[Nek5000-users] perturbing interior variables
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Tue May 11 17:20:56 CDT 2010
On Tue, 2010-05-11 at 17:14 -0500, nek5000-users at lists.mcs.anl.gov
wrote:
> Hi Frank,
>
> Yes - any function that is supposed to be continuous should be
> so at timestep 0, else there will be problems.
Hi Paul,
But if one is perturbing the velocity and/or temperature not at t=0 but
at a later time (in "userchk") then "dsavg" should still be called?
Cheers,
Frank
>
> For the Pn-Pn-2 formulation, pressure is discontinuous, so there
> is no issue for pressure in this case.
>
> However, one would call dsavg for vx, vy,vz and T ---
>
> This is already done in ic.f following standard initialization
> procedures.
>
> It likely wouldn't need to be done if you range strictly over
> the element interiors, i,j,k \in [2,...,nx1]^3 --- but it
> wouldn't hurt in any case.
>
> Paul
>
>
> On Tue, 11 May 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
> > Hi Paul,
>
> I'm not quite sure what you mean here, am assuming you have in mind
> continuous across element boundaries. At present, some simulations are
> running where at a certain time, the temperature field is perturbed as
> in the code segment below. Would the absence of "dsavg" cause a problem
> regardless of whether one loops from "k=2,nz1-1" or "k=1,nz1" etc.?
> Also, is "dsavg" needed when dealing with velocity?
>
> Cheers,
> Frank
>
> if(time>1. .and. time<= 1.+2.5*dt)then
> write(*,*)'Symmetry breaking'
> vmax=.01 ; tmax=.99 ; radius=1.5 ; radius_s=.25
> nlocations_perturbed=3
> do 100 iel=1,nelv
> do 100 k=2,nz1-1
> do 100 j=2,ny1-1
> do 100 i=2,nx1-1
> do n=1,nlocations_perturbed
> angle = acos(-1.)*2.*(n-1.)/nlocations_perturbed
> x1=radius*cos(angle) ; y1=radius*sin(angle)
> if(((xm1(i,j,k,iel)-x1)**2
> & + (ym1(i,j,k,iel)-y1)**2
> & + (zm1(i,j,k,iel)-.45)**2)**.5.le.radius_s)then
> t(i,j,k,iel,1)=tmax*t(i,j,k,iel,1)
> endif
> enddo !n
> 100 continue
> endif !time>1. .and. time<= 1.+2.*dt
>
>
> On Tue, 2010-05-11 at 07:38 -0500, nek5000-users at lists.mcs.anl.gov
> wrote:
> > Hi Frank,
> >
> > One additional note.
> >
> > It's important that your perturbed T() be continuous.
> >
> > This could be done, e.g., via the following code in userchk
> >
> > if (istep.eq.0) then
> > n=nx1*ny1*nz1*nelt
> > do i=1,n
> > t(i,1,1,1,1) = t(i,1,1,1,1) + perturbation of choice
> > enddo
> > call dsavg(t)
> > endif
> >
> > The dsavg() will ensure that T is continuous. If T is not
> > continuous at the beginning, it will be discontinous forever
> > since we only solve for delta T and then add this to T.
> >
> >
> > Paul
> >
> >
> > On Tue, 11 May 2010, nek5000-users at lists.mcs.anl.gov wrote:
> >
> > >
> > >
> > > Hi Frank,
> > >
> > > Boundary values will be set by userbc().
> > >
> > > There is no opportunity to intercede between userbc() being called
> > > and the solver. (In effect, userbc() _is_ the opportunity to
> > > intercede.)
> > >
> > > userchk is called at the end of each step and therefore effectively
> > > at the beginning of the next. Perturbing there will work - you can
> > > perturb all values and rest assured that values on Dirichlet surfaces
> > > will be overwritten by userbc. Values on Neumann surfaces, however,
> > > would not be reset by userbc.
> > >
> > > hth,
> > >
> > > Paul
> > >
> > > On Tue, 11 May 2010, nek5000-users at lists.mcs.anl.gov wrote:
> > >
> > >> Thanks for the replies, Aleks and Stefan. I am still not clear on one
> > > point though. Are changes made to temperature or velocity on boundaries
> > > in "userchk" at each time step irrelevant since they are overwritten by
> > > calls to "userbc"?
> > >
> > > Cheers,
> > > Frank
> > >
> > >
> > > On Mon, 2010-05-10 at 18:15 +0200, nek5000-users at lists.mcs.anl.gov
> > > wrote:
> > >> The heat solver calls BCDIRSC which will apply Dirichlet bcs. All 't '
> > >> boundary points call userbc so you have the full control over the values at
> > >> the boundary.
> > >>
> > >> Stefan
> > >>
> > >>
> > >>
> > >>
> > >> On May 10, 2010, at 6:00 PM, nek5000-users at lists.mcs.anl.gov wrote:
> > >>
> > >> > Hi Frank,
> > >> > > > I assume that you refer to t(i,j,k,iel) as temperature -- to be safe
> > >> it should be t(i,j,k,iel,1)...
> > >> > > > In timestepping loop, subroutine userchk is called last by one --
> > >> right before the last one -- prepost which dumps field files .f or .fld --
> > >> see nek5_svn/trunk/nek/drive1.f:
> > >> > > DO ISTEP=1,NSTEPS
> > >> > call nek_advance
> > >> > call userchk
> > >> > call prepost (.false.,'his')
> > >> > if (lastep .eq. 1) goto 1001B
> > >> > ENDDO
> > >> > > while, as I can see, userbc for a passive scalar is called from a chain
> > >> of subroutines nek_advance > heat > cdscal > BCNEUSC/BCDIRSC
> > >> > > This means that perturbation of temperature at the boundary won't be
> > >> overwritten in userbc.
> > >> > > > One way to apply perturbation everywhere including the element faces
> > >> that are not on the boundary of your domain is simply to multiply your
> > >> perturbation factor by a function that goes to zero on the boundaries,
> > >> e.g.:
> > >> > > t(i,j,k,iel,1)=.99*t(i,j,k,iel,1)*(xm1(i,j,k,iel)**2.-1.)
> > >> > > in case the boundary surface plane is at x=1 & x=-1
> > >> > > Best,
> > >> > Aleks
> > >> > > > > > > > On Mon, 10 May 2010, nek5000-users at lists.mcs.anl.gov wrote:
> > >> > >> Hello all,
> > >> > > I am trying to perturb the temperature in a small part of the flow.
> > >> > However, I only wish to perturb in the interior and not on a boundary.
> > >> > I have the following in "userchk". If I instead looped from "k=1,nz1"
> > >> > instead of "k=2,nz1-1", would this change the BC's? The general
> > >> > question would be, does changing uvw & T in "userchk" change BC's or
> > >> > does "userbc" override what is done in "userchk"?
> > >> > > Cheers,
> > >> > Frank
> > >> > > do 100 iel=1,nelv
> > >> > do 100 k=2,nz1-1
> > >> > do 100 j=2,ny1-1
> > >> > do 100 i=2,nx1-1
> > >> > if(((xm1(i,j,k,iel)-1.1)**2
> > >> > & + (ym1(i,j,k,iel)-1.1)**2
> > >> > & + (zm1(i,j,k,iel)-.45)**2)**.5.le..25)then
> > >> > t(i,j,k,iel)=.99*t(i,j,k,iel)
> > >> > endif
> > >> > enddo !n
> > >> > 100 continue
> > >> > > > > > -- > Frank Herbert Muldoon, Ph.D. Mechanical Engineering
> > >> > Technische Universität Wien (Technical University of Vienna)
> > >> > Inst. f. Strömungsmechanik und Wärmeübertragung (Institute of Fluid
> > >> > Mechanics and Heat Transfer)
> > >> > Resselgasse 3
> > >> > 1040 Wien
> > >> > Tel: +4315880132232
> > >> > Fax: +4315880132299 Cell:+436765203470
> > >> > fmuldoo (skype)
> > >> >
> > >> http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html
> > >> > > _______________________________________________
> > >> > Nek5000-users mailing list
> > >> > Nek5000-users at lists.mcs.anl.gov
> > >> >
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> > >>
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> > > --
> > > Frank Herbert Muldoon, Ph.D. Mechanical Engineering
> > > Technische Universität Wien (Technical University of Vienna)
> > > Inst. f. Strömungsmechanik und Wärmeübertragung (Institute of Fluid
> > > Mechanics and Heat Transfer)
> > > Resselgasse 3
> > > 1040 Wien
> > > Tel: +4315880132232
> > > Fax: +4315880132299 Cell:+436765203470
> > > fmuldoo (skype)
> > > http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html
> > >
> > > _______________________________________________
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> > _______________________________________________ Nek5000-users mailing list Nek5000-users at lists.mcs.anl.gov https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
> --
> Frank Herbert Muldoon, Ph.D. Mechanical Engineering
> Technische Universität Wien (Technical University of Vienna)
> Inst. f. Strömungsmechanik und Wärmeübertragung (Institute of Fluid
> Mechanics and Heat Transfer)
> Resselgasse 3
> 1040 Wien
> Tel: +4315880132232
> Fax: +4315880132299
> Cell:+436765203470
> fmuldoo (skype)
> http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html
>
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> _______________________________________________ Nek5000-users mailing list Nek5000-users at lists.mcs.anl.gov https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
--
Frank Herbert Muldoon, Ph.D. Mechanical Engineering
Technische Universität Wien (Technical University of Vienna)
Inst. f. Strömungsmechanik und Wärmeübertragung (Institute of Fluid
Mechanics and Heat Transfer)
Resselgasse 3
1040 Wien
Tel: +4315880132232
Fax: +4315880132299
Cell:+436765203470
fmuldoo (skype)
http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html
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