<div dir="ltr">Hi Murph,<div><br></div><div>Whats your domain size, and how far did you have to reduce grid spacing? I have an airfoil study with a standard C Grid, and that didn't work with a 30000 element mesh and n = 9 polynomial. My timestep had to go down to 10e-6, and still I got blow-up. What about you?</div><div><br></div><div>Sincerely,</div></div><br><div class="gmail_quote"><div dir="ltr">On Wed, Mar 16, 2016 at 2:54 PM <<a href="mailto:nek5000-users@lists.mcs.anl.gov">nek5000-users@lists.mcs.anl.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<pre><span>Amitvikram,
Hi... I'm doing very high Re on some wind turbine wake flows, and yes, I have resolution problems also. I had to drastically reduce my time step/CFL to prevent blowup. Then, my results showed much more "clutter" (poor resolution), and "exposed" the grid element outlines in isosurface plots; I assume from gradients near the element boundaries...
Increasing DOF and reducing grid spacing did help resolve the problem; vortices and other flow structures became much more defined. However, the "exposed grid" is still there, and I have not reduced the grid spacing enough yet to see these artifacts completely removed...
See Ya,
Murph O'Dea
</span></pre></div><div bgcolor="#FFFFFF" text="#000000">
<br>
<br>
<div>On 3/16/2016 1:00 PM,
<a href="mailto:nek5000-users-request@lists.mcs.anl.gov" target="_blank">nek5000-users-request@lists.mcs.anl.gov</a> wrote:<br>
</div>
</div><div bgcolor="#FFFFFF" text="#000000"><blockquote type="cite"><pre>can you send me a picture of that, perhaps off-list? (<a href="mailto:pschlatt@mech.kth.se" target="_blank">pschlatt@mech.kth.se</a>).
Thanks,
Philipp
On 2016-03-16 16:04, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a> wrote:
Hi Philipp,
My Geometry is a 2D C Grid of a NACA airfoil. And yes, wiggles leading
to a blow up are exactly how I would describe my problems.
Sincerely,
On Wed, Mar 16, 2016, 7:47 AM <<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>
<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank"><mailto:nek5000-users@lists.mcs.anl.gov></a>> wrote:
Hi,
what type of problems do you have? Are you looking at a 3D geometry? Do
you get wiggles, which then lead to a blow up?
Best,
Philipp
On 2016-03-15 20:26, <a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank">nek5000-users@lists.mcs.anl.gov</a>
<a href="mailto:nek5000-users@lists.mcs.anl.gov" target="_blank"><mailto:nek5000-users@lists.mcs.anl.gov></a> wrote:
> Hello all,
>
> I was wondering if anyone on the mailing list has experience with
> simulating high Re flows of the order 10<sup><span style="display:inline-block;width:0;min-height:0;overflow:hidden">^</span>5</sup>. I'm studying flow
> instabilities over airfoils and have been struggling to obtain a
stable
> simulation for these high Re flows.
>
> Its worthwhile to note that I have simulated low Re flows using
> identical geometries. Making the mesh finer or increasing the
order of
> the method does not seem to be doing the trick. The simulations
usually
> diverge after something like 5 seconds of flow time.
>
> If there are any specific conditions/settings that I should be
looking
> at, I'd really appreciate the information.
>
> Thanks,
> --
>
> <b><span>*</span>Amitvikram Dutta<span>*</span></b>
>
> *MASc Candidate**
> *
>
> *Graduate Research Assistant *
>
> <b><span>*</span>Okanagan CFD Laboratory<span>*</span></b>
>
> *University of British Columbia | Okanagan Campus***
>
>
>
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--
<b><span>*</span>Amitvikram Dutta<span>*</span></b>
*MASc Candidate**
*
*Graduate Research Assistant *
<b><span>*</span>Okanagan CFD Laboratory<span>*</span></b></pre></blockquote></div><div bgcolor="#FFFFFF" text="#000000"><blockquote type="cite"><pre>
*University of British Columbia | Okanagan Campus***
Re: Nek5000 simulations of High Re flows ~ 10<sup><span style="display:inline-block;width:0;min-height:0;overflow:hidden">^</span>5</sup></pre>
</blockquote></div><div bgcolor="#FFFFFF" text="#000000">
<br>
<pre cols="72">--
Murphy Leo O'Dea
PhD Student
Oakland University
<a href="mailto:mlodea@oakland.edu" target="_blank">mlodea@oakland.edu</a></pre>
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</blockquote></div><div dir="ltr">-- <br></div><div dir="ltr"><p style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;margin-bottom:0cm;line-height:12.8px"><font color="#000033"><font face="georgia, serif" size="2"><b>Amitvikram Dutta</b></font></font></p><p style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;margin-bottom:0cm;line-height:12.8px"><font face="georgia, serif" size="2"><b style="color:rgb(0,0,51);line-height:12.8px">MASc Candidate</b><font color="#000033"><b><br></b></font></font></p><p style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;margin-bottom:0cm;line-height:12.8px"><font color="#000033"><font face="georgia, serif" size="2"><b>Graduate Research Assistant </b></font></font></p><p style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;margin-bottom:0cm;line-height:12.8px"><font color="#000033"><font face="georgia, serif" size="2"><b>Okanagan CFD Laboratory</b></font></font></p><p style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;margin-bottom:0cm;line-height:12.8px"><font color="#000033" style="font-size:small;line-height:normal"><span style="line-height:12.8px"><b><font face="georgia, serif">University of British Columbia | Okanagan Campus</font></b></span></font><font color="#000033" face="georgia, serif" style="font-size:small;line-height:13px"><b> </b></font></p></div>