ShallowWater1DJacobian.c File Reference

Contains the functions compute flux Jacobians for the 1D shallow water system. More...

#include <mathfunctions.h>
#include <matmult_native.h>
#include <physicalmodels/shallowwater1d.h>

Go to the source code of this file.

Functions
int	ShallowWater1DJacobian (double *Jac, double *u, void *p, int dir, int nvars, int upw)

Detailed Description

Contains the functions compute flux Jacobians for the 1D shallow water system.

Author

Debojyoti Ghosh

Definition in file ShallowWater1DJacobian.c.

Function Documentation

int ShallowWater1DJacobian	(	double *	Jac,
		double *	u,
		void *	p,
		int	dir,
		int	nvars,
		int	upw
	)

Function to compute the flux Jacobian of the 1D shallow water equations, given the solution at a grid point. The Jacobian is square matrix of size nvar=2, and is returned as a 1D array (double) of 4 elements in row-major format.

Parameters

Jac	Jacobian matrix: 1D array of size nvar^2 = 4
u	solution at a grid point (array of size nvar = 2)
p	object containing the physics-related parameters
dir	dimension (x/y/z) (not used, since this is 1D system)
nvars	number of vector components
upw	0 -> send back complete Jacobian, 1 -> send back Jacobian of right(+)-moving flux, -1 -> send back Jacobian of left(-)-moving flux

Definition at line 14 of file ShallowWater1DJacobian.c.

{
  ShallowWater1D  *param = (ShallowWater1D*) p;
  static double   R[_MODEL_NVARS_*_MODEL_NVARS_], D[_MODEL_NVARS_*_MODEL_NVARS_], 
                  L[_MODEL_NVARS_*_MODEL_NVARS_], DL[_MODEL_NVARS_*_MODEL_NVARS_];

  /* get the eigenvalues and left,right eigenvectors */
  _ShallowWater1DEigenvalues_      (u,D,param,0);
  _ShallowWater1DLeftEigenvectors_ (u,L,param,0);
  _ShallowWater1DRightEigenvectors_(u,R,param,0);

  int aupw = absolute(upw), k;
  k = 0; D[k] = absolute( (1-aupw)*D[k] + 0.5*aupw*(1+upw)*max(0,D[k]) + 0.5*aupw*(1-upw)*min(0,D[k]) );
  k = 3; D[k] = absolute( (1-aupw)*D[k] + 0.5*aupw*(1+upw)*max(0,D[k]) + 0.5*aupw*(1-upw)*min(0,D[k]) );

  MatMult2(2,DL,D,L);
  MatMult2(2,Jac,R,DL);

  return(0);
}