ANS:D - neither (a) nor (b)

The Fanning friction factor equation applies to compressible fluid flow. Here’s why:

• Fanning Friction Factor: The Fanning friction factor (fff) is defined as: f=τw12ρu2f = \frac{\tau_w}{\frac{1}{2} \rho u^2}f=21​ρu2τw​​ where:
  • τw\tau_wτw​ is the wall shear stress,
  • ρ\rhoρ is the fluid density,
  • uuu is the velocity of the fluid.
• Applicability to Compressible Flow: The Fanning friction factor is commonly used in the analysis of compressible fluid flow, especially in pipes where pressure changes significantly affect the density and velocity of the fluid. It accounts for the viscous losses in compressible fluid flow and is a function of Reynolds number (ReReRe) and the pipe roughness.
• Non-Isothermal Conditions: The Fanning friction factor equation does not specifically address non-isothermal conditions. For non-isothermal flows, additional considerations such as temperature-dependent properties and heat transfer effects may need to be accounted for separately.