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viscosity_kernel.f90
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viscosity_kernel.f90
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!Crown Copyright 2012 AWE.
!
! This file is part of CloverLeaf.
!
! CloverLeaf is free software: you can redistribute it and/or modify it under
! the terms of the GNU General Public License as published by the
! Free Software Foundation, either version 3 of the License, or (at your option)
! any later version.
!
! CloverLeaf is distributed in the hope that it will be useful, but
! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
! FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
! details.
!
! You should have received a copy of the GNU General Public License along with
! CloverLeaf. If not, see http://www.gnu.org/licenses/.
!> @brief Fortran viscosity kernel.
!> @author Wayne Gaudin
!> @details Calculates an artificial viscosity using the Wilkin's method to
!> smooth out shock front and prevent oscillations around discontinuities.
!> Only cells in compression will have a non-zero value.
MODULE viscosity_kernel_module
CONTAINS
SUBROUTINE viscosity_kernel(x_min,x_max,y_min,y_max, &
celldx,celldy, &
density0, &
pressure, &
viscosity, &
xvel0, &
yvel0 )
IMPLICIT NONE
INTEGER :: x_min,x_max,y_min,y_max
REAL(KIND=8), DIMENSION(x_min-2:x_max+2) :: celldx
REAL(KIND=8), DIMENSION(y_min-2:y_max+2) :: celldy
REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: density0
REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: pressure
REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: viscosity
REAL(KIND=8), DIMENSION(x_min-2:x_max+3,y_min-2:y_max+3) :: xvel0,yvel0
INTEGER :: j,k
REAL(KIND=8) :: ugrad,vgrad,grad2,pgradx,pgrady,pgradx2,pgrady2,grad &
,ygrad,pgrad,xgrad,div,strain2,limiter,dirx,diry
!$ACC DATA &
!$ACC PRESENT(density0,pressure,viscosity,xvel0,yvel0)
!$ACC KERNELS
!$ACC LOOP INDEPENDENT
DO k=y_min,y_max
!$ACC LOOP INDEPENDENT PRIVATE(ugrad,vgrad,div,strain2,pgradx,pgrady,pgradx2,pgrady2,limiter,pgrad,xgrad,ygrad,grad,grad2,dirx,diry)
DO j=x_min,x_max
ugrad=(xvel0(j+1,k )+xvel0(j+1,k+1))-(xvel0(j ,k )+xvel0(j ,k+1))
vgrad=(yvel0(j ,k+1)+yvel0(j+1,k+1))-(yvel0(j ,k )+yvel0(j+1,k ))
div = (celldx(j)*(ugrad)+ celldy(k)*(vgrad))
strain2 = 0.5_8*(xvel0(j, k+1) + xvel0(j+1,k+1)-xvel0(j ,k )-xvel0(j+1,k ))/celldy(k) &
+ 0.5_8*(yvel0(j+1,k ) + yvel0(j+1,k+1)-yvel0(j ,k )-yvel0(j ,k+1))/celldx(j)
pgradx=(pressure(j+1,k)-pressure(j-1,k))/(celldx(j)+celldx(j+1))
pgrady=(pressure(j,k+1)-pressure(j,k-1))/(celldy(k)+celldy(k+1))
pgradx2 = pgradx*pgradx
pgrady2 = pgrady*pgrady
limiter = ((0.5_8*(ugrad)/celldx(j))*pgradx2+(0.5_8*(vgrad)/celldy(k))*pgrady2+strain2*pgradx*pgrady) &
/MAX(pgradx2+pgrady2,1.0e-16_8)
IF ((limiter.GT.0.0).OR.(div.GE.0.0))THEN
viscosity(j,k) = 0.0
ELSE
dirx=1.0_8
IF(pgradx.LT.0.0) dirx=-1.0_8
pgradx = dirx*MAX(1.0e-16_8,ABS(pgradx))
diry=1.0_8
IF(pgradx.LT.0.0) diry=-1.0_8
pgrady = diry*MAX(1.0e-16_8,ABS(pgrady))
pgrad = SQRT(pgradx**2+pgrady**2)
xgrad = ABS(celldx(j)*pgrad/pgradx)
ygrad = ABS(celldy(k)*pgrad/pgrady)
grad = MIN(xgrad,ygrad)
grad2 = grad*grad
viscosity(j,k)=2.0_8*density0(j,k)*grad2*limiter*limiter
ENDIF
ENDDO
ENDDO
!$ACC END KERNELS
!$ACC END DATA
END SUBROUTINE viscosity_kernel
END MODULE viscosity_kernel_module