The problem domain is fluid dynamics so enter the Kv and Cv values.
Technically these are a measure of volumetric flow. For instance, Kv is defined as:
the flow of water with temperature ranging 5 - 30 oC through a valve in cubic meters per hour (m3/h) with a pressure drop of 1 bar
The problem is that engineers see this as a "unitless" value and treat it as having no units at all. They use Kv in SI based equations, not m3/s as we'd expect. Thus all equations being fed to us use Kv as if it were a natural part of the equation.
Most of the time these dimensions do not compute dimensionally anyway but there's rare cases when they do. I have gotten the engineers (those giving me specs for code I write) to decide on Kv instead of doing both Kv and Cv (it's a basic conversion).
It's a little hard to see where the problem is without a concrete example. How about one equation and the corresponding function, with ancillary information about the expected units of inputs/output? Matthias