Particle and Field Descriptions of Fluid Motion

Lagrangian vs. Eulerian Description: In fluid mechanics, we use two primary approaches to describe the motion of particles:

As an alternative (e.g., when tracking an individual particle’s motion in pollution studies), we sometimes use the Lagrangian description of particle motion, where the acceleration, position, and velocity of a particle are specified as a function of time only.

Lagrangian: Follows a specific particle’s trajectory and is therefore a particle description of motion.
Eulerian: Describes any particle at a particular position and a specific instant of time, making it a field description of motion.

This summary helps distinguish the fundamental difference between the two descriptions in fluid mechanics.