Experimental Investigation of non-suppressed sill effect with different geometry on flow pattern and discharge coefficient of sluice

Document Type : Research Article


1 Professor of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.

2 Ph.D, Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran

3 M.sc student, Department of civil engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran.


Introduction: The ease of installing sluice gates and simplicity of their equations resulted in sluice gates as one of the most widely used hydraulic structures in regulating and controlling the water level. Several factors are discussed on the discharge coefficient of the sluice gate, including the effect of sill under the gate. The most important application of sill under sluice gate is to increase its discharge coefficient. Geometry and widths of sill is one of the important factors on discharge coefficient. also use of non-suppressed sills changes the flow pattern and the general equation of discharge coefficient. discharge coefficient of sluice gate with sill was studied by Jalil et al. (2016). In this study, the effect of sill under sluice gate was experimentally investigated on flow discharge coefficient. Results showed that the coefficient of discharge decreases with an increase of relative sill height to the head upstream. Rezavand (2018) investigated the effects of the hydraulic parameters on the flow discharge coefficient by Fluent software. Results showed that the sill under the gate has a positive effect on the flow discharge coefficient. The goal of this study is to investigate the geometry of sill with changes in its width on flow pattern and discharge coefficient in free-flow conditions. According to previous studies effect of sill width parameter with different geometric shapes on discharge coefficient and flow pattern has not been studied.
Methodology: The experiments were performed in a hydraulic laboratory with flume dimensions of 5 m in length, 0.30 m in width, and 0.45 m in height. The walls are made from Plexiglass in order to provide good visibility. The inlet flow were measured by two rotameters with± 2% accuracy. Rotameters were installed at the outlet of the pump and measured with a point gage with an accuracy of 1 mm. a sluice gate with a 1 cm thickness is installed with the distance of 1.5 m away from the inlet of flow. The gate opening was fixed at 4 cm in all experiments. Sills including cylindrical, semicylindrical, pyramidal, and rectangular cubic were prepared in order to investigate the shape effect. All four sill shapes were prepared with widths of 5, 7.5, 10, 15, and 20 cm in order to study the effect of sill width under the gate. The height of all sills in this study was considered to be a fixed value of 3 cm. A total of 20 physical models were tested. In this study, flow discharge in the range of 475 to 700 liters per minute was applied to all models. A total of 200 experiments were performed in order to investigate the effect of sill shape and width on flow pattern and discharge coefficient in free conditions.
Results and Discussion: Results of sluice gate patterns with sill and without sill situations were investigated. The results of these experiments, similar to previous studies, show that a sluice gate with sill increases the discharge coefficient. The results showed that sills with different geometries affect flow under the gate. Also, using non-suppressed sills under the gate breaks the flow lines. As the downstream progress, v-shaped sections are formed. Investigation of flow patterns in cylindrical and semi-cylindrical and pyramidal sills showed pyramidal sill causes a significant uniformity flow lines compared to other geometric shapes due to its sloping side at downstream. while sill with rectangular cube geometry improves rotational flows at downstream of sill. The results of placing sill in different geometric shapes under sluice gate indicate that using semicy-lindrical sill compared to other shapes increases in discharge coefficient and the highest values of discharge coefficient after this sill are allocated to cylindrical, pyramidal and rectangular cubic sills, respectively. semicylindrical average discharge coefficient increased 19.1 percent compared with the gate without sill. According to the laboratory findings, it was observed that increased sill width with decreased gate opening increases the discharge coefficient. Placing a sill with a width of 20 cm in all geometric shapes increases the discharge coefficient by an average of 10% compared to a sill with a width of 5 cm.
Conclusion: The study of discharge coefficient in 20 physical models showed that the highest values of discharge coefficient after semicircular sill are allocated to circular, triangular, and square sills, respectively. This increase is expressed because the semicircular, circular, triangular, and square sills at the smallest width (b = 5 cm) increased discharge coefficient by 6.5, 5.6, 3.5, and 1.6% compared to non- sill state, respectively. Changing sill width from 5 to 20 cm showed that discharge coefficient of semi-cylindrical, cylindrical, pyramidal and rectangular cubic increased by an average of 19.1, 17.2, 14.7, and 12.1% compared to non- sill state.


Ashkan, F., Daneshfaraz, R., Ghaffarinik, A., Gahramanzadeh, A. and Minaei, O. (2019). Numerical investigation of the successive sluice gates performance in regulating flow rate through channels using flow-3D software. J. Water and Soil Science. 29(4), 85-96. (In Persian)
Barghi Khezerloo, A., Khalili Shayan, H., Farhoudi, J. and Vatankhah, A. (2016). Developing a new method for estimating discharge coefficient of sluice gates under free and submerged flow conditions. J. Water and soil science. 26(4.1), 207-221. (In Persian)
Daneshfaraz, R., Ghahramanzadeh, A. and Ghaderi, A. (2016). Investigation of the Effect of Edge Shape on Characteristics of Flow Under Vertical Gates. J. American water works association. 108(8), E425- E432.
Daneshfaraz, R., Majedi Asl, M., Razmi, S., Norouzi, R. and Abraham, J. (2020). Experimental investigation of the effect of dual horizontal screens on the hydraulic performance of a vertical drop. J. Environmental Science and Technology. 17(5), 2927–2936.
Daneshfaraz, R., Norouzi, R., Ebadzadeh, P. and  Abbaszadeh, H. (2021a). Numerical investigation on effective parameters on hydraulic flows in a sluice gate with sill on free-flow condition. J. Environment and Water Engineering. doi: 10.22034/jewe.2021.295538.1596
Daneshfaraz, R., Norouzi, R. and Abbaszadeh, H. (2021b). Numerical investigation on effective parameters on hydraulic flows in chimney proportional weirs. Iranian Journal of Soil and Water Research. doi: 10.22059/ijswr.2021.322751. 668944. (In Persian)
Daneshfaraz, R., Sadeghfam, S. and Hasanniya, V.    (2019). Experimental investigation of energy dissipation in vertical drops equipped with a horizontal screen under supercritical flow, Iranian Journal of Soil and Water Research 50(6), 1421-1436. (In Persian)
Daneshfaraz, R., Abbaszadeh, H. Gorbanvatan, P. and Abdi, M. (2021). Application of Sluice Gate in Different Positions and Its Effect on Hydraulic Parameters in Free-Flow Conditions. Journal of Hydraulic Structures. 7(3), 72-87. doi: 10.22055/ jhs.2022.39208.1196.
Daneshfaraz, R., Norouzi, R. and Abbaszadeh, H. (2022). Experimental Investigation of Hydraulic Parameters of Flow in Sluice Gates with Different Openings. Environment and Water Engineering, doi: 10.22034/jewe.2022.321259.1700.
Golmohammadi, M.H. and Beyrami, M.K. (2011). Estimation of discharge for free flow under sluice and radial gates. J. Water and wastewater. 22(78), 94- 101. (In Persian)
Ilkhanipour Zeinali, R., Mousavi Jahromi, H., Kashefipour Dezfouli, M. and Fathi Mogaddam, M. (2015). Influence of gate plate slope on hydraulic characteristics of sluice gates. J. water and soil resources conservation. 4(4), 1-10. (In Persian)
Jalil, S., Serhan, S. and Subhi Ibrahim, S. (2016). Effect of prismatic sill on the performance of free flow under sluice gate. J. University of Zhako. 4(A)(1), 150-158.
Karami, S., Heidari, M.M. and Adib Rad, M.H. (2020). Investigation of Free Flow Under the Sluice Gate with the Sill Using Flow-3D Model. J. Iran Sci Technol Trans Civ Eng. 44, 317–324, Doi: 10.1007/s40996-019-00310-x.
Khalili Shayan, H., Farhodi, J. and Roshan, R. (2014). Estimation of flow discharge under the sluice and radial gates based on contraction coefficient. J. Science and Technology Transactions of Civil Engineering. 38(C2), 449-463.
Rezavand, N. (2018). Numerical Investigation of the Effect of Sill Height and Shape on the Flow Pattern of the Gates. Master of Science. University of Tabriz, Tabriz, Iran. 104 p.
Shivapur, A.V. and Sesha Prakash, M.N. (2005). Incined sluice gate for free measurement. ISH J. Hydraulic Engineering. 11(1), 46- 56.
Salmasi, F. and Norouzi, R. (2020). Investigation of different geometric shapes of sills on the discharge coefficient of a vertical sluice gate. J. Amirkabir Civil Engineering. 5(2), 1-3. (In Persian)
Volume 17, Issue 3 - Serial Number 173
September 2022
Pages 47-63
  • Receive Date: 24 November 2021
  • Revise Date: 10 March 2022
  • Accept Date: 12 March 2022
  • First Publish Date: 12 March 2022