(a) A typical 3D cubic pore network. The lattice constant, ℓ, compared to the size of the throats and chambers, is shown expanded. The thick arrow indicates the direction of the macroscopic flow, (b) The pore network cubic lattice with one main diagonal parallel to the macroscopic flow direction. The two parallel equilateral triangles are perpendicular to the macroscopic flow, (c) Equilateral triangles align to form a checker-board pattern and exactly fill any frontal area perpendicular to the macroscopic flow.