Grid and time awareness

[wpbonelli]

A good first step toward #113 might be attaching Grid and ModelTime to models and simulations, respectively. I think we could have the grid as an extra attrs.field on the model class (likewise for time), so it becomes an init method parameter, but is ignored by xattree. update: this has been implemented

We also have the grid and time discretizations encoded as dimensions/coordinates in the backing data tree. This gives us alignment but we aren't taking full advantage yet of xarray's extension points.

Eventually I think we want

• an xarray index, which accepts a flopy grid as an init param
• an xarray accessor, a la xugrid's .ugrid, which exposes grid info in an xarray way

We could call the accessor .grid, so it's distinct from .ugrid. But it might use xugrid under the hood and/or redirect to .ugrid.

This way, models have a .grid which is the flopy.discretization.Grid, and the datatree .data also has a grid .data.grid which exposes grid-aware indexing, selection, plotting, etc. You choose between them as the situation calls for it.

[wpbonelli]

@mjreno I can work on the xarray side of things, maybe you can have a look at adding the initial grid/time attributes? It might come in handy for the plotting?

[mjreno]

Sounds good @wpbonelli I've started looking at an adapter that implements ModelInterface which that could dovetail nicely with.

[wpbonelli]

grid/time attributes are in.

[wpbonelli]

As we have some preliminary support for flopy3 Grid and ModelTime I'm going to close this and make separate issues for the xarray index and accessor