def dP_Reader_Harris_Gallagher_wet_venturi_tube(D, Do, P1, P2, ml, mg, rhol, 
                                                rhog, H=1):
    r'''Calculates the non-recoverable pressure drop of a wet gas venturi 
    nozzle based on the pressure drop and the geometry of the venturi nozzle,
    the mass flow rates of liquid and gas through it, the densities of the
    vapor and liquid phase, and an adjustable coefficient `H`.
    
    .. math::
        Y = \frac{\Delta \bar \omega}{\Delta P} - 0.0896 - 0.48\beta^9
        
    .. math::
        Y_{max} = 0.61\exp\left[-11\frac{\rho_{1,g}}{\rho_l}
        - 0.045 \frac{Fr_{gas}}{H}\right]
        
    .. math::
        \frac{Y}{Y_{max}} = 1 - \exp\left[-35 X^{0.75} \exp
        \left( \frac{-0.28Fr_{gas}}{H}\right)\right]
            
    .. math::
        X = \left(\frac{m_l}{m_g}\right) \sqrt{\frac{\rho_{1,g}}{\rho_l}}
        
    .. math::
        {Fr_{\text{gas, densiometric}}} = \frac{v_{gas}}{\sqrt{gD}}
        \sqrt{\frac{\rho_{1,g}}{\rho_l - \rho_{1,g}}}
        =  \frac{4m_g}{\rho_{1,g} \pi D^2 \sqrt{gD}}
        \sqrt{\frac{\rho_{1,g}}{\rho_l - \rho_{1,g}}}
        
    Parameters
    ----------
    D : float
        Upstream internal pipe diameter, [m]
    Do : float
        Diameter of venturi tube at flow conditions, [m]
    P1 : float
        Static pressure of fluid upstream of venturi tube at the cross-section 
        of the pressure tap, [Pa]
    P2 : float
        Static pressure of fluid downstream of venturi tube at the cross-
        section of the pressure tap, [Pa]
    ml : float
        Mass flow rate of liquid through the venturi tube, [kg/s]
    mg : float
        Mass flow rate of gas through the venturi tube, [kg/s]
    rhol : float
        Density of liquid at `P1`, [kg/m^3]
    rhog : float
        Density of gas at `P1`, [kg/m^3]
    H : float, optional
        A surface-tension effect coefficient used to adjust for different 
        fluids, (1 for a hydrocarbon liquid, 1.35 for water, 0.79 for water in 
        steam) [-]

    Returns
    -------
    C : float
        Coefficient of discharge of the wet gas venturi tube flow meter
        (includes flow rate of gas ONLY), [-]

    Notes
    -----
    The model was first published in [1]_, and became ISO 11583 later.
    
    Examples
    --------
    >>> dP_Reader_Harris_Gallagher_wet_venturi_tube(D=.1, Do=.06, H=1, 
    ... P1=6E6, P2=6E6-5E4, ml=5.31926/2, mg=5.31926, rhog=50.0, rhol=800.,)
    16957.43843129572
    
    References
    ----------
    .. [1] Reader-harris, Michael, and Tuv Nel. An Improved Model for 
       Venturi-Tube Over-Reading in Wet Gas, 2009. 
    .. [2] ISO/TR 11583:2012 Measurement of Wet Gas Flow by Means of Pressure 
       Differential Devices Inserted in Circular Cross-Section Conduits.
    '''
    dP = P1 - P2
    beta = Do/D
    X =  ml/mg*(rhog/rhol)**0.5

    V = 4*mg/(rhog*pi*D**2)
    Frg =  Froude_densimetric(V, L=D, rho1=rhol, rho2=rhog, heavy=False)

    Y_ratio = 1.0 - exp(-35.0*X**0.75*exp(-0.28*Frg/H))
    Y_max = 0.61*exp(-11.0*rhog/rhol - 0.045*Frg/H)
    Y = Y_max*Y_ratio
    rhs = -0.0896 - 0.48*beta**9
    dw = dP*(Y - rhs)
    return dw
r'''Calculates the non-recoverable pressure drop of a wet gas venturi 
    nozzle based on the pressure drop and the geometry of the venturi nozzle,
    the mass flow rates of liquid and gas through it, the densities of the
    vapor and liquid phase, and an adjustable coefficient `H`.
    
    .. math::
        Y = \frac{\Delta \bar \omega}{\Delta P} - 0.0896 - 0.48\beta^9
        
    .. math::
        Y_{max} = 0.61\exp\left[-11\frac{\rho_{1,g}}{\rho_l}
        - 0.045 \frac{Fr_{gas}}{H}\right]
        
    .. math::
        \frac{Y}{Y_{max}} = 1 - \exp\left[-35 X^{0.75} \exp
        \left( \frac{-0.28Fr_{gas}}{H}\right)\right]
            
    .. math::
        X = \left(\frac{m_l}{m_g}\right) \sqrt{\frac{\rho_{1,g}}{\rho_l}}
        
    .. math::
        {Fr_{\text{gas, densiometric}}} = \frac{v_{gas}}{\sqrt{gD}}
        \sqrt{\frac{\rho_{1,g}}{\rho_l - \rho_{1,g}}}
        =  \frac{4m_g}{\rho_{1,g} \pi D^2 \sqrt{gD}}
        \sqrt{\frac{\rho_{1,g}}{\rho_l - \rho_{1,g}}}
        
    Parameters
    ----------
    D : float
        Upstream internal pipe diameter, [m]
    Do : float
        Diameter of venturi tube at flow conditions, [m]
    P1 : float
        Static pressure of fluid upstream of venturi tube at the cross-section 
        of the pressure tap, [Pa]
    P2 : float
        Static pressure of fluid downstream of venturi tube at the cross-
        section of the pressure tap, [Pa]
    ml : float
        Mass flow rate of liquid through the venturi tube, [kg/s]
    mg : float
        Mass flow rate of gas through the venturi tube, [kg/s]
    rhol : float
        Density of liquid at `P1`, [kg/m^3]
    rhog : float
        Density of gas at `P1`, [kg/m^3]
    H : float, optional
        A surface-tension effect coefficient used to adjust for different 
        fluids, (1 for a hydrocarbon liquid, 1.35 for water, 0.79 for water in 
        steam) [-]

    Returns
    -------
    C : float
        Coefficient of discharge of the wet gas venturi tube flow meter
        (includes flow rate of gas ONLY), [-]

    Notes
    -----
    The model was first published in [1]_, and became ISO 11583 later.
    
    Examples
    --------
    >>> dP_Reader_Harris_Gallagher_wet_venturi_tube(D=.1, Do=.06, H=1, 
    ... P1=6E6, P2=6E6-5E4, ml=5.31926/2, mg=5.31926, rhog=50.0, rhol=800.,)
    16957.43843129572
    
    References
    ----------
    .. [1] Reader-harris, Michael, and Tuv Nel. An Improved Model for 
       Venturi-Tube Over-Reading in Wet Gas, 2009. 
    .. [2] ISO/TR 11583:2012 Measurement of Wet Gas Flow by Means of Pressure 
       Differential Devices Inserted in Circular Cross-Section Conduits.