Specific Speed of turbine

The specific speed of a turbine is defined as the speed of an imaginary turbine, identical with the given turbine, which develops unit power under unit head. Mathematically, specific speed,

where

P = Power, and H = Net head on turbine.

The specific speed plays an important role in the selection of a type of turbine. By knowing the specific speed of a turbine, the performance of the turbine can also be predicted.