Modelling of fluctuating concentration fields in complex industrial areas

In the framework of the new legislation related to accidental scenarios, the forecast of damage areas is a key issue. In such problems the models should reliably predict the individual exposure during a strong emission event. For the impact assessment, it should be more relevant to predict parameter related to maximum dosage rather then to average concentration. Up to now, Gaussian models are the most used to determine the impact of accidental releases. In order to overcome the simplistic limitations of this approach, the numerical model, LAGFLUM (LAGrangian FLUctuation Model), has been developed. The model utilizes a macromixing scheme, based on the so called "well-mixed" criterion, to evaluate the mean concentration. Moreover the micromixing IECM (Interaction by Exchange with the Conditional Mean) scheme is integrated to calculated the higher statistical moments of the concentration. LAGFLUM is applied to determine the mean and the fluctuation statistics of a concentration field, during a short emission episode in a complex industrial area, which includes 12 irregular shaped buildings. The model is coupled with the micro-SWIFT model, which evaluates the wind field and the turbulence parameters in the proximity of buildings. The results evidence the conditions where the fluctuations of concentration prevail respect to the averages.