In engineering, the Moody chart or Moody diagram (also Stanton diagram) is a graph in
non-dimensional
A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...
form that relates the
Darcy–Weisbach friction factor ''f''
''D'',
Reynolds number
In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be domi ...
Re, and
surface roughness
Surface roughness, often shortened to roughness, is a component of surface finish (surface texture). It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, ...
for fully developed
flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe.
History
In 1944,
Lewis Ferry Moody plotted the
Darcy–Weisbach friction factor against
Reynolds number
In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be domi ...
Re for various values of relative
roughness ε / ''D''.
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