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GATE 2021 ES – Question 35

Water Resources and Environmental Hydraulics · Environmental Hydraulics · 1 mark · Numerical answer

A 4 cm diameter orifice produces a 3.5 cm jet diameter at vena contracta. Velocity coefficient .98. Find discharge coefficient, to two decimals.

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Correct answer: .74 to .76

Explanation

Contraction coefficient is area ratio,$C_c=(3.5/4)^2=.765625$. Discharge coefficient $C_d=C_cC_v=.765625(.98)=.7503125$. Thus **.75**. Squaring the diameter ratio is essential because contraction is defined using areas.

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