BCSponge.c File Reference

Sponge boundary condition. More...

#include <stdlib.h>
#include <basic.h>
#include <arrayfunctions.h>
#include <boundaryconditions.h>

Go to the source code of this file.

Functions
int	BCSpongeSource (void *b, int ndims, int nvars, int ghosts, int *size, double *grid, double *u, double *source)
int	BCSpongeUDummy (void *b, void *m, int ndims, int nvars, int *size, int ghosts, double *phi, double waqt)

Detailed Description

Sponge boundary condition.

Author

Debojyoti Ghosh

Definition in file BCSponge.c.

Function Documentation

BCSpongeSource()

int BCSpongeSource	(	void *	b,
		int	ndims,
		int	nvars,
		int	ghosts,
		int *	size,
		double *	grid,
		double *	u,
		double *	source
	)

Applies the sponge boundary condition: This function computes the source term required to apply a sponge boundary condition that gradually relaxes the solution to a specified state. This boundary condition is different from other boundary conditions in the sense that it is applied at interior grid points (but within the defined sponge zone).

The source term for the sponge is computed as:

\begin{align} {\bf S}_i &= \sigma_i \left( {\bf U}_i - {\bf U}_{\rm ref} \right),\\ \sigma_i &= \frac {x_i - x_{\rm start}} {x_{\rm end} - x_{\rm start}} \end{align}

where \(i\) is the grid index along the spatial dimension of the sponge, \({\bf U}_{\rm ref}\) is the specified state to which the solution is relaxed, and \(x_i\), \(x_{\rm start}\), and \(x_{\rm end}\) are the spatial coordinates of the grid point, sponge start, and sponge end, respectively, along the spatial dimension of the sponge.

Parameters

b	Boundary object of type DomainBoundary
ndims	Number of spatial dimensions
nvars	Number of variables/DoFs per grid point
ghosts	Number of ghost points
size	Integer array with the number of grid points in each spatial dimension
grid	1D array with the spatial coordinates of the grid points, one dimension after the other
u	Solution
source	Source term to which the sponge term is added

Definition at line 26 of file BCSponge.c.

{
  DomainBoundary *boundary = (DomainBoundary*) b;
  int            dim       = boundary->dim;
  int            face      = boundary->face;
  double         *uref     = boundary->SpongeValue;
  double         *xmin     = boundary->xmin;
  double         *xmax     = boundary->xmax;
  int            v;

  if (boundary->on_this_proc) {
    int bounds[ndims], indexb[ndims];
    _ArraySubtract1D_(bounds,boundary->ie,boundary->is,ndims);
    _ArraySetValue_(indexb,ndims,0); 
    int done = 0;
    while (!done) {
      int i = indexb[dim] + boundary->is[dim];
      double x, xstart, xend;
      _GetCoordinate_(dim,i,size,ghosts,grid,x);
      xstart = xmin[dim];
      xend   = xmax[dim];
      /* calculate sigma */
      double sigma;
      if (face > 0) sigma = (x - xstart) / (xend - xstart);
      else          sigma = (x - xend  ) / (xstart - xend);
      /* add to the source term */
      int p; _ArrayIndex1DWO_(ndims,size,indexb,boundary->is,ghosts,p);
      for (v=0; v<nvars; v++) source[nvars*p+v] -= (sigma * (u[nvars*p+v]-uref[v]));
      _ArrayIncrementIndex_(ndims,bounds,indexb,done);
    }
  }
  return(0);
}

BCSpongeUDummy()

int BCSpongeUDummy	(	void *	b,
		void *	m,
		int	ndims,
		int	nvars,
		int *	size,
		int	ghosts,
		double *	phi,
		double	waqt
	)

Dummy function to ensure consistency with the overall boundary condition implementation. The actual sponge boundary condition is implemented by BCSpongeSource()

Parameters

b	Boundary object of type DomainBoundary
m	MPI object of type MPIVariables
ndims	Number of spatial dimensions
nvars	Number of variables/DoFs per grid point
size	Integer array with the number of grid points in each spatial dimension
ghosts	Number of ghost points
phi	The solution array on which to apply the boundary condition
waqt	Current solution time

Definition at line 73 of file BCSponge.c.

{
  return(0);
}