specific speed


specific speed

[spə′sif·ik ′spēd] (mechanical engineering) A number, Ns , used to predict the performance of centrifugal and axial pumps or hydraulic turbines: for pumps, Ns = N √(Q)/ H 3/4; for turbines, Ns = N √(P)/ H 5/4, where Ns is specific speed, N is the rotational speed in revolutions per minute, Q is the rate of flow in gallons per minute, H is head in feet, and P is shaft horsepower.