November 3, 2018 at 2:03 pmabd fsSubscriber
As you may have seen from my last post (https://forum.ansys.com/forums/topic/separartion-flow/) I have been modeling turbulent flow around a ramp 25° . I do not have much experience so please bear with me even if my questions are simple.
I have been wanting to check the U+ vs Y+ values in order to determine if the mesh around at the wall level is fine enough to properly model the different boundary layer regions.
I would like to plot u+ against y+ to have the velocity profile near the walls.
Did anybody already try that?
November 3, 2018 at 8:16 pmDrAmineAnsys Employee
Yes you need to write the functions for u plus and yplus to plot them at a certain position normal to the wall
November 3, 2018 at 9:53 pm
November 5, 2018 at 8:25 amabd fsSubscriber
Someone can help me? With some tips, comments?
November 5, 2018 at 10:58 amRobAnsys Employee
The velocity profile can be plotted using a line and an xy plot: you're plotting velocity against position (perpendicular to the wall). Assuming you have a fine enough mesh you'll see the expected profile.
y+ is a pre-set value (we decide what we want) and is used to calculate theoretical height of the first cell: I think it's the mid point, but look it up in the manuals. This value can then be plotted from Fluent, but only really exists as data on the wall, to check if your mesh is fine enough.
u+ is also another derived term, and you've put the curves in your earlier post.
Edit: moved to Fluids
I'm not sure why you'd need to use CFD to plot the u+ against y+ curve?
November 12, 2018 at 9:20 pmabd fsSubscriber
I am having extreme difficulty getting this to work. Likely because I have no clue what I am doing.
Iam required to compare the law-of-the wall profile to the Uplus v Yplus computed in fluent for a K-omega SST turbulent flow.Fluent gives Yplus but not Uplus.
For logarithmic u+
My question is: how can plot the famous TBL curve U+ vs y+, to detect the 3 zones ?
November 13, 2018 at 5:52 amDrAmineAnsys EmployeeYou need to define y+ and u+. Then create a line at a certain position normal to a wall then you can xy plot to plot the profile you want. U+ is the velocity in the cell / square root of wall shear stress divided by the density.
November 13, 2018 at 7:41 amabd fsSubscriber
Thank you so much AMINE I forgot this,
May 7, 2020 at 12:03 pmmutlaq404Subscriber
Mr. Abd How you calculate Yplus?
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