Section 4: Soil and Water Conservation Engineering
Fluid Mechanics
Subtopic: Dimensional analysis – concepts of geometric dimensionless numbers
Question Statement:
In hydraulic similitude and model testing of open channels, spillways, and weirs, dynamic similarity is governed primarily by equality of the:
Options:
(A) Reynolds number
(B) Froude number
(C) Weber number
(D) Mach number
Answer Key:
B
Step-by-Step Solution & Explanation
In free-surface flows (such as spillways, open channels, and weirs), gravity is the predominant fluid force resisting inertia. Hence, the Froude number ($Fr = \frac{V}{\sqrt{g L}}$) governs the dynamic similitude.