An evaluation of a Lagrangian stochastic model for the assessment of odours. (1st June 2019) - Ferrero, Enrico
Abstract: In this work, we propose and evaluate a one-particle Lagrangian stochastic model for the assessment of the concentration-fluctuation variance, which is often used to predict odour hours for example. The main challenge is to provide a suitable parameterisation for the concentration-variance dissipation time scale. While the particle mass is conserved along the particle trajectory, the concentration variance dissipates. The concentration variance in a Lagrangian particle model evolves according to the same Langevin equation used for the simulation of the turbulent dispersion resulting in a mean concentration field. The variance dissipation is taken into account via a decay term with a finite time scale. We herein discuss and compare different parameterisations of the variance-dissipation time scale against observations from a field experiment. It was found that best results are obtained prescribing the ratio between the concentration-variance dissipation time scale and the Lagrangian time scale, which depends on the travel time. Highlights: A new approach for the evaluation of the odour hour is presented and discussed. Concentration distribution 90th percentile is given by the concentration variance. The concentration variance is calculated by means of a Lagrangian model. Different parameterisation fo the concentration variance dissipation are compared.