DarcyWeisbachtype

The Darcy–Weisbach type refers to a class of friction loss models used to estimate head loss or pressure drop due to pipe flow, based on the Darcy–Weisbach equation. This approach is widely used in civil and mechanical engineering for calculating energy losses in closed conduits such as water mains, industrial piping, and HVAC networks. The core idea is that the friction factor encapsulates the effects of flow regime, pipe roughness, and geometry, allowing the head loss to be expressed in terms of pipe length, diameter, flow velocity, and gravitational acceleration.

The standard form of the Darcy–Weisbach equation for head loss is h_f = f (L/D) (v^2/(2g)), where h_f is the friction head loss, f is the Darcy friction factor, L is pipe length, D is hydraulic diameter, v is mean flow velocity, and g is gravitational acceleration. The friction factor f depends on the Reynolds number Re = vD/ν and the relative roughness ε/D. In laminar flow (Re < 2000–4000 depending on convention), f = 64/Re. In turbulent flow, f is a function of Re and relative roughness, typically determined from the Moody chart or implicit relations such as the Colebrook equation, with several explicit approximations (for example Swamee–Jain) used for direct computation.

Darcy–Weisbach type models are used across many applications, from designing potable water systems and wastewater networks to predicting pressure drops in industrial process piping. They require specifying pipe roughness and flow regime to select the appropriate friction factor. While highly versatile, the approach assumes steady, incompressible flow in fully developed conditions and may require adjustments for highly transient, multi-branch, or non-circular conduits.

See also related friction models such as Hazen–Williams and Manning, which offer alternative approaches for specific fluids, geometries, or regimes.