Learning Forum

[Patrickodon]

Hi all,

 

When attempting to run my simulation, I come across a floating point exception.

 

I've tried increasing/reducing my mech, but get this message:

 

 

Is there any good way of doing this in such a way that it will run? Here is a cut of my mesh (3 parts):

 

 

How do I increase the quality, without going way over the maximum elements/nodes allowed in the student version?

[Keyur Kanade]

The min orthogonal quality should be above 0.1 to proceed to solver. If it is less than 0.1 then please improve the mesh. 

First check the locations of the bad elements. Please see following video for the same. 

 

https://www.youtube.com/watch?v=ZDADSSN8hOs

 

 

Once you have locations, please check if you can improve mesh using different mesh sizing. Please see following video. 

 

https://www.youtube.com/watch?v=w4q6q8nKF3U

 

You can see more information about sizing at following link. 

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v221/en/wb_msh/msh_Use_Adv_SF.html?q=sizing

 

 

If this does not help, please go to geometry and modify or simplify geometry at those locations in SpaceClaim. 

[Patrickodon]

 

I restarted the model and got the mesh orthogonal quality up over 0.2 at minimum:

but I still get an error (without climbing residuals):

 

…is there any explanation for this at all? I see no issues that should stop my run here.

 

[NickFL]

This is a very generic error message. There is no one solution for this problem. What I would recommend is to iterate a few times and see what the solution looks like. Does it make sense? Are there interfaces that are incorrectly defined and acting like walls (I see you moved to a conformal mesh below)? Even if you were to initial the solution with the Hybrid Initialization, you may be able to identify a problem.

Other reasons for this error could be due to the physics you are trying to model. Situations like non-constant material properties and drastic changes between elements can lead to floating point errors (are there any warning in the TUI before it diverges). They all tie together. Also try creating monitor points in your model that you can visualize what is going on in your model during the solve. These could be the pressure at an inlet or an important surface. These can help guide you to what is causing the error.

[Keyur Kanade]

Please check set up and boundary conditions. 

[Patrickodon]

 

I have two contact regions that naturally occured when I created the three-part model. I then created named selections on each part where the sections meet each other. This, however, gives the exact same floating point exception.

 

 

 

Are there any other boundary conditions I should be looking at?

 

[Keyur Kanade]

Do you want conformal or non conformal mesh. 

Please check Share Topology section in the help manual. 

Regards,

Keyur

How to access Ansys Online Help Document

Guidelines on the Student Community

Fluids Engineering Courses | Ansys Innovation Courses

 

[Patrickodon]

I currently have a non-conformal mesh, with my three different sections - should I change to conformal?

 

 

I can access shared topology here, I'll run through it now

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v221/en/flu_ug/tgd_user_workflow_guided_share_topology.html?q=share%20topology

[Keyur Kanade]

It depends on your application. In general go for conformal mesh. Please go through help manual for more details Regards, Keyur How to access Ansys Online Help Document Guidelines on the Student Community Fluids Engineering Courses | Ansys Innovation Courses

[Patrickodon]

So I went through some of the meshing in this video (

&t=380s&ab_channel=ANSYSLEARNINGforBeginner) and got a better mesh:

 

But I'm getting almost the same error:

 

 

I'm not sure why this is - what is a floating point exception? This is surely nothing to do with the mesh, as I'm getting the same issue with the improved mesh and shared topology?

[Keyur Kanade]

This is very generic error. As mentioned earlier, please check set up and boundary conditions.

This needs more information. 

Regards,

Keyur

How to access Ansys Online Help Document

Guidelines on the Student Community

Fluids Engineering Courses | Ansys Innovation Courses

 

[Patrickodon]

Here are my boundary conditions from a working model:

 

 

and here are my boundary conditions from my new model, with the floating point exception:

 

 

I'm missing a contact region in my interface, and a wall. I'm assuming I must add the wall (and the contact region will auto-generate?) in mesh, how do I find where I must add this - and how do I go about doing it?

[Keyur Kanade]

The images show boundary zone names and not boundary conditions. Please check each boundary condition given to each boundary zone and compare with working model. 

Regards,

Keyur

How to access Ansys Online Help Document

Guidelines on the Student Community

Fluids Engineering Courses | Ansys Innovation Courses

 

[Patrickodon]

I compared the boundary conditions for the new 10 % calcium model (left), and the (working) 1 % calcium model (right):

 

 

It seems my Wall-21 on the calcium block of the original model has an extra wall and interface (highlighted). Here is the calcium block (note a section plane is cutting the model):

 

 

How do I add these walls and interfaces to my new model? Here is my 10 % and 1 % setup, respectively:

 

 

 

My 10 % and 1 % DesignModeler setups are slighty different; my 1 % has an extra hydrogelbody that I've suppressed (second image):