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gyacomo/src/geometry_mod.F90
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geometry_mod.F90
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module geometry
! computes geometrical quantities
! Adapted from B.J.Frei MOLIX code (2021)
use prec_const
use model
use grid
use array
use fields
use basic
implicit none
public
contains
subroutine eval_magnetic_geometry
! evalute metrix, elements, jacobian and gradient
implicit none
!
IF( my_id .eq. 0 ) WRITE(*,*) 's-alpha geometry'
! circular model
call eval_s_alpha_geometry
!
END SUBROUTINE eval_magnetic_geometry
!
!--------------------------------------------------------------------------------
!
subroutine eval_s_alpha_geometry
! evaluate circular geometry model
! Ref: Lapilonne et al., PoP, 2009
implicit none
REAL(dp) :: z, kx, ky
zloop: DO iz = izs,ize
z = zarray(iz)
! Metric elements
gxx(iz) = 1._dp
gxy(iz) = shear*z -eps*SIN(z)
gyy(iz) = 1._dp +(shear*z)**2 -2._dp*eps*COS(z) -2._dp*shear*eps*z*SIN(z)
! Relative strengh of radius
hatR(iz) = 1._dp + eps*cos(z)
hatB(iz) = SQRT(gxx(iz)*gyy(iz) - gxy(iz)**2)
! Jacobian
Jacobian(iz) = q0*hatR(iz)**2
! Derivative of the magnetic field strenght
gradxB(iz) = -(COS(z) + eps*SIN(z)**2)/hatB(iz)/hatB(iz)
gradzB(iz) = eps*SIN(z)
! coefficient in the front of parallel derivative
gradz_coeff(iz) = 1._dp / Jacobian(iz) / hatB(iz)
! Curvature operator
DO iky = ikys, ikye
ky = kyarray(iky)
DO ikx= ikxs, ikxe
kx = kxarray(ikx)
Ckxky(ikx,iky,iz) = -SIN(z)*kx -(COS(z)+shear*z*SIN(z))*ky
ENDDO
ENDDO
IF (Nky .EQ. 1) THEN ! linear 1D run we switch kx and ky for parallel opt
DO iky = ikys, ikye
ky = kyarray(iky)
DO ikx= ikxs, ikxe
kx = kxarray(ikx)
Ckxky(ikx,iky,iz) = -SIN(z)*ky -(COS(z)+shear*z*SIN(z))*kx
ENDDO
ENDDO
ENDIF
ENDDO zloop
END SUBROUTINE eval_s_alpha_geometry
end module geometry
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