[Nek5000-users] turbulent heat transfer

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

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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