Attribute Definitions

The following tables provide detailed descriptions for Particle, Geometry, Contact, and Collision attributes.

Particle Attributes


Attribute	Description
Angular Velocity	Indicates the speed at which an object rotates.
Charge	Indicates the charge which is an electrical property of particles (such as electrons and protons) which causes them to attract and repel each other. A material with an excess of electrons has a negative charge; and a material with an absence of electrons (or an excess of protons) has a positive charge. Materials with a balanced number of electrons and protons are called 'neutral'. Positive and negative charges attract each other.
Compressive Force	Indicates the sum of the surface normal force magnitudes.
Coordination Number	Indicates the number of contacts that a particle has with the spheres of another particle at any given point in time. The following image of a 3-sphere particle shape represents four particles placed on top of each other. The base and top particles have a coordination number of 3, as each particle is in contact with 3 spheres of the middle particles. The middle two particles have a coordination number of 6 as they are in contact with 3 spheres of the particle above and 3 spheres of the particle. The Particle-Geometry contacts are not counted in the coordination number.
Diameter	Indicates the diameter of the particle (based on the largest X, Y, or Z component of the bounding box around the particle).
Distance	Indicates the distance between the center of a particle from a reference point or plane.
Electrostatic Force	Indicates the force of interaction between charged particles, measured in Newtons. The force is calculated using the screened Coulomb force equation.
ID	Indicates the unique ID of a Geometry element, particle surface, particle, and collision.
Moment of Inertia	Indicates a measure of a particles resistance to a change of momentum for a sphere defined as: $I = \frac{2}{5} m r^{2}$
Kinetic Energy	Indicates the kinetic energy defined as: $K_{e} = \frac{1}{2} m υ^{2}$ where v is the velocity magnitude of the particle.
Mass	Indicates the magnitude of the gravitational force on a particle defined as: $m = V ρ$
Number of Particles	Indicates the total number of particles in a simulation (or bin group) at that point in time. In a bin group, you can use the Total over time option. This will produce a cumulative particle count for any particles that pass through that bin group. The total over time option can only be used for bin groups with 1 bin.
Orientation	Indicates the alignment of a particle in relation to Cartesian space. It is represented as a 3X3 matrix that defines the rotation of the particle from its original orientation (as defined in Creator and assigned an identity matrix).
Position	Indicates the x, y, or z position of the center of the particle.
Potential Energy	Indicates the potential energy defined as: $P e = m g h$ where m is the particle mass, g is the gravity, and h is the distance between the center of mass of the particle and the defined “ground” level. If the gravity is acting in negative Z, the ground level is z=0.
Residence Time	Indicates the measure of how much time a particle has existed in the simulation. “Residence time = Simulation Time - Particle Creation Time”. You can set the simulation time by navigating to Analyst > File > Export Simulation Deck. This option will impact the Residence Time shown on the particles following the equation “Residence time = Simulation Time - Particle Creation Time”
Rotational Kinetic Energy	Indicates the energy defined as: $0.51 ω^{2}$ where I is the inertia, and ω is the angular velocity magnitude.
Time	Indicates the real time it takes for an event to occur.
Torque	Indicates the tangential contact force * particle radius.
Total Energy	Indicates the sum of the kinetic energy, rotational kinetic energy, and potential energy of a particle.
Total Force	Indicates the resultant unbalanced forces on a particle or Geometry element in x, y, and z.
Velocity	The velocity of the particles is defined as the rate of change of displacement (in x, y and z)
Voidage	Indicates the percentage of space not taken up by particles. Voidage can be obtained by creating a Grid Bin and Voidage query. The Voidage property is defined as: $V o i d a g e = \frac{V_{b i n} - V_{p a r t i c l e s}}{V_{b i n}} X 100$ where V_bin is the volume of the defined bin, and V_particle is the sum of the volume of all the particles inside the bin. Voidage, therefore, does not consider the overlap between particles, which quantifies the deformation of the particles. A particle which overlaps two or more bins will only be counted in the bin that contains the particle center of mass.
Volume	Indicates the amount of space that a particle takes up.

Geometry Attributes


Attribute	Description
Charge	Indicates the electrical property of Geometries (such as electrons and protons). A material with an excess of electrons has a negative charge; a material with an absence of electrons (or an excess of protons) has a positive charge. Materials with a balanced number of electrons and protons are called 'neutral'. Positive and negative charges cause an attractive force to be applied between the elements (Particle-Geometry).
Compressive force	Indicates the sum of the surface normal forces on the Geometry.
Distance	Indicates the distance from the center of a Geometry node from a reference point or plane.
Electrostatic force	Indicates the force of interaction between charged elements, measured in Newtons. The force is calculated using the screened Coulomb force equation.
ID	Indicates the unique ID of a Geometry element, particle surface, particle, and collision.
Node 1, 2, 3	Indicates the position (x, y, and z) of the Geometry nodes.
Number of geometry elements	Indicates the sum of the Geometry elements. Geometries are split into triangular elements.
Position	Indicates the X, Y, or Z position of the center of the Geometry element.
Torque	Indicates the tangential contact force * distance, where distance is the distance from the center of mass to the contact point. The torque is calculated from the individual torque and moment about each individual Geometry element which is then converted to the torque on the whole Geometry about the center of mass. The torque can be plotted or exported along the x, y, and z axis.
Total Force	Indicates the resultant unbalanced forces on a particle or geometry element in x, y , and z.
Velocity	Indicates the rate of change of displacement of the individual Geometry nodes.

Contact Attributes


Attribute	Description
Contact vector 1,2	Indicates the vector connecting the contact point to the center of the particle when two particles collide.
Distance	Indicates the distance from the point of contact to a user-defined point or plane.
Normal force	Indicates the force that is created when two bodies are in direct contact with one another. It always acts perpendicular to the body that applies the force. The force depends on the contact model used, and will be a spring force with a damping component. The reported force on particles includes damping forces, and the reported force on Geometries is the undamped force.
Normal overlap	Indicates the normal deformation of a particle. The normal overlap N between two particles i and j at positions p_i and p_j with radii r_i and r_j is defined as: $N = (r_{i} + r_{j}) - (p_{1} - p_{j})$
Number of contacts	Indicates the number of contacts or impacts occurring between elements at data write-out points. In other words, the contact is in progress when the write-out takes place. The contact has an associated force, position and so on - these are discrete values. If two elements stay in contact with each other for some time. For example, over four write-out points, four contacts will be stored and each of these may have a different force, position and so on
Position	Indicates the central point between two elements at the point in time when a contact starts.
Tangential force	Indicates the force from the tangential overlap.
Tangential overlap	Indicates the tangential displacement of the contact point up to the point at which the contact ends or the particle begins to roll or slip. The tangential overlap represents the tangential deformation of a particle.
Time	Indicates the real time it takes for an event to occur.

Collision Attributes


Attribute	Description
Average normal force	Indicates the average normal force over the duration of a single collision.
Average tangential force	Indicates the average tangential force over the duration of a single collision.
Distance	Indicates the distance from the collision position to a user defined point or plane.
Duration	Indicates the total time that the two elements involved in a collision are in contact.
End time	Indicates the time at which the collision ends.
ID	Indicates a unique number which can be used to track the unique collision and the elements involved.
ID Element n	Indicates a unique number for each element in a collision.
Maximum normal force	Indicates the maximum normal force experienced during a single collision.
Maximum tangential force	Indicates the maximum tangential force experienced during a collision.
Normal energy loss	Indicates the energy lost during a collision due to the normal overlap.
Number of collisions	Indicates the number of completed collisions. Only completed collisions are counted, and collisions in progress (contacts) are not counted.
Position	Indicates the central point between two elements at the point in time when a collision starts. The collision position is written out on completion of the collision.
Relative velocity	Indicates the relative velocity of two elements in a collision is V_a - V_b. Note: This value is calculated from the contact points and not the particle centers.
Relative velocity	Indicates the value calculated from the contact points and not the particle centers.
Relative velocity normal	Indicates the relative normal velocity of two elements in a collision is Vn_a - Vn_b.
Relative velocity tangential	Indicates the relative tangential velocity of two elements in a collision is Vt_a - Vt_b.
Start time	Indicates the point in time when the first contact of a collision occurs.
Tangential energy loss	Indicates the energy lost during a collision due to the tangential overlap.
Time	Indicates the real time it takes for an event to occur.
Total energy loss	Indicates the sum of the normal and tangential energy loss.
Velocity of element A/B	Indicates the velocity magnitude of an element involved in a collision. Element A will have the lowest ID number and element B will have the highest.