Which of the following statements are correct for an incompressible flow?

I) In incompressible flows, variation in density is negligible.

II) Incompressible flows are always laminar.

III) Incompressible flows can be internal as well as external.

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DFCCIL Executive Mechanical 28 Sept 2021 Paper (Shift 1)
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  1. only I and II
  2. I, II and III
  3. Only II and III
  4. only I and III

Answer (Detailed Solution Below)

Option 4 : only I and III
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Detailed Solution

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Explanation:

Incompressible flow: It is that type of flow in which the density is constant for the fluid flow. Liquids are generally incompressible while gases are compressible.

Mathematically, ρ = Constant.

These can be laminar or turbulent, external or internal.

Laminar and Turbulent flow is considered to be incompressible if the density is constant or the fluid expands with little energy in compressing the flow. Hence a flow with varying density (Incompressible) flow could be Laminar & Turbulent.

Additional Information

Compressible flow: The flow in which the density of the fluid changes from point to point or the density is not constant for the fluid

Mathematically, for compressible flow ρ ≠ Constant

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