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spatial resolution in StarCCM+ for LES

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Old   March 10, 2014, 10:37
Default spatial resolution in StarCCM+ for LES
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Dear All, I am performing LES in StarCCM+. To make sure the mesh is reasonable, I need to check the spatial resolution including Y+, as well as X+ and Z+ in the other two directions. StarCCM+ already has the field function of Y+, but how to get the spacitial resolution for the other direction, X+ and Z+?

Thank you so so much !

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Old   March 10, 2014, 12:20
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Y+ does not refer to a specific direction, it is a parameter which is relative to the local face normal. X+ and Z+ do not exist.

Please read up here:
http://en.wikipedia.org/wiki/Law_of_the_wall
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Old   March 10, 2014, 13:03
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x^+ and z^+ do exist.
You can estimate them through the extent of the cell in the respective direction.
Say you have a certain value of y^+ for a cell which has an extent of \Delta y in y-direction.
Then the value for x^+ is
x^+ = y^+ \frac{\Delta x}{\Delta y}.
Same with z^+.

Pay attention that this concept is only valid for the first cell near a wall where y^+ is related to the wall-normal extent of the cell.
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Old   March 10, 2014, 13:20
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I meant they don't exist in STAR-CCM+, sorry.

I don't see any method of calculating these values without user code, unless the geometry is simple enough to know the cell dimensions a priori.
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Old   March 11, 2014, 07:52
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Hi, thank you very much for your reply... which really shocked me... StarCCM+ does not have x+ and z+ ? OMG... If that's true, I would have big trouble with my work..

Thank you.
Aqua

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I meant they don't exist in STAR-CCM+, sorry.

I don't see any method of calculating these values without user code, unless the geometry is simple enough to know the cell dimensions a priori.
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Old   March 11, 2014, 07:57
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Hello Alex, thank you for your kind reply. I understand your explanation, but my problem is , how to get it from StarCCM+... do you have any idea?

In Starccm+, I can get Y+, but then , to calculate X+ and Z+, I would need the size of the cell (width or length), which is an issue for me...

Thank you

Aqua
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x^+ and z^+ do exist.
You can estimate them through the extent of the cell in the respective direction.
Say you have a certain value of y^+ for a cell which has an extent of \Delta y in y-direction.
Then the value for x^+ is
x^+ = y^+ \frac{\Delta x}{\Delta y}.
Same with z^+.

Pay attention that this concept is only valid for the first cell near a wall where y^+ is related to the wall-normal extent of the cell.
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Old   March 11, 2014, 11:29
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No need to be shocked, no general purpose commercial CFD software has predefined functions for these values.
As pointed out by me3840, you will need some user code to get them unless you have a very simple setup.
I am no longer working with CCM+, so I cant really give you a hint how to do this.
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