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changed damp_type to be a mdr damping coefficent

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This commit is contained in:
William Zunker
2025-04-15 13:55:38 -04:00
parent 585565edb9
commit 0c29a0a0c9
7 changed files with 22 additions and 23 deletions
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16
doc/src/pair_granular.rst
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@ -44,7 +44,7 @@ Examples
pair_coeff * * hertz 1000.0 50.0 tangential mindlin 1000.0 1.0 0.4 heat area 0.1
pair_style granular
pair_coeff * * mdr 5e6 0.4 1.9e5 2.0 0.5 0.5 tangential linear_history 940.0 0.0 0.7 rolling sds 2.7e5 0.0 0.6 damping mdr 1
pair_coeff * * mdr 5e6 0.4 1.9e5 2.0 0.5 0.5 tangential linear_history 940.0 1.0 0.7 rolling sds 2.7e5 0.0 0.6 damping mdr 1
Description
"""""""""""
@ -89,7 +89,7 @@ and their required arguments are:
4. *dmt* : E, :math:`\eta_{n0}` (or :math:`e`), :math:`\nu`, :math:`\gamma`
5. *jkr* : E, :math:`\eta_{n0}` (or :math:`e`), :math:`\nu`, :math:`\gamma`
6. *mdr* : :math:`E`, :math:`\nu`, :math:`Y`, :math:`\Delta\gamma`,
:math:`\psi_b`, :math:`\eta_{n0}`, :math:`d_{type}`
:math:`\psi_b`, :math:`\eta_{n0}`
Here, :math:`k_n` is spring stiffness (with units that depend on model
choice, see below); :math:`\eta_{n0}` is a damping prefactor (or, in its
@ -206,9 +206,6 @@ The model requires the following inputs:
6. *Damping coefficent* :math:`\eta_{n0} \ge 0` : The damping coefficient
is a tunable parameter that controls damping in the normal direction.
7. *Damping type* :math:`d_{type} =` 1 or 2 : The damping type specfies the
damping model defined for the *mdr* damping class described below.
.. note::
The values for :math:`E`, :math:`\nu`, :math:`Y`, and :math:`\Delta\gamma` (i.e.,
@ -263,7 +260,7 @@ The *mdr* model currently only supports *fix wall/gran/region*, not
any *fix wall/gran/region* commands must also use the *mdr* model.
Additionally, the following *mdr* inputs must match between the
*pair_style* and *fix wall/gran/region* definitions: :math:`E`,
:math:`\nu`, :math:`Y`, :math:`\psi_b`, and :math:`e`. The exception
:math:`\nu`, :math:`Y`, :math:`\psi_b`, and :math:`\eta_{n0}`. The exception
is :math:`\Delta\gamma`, which may vary, permitting different
adhesive behaviors between particle-particle and particle-wall interactions.
@ -329,7 +326,7 @@ for the damping model currently supported are:
3. *viscoelastic*
4. *tsuji*
5. *coeff_restitution*
6. *mdr*
6. *mdr* (class) : :math:`d_{type}`
If the *damping* keyword is not specified, the *viscoelastic* model is
used by default.
@ -420,9 +417,8 @@ restitution for both monodisperse and polydisperse particle pairs. This damping
model is not compatible with cohesive normal models such as *JKR* or *DMT*.
The *mdr* damping class contains multiple damping models that can be toggled between
by specifying different integer values for the :math:`d_{type}` parameter in the *mdr*
normal model. This damping option is therefore only compatible with the normal *mdr*
contact model.
by specifying different integer values for the :math:`d_{type}` input parameter. This
damping option is only compatible with the normal *mdr* contact model.
Setting :math:`d_{type} = 1` is the suggested damping option. This specifies a damping
model that takes into account the contact stiffness :math:`k_{mdr}` calulated

6
examples/granular/in.tableting.200
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@ -50,8 +50,8 @@ variable mu_roll equal 0.6
variable k_roll equal 2.25*${mu_roll}*${mu_roll}*${YoungsModulus}*${atomRadius}
variable gamma_roll equal 0.0
pair_coeff * * mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergy} ${psi_b} ${damp} ${damp_type} &
damping mdr &
pair_coeff * * mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergy} ${psi_b} ${damp} &
damping mdr ${damp_type} &
tangential linear_history ${kt} ${xgammat} ${mu_s} &
rolling sds ${k_roll} ${gamma_roll} ${mu_roll}
@ -60,7 +60,7 @@ pair_coeff * * mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEne
variable disp_upper equal 0.0
variable disp_lower equal 0.0
variable wall_contact_string string "granular mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergyWall} ${psi_b} ${damp} ${damp_type} damping mdr tangential linear_history ${kt_wall} ${xgammat} ${mu_s_wall} rolling sds ${k_roll} ${gamma_roll} ${mu_roll}"
variable wall_contact_string string "granular mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergyWall} ${psi_b} ${damp} damping mdr ${damp_type} tangential linear_history ${kt_wall} ${xgammat} ${mu_s_wall} rolling sds ${k_roll} ${gamma_roll} ${mu_roll}"
variable dieHeight2 equal 2*${dieHeight}

6
examples/granular/in.triaxial.compaction.12
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@ -38,8 +38,8 @@ variable kt equal 2/7*${YoungsModulus}*${atomRadius}
variable xgammat equal 0.0
variable mu_s equal 0.5
pair_coeff * * mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergy} ${psi_b} ${damp} ${damp_type} &
damping mdr &
pair_coeff * * mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergy} ${psi_b} ${damp} &
damping mdr ${damp_type} &
tangential linear_history ${kt} ${xgammat} ${mu_s}
######################################### ADD IN PLANES ################################################
@ -57,7 +57,7 @@ region plane_xz_neg plane 0 -${halfBoxWidth} 0 0 1 0 side in move NULL v_plane_d
region plane_xy_pos plane 0 0 ${halfBoxWidth} 0 0 -1 side in move NULL NULL v_plane_disp_neg units box
region plane_xy_neg plane 0 0 -${halfBoxWidth} 0 0 1 side in move NULL NULL v_plane_disp units box
variable wall_contact_string string "granular mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergy} ${psi_b} ${damp} ${damp_type} damping mdr tangential linear_history ${kt} ${xgammat} ${mu_s} "
variable wall_contact_string string "granular mdr ${YoungsModulus} ${PoissonsRatio} ${YieldStress} ${SurfaceEnergy} ${psi_b} ${damp} damping mdr ${damp_type} tangential linear_history ${kt} ${xgammat} ${mu_s} "
fix plane_yz_pos all wall/gran/region ${wall_contact_string} region plane_yz_pos contacts
fix plane_yz_neg all wall/gran/region ${wall_contact_string} region plane_yz_neg contacts

8
src/GRANULAR/gran_sub_mod_damping.cpp
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@ -190,6 +190,13 @@ void GranSubModDampingCoeffRestitution::init()
GranSubModDampingMDR::GranSubModDampingMDR(GranularModel *gm, LAMMPS *lmp) :
GranSubModDamping(gm, lmp)
{
num_coeffs = 1;
}
void GranSubModDampingMDR::coeffs_to_local()
{
damp_type = coeffs[0]; // damping type 1 = mdr stiffness or 2 = velocity
if (damp_type != 1 && damp_type != 2) error->all(FLERR, "Illegal MDR normal model, damping type must an integer equal to 1 or 2");
}
/* ---------------------------------------------------------------------- */
@ -200,7 +207,6 @@ void GranSubModDampingMDR::init()
error->all(FLERR, "Damping mdr can only be used with mdr normal model");
damp = gm->normal_model->get_damp();
damp_type = gm->normal_model->get_damp_type();
}
/* ---------------------------------------------------------------------- */

3
src/GRANULAR/gran_sub_mod_damping.h
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@ -42,7 +42,7 @@ namespace Granular_NS {
protected:
double damp_prefactor;
double damp;
int damp_type;
int damp_type; // damping type is only used by normal mdr model
};
/* ---------------------------------------------------------------------- */
@ -99,6 +99,7 @@ namespace Granular_NS {
class GranSubModDampingMDR : public GranSubModDamping {
public:
GranSubModDampingMDR(class GranularModel *, class LAMMPS *);
void coeffs_to_local() override;
void init() override;
double calculate_forces() override;
};

4
src/GRANULAR/gran_sub_mod_normal.cpp
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@ -441,7 +441,7 @@ GranSubModNormalMDR::GranSubModNormalMDR(GranularModel *gm, LAMMPS *lmp) :
{
if (lmp->citeme) lmp->citeme->add(cite_mdr);
num_coeffs = 7;
num_coeffs = 6;
contact_radius_flag = 1;
size_history = 27;
nsvector = 1;
@ -474,7 +474,6 @@ void GranSubModNormalMDR::coeffs_to_local()
gamma = coeffs[3]; // effective surface energy
psi_b = coeffs[4]; // bulk response trigger based on ratio of remaining free area: A_{free}/A_{total}
damp = coeffs[5]; // coefficent of restitution
damp_type = coeffs[6]; // damping type 1 = mdr or 2 = velocity
if (E <= 0.0) error->all(FLERR, "Illegal MDR normal model, Young's modulus must be greater than 0");
if (nu < 0.0 || nu > 0.5) error->all(FLERR, "Illegal MDR normal model, Poisson's ratio must be between 0 and 0.5");
@ -482,7 +481,6 @@ void GranSubModNormalMDR::coeffs_to_local()
if (gamma < 0.0) error->all(FLERR, "Illegal MDR normal model, effective surface energy must be greater than or equal to 0");
if (psi_b < 0.0 || psi_b > 1.0) error->all(FLERR, "Illegal MDR normal model, psi_b must be between 0 and 1.0");
if (damp < 0.0) error->all(FLERR, "Illegal MDR normal model, damping coefficent must be greater than or equal to 0");
if (damp_type != 1 && damp_type != 2) error->all(FLERR, "Illegal MDR normal model, damping type must an integer equal to 1 or 2");
G = E / (2.0 * (1.0 + nu)); // shear modulus
kappa = E / (3.0 * (1.0 - 2.0 * nu)); // bulk modulus

2
src/GRANULAR/gran_sub_mod_normal.h
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@ -41,7 +41,6 @@ namespace Granular_NS {
int get_cohesive_flag() const { return cohesive_flag; }
double get_damp() const { return damp; }
double get_damp_type() const { return damp_type; }
double get_emod() const { return Emod; }
double get_fncrit() const { return Fncrit; }
int get_material_properties() const { return material_properties; }
@ -52,7 +51,6 @@ namespace Granular_NS {
protected:
double damp; // argument historically needed by damping
// typically (but not always) equals eta_n0
int damp_type; // damping type is only used by normal mdr model
double Emod, poiss;
double Fncrit;
int material_properties, cohesive_flag;