Multiphase Modeling of Hydrosystems Using OpenFOAM

This paper presents three computational fluid dynamics applications regarding multiphase modeling of hydro systems with the open source software OpenFOAM. The first model investigates flow processes of groundwater and surface water using an integral approach which solves the three-dimensional Navier–Stokes equations, extended by the consideration of porosities. For the validation, seepages through homogeneous dams with impervious foundations were compared with analytical and numerical solutions. A further application examines the water–air interface in sewer systems.The focus of the model lies on the description of in-sewer water–air flow and transformation processes, reaeration and hydrogen sulfide emission which highly depend on the three-dimensionality of the hydraulic behavior in the closed duct. A test case analyzing the hydraulic behavior in a sewer stretch showed a good agreement of the numerical results with measured water levels. In the third model, fluid–structure interaction is investigated applying FOAM Extend Project. Calculations of the fluid phase are linked with the solid phase via a coupling algorithm to achieve an equilibrium state. To describe the time-varying position of the fluid boundary, caused by the structural response, dynamic meshes are considered. A technical case, consisting of the air flow around a thin tower as well as a natural case, describing the water flow around aquatic vegetation and its response, were examined.