LinearViscoelasticNormalSpecies Class Reference

LinearViscoelasticNormalSpecies contains the parameters used to describe a linear elastic-dissipative normal force. More...

#include <LinearViscoelasticNormalSpecies.h>

Inheritance diagram for LinearViscoelasticNormalSpecies:

Public Types
typedef LinearViscoelasticInteraction	InteractionType
	The correct Interaction type for this FrictionForceSpecies. More...

Public Member Functions
	LinearViscoelasticNormalSpecies ()
	The default constructor. More...
	LinearViscoelasticNormalSpecies (const LinearViscoelasticNormalSpecies &p)
	The default copy constructor. More...
	~LinearViscoelasticNormalSpecies ()
	The default destructor. More...
void	read (std::istream &is)
	Reads the species properties from an input stream. More...
void	write (std::ostream &os) const
	Writes the species properties to an output stream. More...
std::string	getBaseName () const
	Used in Species::getName to obtain a unique name for each Species. More...
Mdouble	getMaximumVelocity (Mdouble radius, Mdouble mass) const
	Calculates the maximum velocity allowed for a collision of two copies of P (for higher velocities particles could pass through each other) More...
void	setStiffnessAndRestitutionCoefficient (Mdouble k_, Mdouble eps, Mdouble mass)
	Sets k, disp such that it matches a given tc and eps for a collision of two copies of P. More...
void	setRestitutionCoefficient (double eps, Mdouble mass)
	Sets disp to obtain a restitution coefficient eps for a collision of two particles of mass m. More...
void	setCollisionTimeAndRestitutionCoefficient (Mdouble tc, Mdouble eps, BaseParticle *p)
	Sets k, disp such that it matches a given tc and eps for a collision of two copies of particle p. More...
void	setCollisionTimeAndRestitutionCoefficient (Mdouble tc, Mdouble eps, Mdouble mass)
	Sets k, disp such that it matches a given tc and eps for a collision of two copies of equal mass m. More...
void	setCollisionTimeAndRestitutionCoefficient (Mdouble collisionTime, Mdouble restitutionCoefficient, Mdouble mass1, Mdouble mass2)
Mdouble	getCollisionTime (Mdouble mass) const
	Calculates collision time for two copies of a particle of given disp, k, mass. More...
Mdouble	getRestitutionCoefficient (Mdouble mass) const
	Calculates restitution coefficient for two copies of given disp, k, mass. More...
void	mix (LinearViscoelasticNormalSpecies *SBase, LinearViscoelasticNormalSpecies *TBase)
	creates default values for mixed species More...
void	setStiffness (Mdouble new_k)
	Allows the spring constant to be changed. More...
Mdouble	getStiffness () const
	Allows the spring constant to be accessed. More...
void	setDissipation (Mdouble dissipation)
	Allows the normal dissipation to be changed. More...
Mdouble	getDissipation () const
	Allows the normal dissipation to be accessed. More...
MERCURYDPM_DEPRECATED void	setStiffnessAndDissipation (helpers::KAndDisp new_)
	Allows the spring and dissipation constants to be changed simultaneously. More...
Mdouble	computeTimeStep (Mdouble mass)
Public Member Functions inherited from BaseNormalForce
	BaseNormalForce ()
	BaseNormalForce (const BaseNormalForce &p)
bool	getConstantRestitution () const
void	setConstantRestitution (bool constantRestitution)
virtual void	actionsAfterTimeStep (BaseParticle *particle) const
Public Member Functions inherited from BaseForce
BaseSpecies *	getBaseSpecies () const
void	setBaseSpecies (BaseSpecies *baseSpecies)

Private Attributes
Mdouble	stiffness_
	(normal) spring constant More...
Mdouble	dissipation_
	(normal) viscosity More...

Detailed Description

LinearViscoelasticNormalSpecies contains the parameters used to describe a linear elastic-dissipative normal force.

See LinearViscoelasticNormalInteraction::computeForce for a description of the force law.

Member Typedef Documentation

InteractionType

typedef LinearViscoelasticInteraction LinearViscoelasticNormalSpecies::InteractionType

The correct Interaction type for this FrictionForceSpecies.

Constructor & Destructor Documentation

LinearViscoelasticNormalSpecies() [1/2]

LinearViscoelasticNormalSpecies::LinearViscoelasticNormalSpecies

(

)

The default constructor.

        : BaseNormalForce()
{
    stiffness_ = 0.0;
    dissipation_ = 0.0;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"LinearViscoelasticNormalSpecies::LinearViscoelasticNormalSpecies() finished"<<std::endl;
#endif
}

References dissipation_, and stiffness_.

LinearViscoelasticNormalSpecies() [2/2]

LinearViscoelasticNormalSpecies::LinearViscoelasticNormalSpecies

(

const LinearViscoelasticNormalSpecies &

p

)

The default copy constructor.

Parameters

[in]

the

species that is copied

        : BaseNormalForce(p)
{
    stiffness_ = p.stiffness_;
    dissipation_ = p.dissipation_;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"LinearViscoelasticNormalSpecies::LinearViscoelasticNormalSpecies(const LinearViscoelasticNormalSpecies &p) finished"<<std::endl;
#endif
}

References dissipation_, and stiffness_.

~LinearViscoelasticNormalSpecies()

LinearViscoelasticNormalSpecies::~LinearViscoelasticNormalSpecies

(

)

The default destructor.

{
#ifdef DEBUG_DESTRUCTOR
    std::cout<<"LinearViscoelasticNormalSpecies::~LinearViscoelasticNormalSpecies() finished"<<std::endl;
#endif
}

Member Function Documentation

computeTimeStep()

Mdouble LinearViscoelasticNormalSpecies::computeTimeStep ( Mdouble  mass )

inline

    {
        return 0.02 * constants::pi /
               std::sqrt(stiffness_ / (.5 * mass) - mathsFunc::square(dissipation_ / mass));
    }

References dissipation_, constants::pi, mathsFunc::square(), and stiffness_.

getBaseName()

std::string LinearViscoelasticNormalSpecies::getBaseName

(

)

const

Used in Species::getName to obtain a unique name for each Species.

Returns

a string containing the name of the species (minus the word "Species")

{
    return "LinearViscoelastic";
}

getCollisionTime()

Mdouble LinearViscoelasticNormalSpecies::getCollisionTime

(

Mdouble

mass

)

const

Calculates collision time for two copies of a particle of given disp, k, mass.

Calculates collision time for two copies of a particle of given disp, k, mass

Parameters

[in]

mass

mass of a typical particle

{
    if (getConstantRestitution()) mass = 1;
    if (mass <= 0)
    {
        logger(ERROR, "Warning in getCollisionTime(%) mass is not set or has an unexpected value, "
                      "(getCollisionTime(%)", mass, mass);
    }
    if (stiffness_ <= 0)
    {
        logger(ERROR, "Error in getCollisionTime(%) stiffness=% is not set or has an unexpected value "
                      "(getCollisionTime(%), with stiffness=%)",
               mass, stiffness_, mass, stiffness_);
    }
    if (dissipation_ < 0)
    {
        logger(ERROR, "Error in getCollisionTime(%) dissipation=% is not set or has an unexpected value "
                      "(getCollisionTime(%), with dissipation=%)",
               mass, dissipation_, mass, dissipation_);
    }
    Mdouble tosqrt = stiffness_ / (.5 * mass) - mathsFunc::square(dissipation_ / mass);
    if (tosqrt <= 0)
    {
        logger(ERROR, "Warning in getCollisionTime(%) values for mass, stiffness and dissipation would lead to an "
                      "overdamped system, (getCollisionTime(%), with stiffness=% and dissipation=%",
               mass, mass, stiffness_, dissipation_);
    }
    return constants::pi / std::sqrt(tosqrt);
}

References dissipation_, ERROR, BaseNormalForce::getConstantRestitution(), logger, constants::pi, mathsFunc::square(), and stiffness_.

Referenced by getRestitutionCoefficient(), main(), MaserRepeatedOutInMPI2Test::MaserRepeatedOutInMPI2Test(), ParticleCreation::ParticleCreation(), ParticleInclusion::ParticleInclusion(), ShiftingConstantMassFlowMaserBoundarySelfTest::setupInitialConditions(), ShiftingMaserBoundarySelfTest::setupInitialConditions(), ConstantMassFlowMaserBoundaryMixedSpeciesSelfTest::setupInitialConditions(), ConstantMassFlowMaserSelfTest::setupInitialConditions(), SubcriticalMaserBoundarySelfTest::setupInitialConditions(), Wall::setupInitialConditions(), EllipsoidsBouncingOnWallDemo::setupInitialConditions(), EllipticalSuperQuadricCollision::setupInitialConditions(), SphericalSuperQuadricCollision::setupInitialConditions(), VisualisationTest::setupInitialConditions(), Packing::setupInitialConditions(), SubcriticalMaserBoundaryTESTMPI2Test::SubcriticalMaserBoundaryTESTMPI2Test(), and viscoElasticUnitTest::viscoElasticUnitTest().

getDissipation()

Mdouble LinearViscoelasticNormalSpecies::getDissipation

(

)

const

Allows the normal dissipation to be accessed.

{
    return dissipation_;
}

References dissipation_.

Referenced by LinearViscoelasticInteraction::computeNormalForce(), main(), mix(), SilbertPeriodic::readNextArgument(), SilbertPeriodic::set_study(), setCollisionTimeAndRestitutionCoefficient(), and SilbertPeriodic::SilbertPeriodic().

getMaximumVelocity()

Mdouble LinearViscoelasticNormalSpecies::getMaximumVelocity	(	Mdouble	radius,
		Mdouble	mass
	)		const

Calculates the maximum velocity allowed for a collision of two copies of P (for higher velocities particles could pass through each other)

{
    return radius * std::sqrt(stiffness_ / (.5 * mass));
}

References stiffness_.

Referenced by main().

getRestitutionCoefficient()

Mdouble LinearViscoelasticNormalSpecies::getRestitutionCoefficient

(

Mdouble

mass

)

const

Calculates restitution coefficient for two copies of given disp, k, mass.

{
    if (getConstantRestitution()) mass = 1;
    return std::exp(-dissipation_ / mass * getCollisionTime(mass));
}

References dissipation_, mathsFunc::exp(), getCollisionTime(), and BaseNormalForce::getConstantRestitution().

Referenced by main(), CubicCell::setupInitialConditions(), and SubcriticalMaserBoundaryTESTMPI2Test::SubcriticalMaserBoundaryTESTMPI2Test().

getStiffness()

Mdouble LinearViscoelasticNormalSpecies::getStiffness

(

)

const

Allows the spring constant to be accessed.

{
    return stiffness_;
}

References stiffness_.

Referenced by LinearViscoelasticInteraction::computeNormalForce(), LinearViscoelasticInteraction::getElasticEnergy(), LinearViscoelasticInteraction::getElasticEnergyAtEquilibrium(), main(), mix(), SilbertPeriodic::set_study(), SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficient(), SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficientNoDispt(), setCollisionTimeAndRestitutionCoefficient(), setRestitutionCoefficient(), Wall::setupInitialConditions(), and SilbertPeriodic::SilbertPeriodic().

mix()

void LinearViscoelasticNormalSpecies::mix	(	LinearViscoelasticNormalSpecies *	SBase,
		LinearViscoelasticNormalSpecies *	TBase
	)

creates default values for mixed species

For all parameters we assume that the harmonic mean of the parameters of the original two species is a sensible default.

Parameters

[in]

S,T

the two species whose properties are mixed to create the new species

{
    stiffness_ = BaseSpecies::average(S->getStiffness(), T->getStiffness());
    dissipation_ = BaseSpecies::average(S->getDissipation(), T->getDissipation());
}

References BaseSpecies::average(), dissipation_, getDissipation(), getStiffness(), and stiffness_.

read()

void LinearViscoelasticNormalSpecies::read

(

std::istream &

is

)

Reads the species properties from an input stream.

Parameters

[in]

input

stream (typically the restart file)

{
    std::string dummy;
    is >> dummy >> stiffness_
       >> dummy >> dissipation_;
}

References dissipation_, and stiffness_.

setCollisionTimeAndRestitutionCoefficient() [1/3]

void LinearViscoelasticNormalSpecies::setCollisionTimeAndRestitutionCoefficient	(	Mdouble	collisionTime,
		Mdouble	restitutionCoefficient,
		Mdouble	mass1,
		Mdouble	mass2
	)

Set k, disp such that is matches a given tc and eps for a collision of two different masses. Recall the resitution constant is a function of k, disp and the mass of each particle in the collision See also setCollisionTimeAndRestitutionCoefficient(Mdouble tc, Mdouble eps, Mdouble mass)

Set k, disp such that is matches a given tc and eps for a collision of two different masses. Recall the resitution constant is a function of k, disp and the mass of each particle in the collision See also setCollisionTimeAndRestitutionCoefficient(Mdouble tc, Mdouble eps, Mdouble mass)

Parameters

[in]

collision

time

{
    Mdouble reduced_mass = mass1 * mass2 / (mass1 + mass2);
    setCollisionTimeAndRestitutionCoefficient(collisionTime, restitutionCoefficient, 2.0 * reduced_mass);
}

References setCollisionTimeAndRestitutionCoefficient().

setCollisionTimeAndRestitutionCoefficient() [2/3]

void LinearViscoelasticNormalSpecies::setCollisionTimeAndRestitutionCoefficient	(	Mdouble	tc,
		Mdouble	eps,
		BaseParticle *	p
	)

Sets k, disp such that it matches a given tc and eps for a collision of two copies of particle p.

{
    Mdouble mass = p->getSpecies()->getDensity() * p->getVolume();
    setCollisionTimeAndRestitutionCoefficient(tc, eps, mass);
}

References ParticleSpecies::getDensity(), BaseInteractable::getSpecies(), and BaseParticle::getVolume().

Referenced by BouncingSuperQuadric::BouncingSuperQuadric(), main(), MaserRepeatedOutInMPI2Test::MaserRepeatedOutInMPI2Test(), SilbertPeriodic::set_study(), SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficient(), SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficientNoDispt(), setCollisionTimeAndRestitutionCoefficient(), AxisymmetricWallSelfTest::setSpeciesAndTimeStep(), ShiftingConstantMassFlowMaserBoundarySelfTest::setupInitialConditions(), ShiftingMaserBoundarySelfTest::setupInitialConditions(), PolydisperseInsertionBoundarySelfTest::setupInitialConditions(), Packing::setupInitialConditions(), MovingIntersectionOfWallsUnitTest_Basic::setupInitialConditions(), WallSpecies::setupInitialConditions(), and SubcriticalMaserBoundaryTESTMPI2Test::SubcriticalMaserBoundaryTESTMPI2Test().

setCollisionTimeAndRestitutionCoefficient() [3/3]

void LinearViscoelasticNormalSpecies::setCollisionTimeAndRestitutionCoefficient	(	Mdouble	tc,
		Mdouble	eps,
		Mdouble	mass
	)

Sets k, disp such that it matches a given tc and eps for a collision of two copies of equal mass m.

Sets k, disp such that it matches a given tc and eps for a collision of two copies of equal mass m

Parameters

[in]	tc	collision time
[in]	eps	restitution coefficient
[in]	mass	harmonic average particle mass, \(\frac{2}{1/m1+1/m2}\)

{
    logger.assert_always(tc>0, "collision time has to be positive");
    logger.assert_always(eps>=0 && eps<=1, "restitution has to be in [0,1]");
    logger.assert_always(mass>0, "mass has to be positive");
    if (getConstantRestitution()) mass = 1;
    if (eps == 0.0)
    {
        stiffness_ = .5 * mass * mathsFunc::square(constants::pi / tc);
        dissipation_ = std::sqrt(2.0 * mass * stiffness_);
    }
    else
    {
        dissipation_ = -mass / tc * mathsFunc::log(eps);
        stiffness_ = .5 * mass * (mathsFunc::square(constants::pi / tc)
                                  + mathsFunc::square(dissipation_ / mass));
    }
    logger(INFO,
           "setCollisionTimeAndRestitutionCoefficient: set stiffness to % and dissipation to % to obtain a collision time of % and a restitution coefficient of % for two particles of mass %",
           getStiffness(), getDissipation(), tc, eps, mass);
}

References dissipation_, BaseNormalForce::getConstantRestitution(), getDissipation(), getStiffness(), INFO, mathsFunc::log(), logger, constants::pi, mathsFunc::square(), and stiffness_.

setDissipation()

void LinearViscoelasticNormalSpecies::setDissipation

(

Mdouble

dissipation

)

Allows the normal dissipation to be changed.

{
    if (dissipation >= 0)
    {
        dissipation_ = dissipation;
    }
    else
    {
        logger(ERROR, "Error in setDissipation(%)", dissipation);
    }
}

References dissipation_, ERROR, and logger.

Referenced by FreeCooling2DinWallsDemo::actionsAfterTimeStep(), FreeCooling3DDemoProblem::actionsAfterTimeStep(), FreeCooling3DinWallsDemo::actionsAfterTimeStep(), FreeCoolingDemoProblem::actionsAfterTimeStep(), InsertionBoundaryMPI2Test::InsertionBoundaryMPI2Test(), main(), ParticleInclusion::ParticleInclusion(), protectiveWall::protectiveWall(), SpeciesHandler::readOldObject(), setStiffnessAndDissipation(), CubicCell::setupInitialConditions(), ConstantMassFlowMaserBoundaryMixedSpeciesSelfTest::setupInitialConditions(), ConstantMassFlowMaserSelfTest::setupInitialConditions(), SubcriticalMaserBoundarySelfTest::setupInitialConditions(), EllipsoidsBouncingOnWallDemo::setupInitialConditions(), EllipticalSuperQuadricCollision::setupInitialConditions(), SphericalSuperQuadricCollision::setupInitialConditions(), VisualisationTest::setupInitialConditions(), FreeFall::setupInitialConditions(), ContactDetectionWithWallTester::setupParticleAndWall(), ContactDetectionTester::setupParticles(), SilbertPeriodic::SilbertPeriodic(), and T_protectiveWall::T_protectiveWall().

setRestitutionCoefficient()

void LinearViscoelasticNormalSpecies::setRestitutionCoefficient	(	double	eps,
		Mdouble	mass
	)

Sets disp to obtain a restitution coefficient eps for a collision of two particles of mass m.

Sets k, disp such that it matches a given tc and eps for a collision of two copies of P

Parameters

[in]	stiffness	stiffness
[in]	eps	restitution coefficient
[in]	mass	effective particle mass, \(\frac{2}{1/m1+1/m2}\)

{
    if (getConstantRestitution()) mass = 1;
    if (eps == 0.0) {
        dissipation_ = std::sqrt(2.0 * mass * getStiffness());
    } else {
        const Mdouble logEps = log(eps);
        dissipation_ = -std::sqrt(2.0 * mass * getStiffness()
                                  / (constants::sqr_pi + mathsFunc::square(logEps))) * logEps;
    }
}

References dissipation_, BaseNormalForce::getConstantRestitution(), getStiffness(), mathsFunc::log(), constants::sqr_pi, and mathsFunc::square().

Referenced by setStiffnessAndRestitutionCoefficient().

setStiffness()

void LinearViscoelasticNormalSpecies::setStiffness

(

Mdouble

new_k

)

Allows the spring constant to be changed.

{
    if (new_k >= 0)
        stiffness_ = new_k;
    else
    {
        logger(ERROR, "setStiffness(%) argument has to be non-negative!", new_k);
    }
}

References ERROR, logger, and stiffness_.

Referenced by Contact::Contact(), InsertionBoundaryMPI2Test::InsertionBoundaryMPI2Test(), InsertionBoundarySelfTest::InsertionBoundarySelfTest(), main(), ParticleInclusion::ParticleInclusion(), protectiveWall::protectiveWall(), SpeciesHandler::readOldObject(), setStiffnessAndDissipation(), CubicCell::setupInitialConditions(), ConstantMassFlowMaserBoundaryMixedSpeciesSelfTest::setupInitialConditions(), ConstantMassFlowMaserSelfTest::setupInitialConditions(), CubeDeletionBoundarySelfTest::setupInitialConditions(), DeletionBoundarySelfTest::setupInitialConditions(), DistributionSelfTest::setupInitialConditions(), DistributionToPSDSelfTest::setupInitialConditions(), InsertionBoundarySelfTest::setupInitialConditions(), MultiplePSDSelfTest::setupInitialConditions(), PSDManualInsertionSelfTest::setupInitialConditions(), PSDSelfTest::setupInitialConditions(), SubcriticalMaserBoundarySelfTest::setupInitialConditions(), EllipsoidsBouncingOnWallDemo::setupInitialConditions(), EllipticalSuperQuadricCollision::setupInitialConditions(), SphericalSuperQuadricCollision::setupInitialConditions(), VisualisationTest::setupInitialConditions(), ParticleParticleInteraction::setupInitialConditions(), ParticleWallInteraction::setupInitialConditions(), FreeFall::setupInitialConditions(), SeparateFilesSelfTest::setupInitialConditions(), ContactDetectionWithWallTester::setupParticleAndWall(), ContactDetectionTester::setupParticles(), SilbertPeriodic::SilbertPeriodic(), T_protectiveWall::T_protectiveWall(), and Wall::Wall().

setStiffnessAndDissipation()

void LinearViscoelasticNormalSpecies::setStiffnessAndDissipation

(

helpers::KAndDisp

new_

)

Allows the spring and dissipation constants to be changed simultaneously.

{
    setStiffness(new_.k);
    setDissipation(new_.disp);
}

References helpers::KAndDisp::disp, helpers::KAndDisp::k, setDissipation(), and setStiffness().

setStiffnessAndRestitutionCoefficient()

void LinearViscoelasticNormalSpecies::setStiffnessAndRestitutionCoefficient	(	Mdouble	stiffness,
		Mdouble	eps,
		Mdouble	mass
	)

Sets k, disp such that it matches a given tc and eps for a collision of two copies of P.

Sets k, disp such that it matches a given tc and eps for a collision of two copies of P

Parameters

[in]	stiffness	stiffness
[in]	eps	restitution coefficient
[in]	harmonic	mean of particle masses, \(\frac{2}{1/m1+1/m2}\)

{
    if (getConstantRestitution()) mass = 1;
    stiffness_ = stiffness;
    setRestitutionCoefficient(eps, mass);
}

References BaseNormalForce::getConstantRestitution(), setRestitutionCoefficient(), and stiffness_.

Referenced by main(), ParticleCreation::ParticleCreation(), SilbertPeriodic::set_study(), Packing::setupInitialConditions(), StressStrainControl::StressStrainControl(), and viscoElasticUnitTest::viscoElasticUnitTest().

write()

void LinearViscoelasticNormalSpecies::write

(

std::ostream &

os

)

const

Writes the species properties to an output stream.

Parameters

[out]

output

stream (typically the restart file)

{
    os << " stiffness " << stiffness_
       << " dissipation " << dissipation_;
}

References dissipation_, and stiffness_.

Member Data Documentation

dissipation_

Mdouble LinearViscoelasticNormalSpecies::dissipation_

private

(normal) viscosity

Referenced by computeTimeStep(), getCollisionTime(), getDissipation(), getRestitutionCoefficient(), LinearViscoelasticNormalSpecies(), mix(), read(), setCollisionTimeAndRestitutionCoefficient(), setDissipation(), setRestitutionCoefficient(), and write().

stiffness_

Mdouble LinearViscoelasticNormalSpecies::stiffness_

private

(normal) spring constant

Referenced by computeTimeStep(), getCollisionTime(), getMaximumVelocity(), getStiffness(), LinearViscoelasticNormalSpecies(), mix(), read(), setCollisionTimeAndRestitutionCoefficient(), setStiffness(), setStiffnessAndRestitutionCoefficient(), and write().

---

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

• LinearViscoelasticNormalSpecies.h
• LinearViscoelasticNormalSpecies.cc