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-   -   Law of the wall plot (https://www.cfd-online.com/Forums/openfoam-post-processing/222605-law-wall-plot.html)

majidsvn7 December 1, 2019 10:42

Law of the wall plot
 
1 Attachment(s)
Hi all,
My case is a turbulent pipe flow which has been simulated in openFoam v7.
I wanna plot famous uplus-yplus graph (law of the wall) like the attached image and I don't know what shall I do?

Bazinga December 2, 2019 02:51

Well, you could use the sample utility to extract the velocity at the wall. Use some software (e.g. matlab, excel, python, whatever you prefer) to calculate your non-dimensional u+ and y+ and plot it. You would need to calculate the wall shear stress for this - I believe there might be a tool for this in OpenFOAM.

It's not as straightforward as I would like it to be, maybe someone has a better idea to get this more convenient.

majidsvn7 December 2, 2019 04:04

Quote:

Originally Posted by Bazinga (Post 751215)
Well, you could use the sample utility to extract the velocity at the wall. Use some software (e.g. matlab, excel, python, whatever you prefer) to calculate your non-dimensional u+ and y+ and plot it. You would need to calculate the wall shear stress for this - I believe there might be a tool for this in OpenFOAM.

It's not as straightforward as I would like it to be, maybe someone has a better idea to get this more convenient.

I've read all the threads and post about law of the wall plot in cfd-online but I can't understand properly what shall I do for plotting this graph... Yes, there is a utility to calculate yPlus (min-max-avg) and wallShearStress in openFoam and I know how to using those for this purpose but I don't understand how can use these values ( single value) to plot the graph?! yPLus in each case have a range and I've force the case to have a specific range of yPlus ?!!!!

Bazinga December 2, 2019 04:19

These functions give you the value at the first nodal point at the wall. What you need is the velocity profile at the wall. For example, you use the sample utility to get u and y over a line. Then you need to calc u+ and y+ by yourself before plotting.


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