def circle(target, pore_diameter='pore.diameter'):
    """
    Calculate cross-sectional area assuming the pore body is a circle

    Only suitable for true 2D simulations

    Parameters
    ----------
    target : OpenPNM Geometry Object
        The Geometry object which this model is associated with. This controls
        the length of the calculated array, and also provides access to other
        necessary geometric properties.

    pore_diameter : string
        The dictionary key of the array on the Geometry object containing the
        pore diameter values necessary to find the area.

    """
    return target[pore_diameter]
