Hello Richard,
Could you please explain me, how CAESAR II is calculating the Natural frequency of the pipe (Modal analysis) to decide the support span and its functions.

I have tried manually with Piping Code: DNV-RP-D101, October 2008. (A17.2 VIV Checkout procedure, page no 31/42). DNV code formula giving the frequency is less than the CAESAR II value (verson 5.10 with the build 090206), like the variation is +5% without medium & +3.5% with the medium . It means the CAESAR II is giving higher value than the DNV code value.

FYI:-
I have done frequency calculation with the fixed constant a=22.4 (Fixed –Fixed),
Condition: Horizontal pipe having length L=4.5m & size:2 Inch with SCH160 and fixed at both end (Fixed-Fixed).

Could you please send me the formula, which is using in CAESAR II to calculate Natural frequency (Modal analysis)

Thanks,
R Seeralan

There is no formula, CAESAR II employs the Jacobi (matrix) iteration scheme to solve the system of equations to determine the Eigen values and vectors.

You also have to be careful how you setup the model, you have to have sufficient node points to obtain reasonable accuracy. In addition, the "consistent mass" approach tends to be more accurate than the "lumpled mass" approach. Try changing that setting and observe the affect.

Thanks Richard,

yes "Cosistent mass" approch is matching to the code value for my piping system system.


Regards,
R Seeralan