[Nek5000-users] Calculating wall shear stress and dimensionless wall distances

[nek5000-users at lists.mcs.anl.gov]

PS -- the way to do this in postx (which assumes you have a .fld file
       structure and not the .f000 file structure) is:

SET PLOT FORMAT
X-Y PLOT
SET OF PROFILES
PLOT

then answer the questions.   You will be prompted for the name of a file
containing the endpoints of each query line -- I usually call it "prof.in"

You can change the line interrogation resolution (i.e., how many sample
points per line) by:

SET ATTRIBUTE
SET RESOLUTION
PROFILE POINTS

1 to 2000 is acceptable.

Note that you get "n+1", so that your spacing is L/n.



On Mon, 12 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:

>
> Shriram,
>
> Another option for small to medium sized data sets ( < 80,000 elements,
> say), is to use the profile option in postx, which will interrogate the
> solution along a line with up to 2000 points and then report:
>
> x,y,z,u,v,w,p,t,distance along a line  (you choose which quantities you want)
>
> Given this data, you can then derive the wall-tangent velocity profile
> and get the wall shear.
>
> Each line is specified by
>
> x0,y0,z0
> x1,y1,z1
>
> You can list many such X0,X1 pairs in a file, and then you can
> use the MAKE MOVIE option in postx to run through a sequence of
> timesteps.   All profiles are then written to profile.out, which
> I typically process with matlab.
>
> Paul
>
>
> On Mon, 12 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hello,
>> 
>> Background : I am trying to perform a LES in a turbine blade where the
>> stream-wise, pitch-wise and span-wise direction is along X,Y and Z axis.
>> 
>> Question : I would like to calculate the yplus and zplus values for the
>> nodes close to the blade. For calculating the dimensionless wall distances,
>> one would require the velocity gradients in the respective direction or the
>> wall shear stress . I would like to know if there are any subroutines
>> available in nek that would help calculate the wall normal distances or the
>> velocity gradients ?
>> 
>> Any help is greatly appreciated. Thanks
>> 
>> Regards
>> Shriram Jagannathan
>> 
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