utilizing FLOW-3D®. In the first step, for choosing the best model of turbulence,
two types of turbulence models k -e and RNGk -e were used. In the next step, four constriction
layouts of S/H=0.312, 0.500, 0.875, 2 (ratio of constriction distances to drop height) were utilized as
long as the case without any constriction. The results showed that the RNGk -e turbulence model has
less relative error percentage and RMSE in comparison with k -e model and more efficiency to
simulate hydraulic characteristics on drops. Based on the obtained results, it was observed that the
vertically constricted entrance would result in decreasing the relative depth of water in the pool, the
depth of downstream water and normal residual energy by 42.31%, 47.23%, and 23.59%, respectively.
Presence of entrance constriction results in increasing the velocity at drop edge and thus the kinetic
energy decreases by flow turbulence increment caused by divided jet falls and production of more airwater
mixing region. Some relations are proposed to calculate pond depth ratio, downstream depth
ratio and normal residual energy with acceptable correlation coefficients which are in accordance with
those of other researchers.


تربن، س.ع.، و مشکاتی، س.م.ه.  (1393). "شبیه­سازی عددی اثرات هیدرولیکی شیب­شکن قائم در یک کانال مستطیلی". دو فصلنامه علمی تخصصی مهندسی آب، (3)1، ص‌ص. 55-66.
تقی­زاده، ح.، و صالحی نیشابوری، ع.ا. (1393). "بررسی عددی الگوی رفتاری جریان روی سرریزهای سه جانبی"، مجله پژوهش آب ایران، (8)14، ص‌ص. 211-215.
کاتورانی، س.، و کاشفی­پور، س.م. (1392). "اثر مشخصات هندسی مانع و شیب کف دراپ روی شرایط هیدرولیکی جریان در دراپ­های مانع­دار"، مجله علوم و مهندسی آبیاری، 37(2)، ص‌ص. 51-59.
Bakhmeteff, M.W. (1932). "Hydraulics of open channels". New York and London, McGraw-Hill book company, Inc.
Chamani, M., and Beirami, M. K. (2002). "Flow characteristics at drops". Journal of Hydraulic Engineering, 128(8), 788-791.
Chamani, M. R., Rajaratnam, N., and Beirami, M. K. (2008). "Turbulent jet energy dissipation at vertical drops". Journal of hydraulic engineering, 134(10), 1532-1535.
Chanson, H. (1994).  "Hydraulics of nappe flow regime above stepped chutes and spillways". Australian Civil Engineering Transactions, IEAust, 36(1), 69-76.
Daneshfaraz, R., Joudi, A. R., Ghahramanzadeh, A., and Ghaderi, A. (2016). "Investigation of flow  pressure  distribution  over  a  stepped  spillway", Advances  and  Applications  in  Fluid 334 Mechanics, 19(4), 811.
Daneshfaraz, R., Ghahramanzadeh, A., Ghaderi, A., Joudi, A. R., and Abraham, J. (2016). "Investigation of the Effect of Edge Shape on Characteristics of Flow under Vertical Gates". Journal‐American Water Works Association, 108(8), 425-432.
Daneshfaraz, R., and Ghaderi, A. (2017). "Numerical Investigation of Inverse Curvature Ogee Spillway", Civil Engineering Journal, 3(11), 1146-1156.
Esen, I. I., Alhumoud, J. M., and Hannan, K. A. (2004). "Energy Loss at a Drop Structure with a Step at the Base". Water international, 29(4), 523-529.
Farouk, M., and Elgamal, M. (2012). "Investigation of the performance of single and multi-drop hydraulic structures."International Journal of Hydrology Science and Technology, 2(1), 48-74.
Gill, M. A. (1979). "Hydraulics of Rectangular Vertical Drop Structures". Journal of Hydraulic Research, 17(4), 289-302.
Grant, D.M. and Dawson, B.D. (1998). "Open Channel Flow Measurement Handbook". 5th ed. ISCO Inc.
Hong, Y. M., Huang, H. S., and Wan, S. (2010). "Drop characteristics of free-falling nappe for aerated straight-drop spillway". Journal of Hydraulic Research, 48(1), 125-129.
Kabiri-Samani, A. R., Bakhshian, E., and Chamani, M. R. (2017). "Flow characteristics of grid drop-type dissipators". Flow Measurement and Instrumentation, 54, 298-306.
Liu, S. I., Chen, J. Y., Hong, Y. M., Huang, H. S., and Raikar, R. V. (2014). "Impact Characteristics of Free Over-Fall in Pool Zone with Upstream Bed Slope". Journal of Marine Science and Technology, 22(4), 476-486.
Lin, C., Hwung, W. Y., Hsieh, S. C., and Chang, K. A. (2007). "Experimental study on mean velocity characteristics of flow over vertical drop."Journal of Hydraulic Research, 45(1), 33-42.
Moore, W. L. (1943). "Energy loss at the base of a free overfall". Transactions of the American Society of Civil Engineers, 108(1), 1343-1360.
Moghaddam, M.A.A. (1999). "Modified theory for rectangular vertical drop structures". Unpublished report.
Mansouri,R., and Ziaei, A.N. (2014). "Numerical modeling of the flow in the vertical drop with inverse apron". 11th International Conference on Hydroinformatics, New York City, USA.
Rouse, H. (1936). "Discharge characteristics of the free overfall: Use of crest section as a control provides easy means of measuring discharge". Civil Engineering, 6(4), 257-260.
Rand, W. (1955). "Flow geometry at straight drop spillways". In Proceedings of the American Society of Civil Engineers, 81(9), 1-13.
Rajaratnam, N. and Chamani, M. R. (1995). "Energy Loss at Drops". Journal of Hydraulic Research, 33(3), 373-384.
Simsek, O., Akoz, M.S. and Soydan, N.G. (2016). "Numerical validation of open channel flow over a curvilinear broad-crested weir", Progress in Computational Fluid Dynamics, an International Journal, Vol. 16, No. 6, pp. 364-378.
USBR. (2001). "Water Measurement Manual". 3rd ed., US Government Printing Office Washington DC.
Versteeg, H. K., and Malalasekera, W. (2007). "An introduction to computational fluid dynamics: the finite volume method". Pearson Education.
White, M.P. (1943). "Discussion of Moore (1943)". ASCE, 108, 1361-1364.
Wu, S. and Rajaratnam, N. (1997). "Impinging Jet and Surface Fiow Regimes at Drops". Journal of Hydraulic Engineering, 36(1), 69-74.
Zahabi, H., Torabi, M., Alamatian, E., Bahiraei, M., and Goodarzi, M. (2018). "Effects of Geometry and Hydraulic Characteristics of Shallow Reservoirs on Sediment Entrapment". Water, 10(12), 1725.