def specific_area_mesh(voidage, d):
    """Calculates the specific area of a wire mesh, as used in demisters or
    filters. Shown in [1]_, and also self-evident and non-empirical.
    Makes the ideal assumption that wires never touch.

    .. math::
        S = \\frac{4(1-\\epsilon)}{d_{wire}}

    Parameters
    ----------
    voidage : float
        Voidage of the mesh []
    d : float
        Diameter of the wires making the mesh, [m]

    Returns
    -------
    S : float
        Specific area of the mesh [m^2/m^3]

    Notes
    -----
    Should be preferred over manufacturer data. Can also be used to show that
    manufacturer's data is inconsistent with their claimed voidage and wire
    diameter.

    Examples
    --------
    >>> specific_area_mesh(voidage=.934, d=3e-4)
    879.9999999999994

    References
    ----------
    .. [1] Helsør, T., and H. Svendsen. "Experimental Characterization of
       Pressure Drop in Dry Demisters at Low and Elevated Pressures." Chemical
       Engineering Research and Design 85, no. 3 (2007): 377-85.
       doi:10.1205/cherd06048.
    """
    return 4 * (1 - voidage) / d
