Pore-scale model factory

[ma-sadeghi]

The idea is to write a method that serves as a factory for pore-scale models. For instance, let's say you want to use a peculiar rate equation as source term, but don't want to bother writing an actual OpenPNM-compatible pore-scale model. Here's the API that I had in mind:

def my_peculiar_rate_eqn(c_A, c_B, T):
    return (c_A + c_B)**2 * np.exp(T/500)

from openpnm.models.misc import model_builder
custom_rate_model = model_builder(func=my_peculiar_rate_eqn,
                                  c_A="pore.c_A",
                                  c_B="pore.c_B",
                                  T="pore.temperature")
phys.add_model(propname="pore.rxn", model=custom_rate_model)

This is sort of related to issue #653. Although it only seems like a wrapper, I think it makes it easier for writing custom pore-scale models, especially for those less experienced in OpenPNM.

[ma-sadeghi]

Another convenience that could come with this model factory is doing proper mapping based on which object on which the model is added, which is usually something that most beginners.

[jgostick]

I think I see some value here. I'm going to reopen it and add it to future enhancements.

[jgostick]

Given that our new philosophy is the keep things simple and stop adding frills just for the thrills, I think we should forget about this. There is ample instruction on how to create a pore-scale model in the docs now.