Example 17 : Rotating Drum With Lagrangian Post Processing

A three-dimensional discrete element method simulation of rotating drum (cylinder) is performed in this example. The cylinder rotates around its axis, with rotational speed of 11.6 rad/s. Total simulation time is equal to 10 s, while time-step, log frequency and output frequency are set equal to 0.000001, 1000 and 1000, respectively:

# --------------------------------------------------
# Simulation and IO Control
#---------------------------------------------------
subsection simulation control
  set time step                 			 = 1e-6
  set time end       					 = 10
  set log frequency				         = 1000
  set output frequency            			 = 1000
end

In the model parameters section, particle-particle and particle-wall broad and fine search frequencies are defined. We also define the particle contact search size (neighborhood threshold), contact forces and integration methods. The contact detection method is dynamic, and it needs dynamic contact search size coefficient (a safety factor for dynamic contact search)

# --------------------------------------------------
# Model parameters
#---------------------------------------------------
subsection model parameters
  set contact detection method 		   		 = dynamic
  set dynamic contact search size coefficient	 	 = 0.8
  set neighborhood threshold				 = 1.3
  set load balance method				 = dynamic
  set load balance threshold				 = 0.5
  set dynamic load balance check frequency		 = 10000
  set particle particle contact force method             = pp_nonlinear
  set particle wall contact force method                 = pw_nonlinear
  set integration method				 = velocity_verlet
end

In the physical properties section, the physical properties of particles and walls, including diameter and density of particles, Young's modulus, Poisson's ratios, restitution coefficients, friction and rolling frictions of particle and wall are chosen. The gravitational acceleration is also set in this section. Diameter of particles in this example is 3 mm. Total number of particles in this example is 226080.

#---------------------------------------------------
# Physical Properties
#---------------------------------------------------
subsection physical properties
    set gx            		 			= 0.0
    set gy            		 			= 0.0
    set gz            		 			= -9.81
    set number of particle types	                = 1
    	subsection particle type 0
		set size distribution type		= uniform
    		set diameter            	 	= 0.003
    		set number              		= 226080
    		set density particles  	 		= 2500
    		set young modulus particles         	= 100000000
    		set poisson ratio particles          	= 0.24
    		set restitution coefficient particles	= 0.97
    		set friction coefficient particles      = 0.3
    		set rolling friction particles         	= 0.01
	end
    set young modulus wall            			= 100000000
    set poisson ratio wall            			= 0.24
    set restitution coefficient wall           		= 0.85
    set friction coefficient wall         		= 0.35
    set rolling friction wall         	      	  	= 0.01
end

Next, we define the insertion properties, which are insertion method, inserted number of particles at each insertion step, insertion frequency, insertion domain and other information regarding the initial positions of particles inside the insertion domain.

#---------------------------------------------------
# Insertion Info
#---------------------------------------------------
subsection insertion info
    set insertion method				= non_uniform
    set inserted number of particles at each time step  = 75110
    set insertion frequency            		 	= 200000
    set insertion box minimum x            	 	= -0.175
    set insertion box minimum y            	        = -0.07
    set insertion box minimum z            	        = -0.085
    set insertion box maximum x            	        = 0.175
    set insertion box maximum y           	 	= 0.07
    set insertion box maximum z            	        = 0.085
    set insertion distance threshold			= 1.575
    set insertion random number range			= 0.05
    set insertion random number seed			= 19
end

The triangulation information, which defines the geometry of the simulated system are defined. The radius of the drum is 0.12 m, and its length is 0.18 m.

#---------------------------------------------------
# Mesh
#---------------------------------------------------
subsection mesh
    set type                 				= dealii
    set grid type      	     				= cylinder
    set grid arguments       				= 0.12:0.18
    set initial refinement   				= 4
end

The rotational motion of the drum is defined here. The id of rotating boundary is 4, the boundary condition type is rotational, and its rotational speed is 11.6 rad/s. The vector of rotation (1,0,0) should be specified separately.

#---------------------------------------------------
# Boundary Condition
#---------------------------------------------------
subsection DEM boundary conditions
  set number of boundary conditions         		= 1
    subsection boundary condition 0
	set boundary id					= 4
        set type              				= rotational
	set rotational speed				= 11.6
	set rotational vector x				= 1
	set rotational vector y				= 0
	set rotational vector z				= 0
    end
end

In the Lagrangian post-processing section, we define the post-processing parameters. In this example, we calculate the particles' average velocity and granular temperature in each triangulation cell. initial step and end step show the initial and end steps of the Lagrangian post-processing.output frequency controls the writing frequency, and the output names are defined using particles velocity output name and granular temperature output name for average velocity and granular temperature, respectively.

#---------------------------------------------------
# Lagrangian post-processing
#---------------------------------------------------
subsection post-processing
    set Lagrangian post processing			= true
    set calculate particles average velocity            = true
    set calculate granular temperature			= true
    set initial step            			= 8500000
    set end step       					= 9500000
    set output frequency				= 1000
    set particles velocity output name   		= average_velocity
    set granular temperature output name		= granular_temperature
end

This example should be solved using dem_3d solver.