Frehg stands for Fine Resolution Environmental Hydrodynamic and Groundwater model. It is a coupled 2D depth-integrated hydrodynamic and 3D variably-saturated groundwater model.
Currently the Frehg model is still under development. As of 2021-10, the capabilities of Frehg includes:
- Simulate overland flow with either 2D depth-integrated Navier-Stokes equations, or a diffusive wave approximation of the shallow water equation.
- Simulate overland flow on coarse grids with subgrid-scale topography.
- Simulate 3D variably-saturated groundwater flow with the predictor-corrector method.
- Simulate coupled surface-subsurface flow under prescribed tidal elevation, river stage, inflow, wind, rainfall and evaporation rates.
- Simulate transport of passive scalars in both surface and subsurface domains.
- Simulate density-driven transport of scalars in the subsurface domain.
- Parallel simulation with MPI.
The hydrodynamic part of Frehg is built based on:
Li, Z., Hodges, B.R. (2019) Model instability and channel connectivity for 2D coastal marsh simulations. Environ Fluid Mech 19, 1309–1338 doi:10.1007/s10652-018-9623-7
Li, Z., Hodges, B.R. (2019) Modeling subgrid-scale topographic effects on shallow marsh hydrodynamics and salinity transport. Adv. Water Resour (129), 1-15 doi:10.1016/j.advwatres.2019.05.004
The variably-saturated groundwater part of Frehg is built based on:
Li, Z., Ozgen, I. and Maina, F.Z., (2020), A mass-conservative predictor-corrector solution to the 1D Richards equation with adaptive time control, Journal of Hydrology (592)125809, doi:10.1016/j.jhydrol.2020.125809
The following figure validates the frehg model against benchmark problems (rainfall-runoff on a sloping plane) used by Sulis(2010). The frehg model produces similar results with the CATHY and ParFlow models.
A brief user manual and a sample problem can be found in this repository.