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Particle tracking
| Method indicator | ||
|---|---|---|
| Bottom-Up | Hybrid | Top-Down |
| YES | ||
Summary of key issues:
| Issue | Description |
|---|---|
| Description | This technique typically uses the output from hydrodynamic and/or advection-diffusion models to predict particle movements in a Lagrangian manner. The flow regime is seeded with particles having defined properties (size, density, settling velocity, etc) and tracked as they move with the flow. This is a useful means of visualising flow patterns, particularly eddies and recirculation cells but can also be used to examine the movement of material away from particular activities such as dredging, dumping, outfalls, etc. By examining the statistics of how particles are re-distributed in the model domain, it is also possible to extract some quantitative information. |
| Temporal applicability | Typically applied to the short-term (single tide up to several months). |
| Spatial applicability | Varying from a single point to estuary-wide including the open coast. |
| Links with other tools | Typically, particle models are run using the output from a hydrodynamic flow model. Links have also been established with bed updating methods to provide a form of hybrid bed updating model (Sandtrack) |
| Data sources |
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| Necessary software tools / skills | A range of modelling skills can be required depending on the complexity of the hydrodynamics of the area being studied and the particles being simulated. Typically, expert knowledge of hydrodynamics and water quality is required. |
| Typical analyses | Transport of particles, looking at the fate and concentration within the environment. |
| Limitations | Computation time increases linearly with the number of particles, this is often a limiting factor. Calibration data for the particle model is often limited with assumptions made for diffusion/dispersion coefficients. |
| Example applications | Thames and Humber Estuaries |
Particle tracking uses the output from hydrodynamic and/or advection-diffusion models to predict particle movements in a Lagrangian manner. The flow regime is seeded with particles having defined properties (size, density, settling velocity, etc) and tracked as they move with the flow. This facilitates the visualisation of flow patterns, particularly eddies and recirculation cells but can also be used to examine the movement of material away from particular activities such as dredging, dumping, outfalls, etc. Quantitative information can be obtained by examining the statistics of how particles are re-distributed in the model domain.
The discharged or spilled material is considered as particles being advected with the surrounding water body and dispersed as a result of random processes including the dispersion caused by current, wind-induced turbulence and molecular diffusion. A corresponding mass is attached to each particle. This can change during the simulation. Additionally, the particles can deposit with a constant settling velocity and re-suspend.
Particle Tracking methods are crucial to simulating transport phenomena such as transport of pollutants in coastal waters. These methods are able to quite accurately predict the pollutant transport in cases of steep concentration gradients after the pollutant has just entered into the water whereas conventional methods such as finite difference and finite volume methods may have difficulties. Since the computation time in a particle model increases linearly with the number of particles, this often forms a limiting factor.
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