ANS:D - ∞

For an ideal fluid flow, the Reynolds number (ReReRe) is 0. Here’s why:

• Ideal Fluid Flow: An ideal fluid is an imaginary fluid that is inviscid (zero viscosity) and incompressible (constant density). In such a fluid, there are no shear forces between layers of fluid, and thus, no viscosity effects are present.
• Reynolds Number Definition: The Reynolds number (ReReRe) is defined as: Re=ρVLμRe = \frac{\rho V L}{\mu}Re=μρVL​ where:
  • ρ\rhoρ is the density of the fluid,
  • VVV is the characteristic velocity of the flow,
  • LLL is a characteristic length (such as the diameter of a pipe),
  • μ\muμ is the dynamic viscosity of the fluid.
• Ideal Fluid Characteristics: In an ideal fluid where viscosity (μ\muμ) is zero, the Reynolds number becomes: Re=ρVL0=∞Re = \frac{\rho V L}{0} = \inftyRe=0ρVL​=∞ This indicates that in ideal fluid flow, the Reynolds number tends towards infinity because there is no viscous resistance to flow.