Incorrect value used to fill missing layers in angle1 array in NPF package

[JoerivanEngelen]

Bug description
Users do not have to set values for each layer for the ANI package in the projectfile. We have utilities to fill these missing layers with a constant value. Right now we use the incorrect value to fill missing layers: Should be 90, is 0 at the moment.

[Huite]

No, this is not the right approach!
By filling a default value of 90, MODFLOW 6 has do a great deal of unnecessary work. Unless I'm mistaken, this potentially results in expensive trigoniometric evaluations, potentially for each formulation!
You should do the trig in imod-python instead, and rotate the north bound iMOD5 kh to the eastbound MF6 k11.

[JoerivanEngelen]

Thanks @Huite for ringing the alarm on this one. The approach taken from iMOD5 in imod.mf6.NodePropertyFlow.from_imod5_data is suboptimal.

In my short description I did not make my priorities and scope of this issue clear:

This issue is a subissue of parent #1208. My idea for this one is to first reproduce iMOD5 input as much as possible (except when it would lead to lots of new code implementing perfidious things). I use this to see convert the LHM and run it to see if there are any noticeable differences and detect potential bugs in iMOD Python. In the current state of the code base, the implementation is already suboptimal and has the wrong default value for missing layers. Fixing this default value is as I proposed is trivial and at least makes things consistent with iMOD5, so we can avoid any doubt that differences might be caused by incorrect trigoniometric computations in iMOD Python. This is my top priority now.

In a follow-up issue, we can replace the current suboptimal implementation with a better one. This will be picked up when I've resolved #1208 and proven that iMOD Python does the right thing for the LHM in its conversion of iMOD5 data to MODFLOW6 data. (I think I'm nearly there). I'll open up a follow-up issue to optimize the NPF import.

[JoerivanEngelen]

I created #1397 to resolve the issues @Huite raised.