The oil with specific gravity 0.8, dynamic viscosity of 8 × 10-3 Ns/m2 flows through a smooth pipe of 100 mm diameter and with Reynolds number 2100. The average velocity in the pipe is:

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ESE Mechanical 2016 Paper 1: Official Paper
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  1. 0.21 m/s
  2. 0.42 m/s
  3. 0.168 m/s
  4. 0.105 m/s

Answer (Detailed Solution Below)

Option 1 : 0.21 m/s
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ST 1: UPSC ESE (IES) Civil - Building Materials
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Detailed Solution

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Concept:

Where, ρ is the density of the fluid and Vavg is the average velocity of the fluid in the pipe and D is the diameter of the pipe and μ is the dynamic viscosity of the fluid

Calculation:

Given,

Specific gravity of oil = 0.8, thus density = 0.8 × 1000 = 800 kg/m3

Reynolds number = 2100, Dynamic viscosity = 8 × 10-3 Ns/m2,

Diameter = 100 mm = 100 × 10-3 m

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