def Gregory_Scott(x, rhol, rhog):
    r'''Calculates void fraction in two-phase flow according to the model of 
    [1]_ as given in [2]_ and [3]_.
    
    .. math::
        \alpha = \frac{x}{\rho_g}\left[C_0\left(\frac{x}{\rho_g} + \frac{1-x}
        {\rho_l}\right) +\frac{v_{gm}}{G} \right]^{-1}
        
    .. math::
        v_{gm} = 0

    .. math::
        C_0 = 1.19
        
    Parameters
    ----------
    x : float
        Quality at the specific tube interval []
    rhol : float
        Density of the liquid [kg/m^3]
    rhog : float
        Density of the gas [kg/m^3]

    Returns
    -------
    alpha : float
        Void fraction (area of gas / total area of channel), [-]

    Notes
    -----
        
    Examples
    --------
    >>> Gregory_Scott(0.4, 800., 2.5)
    0.8364154370924108

    References
    ----------
    .. [1] Gregory, G. A., and D. S. Scott. "Correlation of Liquid Slug 
       Velocity and Frequency in Horizontal Cocurrent Gas-Liquid Slug Flow." 
       AIChE Journal 15, no. 6 (November 1, 1969): 933-35. 
       doi:10.1002/aic.690150623.
    .. [2] Xu, Yu, and Xiande Fang. "Correlations of Void Fraction for Two-
       Phase Refrigerant Flow in Pipes." Applied Thermal Engineering 64, no. 
       1-2 (March 2014): 242–51. doi:10.1016/j.applthermaleng.2013.12.032. 
    .. [3] Woldesemayat, Melkamu A., and Afshin J. Ghajar. "Comparison of Void 
       Fraction Correlations for Different Flow Patterns in Horizontal and 
       Upward Inclined Pipes." International Journal of Multiphase Flow 33, 
       no. 4 (April 2007): 347-370. doi:10.1016/j.ijmultiphaseflow.2006.09.004.
    '''
    C0 = 1.19
    return x/rhog*(C0*(x/rhog + (1-x)/rhol))**-1
def Gregory_Scott ( x , rhol , rhog ) : C0 = 1.19 return x / rhog * ( C0 * ( x / rhog + ( 1 - x ) / rhol ) ) ** - 1
r'''Calculates void fraction in two-phase flow according to the model of 
    [1]_ as given in [2]_ and [3]_.
    
    .. math::
        \alpha = \frac{x}{\rho_g}\left[C_0\left(\frac{x}{\rho_g} + \frac{1-x}
        {\rho_l}\right) +\frac{v_{gm}}{G} \right]^{-1}
        
    .. math::
        v_{gm} = 0

    .. math::
        C_0 = 1.19
        
    Parameters
    ----------
    x : float
        Quality at the specific tube interval []
    rhol : float
        Density of the liquid [kg/m^3]
    rhog : float
        Density of the gas [kg/m^3]

    Returns
    -------
    alpha : float
        Void fraction (area of gas / total area of channel), [-]

    Notes
    -----
        
    Examples
    --------
    >>> Gregory_Scott(0.4, 800., 2.5)
    0.8364154370924108

    References
    ----------
    .. [1] Gregory, G. A., and D. S. Scott. "Correlation of Liquid Slug 
       Velocity and Frequency in Horizontal Cocurrent Gas-Liquid Slug Flow." 
       AIChE Journal 15, no. 6 (November 1, 1969): 933-35. 
       doi:10.1002/aic.690150623.
    .. [2] Xu, Yu, and Xiande Fang. "Correlations of Void Fraction for Two-
       Phase Refrigerant Flow in Pipes." Applied Thermal Engineering 64, no. 
       1-2 (March 2014): 242–51. doi:10.1016/j.applthermaleng.2013.12.032. 
    .. [3] Woldesemayat, Melkamu A., and Afshin J. Ghajar. "Comparison of Void 
       Fraction Correlations for Different Flow Patterns in Horizontal and 
       Upward Inclined Pipes." International Journal of Multiphase Flow 33, 
       no. 4 (April 2007): 347-370. doi:10.1016/j.ijmultiphaseflow.2006.09.004.