Question

Flow over a spillway of a dam is to be treated as

• A. Flow over a weir
• B. Flow through an orifice
• C. Flow through a mouthpiece
• D. Flow through a pipeline

Hint:

Remember: \[ \boxed{ \begin{aligned} \text{Weir} &\rightarrow \text{Flow over an opening}\\ \text{Orifice} &\rightarrow \text{Flow through an opening} \end{aligned} } \]

Answer 1

The Correct Option is A

Step 1: Recall what a weir actually is.
A weir is simply an obstruction placed across a channel so that water falls freely over its crest, with the falling sheet (nappe) exposed to atmospheric pressure on the outside.
Step 2: Compare this with a spillway.
A spillway sits on the crest of a dam and lets surplus water fall freely down its downstream face, again with the flow open to the atmosphere rather than confined like in a pipe or orifice.
Step 3: Match the behaviour.
Since both cases involve free surface flow falling over a crest under atmospheric pressure, spillway flow is treated using weir hydraulics.
\[ \boxed{\text{Flow over a weir}} \]