2014 NGWA Groundwater Summit

May 04 - 07, 2014

Twilight Session: Dynamics of Groundwater Flow

In subsurface fluid mechanics there exists a dichotomy as to the description of forces driving subsurface fluids. On the one hand there is the application of velocity potentials [energy/unit volume] within engineering hydraulics which assumes water to be incompressible amongst other assumptions. Alternately there is the application of force potentials [energy/unit mass] and groundwater flow systems theory in groundwater dynamics incorporating water as compressible fluids. The difference between the two concepts may appear academic to some. It manifests, however, the fundamental differences between a purely mathematical treatment by engineering hydraulics, and the physically-based approach involving force potentials. The presentation explains both systems and addresses the fundamental differences between the two approaches. They extend to the treatment of hydraulic forces, buoyancy, buoyancy reversal, overpressure, and variable density flow, as well as their implementations within oil field simulators and, in part, groundwater model codes such as MODFLOW and FEFLOW.