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  • Final Mini Project – CFD foundation course

    Posted by Mathanraj on January 5, 2024 at 2:15 pm

    Hi !

    I have designed AHMED model using Design-modeler & Space-claim.

    Meshing and setup done by fluent.

    When I run calculation for lift & drag after initialization,result is not converged even after 1000 iterations.

    I couldn’t my mistake.
    Please guide to get converged solution.

    Thank You!

    Orhan replied 2 months, 3 weeks ago 3 Members · 7 Replies
  • 7 Replies
  • Sujith FTL

    Member
    January 5, 2024 at 3:22 pm

    Hi Mathanraj,

    Please check you reference values you’ve given as the drag and lift values seems to be very large from the data you’ve shown. Give averaging for every 200 iterations as the fluctuations seem to be periodic for every 200 iterations and check the values.

    Regards,

    Sujith

    • Mathanraj

      Member
      January 7, 2024 at 7:06 am

      Hi sujith !

      Thanks for the reply!

      I have a doubt.

      What is the reference value which you are mentioned here?

      • Sujith FTL

        Member
        January 8, 2024 at 7:30 am

        Hi, you can find the reference values section after the boundary conditions section in the setup tree.

        • Mathanraj

          Member
          January 17, 2024 at 4:19 pm

          Thank u Sujith..
          I have calculated area of inlet using report option in results.

          Updated the calculated area as ‘reference value’ & changed ‘pseudo time explicit relaxation factors’ like pressure & momentum as 0.25 from 0.50.

          Now my solution is converged after 348 iterations.

          Solution: drag co-efficient = 30.15 & lift co-efficient = 79.61

          Is my solution correct?

          • Orhan

            Member
            January 17, 2024 at 5:17 pm

            Hello Matranhaj,

            I see in the previous message that you said that you calculated the projected area of the inlet. In my project, my drag_coefficient value in the project I made for Ahmed body geometry (slant angle 30°) was: 0.297. This was consistent with the wind tunnel test values. If you take the projected area from ahmad_body, your drag values will be calculated more accurately.

            • Mathanraj

              Member
              January 18, 2024 at 5:38 pm

              Thank you Orhan !

              I have changed the projected area & velocity reference values.

              Now i got Cd value as 0.33 for 35 degree ahmed model with flap on sides.

  • Orhan

    Member
    January 20, 2024 at 6:37 pm

    You are welcome Mathanraj, good luck

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