Darcy friction factor f for wellbore flow can be written as:
(1) | {\rm Re}(l) = \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 due to the influence of pressure
p(l) and temperature
T(l) variations on the fluid viscosity
\mu(T, p).
For water flow it is usually not exceeding 10 % 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