char_tracing.c File Reference

Compute time-centered interface states using characteristic tracing. More...

#include "pluto.h"

Macros
#define	REF_STATE   2

Functions
void	CharTracingStep (const State_1D *state, int beg, int end, Grid *grid)

Detailed Description

Advance 1-D left and right interface states, previously computed with any of the States functions, to the half time level (n+1/2) by extrapolating characteristic variables. This is done using an upwind selection rule that discards waves not reaching the interface in dt/2.

References:

• "The PLUTO Code for Adaptive Mesh Refinement in Astrophysical Fluid Dynamics"
  Mignone et al, ApJS (2012) 198, 7M

Author

A. Mignone (migno.nosp@m.ne@p.nosp@m.h.uni.nosp@m.to.i.nosp@m.t)

Date

Sept 17, 2012

Macro Definition Documentation

#define REF_STATE   2

Flag to control the choice of the reference state in the upwind selection rule. Set REF_STATE to 1,2,3 to use cell centered value (1), interpolated states (2) or fastest wave (3, the usual PPM prescription).

Function Documentation

void CharTracingStep	(	const State_1D *	state,
		int	beg,
		int	end,
		Grid *	grid
	)

Compute interface states using characteristic tracing step.

Parameters

[in]	state	pointer to a State_1D structure
[in]	beg	initial index of computation
[in]	end	final index of computation
[in]	grid	pointer to an array of Grid structures

Returns

This function has no return value.

Tasks are numbered below.

1) Compute eigenvectors and eigenvalues if not yet defined.

2) Obtain characteristic variable increments dwp and dwm.

3) Initialize vp and vm to the reference state. Since this is somewhat arbitrary we use the value of REF_STATE to select one of the following cases:

• REF_STATE==1: use cell-center value;
• REF_STATE==2: interpolated value at base time level
• REF_STATE==3: traditional PPM reference state (fastest wave), minimize the size of the term subject to characteristic limiting.

Passive scalars use always REF_STATE == 2.

4) Compute left and right states in primitive variables. This step also depends on the value of REF_STATE and include:

• evolve characteristic variable increments by dt/2;
• discard contributions from waves not reaching the interface;
• project characteristic differences dwp and dwm onto right eigenvectors

5) Add source term to L/R states

6) Repeat construction for passive scalars