Title: Lagrangian micromixing modelling of reactive scalar statistics: scalar mixing layer in decaying grid turbulence

Authors: Andrea Amicarelli; Giovanni Leuzzi; Paolo Monti; Nicola Pepe; Guido Pirovano

Addresses: Ricerca sul Sistema Energetico - RSE SpA, SFE, via Rubattino, 54, 20134, Milan, Italy ' DICEA, Università di Roma La Sapienza, Italy ' DICEA, Università di Roma La Sapienza, Italy ' Ricerca sul Sistema Energetico - RSE SpA, SFE, via Rubattino, 54, 20134, Milan, Italy; Politecnico di Milano, DICA, P.zza Leonardo da Vinci, 32,20133, Milan, Italy ' Ricerca sul Sistema Energetico – RSE SpA, SFE, via Rubattino, 54, 20134, Milan, Italy

Abstract: A Lagrangian micro-mixing numerical model estimates the concentration statistics of reactive pollutants (NO, O₃ and NO₂) of a scalar mixing layer in decaying grid turbulence. A stochastic macro-mixing scheme computes the fluid particle trajectories, which describe the turbulent flow (Lagrangian turbulence), whereas the micro-mixing scheme interaction by the exchange with the conditional mean (IECM), implementing a new formulation for the mixing time, represents the dissipation of concentration turbulent fluctuations due to molecular diffusion. The non-homogeneous reaction-dominated limit (NHRDL) of the conserved scalar theory simulates chemical reactions. The numerical model integrates these three schemes and is validated by comparison with experimental and direct numerical simulation (DNS) data, whereas inter-comparisons with other numerical models are also reported. The study focuses on the reliability of Lagrangian stochastic models in representing micro-scale pollutant dispersion (air quality) and the importance of representing chemical reactions depending on instantaneous concentrations rather than their means.

Keywords: segregation coefficient; concentration fluctuations; Lagrangian micromixing; conserved scalar theory; CST; reaction-dominated limit; air quality; Lagrangian stochastic modelling; reactive pollutants; air pollution; reactive scalar statistics; scalar mixing layer; decaying grid turbulence; numerical simulation; microscale pollutant dispersion.

DOI: 10.1504/IJEP.2015.077456

International Journal of Environment and Pollution, 2015 Vol.58 No.4, pp.251 - 267

Received: 22 Dec 2014
Accepted: 04 Dec 2015
Published online: 01 Jul 2016 *

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