Fluids

Fluids

Residuals don’t appear in the plot, why?

    • nep
      Subscriber

      Hello,

      I'm modeling the solar radiation on a steel plate to see the temperature but I don't see the residual continuity etc.

      Could someone give me any clue as to why they do not appear, please? in the configuration I have marked the checks so that they appear in the plot but nevertheless it seems that they are not being calculated...

      Thanks a lot

    • Rob
      Ansys Employee
      How many cells zones have you got, and what are they?
    • nep
      Subscriber
      Two zones, one for the air modeled behind the plate (convection) and one for the plate (solid).

    • Rob
      Ansys Employee
      Please repost the image, I'm not permitted to open attachments.
    • nep
      Subscriber
      Sorry. I have changed the model and I have removed the air zone, to simplify it. now I only have the 15x15 cm modeled plate (1.5mm).
      I attach the image of the supplied solar radiation (the checks that the surfaces participate in the solar radiation are activated), but I can't get the residuals to be shown on the graph, I think there are equations that are not being calculated (the residuals checks are marked too).
      The configuration is stationary and pressure, with the SIMPLEC method at 1000 iterations... I attach more images.
      On the other hand, I can't get that solar radiation reflected on the plate, the plate doesn't change temperature...I think that could be the problem.
      Thank you very much for your help.
      All the best


    • DrAmine
      Ansys Employee
      Screenshot of Fluent Console to see if continuity residual is zero or not. Do you have inflow/outflow? If not do you have scenario of buoyancy? If yes: gravity on?
    • nep
      Subscriber
      Hello With the conditions that I described in the previous message, everything goes to zero, the graph doesn't even come out now... I attach images:

      Thanks for the help
    • DrAmine
      Ansys Employee
      run for more iterations: under Residual disable convergence by residual to enforce certain number of iterations.
      Do you have inflow?
    • nep
      Subscriber
      I put 10000 iterations as an example and now the energy residual appears, only. And the temperature of the plate is still at 300K, its temperature doesn't increase, I don't understand why the solar radiation doesn't affect the plate. Am I missing something to configure? I suppose that when this happens, the other residuals will appear?

      Thanks
    • DrAmine
      Ansys Employee
      Please add picture to understand the problem: perhaps surface display. Again do you have one or two cell zones? If only solid: continuity will be always zero same with velocity.
    • DrAmine
      Ansys Employee
      To account for radiation through solids: this should be explicitly enabled under the cell zone condition: please verify that too.
    • nep
      Subscriber
      Sorry, I didn't understand what you mean:
      "continuity will be always zero same with velocity"
      In models where there is only one body, the continuity and velocity residuals are zero?
      Yes, in cell zone condition I also enabled the radiation participation check.
      I want the radiation to hit only the face:"placa_con_radiacion" but I don't get it. Always the temperature it's 300K.


    • DrAmine
      Ansys Employee
      If you have only solid: continuity and momentum residuals will be zero as momentum and continuity do not make a sense for solid.
    • Rob
      Ansys Employee
      To add, as you only have a solid there are no continuity residuals: there's no fluid zone to solve them on. The zero reported is a placeholder because of the way the solver reports work.
    • nep
      Subscriber
      Ok, so that doesn't mean that the solution is wrong?
      Anyway, it is not normal that it converges in iteration 1, right? the model is not working because the solar radiation is not reaching the first face of the plate, could you tell me why, please? I am missing to model the solar radiation.
      Thank you very much
    • DrAmine
      Ansys Employee
      It is not wrong: if you just have solid zones you can disable the solution of continuity and momentum equations.
      Disable residual check by convergence and run.
    • nep
      Subscriber
      Ok, thank you very much.
      And about the solar charging, could you please, tell me what am I doing wrong? I attached a picture in previous comments of the solar configuration.
      In cell zone conditions I put that it is a solid (inconel 625 steel) and that solar radiation participates. The material inside is not hollow.
      Then, in boundary conditions, in the face where I want the solar radiation to affect, I put via system coupling, which is opaque and the solar radiation participates.
      Would this be correct? because the plate still does not increase in temperature in this face, as if no solar radiation was reaching it...
    • DrAmine
      Ansys Employee
      I cannot follow-up: are you using Solar Load Model + solid zone?
    • nep
      Subscriber
      Yes, but the plate still does not increase in temperature in this face, as if no solar radiation was reaching it...


    • DrAmine
      Ansys Employee
      Solar Load Model will work if and only if the first walls you have in your system are semi-transparent.
    • nep
      Subscriber
      I'm sorry... I don't understand. The steel is opaque, should i put it as semitransparent? would that be correct? because it's not a transparent glass for example, I don't know if that semitransparent check refers to that.
      I only have the steel plate.
      Thank you very much for your help
    • DrAmine
      Ansys Employee
      That is the problem.
      For all of your external opaque walls, set the BC Type to be semi-transparent, then the absorptivity to 1 and transmissivity to 0 - Initialize the model and do not run.
      Now Create a custom-field function for the blackbody temperature, i.e. (Solar Heat Flux/ 5.67e-8)^0.25. Call the function 'radtemp' . -Export profile of the blackbody temperature: Define -> Profiles -> write -> surfaces = all opaque external walls, and select the blackbody custom field function name.
      Now change back to Opaque Wall BC's and use the newly exported profile as Outside Radiation Temperature.

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