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November 28, 2011, 11:49 |
Tutorial "airFoil2D" yPlus value
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#1 |
New Member
Denis
Join Date: Jul 2011
Posts: 8
Rep Power: 14 |
Hello,
I have a question about the airFoil2D tutorial. I compute the given case and evaluated the y+ value with the yPlusRAS-function. So this is the solution: Code:
Patch 2 named wall y+ : min: 958.43 max: 13790.7 average: 8328.47 So is this a bug ?? Denis |
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November 30, 2011, 05:42 |
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#2 |
Senior Member
Join Date: Aug 2010
Location: Groningen, The Netherlands
Posts: 216
Rep Power: 18 |
Hi Denis,
this isn't a bug I can assure you. The yPlus factor is a value which gives you an indication of the resolution of the boundary layer. ( yPlus = (u * y) / nu ) If you want to make a simulation without further approximations this value should be 1. However this results in lots of cells so some guys had the idea of the usage of wall functions. This allows you to increase this value up to 300 and the results may still look like a good representation of the reality (for engineers this is usually enough). Since you can then use less cells also the calculation time decreases which is quite handy. Which brings us to the tutorials: They are made to show you the general principle of a solver/feature so they usually use a coarse mesh which must not necessarily full fill all the requirements one has to a mesh, so quality or resolution factors might exceed the values which you would use for a real computation where you rely on the results. I hope I explained everything well enough regards |
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