def modified_sommerfeld_number(radius_stator, omega, viscosity, length,
    load, radial_clearance):
    """Returns the modified sommerfeld number.
    Parameters
    ----------
    radius_stator : float
        The external radius of the bearing.
    omega: float
        Rotation of the rotor (rad/s).
    viscosity: float
        Viscosity (Pa.s).
    length: float
        Length in the Z direction (m).
    load: float
        Load applied to the rotor (N).
    radial_clearance: float
        Difference between both stator and rotor radius, regardless of eccentricity.

    Returns
    -------
    float
        The modified sommerfeld number.
    Examples
    --------
    >>> from ross.fluid_flow.fluid_flow import fluid_flow_example
    >>> my_fluid_flow = fluid_flow_example()
    >>> radius_stator = my_fluid_flow.radius_stator
    >>> omega = my_fluid_flow.omega
    >>> viscosity = my_fluid_flow.viscosity
    >>> length = my_fluid_flow.length
    >>> load = my_fluid_flow.load
    >>> radial_clearance = my_fluid_flow.radial_clearance
    >>> modified_sommerfeld_number(radius_stator, omega, viscosity,
    ...                            length, load, radial_clearance) # doctest: +ELLIPSIS
    0.33...
    """
    return radius_stator * 2 * omega * viscosity * length ** 3 / (8 * load *
        radial_clearance ** 2)
