KSCE Journal of Civil Engineering

, Volume 23, Issue 5, pp 2117–2125 | Cite as

Laboratory Study of the Effect of Sills on Radial Gate Discharge Coefficient

  • Farzin SalmasiEmail author
  • Mysam Nouri
  • John Abraham
Hydraulic Engineering


In the present study, the effect of a sill on the discharge coefficient (CD) of radial gates in a free flow condition has been investigated. Different sill shapes were used including a circle, a semicircle, a triangle, a rectangle and a trapezoid. Variable geometric parameters of these sills that were investigated were length, upstream slope, downstream slope and sill height. In addition, the effect of sill location on CD was investigated so that in case 1, with an open gate, the sill was located upstream of the gate. In case 2, the sill is located under the gate. In total, 43 physical models of different shapes sizes of sills were used. The results showed that when the radial gate is open and sills are in upstream of the gates (case 1), the sill operates as a barrier and reduces CD. But in case 2, the sill location has a positive effect on CD. In case 2, the semicircle shape has better performance and increases CD by about 30% compared to the gate without a sill. Also, the rectangular and trapezoidal sills always increase CD. In these sills, increases in CD depend on the sill length to its height (L/Z). Small values of L/Z increase the discharge coefficient up to 13%. Finally, for circular and semicircular sill shapes, two regression equations were presented which can be used by designers.


radial gate discharge coefficient sill free condition flow measurement 


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Copyright information

© Korean Society of Civil Engineers 2019

Authors and Affiliations

  1. 1.Dept. of Water EngineeringUniversity of TabrizTabrizIran
  2. 2.School of EngineeringUniversity of St. ThomasSt. PaulUSA

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