Section 4: Soil and Water Conservation Engineering
Fluid Mechanics
Subtopic: Continuity equation, kinematics and dynamics of flow
Question Statement:
The velocity of a fluid in a pipe A of diameter D is v m s⁻¹. This pipe is connected with another pipe B of diameter 2D. Reynold's number in pipe A in relation to pipe B is
Options:
(A) same
(B) half
(C) double
(D) triple
Official Answer Key:
C
Step-by-Step Solution & Explanation
By continuity, V_A·D² = V_B·(2D)² → V_B = V_A/4. Re_A = V_A D/ν; Re_B = V_B(2D)/ν = (V_A/4)(2D)/ν = V_A D/(2ν) = Re_A/2. Hence Re_A = 2·Re_B — Reynolds number in pipe A is double that in pipe B.
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