chaos-polymtl · blaisb · Jul 21, 2024 · Jul 20, 2024 · Jul 20, 2024
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -3,6 +3,12 @@
 All notable changes to the Lethe project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
+## [Master] - 2024-07-20
+
+### Fixed
+
+- MINOR The ratio of the critical Rayleigh time step was wrong in CFD-DEM and was modified as done in DEM. [#1203](https://github.com/chaos-polymtl/lethe/pull/1203)
+
 ## [Master] - 2024-07-14
 
 ### Added

diff --git a/applications_tests/lethe-fluid-particles/adaptive_sparse_contacts.mpirun=1.output b/applications_tests/lethe-fluid-particles/adaptive_sparse_contacts.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 2.34951% of Rayleigh time step
+DEM time-step is 2.61468% of Rayleigh time step
 Reading DEM checkpoint 
 Finished reading DEM checkpoint 
 350 particles are in the simulation 

diff --git a/applications_tests/lethe-fluid-particles/conserve_phase_volumes.mpirun=1.output b/applications_tests/lethe-fluid-particles/conserve_phase_volumes.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 2.186842813% of Rayleigh time step
+DEM time-step is 2.433653979% of Rayleigh time step
 Reading DEM checkpoint 
 Finished reading DEM checkpoint 
 10000 particles are in the simulation 

diff --git a/applications_tests/lethe-fluid-particles/dynamic_contact_search.mpirun=1.output b/applications_tests/lethe-fluid-particles/dynamic_contact_search.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 16.41771423% of Rayleigh time step
+DEM time-step is 18.27064813% of Rayleigh time step
 Reading DEM checkpoint 
 Finished reading DEM checkpoint 
 1 particles are in the simulation 

diff --git a/applications_tests/lethe-fluid-particles/liquid_fluidized_bed.mpirun=1.output b/applications_tests/lethe-fluid-particles/liquid_fluidized_bed.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 2.186842813% of Rayleigh time step
+DEM time-step is 2.433653979% of Rayleigh time step
 Reading DEM checkpoint 
 Finished reading DEM checkpoint 
 10000 particles are in the simulation 

diff --git a/applications_tests/lethe-fluid-particles/particle_sedimentation.mpirun=1.output b/applications_tests/lethe-fluid-particles/particle_sedimentation.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 16.41771423% of Rayleigh time step
+DEM time-step is 18.27064813% of Rayleigh time step
 Reading DEM checkpoint 
 Finished reading DEM checkpoint 
 1 particles are in the simulation 

diff --git a/applications_tests/lethe-fluid-particles/periodic_particles_qcm.mpirun=1.output b/applications_tests/lethe-fluid-particles/periodic_particles_qcm.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 4.74073% of Rayleigh time step
+DEM time-step is 5.13612% of Rayleigh time step
 Reading DEM checkpoint 
 Finished reading DEM checkpoint 
 2 particles are in the simulation 

diff --git a/applications_tests/lethe-fluid-particles/restart-gas-solid-fluidized-bed.mpirun=2.output b/applications_tests/lethe-fluid-particles/restart-gas-solid-fluidized-bed.mpirun=2.output
@@ -1,5 +1,5 @@
 Running on 2 MPI rank(s)...
-DEM time-step is 3.28354% of Rayleigh time step
+DEM time-step is 3.65413% of Rayleigh time step
    Number of active cells:       40
    Number of degrees of freedom: 656
    Volume of triangulation:      0.00108

diff --git a/applications_tests/lethe-fluid-particles/restart_particle_sedimentation.mpirun=1.output b/applications_tests/lethe-fluid-particles/restart_particle_sedimentation.mpirun=1.output
@@ -1,5 +1,5 @@
 Running on 1 MPI rank(s)...
-DEM time-step is 16.41771423% of Rayleigh time step
+DEM time-step is 18.27064813% of Rayleigh time step
    Number of active cells:       25
    Number of degrees of freedom: 192
    Volume of triangulation:      0.001

diff --git a/source/fem-dem/cfd_dem_coupling.cc b/source/fem-dem/cfd_dem_coupling.cc
@@ -1504,27 +1504,26 @@ CFDDEMSolver<dim>::dem_setup_contact_parameters()
   dem_time_step =
     this->simulation_control->get_time_step() / coupling_frequency;
 
-  double rayleigh_time_step = 0;
-
-  for (unsigned int i = 0;
-       i < dem_parameters.lagrangian_physical_properties.particle_type_number;
-       ++i)
-    rayleigh_time_step = std::max(
-      M_PI_2 *
-        dem_parameters.lagrangian_physical_properties
-          .particle_average_diameter[i] *
-        sqrt(2 *
-             dem_parameters.lagrangian_physical_properties.density_particle[i] *
-             (2 + dem_parameters.lagrangian_physical_properties
-                    .poisson_ratio_particle[i]) *
-             (1 - dem_parameters.lagrangian_physical_properties
-                    .poisson_ratio_particle[i]) /
-             dem_parameters.lagrangian_physical_properties
-               .youngs_modulus_particle[i]) /
-        (0.1631 * dem_parameters.lagrangian_physical_properties
-                    .poisson_ratio_particle[i] +
-         0.8766),
-      rayleigh_time_step);
+  double rayleigh_time_step = 1. / DBL_MIN;
+
+  Parameters::Lagrangian::LagrangianPhysicalProperties &physical_properties =
+    dem_parameters.lagrangian_physical_properties;
+
+  for (unsigned int i = 0; i < physical_properties.particle_type_number; ++i)
+    {
+      double shear_modulus =
+        physical_properties.youngs_modulus_particle[i] /
+        (2.0 * (1.0 + physical_properties.poisson_ratio_particle[i]));
+
+      double min_diameter =
+        size_distribution_object_container.at(i)->find_min_diameter();
+
+      rayleigh_time_step = std::min(
+        M_PI_2 * min_diameter *
+          sqrt(physical_properties.density_particle[i] / shear_modulus) /
+          (0.1631 * physical_properties.poisson_ratio_particle[i] + 0.8766),
+        rayleigh_time_step);
+    }
 
   const double time_step_rayleigh_ratio = dem_time_step / rayleigh_time_step;
   this->pcout << "DEM time-step is " << time_step_rayleigh_ratio * 100