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Overflow and Zero divide errors in compressible flow

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Old   April 23, 2014, 06:18
Default Overflow and Zero divide errors in compressible flow
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Noukhez Ahmed
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I have attached the error below in what I persist to get. I am trying to simulate a centrifugal compressor in compressible flow and keep encountering overflow, no matter what settings I alter. This is the main problem. Furthermore, in order to achieve better residuals, I have used incompressible flow allowing it to converge, then changing the flow to compressible and run from this point forward. However, the zero divide error arises. Please review the attached documents. I hope you can help. Many thanks.
Attached Images
File Type: jpg overflow error.jpg (57.4 KB, 11 views)
File Type: jpg zero divide error.jpg (93.2 KB, 8 views)
Attached Files
File Type: zip flow iterations.zip (43.3 KB, 1 views)
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Old   April 23, 2014, 07:17
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Bharath kumar
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I don't have experience in compressor CFD model. Still i had some questions.

1) Check your solver is reporting High Mach number (more than 2) warning while solving compressible flow.Is that OK?

2) Rotor domain minimum angle is 10.Is it possible to improve that?

3) Incompressible flow is a bad intial condition for a compressible flow problem.

4) Try less Pressure ratio first and gradually increase it to final value.It may help.
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Old   April 23, 2014, 10:13
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Kevin Hoopes
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What Exit BC are you using? I have seen this alot when the compressor is trying to run off the map.
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Old   April 24, 2014, 04:00
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Glenn Horrocks
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This question is an FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

Before diving into details I would check that the basics covered in the FAQ have been checked first. Because the first one (mesh quality) is almost always a MAJOR factor.
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