CONTRACTION_ROUND

Overview

Calculate the loss coefficient (K) for a rounded pipe contraction (reducer).

Excel Usage

=CONTRACTION_ROUND(Di_large, Di_small, rc, con_rnd_method)

• Di_large (float, required): Inside diameter of original (larger) pipe [m]
• Di_small (float, required): Inside diameter of following (smaller) pipe [m]
• rc (float, required): Radius of curvature of the contraction [m]
• con_rnd_method (str, optional, default: “Rennels”): Calculation method

Returns (float): Loss coefficient K for the rounded contraction [-]

Examples

Example 1: Basic rounded contraction

Inputs:

Di_large	Di_small	rc
1	0.4	0.04

Excel formula:

=CONTRACTION_ROUND(1, 0.4, 0.04)

Expected output:

Result
0.1783

Example 2: Rounded contraction with Miller method

Inputs:

Di_large	Di_small	rc	con_rnd_method
1	0.4	0.04	Miller

Excel formula:

=CONTRACTION_ROUND(1, 0.4, 0.04, "Miller")

Expected output:

Result
0.0857

Example 3: Large radius of curvature

Inputs:

Di_large	Di_small	rc
0.5	0.2	0.1

Excel formula:

=CONTRACTION_ROUND(0.5, 0.2, 0.1)

Expected output:

Result
0.0374

Example 4: Small radius of curvature

Inputs:

Di_large	Di_small	rc
0.5	0.2	0.01

Excel formula:

=CONTRACTION_ROUND(0.5, 0.2, 0.01)

Expected output:

Result
0.2672

Python Code

import micropip
await micropip.install(["fluids"])
from fluids.fittings import contraction_round as fluids_contraction_round

def contraction_round(Di_large, Di_small, rc, con_rnd_method='Rennels'):
    """
    Calculate the loss coefficient (K) for a rounded pipe contraction (reducer).

    See: https://fluids.readthedocs.io/fluids.fittings.html#fluids.fittings.contraction_round

    This example function is provided as-is without any representation of accuracy.

    Args:
        Di_large (float): Inside diameter of original (larger) pipe [m]
        Di_small (float): Inside diameter of following (smaller) pipe [m]
        rc (float): Radius of curvature of the contraction [m]
        con_rnd_method (str, optional): Calculation method Valid options: Rennels, Miller, Idelchik. Default is 'Rennels'.

    Returns:
        float: Loss coefficient K for the rounded contraction [-]
    """
    try:
        Di1 = float(Di_large)
        Di2 = float(Di_small)
        rc = float(rc)
    except (ValueError, TypeError):
        return "Error: Di_large, Di_small, and rc must be numbers."

    if Di1 <= 0 or Di2 <= 0:
        return "Error: Diameters must be positive."
    if Di2 >= Di1:
        return "Error: Di_small must be less than Di_large."
    if rc < 0:
        return "Error: Rc must be non-negative."

    try:
        result = fluids_contraction_round(Di1=Di1, Di2=Di2, rc=rc, method=con_rnd_method)
        return float(result)
    except Exception as e:
        return f"Error: {str(e)}"

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