3.2.27 cw_cheng - Cheng friction factor

f = cw_cheng(d,e,re)

Calculate the Cheng approximation of the Colebrook-White equation.

Arguments

d

Pipe internal diameter ().

e

Pipe effective roughness .

re

Reynolds number

Returns Darcy friction factor , dimensionless.

Possible Errors

Cheng diameter is <= 0

The given internal diameter of the pipe must be above zero.