(1) | {\rm Re} = \frac{u(l) \cdot d}{\nu(l)} = \frac{4 \rho_s q_s}{\pi d} \frac{1}{\mu(T, p)} |
\displaystyle {\rm Re} = \frac{u(l) \cdot d}{\nu(l)} = \frac{4 \rho_s q_s}{\pi d} \frac{1}{\mu(T, p)}
The along-hole variation of Darcy friction factor f is usually not exceeding 2-3 % and in many practical applications can be considered as constant along hole f = f_s = \rm const.
The absolute value is staying between f = 0.04 for the very small flow rates (< 100 cmd) and f = 0.015 for the very high flow rates (> 1,000 cmd).
See also
Physics / Fluid Dynamics / Pipe Flow Dynamics / Darcy–Weisbach equation / Darcy friction factor