Learning Forum

[rkoomul]

I am trying to conduct Fluid Structure Interaction (FSI) analysis of a very thin membrane.  The membrane is of size 0.3m x 0.2m and thickness is 0.0001 m (0.1mm). I sketched a rectangle with the above dimensions in DesignModeler and created a surface body using the option “Concept -> Surfaces from Sketches”, with the specified thickness.  I used this geometry for modal analysis and it is working fine.

For the FSI analysis I tried to subtract the above surface body from a 3D body using the Boolean operation, but it didn’t work and gave me an error message “ Error: Operation would result in non-manifold bodies”.  If I create a 3D model for the membrane the number of elements will be very large, and the mesh quality will be poor.  What is the best approach for modeling this type of problem involving VERY thin objects in the computational domain?

Thank you for your help.

[Rob]

In Fluent we can have a thin wall which we then assign a thickness in Fluent as needed. If you have a pressure (from Fluent) can you attach that to a shell in Mechanical? 

[rkoomul]

Thank you Rob for the reply.

Using SpaceClaim, I have created a “Surface body” for the membrane and 3-D cube around the membrane as the flow domain.  Then I used “Share” option under “Workbench” to get the computational domain. In SpaceClaim, under “Share” options, I used “Preserve Instances” to keep both the geometries (See the image below).

In the “Mesher” I am able to create a “NameList” for the membrane and able to create boundary layer mesh on both sides of the membrane. (See the image below.  This is a cross-sectional view).

I am sharing the same geometry between the fluid and structural solver (see the image below).  Inside “Transient structural”, the geometry is automatically imported as a 3-D volume with the membrane inside (see the image below).  I am not able to separate out the membrane to conduct structural analysis. Any suggestions on how to get the membrane geometry in the structural solver for analysis?

Also, are there any better approaches to conduct FSI analysis of membranes?

Thank you for your help.

[Rob]

I have no idea about Mechanical - whilst I can use the software due to it being the same interface as Ansys Meshing I don't know any more about the buttons. As a Chemical Engineer we were taught that Mechanical Engineers did have a use... ;) 

Typically a membrane is used to separate two regions, osmosis type systems being a common application. So, the membrane would be the surface boundary between two fluid regions. That may make the set up easier.