# Integrating Rotational Degree Of Freedom in EDEM

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## Содержание

Understand - how rotational DOF are integrated inside EDEM. For this: prepare simulation which could be compared with analytics.
For this:

1. Prepare factory that creates particles
2. Prepare contact model which describes the rule of interaction
3. Prepare EDEM simulation
4. Measure something and compare it to analytic

## Factory

We create 2 particles on a distance 0.1m and rotated at an angle of 5-15 () degrees;
These particles are of 2 types "small" and a "big" one; Big particle has identity matrix as rotation matrix; Small particle is rotated using rotation matrix
Particles's velocity and angular velocity equals to zero;
Y and Z coordinates are the same (0.5,0.5); Only X is different (0.45 for "big" and 0.55 for "small");

• For small particle:

double OrientAngle = pi/12; // angle between particles in Radians
orientation = 1.0; // Rotating particle. X axis.
orientation = cos(OrientAngle);
orientation = -sin(OrientAngle);
orientation = sin(OrientAngle);
orientation = cos(OrientAngle);

## Contact Model

In our project we used simple contact model.
All central forces we made zero. Also we made zero all torques except torque, which operates on a "small" particle.
calculatedElem2AdditionalTorqueX = 1.0 * (elem1Orientation * elem2Orientation + elem2Orientation * elem1Orientation );
In this formula С = 1.0

## EDEM simulation

### Globals:

Interaction: Particle to particle
Model: our contact model
No gravity
There are two materials "material" and "material_2" with different density for "material" 1000 for "material_2" 1.7e+05
Restitution: 0.5
No static and rolling friction

### Particles:

We create particles of 2 types;"big" with big moment of inertia (100kgm2 X-axis) and "small"(0.000285kgm2 X-axis);Both particles are made of 2 surfaces placed along Z-axis on a distance of 2 particle radius

## Measures

We measured the period of oscillation

### Integration

We measured period using the Graph of angular velocity and got the result

## Results

So we got the result that is different to the analytic;
Then we wrote small programm on C# that integrates the equalation in a simple way and got the result

We checked all in EDEM simulation; Changing parameters of particles, roll stiffness didn't gave any difference the results stayed different to analytic.