TURBULENT MIXING WITH CHEMICAL-REACTION IN THE PLANETARY BOUNDARY-LAYER

Detailed statistics of the fluctuating concentration field produced by large-eddy simulations (LES) of the chemically reactive mixing of two species in a convectively driven mixed layer are presented. The effec t of the turbulent mixing on the effective reaction rate between the s pecies is analyzed. The segregation between the species is shown to be significant for fast reactions, and therefore correct model predictio ns of the evolution of the species concentration requires an estimate of the segregation coefficient. Some simple modeling concepts for one- point second-order turbulence closure schemes are examined and compare d with the LES results. The results are a promising indication that se cond-order closure schemes can be extended to provide a practical calc ulation of the turbulent mixing effects on fast chemical reactions.