Turbulent Dispersion Modelling in a Complex Urban Environment - Data Analysis and Model Development

This report summarises recent research conducted by the DSTO in plume model development for urban environments, with an emphasis on establishing clear physical grounds for the models, yet maintaining enough simplicity to be treated numerically in an operationally viable way. The aim is not to replace existing operational models with a new generation of more accurate models, but to provide a more physics-based framework for flow and dispersion in an urban environment that can reconcile the empirically based approach of current operational models, and the more sophisticated computational fluid dynamics techniques now gaining popularity for atmospheric dispersion applications. A key feature of the model framework developed in this report is the definition of a single parameter that describes canopy morphology, and links this to canopy flow variables. A simple canopy dispersion model is then developed, based on flow parameters generated by the canopy model. In relevant areas the well-known Urban Dispersion Model by the UK Defence Science and Technology Laboratory is used as a benchmark for comparison. Supporting evidence for the models developed here is supplied through comparison with experimental data from a water channel simulation. The original document contains color images.