## General Mechanical

#### How to model pipe walls in 2.5D in Transient Structural

• Chee Min Leong
Subscriber

Hi,

I would like to know how I can replicate the relationship between the two solids (image A) as if they were pipe walls (image B - highlighted sections) as shown in the images below.

Image A

Image B - Highlighted Wall Section

The reason for being one cell thick was so that I could later incorporate fluid between the two solids and perform FSI for a pipe conveying fluid in 2.5D since FSI is not possible in 2D (or so I read).

I am also working on a 3D FSI model for it but the simulation takes a long time even after symmetry. I am just wondering if there is an alternative.

• Erik Kostson
Ansys Employee

Hi

Use perhaps 1/4 symmetry – so model only one quarter perhaps.

(Cyclic regions can not be used so hence 1/4 is the way to reduce the model size)

All the best

Erik

• Chee Min Leong
Subscriber

Hi Erik,

Thanks for the suggestion. I don't think I could use 1/4 symmetry in my case because the pipe will swing side to side (along the x-axis), but do correct me if I am wrong. Here is a video of the phenomenon I am trying to replicate,

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(up to planar flutter).

Cheers,
CM

• Erik Kostson
Ansys Employee

Hi

This is like nonlinear flutter/instab. – perhaps not then since is chaotic motion.

All the best

Erik

• Chee Min Leong
Subscriber

Yes. It is a nonlinear flutter for the first mode shape which is what I am trying to model. As shown in the video between 0:05 to 0:20, the motion of the pipe is generally on a single plane.

Hence, it is possible to use symmetry which is what I am currently working on as well but was wondering if it could also be done in 2.5D to reduce computation time.

• Erik Kostson
Ansys Employee

Hi

If it is in one plane perhaps one can use 1/2 symmetry (2.5 D there is nothing called like that in Ansys – cyclic symmetry/region can not be used here which is kind of 2.5 D perhaps).

So just use full model, or if it moves in a single plane perhaps 1/2 symmetry. All the best