     <span class="keyword">case</span> 1 <span class="comment">% coarse fractures constraints the coarse dual grid</span>
            coarseGrid = cell(1,1);
            coarseGrid{1} = fset{1};
            coarseGrid{1}.merge = true;
            coarseGrid{1}.apertureType = <span class="string">'constants'</span>;
            fineGrid = cell(2,1);
            fineGrid{2} = fset{2};
            fineGrid{1} = fset{3};
        <span class="keyword">case</span> 2 <span class="comment">% the Cartesian grid is u