are the two tank at the same levels? If so, you need to change the initial value (open the block and click on the Initialization tab)

The fluid level on each tank is different. In the first tank we have 1.5m and in the second 1m.
So we had already change the initial value.
We are looking for the unsteady solution : if we impose different initial levels in the two tanks, we expect that the solution is an oscilation of the fluid level, until the viscosity plays it's role and damps the oscilations.
To get this unsteady behaviour, Modelica should take into account kinetic energy in the impulse balance equation and default option is to neglect this.

Cf
https://www.maplesoft.com/documentation … ssels.html
where it is said "Heights of ports as well as kinetic and potential energy of fluid enering or leaving are not taken into account anymore".
In the open tank model.

I cannot believe that it does not exist a possibility to take into account kinetic energy.

does anyone have any idea?