**2. Materials and Methods**

The fluid dynamic models in both pump and turbine operation are shown separately, highlighting the various steps necessary to obtain the characteristic curves of the machine. These models are tuned on a sample of 6 centrifugal pumps, having specific speed changing in the range 9.05 ÷ 43.48. On these pumps, the measurements of the geometric parameters and the experimental tests on the test bench were carried out, as the flow rate varied, both in direct and reverse operation.
