# Particle Lagrangian Tracing

In this tutorial, the modeling of particles is considered. One of the important points in the physics of flows with particles is the path traversed by the particle. To calculate the path of the particle and trace it over time, Ordinary Differential Equations (ODEs) are written for the motion of the particle, and integrate it to calculate the particle’s location and velocity at any given moment according to a suitable initial condition. The phase of the particle in its two-phase flow has its own mass flow rate. In fact, each particle has its own mass flow rate.

Eulerian or Lagrangian Model

The tracing of the particle by the Lagrangian method is a substitution for the Eulerian-Eulerian multiphase model, we must be careful to select the best method in practice. Essentially, the same physical characteristics are modeled. Although in the Lagrangian model particles have a defined geometric diameter, they are modeled as moving points. In this model, the particles do not occupy any volume of the solution domain and it do not take into account the interactions of the particles, since the ratio of the particle size to the continuous phase is very small. Generally, in this model, it is assumed that particles are points that have mass and that the shape and volume occupied by them are not important. Also, the details of the flow around the particle are ignored. These details may include phenomena such as near-particle flow, vortex, flow separation, and boundary layer. The local properties of the distributed phase are obtained from averaging a spatial location on a particle motion path from a given initial position. In this way, the path to all particles will not be achieved.