Set up a simulation with cavitation turned on and pressure levels set high enough to avoid levels of cavitation that significantly affect pressure rise.

If you have trouble getting a converged solution, try running a simulation with cavitation turned off, then use the result as an initial guess for a simulation with cavitation turned on.

Run the solver to obtain a solution.

Calculate the pressure rise across the pump and the NPSH value, then plot a point in the performance diagram.

Lower the pressure boundary condition by about 5% to 10%.

Repeat starting from step 2, using the previous solution as the initial guess, until cavitation has caused a significant loss of pump head.