Calculate flow velocity, Reynolds number, and pressure drop in pipes from flow rate and diameter.
The Reynolds number indicates whether flow is laminar (Re < 2,300), transitional (2,300-4,000), or turbulent (Re > 4,000). Most pipe flows in practice are turbulent. Laminar flow is smoother and has less friction loss.
Pressure drop increases with higher velocity, longer pipe, smaller diameter, and rougher pipe walls. Doubling the flow velocity roughly quadruples the pressure drop. Pipe fittings (elbows, valves) add additional losses.