/usr/include/liggghts/normal_model_hertz.h is in libliggghts-dev 3.7.0+repack1-1.
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This is the
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╚══════╝╚═╝ ╚═════╝ ╚═════╝ ╚═════╝ ╚═╝ ╚═╝ ╚═╝ ╚══════╝®
DEM simulation engine, released by
DCS Computing Gmbh, Linz, Austria
http://www.dcs-computing.com, office@dcs-computing.com
LIGGGHTS® is part of CFDEM®project:
http://www.liggghts.com | http://www.cfdem.com
Core developer and main author:
Christoph Kloss, christoph.kloss@dcs-computing.com
LIGGGHTS® is open-source, distributed under the terms of the GNU Public
License, version 2 or later. It is distributed in the hope that it will
be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. You should have
received a copy of the GNU General Public License along with LIGGGHTS®.
If not, see http://www.gnu.org/licenses . See also top-level README
and LICENSE files.
LIGGGHTS® and CFDEM® are registered trade marks of DCS Computing GmbH,
the producer of the LIGGGHTS® software and the CFDEM®coupling software
See http://www.cfdem.com/terms-trademark-policy for details.
-------------------------------------------------------------------------
Contributing author and copyright for this file:
Christoph Kloss (DCS Computing GmbH, Linz)
Christoph Kloss (JKU Linz)
Richard Berger (JKU Linz)
Copyright 2012- DCS Computing GmbH, Linz
Copyright 2009-2012 JKU Linz
------------------------------------------------------------------------- */
#ifdef NORMAL_MODEL
NORMAL_MODEL(HERTZ,hertz,3)
#else
#ifndef NORMAL_MODEL_HERTZ_H_
#define NORMAL_MODEL_HERTZ_H_
#include "global_properties.h"
#include "fix_property_atom.h"
#include <math.h>
#include "normal_model_base.h"
#include "fix_mesh_surface.h"
namespace LIGGGHTS {
namespace ContactModels
{
class ContactModelBase;
template<>
class NormalModel<HERTZ> : public NormalModelBase
{
public:
NormalModel(LAMMPS * lmp, IContactHistorySetup* hsetup, class ContactModelBase *c) :
NormalModelBase(lmp, hsetup, c),
Yeff(NULL),
Geff(NULL),
betaeff(NULL),
limitForce(false),
displayedSettings(false),
heating(false),
heating_track(false),
elastic_potential_offset_(-1),
elasticpotflag_(false),
fix_dissipated_(NULL),
dissipatedflag_(false),
overlap_offset_(0.0),
disable_when_bonded_(false),
bond_history_offset_(-1),
dissipation_history_offset_(-1),
cmb(c)
{
}
void registerSettings(Settings & settings)
{
settings.registerOnOff("tangential_damping", tangential_damping, true);
settings.registerOnOff("limitForce", limitForce);
settings.registerOnOff("heating_normal_hertz",heating,false);
settings.registerOnOff("heating_tracking",heating_track,false);
settings.registerOnOff("computeElasticPotential", elasticpotflag_, false);
settings.registerOnOff("computeDissipatedEnergy", dissipatedflag_, false);
settings.registerOnOff("disableNormalWhenBonded", disable_when_bonded_, false);
//TODO error->one(FLERR,"TODO here also check if right surface model used");
}
inline void postSettings(IContactHistorySetup * hsetup, ContactModelBase *cmb)
{
if (elasticpotflag_)
{
elastic_potential_offset_ = cmb->get_history_offset("elastic_potential_normal");
if (elastic_potential_offset_ == -1)
{
elastic_potential_offset_ = hsetup->add_history_value("elastic_potential_normal", "0");
hsetup->add_history_value("elastic_force_normal_0", "1");
hsetup->add_history_value("elastic_force_normal_1", "1");
hsetup->add_history_value("elastic_force_normal_2", "1");
if (cmb->is_wall())
hsetup->add_history_value("elastic_potential_wall", "0");
cmb->add_history_offset("elastic_potential_normal", elastic_potential_offset_);
}
}
if (dissipatedflag_)
{
if (cmb->is_wall())
{
fix_dissipated_ = static_cast<FixPropertyAtom*>(modify->find_fix_property("dissipated_energy_wall", "property/atom", "vector", 0, 0, "dissipated energy"));
dissipation_history_offset_ = cmb->get_history_offset("dissipation_force");
if (!dissipation_history_offset_)
error->one(FLERR, "Internal error: Could not find dissipation history offset");
}
else
fix_dissipated_ = static_cast<FixPropertyAtom*>(modify->find_fix_property("dissipated_energy", "property/atom", "vector", 0, 0, "dissipated energy"));
if (!fix_dissipated_)
error->one(FLERR, "Surface model has not registered dissipated_energy fix");
}
if (disable_when_bonded_)
{
bond_history_offset_ = cmb->get_history_offset("bond_contactflag");
if (bond_history_offset_ < 0)
error->one(FLERR, "Could not find bond history offset");
overlap_offset_ = hsetup->add_history_value("overlap_offset", "0");
}
}
void connectToProperties(PropertyRegistry & registry)
{
registry.registerProperty("Yeff", &MODEL_PARAMS::createYeff,"model hertz");
registry.registerProperty("Geff", &MODEL_PARAMS::createGeff,"model hertz");
registry.registerProperty("betaeff", &MODEL_PARAMS::createBetaEff,"model hertz");
registry.connect("Yeff", Yeff,"model hertz");
registry.connect("Geff", Geff,"model hertz");
registry.connect("betaeff", betaeff,"model hertz");
// enlarge contact distance flag in case of elastic energy computation
// to ensure that surfaceClose is called after a contact
if (elasticpotflag_)
{
//set neighbor contact_distance_factor here
const char* neigharg[2];
neigharg[0] = "contact_distance_factor";
neigharg[1] = "1.01";
neighbor->modify_params(2,const_cast<char**>(neigharg));
}
}
// effective exponent for stress-strain relationship
inline double stressStrainExponent()
{
return 1.5;
}
void dissipateElasticPotential(SurfacesCloseData &scdata)
{
if (elasticpotflag_)
{
double * const elastic_energy = &scdata.contact_history[elastic_potential_offset_];
if (scdata.is_wall)
{
// we need to calculate half an integration step which was left over to ensure no energy loss, but only for the elastic energy. The dissipation part is handled in fix_wall_gran_base.h.
double delta[3];
scdata.fix_mesh->triMesh()->get_global_vel(delta);
vectorScalarMult3D(delta, update->dt);
// -= because force is in opposite direction
// no *dt as delta is v*dt of the contact position
elastic_energy[0] -= (delta[0]*(elastic_energy[1]) +
delta[1]*(elastic_energy[2]) +
delta[2]*(elastic_energy[3]))*0.5
// from previous half step
+ elastic_energy[4];
elastic_energy[4] = 0.0;
}
elastic_energy[1] = 0.0;
elastic_energy[2] = 0.0;
elastic_energy[3] = 0.0;
}
}
inline void surfacesIntersect(SurfacesIntersectData & sidata, ForceData & i_forces, ForceData & j_forces)
{
if (sidata.contact_flags) *sidata.contact_flags |= CONTACT_NORMAL_MODEL;
const bool update_history = sidata.computeflag && sidata.shearupdate;
const int itype = sidata.itype;
const int jtype = sidata.jtype;
const double radi = sidata.radi;
const double radj = sidata.radj;
double reff = sidata.is_wall ? radi : (radi*radj/(radi+radj));
#ifdef SUPERQUADRIC_ACTIVE_FLAG
if(sidata.is_non_spherical) {
if(sidata.is_wall)
reff = MathExtraLiggghtsNonspherical::get_effective_radius_wall(sidata, atom->roundness[sidata.i], error);
else
reff = MathExtraLiggghtsNonspherical::get_effective_radius(sidata, atom->roundness[sidata.i], atom->roundness[sidata.j], error);
}
#endif
const double meff=sidata.meff;
if(sidata.deltan < 0)
error->one(FLERR, "sidata.deltan < 0!");
const double sqrtval = sqrt(reff*sidata.deltan);
#ifdef LIGGGHTS_DEBUG
if(std::isnan(sqrtval))
error->one(FLERR, "sqrtval is NaN!");
#endif
if (disable_when_bonded_ && update_history && sidata.deltan < sidata.contact_history[overlap_offset_])
sidata.contact_history[overlap_offset_] = sidata.deltan;
const double deltan = disable_when_bonded_ ? fmax(sidata.deltan-sidata.contact_history[overlap_offset_], 0.0) : sidata.deltan;
const double Sn=2.*Yeff[itype][jtype]*sqrtval;
const double St=8.*Geff[itype][jtype]*sqrtval;
double kn=4./3.*Yeff[itype][jtype]*sqrtval;
double kt=St;
const double sqrtFiveOverSix = 0.91287092917527685576161630466800355658790782499663875;
const double gamman=-2.*sqrtFiveOverSix*betaeff[itype][jtype]*sqrt(Sn*meff);
const double gammat= tangential_damping ? -2.*sqrtFiveOverSix*betaeff[itype][jtype]*sqrt(St*meff) : 0.0;
if(!displayedSettings)
{
displayedSettings = true;
/*
if(limitForce)
if(0 == comm->me) fprintf(screen," NormalModel<HERTZ_STIFFNESS>: will limit normal force.\n");
*/
}
// convert Kn and Kt from pressure units to force/distance^2
kn /= force->nktv2p;
kt /= force->nktv2p;
const double Fn_damping = -gamman*sidata.vn;
const double Fn_contact = kn*deltan;
double Fn = Fn_damping + Fn_contact;
//limit force to avoid the artefact of negative repulsion force
if(limitForce && (Fn<0.0) )
{
Fn = 0.0;
}
sidata.Fn = Fn;
sidata.kn = kn;
sidata.kt = kt;
sidata.gamman = gamman;
sidata.gammat = gammat;
#ifdef NONSPHERICAL_ACTIVE_FLAG
double torque_i[3] = {0., 0., 0.};
double Fn_i[3] = { Fn * sidata.en[0], Fn * sidata.en[1], Fn * sidata.en[2]};
if(sidata.is_non_spherical) {
double xci[3];
vectorSubtract3D(sidata.contact_point, atom->x[sidata.i], xci);
vectorCross3D(xci, Fn_i, torque_i);
}
#endif
// apply normal force
if (!disable_when_bonded_ || sidata.contact_history[bond_history_offset_] < 0.5)
{
if(heating)
{
const double mj = sidata.is_wall ? sidata.mi : sidata.mj;
const double E_therm = fabs((-sidata.vn - update->dt*Fn*0.5*(1.0/sidata.mi + 1.0/mj))*Fn_damping);
sidata.P_diss += E_therm;
if(heating_track && sidata.is_wall)
cmb->tally_pw(E_therm ,sidata.i,jtype,0);
if(heating_track && !sidata.is_wall)
cmb->tally_pp(E_therm ,sidata.i,sidata.j,0);
}
// energy balance terms
if (update_history)
{
// compute increment in elastic potential
if (elasticpotflag_)
{
double * const elastic_energy = &sidata.contact_history[elastic_potential_offset_];
// correct for wall influence
double delta[3];
if (sidata.is_wall)
{
sidata.fix_mesh->triMesh()->get_global_vel(delta);
vectorScalarMult3D(delta, update->dt);
// -= because force is in opposite direction
// no *dt as delta is v*dt of the contact position
//printf("pela %e %e %e %e\n", update->get_cur_time()-update->dt, deb, -sidata.radj, deb-sidata.radj);
elastic_energy[0] -= (delta[0]*elastic_energy[1] +
delta[1]*elastic_energy[2] +
delta[2]*elastic_energy[3])*0.5
// from previous half step
+ elastic_energy[4];
elastic_energy[4] = -(delta[0]*Fn_contact*sidata.en[0] +
delta[1]*Fn_contact*sidata.en[1] +
delta[2]*Fn_contact*sidata.en[2])*0.5;
}
elastic_energy[1] = -Fn_contact*sidata.en[0];
elastic_energy[2] = -Fn_contact*sidata.en[1];
elastic_energy[3] = -Fn_contact*sidata.en[2];
}
// compute increment in dissipated energy
if (dissipatedflag_)
{
double * const * const dissipated = fix_dissipated_->array_atom;
double * const dissipated_i = dissipated[sidata.i];
double * const dissipated_j = dissipated[sidata.j];
const double F_diss = -Fn_damping;
dissipated_i[1] += sidata.en[0]*F_diss;
dissipated_i[2] += sidata.en[1]*F_diss;
dissipated_i[3] += sidata.en[2]*F_diss;
if (sidata.j < atom->nlocal && !sidata.is_wall)
{
dissipated_j[1] -= sidata.en[0]*F_diss;
dissipated_j[2] -= sidata.en[1]*F_diss;
dissipated_j[3] -= sidata.en[2]*F_diss;
}
else if (sidata.is_wall)
{
double * const diss_force = &sidata.contact_history[dissipation_history_offset_];
diss_force[0] -= sidata.en[0]*F_diss;
diss_force[1] -= sidata.en[1]*F_diss;
diss_force[2] -= sidata.en[2]*F_diss;
}
}
#ifdef NONSPHERICAL_ACTIVE_FLAG
if ((dissipatedflag_ || elasticpotflag_) && sidata.is_non_spherical)
error->one(FLERR,"Dissipation and elastic potential do not compute torque influence for nonspherical particles");
#endif
}
if(sidata.is_wall) {
const double Fn_ = Fn * sidata.area_ratio;
i_forces.delta_F[0] += Fn_ * sidata.en[0];
i_forces.delta_F[1] += Fn_ * sidata.en[1];
i_forces.delta_F[2] += Fn_ * sidata.en[2];
#ifdef NONSPHERICAL_ACTIVE_FLAG
if(sidata.is_non_spherical) {
//for non-spherical particles normal force can produce torque!
i_forces.delta_torque[0] += torque_i[0];
i_forces.delta_torque[1] += torque_i[1];
i_forces.delta_torque[2] += torque_i[2];
}
#endif
} else {
i_forces.delta_F[0] += sidata.Fn * sidata.en[0];
i_forces.delta_F[1] += sidata.Fn * sidata.en[1];
i_forces.delta_F[2] += sidata.Fn * sidata.en[2];
j_forces.delta_F[0] += -i_forces.delta_F[0];
j_forces.delta_F[1] += -i_forces.delta_F[1];
j_forces.delta_F[2] += -i_forces.delta_F[2];
#ifdef NONSPHERICAL_ACTIVE_FLAG
if(sidata.is_non_spherical) {
//for non-spherical particles normal force can produce torque!
double xcj[3], torque_j[3];
double Fn_j[3] = { -Fn_i[0], -Fn_i[1], -Fn_i[2]};
vectorSubtract3D(sidata.contact_point, atom->x[sidata.j], xcj);
vectorCross3D(xcj, Fn_j, torque_j);
i_forces.delta_torque[0] += torque_i[0];
i_forces.delta_torque[1] += torque_i[1];
i_forces.delta_torque[2] += torque_i[2];
j_forces.delta_torque[0] += torque_j[0];
j_forces.delta_torque[1] += torque_j[1];
j_forces.delta_torque[2] += torque_j[2];
}
#endif
}
}
else if (update_history)
{
sidata.contact_history[overlap_offset_] = sidata.deltan;
dissipateElasticPotential(sidata);
}
}
void surfacesClose(SurfacesCloseData &scdata, ForceData&, ForceData&)
{
if (scdata.contact_flags) *scdata.contact_flags |= CONTACT_NORMAL_MODEL;
dissipateElasticPotential(scdata);
}
void beginPass(SurfacesIntersectData&, ForceData&, ForceData&){}
void endPass(SurfacesIntersectData&, ForceData&, ForceData&){}
protected:
double ** Yeff;
double ** Geff;
double ** betaeff;
bool tangential_damping;
bool limitForce;
bool displayedSettings;
bool heating;
bool heating_track;
int elastic_potential_offset_;
bool elasticpotflag_;
FixPropertyAtom *fix_dissipated_;
bool dissipatedflag_;
int overlap_offset_;
bool disable_when_bonded_;
int bond_history_offset_;
int dissipation_history_offset_;
class ContactModelBase *cmb;
};
}
}
#endif
#endif
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