def w_oper(rho_mix, rho_vapor):
    """
    Calculates the operating speed in column.
    Parameters
    ----------
    rho_mix : float
        The destiny of mix, [kg/m**3]
    rho_vapor : float
        The destiny of vapor, [kg/m**3]
    Returns
    -------
    w_oper : float
        The operating speed in column. [m]
    References
    ----------
    Дытнерский, страница 205, формула 5.33
    """
    return 0.05 * rho_mix**0.5 / rho_vapor**0.5