[Nek5000-users] Rotating computational domain

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

I guess in the end it amounts to the same as having ALE on the entire 
domain, but you can do a combination of changing the inflow and adding 
fictitious forces on the flow. In this way you account for the 
accelerations explicitly using forcing terms (as opposed to ALE where 
you get the same "implicitly"). I guess it works, but you might get 
quite high accelerations further away from the axis. I remember we tried 
it at some point but I am unsure of the outcome.
Philipp

On 2018-08-21 17:30, 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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