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Flow Induced Vibration of Power and Process Plant Components: A Practical Workbook

By
M. K. Au-Yang, Ph.D., P.E.
M. K. Au-Yang, Ph.D., P.E.
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ISBN-10:
0791801667
No. of Pages:
494
Publisher:
ASME Press
Publication date:
2001
In the special case when only one of the cylinders is flexible, the “in-water” natural frequencies of the shell can be obtained from the “in-air” frequencies by simple rationing:  
f̄n=fnairμμ+M̑H
As shown in Chapter 4, one of the major tasks of calculating the hydrodynamic mass is the calculation of the hydrodynamic mass component h. In this chapter, simplified expressions for calculating h in special cases are given. Of these, the most commonly used in the industry is the “slender cylinder” approximation:  
hαna+ρanb2n+a2nb2na2nhαnab+2ρanb2n+a2nb2na2nhαnba+2ρanb2n+a2nb2na2nhαnb+ρbnb2n+a2nb2na2n

However, for application to large-shell structures commonly encountered in the power and process industries, Equation (5.2) often overestimates the hydrodynamic masses by as much as a factor of two or more. In addition, these equations give the hydrodynamic mass components in the form of surface densities. The effective hydrodynamic mass still has to be computed based on Equation (4.50). Failure to observe this has lead to inconsistencies in the hydrodynamic mass formulation of coupled fluid-shell problems.

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