<div dir="ltr">Hi Paul,<div><br></div><div>Thanks for the diagnosing this problem. Indeed it is bad initial data. At the moment I do not have specific initial data or forcing to work with and so I'm just trying out the feasibility of using NEK to solve on the shell. I should have some concrete initial data in the next couple of days. </div>
<div><br></div><div>When I try to repeat the run with </div><div><br></div><div>ux = 0.0</div><div>uy = 0.0</div><div>uz = 0.0</div><div><br></div><div>and </div><div><br></div><div>ffx = 0.0</div><div>ffy = 0.0</div><div>
ffz = 1.0</div><div><br></div><div>NEK shows a lot of convergence errors. Could you check this out?</div><div><br></div><div>I've attached the .rea file.</div><div><br></div><div>Thanks,</div><div>Mani<br><br><div class="gmail_quote">
On Sun, Aug 14, 2011 at 5:31 PM, <span dir="ltr"><<a href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br>
Hi Mani,<br>
<br>
I ran this with<br>
<br>
G="-g -Ktrap=fp"<br>
<br>
and the "nekd" script in serial (just gdb nek5000 after<br>
setting up requisite files).<br>
<br>
Here is the output:<br>
<br>
Program received signal SIGFPE, Arithmetic exception.<br>
0x000000000040376c in useric_ (ix=1, iy=1, iz=1, ieg=3)<br>
at /homes/fischer/nek_debug/mani/<u></u>z.f:83<br>
83 utheta = 1.0/(x**2 + y**2)**0.5<br>
(gdb)<br>
<br>
<br>
This makes sense -- you have a pole singularity in<br>
this formulation. I'm certain it's a removable singularity if you just rework your ux/uy velocity<br>
definition.<br>
<br>
Please let me know if this resolves the issue.<br>
<br>
Paul<div><div></div><div class="h5"><br>
<br>
<br>
<br>
<br>
On Sun, 14 Aug 2011, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.<u></u>gov</a> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Paul,<br>
<br>
I setup a simulation but I keep getting NaN's when I give nontrivial initial data. I'm attaching the relevant files. Could you please try it out?<br>
<br>
I checked that the initial data is divergence free and satisfies the boundary conditions (u_r = 0, du_theta/dr = 0, du_phi/dr = 0).<br>
<br>
Regards,<br>
Mani<br>
<br>
On 08/11/2011 05:46 PM, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.<u></u>gov</a> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Hi Mani,<br>
<br>
Probably your best bet is to use a very thin layer of elements<br>
in a 3D spherical shell with SYM bcs on faces 5 & 6, plus the<br>
stress formulation. I would imagine that a shell of thickness<br>
.001 with R=1.0 might be feasible.<br>
<br>
Instructions for constructing a 3D shell can be found in<br>
<a href="http://www.mcs.anl.gov/~fischer/primer.pdf" target="_blank">www.mcs.anl.gov/~fischer/<u></u>primer.pdf</a><br>
<br>
(Some of this info may already have been transferred into<br>
current manual.) We can help with this if you need any<br>
assistance.<br>
<br>
Regards,<br>
<br>
Paul<br>
<br>
<br>
On Thu, 11 Aug 2011, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.<u></u>gov</a> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Nek devs,<br>
<br>
Is it possible to use NEK to solve for Navier Stokes equations on the<br>
surface of a sphere, where r is fixed and the velocity varies in theta and<br>
phi?<br>
<br>
Thanks,<br>
Mani Chandra<br>
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