Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

486 Centrifugal Pumps: Design and Application
Figure 18-41. Nonsynchronous instability vibration of high speed pump.
rithmic decrement of 0.01 for a simulated fluid aerodynamic loading of
1,000 Ib/in. at the impellers [36, 47]. The pump rotor with the modified
bearings was predicted to have a positive logarithmic decrement of 0.10.
The rotor vibrations after the bearing modifications were made are
shown in Figure 18-42. The nonsynchronous vibration component was
no longer present and the unit has since operated successfully.
Appendix
Acoustic Velocity of Liquids
The acoustic velocity of liquids can be written as a function of the isentropic
bulk modulus, K s and the specific gravity:
where
c = acoustic velocity, ft/sec
sp gr = specific gravity
K s = isentropic (tangent) bulk modulus, psi