An integral approach to simulate three-dimensional flow in and around a ventilated U-shaped chironomid dwelled burrow

Abstract

Tube dwelling of chironomids often dominates benthic communities in freshwater ecosystems with high population density and pumping rates. This strongly enhances exchange across the sediment-water interface and impacts biogeochemical processes. Such processes are investigated by tracking the flow initiated by chironomid’s pumping through and around burrows using laboratory and computer models. We used modeling and experimental results of other authors considering U-shaped burrows embedded in the sediment to improve process-understanding and prove the plausibility of an integral modeling approach. In contrast to coupled models of pipe (burrow), surface water (overlying water column) and groundwater flow (surrounding sediment), we present a novel high-resolution integral formulation for the porous medium-surface water domain (called porousInter as part of OpenFOAM (Open Field Operation and Manipulation)). This approach solves the extended version of the Navier-Stokes equations allowing simultaneous flow simulation in the burrow, the overlying water column and the surrounding sediment to better account for feedback effects between the sediment and surface water. Using similar model setup as of a coupled approach, we performed scenarios of flow through burrow and sediment triggered by pumping in the center of the burrow. Plausible agreement of our integral model with results of a coupled model and experimental results was obtained when comparing flow patterns around the burrows, between two burrow branches and at burrow inlet and outlet.

Keywords:

• Integral approach
• groundwater hydraulics
• numerical modeling
• feedback effects
• tube-dwelling invertebrates

Acknowledgments

This contribution was elaborated within project H2 of the interdisciplinary Research Training Group “Urban Water Interfaces” (UWI, RTG 2032/2) funded by the Deutsche Forschungsgemeinschaft (DFG). The project is located at the Technische Universität Berlin (TUB) and the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB). High performance computers (HPC) of TU Berlin were used during this project.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by German Research Foundation.