[Nek5000-users] Nek5000 simulations of High Re flows ~ 10^5

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

Hi Murph,

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?

Sincerely,

On Wed, Mar 16, 2016 at 2:54 PM <nek5000-users at lists.mcs.anl.gov> wrote:

> 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
>
>
>
> On 3/16/2016 1:00 PM, nek5000-users-request at lists.mcs.anl.gov wrote:
>
> can you send me a picture of that, perhaps off-list? (pschlatt at mech.kth.se).
>
> Thanks,
>
> Philipp
>
>
>
> On 2016-03-16 16:04, nek5000-users at lists.mcs.anl.gov 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 <nek5000-users at lists.mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov> <nek5000-users at lists.mcs.anl.gov>> 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, nek5000-users at lists.mcs.anl.gov
>
>     <mailto:nek5000-users at lists.mcs.anl.gov> <nek5000-users at lists.mcs.anl.gov> wrote:
>
>      > Hello all,
>
>      >
>
>      > I was wondering if anyone on the mailing list has experience with
>
>      > simulating high Re flows of the order 10^5. 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,
>
>      > --
>
>      >
>
>      > **Amitvikram Dutta**
>
>      >
>
>      > *MASc Candidate**
>
>      > *
>
>      >
>
>      > *Graduate Research Assistant *
>
>      >
>
>      > **Okanagan CFD Laboratory**
>
>      >
>
>      > *University of British Columbia | Okanagan Campus***
>
>      >
>
>      >
>
>      >
>
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>
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>
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>
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>
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>
>
> --
>
>
> **Amitvikram Dutta**
>
>
>
> *MASc Candidate**
>
> *
>
>
>
> *Graduate Research Assistant *
>
>
> **Okanagan CFD Laboratory**
>
>
>
>
>
> *University of British Columbia | Okanagan Campus***
>
>
>
>
>
>
> Re: Nek5000 simulations of High Re flows ~ 10^5
>
>
> --
> Murphy Leo O'Dea
> PhD Student
> Oakland Universitymlodea at oakland.edu
>
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-- 

*Amitvikram Dutta*

*MASc Candidate*

*Graduate Research Assistant *

*Okanagan CFD Laboratory*

*University of British Columbia | Okanagan Campus*
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