def K_motionless_mixer(K, L, D, fd):
    """Calculates loss coefficient of a motionless mixer with a regression
    parameter in [1]_ and originally in [2]_.

    .. math::
        K = K_{L/T}f\\frac{L}{D}

    Parameters
    ----------
    K : float
        Correlation parameter specific to a mixer's design, [-]
        Also specific to laminar or turbulent regime.
    L : float
        Length of the motionless mixer [m]
    D : float
        Diameter of pipe [m]
    fd : float
        Darcy friction factor [-]

    Returns
    -------
    K : float
        Loss coefficient of mixer [-]

    Notes
    -----
    Related to example 7-8.3.2 in [1]_.

    Examples
    --------
    >>> K_motionless_mixer(K=150, L=.762*5, D=.762, fd=.01)
    7.5

    References
    ----------
    .. [1] Paul, Edward L, Victor A Atiemo-Obeng, and Suzanne M Kresta.
       Handbook of Industrial Mixing: Science and Practice.
       Hoboken, N.J.: Wiley-Interscience, 2004.
    .. [2] Streiff, F. A., S. Jaffer, and G. Schneider (1999). Design and
       application of motionless mixer technology, Proc. ISMIP3, Osaka,
       pp. 107-114.
    """
    return L / D * fd * K
