[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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