Thank you very much, Mr. Claudio for the prompt response.

I generally understand the approach you have mentioned. But, in order to implement the same in ANSYS, what would be the the sequence of stepsto be followed?

As per my understanding, first the added mass value has to be determined the using the tables of formulas for added mass. Then a structural mass element (may be mass21) needs to be defined in ANSYS. This added mass element will have to applied at certain node (or maybe all of the nodes of the plate) and the modal analysis has to be performed.

I am thinking of how to decide the node(s) on which the "added mass" has to be applied? Should it be distributed equally on all of the nodes?

Warm regards

Nitin

I understood the approach clearly. However, I was unable to validate the natural frequencies with those reported by Li and Li (2008) in Table 2 [DOI: 10.1016/j.apacoust.2006.11.004].

The problem parameters are:

a=0.455m, b=0.379m, h=0.003m, E=210e9 (Steel), v=0.3, ro=7850

I used shell281 to model the plate. Using the relation for hydrodynamic mass for flat plate as given in document UCRL-52342 [Table 6, page 13], I obtained the added mass (ma=28.940). Then, I computed the density to be added, i.e. ro_added=ma/(a*b*h).

Lastly, I input the density in MP,DENS equal to (ro+ro_added). Unfortunately, only the first mode matched and the other modes were off by more than 30%.

Am I doing something wrong?

Also, how to get access to the table in ASME Sec. III Appendix N (Table N-1311-1)?

Warm regards,

Nitin

I remember once (it was a long time ago) having a discussion about modal analysis of submerged components. ANSYS suggested using any ordinary structural element to model the surrounding media. I've done that with APDL the way the attached document indicates. I imagine (I'm not ANSYS user anymore) FLUID220 or FLUID221 could be used to model the surrounding fluid. You definitely don't need FSI. It is overkill. I would also use shared nodes at the interface (fluid+struc) instead of contact.

Thanks a lot Mr. Giovanni for the suggestion.

I shall try this and will update my results here asap.

Thanks

Nitin

Thankyou very much for your input and guidance. Now, having implemented the added mass methodology in ANSYS, I shall try the same problem by the approach mentioned by Mr. Giovanni.

Warm regards,

Nitin

Please let us know Nitin how successfull you were.

Regards

Giovanni

http://www.intes.de/kategorie_permas/modules/dynamics/fs/

Sure, I will be happy to share how the approach worked out.

Thanks for pointing to the ACT extension, I am aware of it but have not used it much. I am working on vibroacoustic responses of composite structures using FEM-BEM through an in-house code. And, as a first step I try to validate my results with those obtained using the commercial tools. That's why I am interested in solving problems via Ansys/Abaqus.

Will be troubling you gentlemen with more questions in future...

Thanks

Nitin

Thanks a lot Mr. Nils Wagner for the link to PERMAS-FS Fluid-Structure Acoustics tool. I would check out if they offer a trial version for this software.

Warm regards,

Nitin

@ Mr. Giovanni , @ Mr. Claudio

I tried modeling the problem as pointed by you. Unfortunately, I think there is some mistake I am making and I am unable to identify it. I will briefly explain what I did:

Any idea on where I have possibly gone wrong?

Warm regards,

Nitin