[Nek5000-users] Stream function

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

Hi Philipp,

Thanks very much for your comments.  Yes, the delta* works only for the parallel plate.  

The streamfunction computation with the Blasius example is still not working. I suspect I am not using the correct mask (vmult /tmult, imsh as well). 

Using the Blasius example, v1mask, vmult (imsh = 1), I dumped the streamfuntion to the temperature field. However, it only contains negative values and does not look physical (I pasted userchk below). 

Another Nek Example, “mv_wall”, computes the streamfunction from the Possison equation using vorticity. It uses tmask, tmult, and imsh = 2. 

I tried implementing what was done in the “mv_wall” example in the Blasius example, but the computed streamfunction is zero everywhere.

Any ideas what I might be doing wrong?

Any advice would be appreciated! 

Thanks again, 

Hannah  

c-----------------------------------------------------------------------
      subroutine userchk
      include 'SIZE'
      include 'TOTAL'

      common /myblas/ ub(lx1,ly1,lz1,lelt),vb(lx1,ly1,lz1,lelt)

      common /blasiusr/ u(lx1,ly1,lz1,lelv),v(lx1,ly1,lz1,lelv)
      common /blasiusg/ bin(lx1,ly1,lz1,lelv)
      common /scrns/    dum(lx1*ly1*lz1*lelv)

      common /xtream/ psi(lx1*ly1*lz1*lelt)
     $              , rhs(lx1*ly1*lz1*lelt)
     $              , h1 (lx1*ly1*lz1*lelt)
     $              , h2 (lx1*ly1*lz1*lelt)

      parameter (lt=lx1*ly1*lz1*lelt)
      common /scrns/ vort(lt,3),w1(lt),w2(lt)

      integer bin
      real normu(50),normv(50)

      real xmax,xmin,dx
      save xmax,xmin,dx

      n = nx1*ny1*nz1*nelv
      ifheat=.false.
      call comp_vort3(vort , w1, w2, vx, vy, vz)
      call copy (t,vort,n)   ! Vorticity --> T
      ifto = .true.          ! Dump vorticity as T
c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
c     Compute streamfunction from vorticity
      call col3 (rhs,t,bm1,n) ! B*omega
      call rone (h1,n)
      call rzero(h2,n)

      ifield = 1
      tol    = param(22)
      imsh   = 1
      call hmholtz('psi ',psi,rhs,h1,h2,v1mask,vmult,imsh,
     $        tol,200,1)
      call copy (t,psi,n)    ! Psi --> T (for output)
c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

      nfldt = 1 + npscal

      if (istep.eq.0) call outpost2(vx,vy,vz,pr,t,nfldt,'   ')

      do i=1,n
         dum(i) = 1.-vx(i,1,1,1)
      enddo
      tot_deficit = glsc2(dum,bm1,n)
      xmin        = glmin(xm1,n)
      xmax        = glmax(xm1,n)
      delta_star  = tot_deficit/(xmax-xmin)
      tmin        = glmin(t,n)
      tmax        = glmax(t,n)
      vortmin      = glmin(vort,n)
      vortmax      = glmax(vort,n)
      if (nid.eq.0) write(6,1) istep,time,delta_star,vortmin,vortmax
      if (nid.eq.0) write(6,1) istep,tmin,tmax
    1 format(i8,1p4e13.5,'  blasius: delta*')

      return
      end
c-----------------------------------------------------------------------


________________________________________
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: Tuesday, June 26, 2018 1:22 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] Stream function

Hi,
To correctly compute the stream function, the rhs of the Poisson
equation needs to be the (negative) vorticity. Therefore, the line

    call col2(rhs,bm1,n)

is wrong, and should be something like

    call col3(rhs, vorticity, bm1, n)

where vorticity should be the computed vorticity using comp_vort.

I guess your calculation of delta* only works for parallel boundary layers.

Philipp



On 2018-06-26 18:35, nek5000-users at lists.mcs.anl.gov wrote:
> Hi Phillip,
>
> I am using the “Blasius” example test outputting the streamfunction as a
> scalar.
>
> I included my code below. I am not sure what I am doing wrong.
>
> In userchk, I added “compute streamfunction from vorticity” from the
> psi_omega example, but it does not compute the psi properly… (max_psi =
> min_psi = 0 in every step)
>
> c-----------------------------------------------------------------------
>
>        subroutine userchk
>
>        include 'SIZE'
>
>        include 'TOTAL'
>
>        common /myblas/ ub(lx1,ly1,lz1,lelt),vb(lx1,ly1,lz1,lelt)
>
>        common /blasiusr/ u(lx1,ly1,lz1,lelv),v(lx1,ly1,lz1,lelv)
>
>        common /blasiusg/ bin(lx1,ly1,lz1,lelv)
>
>        common /scrns/    dum(lx1*ly1*lz1*lelv)
>
>        common /xtream/ psi(lx1*ly1*lz1*lelt)
>
>       $              , rhs(lx1*ly1*lz1*lelt)
>
>       $              , h1 (lx1*ly1*lz1*lelt)
>
>       $              , h2 (lx1*ly1*lz1*lelt)
>
>        integer bin
>
>        real normu(50),normv(50)
>
>        real xmax,xmin,dx
>
>        save xmax,xmin,dx
>
>        n = nx1*ny1*nz1*nelv
>
> c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
>
> c     Compute streamfunction from vorticity
>
>        call col2(rhs,bm1,n)
>
>        call rone (h1 ,n)
>
>        call rzero(h2 ,n)
>
>        tol = param(22)
>
>        imsh   = 1
>
>        call hmholtz('psi ',psi,rhs,h1,h2,v1mask,vmult,imsh,tol,200,1)
>
> c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
>
>        if (istep.eq.0) call outpost(vx,vy,vz,pr,psi,'   ')
>
> c     Compute delta*
>
>        do i=1,n
>
>           dum(i) = 1.-vx(i,1,1,1)
>
>        enddo
>
>        tot_deficit = glsc2(dum,bm1,n)
>
>        xmin        = glmin(xm1,n)
>
>        xmax        = glmax(xm1,n)
>
>        delta_star  = tot_deficit/(xmax-xmin)
>
>        psimin      = glmin(psi,n)
>
>        psimax      = glmax(psi,n)
>
>        if (nid.eq.0) write(6,1) istep,time,delta_star,psimin,psimax
>
>      1 format(i8,1p4e13.5,'  blasius: delta*')
>
>        return
>
>        end
>
>
>
> _______________________________________________
> Nek5000-users mailing list
> Nek5000-users at lists.mcs.anl.gov
> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>
_______________________________________________
Nek5000-users mailing list
Nek5000-users at lists.mcs.anl.gov
https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users