Learning Forum

[enes savli]

I am simulating lamb wave propagation water + pipe + water crossection to see how leaky waves behaving using transient structural module. I would like to see pressure fields in liquids that occurs due to leakage of S0 modes of lamb waves from solid. I am confused about that. What module I can use for that? Should I do FSI simulation or Coupled transient simulation?

[Erik Kostson]

 

 

Hi

You should use the coupled field transient system with the pipe as structural region, and water domains as acoustic physics regions. Use an inplane/axial force on the pipe to excite the S0 mode, very similar to this example (have in mind that this is an old example not using the new coupled field transient, so you should use coupled field transient). https://www.cadfem.net/gb/en/industries-topics/references/reference/transient-sound-emission-analysis-during-offshore-pile-driving-of-monopiles.html

Have in mind that coupled field transient is only in 3D – if you want to use 2D axis-sym. (which is ok for the S0 in a pipe), we need to use transient structural system with apdl command snippets.

All the best

Erik

 

 

[enes savli]

Thanks for the answer Erik, 

For now I don't model hole pipe just crossectional plate (Like this video :

) in this video we can see the pressure fields i am not sure what he used.

Actually my ultimate goal is to calculate shear wave attenuations caused by liquid viscosity. I can't estimate what module/coupling I should use. So i in that case would be the same coupling?

All the best

 

[Erik Kostson]

 

Hi – the fist one with the mach cone leaking into the water that is the S0 mode – you would need 2D axis-sym. if you want to do like the video, which needs as I said commands snippets like in the cadfem paper (link I sent). 

As for shear wave, in a wave guide these fundamental waves (Shear and Compression) form guided waves like S0 Lamb wave in a plate. If you mean the SH in a plate or like a torsional (T) mode in a pipe, then 2D can not be used, you need the 3D coupled field system.

As for your study that has been done long ago by NDE group (Imperial C.) – see here:
https://ieeexplore.ieee.org/iel5/58/29255/0132085

See there for more info and how this can modelled with FEA.

All the best

Erik