ANS:B - more than 3000

Flow in pipes is turbulent if the Reynolds number is more than 3000. The Reynolds number (Re) is a dimensionless quantity used to predict the flow regime in a pipe. It is defined as the ratio of inertial forces to viscous forces within a fluid flow. Mathematically, it is expressed as: Re=ρ⋅V⋅D​/μ Where:

• ρ is the density of the fluid,
• V is the velocity of the fluid,
• D is the characteristic diameter of the pipe, and
• μ is the dynamic viscosity of the fluid.

When the Reynolds number is less than 2100, the flow is typically laminar, characterized by smooth and predictable flow patterns. When the Reynolds number exceeds 3000, the flow is generally turbulent, characterized by chaotic and irregular flow patterns. Therefore, the correct statement is: Flow in pipes is turbulent if the Reynolds number is more than 3000.