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Fluid Mechanics: Major Head Loss

The major head loss considers the drop in pressure due to viscous effects. To calculate the major head loss equation 1 would be used.

Major head loss equation (1)

hLmajor = Major Head Loss

f = Friction Factor

L = Pipe Length

D = Pipe Diameter

v = Fluid Velocity

g = Gravitational Constant


The variable f in equation 1 represents the friction factor. To calculate the friction factor for laminar flow equation 2 would be used. If the flow is turbulent then the Moody Chart could be used, or equation 3 could be used.

friction factor equation laminar flow (2)

Re = Reynolds Number


friction factor equation turbulent flow (3)

Moody Chart (source Wikipedia )

Moody Chart

From equation 3, ε represents the roughness of the pipe's surface. The roughness of the pipe's surface has little to no effect on laminar flow.

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