can you please tell how to solve the governing equation to obtain the frequencies to compare with the ansys result
Hi
(I haven’t looked at your xml as I doing this from my iPad).
i guess the answer is Yes and No.
Yes, we can use analytical and numerical models, or tests, to find, as best possible natural frequencies. To what effect may be worth pondering.
There are some problem with pipelines.
1) they tend to be very long. Infinite, may be a reasonable approx. Unbounded systems don’t not have modes, they have wave propagation. They can be approximated using modes but you need a lot of them and the modal summation doesn’t always converge as one would want it to.
2) every frequency is a natural frequency for an infinite system, ie you get lots of closely spaced modes, which in turn provides a high modal overlap situation (search RG, it has been discussed before).
3) I imagine that numerical solvers may have a problem with closely spaced modal systems.
4) pipelines tend to lie on something, ie the couple to terrain, again a large system.
So, chasing this problem using modes may not be your best bet.
Wave propagation for analytical models and direct numeric solution for FE probably is the better way to go.
Hope this helps
claes
You can also check this for an idea:
Chapter Impact Force Localization Using Eigenfrequency Measurement i...
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