[Nek5000-users] Initial Condition & Recycling

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

Dear Paul,


Indeed thanks for the input However, the volume average velocity still 
tends to zero and as a consequence the rescaling routine tries to 
compensate making the code unstable until it diverges. The reason why 
the volume average velocity tends to zero could simply be because the 
flow relaminarizes in the absence of fluctuations in the prescribed 
inlet. From my understanding the recycling routine only rescales the 
flow to a target mean velocity without adding fluctuations.

To be sure of that change of dynamic I set up a simulation with a 
(1/7)th velocity profile at the inlet (same code but without recycling) 
convinced that the flow would laminarize and tend to a "blasius-like" 
profile. To my surprise the flow remained steady.

Finally as I want to use a dynamic Smagorinsky model for this project I 
set the filtering to none and variable properties to TRUE however it 
seems that there is a division by zero which I couldn't trace back in 
the source code.


Just after starting to compute the eddy viscosity :


  Calculating eddy visosity
  flt amp 0.0000 0.0000 0.0000 0.0000 0.0000 0.0500 0.5000 0.9500
  flt trn 1.0000 1.0000 1.0000 1.0000 1.0000 0.9500 0.5000 0.0500
forrtl: severe (71): integer divide by zero
Image              PC                Routine Line        Source
nek5000            00000000008CF105  Unknown Unknown  Unknown
libpthread-2.17.s  00002B44DF7BD370  Unknown Unknown  Unknown
nek5000            00000000005D70BE  Unknown Unknown  Unknown
nek5000            0000000000408121  Unknown Unknown  Unknown
nek5000            0000000000404D3F  Unknown Unknown  Unknown
nek5000            000000000040F572  Unknown Unknown  Unknown
nek5000            000000000040E0DF  Unknown Unknown  Unknown
nek5000            0000000000404A1E  Unknown Unknown  Unknown
libc-2.17.so       00002B44DFCEDB35  __libc_start_main Unknown  Unknown
nek5000            0000000000404929  Unknown Unknown  Unknown


Sincerely,
Armand.

Le 07/06/2018 à 15:43, nek5000-users at lists.mcs.anl.gov a écrit :
>
>
> Dear Armand,
>
>
> The attached .usr file seems to work ok... just a few
>
> small modifications to the .usr file you provided.
>
>
> I think the main issue was the declaration of some of the
>
> variables in useric.
>
>
> Best,
>
>
> 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:* Thursday, June 7, 2018 3:51:09 AM
> *To:* nek5000-users at lists.mcs.anl.gov
> *Subject:* [Nek5000-users] Initial Condition & Recycling
> Dear All,
>
>
> In an attempt to simulate an established turbulent flow over a flat
> plate with a recycling method for the inlet, it has to my attention that
> a (1/7)th Power Law would be suitable as an initial condition. However
> the solver divergences and I think I know why.
>
> Here the layout of the recycling procedure :
>
> 1. call set_inflow_fpt in userchk
>
> 2. If it is the 1st call then call setp_inflow_fpt_setup
>
> 3. call rescale_fpt (which rescales the copied field to a user specified
> mean velocity ubar)
>
> 4.In the rescale_fpt routine we call get_flux_and_area which gives the
> flux and area of a face with cbc == 'v   ' so a user specified velocity
> boundary condition.
>
> 4. a) As the initial condition is wrong once that routine sums the flux
> on the boundary it returns zero in this case and the variable scale
> which is divided by the latter returns infinity !
>
>
> However I set the initial conditions as in many other examples, such as
> the turbInflow. Would have an insight that could lead me to a solution ?
>
>
> Please find attached the related files.
>
>
> Sincerely,
>
> Armand, ONERA - The French Aerospace Lab.
>
>
>
>
> _______________________________________________
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