What is the result of the interaction between a hose or pipe and flowing water that leads to a reduction in flow pressure?

The interaction between a hose or pipe and flowing water that leads to a reduction in flow pressure is best described as friction loss. This phenomenon occurs due to the resistance that the water encounters as it moves through the internal surfaces of the hose or pipe. The walls of the hose or pipe create friction against the moving water, which results in a loss of pressure over distance.

Friction loss is an important concept in fluid dynamics, especially in firefighting and other applications where water must be transported through hoses and pipes. It emphasizes how factors such as the pipe's length, diameter, surface roughness, and the speed of the water flow influence the overall pressure loss. Understanding friction loss is crucial for accurately calculating the pressure needed to deliver water effectively to a fire or any other application requiring a water supply.

While pressure loss might seem to directly relate to what is happening, it is the friction between the water and the material of the hose or pipe that specifically accounts for the reduction in flow pressure as water flows.