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

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

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
>