Darcy Equation Fluids Flow Equation

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Hydraulic and Pneumatic Knowledge
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Darcys Equation Fluids Flow Equation - also called Darcy–Weisbach equation.

In fluid dynamics , the Darcy–Weisbach equation is a phenomenological equation, which relates the head loss — or pressure loss — due to friction along a given length of pipe to the average velocity of the fluid flow.

The Darcy–Weisbach equation contains a dimensionless friction factor, known as the Darcy friction factor . This is also called the Darcy–Weisbach friction factor or Moody friction factor . The Darcy friction factor is four times the Fanning friction factor , with which it should not be confused.

The frictional head loss can be calculated using a mathematical relationship that is known as Darcys equation for head loss. The equation takes two distinct forms. The first form of Darcys equation determines the losses in the system associated with the length of the pipe.

Darcys Equation Calculator <--- Open

Formula 1
hf = f ( L / D ) ( v2 / ( 2 g ) )


f = friction factor (unitless)
L = length of pipe (ft)
D = diameter of pipe (ft)
v = fluid velocity (ft/sec)
g = gravitational acceleration (ft/sec2)



  • Piping Calculations Manual,
    E. Shashi Menon
    SYSTEK Technologies, Inc