fd2d_prb.f90

是一个接收永磁体磁场计算的程序

subroutine u_init ( alpha, beta, gamma, delta, m, n, x, y, u0 )

!*****************************************************************************80
!
!! U_INIT supplies the initial value of U at each node.
!
!  Modified:
!
!    01 August 2004
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, real ( kind = 8 ) ALPHA, BETA, GAMMA, DELTA, the parameters.
!
!    Input, integer M, N, the number of rows and columns.
!
!    Input, real ( kind = 8 ) X(M,N), Y(M,N), the X and Y coordinates
!    of the nodes.
!
!    Output, real ( kind = 8 ) U0(M,N), the initial value of U at the nodes.
!
  implicit none

  integer m
  integer n

  real ( kind = 8 ) alpha
  real ( kind = 8 ) beta
  real ( kind = 8 ) delta
  real ( kind = 8 ) gamma
  real ( kind = 8 ) u0(m,n)
  real ( kind = 8 ) ustar
  real ( kind = 8 ) x(m,n)
  real ( kind = 8 ) y(m,n)

  ustar = gamma * alpha / ( beta - gamma )

  u0(1:m,1:n) = ustar - 2.0D-07 &
    * ( x(1:m,1:n) - 0.1D+00 * y(1:m,1:n) - 225.0D+00 ) &
    * ( x(1:m,1:n) - 0.1D+00 * y(1:m,1:n) - 675.0D+00 )

  return
end
subroutine v_init ( alpha, beta, gamma, delta, m, n, x, y, v0 )

!*****************************************************************************80
!
!! V_INIT supplies the initial value of U at each node.
!
!  Modified:
!
!    30 November 2004
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, real ( kind = 8 ) ALPHA, BETA, GAMMA, DELTA, the parameters.
!
!    Input, integer M, N, the number of rows and columns.
!
!    Input, real ( kind = 8 ) X(M,N), Y(M,N), the X and Y coordinates
!    of the nodes.
!
!    Output, real ( kind = 8 ) V0(M,N), the initial value of U at the nodes.
!
  implicit none

  integer m
  integer n

  real ( kind = 8 ) alpha
  real ( kind = 8 ) beta
  real ( kind = 8 ) delta
  real ( kind = 8 ) gamma
  real ( kind = 8 ) ustar
  real ( kind = 8 ) v0(m,n)
  real ( kind = 8 ) vstar
  real ( kind = 8 ) x(m,n)
  real ( kind = 8 ) y(m,n)

  ustar = gamma * alpha / ( beta - gamma )
  vstar = ( 1.0D+00 - ustar ) * ( alpha + ustar )

  v0(1:m,1:n) = vstar - 3.0D-05 * ( x(1:m,1:n) - 450.0D+00 ) &
    - 1.2D-04 * ( y(1:m,1:n) - 150.0D+00 )

  return
end

subroutine timestamp ( )

!*****************************************************************************80
!
!! TIMESTAMP prints the current YMDHMS date as a time stamp.
!
!  Example:
!
!    May 31 2001   9:45:54.872 AM
!
!  Modified:
!
!    15 March 2003
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    None
!
  implicit none

  character ( len = 40 ) string

  call timestring ( string )

  write ( *, '(a)' ) trim ( string )

  return
end


subroutine timestring ( string )

!*****************************************************************************80
!
!! TIMESTRING writes the current YMDHMS date into a string.
!
!  Example:
!
!    STRING = 'May 31 2001   9:45:54.872 AM'
!
!  Modified:
!
!    15 March 2003
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Output, character ( len = * ) STRING, contains the date information.
!    A character length of 40 should always be sufficient.
!
  implicit none

  character ( len = 8 ) ampm
  integer d
  character ( len = 8 ) date
  integer h
  integer m
  integer mm
  character ( len = 9 ), parameter, dimension(12) :: month = (/ &
    'January  ', 'February ', 'March    ', 'April    ', &
    'May      ', 'June     ', 'July     ', 'August   ', &
    'September', 'October  ', 'November ', 'December ' /)
  integer n
  integer s
  character ( len = * ) string
  character ( len = 10 ) time
  integer values(8)
  integer y
  character ( len = 5 ) zone

  call date_and_time ( date, time, zone, values )

  y = values(1)
  m = values(2)
  d = values(3)
  h = values(5)
  n = values(6)
  s = values(7)
  mm = values(8)

  if ( h < 12 ) then
    ampm = 'AM'
  else if ( h == 12 ) then
    if ( n == 0 .and. s == 0 ) then
      ampm = 'Noon'
    else
      ampm = 'PM'
    end if
  else
    h = h - 12
    if ( h < 12 ) then
      ampm = 'PM'
    else if ( h == 12 ) then
      if ( n == 0 .and. s == 0 ) then
        ampm = 'Midnight'
      else
        ampm = 'AM'
      end if
    end if
  end if

  write ( string, '(a,1x,i2,1x,i4,2x,i2,a1,i2.2,a1,i2.2,a1,i3.3,1x,a)' ) &
    trim ( month(m) ), d, y, h, ':', n, ':', s, '.', mm, trim ( ampm )

  return
end