Particle in Cell
What is the Particle In Cell Method?
In 1957, Francis H. Harlow with Los Alamos Scientific Laboratory developed the Particle-In-Cell (PIC) method that centered on manipulating particles that represented a small mass. Each particle had a variable for position, mass, and species information for its placement on an Eulerian 2D mesh. This allowed the transient and compressible flow of multiple materials to be carried out with no restrictions.
This code was the first to use the T-3 team's technique of solution phases, which consisted of dividing the computational cycle into a Lagrangian and Eulerian phase, and it was one of the first techniques to describe a strongly distorted flow in multidimensional spaces.
This method first divides the particles into a grid that averages particle values into weighted sums for calculations. It keeps track of mass, momentum and energy of shear and bulk values. This allows for systems to more easily reflect effects of particles on each other and is a necessary step to understanding fluid dynamics.
The Particle in cell method
To run a simple particle cell simulation the steps usually involve:
- 1. Initialize the grid, particles and the starting values for density and velocity (or direction) for each cell; although some simulations can also involve temperature, charge density and reference potential (which is similar to viscosity). Then plot them
- 2. Using the initial cell velocities and densities apply their values onto each of the particles in their cell respectively.
- 3. Using the new cell values determine their individual new velocities and positions.
- 4. Check for particle collisions and adjust trajectories based on your simulations goals. Different particle simulations handle collision on a case by case basis. Even when comparing fluid dynamics how particles react on collision can vary. In some cases particles can be removed by collision so for these cases particles are added to the simulation to make sure there is a constant amount of particles.
- 5. Calculate the new average weight fields for each of the cells by using the now changed values of density and velocity.
- 6. Repeat steps 2-5 to continue the simulation.
Current and future uses
Particle in Cell has been very successful in several fields due to its intuitive method and ease of implementation. Today it is one of the leading techniques in modeling plasma interaction. In the field of fluid simulation, adaptations such as The FLIP (Fluid-Implicit Particle) algorithm have been made with Particle in Cell dynamics.
Site was last updated on 10/17/2013