[Nek5000-users] heat transfer in a channel

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

Zhicheng,

We've run under these conditions on a regular basis with this
technique.

Because temperature is determined only up to a constant there
is no apriori reason to anticipate T > 0 everywhere.

In general, for uniform heat flux boundary conditions, one writes

     T(X,t) = T'(X,t) + gamma x  +  C

with X=(x,y,z) and T'(X,t) = T'(X+L,t) being the periodic
part computed by nek.  Here, C is an arbitrary constant and gamma
is a constant determined by the mean temperature rise in the
system.  Gamma (in your case, gamma==1) should be chosen to 
balance the thermal enegy input at the boundaries with the flux 
advected by the mean flow.

Note that if constant temperature bcs (as opposed to const. flux) 
are a bit trickier as that effectively amounts to solving an 
eigenvalue problem.  (See, e.g.,

    M. Greiner, G. Spencer, and P. Fischer, "Direct numerical simulation
    of three-dimensional flow and augmented heat transfer in a grooved
    channel" ASME J. of Heat Transfer 120 3 pp.  717-723 (1998).

).

Paul



On Fri, 17 Sep 2010, nek5000-users at lists.mcs.anl.gov wrote:

>  Hi,
>
> I'm running a DNS of fully developed heat transfer in a channel, the same as
> H. Kawamura et. al, International Journal of Heat and Fluid Flow, 1998.
>
> I use following subroutine to get rid of additional heat
>
> c-----------------------------------------------------------------------
>      subroutine userq  (ix,iy,iz,ieg)
>      include 'SIZE'
>      include 'TOTAL'
>      include 'NEKUSE'
>      ie   = gllel(ieg)
>      qvol = -vx(ix,iy,iz,ie)
>      source = 0.0
>
>      return
>      end
> c-----------------------------------------------------------------------
>
> Other procedures are similar to turbChannel example.
>
> But I find the mean temperature is not correct,  there should not be
> negative  value in my case.
>
> I attached my *.usr and *.rea and means.dat to this email.
>
> is there any one  else did DNS of heat transfer in a channel ?
>
>
> Thank you very much
>
>
> zhicheng
>