working on adding damping types to mdr damping

src/GRANULAR/gran_sub_mod_damping.cpp

@@ -45,6 +45,11 @@ GranSubModDamping::GranSubModDamping(GranularModel *gm, LAMMPS *lmp) : GranSubMo
 void GranSubModDamping::init()
 {
   damp = gm->normal_model->get_damp();
+  if (gm->normal_model->name == "mdr") {
+    if (gm->tangential_model->name != "mdr")
+      error->all(FLERR, "Only damping mdr may be used with the mdr normal model");
+    damp_type = gm->normal_model->get_damp_type();
+  }
 }
 
 /* ----------------------------------------------------------------------
@@ -77,17 +82,7 @@ GranSubModDampingVelocity::GranSubModDampingVelocity(GranularModel *gm, LAMMPS *
 
 double GranSubModDampingVelocity::calculate_forces()
 {
-  if (gm->normal_model->name == "mdr") {
-    using namespace Granular_MDR_NS;
-    double *history = & gm->history[gm->normal_model->history_index];
-    if (history[DAMP_SCALE] == 0.0) {
-      damp_prefactor == 0.0;
-    } else {
-      damp_prefactor = damp;
-    }
-  } else {
-    damp_prefactor = damp;
-  }
+  damp_prefactor = damp;
   return -damp_prefactor * gm->vnnr;
 }
 
@@ -209,6 +204,14 @@ double GranSubModDampingMDR::calculate_forces()
 {
   using namespace Granular_MDR_NS;
   double *history = & gm->history[gm->normal_model->history_index];
-  damp_prefactor = damp * history[DAMP_SCALE];
+  if (damp_type == 1) {
+    damp_prefactor = damp * history[DAMP_SCALE];
+  } else if (damp_type == 2) {
+    if (history[DAMP_SCALE] == 0.0) {
+      damp_prefactor == 0.0;
+    } else {
+      damp_prefactor = damp;
+    }
+  }
   return -damp_prefactor * gm->vnnr;
 }

src/GRANULAR/gran_sub_mod_damping.h

@@ -42,6 +42,7 @@ namespace Granular_NS {
    protected:
     double damp_prefactor;
     double damp;
+    int damp_type;
   };
 
   /* ---------------------------------------------------------------------- */

src/GRANULAR/gran_sub_mod_normal.cpp

@@ -441,7 +441,7 @@ GranSubModNormalMDR::GranSubModNormalMDR(GranularModel *gm, LAMMPS *lmp) :
 {
   if (lmp->citeme) lmp->citeme->add(cite_mdr);
 
-  num_coeffs = 6;
+  num_coeffs = 7;
   contact_radius_flag = 1;
   size_history = 27;
   nsvector = 1;
@@ -468,12 +468,13 @@ GranSubModNormalMDR::~GranSubModNormalMDR()
 
 void GranSubModNormalMDR::coeffs_to_local()
 {
-  E = coeffs[0];      // Young's modulus
-  nu = coeffs[1];     // Poisson's ratio
-  Y = coeffs[2];      // yield stress
-  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
+  E = coeffs[0];         // Young's modulus
+  nu = coeffs[1];        // Poisson's ratio
+  Y = coeffs[2];         // yield stress
+  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");
@@ -481,6 +482,7 @@ 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 (mdr) or 2 (velocity)");
 
   G = E / (2.0 * (1.0 + nu));            // shear modulus
   kappa = E / (3.0 * (1.0 - 2.0 * nu));  // bulk modulus

src/GRANULAR/gran_sub_mod_normal.h

@@ -41,6 +41,7 @@ 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; }
@@ -51,6 +52,7 @@ 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;