Class to set density and pressure floors for MHD fluid. More...

#include <set_floors.h>

Inheritance diagram for wxm::apps::functions::mhd::SetFloors:

Detailed Description

Class to set density and pressure floors for MHD fluid.

!!WARNING: Does not conserve density or energy.!!

Density and pressure floors are a brute-force method of enforcing positivity in regions where numerical oscillations, or where the kinetic or magnetic energy is large compared to the thermal energy, resulting in density or pressures going negative.

In the methods implemented here, when the density or pressure at a node is found to be below a threshold value ( \(\rho_{min}\) or \(P_{min}\)) the value is replaced. The replacement value is calculated one of two ways:

_eliminate_ke == false (Default). When density or pressure fall below threshold values density and energy are recalculated using \(\rho_{min}\) and \(P_{min}\)
\begin{align*} \rho_{out} &= \max (\rho_{min}, \rho_{in}) \\ \boldsymbol{p}_{out} &= \boldsymbol{p}_{in}, \\ e_{out} &= \frac{1}{\gamma-1} \max (P_{min}, P_{in}) + \frac{1}{2} \max \left( \rho_{min}, \rho_{in} \right)^{-1} \left(p_x^2 + p_y^2 + p_z^2 \right)_{in}. \end{align*}
_eliminate_ke == true. When density falls below \(\rho_{min}\), the momentum is set to zero and kinetic energy is subtracted from total energy
\begin{align*} \rho_{out} &= \rho_{min}, \\ \boldsymbol{p}_{out} &= 0, \\ e_{out} &= \frac{1}{\gamma - 1} P_{min}. \end{align*}
In cases where \(\rho > \rho_{min}\)

\begin{align*} \rho_{out} &= \rho_{in}, \\ \boldsymbol{p}_{out} &= \boldsymbol{p}_{in}, \\ e_{out} &= \frac{1}{\gamma-1} \max (P_{min}, P_{in}) + \frac{1}{2 \rho_{in}} \left(p_x^2 + p_y^2 + p_z^2 \right)_{in}. \end{align*}

Public Member Functions
	SetFloors ()
	Constructor.

	~SetFloors () override
	Destructor.

void	setup (const WxCryptSet &wxc) override
	Setup.

const std::vector< int > &	getInputVariableIndexes (int flag) const override
	Grab input variable indices.

const std::vector< int > &	getOutputVariableIndexes (int flag) const override
	Grab output variable indices.

void	evaluate_function (const real q, const real aux, const solverVariables_t pSV, real result) const override
	Redefinition of the function evaluator.

Public Member Functions inherited from WmApplication
	WmApplication ()

virtual	~WmApplication ()=default

virtual void	setup (const WxCryptSet &wxc)

virtual const std::vector< int > &	getAuxiliaryVariableIndexes (int flag=WMAPPLICATIONFLAG_NONE) const

virtual const std::vector< int > &	getCrossVariableIndexes (int flag=WMAPPLICATIONFLAG_NONE) const

const std::vector< std::string > &	getBoundaryNames () const

bool	isOnBoundary (const std::string &boundaryName) const

bool	has (int flag) const

virtual real	numerical_flux (const real q_l, const real q_r, const real aux_l, const real aux_r, const solverVariables_t pFV, real numericalFlux) const

virtual real	internal_flux (const real q, const real aux, const solverVariables_t *pSV, std::vector< std::vector< real > > &internalFlux) const

virtual real	source (const real q, const real aux, const elementGeometry_t pEG, real source) const

virtual void	bc_q (const real q_in, const real aux_in, const real aux_out, const solverVariables_t pFV, real *q_out) const
	Boundary Condition Application which sets the boundary condition on ghost nodes.

virtual real	bcNumericalFlux (const real q_l, const real q_r, const real aux_l, const real aux_r, const solverVariables_t pFV, real numericalFlux) const

virtual void	conserved_to_primitive (const real q, const real aux, real *w) const

virtual void	primitive_to_conserved (const real w, const real aux, real *q) const

virtual void	evaluate_function (const real q, const real aux, const solverVariables_t pSV, real result) const

virtual void	bc_q_kinetic (const real q_in, const real aux_in, const solverVariables_t pFV, real q_out) const

std::shared_ptr< std::string >	app_name ()

virtual const std::vector< int > &	getInputVariableIndexes (int flag=0) const

virtual const std::vector< int > &	getOutputVariableIndexes (int flag=0) const

Protected Attributes
std::vector< int >	_fluid
	Vector of MHD fluid variable indices.

real	_gas_gamma
	Ratio of specific heats.

real	_rho_min
	Mass density floor.

real	_p_min
	Pressure floor.

bool	_eliminate_ke
	Floor method toggle.

Protected Attributes inherited from WmApplication
std::string	_app_name

WxLogStream	_debStrm

std::vector< int >	_allowedFlags

std::vector< std::string >	_onBoundaries

Additional Inherited Members
Public Types inherited from WmApplication
typedef Application_Variable	WmApplication_Variable

typedef std::map< std::string, std::string >	replaceMap_t

Static Public Attributes inherited from wxm::app_base
static std::vector< int >	empty

Protected Member Functions inherited from wxm::app_base
virtual	~app_base ()=default

Constructor & Destructor Documentation

◆ SetFloors()

wxm::apps::functions::mhd::SetFloors::SetFloors ( )

Constructor.

◆ ~SetFloors()

wxm::apps::functions::mhd::SetFloors::~SetFloors ( )

override

Destructor.

Member Function Documentation

◆ evaluate_function()

void wxm::apps::functions::mhd::SetFloors::evaluate_function	(	const real *	q,
		const real *	aux,
		const solverVariables_t *	pSV,
		real *	result
	)		const

overridevirtual

Redefinition of the function evaluator.

Parameters

const	q - input variable
const	aux - auxiliary variable
const	pSV - solver variable structure
result	- output variable

Reimplemented from WmApplication.

◆ getInputVariableIndexes()

const std::vector< int > & wxm::apps::functions::mhd::SetFloors::getInputVariableIndexes ( int flag ) const

inlineoverridevirtual

Grab input variable indices.

Parameters

int	flag - usually flag is given like flux type but usually not checked

Returns: vector of input variable indices

Reimplemented from wxm::app_base.

◆ getOutputVariableIndexes()

const std::vector< int > & wxm::apps::functions::mhd::SetFloors::getOutputVariableIndexes ( int flag ) const

inlineoverridevirtual

Grab output variable indices.

Parameters

int	flag - usually flag is given like flux type but usually not checked

Returns: vector of output variable indices

Reimplemented from wxm::app_base.

◆ setup()

void wxm::apps::functions::mhd::SetFloors::setup ( const WxCryptSet & wxc )

overridevirtual

Setup.

Parameters

WxCryptSet object

Reimplemented from WmApplication.

Member Data Documentation

◆ _eliminate_ke

bool wxm::apps::functions::mhd::SetFloors::_eliminate_ke

protected

Floor method toggle.

See detailed notes. Default False.

◆ _fluid

std::vector<int> wxm::apps::functions::mhd::SetFloors::_fluid

protected

Vector of MHD fluid variable indices.

Len 8.

◆ _gas_gamma

real wxm::apps::functions::mhd::SetFloors::_gas_gamma

protected

Ratio of specific heats.

◆ _p_min

real wxm::apps::functions::mhd::SetFloors::_p_min

protected

Pressure floor.

◆ _rho_min

real wxm::apps::functions::mhd::SetFloors::_rho_min

protected

Mass density floor.

The documentation for this class was generated from the following file:

src/apps/function_evaluators/mhd/set_floors.h

Detailed Description

Public Member Functions

Protected Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ SetFloors()

◆ ~SetFloors()

Member Function Documentation

◆ evaluate_function()

◆ getInputVariableIndexes()

◆ getOutputVariableIndexes()

◆ setup()

Member Data Documentation

◆ _eliminate_ke

◆ _fluid

◆ _gas_gamma

◆ _p_min

◆ _rho_min