Fluids

Fluids

CFD post graphic and video are not the same

    • Jamessmp23
      Subscriber

      Hello all,


      had simulated the transient 2D airlift bioreactor, when the simulation was done. the CFD post graphic was appear like what I expected but after I used the time step selector or video rendering,I cannot find the first appear CFD post graphic, I tried to look in time step selector in every single time step but not have any graphic that same as the first appear CFD post graphic, even in the video.

    • Jamessmp23
      Subscriber

      1. How to find the first appear CFD post graphic ?
      2.
      From these pictures does this simulation has the circulating at steady state, which one is correct result from the simulation ?


      Thank you,
      James 


      ***** I have a problem on posting, what wrong with the "The field Content must be a string with a maximum length of 6000. "

    • Jamessmp23
      Subscriber

      Here is the picture comparing the first appear CFD post graphic and the graphic at the end of the video.


      3. Does this simulation calculate as the cylindrical structure or as the rectangle structure ?


       

    • DrAmine
      Ansys Employee

      Does the right picture corresponds to the first time step?

    • Jamessmp23
      Subscriber

      Hello Amine,


      The right picture corresponds to the final time step.


      Any suggestion ?


      Thanks for replying,
      James

    • Jamessmp23
      Subscriber

      I getting confuse about the transient simulation,


      does this simulation is a pulse of gas flow through a water in the reactor ?
      according to the time step picture it lead me thinking of a pulse of gas instead of continuous air flow.


      Here is the pictures from time step 0.05, 0.5, 2, 5, 8, 9, 13 




      Did I setup anything wrong ? How can I set the inlet flow as the continuous air flow ? any recommendation ?


      Regards,
      James 

    • DrAmine
      Ansys Employee

      That is your simulation results so you are the one who can say whether th results corresponds to the time level or not. 


      Just to test: Switch off global scaling in CFD-Post and just use a fix scaling for the animations.


      We cannot give any recommendations without any information about the case setup.

    • Jamessmp23
      Subscriber

      Dear Amine,


      1) What about the first appear picture when the simulation done, I cannot find the same picture in any time step using the time step selector on CFD post.
      I had resimulated it, the result appear same as the first appear picture when the simulation done but still couldn't find it on the time step selector.


      2) For the 2D simulation, I would like to know that the simulation is calculate this structure as the cylindrical shape or as the rectangular shape ?
      This structure I drawn it from the spaceclaim without setup anything and during the meshing I already identified the interior surface, outer wall edge, inlet edge and outlet edge.


      3) The transient simulation, I had setup the material primary phase as water and secondary phase as air with diameter = 0.005 m.
      at the boundary condition, air inlet = 0.075 m/s. according to the pictures I posted here (time step 0.05, 0.5, 2, 5, 8, 9, 13 ) I though it is a pulse of gas but I prefer to flow the gas continuously with a flow rate = 0.075 m/s, So my question is, did I setup anything wrong in the boundary condition ? 


      Regards,
      James

    • DrAmine
      Ansys Employee

      1/You need to clarify a bit how you are creating the pictures or animation here.


      2/I do not understand


      3/So air is coming from the top and gravity is acting from bottom to the top? 

    • Jamessmp23
      Subscriber

      1). Okay, first I simulate the A (Fluid Flow, Fluent) then at the Results, created the contours and vectors. Later, I duplicate the A (Fluid Flow, Fluent) and edit the geometry then simulate. After the simulation is done. I opened the Results.
      There is a contour picture that I expected it, then I choose a time step selector to see other time step contour pictures. after that I tried to find that contour picture in time step selector but I cannot find it. 


      * I can see the water contour, air contour, water vector, air vector of that graphic before I mess with the time step selector,


      I would like to know, what does it means ? does that first appearing picture is wrong ?  


      I can send you the picture and the video.


      2) I just not really get the concept of 2D and 3D simulation, for now I will think the 2D simulation is only the airflow through a reactor plane.


      3) I will email to the reference paper's author to study more about what did I misunderstanding.


      Thanks,
      James

    • DrAmine
      Ansys Employee
      1/clear generated Data for the second Analysis
      2/2D means you are assuming planar symmetry and no flow in the 3rd direction.
    • Jamessmp23
      Subscriber

      I found a solution, there is a bug on Fluent CFD post which have different results in the same simulation. I had asked some professors in this field their experienced this problem too.


      For my understanding, using Fluent to see the results (contour, vector, etc.) is more accurate than using the CFD post.
      CFD post is much more user friendly but their an error for some simulation.


      Here is the comparison between Fluent graphic result and CFD post. If I made any mistake or misunderstanding please inform.


       


      Regards,
      Sumit

    • DrAmine
      Ansys Employee

      Thanks for sharing your feedback. 

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