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Old   August 24, 2011, 07:32
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Thomas
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Hello

I am computing 1/6 of a pipe with a restriction inside. The material is air. As a BC I use a pressure difference of 1 bar between the inlet and outlet. (Advection and Turbulence Scheme: High Resolution) This results in a Mach number of 5.
I expect a shock after the restriction but unfortunately there is no. Does somebody know which options I have to change to get the shock?
Thanks for helping!

Regards
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Old   August 24, 2011, 07:44
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Glenn Horrocks
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Post an image of what you get. And the CCL file.
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Old   August 24, 2011, 08:09
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This is one of the results I got.
Attached Files
File Type: zip pipe.zip (47.7 KB, 16 views)
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Old   August 24, 2011, 18:49
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Your image looks like it shows a shock wave at the end of the Mach 5 section to me.
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Old   August 24, 2011, 19:00
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Thanks for looking. In contrast to real experiments the shock should start earlier. Further the influence to the upper area is too small. Do you have an idea to improve the shock "qualitiy"?
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Old   August 24, 2011, 19:03
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So your problem is accuracy, not that the shock does not appear.

Try the suggestions here:
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
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Old   August 24, 2011, 19:29
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Thus you think there is a shock? I am not quite sure.
At the moment I am working at a sensitve analysis. I think the grid is fine but I will test a much finer one. I will report about the result.
Do you think the timestep size could be the right influence parameter?
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Old   August 24, 2011, 19:49
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It looks like a shock wave, but I do not have the data set in front of me so I cannot check. If you do not think it is a shock then post an image which shows it.

The FAQ explains the key general issues required for an accurate CFD analysis. I recommend you work through the suggestions.
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