- Number 413 |
- May 12, 2014
Several faces of physics become one
The unified multiscale model developed at
PNNL couples water transport equations in
such a way that this one model can
represent transport at both pore (top)
and watershed (bottom) scales.
Water moves through multifaceted physical boundaries, posing a significant challenge for scientists who must simulate water flow across many domains. Scientists at DOE’s Pacific Northwest National Laboratory (PNNL) conquered this challenge by merging different physical laws in a new approach that describes any type of water flow in soil pores, streams, lakes, rivers and oceans, and in mixed media of pores and solids for soil and aquifer. The versatile properties of the new approach allow cross-domain simulation of water flow at different scales.
From stream flow, to soil and irrigation saturation, to underground aquifers, understanding how water travels through many varied regions is important for understanding water cycling and its effect on agriculture, water conservation, and climate changes.
For scientists, the challenge is simulating water's travels through many different domains in ways that are efficient and effective. Soil consists of large spaces (macropore) where water easily flows and small spaces (micropore) where water drains and saturates slowly. Similarly, an ecosystem consists of open water bodies (lakes, rivers, and oceans) where water flow is less restricted, and aquifers (containing mixed water and solids) where water flow is resisted by collision with solids. Different domains mean different and repeated calculations for the physical trail.
The research team devised a new approach that eliminates repeated calculations at the domain interfaces, significantly simplifying water flow simulations for ecosystems. Their unified theory and unified multiscale model (UMSM) simulates water flow at all scales. The team performed extensive numerical verifications to evaluate the new model under both saturated and unsaturated conditions.
Using water flow in a soil core from Rattlesnake Mountain in south-central Washington State as an example, they validated the new model. Their numerical verification and experimental validation confirmed that the unified model performs well.
"By solving a single set of equations in all ecosystem components, UMSM presents a system-scale approach to analyze water cycling," said Dr. Chongxuan Liu, biogeochemist and corresponding author of the paper. "This approach will facilitate integration of ecosystem water flow in large, climate-scale modeling."
Next, UMSM directly simulates water flow across scales and physical domains in soils and ecosystems. The PNNL researchers are now extending UMSM to describe biogeochemical processes in soils and ecosystems that are coupled with water flow.This research was supported by DOE’s Office of Biological and Environmental Research through the Terrestrial Ecosystem Science program. Resources at EMSL, a DOE national scientific user facility located at PNNL, were used in the study.
[Kristin Manke, 509.372.6011,