[Nek5000-users] LES and heat transfer in channel

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

Hi,

I am running a channel LES simulation (periodic in streamwise and 
spanwise, length=width=9*channel height) in nek with the following 
parameters:
-LES model: Filter last 3 modes, 5% filter weight; lx1=14; ld1=20
-Piece of the rea file
"
    1.00000         DENSITY
    0.31250E-04     VISCOS
    1.00000         RHOCP
    1.00000         CONDUCT
    4.00000           p99=3 ==> dealiasing turned on
  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
  T      IFCHAR
"
-Reynolds number based on 2*channel height: 12800
-Constant heat flux on walls
-The streamwise boundary is a recycling one, I set it up similar to the 
turbJet example, but I added temperature recycling. To avoid 
"over-heating", I subtract the added thermal energy from the temperature 
when recycling
-Some material parameters are set in the .usr file:
"
param(8)   = param(2)/0.71 ! Prandt=0.71
cpfld(2,1) = param(8)      ! conductivity
"

When I compare the spanwise averaged and time averaged Nusselt number on 
a wall, it is fairly constant with streamwise direction (which is good), 
but about 50% higher then the experimental one from the correlation
Nu=0.022*Re^0.8*Pr^0.5
This might be because I am only 2.5 flow throughs away from the initial 
  condition, but I wanted to make sure that everything is right before 
putting in more computing hours.
Does the above look OK? Is there another explanation for the heat 
transfer coefficient being too high?

Thanks,
Markus