Learning Forum

[ali_i_96]

How can i do an FSI analysis using a 2D model ?

I've tried to extrude the model to a 3D model and do a one element through thickness mesh , but any change in the thickness will lead to a change in the results .

What can I do ?

Thank you in advance

[Rob]

Why will it change the results?

[ali_i_96]

First Thank you for your response .
The problem is the following :
I have a 2D model , I want to do a FSI analsysi ( which can't be done in 2D in ansys ) so i extrude the geometry to a 1mm thickness and i have a done a one element through thickness mesh , and I have done the fsi analsys .
After that , I want to check if method is good , so i have make an extrude about 10 mm , then when i have run the analysis the results of stress and deformation was changed .
The stress in the wall caused by the fluid has different value when i changed the thickness .
So the result have differ .
If there is any other solution to do the 2d fsi ?

Thank you .

[ali_i_96]

This is an example of what i have faced, these two simulation the first is with a 1 mm thickness and the second with 3 mm thickness. The Imported pressure differ between the two thickness , also the shear stress at walls in the Fluent results.
you can see the difference in the Equiv Stress Results with varying the thickness.
Thank you in Advance

[Ananth Narayan]

Did the side face in your model contain one element in both cases?. Means- you need to set element size to 3mm in the second case because this will not form some kind of similarity I believe. Try doing this and share your results.

[ali_i_96]

Hello , Thank you for your response.
Yes I already did that ( the element in the thickness for the second case is 3mm ).
I've shared the results in the thickness for the two cases . You can see the imported load how it's differ also.

[Rob]

Check the pressure in Fluent. Reporting max values can be misleading if it's a tiny area that's affected. The resolution isn't that high either so you also need to review convergence and mesh resolution in Fluent.

[ali_i_96]

Hello Thank you for your response.
I've tried to make better mesh , the results remain changing when I've tried a new thickness ( 0.1mm - 1mm - 5mm ).
The results in fluent concerning the static pressure and wall shear stress have changed with each thickness ,
Do we have a ratio of what thickness should we choose when doing FSI 2d ( one element through thickness ????

[Rob]

Can you post some results? Without knowing what you're looking at it's impossible to give any guidance.