Specific speed – Specific diameter
Similarity of hydraulic turbomachines

A turbomachine must convey a given fluid flow rate q _v by giving it an imposed height H _m , with the best possible efficiency. In addition, it may be necessary to impose the speed of rotation :

• either a driving or receiving machine running at a given speed;

• or the risk of cavitation imposes a maximum speed above which it is impossible to operate; a lower speed would have the disadvantage of increasing the size of the machine, which is undesirable from a cost point of view.

It may therefore be useful to characterize families of homothetic turbomachines by a reduced variable...