The numerical study shows that when the upwards-driven wetting front has reached the level of the bed surface of the 1.5 mm beach, a pathway is created to release the air, at a higher pressure than atmospheric pressure, entrapped within the beach. Entrapped air is then not only released through the unsaturated region of the beach beyond the shoreline position, but also through the additional flow paths created at the lower end of the beach, where the beach has returned to its initially unsaturated state.
beach
1.5 mm
mm