Question about units

[Alex-blip-sys]

Hello!

I was curious whether anyone could help me understand what units svsolver solves in with the .json files. I believe the documentation noted that it was cgs units, but does this extend to the pressure and resistance values? Specifically, I wanted to know whether someone could let me know what the units of Pressure, Elastance_max and min, and Resistance are in the .json file for the chamber_elastance_inductor.json (https://github.com/SimVascular/svZeroDSolver/blob/master/tests/cases/chamber_elastance_inductor.json)?
Thank you so much!

[mrp089]

As with any computational solver, there are no units. Everything is user-defined in the input file. Once you pick your unit system (e.g. CGS), you can derive all units from that. In CGS, that should be:

Quantity	Symbol	Formula	CGS Units
Resistance	$R$	$\Delta P / Q$	$\text{g}/(\text{cm}^4 \cdot \text{s})$
Capacitance	$C$	$\Delta V / \Delta P$	$\text{cm}^3 \cdot \text{s}^2 / \text{g}$
Inertance	$I$	$\Delta P / (dQ/dt)$	$\text{g}/\text{cm}^4$
Elastance	$E$	$1/C$	$\text{g}/(\text{cm}^3 \cdot \text{s}^2)$

[Alex-blip-sys]

Ah I see, thank you! So with the chamber_elastance_inductor.json test case, it was user defined. Would those values be in SI units then, or is there further documentation on the values from this particular test case? I was curious on where the values were obtained from. Thank you!