Displacement of a Probe Subjected to Fluid Pressure

[MrMarco]

Hi everyone,

I am encountering difficoulties in defining on Abaqus a simple probe subjected to a distributed load (given by fluid pressure), whose orientation is fixed in space, while the probe can move due to the load application.

The geometry is the one specified in the picture.

I tried to apply a surface traction load but i am not sure this is the right way to define the problem.

The aim is to achieve a time marching simulation where I can see the deflection of the probe up to a steady state condition where it reaches the maximum deflection due to the load application.

Thank you very much in advance!

Marco

 

[FEA way]

It would be best to apply surface pressure distribution imported from CFD analysis or run FSI co-simulation with external software but if you can't do it then you have to define the load manually. Surface traction seems like a good idea. Run some tests and see if the deformation looks correct.

 

[MrMarco]

Thanks for your reply!

I'm doing this analysis to achieve a preliminary result. Maybe in future I'll implement it with CFD results.

What I have achieved so far though, is a solution where i get the first deformation on the first time step and then it remains constant for all the other time steps. I find it strange since I imagine a first deformed shape which gets more loaded then the previous shape and so get more deformed, but I'm not getting this result.

Do you have any suggestion on how can I improve the simulation? I upload the dialogue box from the surface traction definition. Maybe I'm missing something there.

If it can be useful, I think that what I'm trying to achieve is well represented by this video

https://www.youtube.com/watch?v=gnO4TjKjPnQ

 

[FEA way]

If you want to model the variation of distributed load in time then you have to define amplitude and reference it in load definition. Otherwise the surface traction will be applied with default ramp amplitude (linear increase throughout the step).

 

[MrMarco]

Well, actually the load should remain constant, while its orientation with respect to the surface changes, since the probe gets deformed, so it is not a proper variation of the distributed load, in a global frame of reference. Am i wrong?

 

[FEA way]

Distributed loads update with deformation of the model when NLgeom (geometric nonlinearity) is enabled. Regardless of that, you can define complex distributed load variation in time and space using DLOAD subroutine or create multiple analysis steps with modified load.

 

[Mustaine3]

Are you sure that the fluid applies a shear traction on the inner surfaces of the tube? Most fluid have no shear stiffness and the velocity at the wall is assumed to be zero.