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” zero iteration in iterative solver ” when i simulated ice on airfoil by FENSAP – ICE

    • PHAMHUUHOANG
      Subscriber

      Hello everyone !

      Thank you for reading my question !

      I am now simulating icing on airfoil by Ansys FENSAP - ICE , but this warning appeared:

      " zero iteration in iterative solver "

    • TatianaContreras
      Subscriber
      Hi, Usually for FENSAP module you can work with 500 or more iterations, and for the drop3D module you can work with 300 iterations. The time also depends of the number of elements or nodes in the mesh. If your mesh is really fine, that will take more time to run.
    • Shoaib Shah
      Ansys Employee
      Hi In general for FENSAP typically for airfoils CFL from anywhere between 50 and 200 would work. The higher the CFL the faster the simulation convergence and fewer the iterations needed. Of course, higher CFL could also mean more instability and could lead to divergence. I would normally for a multishot icing run be conservative and pick somewhere between 50 and 100. No. of iterations, anywhere between 250 and 400 iterations to achieve something between nearly full convergence and full convergence.
      The warning you are getting is from DROP3D (droplet solver) - the CFL you have picked is too high. Default settings for drop3d would almost always work. CFL=20 is sufficient. For really slow air speeds e.g. 5m/s we go CFL=40 or sometimes even higher. But for typical aero-icing 20 is ideal. For no. of iterations, for airfoils - anywhere between 150-250 iterations are enough for typical droplet sizes of 20-100microns. If droplet sizes are small, i would increase no. of iterations to allow for the shadow zones (low catchment zones) to converge better.
      For industrial cases, you can scale the no.s accordingly, mainly increasing the no. of iterations. CFL almost always the same as above.
      Also whenever facing convergence issues, open the .solvercm.out/log.txt files with a text editor and see the print outs. Convergence graphs are also useful, so see if they look reasonable.
      Lastly, more than often users forget to click "import reference conditions" for DROP3D and FENSAP inlet settings. Check to see if the LWC and velocity etc. are set correct. You will find this under boundaries panel.

      Hope this helps. Take care.
    • PHAMHUUHOANG
      Subscriber
      Hi Tatiana
      Thank you so much.
      Your answer helped me alot.
      PHAM HUU HOANG
    • PHAMHUUHOANG
      Subscriber
      Hi sshah.
      Thank you so much.
      Your explain is very clearly.
      It helped me a lot. I could fix my problem.
      PHAM HUU HOANG
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