Initialize internal variable of Coronary BC

[mrp089]

For boundary conditions (BCs), I'll distinguish between external (on the interface between 3D and 0D model) and internal (inside the 0D model) unknowns.

RCR BCs have two (external) unknowns [P, Q]. They get exported every time step in the files

PHistRCR.dat.*
QHistRCR.dat.*

Coronary BCs have three unknowns [P, Q, V], where V is an internal unknown (e.g. volume of C_im). However, only the two external unknowns are exported every time step

PHistCOR.dat.*
QHistCOR.dat.*

There is a file PLvCOR.dat.*, but that just reports the intra-myocardial pressure that's prescribed in the input file.

This means that the Coronary BC is not exporting the internal unknown. I hypothesize that svSolver assumes that the internal variable is zero at time step zero. Consequently, when prescribing initial conditions, the internal variable of the Coronary BC is always initialized to zero. This severely slows convergence to a periodic state.

I will try the following to test this problem:

• doing a restart from a fictitious time history of P and Q instead of prescribing initial conditions
• use GenBC to recreate the Coronary BC and correctly initialize the internal variable

If these circumvent the problem, I will try to find a way to export and read in the internal variable. This would most certainly require rewriting the formulation of the Coronary BC. Currently, it does not explicitly compute this internal variable (as far as I know).