[Nek5000-users] turbulent heat transfer

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

Dear Alex,

OK... that's clearly an error in the documentation.

As with param 2, a negative param 8 implies p8=1/|p8|,
so that |input value| = Peclet number.

My apologies for the confusion.  We'll update the wiki.

Thanks,

Paul



On Wed, 13 Feb 2013, nek5000-users at lists.mcs.anl.gov wrote:

> Dear Paul
>
> thanks for your quick answer. We thought we were imposing the Prandtl
> number since in the
> web we found the following information
>
> P008  CONDUCT     conductivity for the case of constant properties (see
>                 parameter P030)   if <0, it defines the Prandtl number
>
> Is the previous information not correct?
> Should we fix  the conductivity to -750*0.7 or to 750*0.7 ?
>
> Concerning the boundary conditions we are indeed using periodic boundary
> conditions.
> However, we are not interested in the
> constant temperature case. We were using it for testing (since we
> errouneously thought it
> was easier). In the end we will impose
> the heat flux.
>
> Thanks again
>
> Best Regards,
> Alex
>
> 2013/2/13 <nek5000-users at lists.mcs.anl.gov>
>
>>
>> Hi Alex,
>>
>> I see you have ifadv set to T, which is correct.
>>
>> However, I also see that your conductivity is -.7, which
>> implies your Peclet number is 0.7 ---- (assuming your Reynolds number is
>> 750).  Is this what you want ?
>>
>> Also, are you using periodic boundary conditions?
>> If so, it takes a bit of care to get meaningful
>> forcing conditions, particularly for the fixed-temperature
>> boundary condition.  (This condition leads to determination
>> of an eigenvalue to find the fully-developed flow conditions,
>> which have a bulk temperature scaling like  exp(-lambda x).
>> I can point you to some techniques for developing such conditions if you'd
>> like.)
>>
>> Paul
>>
>>
>>
>>
>> On Wed, 13 Feb 2013, nek5000-users at lists.mcs.anl.**gov<nek5000-users at lists.mcs.anl.gov>wrote:
>>
>>  Dear all
>>>
>>> we are trying to make calculations of turbulent heat transfer in a
>>> pipe. Everything seems to work fine
>>> with the velocity field, however this is not the case for the
>>> temperature. It seems as if the convection
>>> for the temperature equation is switched off. So, we obtain a
>>> turbulent velocity distribution but a laminar temperature
>>> distribution.
>>>
>>> We have tried several thermal boundary condtions and at the moment we
>>> are just fixing the temperature at the wall
>>> T=0 and adding a heat source qvol=1. In the following we add details
>>> of the case.
>>>
>>> Thanks for your help
>>>
>>> Regards,
>>> Alex
>>>
>>> rea file
>>> ****** PARAMETERS *****
>>>   2.6099999      NEKTON VERSION
>>>   3 DIMENSIONAL RUN
>>>         103  PARAMETERS FOLLOW
>>>   1.00000     p001 DENSITY
>>>  -750.       p002 VISCOS
>>>   0.00000     p003
>>>   0.00000     p004
>>>   0.00000     p005
>>>   0.00000     p006
>>>   1.00000     p007 RHOCP
>>>  -0.7         p008 CONDUCT
>>> [...]
>>>          13   LOGICAL SWITCHES FOLLOW
>>> T      IFFLOW
>>> T      IFHEAT
>>> T      IFTRAN
>>> T T F F F F F F F F F IFNAV & IFADVC (convection in P.S. fields)
>>> F F T T T T T T T T T T  IFTMSH (IF mesh for this field is T mesh)
>>> F      IFAXIS
>>> F      IFSTRS
>>> F      IFSPLIT
>>> F      IFMGRID
>>> F      IFMODEL
>>> F      IFKEPS
>>> F      IFMVBD
>>> F      IFCHAR
>>> [...]
>>>
>>> usr file
>>> [...]
>>> c-----------------------------
>>> ------------------------------**------------
>>>      subroutine userf  (ix,iy,iz,ieg)
>>>      include 'SIZE'
>>>      include 'TOTAL'
>>>      include 'NEKUSE'
>>>
>>>      ffx = 0.0
>>>      ffy = 0.0
>>>      ffz = 2.0
>>>
>>>      return
>>>      end
>>> c-----------------------------**------------------------------**
>>> ------------
>>>      subroutine userq  (ix,iy,iz,ieg)
>>>      include 'SIZE'
>>>      include 'TOTAL'
>>>      include 'NEKUSE'
>>>
>>>      qvol   = 1.0
>>>      source = 0.0
>>>
>>>      return
>>>      end
>>> c-----------------------------**------------------------------**
>>> ------------
>>> [...]
>>>
>>>  ______________________________**_________________
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