Darcy friction factor f calculation

Darcy friction factor f as a function of Reynolds number Re and pipe relative roughness ε / d, fitting the data of experimental studies of turbulent flow in smooth and rough pipes.

The equation can be used to (alliteratively) solve for the Darcy–Weisbach friction factor f.

For a conduit flowing completely full of fluid at Reynolds numbers greater than 4000, it is expressed as:

1/√(f) = -2*log((e/d)/3.7 + 2.51/(Nre*√(f))

As can see from the formula, simple calculation is not possible, so user should use iterative calculations or a solver to find the value of f that satisfies the formula.

Pipe Material Commercial Steel, e = 0.05
Pipe Internal Diameter (d, mm) = 25
Reynold's Number (Re) = 100000
Relative Roughness (ε/D)  0.002
Friction factor (f) 0.023

Run Python code below : https://www.mycompiler.io/view/4rbUNlvs1QN

import math
import numpy as np

def frictionfactor(piping, d, Nre):

    piping = "Commercial Steel"
    if piping == "Commercial Steel": e = 0.05
    if piping == "Cast Iron": e = 0.26
    if piping == "Galvanized Iron": e = 0.15
    if piping == "Asphalted Cast Iron": e = 0.12
    if piping == "Drawn Tubing": e = 0.0015

    if (Nre > 1 and Nre <= 2000):
        
        f_result = 64 / Nre

    elif Nre > 4000:

        delta_result = 1
        delta = 1

        for f in np.arange(0.001, 0.1, 0.001):
            lhs = 1/math.sqrt(f)
            rhs = -2*math.log10((e/d)/3.7 + 2.51/(Nre*math.sqrt(f)))
            delta = abs(lhs - rhs)
            if (delta < delta_result):
                delta_result = delta
                f_result = f
    else:
        pass
    
    return f_result

f = frictionfactor("Commercial Steel", 25, 10000)
print("darcy friction factor = ", f)

When run the code, you will receive the following results.

darcy friction factor =  0.034