Turbulent transport and mixing are important in many flows and relevant in disciplines such as biology, geosciences or chemical engineering. During a turbulent mixing process, scalar interfaces are continuously expanded and shrink, and complex small-scale scalar structures, mainly due to generation of high concentration gradients, are formed. Flow field typically defines the smallest lengthscales controlling the mixing. At small scales, molecular diffusion becomes dominant and scalar fluctuations are reduced locally. In turbulent flow, mixing process is governed by generation of the small-scale scalar gradients through turbulence and becomes independent of the molecular diffusivity. In turbulent flow fields, despite similarities between velocity and scalar statistics there exist important differences including local anisotropy and enhanced dispersion due to differential diffusion. Since these phenomena occur at the smallest scales resulting wide range of scalar field lengthscales is difficult to resolve in numerical simulations.
In this talk a stochastic strategy is presented to track variation of diffusion under turbulent flow. In this way, a computational approach is proposed for predicting mixing process under complex flow condition which can be used for the simulation of turbulent mixing in engineering applications.