RelativeThermostat Class Reference

A relative thermostat that can be used to control the temperature of a particle container. Allows for gradual scaling of the temperature towards a set target. More...

#include <RelativeThermostat.h>

Inheritance diagram for RelativeThermostat:

Collaboration diagram for RelativeThermostat:

Public Member Functions
	RelativeThermostat (double target_temperature, double max_temperature_change=std::numeric_limits< double >::max(), ThirdDimension third_dimension=ThirdDimension::ENABLED)
	Construct a new Thermostat object. More...
void	scaleTemperature (const std::unique_ptr< ParticleContainer > &particle_container) const override
	Scale the temperature of a particle container towards the target temperature. Capped by the maximum temperature change. More...
double	getContainerKineticEnergy (const std::unique_ptr< ParticleContainer > &particle_container, std::array< double, 3 > average_velocity) const
	Get the kinetic energy of a particle. More...
double	getCurrentContainerTemperature (const std::unique_ptr< ParticleContainer > &particle_container, std::array< double, 3 > average_velocity) const
	Get the current temperature of a particle. More...
double	getCurrentContainerTemperature (const std::unique_ptr< ParticleContainer > &particle_container) const override
	Get the current temperature of a particle container. More...
Public Member Functions inherited from Thermostat
	Thermostat (double target_temperature, double max_temperature_change, ThirdDimension third_dimension)
	Construct a new Thermostat object. More...
virtual	~Thermostat ()=default
	Destroy the Thermostat object. More...
void	setTemperature (double new_temperature, const std::unique_ptr< ParticleContainer > &particle_container)
	Set the initial temperature of a particle container. This function sets the velocity of all particles in the container to a random value according to the Maxwell-Boltzmann distribution (all previous velocities are discarded). Use this function for systems with no initial velocity. More...
double	getTargetTemperature () const
	Get the target temperature of the thermostat. More...
double	getMaxTemperatureChange () const
	Get the maximum temperature change of the thermostat. More...
ThirdDimension	getThirdDimension () const
	Get if the third dimension is enabled on this thermostat or not. More...

Additional Inherited Members
Static Public Member Functions inherited from Thermostat
static void	setParticleTemperature (double new_temperature, Particle &particle, ThirdDimension third_dimension)
	Set the temperature of a particle. This method adds a random velocity to the particle according to the Maxwell-Boltzmann distribution. This function can be used for particle generators since previous velocities are not discarded. More...
Protected Attributes inherited from Thermostat
const double	target_temperature
	The target temperature for thermostat applications. More...
const double	max_temperature_change
	The maximum temperature change allowed per thermostat application. More...
const ThirdDimension	third_dimension
	Defines whether the third dimension is enabled. More...

Detailed Description

A relative thermostat that can be used to control the temperature of a particle container. Allows for gradual scaling of the temperature towards a set target.

This thermostat is a basic implementation of the Thermostat interface.

This Thermostats is "relative" in the sense that it takes the actual "average" velocity of the particles into account when scaling the temperature. This means that the particles jiggle gets reduced, but in total the particles will still move if given an initial velocity.

Definition at line 19 of file RelativeThermostat.h.

Constructor & Destructor Documentation

RelativeThermostat()

RelativeThermostat::RelativeThermostat	(	double	target_temperature,
		double	max_temperature_change = std::numeric_limits<double>::max(),
		ThirdDimension	third_dimension = ThirdDimension::ENABLED
	)

Construct a new Thermostat object.

Parameters

target_temperature	The target temperature for thermostat applications.
max_temperature_change	The maximum temperature change allowed per thermostat application.
third_dimension	Wether the thermostat applies to a 3-dimensional domain or 2 dimensions.

Definition at line 7 of file RelativeThermostat.cpp.

    : Thermostat(target_temperature, max_temperature_change, third_dimension) {}

Member Function Documentation

getContainerKineticEnergy()

double RelativeThermostat::getContainerKineticEnergy	(	const std::unique_ptr< ParticleContainer > &	particle_container,
		std::array< double, 3 >	average_velocity
	)		const

Get the kinetic energy of a particle.

Parameters

particle_container	The particle container to get the kinetic energy of.
average_velocity	The average velocity of all particles in the container.

Returns

double The kinetic energy of the particle.

Definition at line 36 of file RelativeThermostat.cpp.

                                                                                                 {
    double total_kinetic_energy = 0;
    for (auto& particle : *particle_container) {
        if (particle.isLocked()) continue;
        std::array<double, 3> v = particle.getV() - average_velocity;
        total_kinetic_energy += particle.getM() * (v[0] * v[0] + v[1] * v[1] + v[2] * v[2]) * 0.5;
    }
    return total_kinetic_energy;
}

getCurrentContainerTemperature() [1/2]

double RelativeThermostat::getCurrentContainerTemperature ( const std::unique_ptr< ParticleContainer > &  particle_container ) const

overridevirtual

Get the current temperature of a particle container.

Parameters

particle_container

The particle container to get the temperature of.

Returns

double The current temperature of the particle container.

Implements Thermostat.

Definition at line 53 of file RelativeThermostat.cpp.

                                                                                                                          {
    return getCurrentContainerTemperature(particle_container, averageVelocity(particle_container));
}

getCurrentContainerTemperature() [2/2]

double RelativeThermostat::getCurrentContainerTemperature	(	const std::unique_ptr< ParticleContainer > &	particle_container,
		std::array< double, 3 >	average_velocity
	)		const

Get the current temperature of a particle.

Parameters

particle_container	The particle container to get the temperature of.
average_velocity	The average velocity of all particles in the container.

Definition at line 47 of file RelativeThermostat.cpp.

                                                                                                      {
    double dimension_count = third_dimension == ThirdDimension::ENABLED ? 3 : 2;
    return 2 * getContainerKineticEnergy(particle_container, average_velocity) / (dimension_count * particle_container->size());
}

scaleTemperature()

void RelativeThermostat::scaleTemperature ( const std::unique_ptr< ParticleContainer > &  particle_container ) const

overridevirtual

Scale the temperature of a particle container towards the target temperature. Capped by the maximum temperature change.

Parameters

particle_container

The particle container to scale the temperature of.

Implements Thermostat.

Definition at line 21 of file RelativeThermostat.cpp.

                                                                                                          {
    const std::array<double, 3> average_velocity = averageVelocity(particle_container);
 
    const double current_temperature = getCurrentContainerTemperature(particle_container, average_velocity);
    const double temperature_change = std::min(std::abs(target_temperature - current_temperature), max_temperature_change);
    const double new_temperature = current_temperature + temperature_change * (target_temperature > current_temperature ? 1 : -1);
 
    const double scaling_factor = std::sqrt(new_temperature / current_temperature);
 
    for (auto& particle : *particle_container) {
        if (particle.isLocked()) continue;
        particle.setV(average_velocity + scaling_factor * (particle.getV() - average_velocity));
    }
}

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

• RelativeThermostat.h
• RelativeThermostat.cpp