Class modeling a thermostat which regulates the temperature of a Particle system. More...

#include <Thermostat.h>

Public Member Functions
	Thermostat (ParticleContainer &particles)
	Construct a new Thermostat with default-initialized values.

	Thermostat (ParticleContainer &particles, int dimension, double T_init, int n_thermostat, double T_target, double delta_T, bool initBrownianMotion, bool nanoFlow=false)
	Construct a complete Thermostat object with all parameters.

	~Thermostat ()
	Destroys the current Thermostat object.

void	initialize (int dimension, double T_init, int n_thermostat, double T_target, double delta_T, bool initBrownianMotion, bool nanoFlow=false, bool limitScaling=false)
	Initialize the current Thermostat's parameters.

void	initializeBrownianMotion ()
	Initialize the Particle velocities with Brownian Motion.

void	calculateKineticEnergy ()
	Calculates the kinetic energy \( E_{kin} \) for all Particle objects in the system.

void	calculateTemp ()
	Calculates the current temperature \( T \) of the system.

void	calculateScalingFactor ()
	Calculates the scaling factor \( \beta \).

void	calculateThermalMotions ()
	Calculates the thermal motion of each Particle in the system.

void	updateSystemTemp (int currentStep)
	Updates the system temperature after the number of iterations specified inside the Thermostat object.

double	getKineticEnergy () const
	Gets the kinetic energy \( E_{kin} \) of the active simulation particles.

double	getTemp () const
	Gets the current temperature \( T \) of the system.

double	getInitTemp () const
	Gets the starting temperature \( T_{init} \) of the system.

double	getTargetTemp () const
	Gets the target temperature \( T_{target} \) of the system.

double	getDeltaT () const
	Gets the maximum temperature difference \( \Delta T \) in one Thermostat application.

double	getScalingFactor () const
	Gets the scaling factor \( \beta \) by which to scale the Particle velocities.

bool	doScalingLimit () const
	Checks if the Thermostat should apply gradual or direct velocity scaling.

int	getTimestep () const
	Gets the number of simulation iterations after which to apply the Thermostat functionality.

bool	getNanoflow () const
	Determines whether the thermostat is used for the nano-scale flow simulation.

ParticleContainer &	getParticles () const
	Gets a reference to the Particle system.

bool	operator== (const Thermostat &other) const
	Overload of the equality operator. Checks if two Thermostat objects have the same values.

Private Attributes
int	dimension {2}
	The dimensions for which the Thermostat temperature regulation should be applied (default: 2).

double	kineticEnergy {0.0}
	The kinetic energy \( E_{kin} \) of the active simulation particles (default: 0).

double	temperature {0.0}
	The Temperature \( T \) of the system (default: 0).

double	scalingFactor {1.0}
	The scaling factor \( \beta \) by which to scale the Particle velocities (default: 1).

double	T_init {0.0}
	The starting temperature \( T_{init} \) of the system (default: 0).

double	T_target {0.0}
	The target temperature \( T_{target} \) of the system (default: \( T_{init} \)).

int	n_thermostat {1000}
	The number of simulation iterations after which to apply the Thermostat functionality (default: 1000).

double	delta_T {INFINITY}
	The maximum temperature difference \( \Delta T \) in one Thermostat application (default: \( \infty \)).

bool	limitScaling {false}
	Determines if the Thermostat should apply gradual velocity scaling or direct velocity scaling (default: direct).

bool	initBrownianMotion {true}
	Determines whether or not to initialize the velocities with Brownian Motion (default: on).

bool	nanoFlow {false}
	Determines whether the thermostat is used for the nano-scale flow simulation.

std::array< double, 3 >	avg_velocity {0, 0, 0}
	Average velocity of the system.

ParticleContainer &	particles
	A reference to the Particle system.

Detailed Description

Class modeling a thermostat which regulates the temperature of a Particle system.

Constructor & Destructor Documentation

◆ Thermostat() [1/2]

Thermostat::Thermostat ( ParticleContainer & particles )

explicit

Construct a new Thermostat with default-initialized values.

Parameters

particles The ParticleContainer representing the Particle system.

◆ Thermostat() [2/2]

Thermostat::Thermostat	(	ParticleContainer &	particles,
		int	dimension,
		double	T_init,
		int	n_thermostat,
		double	T_target,
		double	delta_T,
		bool	initBrownianMotion,
		bool	nanoFlow = `false`
	)

Construct a complete Thermostat object with all parameters.

Parameters

particles	The ParticleContainer representing the Particle system.
dimension	The dimensions for which the Thermostat temperature regulation should be applied.
T_init	The starting temperature \( T_{init} \) of the system.
n_thermostat	The number of simulation iterations after which to apply the Thermostat functionality.
T_target	The target temperature \( T_{target} \) of the system.
delta_T	The maximum temperature difference \( \Delta T \) in one Thermostat application.
initBrownianMotion	Determines whether or not to initialize the velocities with Brownian Motion.
nanoFlow	Determines whether the thermostat is used for the nano-scale flow simulation.

◆ ~Thermostat()

Thermostat::~Thermostat ( )

Destroys the current Thermostat object.

Member Function Documentation

◆ calculateKineticEnergy()

void Thermostat::calculateKineticEnergy ( )

Calculates the kinetic energy \( E_{kin} \) for all Particle objects in the system.

The kinetic energy is calculated using the formula

\[ E_{kin} = \sum_{i=1}^N \frac{m_i \langle v_i, v_i \rangle}{2} \]

where \( N \) denotes the total number of active Particle objects.

◆ calculateScalingFactor()

void Thermostat::calculateScalingFactor ( )

Calculates the scaling factor \( \beta \).

The scaling factor is calculated using the formula

\[ \beta = \sqrt{\frac{T_{new}}{T_{current}}} \]

where \( T_{new} \) is either the target temperature if no limit \( \Delta T \) is given or if the target temperature can be reached in the next thermostat application, or \( T_{current} \pm \Delta T \) otherwise (depending if the current temperature is above or below the target temperature).

◆ calculateTemp()

void Thermostat::calculateTemp ( )

Calculates the current temperature \( T \) of the system.

The temperature is calculated after getting the kinetic energy \( E_{kin} \) of all Particle objects in the system by rearranging the equation

\[ E_{kin} = \frac{D \cdot N}{2}k_B T \]

and solving for \( T \), with \( N \) being the total number of active Particle objects, \( D \) being the number of dimensions and \( k_B = 1 \).

◆ calculateThermalMotions()

void Thermostat::calculateThermalMotions ( )

Calculates the thermal motion of each Particle in the system.

First, the average velocity

\[ \tilde v = \frac1N \sum_{i=0}^N v_i \]

is determined using the velocities of each non-wall particle in the system. Then, for each particle, its thermal motion \( \hat v_i \) is calculated as the difference between the velocity and the average velocity.

◆ doScalingLimit()

bool Thermostat::doScalingLimit ( ) const

Checks if the Thermostat should apply gradual or direct velocity scaling.

◆ getDeltaT()

double Thermostat::getDeltaT ( ) const

Gets the maximum temperature difference \( \Delta T \) in one Thermostat application.

◆ getInitTemp()

double Thermostat::getInitTemp ( ) const

Gets the starting temperature \( T_{init} \) of the system.

◆ getKineticEnergy()

double Thermostat::getKineticEnergy ( ) const

Gets the kinetic energy \( E_{kin} \) of the active simulation particles.

◆ getNanoflow()

bool Thermostat::getNanoflow ( ) const

Determines whether the thermostat is used for the nano-scale flow simulation.

◆ getParticles()

ParticleContainer & Thermostat::getParticles ( ) const

Gets a reference to the Particle system.

◆ getScalingFactor()

double Thermostat::getScalingFactor ( ) const

Gets the scaling factor \( \beta \) by which to scale the Particle velocities.

◆ getTargetTemp()

double Thermostat::getTargetTemp ( ) const

Gets the target temperature \( T_{target} \) of the system.

◆ getTemp()

double Thermostat::getTemp ( ) const

Gets the current temperature \( T \) of the system.

◆ getTimestep()

int Thermostat::getTimestep ( ) const

Gets the number of simulation iterations after which to apply the Thermostat functionality.

◆ initialize()

void Thermostat::initialize	(	int	dimension,
		double	T_init,
		int	n_thermostat,
		double	T_target,
		double	delta_T,
		bool	initBrownianMotion,
		bool	nanoFlow = `false`,
		bool	limitScaling = `false`
	)

Initialize the current Thermostat's parameters.

Parameters

dimension	The dimensions for which the Thermostat temperature regulation should be applied.
T_init	The starting temperature \( T_{init} \) of the system.
n_thermostat	The number of simulation iterations after which to apply the Thermostat functionality.
T_target	The target temperature \( T_{target} \) of the system.
delta_T	The maximum temperature difference \( \Delta T \) in one Thermostat application.
initBrownianMotion	Determines whether or not to initialize the velocities with Brownian Motion.
nanoFlow	Determines whether the thermostat is used for the nano-scale flow simulation.
limitScaling	Determines if the Thermostat should apply gradual or direct velocity scaling.

◆ initializeBrownianMotion()

void Thermostat::initializeBrownianMotion ( )

Initialize the Particle velocities with Brownian Motion.

Assuming a Particle does not have an initial velocity, in order for the system to have a non-zero temperature, the velocity for any given Particle \( i \) is calculated using a Maxwell-Boltzmann distribution with the factor

\[ f_i = \sqrt{\frac{T_{init}}{m_i}}. \]

◆ operator==()

bool Thermostat::operator== ( const Thermostat & other ) const

Overload of the equality operator. Checks if two Thermostat objects have the same values.

Does not check if both objects reference the same ParticleContainer.

Parameters

other The other Thermostat to check the values against.

Returns: true if both Thermostat objects contain the same values.; false if both Thermostat objects do not contain the same values.

◆ updateSystemTemp()

void Thermostat::updateSystemTemp ( int currentStep )

Updates the system temperature after the number of iterations specified inside the Thermostat object.

For nanoscale simulations, the thermal motion of the particles inside the system are taken into account.

Parameters

currentStep The current iteration of the simulation, used to determine whether or not to apply the thermostat. In the first iteration, if initBrownianMotion is set, the Particle velocities will be initialized with Brownian Motion. Otherwise, nothing is done in the first iteration.

Member Data Documentation

◆ avg_velocity

std::array<double, 3> Thermostat::avg_velocity {0, 0, 0}

private

Average velocity of the system.

◆ delta_T

double Thermostat::delta_T {INFINITY}

private

The maximum temperature difference \( \Delta T \) in one Thermostat application (default: \( \infty \)).

If no temperature difference is specified (i.e. if the value is defaulted to INFINITY), the temperature is set directly in one Thermostat application.

◆ dimension

int Thermostat::dimension {2}

private

The dimensions for which the Thermostat temperature regulation should be applied (default: 2).

◆ initBrownianMotion

bool Thermostat::initBrownianMotion {true}

private

Determines whether or not to initialize the velocities with Brownian Motion (default: on).

◆ kineticEnergy

double Thermostat::kineticEnergy {0.0}

private

The kinetic energy \( E_{kin} \) of the active simulation particles (default: 0).

◆ limitScaling

bool Thermostat::limitScaling {false}

private

Determines if the Thermostat should apply gradual velocity scaling or direct velocity scaling (default: direct).

◆ n_thermostat

int Thermostat::n_thermostat {1000}

private

The number of simulation iterations after which to apply the Thermostat functionality (default: 1000).

Must be specified when initializing a Thermostat.

◆ nanoFlow

bool Thermostat::nanoFlow {false}

private

Determines whether the thermostat is used for the nano-scale flow simulation.

◆ particles

ParticleContainer& Thermostat::particles

private

A reference to the Particle system.

◆ scalingFactor

double Thermostat::scalingFactor {1.0}

private

The scaling factor \( \beta \) by which to scale the Particle velocities (default: 1).

◆ T_init

double Thermostat::T_init {0.0}

private

The starting temperature \( T_{init} \) of the system (default: 0).

Must be specified when initializing a Thermostat.

◆ T_target

double Thermostat::T_target {0.0}

private

The target temperature \( T_{target} \) of the system (default: \( T_{init} \)).

If no target temperature is given in the input, the target temperature is set to \( T_{init} \).

◆ temperature

double Thermostat::temperature {0.0}

private

The Temperature \( T \) of the system (default: 0).

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

src/objects/Thermostat.h

Public Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Thermostat() [1/2]

◆ Thermostat() [2/2]

◆ ~Thermostat()

Member Function Documentation

◆ calculateKineticEnergy()

◆ calculateScalingFactor()

◆ calculateTemp()

◆ calculateThermalMotions()

◆ doScalingLimit()

◆ getDeltaT()

◆ getInitTemp()

◆ getKineticEnergy()

◆ getNanoflow()

◆ getParticles()

◆ getScalingFactor()

◆ getTargetTemp()

◆ getTemp()

◆ getTimestep()

◆ initialize()

◆ initializeBrownianMotion()

◆ operator==()

◆ updateSystemTemp()

Member Data Documentation

◆ avg_velocity

◆ delta_T

◆ dimension

◆ initBrownianMotion

◆ kineticEnergy

◆ limitScaling

◆ n_thermostat

◆ nanoFlow

◆ particles

◆ scalingFactor

◆ T_init

◆ T_target

◆ temperature