Particle Agglomeration Model Reference

The Particle Agglomeration model introduces attractive inter-particle forces to the particle system. When the bond formation criteron is met, the Particle Agglomeration model acts to form clusters from particles that collide.

The Particle Agglomeration model uses the concept of a massless bar connecting a pair of spherical particles or a spherical particle bonded to a wall. The bar can transmit force and torque between particles and it is also subject to cracking under load.

The inter-particle force consists of the traditional grain-grain interaction (represented by the specified contact model, Hertz-Mindlin, Linear Spring, or Walton-Braun) and the parallel bond forces. When the Particle Agglomeration model is selected, the Simple Failure and Constant Rate Damage models become available. If either of these models is selected and determines that the bond breaks, the particles or particle and wall separate. Thereafter, the contact force model (such as Hertz Mindlin or Linear Spring) determines the particle-particle interaction upon collision.

Potential applications of this particular model include:

Pharmaceutical and biomedical—the tableting process, the breakage of particles, and deforming cells in blood flow
Nuclear—checking the effects of certain obstructions to the flow of nuclear waste material; heat transfer studies
Chemical and metallurgical—particle breakage and dust formation during handling of solid raw materials; also phase change
Shipping—ice breakup, specifically ice breakup upon collision with dams or shorelines, as well as upon collision with shipping vessels
Petroleum—hydrates and asphaltenes. This application can include specifying how particles bond with each other based on various parameters.


Theory	See Particle Bonding Model.
Provided By	[physics continuum] > Models > Multiphase Interaction > Phase Interactions > Phase Interaction [n] > Models > Optional Models
Example Node Path	Continua > Physics 1 > Models > Multiphase Interaction > Phase Interactions > Phase Interaction 1 > Models > Particle Agglomeration
Requires	Under Lagrangian Multiphase, select Particle Type: DEM Particles, Particle Shape: Spherical Particles or Composite Particles Under Multiphase Interaction: Select Phase Interaction Topology: DEM Phase Interaction if it has not been automatically selected. Set the First Phase and Second Phase properties of DEM Phase Interaction to DEM Lagrangian phases. Select Optional Models: Hertz Mindlin, Walton Braun, or Linear Spring
Properties	Key property is: Bond Radius Multiplier. See Particle Agglomeration Properties.
Activates	Model Controls (child nodes)	Bond Formation. See Controlling Bond Formation. Bond Stiffness. See Controlling Bond Stiffness.
	Field Functions	Bond State

Particle Agglomeration Properties

Bond Radius Multiplier: Scales the radius of the particle bond. The default multiplier is 1.

Controlling Bond Formation

Method	Corresponding Method Node
User Defined Allows you to specify a user-defined bond formation criterion.	User Defined Bond Formation Criterion Specifies the conditions under which bonds between spherical DEM particles or between spherical DEM particles and a wall form, as an expression. For example, ${ContactTime} > 0.001.
Time Window When the simulation time is in the interval between these times, any particles that collide, or any particle that collides with a wall, establishes a parallel bond in addition to the regular contact force being calculated.	Time Window Bond Start Time Specifies the time at which the bonds begin to be created. The default is 0 s. Bond End Time Specifies the time at which the bond creation process stops. The default is 0 s.

Controlling Bond Stiffness

Method	Corresponding Method Node
User Defined	User Defined Allows you to set the properties of the Normal Stiffness and Stiffness Ratio nodes: Normal Stiffness Allows you to set the normal stiffness of the bond. If the bond tangential stiffness is different from the normal stiffness, you can change the Stiffness Ratio (1.0 by default). Method Select from among standard profiles. Update option When set to Initialize only, normal stiffness remains the same as long as the bond lasts. When Initialize and update is selected, normal stiffness is updated every sub-step according to the profile selected under Method. Stiffness Ratio The ratio of tangential to normal stiffness. The default value is 1.0
Particle Material Based	Particle Material Based Value is set automatically according to the material used in the particle. See the treatment of bond stiffness parameters $k_{n}$ and $k_{s}$ in Particle Clustering and Breakup.

Method

Corresponding Method Node

User Defined

User Defined

Allows you to set the properties of the Normal Stiffness and Stiffness Ratio nodes:

Normal Stiffness

Allows you to set the normal stiffness of the bond. If the bond tangential stiffness is different from the normal stiffness, you can change the Stiffness Ratio (1.0 by default).

Method: Select from among standard profiles.
Update option: When set to Initialize only, normal stiffness remains the same as long as the bond lasts. When Initialize and update is selected, normal stiffness is updated every sub-step according to the profile selected under Method.

Stiffness Ratio

The ratio of tangential to normal stiffness. The default value is 1.0

Particle Material Based

Particle Material Based: Value is set automatically according to the material used in the particle. See the treatment of bond stiffness parameters $k_{n}$ and $k_{s}$ in Particle Clustering and Breakup.