Numerical simulation of particle trajectory and atmospheric dispersion of airborne releases

摘要

Numerical simulation of particle trajectory and atmospheric dispersion has been performed for an airborneaccidental release from a nuclear power plant site. A Long-range Particle transport and Dispersion Model (LPDM) basedon a Lagrangian approach is developed and tested in this work. The Lagrangian transport/dispersion model is directlycoupled with an atmospheric prediction model, RAMS (Regional Atmospheric Modeling System), to provide necessarymeteorological fields in a three-dimensional domain. An advantage of this direct coupling is that the meteorological datagenerated by RAMS can be used directly for trajectory calculations without storage, thus reducing the CPU time consumedin the data storage and retrieval. This effort was done to be able to use this directly coupled modelling system for real-timepredictions in case of an accidental release from a potential site. The simulated Lagrangian trajectories were compared with those obtained using observed hourly weather data obtainedfrom an on-site meteorological tower. The results indicated that this one-way coupling between LPDM-RAMS providedalmost identical trajectories when compared with those obtained using LPDM alone driven by hourly observed wind data.The comparison demonstrated the reliability of the RAMS meteorological predictions for the site under consideration. Thecomparison also indicated that LPDM (run in a stand alone mode), with hourly-observed wind data, could also be usedfor trajectory calculations over flat terrain. The model was developed on a parallel processing computer (SGI workstation, ORIGIN 2000 computer with eightprocessors) for use in real-time forecast mode. The computational time was about one-third of the simulation time, whileusing four processors. The model options need to be explored to reduce the computational time further and test itsperformance for real-time atmospheric dispersion applications.