Lagrangian particle tracking

Lagrangian Particle Tracking (LPT) is a method used in fluid mechanics to analyse flow behaviour by tracking the motion of individual particles. It provides a Lagrangian perspective, in which the flow is described by following fluid parcels or tracers over time, rather than observing changes at fixed locations as in the Eulerian frame.

In experimental studies, LPT is typically performed using three-dimensional Particle Tracking Velocimetry (3D-PTV). Neutrally buoyant tracer particles are seeded into the flow, and their positions are recorded using high-speed cameras and stereo reconstruction techniques. The resulting particle paths allow for the study of turbulence structure, transport phenomena, and time-resolved Lagrangian statistics.^{[1] [2]}

In computational fluid dynamics, LPT refers to the numerical simulation of discrete particles embedded in a continuous flow field. The fluid phase is typically solved in an Eulerian framework, while the particle phase is resolved using Lagrangian mechanics. This approach—also termed Discrete Particle Simulation (DPS)—is particularly suited to dilute multiphase flows, such as sprays, aerosols, or dust transport, where particle–fluid coupling is weak and particle inertia plays a significant role. Applications include industrial mixing, combustion modelling, and environmental particle transport.^[3]

Beyond engineering and turbulence research, LPT has been widely adopted in environmental modelling. Its capacity to resolve particle motion over complex terrain and at large scales makes it suitable for studying atmospheric pollutant dispersion. In regional air quality assessments, LPT methods have been used for both forward simulations (predicting particle transport from known sources) and inverse modelling (inferring sources from observed concentrations). These techniques have proven effective in identifying transboundary pollution pathways and assessing exposure risks.^[4]

See also

• Lagrangian and Eulerian specification of the flow field