CD_GRAF
Overview
Calculate drag coefficient of a sphere using the Graf correlation.
Excel Usage
=CD_GRAF(Re)Re(float, required): Particle Reynolds number [-]
Returns (float): Drag coefficient [-], or error message (str) if input is invalid.
Examples
Example 1: Reynolds number of 200
Inputs:
| Re |
|---|
| 200 |
Excel formula:
=CD_GRAF(200)Expected output:
0.8521
Example 2: Reynolds number of 1000
Inputs:
| Re |
|---|
| 1000 |
Excel formula:
=CD_GRAF(1000)Expected output:
0.4978
Example 3: Reynolds number of 10000
Inputs:
| Re |
|---|
| 10000 |
Excel formula:
=CD_GRAF(10000)Expected output:
0.3247
Example 4: Reynolds number of 100
Inputs:
| Re |
|---|
| 100 |
Excel formula:
=CD_GRAF(100)Expected output:
1.1536
Python Code
from fluids.drag import Graf as fluids_Graf
def cd_graf(Re):
"""
Calculate drag coefficient of a sphere using the Graf correlation.
See: https://fluids.readthedocs.io/fluids.drag.html#fluids.drag.Graf
This example function is provided as-is without any representation of accuracy.
Args:
Re (float): Particle Reynolds number [-]
Returns:
float: Drag coefficient [-], or error message (str) if input is invalid.
"""
try:
Re = float(Re)
if Re <= 0:
return "Error: Re must be positive."
result = fluids_Graf(Re=Re)
if result != result: # NaN check
return "Error: Calculation resulted in NaN."
return float(result)
except (ValueError, TypeError):
return "Error: Re must be a number."
except Exception as e:
return f"Error: {str(e)}"