Moody Chart
Moody Chart or Moody Diagram
 In Fluid Mechanics, the Moody chart or Moody diagram is a graph which relates the DarcyWeisbach friction factor (f_{D )}, Reynolds number (Re), and surface roughness for fully developed flow in a circular pipe.
 It can be used to predict pressure drop or flow rate down such a pipe.

This diagram is used to estimate friction coefficients by DarcyWeisbach major loss equation
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This nondimensionl chart is used to calculate pressure drop, ΔP (Pa) (or head loss, h_{f} (m)) and flow rate through pipes. Head loss can be calculated using the Darcy–Weisbach equation in which the Darcy friction factor f_{D} appears :
We can rewrite the above equation in terms of fanning friction factor as :
Where fD =4*f (Relationship between darcy friction factor and fanning friction factor).
Hence Pressure drop in the flow field can be calculated as :
or,
where,
ρ : density of the fluid,
V : average velocity in the pipe,
f_{D} : friction factor from the Moody chart,
L : Characteristic length of the pipe
D : pipe diameter.
The Moody chart can be divided into two regimes of flow: laminar and turbulent. For the laminar flow regime (Re < ~2000), roughness has no discernible effect, and the Darcy–Weisbach friction factor f_{D} was determined analytically by Poiseuille:
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