[Nek5000-users] Temperature gradient at a point

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

Hi Pradeep,

Why not just solve the conjugate heat transfer problem directly
using fluid + solid elements in nek?

Also, nek supports full Robin boundary conditions if you wish
to do a Newton law of cooling:  k*dT/dn . n_hat = h*(T-Tinf), where 
Tinf is the external temperature and h is the heat transfer 
coefficient, both of which can be functions of time and space.


Regarding gradm1, you would call it from userchk, and store
the output in arrays in a common block, e.g., as below.

Paul

       subroutine userchk
       :
       common /mygrad/ tx(lx1,ly1,lz1,lelt)
      $              , ty(lx1,ly1,lz1,lelt)
      $              , tz(lx1,ly1,lz1,lelt)

       call gradm1(tx,ty,tz,t)

       :
       :

       subroutine userbc (ix,iy,iz,iside,eg)
       include 'SIZE'
       include 'TOTAL'
       include 'NEKUSE'

       common /mygrad/ tx(lx1,ly1,lz1,lelt)
      $              , ty(lx1,ly1,lz1,lelt)
      $              , tz(lx1,ly1,lz1,lelt)

       integer e,eg

       e = gllel(eg) ! global element number to processor-local el. #

       gtx=tx(ix,iy,iz,e)
       gty=ty(ix,iy,iz,e)
       gtz=tz(ix,iy,iz,e)



On Mon, 23 Aug 2010, nek5000-users at lists.mcs.anl.gov wrote:

> Hi Paul,
>
> I am basically trying to solve a conjugate heat transfer problem in an
> iterative manner, for flow over an infinitely long cylinder (2D).
>
> I need to use the heat transfer at the boundary, to calculate the new
> temperature at the boundary for the next time step. The
> temperature for the next time step is solved for using this heat flux, by a
> function in the usr file using an FEM algorithm for the solid part
> (cylinder). The bc type I am using is Temperature - fortran function.
>
> Regards,
> Pradeep
>
> On Mon, Aug 23, 2010 at 2:50 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
>
>>
>> Pradeep,
>>
>> if you give me some idea of the nature of your bc, I can
>> perhaps help --- there are a large number of bc types already
>> supported inside nek
>>
>> Paul
>>
>>
>>
>> On Mon, 23 Aug 2010, nek5000-users at lists.mcs.anl.gov wrote:
>>
>>  Hi,
>>>
>>> I wanted to know if there was a way to find the temperature gradient at a
>>> point. I need that information in the userbc function.
>>>
>>> I tried using gradm1(), but I am not sure how to get the value at a given
>>> point.
>>>
>>> Thanks,
>>> Pradeep
>>>
>>>  _______________________________________________
>> Nek5000-users mailing list
>> Nek5000-users at lists.mcs.anl.gov
>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>>
>
>
>
> -- 
> Pradeep C. Rao
> Graduate Research Assistant for FT2L (http://www1.mengr.tamu.edu/FT2L/)
> Department of Mechanical Engineering
> Texas A&M University
> College Station, TX 77843-3123
>
> 428 Engineering Physics Building
> (713) 210-9769
>
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c-----------------------------------------------------------------------
C
C  USER SPECIFIED ROUTINES:
C
C     - boundary conditions
C     - initial conditions
C     - variable properties
C     - local acceleration for fluid (a)
C     - forcing function for passive scalar (q)
C     - general purpose routine for checking errors etc.
C
c-----------------------------------------------------------------------
       subroutine uservp (ix,iy,iz,eg)
       include 'SIZE'
       include 'TOTAL'
       include 'NEKUSE'

       integer e,f,eg
c     e = gllel(eg)

       udiff =0.
       utrans=0.
       return
       end
c-----------------------------------------------------------------------
       subroutine userf  (ix,iy,iz,eg)
       include 'SIZE'
       include 'TOTAL'
       include 'NEKUSE'

       integer e,f,eg
c     e = gllel(eg)


c     Note: this is an acceleration term, NOT a force!
c     Thus, ffx will subsequently be multiplied by rho(x,t).


       ffx = 0.0
       ffy = 0.0
       ffz = 0.0

       return
       end
c-----------------------------------------------------------------------
       subroutine userq  (ix,iy,iz,eg)
       include 'SIZE'
       include 'TOTAL'
       include 'NEKUSE'

       integer e,f,eg
c     e = gllel(eg)

       qvol   = 0.0

       return
       end
c-----------------------------------------------------------------------
       subroutine userchk
       include 'SIZE'
       include 'TOTAL'
       return
       end
c-----------------------------------------------------------------------
       subroutine userbc (ix,iy,iz,iside,ieg)
       include 'SIZE'
       include 'TOTAL'
       include 'NEKUSE'
       ux=0.0
       uy=0.0
       uz=0.0
       temp=0.0
       return
       end
c-----------------------------------------------------------------------
       subroutine useric (ix,iy,iz,ieg)
       include 'SIZE'
       include 'TOTAL'
       include 'NEKUSE'
       ux=0.0
       uy=0.0
       uz=0.0
       temp=0
       return
       end
c-----------------------------------------------------------------------
       subroutine usrdat
       include 'SIZE'
       include 'TOTAL'
c
       return
       end
c-----------------------------------------------------------------------
       subroutine usrdat2
       include 'SIZE'
       include 'TOTAL'

       param(66) = 4.   ! These give the std nek binary i/o and are
       param(67) = 4.   ! good default values

       return
       end
c-----------------------------------------------------------------------
       subroutine usrdat3
       include 'SIZE'
       include 'TOTAL'
c
       return
       end
c-----------------------------------------------------------------------