A Lagrangian approach for modelling turbulent transport and chemistry

A Lagrangian two-particle model for the relative diffusion and mixing of tw o reactive species is proposed. The model has been tested for consistency i n simple geometrical configurations and has been compared to experimental d ata, Eulerian first- and second-order closure models as well as to other La grangian models. The model includes the covariance between the two species and therefore gives better predictions of both diffusion and chemistry than first-order closure models or the one-particle model proposed by Chock and Winkler (1994a,b, Journal of Geophysical Research, 99 D1, 1019-1031, 99 D1 , 1033-1041). The model is a generalisation of the model presented by Komor i et al. (1991, Journal of Fluid Mechanics 228, 629-659). The results of th e calculations, although preliminary in character, indicate that the propos ed algorithm is robust and efficient, and yields satisfactory results in tu rbulence with slow to moderate chemistry. (C) 1999 Elsevier Science Ltd. Al l rights reserved.