drop, given the same flow rate. Piping fittings (such as elbow and tee joints) generally lead to greater pressure drop than straight pipe. As such, a number of correlations have been developed to calculate equivalent length of fittings. Certain valves are provided with an associated flow coefficient, commonly known as or . The flow coefficient relates pressure drop, flow rate, and specific gravity for a given valve. Many empirical calculations exist for calculation of pressure drop, including: Darcy–Weisbach equation, to calculate pressure drop in a pipe Hagen–Poiseuille equation See also ΔP head loss References External links Mechanics Fluid dynamics