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Feature/spring damper #6

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Jun 16, 2021
Merged

Feature/spring damper #6

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34e77ea
running avg for spring and damper force
BenceVirtonomy Jun 16, 2021
08d66df
spring damper fixed
BenceVirtonomy Jun 16, 2021
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34 changes: 21 additions & 13 deletions SPHINXsys/src/shared/particle_dynamics/solid_dynamics/solid_dynamics.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -374,43 +374,51 @@ namespace SPH
pos_n_(particles_->pos_n_),
pos_0_(particles_->pos_0_),
vel_n_(particles_->vel_n_),
dvel_dt_prior_(particles_->dvel_dt_prior_),
mass_(particles_->mass_)
dvel_dt_prior_(particles_->dvel_dt_prior_)
{
stiffness_ = stiffness;
damping_ratio_ = damping_ratio;
// calculate total mass
total_mass_ = 0.0;
for (int i = 0; i < particles_->mass_.size(); i++)
{
total_mass_ += particles_->mass_[i];
}
// scale stiffness and damping by mass here, so it's not necessary in each iteration
stiffness_ = stiffness / total_mass_;
damping_coeff_ = stiffness * damping_ratio / total_mass_;
}
//=================================================================================================//
SpringDamperConstraintParticleWise::~SpringDamperConstraintParticleWise()
{}
//=================================================================================================//
void SpringDamperConstraintParticleWise::setupDynamics(Real dt)
{
particles_->total_ghost_particles_ = 0;
}
//=================================================================================================//
Vecd SpringDamperConstraintParticleWise::getAcceleration(Vecd& disp, Real mass)
{
Vecd SpringDamperConstraintParticleWise::getSpringForce(size_t index_i, Vecd& disp)
{
Vecd spring_force(0);
for(int i = 0; i < disp.size(); i++)
{
spring_force[i] = -stiffness_[i] * disp[i] / mass;
}
spring_force[i] = -stiffness_[i] * disp[i];
}
return spring_force;
}
//=================================================================================================//
Vecd SpringDamperConstraintParticleWise::getDampingForce(size_t index_i, Real mass)
Vecd SpringDamperConstraintParticleWise::getDampingForce(size_t index_i)
{
Vecd damping_force(0);
for(int i = 0; i < vel_n_[index_i].size(); i++)
{
damping_force[i] = -stiffness_[i] * damping_ratio_ * vel_n_[index_i][i] / mass;
damping_force[i] = -damping_coeff_[i] * vel_n_[index_i][i];
}
return damping_force;
}
//=================================================================================================//
void SpringDamperConstraintParticleWise::Update(size_t index_i, Real dt)
{
Vecd disp_from_0 = pos_n_[index_i] - pos_0_[index_i];
dvel_dt_prior_[index_i] += getAcceleration(disp_from_0, mass_[index_i]);
dvel_dt_prior_[index_i] += getDampingForce(index_i, mass_[index_i]);
dvel_dt_prior_[index_i] += getSpringForce(index_i, pos_n_[index_i] - pos_0_[index_i]);
dvel_dt_prior_[index_i] += getDampingForce(index_i);
}
//=================================================================================================//
AccelerationForBodyPartInBoundingBox::
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22 changes: 8 additions & 14 deletions SPHINXsys/src/shared/particle_dynamics/solid_dynamics/solid_dynamics.h
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Expand Up @@ -296,23 +296,23 @@ namespace SPH
* @brief Exerts spring force and damping force in the form of acceleration to each particle.
* The spring force is calculated based on the difference from the particle's initial position.
* The damping force is calculated based on the particle's current velocity.
* Only for 3D applications
*/
class SpringDamperConstraintParticleWise
: public ParticleDynamicsSimple, public SolidDataSimple
{
public:
SpringDamperConstraintParticleWise(SolidBody* body, Vecd stiffness, Real damping_ratio = 0.01);
virtual ~SpringDamperConstraintParticleWise() {};
SpringDamperConstraintParticleWise(SolidBody* body, Vecd stiffness, Real damping_ratio = 0.05);
~SpringDamperConstraintParticleWise();
protected:
StdLargeVec<Real>& mass_;
Real total_mass_;
StdLargeVec<Vecd>& pos_n_,& pos_0_,& vel_n_,& dvel_dt_prior_;
Vecd stiffness_;
// damping component parallel to the spring force component
// damping coefficient = stiffness_ * damping_ratio_
Real damping_ratio_;
Vecd damping_coeff_; // damping component parallel to the spring force component

virtual void setupDynamics(Real dt = 0.0) override;
virtual Vecd getAcceleration(Vecd& disp, Real mass);
virtual Vecd getDampingForce(size_t index_i, Real mass);
virtual Vecd getSpringForce(size_t index_i, Vecd& disp);
virtual Vecd getDampingForce(size_t index_i);
virtual void Update(size_t index_i, Real dt = 0.0) override;
};
/**
Expand Down Expand Up @@ -389,12 +389,6 @@ namespace SPH
Real ReduceFunction(size_t index_i, Real dt = 0.0) override;
};

/**
* @function getSmallestTimeStepAmongSolidBodies
* @brief computing smallest time step to use in a simulation
*/
Real getSmallestTimeStepAmongSolidBodies(SPHBodyVector solid_bodies);

/**
* @class DeformationGradientTensorBySummation
* @brief computing deformation gradient tensor by summation
Expand Down