A numerical investigation of free surface—Seepage face relationship under steady state flow conditions

The relationship between free surface and seepage face under steady conditions of flow has been analyzed for radial and planar flow configurations. The numerical studies, carried out with a saturated‐unsaturated flow model, included the simulation of a series of experimental observations documented by Hall (1955). The numerical analysis took into consideration effects of capillary fringe, model geometry, as well as converging and diverging patterns of flow. For the control series of three cases studied, discharge rates, free surface location, seepage face height and the spatial distribution of potentials closely matched the experimental observations. Additional parametric studies showed that converging patterns of flow favor more pronounced development of seepage face than divergent flows. In two‐dimensional planar flow, larger drawdowns tend to favor relatively more pronounced development of seepage face. Comparison of the detailed simulation results (taking unsaturated flow into consideration) with results generated using Dupuit‐Forchheimer assumptions suggest that the latter may provide discharge estimates that are in error by 12 to 20% both for radial and for two‐dimensional planar flows.