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Fluid Mechanics - Engineering

Q1:

Fanning equation is given by. It is applicable to __________ region flow.

A transition

B laminar

C turbulent

D both (b) and (c)

ANS:D - both (b) and (c)

The Fanning friction factor equation, often denoted as fff, is given by: f=τwρV22=4τwρV2f = \frac{\tau_w}{\rho \frac{V^2}{2}} = \frac{4 \tau_w}{\rho V^2}f=ρ2V2​τw​​=ρV24τw​​ where:

  • τw\tau_wτw​ is the wall shear stress,
  • ρ\rhoρ is the fluid density,
  • VVV is the flow velocity.
This equation is applicable to both laminar and turbulent flow regions.
  • Laminar Flow: In laminar flow, the Fanning friction factor fff is directly proportional to the Reynolds number ReReRe and is given by f=16Ref = \frac{16}{Re}f=Re16​.
  • Turbulent Flow: In turbulent flow, the Fanning friction factor fff varies with the Reynolds number ReReRe and the relative roughness of the pipe wall.
Therefore, the Fanning equation is applicable to both (b) laminar and (c) turbulent flow regions. It provides a means to calculate the friction factor for both types of flow regimes in fluid mechanics.