MULTIPHYSICS MODELING OF STRONGLY COUPLED HYDROLOGIC PHENOMENA

Coupled hydrologic systems commonly have contrasting physical properties and dynamical behavior. One indicator of such contrasts is the difference in response or residence times and fluxes through different components. This property, in addition to the difficulty of solving strongly coupled nonlinear equations has prevented wide-scale modeling of such natural phenomena, particularly in the way of using modeling as a predictive analysis tool. Until recently, such previous modeling studies have been based on codes developed mainly by academicians to handle specific problems. Simplifying assumptions regarding the governing equations are commonly made in order to make the problems more tractable but consequently making the problems less directly based on fundamental physics. With the advent of robust yet flexible commercial multiphysics numerical modeling software (e.g., FEMLAB, CFD-ACE), solving such problems with minimal simplifications becomes tenable. Additionally, turn-around times between model conceptualization and implementation, and result visualization and interpretation, are drastically reduced. This affords us the opportunity to study the dynamics of certain hydrologic systems that have traditionally been investigated through limited laboratory experiments, if at all. We review several multiphysics problems involving porous media and a second fluid-dynamical regime – including (1) air flow in caves surrounded by an unsaturated non-isothermal porous media, and (2) hyporheic flow through a water-saturated porous sediments underlying a current-driven water column. We explore this second problem in some detail, considering both laminar and turbulent water column flow, and “discharging” benthic groundwater.