The specifi c speed Ns, as defi ned by Eqs. (11.30), does not contain the impeller
Chapter 11, Problem p11.40(choose chapter or problem)
The specifi c speed Ns, as defi ned by Eqs. (11.30), does not contain the impeller diameter. How then should we size the pump for a given Ns? An alternate parameter is the specifi c diameter, Ds, which is a dimensionless combination of Q, gH, and D. (a) If Ds is proportional to D, determine its form. (b) What is the relationship, if any, of Ds to CQ*, CH*, and CP*? (c) Estimate Ds for the two pumps of Figs. 11.8 and 11.13
Unfortunately, we don't have that question answered yet. But you can get it answered in just 5 hours by Logging in or Becoming a subscriber.
Becoming a subscriber
Or look for another answer