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Hi,<br>
thanks for the advice. I found that one also has to comment the line<br>
IF (.NOT.IFTRAN) NSTEPS=1<br>
in setvar in drive2.f and use a fixed timestep so that the timeloop
does not stop too soon.<br>
<br>
Thanks again,<br>
Jan<br>
<br>
<div class="moz-cite-prefix">On 08/05/2015 02:30 PM,
<a class="moz-txt-link-abbreviated" href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a> wrote:<br>
</div>
<blockquote
cite="mid:mailman.4940.1438777826.24727.nek5000-users@lists.mcs.anl.gov"
type="cite">
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<div class="moz-text-flowed" style="font-family: -moz-fixed;
font-size: 14px;" lang="x-western">Hello, Jan, <br>
<br>
We have in fact solved a similar problem as you face now. In our
case, we have steady Stokes equation at each time step, <br>
in the absence of time derivative and convection term. However
we have time-dependent volume forcing and boundary <br>
conditions, as we solve for fluid-structure interactions in the
Stokes regime. <br>
<br>
You only need to change the source code for one thing. By
changing the flags in the .rea file, you can easily turn <br>
off the two terms. However, the code only runs for 1 time step
even if you specify for example 10 total time steps, which makes
sense <br>
as NEK realizes this is a steady problem. NEK5000 does not see
that the next time step, BCs and forcing will be changed, and so
<br>
as the flow. <br>
<br>
So I remember I only commented two lines of the source code to
achieve this, in the file 'connect2.f', subroutine 'rdparam', <br>
this is what I have done (i am using a quite old version of the
NEK, so...) <br>
<br>
IF (.NOT.IFTRAN) THEN <br>
c PARAM(11) = 1.0 !lailai comment for steady stokes <br>
c PARAM(12) = 1.0 !lailai comment for steady stokes <br>
PARAM(19) = 0.0 <br>
ENDIF <br>
<br>
Of course you need to set the flags right in .rea file, which
you can find the details on the webpage. You also need to <br>
solve for heat equations to get T. Then in the userchk
subroutine, you calculate the T-dependent buoyancy forcing at
each time step. <br>
Solve the flow with new forcing terms. This should be all
manageable. <br>
<br>
cheers and good luck, <br>
<br>
lailai <br>
<br>
<br>
<br>
On 2015/8/5 12:15, <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a>
wrote: <br>
<blockquote type="cite" style="color: #000000;">Hi all, <br>
I was wondering if it is possible to use Nek5000 for
simulations in the infinite Prandtlnumber regime (e.g.
planetary mantles). This would require to solve the NS Stokes
equation without the time derivative and advection term and
the heat equation for T: <br>
<br>
1) Solve visc * laplace u - grad p + buoyancy = 0 and div u =
0, where bouyancy depends on a given T field and a Rayleigh
number <br>
2) Update T by solving dT/dt + u grad T = diff * laplace T (+
other sources) <br>
3) go back to 1 with the new T field, repeat <br>
<br>
More realistic models would then use a varying viscosity. <br>
I looked at the steady state example (kov_st_state), but this
is missing the time depencence via the Temperature. Any hints
on the possibility would be much appreciated. <br>
<br>
Thanks, <br>
Jan <br>
<br>
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<br>
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href="https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users">https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users</a>
<br>
</blockquote>
<br>
<div class="moz-txt-sig"><span class="moz-txt-tag">-- <br>
</span>Lailai Zhu <br>
Laboratory of Fluid Mechanics and Instabilities LFMI <br>
EPFL STI IGM LFMI ME A2 408 (Bâtiment ME) Station 9 <br>
CH-1015 Lausanne Switzerland <br>
<br>
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<br>
<pre class="moz-signature" cols="72">--
----------------------
Jan Vormann
Institut für Geophysik
Corrensstr. 24
D-48149 Münster</pre>
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