[Nek5000-users] Questions in AXHELM and WLAPLACIAN

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

Dear nek5000 team,

Could you help me with the 2 questions below? Thank you very much !

1)
Concerning the routine “axhelm” in hmholtz.f. If I am right, one possibility of this routine can be the discretisation of the diffusion operator. However it is not clear to me if axhelm performs:

a) vdiff  x   Laplacian(phi)

or

b) grad ( vdiff x grad (phi) )

phi being the variable solved for (T or PS for example).

So, is it actually a) or b) ?


2)
In the routine wlaplacian in navier1.f, I am not sure to understand the consequence of the line:

call sub2 (out,wrk,ntot)

after the lines:

call bcneusc(out,1)
call axhelm(wrk,a,diff,h2,imesh,1)

If I am right, this will change the sign in front of the diffusion operator, right?
Because in makeq.f, I am not sure that the line
call add2(bq(1,1,1,1,ifield-1),w1,ntot)

will actually assemble the RHS of the transport equation :  - (vtrans) x  U grad (phi)  +  grad ( vdiff x grad (phi) )


Thank you for your help !

Best regards,
Emmanuel



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