Which parameter describes the resistance to flow in a pipe due to roughness and turbulence?

• A. Velocity
• B. Friction Factor
• C. Water Harvesting
• D. Potable Water

Answer: (B)

The friction factor is the quantity that describes how much resistance a pipe offers to flow due to wall roughness and turbulent eddies. It’s a dimensionless number used in the Darcy-Weisbach equation to calculate head loss along a pipe: h_f = f (L/D) (v^2/(2g)). The friction factor increases with rougher interiors and with more turbulent flow, and it’s determined by relative roughness and Reynolds number (often read from the Moody chart or using appropriate correlations). This directly links pipe roughness and turbulence to the energy lost as water travels through the system, which is essential for designing adequate pump pressure and ensuring proper irrigation flow. Velocity, while related to flow, is a rate of motion, not a measure of resistance; Water Harvesting and Potable Water refer to broader concepts unrelated to the hydraulic resistance described by the friction factor.