@@ -129,6 +129,26 @@ Select the bed elevation (z) variable and click on "Create plot". Set up the axi
The bed elevation is assumed not to change in time, and therefore you don't have a temporal dimension to advance through. However, if you plot the water depth (h), or water surface elevation (h+z) or velocity variables (u, v) they are time dependant. Check out how the other variables look, and advance them in time.
Note that there is nothing actually happening in this simulation. The still water remains still.
This is because
1. the initial condition was one of still water
2. there is no forcing through the boundaries
3. there is no forcing through source or sink terms
Nonetheless, it is important to highlight that still water equilibrium is a very important property of the numerical scheme signalling well-balancing between the fluxes and source terms in the numerical solver.
### Run the full simulation
Now we want to run the full simulation, with boundaries which model the incoming tsunami wave. For this we need to create the `extbc.input` file (`extbc` stands for external boundary conditions).
Details on how to setup boundary conditions are in the [SERGHEI BC wiki page](https://gitlab.com/serghei-model/serghei/-/wikis/User-Guide/Boundary-conditions).
We need to devine a single boundary, which we may call `inlet`. We wish to define an **inflow stage hydrograph**, i.e., a time series of water surface elevations (t, h+z). You therefore need to include the relevant `bctype` code for this. `direction` indicates the inflow direction of the hydrograph in a unit vector fashion, i.e., `1.0 1.0` would mean a 45 degree angle (North-East), `-1, 0` would mean a 180 degree angle (South).
Finally, the `polygon` and `hydrograph` entries require the name of the polygon file which defines where to find the boundary, and the file containing the stage hydrograph (i.e., `wave.input`).
Try to build the polygon file to capture the west boundary, where the tsunami wave should come from, flowing eastwards.
Once all this is setup, run the simulation again and visualise the results again. If everything is set correctly, results at the end of the simulation should look like this
