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Polar Creation Not happening

Hello All,

My polars appear to not be generating on V 2.0.4.5 and 2.0.4.8_alpha windows I am trying to import and then generate a polar for the NREL S823 at an Re of 155000 and Mach number of .01925. I copy the Selig format of the dat file from Airfoiltools.com, import from clipboard, then go to the Airfoil Analysis Module, say create new, input my Re and Mach number and then leave the Ncrit value and convergence values at their defaults (9 and 1 and 1 respectively) I then tried running the analysis at -15 to 20 degs with a delta of .5, the xfoil (or something) progress bar pops up really quick and then disappears and no new polar shows up or appears to be generated. Any thoughts on what I am doing wrong?

Thanks,

Jacob

Hi Jacob,

all steps that you describe are correct, but for some reason XFoil is not being executed correctly on your machine. The coupling to XFoil in QBlade-CE is realized by calling the XFoil binary outside of QBlade. So the problem could be that somehow QBlade-CE doesnt have the rights or otherwise fails on your machine to create the XFoil input files and call the executable. Maybe starting QBlade with admin rights might fix the issue. Otherwise you could check the permissions on your machine regarding the XFoil binary. On a second thought: does the turbulent windfield generation work on your machine? The TubSim binary is called in a similar way as the XFoil binary…

BR,

David

David! Thanks for the reply!

Here is the update: The Turbulent windfield generation does work, both when run normally and as an admin. The Polar generation runs if I run QBlade as an administrator, however the polar is now just flat at 0 (from -15 to 20 degs). I tested with 2 different airfoils  and both came out flat. The turbulent windfield does look normal (however I’ve never generated one before). I have xfoil downloaded and can and have run it separately. Is that part of the problem? This is also happening on 2 computers. I am on a Lenovo laptop using the 4.5 version, and my teammate is on a different lenovo laptop, running the 4.8 version and having similar problems.

Thanks,

Jacob

Hi Jacob,

this is not so easy to debug since I havent experienced such behavior before – and on my machines everything is working nicely. What you could try:

  • test if other XFoil functionality in the Airfoil Module works, such as Set TE Flap or Repanel Current Airfoil, these functions use the same “interface” with XFoil as the polar analysis
  • maybe your installed version of XFoil is in the PATH environmental variable, so it gets executed instead of QBlade XFoil binary, try renaming your installed XFoil binary
  • check if the XFoil analysis works with a NACA 4-digit airfoil thats directly generated in QBlade
  • check if your airfoil has a TE gap, which XFoil might require to converge

The outcome of these tests could help to narrow down the issue…

BR,

David

Sorry to come back to this after so long. We got busy doing some other things and didn’t have time to focus on this. I redownloaded qblade and polar creation worked for like a day, and now it no longer works, including repaneling etc.

  • I don’t know how to rename the xfoil binary in qblade?
  • It won’t generate the NACA airfoil
  • I’m not sure what a TE gap is, but we were able to get it to converge and run in xfoil by itself.

Our current work around is just to run it in XFoil and then import the polars, and then we can extend and smooth them etc.

Hi Jacob,

I can inform you that there is a high chance we could isolate and fix this erratic behavior related to the XFoil coupling in QBlade-CE v2.0.4.9, which was just uploaded. Could you give it a try to see if this issue is solved for you?

BR,

David