[Nek5000-users] mapping straight pipe to curved pipe

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

Hello,

I am trying to change the usrdat2 in example pipe(helix) to make curved
pipe with defined curvature. I changed the .usr file like this:

subroutine usrdat2
      include 'SIZE'
      include 'TOTAL'
      common /ogeom/ ox(lx1,ly1,lz1,lelv)
     $             , oy(lx1,ly1,lz1,lelv)
     $             , oz(lx1,ly1,lz1,lelv)

      diam  = 1.0
      one  = 1.
      pi   = 4.*atan(one)

      Rcurv = 3   !curvature of the pipe

      z0 = 0.
      z1 = pi*Rcurv  !equal to area of the curved pipe
      call rescale_x (zm1,z0,z1)

      rad  = diam/2.
      radm = -rad
      call rescale_x (xm1,radm,rad)
      call rescale_x (ym1,radm,rad)

      n = nx1*ny1*nz1*nelv
      call copy(ox,xm1,n)
      call copy(oy,ym1,n)
      call copy(oz,zm1,n)

      do i=1,n                  ! preset offset twist
         x  = xm1(i,1,1,1)
         y  = ym1(i,1,1,1)
         z  = zm1(i,1,1,1)
         theta = z/Rcurv
         zm1 = Rcurv*sin(theta)
         ym1(i,1,1,1) = y + Rcurv*cos(theta)
      enddo


      param(59) = 1.   !  All elements deformed
      ifxyo     = .true.

      return
      end
c-----------------------------------------------------------------------

but it comes out with some error associated with vanishing jacobian! I
would ask that what is the problem with my modification on mapping straight
pipe?

Thanks,
Ami
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