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Old   June 17, 2014, 10:26
Default CDrag (TOTAL) starts at 1000.0000
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Jeffrey van Oostrom
Join Date: Feb 2014
Location: Delft, The Netherlands
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I'm trying to run a simulation for validation purposes such that I can show my supervisors that I can use SU2 in my thesis. The problem is simple, I have a blunted flat plate. The Mach-number is 8.08 and the Reynolds number is 0.17E6. The .GEO (GMSH) and .CFG can be found in the attachment (the .SU2 mesh was too large). I'm trying to get a y+-value of 1 in the first row of elements in the boundary layer, hence my first row height is 2E-7 something.

Now, when I try to run the simulation, the CDrag (Total) starts at 1000.000. I know that it should be around 0.62-ish. What in my settings is so horribly wrong that this happens and prevents my simulation to converge? I have tried adapting the mesh, tried changing the CFL number to as low as 0.1 and 0.01. I have tried (just to make sure) to change the Reynolds number.

The interesting thing is, that my supervisor has a slightly different geometry, equal amounts of elements, and a CFL of 2, bit higher Re, but is able to run the calculation without any problems.

Has anyone got any clue?

Thanks in advance for your help and support.

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Old   June 24, 2014, 20:28
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Thomas D. Economon
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Dear Jeffrey,

This is the typical result when something is immediately going unstable in your simulation. Without going into great detail to study the config options and mesh, I can only offer a few suggestions: check the quality of the elements in your mesh (or start with something even more coarse or Euler), turn off multigrid, turn the CFL way down, or try lower Mach and Re until you can diagnose and pinpoint the issue (I am guessing it might be in the mesh somewhere). Don't forget that there are many config files in the test cases folder that you might be able to use as a good starting point or template for your own case.

Best of luck,
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