def Erdim_Akgiray_Demir(dp, voidage, vs, rho, mu, L=1):
    r'''Calculates pressure drop across a packed bed of spheres using a
    correlation developed in [1]_, claiming to be the best model to date.

    .. math::
        f_v = 160 + 2.81Re_{Erg}^{0.904}

    .. math::
        f_v = \frac{\Delta P d_p^2}{\mu v_s L}\frac{\epsilon^3}{(1-\epsilon)^2}

    .. math::
        Re_{Erg} = \frac{\rho v_s  d_p}{\mu(1-\epsilon)}

    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
    -----
    Developed with data in the range of:

    .. math::
        2 < Re_{Erg} <3582\\
        4 < d_t/d_p < 34.1\\
        0.377 < \epsilon <0.470

    Examples
    --------
    >>> Erdim_Akgiray_Demir(dp=8E-4, voidage=0.4, vs=1E-3, rho=1E3, mu=1E-3)
    1438.2826958844414

    References
    ----------
    .. [1] 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.
    '''
    Rem = dp*rho*vs/mu/(1-voidage)
    fv = 160 + 2.81*Rem**0.904
    return fv*(mu*vs*L/dp**2)*(1-voidage)**2/voidage**3