Kästner et al. (2026) Physically consistent modelling of the flow resistance across the laminar-turbulent transition allows for efficient computation of zero-inertia overland flow

Identification

• Journal: Advances in Water Resources
• Year: 2026
• Date: 2026-07-03
• Authors: Karl Kästner, Daniel Caviedes‐Voullième
• DOI: 10.1016/j.advwatres.2026.105370

Research Groups

• Hydrology, Brandenburg University of Technology Cottbus-Senftenberg (Germany)
• Chair for Environmental Fluid Dynamics and Modelling, TUD Dresden University of Technology (Germany)
• Simulation and Data Lab Terrestrial Systems, Institute of Bio- and Geosciences: Agrosphere and Jülich Supercomputing Centre (Germany)

Short Summary

This study proposes a physically consistent model for the flow resistance across the laminar-turbulent transition in overland flow, allowing for efficient computation of zero-inertia flow. The new model combines linear and quadratic flow resistance relations, facilitating a gradual transition between the two regimes.

Objective

• Investigate the effect of flow regime on the numerical integration of the Zero-Inertia Equation (ZIE) for overland flow.
• Develop a physically consistent model for the laminar-turbulent transition in overland flow.

Study Configuration

• Spatial Scale: Hillslope scale, with a spatial resolution of 1 m.
• Temporal Scale: High temporal resolution of 1 minute, over a period of 10 years.

Methodology and Data

• Models used: Finite volume discretization of the ZIE, combined flow resistance model.
• Data sources: Satellite data, observation data, reanalysis data (not specified).

Main Results

• The new combined flow resistance model resolves the singularity of the ZIE with quadratic flow resistance when water comes to rest.
• The model facilitates efficient numerical integration of the ZIE for small surface slopes.
• The celerity and diffusion of waves in the laminar-turbulent transition are asymptotically approached by the values for turbulent and laminar flow, respectively.

Contributions

• This study provides a physically consistent model for the laminar-turbulent transition in overland flow, allowing for efficient computation of zero-inertia flow.
• The new model resolves the singularity of the ZIE with quadratic flow resistance when water comes to rest.

Funding

• Not specified.

Citation

@article{Kästner2026Physically,
  author = {Kästner, Karl and Caviedes‐Voullième, Daniel},
  title = {Physically consistent modelling of the flow resistance across the laminar-turbulent transition allows for efficient computation of zero-inertia overland flow},
  journal = {Advances in Water Resources},
  year = {2026},
  doi = {10.1016/j.advwatres.2026.105370},
  url = {https://doi.org/10.1016/j.advwatres.2026.105370}
}