entropy_switch.c File Reference

Flag zones where pressure is updated using entropy. More...

#include "pluto.h"

Functions
void	EntropySwitch (const Data *d, Grid *grid)

Detailed Description

Flag cells where pressure has to be updated from the conserved entropy density and compute entropy at the beginning of each integration stage.

The flagging strategy is based on two switches designed to detect the presence of compressive motion or shock waves in the fluid:

• 
• 

By default, if at least one of the switch is FALSE, we flag the computational zone by turning the FLAG_ENTROPY bit of the d->flag array on. In this way, the default strategy is to evolve the entropy equation everywhere, except at shocks (where both switches are TRUE).

This flag will be checked later in the ConsToPrim() functions in order to recover pressure from the entropy density rather than from the total energy density. The update process is:

• start with a vector of primitive variables {V,s} where s is the entropy;
• set boundary condition on {V}; compute {s} from {V}; flag zones where entropy may be used (flag = 1);
• evolve equations for one time step;
• convert {U,S} to primitive:

  where (flag == 0) {
    p = p(E);
  }else{  
    p = p(S);
    correct E using new p;
  }
  

Reference

• "Maintaining Pressure Positivity in Magnetohydrodynamics Simulations" Balsara & Spicer, JCP (1999) 148, 133

Author

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

Date

Aug 16, 2012

Function Documentation

void EntropySwitch	(	const Data *	d,
		Grid *	grid
	)

Compute entropy and flag zones for updating pressure using the conserved entropy density.

Parameters

[in,out]	d	pointer to Data structure
[in]	grid	pointer to an array of Grid structures.

Returns

This function has no return value.

< Update pressure using entropy equation.