[Nek5000-users] Temperature gradient at a point

nek5000-users at lists.mcs.anl.gov nek5000-users at lists.mcs.anl.gov
Thu Aug 26 15:30:06 CDT 2010


What's the error message you are getting? 

It may be the case, I know that I have had issues with settings and conj HT before since they are (mainly because of our group) revisiting CHT and fixing issues that we request. The latest issue, like I mentioned, was the new time stepping scheme and CHT. 

Did the error show up during compiling, or during the run in the output log? 

- Mike 

----- Original Message ----- 
From: nek5000-users at lists.mcs.anl.gov 
To: nek5000-users at lists.mcs.anl.gov 
Sent: Thursday, August 26, 2010 2:18:39 PM GMT -06:00 US/Canada Central 
Subject: Re: [Nek5000-users] Temperature gradient at a point 

Hi, 

Is there any reason why a conjucate heat transfer case should not work with IFLOMACH turned on? 
I did modify the uservp to set utrans = 1./temp. 

Thanks, 
Pradeep 

c----------------------------------------------------------------------- 
subroutine uservp (ix,iy,iz,ieg) 
include 'SIZE' 
include 'TOTAL' 
include 'NEKUSE' 

if (ifield.eq.1) then 
utrans = 1./temp 
c utrans = param(1) 
udiff = param(2) 

else 

utrans = 1./temp ! thermal properties 
c utrans = param(7) 
udiff = param(8) 

if (ieg .gt. nelgv) then ! properties in the solid 
udiff = 0.1*param(8) ! conductivity 
utrans = 1.0 
endif 

endif 

return 
end 
c----------------------------------------------------------------------- 


On Mon, Aug 23, 2010 at 4:40 PM, Pradeep Rao < stringsofdurga at gmail.com > wrote: 


Thanks Aleks, 

Will give that a try. 





On Mon, Aug 23, 2010 at 4:25 PM, < nek5000-users at lists.mcs.anl.gov > wrote: 


Hi Pradeep, 

Dependence of conductivity on time and space is not a problem once one uses non zero p30 in .rea that activates a call to uservp of .usr file 

If you also need a dependence of conductivity on temperature you may want to consider either using the values from the previous time step or doing extrapolation in time. 

Best, 
Aleks 





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



Hi Paul, 

Thanks for the detailed reply. The reason I'm not solving it as a conjugate 
heat transfer problem, is that thermal conductivity is a function of 
temperature based on some curve fit equations, and I am not sure how to 
implement that. 

Thanks, 
Pradeep 

On Mon, Aug 23, 2010 at 4:04 PM, < nek5000-users at lists.mcs.anl.gov > wrote: 




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 

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-- 
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 

uuuu 
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----------------------------------------------------------------------- 

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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 

_______________________________________________ 
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 



-- 
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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