[Nek5000-users] Сollocation of i,j,k in each spectral element

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

Hi Elizabeth,


Correct - there is no guarantee that the elements are generated

with any particular orientation (except if you use genbox).


You have access to all the variables in the code.  Typically, usrdat2() or

userchk() are good places to query.


Use usrdat2() if you want to set things up prior to the start of the computation. Use userchk() if you want to set things up during or just at the very start of the computation.


A common usage mode:


subroutine userchk()

...

if (istep.eq.0) then

    check whatever...

endif


The advantage of checking in userchk() on step 0 is that all of the preliminary variables (including initial conditions) are set and ready to go.


The advantage of using usrdat2() is that the geometry is ready (i.e., xm1, ym1, zm1), but the geometric factors are recomputed after usrdat2 is called, so that you can _morph_ the geometry (i.e., make a smooth and _continuous_ transformation).   You cannot, say, rotate individual elements in usrdat2() because that would result in a topological change in the mesh connectivity and at present Nek5000 does not have a mechanism to discover that change.  (Connectivity is established by genmap.)


hth,


Paul


________________________________
From: Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on behalf of nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
Sent: Tuesday, November 21, 2017 9:11:48 PM
To: nek5000-users
Subject: [Nek5000-users] Сollocation of i,j,k in each spectral element



Hi, Neks!

I am working with a complex geometry witch was built in gambit.And I want to change positions of some points in spectral elements. I've read in documentation that i,j,k,e in xm1(i,j,k,e), for example, are changed from 1 to nx1,ny1,nz1 and nelv respectively. But during my tests it's seemed that in different elements x,y,z axis not always correspond to the global coordinate system. Am I right?

And how could  I find out the principle of collocation of i,j,k in each spectral element?

Best regards,
Elizabeth
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