Question

Given below are two statements: Statement (I): Flumes are specially shaped and constructed channel sections used to measure the flow of water. Statement (II): The principle of flumes is based on the concept of kinetic energy and critical flow in open channels. In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

Flumes create critical flow conditions at their throat.
This eliminates downstream backwater effects, allowing the flow rate to be determined by measuring a single upstream water depth.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Flumes are primary flow-measuring devices installed in open channels, irrigation canals, and sewer systems to determine discharge rates without causing significant head loss.

Step 2: Detailed Explanation:
Let us evaluate both statements:
Statement (I): Flumes (such as the Parshall flume or Cutthroat flume) are specialized structures built with converging, constricted (throat), and diverging sections.
By measuring the depth of water at specific locations within the flume, the volumetric flow rate can be accurately determined, making Statement (I) correct.
Statement (II): Flumes operate by narrowing the channel width or raising the channel floor, which accelerates the water flow.
This acceleration forces the flow to transition from subcritical to supercritical, passing through a state of critical flow at the throat.
At critical flow, a unique, stable relationship is established between the water depth (potential energy) and velocity (kinetic energy).
This allows surveyors to calculate discharge using a single upstream depth measurement, making Statement (II) correct.
Thus, both statements are correct.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are correct.