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, 43:61 | Cite as

Experimental determination of contraction coefficient and velocity coefficient for radial gates with elliptical lips

  • Jailakshmi Menon
  • B V Mudgal
Article
  • 45 Downloads

Abstract

Radial gates are widely used to control the flow in irrigation channels and spillways. Radial gates require lower hoisting force and have better discharge characteristics in partial gate openings. The accurate discharge measurement through a radial gate is a challenging problem especially in submerged flow conditions. The coefficient of contraction \( C_{c} \) is an important parameter for accurate discharge measurement in open channels. In this study, an attempt has been made to determine the coefficient of contraction\( C_{c} \) and velocity coefficient \( C_{v} \) for radial gates both for free flow and submerged flow conditions. The flow emanating from a gate is similar to the wall jet emerging from a nozzle. The \( C_{c} \) and \( C_{v} \) values under free and submerged flow conditions are obtained from the measured jet velocity and the discharge. The coefficient of discharge values under submerged flow conditions show large variations with submergence and hence discharge characteristics needs to be improved for better control of flow. Hence, experiments are conducted so as to improve the discharge characteristics by modifying the exit geometry of the radial gate by attaching a quarter of an elliptical lip. Three different geometries of elliptical lips were attempted and the results show reasonable increase in the contraction coefficient.

Keywords

Radial gates contraction coefficient wall jet acoustic doppler velocimeter (ADV) laboratory experiments 

List of symbols

a

height of gate opening

b

length of the semi minor axis of the quadrant lip

\( C_{c} \)

coefficient of contraction of the gate

\( C_{v} \)

coefficient of velocity

\( C_{dw} \)

coefficient of discharge of the weir

d

length of the semi major axis of the quadrant lip

\( g \)

acceleration due to gravity

H

difference in manometer readings in the u-tube

\( H_{w} \)

head over the crest of the weir

\( H_{1} \)

upstream energy head

\( L \)

width of the channel and length of the weir

P

height of the weir

p

pinion height of the gate

Qact

actual discharge in the flume

R

radius of the radial gate

\( R_{e} \)

Reynolds number

\( v \)

velocity downstream of the gate

\( v_{j} \)

jet velocity

\( v_{1} \)

average velocity upstream of the gate

\( y \)

depth of water immediately downstream of the gate

\( y_{j} \)

depth of water at the vena-contracta

\( y_{1} \)

depth of water upstream of the gate

\( y_{2} \)

depth of water downstream at the exit of the gate

\( y_{3} \)

tail water depth in the flume

α

velocity distribution coefficient

β

energy loss coefficient

\( \nu \)

kinematic viscosity

θ

gate angle

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Copyright information

© Indian Academy of Sciences 2018

Authors and Affiliations

  1. 1.Centre for Water ResourcesAnna UniversityChennaiIndia

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