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Commonly Used Formula in Hydraulics

Darcy Weisbach formula
Darcy Weisbach formula which is valid for laminar or turbulent flow in all fluids is one of the most commonly used formula for determining the head loss.


hf=head loss due to friction, ft (m)

f= friction factor

L =length of pipe, ft (m)

D= diameter of pipe, ft (m)

V =velocity of fluid, ft/s (m/s)

g =acceleration due to gravity, 32.2 ft/s2 (9.81 m/s2)


Chezy Formula

This Equation holds got for head loss in conduits and gives good results for high Reynolds numbers:


C=coefficient depending on surface roughness of conduit
S=slope of energy grade line or head loss due to friction of conduit
R=hydraulic radius,ft(m)
Generally R=Area/wetted perimeter

Manning’s Formula
According to this


n=coefficient depending on surface roughness.Now with this vaue of R=D/4 we can calculate V and Q.


Hazen Williams Formula
This is one of the most widely used formula and is given below:


R= hydraulic radius, ft (m)

S= head loss due to friction, ft/ft (m/m) of pipe

D= diameter of pipe, ft (m)
L= length of pipe, ft (m)
Q= discharge, ft3/s (m3/s)
hf =friction loss, ft (m)

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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3 comments on "Commonly Used Formula in Hydraulics"

sweta priya says:

the above written V=C?(RS) should be V=C/(RS).

Jagdish J.Asodia says:

We are very thank you for your metal weight calculator.Thanks a lot.

ven mana says:

verry nice

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