can you help me how to find flow rate of turbine runner or tick the mistake on my work

here i am new and i am beginneer in openfoam and paraview. i have a simple rotatating domain and solved in openfoam. i could find the force and torque on the turbine simple runner but i got problem in finding flow rate , head, power.
i try to use simply calculator with force, pressure but it is not good
hope i will get answers from here
thank you in advance
any suggestion regarding this will be helpful for me