def Lockhart_Martinelli(m, x, rhol, rhog, mul, mug, D, L=1, Re_c=2000):
    r'''Calculates two-phase pressure drop with the Lockhart and Martinelli
    (1949) correlation as presented in non-graphical form by Chisholm (1967).

    .. math::
        \Delta P = \Delta P_{l} \phi_{l}^2

    .. math::
        \phi_l^2 = 1 + \frac{C}{X} + \frac{1}{X^2}

    .. math::
        X^2 = \frac{\Delta P_l}{\Delta P_g}

    +---------+---------+--+
    |Liquid   |Gas      |C |
    +=========+=========+==+
    |Turbulent|Turbulent|20|
    +---------+---------+--+
    |Laminar  |Turbulent|12|
    +---------+---------+--+
    |Turbulent|Laminar  |10|
    +---------+---------+--+
    |Laminar  |Laminar  |5 |
    +---------+---------+--+

    This model has its own friction factor calculations, to be consistent with
    its Reynolds number transition and the procedure specified in the original
    work. The equation 64/Re is used up to Re_c, and above it the Blasius
    equation is used as follows:

    .. math::
        f_d = \frac{0.184}{Re^{0.2}}

    Parameters
    ----------
    m : float
        Mass flow rate of fluid, [kg/s]
    x : float
        Quality of fluid, [-]
    rhol : float
        Liquid density, [kg/m^3]
    rhog : float
        Gas density, [kg/m^3]
    mul : float
        Viscosity of liquid, [Pa*s]
    mug : float
        Viscosity of gas, [Pa*s]
    D : float
        Diameter of pipe, [m]
    L : float, optional
        Length of pipe, [m]
    Re_c : float, optional
        Transition Reynolds number, used to decide which friction factor
        equation to use and which C value to use from the table above.

    Returns
    -------
    dP : float
        Pressure drop of the two-phase flow, [Pa]

    Notes
    -----
    Developed for horizontal flow. Very popular. Many implementations of this
    model assume turbulent-turbulent flow.

    The original model proposed that the transition Reynolds number was 1000
    for laminar flow, and 2000 for turbulent flow; it proposed no model
    for Re_l < 1000 and Re_g between 1000 and 2000 and also Re_g < 1000 and
    Re_l between 1000 and 2000.

    No correction is available in this model for rough pipe.

    [3]_ examined the original data in [1]_ again, and fit more curves to the
    data, separating them into different flow regimes. There were 229 datum
    in the turbulent-turbulent regime, 9 in the turbulent-laminar regime, 339
    in the laminar-turbulent regime, and 42 in the laminar-laminar regime.
    Errors from [3]_'s curves were 13.4%, 3.5%, 14.3%, and 12.0% for the above
    regimes, respectively. [2]_'s fits provide further error.

    Examples
    --------
    >>> Lockhart_Martinelli(m=0.6, x=0.1, rhol=915., rhog=2.67, mul=180E-6,
    ... mug=14E-6, D=0.05, L=1)
    716.4695654888484

    References
    ----------
    .. [1] Lockhart, R. W. & Martinelli, R. C. (1949), "Proposed correlation of
       data for isothermal two-phase, two-component flow in pipes", Chemical
       Engineering Progress 45 (1), 39-48.
    .. [2] Chisholm, D."A Theoretical Basis for the Lockhart-Martinelli
       Correlation for Two-Phase Flow." International Journal of Heat and Mass
       Transfer 10, no. 12 (December 1967): 1767-78.
       doi:10.1016/0017-9310(67)90047-6.
    .. [3] Cui, Xiaozhou, and John J. J. Chen."A Re-Examination of the Data of
       Lockhart-Martinelli." International Journal of Multiphase Flow 36, no.
       10 (October 2010): 836-46. doi:10.1016/j.ijmultiphaseflow.2010.06.001.
    .. [4] Kim, Sung-Min, and Issam Mudawar. "Universal Approach to Predicting
       Two-Phase Frictional Pressure Drop for Adiabatic and Condensing Mini/
       Micro-Channel Flows." International Journal of Heat and Mass Transfer
       55, no. 11-12 (May 2012): 3246-61.
       doi:10.1016/j.ijheatmasstransfer.2012.02.047.
    '''
    def friction_factor(Re):
        # As in the original model
        if Re < Re_c:
            return 64./Re
        else:
            return 0.184*Re**-0.2

    v_l = m*(1-x)/rhol/(pi/4*D**2)
    Re_l = Reynolds(V=v_l, rho=rhol, mu=mul, D=D)
    v_g = m*x/rhog/(pi/4*D**2)
    Re_g = Reynolds(V=v_g, rho=rhog, mu=mug, D=D)

    if Re_l < Re_c and Re_g < Re_c:
        C = 5.0
    elif Re_l < Re_c and Re_g >= Re_c:
        # Liquid laminar, gas turbulent
        C = 12.0
    elif Re_l >= Re_c and Re_g < Re_c:
        # Liquid turbulent, gas laminar
        C = 10.0
    else: # Turbulent case
        C = 20.0

    fd_l = friction_factor(Re=Re_l)
    dP_l = fd_l*L/D*(0.5*rhol*v_l**2)
    fd_g = friction_factor(Re=Re_g)
    dP_g = fd_g*L/D*(0.5*rhog*v_g**2)

    X = (dP_l/dP_g)**0.5

    phi_l2 = 1 + C/X + 1./X**2
    return dP_l*phi_l2
r'''Calculates two-phase pressure drop with the Lockhart and Martinelli
    (1949) correlation as presented in non-graphical form by Chisholm (1967).

    .. math::
        \Delta P = \Delta P_{l} \phi_{l}^2

    .. math::
        \phi_l^2 = 1 + \frac{C}{X} + \frac{1}{X^2}

    .. math::
        X^2 = \frac{\Delta P_l}{\Delta P_g}

    +---------+---------+--+
    |Liquid   |Gas      |C |
    +=========+=========+==+
    |Turbulent|Turbulent|20|
    +---------+---------+--+
    |Laminar  |Turbulent|12|
    +---------+---------+--+
    |Turbulent|Laminar  |10|
    +---------+---------+--+
    |Laminar  |Laminar  |5 |
    +---------+---------+--+

    This model has its own friction factor calculations, to be consistent with
    its Reynolds number transition and the procedure specified in the original
    work. The equation 64/Re is used up to Re_c, and above it the Blasius
    equation is used as follows:

    .. math::
        f_d = \frac{0.184}{Re^{0.2}}

    Parameters
    ----------
    m : float
        Mass flow rate of fluid, [kg/s]
    x : float
        Quality of fluid, [-]
    rhol : float
        Liquid density, [kg/m^3]
    rhog : float
        Gas density, [kg/m^3]
    mul : float
        Viscosity of liquid, [Pa*s]
    mug : float
        Viscosity of gas, [Pa*s]
    D : float
        Diameter of pipe, [m]
    L : float, optional
        Length of pipe, [m]
    Re_c : float, optional
        Transition Reynolds number, used to decide which friction factor
        equation to use and which C value to use from the table above.

    Returns
    -------
    dP : float
        Pressure drop of the two-phase flow, [Pa]

    Notes
    -----
    Developed for horizontal flow. Very popular. Many implementations of this
    model assume turbulent-turbulent flow.

    The original model proposed that the transition Reynolds number was 1000
    for laminar flow, and 2000 for turbulent flow; it proposed no model
    for Re_l < 1000 and Re_g between 1000 and 2000 and also Re_g < 1000 and
    Re_l between 1000 and 2000.

    No correction is available in this model for rough pipe.

    [3]_ examined the original data in [1]_ again, and fit more curves to the
    data, separating them into different flow regimes. There were 229 datum
    in the turbulent-turbulent regime, 9 in the turbulent-laminar regime, 339
    in the laminar-turbulent regime, and 42 in the laminar-laminar regime.
    Errors from [3]_'s curves were 13.4%, 3.5%, 14.3%, and 12.0% for the above
    regimes, respectively. [2]_'s fits provide further error.

    Examples
    --------
    >>> Lockhart_Martinelli(m=0.6, x=0.1, rhol=915., rhog=2.67, mul=180E-6,
    ... mug=14E-6, D=0.05, L=1)
    716.4695654888484

    References
    ----------
    .. [1] Lockhart, R. W. & Martinelli, R. C. (1949), "Proposed correlation of
       data for isothermal two-phase, two-component flow in pipes", Chemical
       Engineering Progress 45 (1), 39-48.
    .. [2] Chisholm, D."A Theoretical Basis for the Lockhart-Martinelli
       Correlation for Two-Phase Flow." International Journal of Heat and Mass
       Transfer 10, no. 12 (December 1967): 1767-78.
       doi:10.1016/0017-9310(67)90047-6.
    .. [3] Cui, Xiaozhou, and John J. J. Chen."A Re-Examination of the Data of
       Lockhart-Martinelli." International Journal of Multiphase Flow 36, no.
       10 (October 2010): 836-46. doi:10.1016/j.ijmultiphaseflow.2010.06.001.
    .. [4] Kim, Sung-Min, and Issam Mudawar. "Universal Approach to Predicting
       Two-Phase Frictional Pressure Drop for Adiabatic and Condensing Mini/
       Micro-Channel Flows." International Journal of Heat and Mass Transfer
       55, no. 11-12 (May 2012): 3246-61.
       doi:10.1016/j.ijheatmasstransfer.2012.02.047.