Question

A beaker contains water up to a certain height as shown. If the water is allowed to get discharged through a small pipe (of a uniform diameter), what type of flow will it be in the pipe?

(a) steady and uniform

(b) unsteady and uniform

(c) steady and non-uniform

(d) unsteady and non-uniform

The question was posed to me during an interview for a job.

This interesting question is from Types of Fluid Flow in division Kinematics of Flow and Ideal Flow of Fluid Mechanics

Answer 1

The correct choice is (b) unsteady and uniform

Explanation: The velocity in which the water is discharged with a velocity   With time as the water gets discharged,v decreases as H decreases. Hence, it will be an unsteady flow.

According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. Since water is treated as an incompressible liquid (ρ =constant) and the pipe has a uniform diameter (A =constant) at a given instant, V will remain constant throughout the whole cross-section of the pipe. Hence, it will be a uniform flow.