Fluids

Fluids

Convection is not possible on some areas

    • matthias.zeller
      Subscriber

      Hello,


      on some areas it is not possible to apply convection in Workbench 19.0. As an example I marked some areas on the picture to show areas which are usable and unusable for convection. In case I apply convection on unusable areas there is a solver-pivot error upcoming. Anyway heat or other loads can be applied to all areas. How can I apply convection to all areas? 


      I designed the part with SolidWorks.


      Thanks in Advance.


    • Karthik R
      Administrator

      Hello,


      Are you using Steady state or transient thermal to perform your analysis? Are you able to click on all the marked surfaces in SpaceClaim? Can you please post screenshots of this in SpaceClaim?


      Thank you.


      Best Regards,
      Karthik


       

    • matthias.zeller
      Subscriber

      Hey Karthik,


      Thank you for your answer. I am doing a transient analysis. Here you can find 3 screenshots. I am able to mark all areas in SpaceClaim. The CAD-files are .stp in this case.


    • Karthik R
      Administrator

      Hello,


      Could you please try and turn off the 'Solver Pivot Checking' option under settings? You should be able to find this in the Solver Controls. Please let me know here if this helps.


      Thank you.


      Best Regards,


      Karthik

    • matthias.zeller
      Subscriber

      Hi Karthik,


      thank you for your answer. When doing a transient analysis I do not have the 'Solver Pivot Checking' option. I only have the option for a steady state analysis. Here switching off the solver pivot checking is working, but I want to do a transient analysis. How can I switch off the solver pivot checking during a transient analysis?


      Thank you in advance

    • matthias.zeller
      Subscriber

      I found another option to deactivate the 'Solver Pivot Checking' under Tools -> Options -> Solver Controls. Anway changing this does not change anything during a steady state or transient analysis. It seems like these settings are not affecting the simulation, because the settings in the Solver Controls menu on the left keep the same.

    • Karthik R
      Administrator

      Hello,



      • Do you have any other parts / components in your geometry?

      • Where is your heat source?

      • Can you share screenshots of all your boundary conditions? I would like to make sure that your problem is well posed.

      • In your transient model, what are your solver settings? And what is your time step?

      • I am sure you must have attempted to run the model as a steady state. What were your results?


      I am asking you these questions because I'd like to understand a little more about your model.


      Thank you.


      Best Regards,


      Karthik

    • matthias.zeller
      Subscriber

      In this case I don't have other parts in my geometry.


      In the first screenshot you can see that I can apply convection to this hole which reaches a surface temperature of 100 °C after 1 sec. This is working and you can see the results in the screenshot. If I apply convection to other surfaces (for example like the surfaces you can see on my older screenshots) there is an solver-pivot error upcoming and I don't get a result. I changed nothing else. I can apply other loads like radiation or a heat flux to all surfaces. Only convection causes problems. This geometry is an example. I have the same problem for other geometries as well.



      You can find the solver settings and boundary conditions in the next two other screenshots. Unfortunately it is in german. The minimum time step is 1e-3 s, the maximum time step is 0,1 s. The heat transfer coefficient of the convection is 100 W/mm2°C and the temperature of the fluid is 100 °C.


      In case of a steady-state analysis the body reaches a temperature of 100 °C everywhere. As I'd like to know the temperature distribution after 1 sec I'd like to do the transient analysis.


      Thank you for your help.


    • dinhan0394
      Subscriber

      Hi Maddes,


      Could you send me that project?


      I'll try to check project. Hope that I can help.


       


      Thanks,

    • matthias.zeller
      Subscriber

      Hi AnPham,


      thank you for your help.


      When reducing the time step I can find that the calculations are interrupted, but anyway I can get a result. In one node the temperature is very low (<< 0 K) which should be the reason for the Solver-Pivot-Error. In all other nodes the temperature is as exspected due the contribution of convection (on the surface About 100 °C, elsewhere 22-100 °C). This can be seen on the screenshot attached. In this screenshot convection is only applied to the upper surface. 



      How can I send you the project?

    • matthias.zeller
      Subscriber

      Thank you all for your help!


      Now I have the solution: There was a problem with the mesh. I changed the mesh and now it is working.

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