[Nek5000-users] Rotating computational domain

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

Hi Paul and Phillip,

Thanks for your replies.  I will try to apply ALE to the entire domain and
play with the BCs to try and get a result.  I've already rejected the
standard C-mesh for airfoils in favor of an unstructured circular domain
because the C-mesh boundaries are not conducive to rotating the entire
domain.  If I'm unsuccessful with this approach I will try to apply a
rotating inflow and add a Coriolis force to correct.  In either case, if
everything works out I would like to submit a very small example case to
the Nek documentation to help others in their quest for a rotating domain.
I'll post back here if I run into trouble, thanks again for your insight!

-Harry

On Tue, Aug 21, 2018 at 11:30 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

>
> Hi Harry,
>
>
> One simple approach is to use ALE but to have the entire domain pitch,
>
> thus preserving your mesh structure.
>
>
> That would properly account for all the accelerations in your non inertial
>
> domain.
>
>
> The slightly tricky part would be to determine what BCs you need.  You
>
> need to be careful about changing the character of the BCs (e.g., from
> inflow
>
> to outflow)  in the middle of a computation because that changes which
> quantities
>
> are prescribed and which are unknown.   Perhaps one approach would be
>
> to have a circular domain with 3/4 of it Dirichlet and 1/4 being outflow
> (i.e.,
>
> Neumann for velocity).
>
>
> hth,
>
>
> Paul
>
>
> ------------------------------
> *From:* Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on behalf
> of nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
> *Sent:* Tuesday, August 21, 2018 9:43:56 AM
> *To:* nek5000-users at lists.mcs.anl.gov
> *Subject:* [Nek5000-users] Rotating computational domain
>
> Hello Neks,
>
> I am an undergraduate student new to Nek and I am working on a simulation
> studying dynamic stall in a dynamically pitching airfoil.  I want to do a
> pitch and hold simulation at low Reynold's number (Re = 12000) where I
> rotate the entire computational domain up to about 50 degrees AOA and then
> hold at 50 degrees, with steady inflow ux = 1.  I would like to rotate the
> domain about the z axis, which passes through the quarter chord location of
> the airfoil profile (modified NACA 0012).
>
> Because of the steep AOA, I would like to stay away from pitching the
> airfoil within the stationary domain with ALE to avoid too much mesh
> deformation.  To this end, I have been scouring documentation to try and
> find a method of applying a rotational mesh velocity to the entire domain
> about the z axis while keeping the flow within the domain at ux = 1.  I am
> feeling very stuck.  Others have suggested applying a Coriolis force to the
> flow, but I don't really see how this would simulate rotation of the entire
> domain.  It seems to me that simulation of a Coriolis force would be
> acceptable to correct the flow field to always be ux = 1 inside a rotating
> domain, but I don't see how that would apply a mesh velocity anywhere.
>
> Are there any examples where an entire computational domain is rotated
> that I can look at, or has anybody done similar work who can point me in
> the right direction?
>
> Regards,
> -Harry
>
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>


-- 
Harry E. Werner IV
Secretary
Clarkson University SCUBA Club
*Cell:* (716) 570-4023
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