Simulator Grid (CPU Engine only)

The main computational challenge in DEM simulations is the detection of contacts. EDEM Simulator can examine each cell and analyze only those that contain two or more elements (and hence a possible contact) by dividing the domain into grid cells, saving processing time.

To use the Simulator grid:
  1. Click the icon to display the CPU engine/Particle-Particle grid in the Viewer.
  2. Draw the grid, and divide the domain into cells of a specified size.
  3. Identify the active cells (containing two or more elements) and check for contacts.
  4. Calculate forces on the elements.
  5. Reposition the elements as a result of any force acting upon them.
    Active cells are identified and the process is repeated. As the grid length decreases, fewer elements are assigned to each grid cell and contacts become easier to resolve. The fewer particles per grid cell, the more efficient the simulator. If there is no more than one particle in each grid cell, then contact detection is eliminated to help the simulation progress faster. The ideal length of a grid cell is 2-6Rmin, where Rmin is the minimum particle radius in the simulation.
    Note: The CUDA solver uses a different contact detection method for Multi-Spheres, eliminating the need for a grid. Therefore, the option to set a grid size in the CUDA solver is not available.

    The results achieved by a simulation are not affected by the number of grid cells, only the time taken to reach them.

    EDEM calculates the smallest particle size in the simulation (Rmin). You then set a grid cell size based on this particle size. 3 Rmin is the default value, typical ranges are 3-6 Rmin, the Estimate Cell Size option provides guidance on the optimal Cell Size for a specific simulation Time Step. The grid impact only the simulation speed and not the simulation results. A smaller grid size results in more memory (RAM) usage. Therefore, reducing the grid cells size below 2 Rmin can result in a significant slow-down for the simulation.

    EDEM GPU has a different grid size for Particle-Particle and Particle-Geometry interactions. You define the Particle-Particle Rmin size in the Simulator Settings, and the Particle-Geometry cell size in the Advanced Settings. This allows you to specify the optimal grid setting for the GPU Particle-Geometry interactions. You can use the default ‘recommended grid cell size’ or a custom value. Typically the optimal Particle-Geometry grid setting for GPU is larger than the optimal CPU or Particle-Particle value.