HELICAL_RE_CRIT
Estimates the critical Reynolds number for transition between laminar and turbulent flow in curved or helical pipes from the tube and coil diameters. The wrapper exposes several published transition correlations, with Schmidt as the default method recommended by the library.
Because curvature stabilizes or destabilizes internal flow differently from straight pipes, the transition threshold depends on the coil geometry rather than being fixed at a single Reynolds number. This function provides that geometry-dependent transition estimate for helical-coil analysis.
Excel Usage
=HELICAL_RE_CRIT(Di, Dc, hrc_method)Di(float, required): Inner diameter of the tube making up the coil (m)Dc(float, required): Diameter of the helix/coil measured center-to-center (m)hrc_method(str, optional, default: “Schmidt”): Critical Reynolds number transition correlation method
Returns (float): Critical Reynolds number for transition in curved-pipe flow [-]
Example 1: Tight coil with default Schmidt method
Inputs:
| Di | Dc |
|---|---|
| 0.02 | 0.5 |
Excel formula:
=HELICAL_RE_CRIT(0.02, 0.5)Expected output:
6946.79
Example 2: Loose coil (large Dc) with Schmidt method
Inputs:
| Di | Dc |
|---|---|
| 0.01 | 2 |
Excel formula:
=HELICAL_RE_CRIT(0.01, 2)Expected output:
4122.9
Example 3: Using Ito method
Inputs:
| Di | Dc | hrc_method |
|---|---|---|
| 1 | 7 | Ito |
Excel formula:
=HELICAL_RE_CRIT(1, 7, "Ito")Expected output:
10730
Example 4: Using Srinivasan method
Inputs:
| Di | Dc | hrc_method |
|---|---|---|
| 1 | 7 | Srinivasan |
Excel formula:
=HELICAL_RE_CRIT(1, 7, "Srinivasan")Expected output:
11624.7
Python Code
Show Code
from fluids.friction import helical_Re_crit as fluids_helical_Re_crit
def helical_re_crit(Di, Dc, hrc_method='Schmidt'):
"""
Calculate the transition Reynolds number for fluid flowing in a curved or helical pipe between laminar and turbulent flow.
See: https://fluids.readthedocs.io/fluids.friction.html#fluids.friction.helical_Re_crit
This example function is provided as-is without any representation of accuracy.
Args:
Di (float): Inner diameter of the tube making up the coil (m)
Dc (float): Diameter of the helix/coil measured center-to-center (m)
hrc_method (str, optional): Critical Reynolds number transition correlation method Valid options: Seth Stahel, Ito, Kubair Kuloor, Kutateladze Borishanskii, Schmidt, Srinivasan. Default is 'Schmidt'.
Returns:
float: Critical Reynolds number for transition in curved-pipe flow [-]
"""
try:
Di = float(Di)
Dc = float(Dc)
hrc_method = str(hrc_method)
if Di <= 0:
return "Error: Di must be positive."
if Dc <= 0:
return "Error: Dc must be positive."
valid_methods = [
"Seth Stahel",
"Ito",
"Kubair Kuloor",
"Kutateladze Borishanskii",
"Schmidt",
"Srinivasan",
]
if hrc_method not in valid_methods:
return f"Error: hrc_method must be one of {valid_methods}."
result = fluids_helical_Re_crit(Di=Di, Dc=Dc, Method=hrc_method)
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)}"