[Nek5000-users] Temperature Perturbation Zone

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

Hi Nicolas,


OK.  You probably don't want to do that every time step (I'm just guessing...), but in any case, you would do it as written below.


Best, Paul


  do i=1,n
          x=xm1(i,1,1,1)
          y=ym1(i,1,1,1)
          z=zm1(i,1,1,1)

          if(x.ge.px1.and.x.le.px2)then
          if(z.ge.pz1.and.z.le.pz2)then
               t(i,1,1,1,1) = t(i,1,1,1,1) + perturb
          endif
          endif
      end do

________________________________
From: Nek5000-users <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: Monday, May 14, 2018 8:21:28 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] Temperature Perturbation Zone

Hi Paul,

It's not the boundary temperature what I'm trying to modify but a arbitrary zone inside the fluid domain. Boundary condition are 6 walls, 4 isolated and 2 with constant temperature, but that is already settled up.

After reading some entries on the mailing list I tried this

-----------------------------------------------------------------
      subroutine userchk()

      include 'SIZE'
      include 'TOTAL'

      real period,amplitude,perturb
      real px1,px2,py1,py2
      integer n

      amplitude = 1.2
      period = 0.75
      perturb = amplitude * sin( (2.0*pi/period)*time )

      px1 = 0.25/2.0-0.05
      px2 = 0.25/2.0+0.05
      pz1 = 0.5-0.1
      pz2 = 0.5+0.1

      n = lx1*ly1*lz1*nelt

      do i=1,n
          x=xm1(i,1,1,1)
          y=ym1(i,1,1,1)
          z=zm1(i,1,1,1)

          if(x.ge.px1.and.x.le.px2)then
          if(z.ge.pz1.and.z.le.pz2)then
(1)              temp = temp + perturb      ! Nothing happens
(2)              t = t + perturb                   ! WARNING: DIV(V)-QTL too large!
          endif
          endif
      end do

      return
      end
-----------------------------------------------------------------

After running the simulations, with (1) I get the same results that without it; with (2) the solver indicates "WARNING: DIV(V)-QTL too large!" in every timestep, makes some really small timesteps (1e-5 sec. vs 1e-2) and doesn't seem to converge.

I guess that the addition of the perturbation is bad defined.



Nicolás

Nicolás Andrés Órdenes Leiva

Estudiante de Ingeniería Civil Mecánica
Universidad Técnica Federico Santa María
Tel: +56 9 7619 2857

2018-05-14 19:15 GMT-04:00 <nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov>>:

Dear Nicolas,


For time-dependent boundary conditions, you could

use something like the expression you have in your email.


You would need "t  " ( "tee" space space) for the thermal

boundary conditions in your .rea or .box file.


Please let me know if this solves your problem.


Paul


________________________________
From: Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov<mailto:nek5000-users-bounces at lists.mcs.anl.gov>> on behalf of nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov> <nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov>>
Sent: Monday, May 14, 2018 5:26:23 PM
To: nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov>
Subject: [Nek5000-users] Temperature Perturbation Zone

Hi,

I'm setting a 3D box to perform natural convection problems in a closed cavity. After trying several method i can't manage to define a zone with a variable temperature perturbation in the usrchk() routine.

Let's say, that temp = temp + A*sin(w*time) in a square of boundaries [x_min, x_max] x [y_min, y_max] x [z_min, z_max] for x, y, z.

Any advice for implementing this?

Regards,

Nicolás Andrés Órdenes Leiva

Estudiante de Ingeniería Civil Mecánica
Universidad Técnica Federico Santa María
Tel: +56 9 7619 2857

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