FROUDE

Calculates the Froude number, comparing inertial effects to gravitational effects for free-surface or gravity-influenced flow.

Excel Usage

=FROUDE(V, L, g, squared)

V (float, required): Characteristic velocity (m/s)
L (float, required): Characteristic length (m)
g (float, optional, default: 9.80665): Gravitational acceleration (m/s²)
squared (bool, optional, default: false): If true, returns squared Froude number

Returns (float): Froude number (float), or error message string.

Example 1: Standard gravity with unsquared Froude number

Inputs:

V	L	g	squared
1.83	2	9.80665	false

Excel formula:

=FROUDE(1.83, 2, 9.80665, FALSE)

Expected output:

0.413215

Example 2: Reduced gravity with unsquared Froude number

Inputs:

V	L	g	squared
1.83	2	1.63	false

Excel formula:

=FROUDE(1.83, 2, 1.63, FALSE)

Expected output:

1.01354

Example 3: Standard gravity with squared Froude number

Inputs:

V	L	g	squared
1.83	2	9.80665	true

Excel formula:

=FROUDE(1.83, 2, 9.80665, TRUE)

Expected output:

0.170746

Example 4: Reduced gravity with squared Froude number

Inputs:

V	L	g	squared
1.83	2	1.63	true

Excel formula:

=FROUDE(1.83, 2, 1.63, TRUE)

Expected output:

1.02727

Python Code

Show Code

from fluids.core import Froude as fluids_froude

def froude(V, L, g=9.80665, squared=False):
    """
    Calculate the Froude number (Fr) for a given velocity, length, and gravity.

    See: https://fluids.readthedocs.io/fluids.core.html#fluids.core.Froude

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

    Args:
        V (float): Characteristic velocity (m/s)
        L (float): Characteristic length (m)
        g (float, optional): Gravitational acceleration (m/s²) Default is 9.80665.
        squared (bool, optional): If true, returns squared Froude number Default is False.

    Returns:
        float: Froude number (float), or error message string.
    """
    try:
        V = float(V)
        L = float(L)
        g = float(g)
        squared = bool(squared)
    except Exception:
        return "Error: V, L, and g must be numeric values."
    if L <= 0 or g <= 0:
        return "Error: L and g must be positive."
    try:
        result = fluids_froude(V, L=L, g=g, squared=squared)
    except Exception as e:
        return f"Error: {str(e)}"
    return result

Online Calculator

V *

Characteristic velocity (m/s)

L *

Characteristic length (m)

Gravitational acceleration (m/s²)

squared

If true, returns squared Froude number