[Nek5000-users] Linearised Navier Stokes

Thu Aug 17 08:33:13 CDT 2017

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:

> 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> 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 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> 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 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 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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