Analytical Inlet Module

[nlaing613]

This issue is intended to create an inlet geometry analysis tool, connecting freestream conditions with the usable StanShock domain via an outputted boundary condition. It will use method of characteristics/2D analytical solutions from compressible flow to compute properties at the inlet exit.

[nlaing613]

@TimothyEDawson

Hey Tim,

I'm curious if you have any ideas for how to better handle the "Feature" class I've made. 

Right now, this class is initialized by:

1. Initial flow state (T, P, Mach, theta, gamma (from Cantera)).
2. Feature start location (x, y), identified from Geometry.inflections.x and Geometry.inflections.y
3. New flow angle, identified from Geometry.inflections.slope (serves as an input for the feature_generator)
4. Wall type (upper/lower)

After running feature_generator (which right now only works for walls), the Feature will store:

1. Post-feature flow state (computed)
2. Characteristic angle sigma (flipped appropriately depending on the wall)

The major shortcoming of this method is that there's no clear way to implement a 2D Riemann problem. Although there is a Wall class in Geometry, I wouldn't want to instantiate a Wall from a slipstream, even though in some ways it clear defines a boundary across which M, T, rho, and entropy are discontinuous.

An alternative would be to assign the slipstream angle (currently crudely solved for in examples/inlet_testing/shock_shock_soln.py) to the Feature's sigma/characteristic angle, but then having upper/lower states could get a little bit messy.

Right now, I'm considering renaming the Feature class to a Wave class. Waves can be instantiated from a wall inflection point or from the intersection of characteristic lines/shocks and instead of having a "wall_type" would be classified as left-running or right-running.

The same logic for wall and slope changes to determine if the feature is a shock or fan (as found in src/utils/feature_generator) could be refactored to produce a Wave instantiation with the appropriate left/right running property.

This classification comes from Sections 4.8/4.9 of Anderson's Comp. Flow book (pg. 122 in my edition).

I'll keep working on this but if you can think of a better way to fix this I'd love to hear it.

Thanks,
Nathan