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

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

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>> 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>  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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>
>       >Nek5000-users at lists.mcs.anl.gov
>
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>
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>
>       >
>
>      _______________________________________________
>
>      Nek5000-users mailing list
>
>      Nek5000-users at lists.mcs.anl.gov  <mailto:Nek5000-users at lists.mcs.anl.gov>
>
>      https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>
>
>
> --
>
>
>
> *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 University
mlodea at oakland.edu

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