Darcy–Weisbach equation

The Darcy -Weisbach equation is an important empirical formula in the hydraulics of pipe flows. With it the pressure and energy losses can be calculated by pipe friction on the given length of pipe.

The Darcy -Weisbach equation to have been developed by Henry Darcy along with Julius Weisbach in Freiberg as a variant of Prony equation of Gaspard de Prony. Darcy was the formula but apparently only attributed erroneously; Instead, it comes from Jean François d' Aubuisson de Voisin (1834 ) and Weisbach (1845 ).

It reads:

Where:

• Hf head loss ( pressure drop)
• Pipe friction factor, depending on the material properties of the tube and the flow rate
• L / D ratio of length to diameter of the tube
• Average flow velocity v
• G acceleration due to gravity

To calculate the influence factors on the flow, which play a role, particularly in the design of pipelines (. , Where min flow, Eingangs-/Ausgangsdruck searched ), the equation can be rewritten using the Bernoulli equation:

Where:

• Inlet pressure p1
• Output pressure p2
• Density of the fluid
• Volume flow
• Cross-sectional area of the tube.

Initially lacked the data on the dependence of the friction factor of the flow rate, so the empirical Prony equation was used instead of the Darcy -Weisbach equation. Later, there were a number of other empirical equations, especially the Hazen -Williams equation, which were much easier to use in calculations usually. Only since there are calculators and computers, the simplicity of the calculation no longer plays such an important role. Therefore, today the general Darcy -Weisbach equation is preferred.

• Hydraulic