In pipe sizing, which two primary factors are typically considered to determine flow characteristics?

• A. Velocity
• B. Friction Factor
• C. Velocity and Friction Factor
• D. Pipe Sizing

Answer: (C)

Flow characteristics in pipe sizing hinge on two main ideas: how fast the fluid is moving and how much resistance the pipe presents to that motion. In the common energy–loss framework, those ideas appear as velocity and the friction factor. Velocity sets the energy per unit weight and the actual flow rate through the cross‑section, while the friction factor captures the pipe’s roughness and the flow regime (laminar or turbulent), which determine how much energy is lost to friction along the length of the pipe. The combination of velocity and friction factor directly controls the pressure drop for a given length and diameter, guiding what diameter can carry the desired flow with an acceptable loss. Considering velocity alone would ignore losses, and considering friction factor alone would ignore how much fluid is being moved. Pipe sizing is about selecting a diameter that achieves the needed flow with acceptable losses, so velocity and friction factor are the two primary factors.