def Kuo_Nydegger(dp, voidage, vs, rho, mu, L=1):
    """Calculates pressure drop across a packed bed of spheres using a
    correlation developed in [1]_, as shown in [2]_ and [3]. Thirty-eighth most
    accurate correlation overall in the review of [2]_.

    .. math::
        f_p = \\left(276.23 + 5.05\\left(\\frac{Re}{1-\\epsilon}\\right)^{0.87}
        \\right)\\frac{(1-\\epsilon)^2}{\\epsilon^3 Re}

    .. math::
        f_p = \\frac{\\Delta P d_p}{\\rho v_s^2 L}

    .. math::
        Re = \\frac{\\rho v_s  d_p}{\\mu}

    Parameters
    ----------
    dp : float
        Particle diameter of spheres [m]
    voidage : float
        Void fraction of bed packing [-]
    vs : float
        Superficial velocity of the fluid (volumetric flow rate/cross-sectional 
        area)[m/s]
    rho : float
        Density of the fluid [kg/m^3]
    mu : float
        Viscosity of the fluid, [Pa*s]
    L : float, optional
        Length the fluid flows in the packed bed [m]

    Returns
    -------
    dP : float
        Pressure drop across the bed [Pa]

    Notes
    -----
    Validity range shown in [2]_ as for a range of
    :math:`460 < Re < 14600`.
    :math:`0.3760 < \\epsilon < 0.3901`.
    Developed with data from rough granular ball propellants beds, with air.

    Examples
    --------
    >>> Kuo_Nydegger(dp=8E-1, voidage=0.4, vs=1E-3, rho=1E3, mu=1E-3)
    0.025651460973648624

    References
    ----------
    .. [1] Kuo, K. K. and Nydegger, C., "Flow Resistance Measurement and
       Correlation in Packed Beds of WC 870 Ball Propellants," Journal of
       Ballistics , Vol. 2, No. 1, pp. 1-26, 1978.
    .. [2] Erdim, Esra, Ömer Akgiray, and İbrahim Demir. "A Revisit of Pressure
       Drop-Flow Rate Correlations for Packed Beds of Spheres." Powder
       Technology 283 (October 2015): 488-504. doi:10.1016/j.powtec.2015.06.017.
    .. [3] Jones, D. P., and H. Krier. "Gas Flow Resistance Measurements
       Through Packed Beds at High Reynolds Numbers." Journal of Fluids
       Engineering 105, no. 2 (June 1, 1983): 168-172. doi:10.1115/1.3240959.
    """
    Re = dp * rho * vs / mu
    fp = (276.23 + 5.05 * (Re / (1 - voidage)) ** 0.87) * (1 - voidage
        ) ** 2 / (voidage ** 3 * Re)
    return fp * rho * vs ** 2 * L / dp
