[Nek5000-users] turbulent heat transfer

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

PS - sorry - I forgot to answer your question about
how to set p8.

I guess I would set p2=-750 and p8 = -(750*0.7)



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

>
>
> 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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>>> 
>> 
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