2d/bc/bcout2.f

!-----------------------------------------------------------------------
! Physical boundary conditions for 2d equations.
! Zero order outflow at all sides.
! Interface:
!   mx,my    := shape of grid function
!
!   u(,) := grid function
!
!   lb(2) := lower bound for grid
!   ub(2) := upper bound for grid
!   lbbnd(2) := lower bound for boundary region
!   ubnd(2) := upper bound for boundary region
!   shapebnd(2) := shape of boundary region 
!   xc(2) := lower left corner of grid
!   dx(2) := grid spacing
!   dir := at which side of the grid is the boundary?
!   bnd(,2,2) := lower left and upper right corner of global grid and 
!      of mb-1 internal boundary regions
! 
! A general implementation of boundary conditions is required, because
! - a boundary region can have a width of 1 or 2 ghost cells. 
! - corners of a grid might be part of two boundaries and it is NOT 
!   guaranteed that ALL cells of a particular corner region are
!   contained in both boundaries. 
!-----------------------------------------------------------------------

      subroutine physbd(u,mx,my,lb,ub,lbbnd,ubbnd,shapebnd,
     &     xc,dx,dir,bnd,mb,time,args,argc)

      implicit none

      integer   argc, args, mx, my, mb, dir
      integer   lb(2), ub(2), lbbnd(2), ubbnd(2), shapebnd(2)
      real*8    u(args, mx, my), xc(2), dx(2), bnd(mb,2,2), time

!      Local variables
      integer   i, j, imin, imax, jmin, jmax, m
      integer   stride, meqn, getindx

      meqn = args

!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
!      See definition of member-function extents() in BBox.h 
!      for calculation of stride
         
      stride = (ub(1) - lb(1))/(mx-1)
               
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
!     Find working domain
         
      imin = getindx(max(lbbnd(1), lb(1)), lb(1), stride)
      imax = getindx(min(ubbnd(1), ub(1)), lb(1), stride)
      
      jmin = getindx(max(lbbnd(2), lb(2)), lb(2), stride)
      jmax = getindx(min(ubbnd(2), ub(2)), lb(2), stride)
         
      go to (100,200,300,400) dir+1

!        Left Side --- Outflow
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 100  continue
      do 110 i = imax, imin, -1
         if (xc(1)+(i-0.5d0)*dx(1).lt.bnd(1,1,1)) then
            do 120 j = jmin, jmax
               do 120 m = 1, meqn
                  u(m,i,j) = u(m,i+1,j)
 120        continue
         endif
 110  continue
      return

!        Right Side --- Outflow
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 200  continue
      do 210 i = imin, imax
         if (xc(1)+(i-0.5d0)*dx(1).gt.bnd(1,2,1)) then
            do 220 j = jmin, jmax
               do 220 m = 1, meqn
                  u(m,i,j) = u(m,i-1,j)
 220        continue
         endif
 210  continue
      return
         
!        Bottom Side --- Outflow
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 300  continue
      do 310 j = jmax, jmin, -1
         if (xc(2)+(j-0.5d0)*dx(2).lt.bnd(1,1,2)) then
            do 320 i = imin, imax
               do 320 m = 1, meqn
                  u(m,i,j) = u(m,i,j+1)
 320        continue
         endif
 310  continue
      return

!        Top Side --- Outflow
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 400  continue
      do 410 j = jmin, jmax
         if (xc(2)+(j-0.5d0)*dx(2).gt.bnd(1,2,2)) then
            do 420 i = imin, imax
               do 420 m = 1, meqn
                  u(m,i,j) = u(m,i,j-1)
 420        continue
         endif
 410  continue
      return

      end