Delft3D-FLOW models require hydrodynamic and transport boundary conditions. In case the boundary conditions of a model are generated by a larger (overall) model we speak of a nested model. Nesting in Delft3D-FLOW is executed in three steps, using two separate utilities and the Delft3D-FLOW program. This manual describes the steps to generate boundary conditions for a nested Delft3D-FLOW model.
In principle, the nested boundary conditions are generated by bi-linear interpolation of computational results at monitoring stations of the overall model.
The procedure to generate nested boundary conditions consists of 3 steps:
1. Using the tool NESTHD1 a list of monitoring stations in the overall model, needed for the interpolation, can be generated. In addition to this, the program generates the nesting administration, i.e. the link between the boundary support points in the nested model and the monitoring stations in the overall model.
2. Run the overall model with the list of monitoring stations generated by NESTHD1.
3. The actual boundary conditions for the nested model are generated by NESTHD2 using the history file of the overall model and the nest administration.
Restrictions:
At present, the nesting programs have the following limitations:
1. Both model grids must be supplied in a grid file and must be defined in the same co-ordinate system.
2. Hydrodynamic boundary conditions are of the water level or (perpendicular) velocity type. Discharge and Riemann boundary conditions are not implemented yet.
3. The boundary definition of the nested model has to be supplied as an attribute file.
4. Temporary dry points in the overall model are not taken into account in the nesting programs.
5. For a nested 3D model the number and the thickness of the layers must be identical to the overall model.
6. The generated boundary conditions are written to a time-series file. This implies that the reference date of a simulation with the nested model must be identical to the reference date of the overall model simulation used to generate the boundary conditions.