Floating point exception in Fluent

  • 6.8K Views
  • Last Post 03 August 2018
  • Topic Is Solved
gordongn posted this 02 August 2018

I am doing a counter-flow heat exchanger simulation in ANSYS student version.

After I setup, I always got error "floating point exception"  in calculation.

Please can somebody solve my problem?

 

Intialization result:

n

 

During calculation:

Error:

 

 

 

There are my all the details:

Details:

 

 

It is recirculated exhaust gas heat exchanger which used in gas turbine. It is 200mm long with 60mm diameter.

 

In my geometry, this heat exchanger consists of three parts, hot air fluid domain (outer domain) , 4 solid pipes and 4 inner fluid domain (2 methane and 2 air). As you can see, there are 8 interfaces in total.

This is my meshing. I used adaptive sizing function to get less cells (119610 nodes and 326512 elements). And 4 edge sizing for pipes (20 Division hard). I don't use culvature size function because it will lead to 3300000 elements which I can't run it in student version.

 

This is my skewness data.

 

However, in my setup part. There are my setting.

Pressure-based

Absolute

Steady

Density on Y direction 9.81

Energy Equation On

Viscous - Realizable k-e Scalable Wall Function\

Materials are air, methane and steel

Cell Zone Conditions.

I didn't coupled my interfaces in Mesh Interfaces.

 

 

 

 

In my Boundary Condition. There are 2 air mass- flow-inlet, 2 methane mass-flow-inlet, 1 hot mass-flow-inlet. And 5 pressure outlet in total.

All the wall material has been set to Steel.

 

If you need more details, please leave a comment.

 

Thank you very much!

Gordon

Kremella posted this 03 August 2018

Hello Gordon,

Here are some suggestions about your model:

  • Your mesh skewness is really high. Please try to maintain this value below 0.95. 
  • Please try to use conformal mesh (rather than non-conformal). This will remove all your mesh interfaces and reduce your model complexity. You will have to perform 'share topology' in SpaceClaim. Here is an excellent video on how to.

  • Please make sure you have sufficient boundary layer mesh corresponding to y+ ~ 40, since you are using scalable wall functions.

I hope this helps you overcome your convergence issues.

Thanks.

Best Regards,

Karthik

Close