Index

NAME

GridLatticeC  -  staggered  C-grid for finite difference computa­
tions

INCLUDE

include "GridLatticeC.h"

SYNTAX

 class GridLatticeC : public GridLattice
 {
 private:

 protected:

 public:
   GridLatticeC (int nsd =1, bool scalar_in_half_index=true);
   GridLatticeC (int nsd, bool scalar_in_half_index,
                 Ptv(int) half_shift_in_min, Ptv(int) half_shift_in_max);
  ~GridLatticeC ();

   void changeGridSize();

   void setIndexBase();

   void indexCheckOk(real i) const;
   void indexCheckOk(real i, real j) const;
   void indexCheckOk(real i, real j, real k) const;

   void computeCgrid(const GridLattice& grid,
                     const GridLattice:: Component);


   CLASS_INFO

   VIRTUAL_CAST(GridLatticeC)

 };

KEYWORDS

finite difference, staggered grid

DESCRIPTION

GridLatticeC enables the programmer to construct a  staggered  C-
grid  which  is  automatically  copied and redimensioned into the
right size when the grid is bound to a FieldLattice object  which
represents the different components in the calculations.

CONSTRUCTORS AND INITIALIZATION

There  are  two constructors with two and three arguments respec­
tively.  The scalar_in_half_index argument is true if the  scalar
is  located  at  the  centroid  of the cell (placing the velocity
points at the vertices of the cells), and false in  the  opposite
case. This variable will not be set by any other functions, hence
if it is to be different than the default value true, it must  be
set  at construction time. The half_shift_in_max argument is used
to cut off half a grid cell at the upper part of the  grid.  This
is  typically  used  if one has a velocity component given at one
boundary and the scalar value given at the  other  boundary.  The
variable is a Ptv(int) and has, in each direction, the value 1 if
a half shift is to occur, and 0 if the grid is to be left  as  it
is.

MEMBER FUNCTIONS

changeGridSize  and setIndexBase is called by FieldLattices real­
locate function as soon as the FieldLattice object is constructed
and  the  field  has got information on which component it repre­
sents in the staggered grid.

changeGridSize alters a copy of the grid to  make  it  the  right
size for the field it represents.

setIndexBase sets the variable index_base to the appropriate val­
ues determined by which component it represents in the  staggered
grid.

computeCgrid  -  alters  a  copy of the supplied grid to hold the
appropriate size for the given component in a C-grid. This change
is normally done by the FieldLattice constructor at the same time
as the required array for holding the values is created, hence in
ordinary  sequencial  programming  this  function  should  not be
called explicitely by the user. In parallel programming  however,
one  wishes to create the grid in the right size first, then dis­
tribute it on the available  processors  before  the  appropriate
array is allocated.

SEE ALSO

class FieldLattice, class GridLattice

DEVELOPED BY

SINTEF Applied Mathematics, Oslo, Norway, and University of Oslo,
Dept. of Mathematics, Norway

AUTHOR

Elizabeth Acklam, UiO