[Nek5000-users] energy dissipation over a subdomain

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

Hi Ilias,

As I mentioned to you earlier, for the case when you subdomain integration consists of whole elements, I would do the simplest

      dimension ybm1(lx1*ly1*lz1), rmask(lx1*ly1*lz1,lelt)

      nxyz = nx1*ny1*nz1
      ntot  = nxzy*nelt
      do e=1,nelt
          call rzero(rmask,ntot)
          call col3(ybm1,bm1,nxyz)
          yavg = vlsum(ybm1,nxyz)
          yavg = yavg/vlsum(ym1,nxyz)
          if (yavg.gt.y_something) call rone(rmask(1,1,1,e),nxyz)
      enddo

and then use glsc3 with arguments of bm1, your quantity on GLL mesh, and created rmask.

Note that the above approach with modification will work even for the case of the integration subdomain boundary cutting through the elements but you need to use every GLL's ym1 instead of yavg -- be aware that the spectral convergence of this integration with increase of polynomial order will be affected since it is equivalent to integration of a step/discontinuous function inside an element...

Note also that if the integration subdomain is much smaller than the whole domain, you could compute the collocation with your quantity and bm1 inside the above loop and do summation yourself

Aleks


________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Thursday, October 29, 2015 1:16 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] energy dissipation over a subdomain

Dear neks!

I would like to compute kinetic energy dissipation over different subdomains.

It involves the calculation of the dissipation itself in GLL points,
and integration over some domain.

I understand now that it is more accurate to involve whole number of elements
for integration,
and  that for computation of  the integral over
a subdomain one can use a mask (of 1s and 0es) over the whole domain,
and after that to use global scalar product like glsc3.

Are there the implementations of these ideas?
first of all, the creation of a mask, based on geometrical constructions like
      IF      (Y.gt.something) THEN
...

and also if somebody has already a procedure of kinetic energy dissipation,
though here it is more strait: calculation of of velocity gradient and contraction of
its multiplication with itself,

Thank you, Ilias
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