What does velocity head measure?

Velocity head refers to the energy of fluid motion in a system, typically expressed in terms of the height of a fluid column. It is given by the formula ( \frac{v^2}{2g} ), where ( v ) is the flow velocity and ( g ) is the acceleration due to gravity.

When considering velocity head, it is important to understand its relationship with static and total pressure head. Velocity head represents the kinetic energy of flowing fluid, and as fluid velocity increases, this kinetic energy contributes to changes in pressure. However, if we consider a closed system with a constant mass flow rate, an increase in velocity head can lead to a decrease in static pressure head, according to Bernoulli’s principle.

In this context, the correct answer identifies that velocity head measures how motion affects the static pressure within a system. Therefore, understanding velocity head is crucial for plumbing design, as it plays a significant role in calculating flow rates and ensuring that systems are designed to operate effectively while accounting for fluctuations in pressure.

This explanation aids in linking the concept of velocity head with the implications of fluid dynamics, helping to reinforce foundational principles necessary for plumbing design.