The mass of liquid in a Simscape network may not closely match the mass of liquid in the real system even when the Simscape network behavior is very close to that of the real system, so be cautious if you try to calculate or set the fluid mass within the Simscape network.
Why is this? Some Simscape blocks have an internal volume and others do not. For example, the Flow Resistance (TL) and the Centrifugal Pump (TL) do not have internal volumes. Asking Simscape for the total fluid mass in the system would be likely to undershoot unless you added pipes/chambers to match the real system geometry. And these extra blocks might have undesireable effects on the overall system simulation goals. If you really need to calculate or set the mass of liquid in your system, I would personally recommend using a MATLAB live script. The script could calculate system initial conditions based on the desired fluid mass or calculate fluid mass based on logged internal node variables as hinted at by Yifeng earlier. In the script, you could precisely control the fluid mass accounting and also include additional geometric information from data sheets or CAD models.
