Hi Federico,
For the block you mentioned, tabulated data or polynomial coefficients (which will require some data fitting) are the only options. I understand sometime it's expensive to get these from CFD simulations.
If you are open to use the newer (and better) isothermal liquid domain, instead of the hydraulic domain (you should!), there is another module that may help:
This block allows you to provide one set of operation condition, which can be easier to get from one CFD run, and it'll extrapolate to other conditions using analytical formula.
You may also try to contact MathWorks support or sales team to get additional help.
