SSC JE Civil Engineering 29-Oct-2020 Shift 1 Paper

Question : 180 of 200

Marks: +1, -0

Which of the following statements are true about laminar flow through pipes?
i. Fluid particles move along straight parallel path in layers.
ii. Path of the individual particle crosses path of neighbouring particles.
iii. Reynold's number is less than 2000.
iv. Reynold's number is more than 4000.

Both statements ii and iv are true
Both statements i and iv are true
Both statements ii and iii are true
Both statements i and iii are true

Validate

Solution:

Laminar Flow: Laminar flow is the flow in which fluid particles flow in layers. Each layer moves smoothly past the adjacent layer with little or no intermixing. There is no intermingling of fluid particles across the cross-section.
Turbulent Flow: Turbulent flow is the flow in which fluid particles flow in a random fashion where intermixing/intermingling is present.
Reynolds number is a dimensionless formula that is used to differentiate laminar flow from the turbulent flow.
Reynolds number is given by

\Re = {{\ρ×\V ×\D}}/{\µ}

Where,
ρ = Density of fluid, V = velocity of fluid, D = Diameter of pipe, μ = Dynamic viscosity of the fluid
In the case of pipe flow,
● If Re ≤ 2000 then flow is laminar
● 2000 ≤ Re ≤ 4000 then flow is transitional
● Re ≥ 4000 then flow is turbulent

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