[Nek5000-users] Linearised Navier Stokes

nek5000-users at lists.mcs.anl.gov nek5000-users at lists.mcs.anl.gov
Fri Aug 18 03:49:24 CDT 2017


Hi
    I could no find the ###.ma2 file for the dfh_cav example. Hence I
suppose I require the ###.box or the ###.map file to proceed for the base
flow. Please correct me if I have misunderstood.

Swarandeep

On Fri, Aug 18, 2017 at 1:03 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi Swarandeep,
>
> For computing the base flow you can use the same mesh and map file. What
> you need to change is 1) the boundary conditions such that they are valid
> for the base flow and 2) the flags that you run a nonlinear instead of a
> linear case.
>
> As Clio was saying, in that particular case the base flow was computed
> using a Newton method. For lower Rayleigh numbers, you should however be
> able to just run (nonlinear) DNS to reach the steady state.
>
> Best regards,
> Philipp
>
> On 2017-08-17 20:23, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hi Clio and Adam,
>>
>>         Thanks for the information.
>>
>>   I think in order to compute the base flow I need the ###.box file as
>> well as a different ###.usr file as I think the boundary and initial
>> conditions for the ###.usr file in the short_tests/dfh_cav directory is
>> applicable for the perturbations only. Please send me the ###.box and the
>> corresponding ###.usr file applicable for the base flow for dfh_cav case.
>>
>> Swarandeep
>>
>>
>> On Thu, Aug 17, 2017 at 7:03 PM, <nek5000-users at lists.mcs.anl.gov
>> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>>
>>     Hi Swarandeep,
>>
>>     The baseflow has been computed with a Newton solver (which is not
>>     available in the nek examples). The additional code had been
>>     implemented in the version 1040 of nek5000, and there is no .par
>>     file for that. However, in general, if your case is laminar, to
>>     compute a baseflow, you just need to evaluate the steady state of
>>     your nonlinear case. For that, you can use the same .par file, and
>>     just change to the nonlinear solver (perturbationmodes = 0,
>>     perturbations = no, solveBaseflow = yes).
>>
>>     The non dimensionalization is based on Hellums and Churchill (1962).
>>
>>     The equations are:
>>
>>     Pr (du/dt + (U*nabla)u + (u*nabla)U) = 1/sqrt(Ra)laplacian(u) -grad
>>     p + e_g theta
>>     d theta/dt + (u*nabla)Theta + (U*nabla)theta =
>>     1/sqrt(Ra)laplacian(theta)
>>     div(u)=0
>>
>>     where u, theta are respectively the velocity and temperature of the
>>     perturbation, U, Theta the velocity and temperature of the baseflow.
>>
>>     You can find more information in the paper "Saglietti, Clio, et al.
>>     "Adjoint optimization of natural convection problems: differentially
>>     heated cavity." Theoretical and Computational Fluid Dynamics (2016):
>>     1-17." on which the example is based.
>>
>>     Regards,
>>
>>     clio
>>
>>
>>     Quoting nek5000-users at lists.mcs.anl.gov
>>     <mailto:nek5000-users at lists.mcs.anl.gov>:
>>
>>         Hi Adam,
>>
>>         Thanks for the clarification. Can you please send me a sample
>>         .par file for
>>         the baseflow for the case of "dfh_cav". Also is it possible to
>>         get the
>>         equations solved for this problem(dfh_cav). I would like to know
>>         the way
>>         that this has been made dimensionless.
>>
>>         For your kind information I briefly describe my case which I
>>         have been used
>>         to solve with the regular non-linear framework using older
>>         versions (.rea
>>         files). My setup is as follows:
>>         Geometry is a 3D cylindrical annullus.
>>         Temperature are fixed at inner and outer cylinders.
>>         Gravity is acting in -z direction
>>         There is a back ground rotation which is constant.
>>
>>         Please let me know if any other info is required. Thanks for the
>>         help.
>>
>>         Swarandeep
>>
>>
>>
>>
>>         On Thu, Aug 17, 2017 at 1:48 PM,
>>         <nek5000-users at lists.mcs.anl.gov
>>         <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>>
>>             Hi Swarandeep,
>>
>>             Yes. You generate ###.rea in the standard way. In the old
>>             version it was
>>             txt and contained both mesh information and runtime
>>             parameter. One could
>>             split mesh information (###.re2, binary file) and runtime
>>             parameters
>>             (###.rea with negative number of elements or currently
>>             ###.par) using
>>             reatore2 tool. The map file is generated with genmap (can be
>>             txt or
>>             binary). So the procedure is more or less the same. If you
>>             have ###.rea
>>             with mesh you split it and generate ###.re2. Next you
>>             generate ###.map with
>>             genmap and finally ###.par by hand. Be careful to use tolls
>>             from the same
>>             release, as they've been changed significantly (e.g. binary
>>             ###.map file).
>>             Regards
>>             Adam
>>
>>
>>             On 16/08/17 18:52, nek5000-users at lists.mcs.anl.gov
>>             <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>
>>             Hi Adam,
>>
>>                       Thank you very much for the help.
>>
>>                       Does the ###.map, ###.box file  and from them the
>>             ###.rea file
>>             (in the dfh_cav case: the ###.re2 files)  are created as
>>             done for the
>>             earlier versions i.e., by using genbox and genmap. Please
>>             clarify.
>>
>>             Swarandeep
>>
>>
>>
>>             On Wed, Aug 16, 2017 at 5:35 PM,
>>             <nek5000-users at lists.mcs.anl.gov
>>             <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>>
>>                 Hi,
>>
>>                 The simplest way would be to look into existing example
>>                 under
>>                 Nek5000/short_test/dfh_cav/
>>                 It is a differentially heated cavity case and covers
>>                 both direct and
>>                 adjoint linear solver. It is compatible with the current
>>                 git version and
>>                 uses ###.par file instead of ###.rea.
>>                 Regards
>>                 Adam
>>
>>
>>
>>
>>
>>                 On 11/08/17 11:05, nek5000-users at lists.mcs.anl.gov
>>                 <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>
>>                     This information might be outdated (old version) but
>>                     previously the base
>>                     flow was read in using the restart option in the rea
>>                     file. The disturbance
>>                     you can read in yourself in userchk.
>>
>>                     Philipp
>>
>>                     On 2017-08-11 10:49, nek5000-users at lists.mcs.anl.gov
>>                     <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>>
>>                         Hi Philipp,
>>
>>                                That was very much helpful. I have a
>>                         steady base flow and
>>                         temperature state. Please let me know where to
>>                         provide the base flow.
>>
>>
>>                         Thank you
>>                         Swarandeep
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