[Nek5000-users] Solving for fluid flows on a sphere

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

Hi Mani,

I ran this with

G="-g -Ktrap=fp"

and the "nekd" script in serial (just gdb nek5000 after
setting up requisite files).

Here is the output:

Program received signal SIGFPE, Arithmetic exception.
0x000000000040376c in useric_ (ix=1, iy=1, iz=1, ieg=3)
     at /homes/fischer/nek_debug/mani/z.f:83
83            utheta = 1.0/(x**2 + y**2)**0.5
(gdb)


This makes sense -- you have a pole singularity in
this formulation.  I'm certain it's a removable 
singularity if you just rework your ux/uy velocity
definition.

Please let me know if this resolves the issue.

Paul




On Sun, 14 Aug 2011, nek5000-users at lists.mcs.anl.gov wrote:

> Hi Paul,
>
> 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?
>
> 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).
>
> Regards,
> Mani
>
> On 08/11/2011 05:46 PM, nek5000-users at lists.mcs.anl.gov wrote:
>> 
>> Hi Mani,
>> 
>> Probably your best bet is to use a very thin layer of elements
>> in a 3D spherical shell with SYM bcs on faces 5 & 6, plus the
>> stress formulation.  I would imagine that a shell of thickness
>> .001 with R=1.0 might be feasible.
>> 
>> Instructions for constructing a 3D shell can be found in
>> www.mcs.anl.gov/~fischer/primer.pdf
>> 
>> (Some of this info may already have been transferred into
>> current manual.)   We can help with this if you need any
>> assistance.
>> 
>> Regards,
>> 
>> Paul
>> 
>> 
>> On Thu, 11 Aug 2011, nek5000-users at lists.mcs.anl.gov wrote:
>> 
>>> Hi Nek devs,
>>> 
>>> Is it possible to use NEK to solve for Navier Stokes equations on the
>>> surface of a sphere, where r is fixed and the velocity varies in theta and
>>> phi?
>>> 
>>> Thanks,
>>> Mani Chandra
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>>> Nek5000-users at lists.mcs.anl.gov
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>>> 
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>
>