[Nek5000-users] turbulent channel flow

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

Hi Alex,

You could do like this:

      subroutine userf  (ix,iy,iz,ieg)
      include 'SIZE'
      include 'TOTAL'
      include 'NEKUSE'

      real retau
c
      visc=param(2) 
c
      retau = 180
      ffx = (retau*visc)**2
      ffz = 0.0
      ffy = 0.0
      return
      end

/Johan
nek5000-users at lists.mcs.anl.gov wrote:
> Hi,
>
> I am trying to reproduce the results for the turbulent channel flow
> using DNS.
>
> However, instead of using the bulk velocity or the flow rate to drive
> the flow, I would like to use a mean pressure gradient.
>
> Using the non-dimensional equations resulting from selecting the
> friction velocity (u_tau) as the velocity scale, only the Reynolds
> number based on u_tau needs to be specified because the mean pressure
> gradient is equal to -1.
> Consequently the pressure gradient in the streamwise direction is grad
> p=-1+grad p* where * means fluctuation.
>
> I assumed that this could be done by simply setting:
> ffx=1.0
> ffy=0.0
> ffz=0.0
> in subroutine userf.
>
> All my trials initializing the flow with some kind of synthetic
> turbulent flow ended up damping the fluctuation and converging towards
> the laminar solution.
>
> Any help?.
>
>   


-- 
Johan Malm
Department of Mechanics, KTH
SE-100 44, Stockholm, Sweden
Phone: +46 8 7906876
E-mail: johan at mech.kth.se