# DEM Application

The DEM Kratos Team

## Theory

This application solve the the equations.... Mathematical approach to the problems.

Nothing numerical

### The contact laws

Concept of indentation

(restit. coef)

## Numerical approach (implementation)

Structure of the code (Strategy, Scheme, Element, Node, Utilities, functions frequently used like FastGet,...)

## Benchmarks

Insert here all the benchmarks of the application.

For every benchmark insert a video or at list a photo (not only a link)

For every benchmark - brief description of the solved problem, if it is a benchmark that can be found in literature, insert the link to the reference or, at least a reference). - reference with a link the location in which you describe all the theory behind Numerical approach.

## How to analyse using the current application

### Pre-Process

GUI's & GiD

##### D-DEMPack

Discontinuum / non-cohesive

##### C-DEMPack

Continuum / Cohesive

Fluid coupling

## Application Dependencies

The Swimming DEM Application depends on the DEM application

FEM-DEM

## Contact

-Miguel Angel Celigueta: maceli@cimne.upc.edu

-Guillermo Casas: gcasas@cimne.upc.edu

-Salva Latorre: latorre@cimne.upc.edu

-Miquel Santasusana: msantasusana@cimne.upc.edu

-Ferran Arrufat: farrufat@cimne.upc.edu

## Problems!

#### What to do if the Discrete Elements behave strangely

In the case you notice that some discrete elements cross walls, penetrate in them or simply fly away of the domain at high velocity, check the following points:

In the case of excessive penetration:

• Check that the Young Modulus is big enough. A small Young Modulus makes the Elements and the walls behave in a very smooth way. Sometimes they are so soft that total penetration and trespass is possible.
• Check the Density of the material. An excessive density means a big weight and inertia that cannot be stopped by the walls.
• Check the Time Step. If the time step is too big, the Elements can go from one side of the wall to the other with no appearence of a reaction.
• Check the frequency of neighbour search. If the search is not done frequently enough, the new contacts with the walls may not be detected soon enough.

In the case of excessive bounce:

• Check that the Young Modulus is not extremely big. An exaggerated Young Modulus yields extremely large reactions that can make the Elements bounce too fast in just one time step.
• Check the Density of the material. An excessive density means a big weight and inertia that cannot be stopped by the walls.
• Check the Time Step. If the time step is too big, the Elements can go from one side of the wall to the other with no appearence of a reaction.
• Check the frequency of the neighbour search. If the search is not done frequently enough, the new contacts with the walls may not be detected soon enough.

You can access the calculation code through this site.