Moody Diagram

The Moody chart or Moody diagram is a graph in non-dimensional form that relates the Darcy-Weisbach friction factor, Reynolds number and relative roughness for fully developed flow in a circular pipe. It can be used for working out pressure drop or flow rate down such a pipe.

Curves generated by experimental data:

Key points about the Moody Diagram –
1). In the laminar zone – f decreases as Nr increases!
2). f = 64/Nr.
3). transition zone – uncertainty – not possible to predict -
4). Beyond 4000, for a given Nr, as the relative roughness term
     D/ε increases (less rough), friction factor decreases
5). For given relative roughness, friction factor decreases with
     increasing Reynolds number till the zone of complete
     turbulence
6). Within the zone of complete turbulence – Reynolds number
     has no affect.
7). As relative roughness increases (less rough) – the boundary
     of the zone of complete turbulence shifts (increases)

• If you know that- the relative roughness,Reynold number-you can compute the friction factor from the Moody Diagram.