[Nek5000-users] Smoothness of the derivatives

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

This is correct, derivatives in SEM are not C0. Your code forces the field to be C0 but it does not make it smooth across elements. Typically filtering doesn’t help. Why do you want a smooth derivative field?


> On 25 Jun 2018, at 12:55, "nek5000-users at lists.mcs.anl.gov" <nek5000-users at lists.mcs.anl.gov> wrote:
> 
> Hi, Neks!
> 
> 1) I am doing a DNS study of turbulent pipe jets and looking at turbulent kinetic energy budgets. 
> 
> I take derivatives via gradm1 subroutine, for example:
> 
> call gradm1(uxdx,uxdy,uxdz,ux)
> 
> After all, if I look at my dissipation field (via outpost), I see some wrong values on the surface between spectral elements. 
> I want to filter them using:
> 
> call col2(uxdx,bm1,ntot) 
> call dssum(uxdx,lx1,ly1,lz1) 
> call col2(uxdx,binvm1,ntot)
> 
> call dsavg(dxux)
> 
> for every array. But conversely it leads to an increase in gaps. What am I doing wrong?
> 
> 2) How does a filter-function in dssum look and how much points does it use for filtering? 
> 
> Best regards,
> Vlad.
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