SWAMEE_JAIN
Computes Darcy friction factor with the Swamee-Jain explicit equation using Reynolds number and relative roughness for turbulent pipe flow. This correlation is a common alternative to iterative Colebrook calculations when a closed-form engineering approximation is preferred.
The implemented expression is:
\frac{1}{\sqrt{f_d}} = -4\log_{10}\left[\left(\frac{6.97}{Re}\right)^{0.9} + \frac{\epsilon}{3.7D}\right]
It is intended for turbulent straight-pipe applications within the published validity range of the correlation.
Excel Usage
=SWAMEE_JAIN(Re, eD)Re(float, required): Reynolds number, [-]eD(float, required): Relative roughness (roughness/diameter), [-]
Returns (float): Darcy friction factor from the Swamee-Jain equation [-]
Example 1: Smooth pipe with low Reynolds number
Inputs:
| Re | eD |
|---|---|
| 10000 | 0.000001 |
Excel formula:
=SWAMEE_JAIN(10000, 0.000001)Expected output:
0.0309738
Example 2: Smooth pipe with high Reynolds number
Inputs:
| Re | eD |
|---|---|
| 100000 | 0.0001 |
Excel formula:
=SWAMEE_JAIN(100000, 0.0001)Expected output:
0.0184524
Example 3: Rough pipe
Inputs:
| Re | eD |
|---|---|
| 50000 | 0.01 |
Excel formula:
=SWAMEE_JAIN(50000, 0.01)Expected output:
0.0394639
Example 4: Very rough pipe at upper eD limit
Inputs:
| Re | eD |
|---|---|
| 1000000 | 0.05 |
Excel formula:
=SWAMEE_JAIN(1000000, 0.05)Expected output:
0.0716069
Python Code
Show Code
from fluids.friction import Swamee_Jain_1976 as fluids_swamee_jain
def swamee_jain(Re, eD):
"""
Calculate Darcy friction factor using the Swamee-Jain (1976) equation.
See: https://fluids.readthedocs.io/fluids.friction.html#fluids.friction.Swamee_Jain_1976
This example function is provided as-is without any representation of accuracy.
Args:
Re (float): Reynolds number, [-]
eD (float): Relative roughness (roughness/diameter), [-]
Returns:
float: Darcy friction factor from the Swamee-Jain equation [-]
"""
try:
Re = float(Re)
eD = float(eD)
if Re <= 0:
return "Error: Reynolds number must be positive."
if eD < 0:
return "Error: Relative roughness must be non-negative."
result = fluids_swamee_jain(Re=Re, eD=eD)
if result != result:
return "Error: Result is NaN."
if result == float('inf') or result == float('-inf'):
return "Error: Result is not finite."
return float(result)
except Exception as e:
return f"Error: {str(e)}"