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.


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Volume 13, Issue 4 - Serial Number 134
February 2019
Pages 121-131
  • Receive Date: 02 September 2018
  • Revise Date: 07 November 2018
  • Accept Date: 12 November 2018
  • First Publish Date: 21 January 2019