Analysis and modelling of non-local eddy diffusivity for turbulent scalar flux

The local eddy diffusivity model for the turbulent scalar flux is widely used to understand and predict transport in turbulence. However, approximation space time not always valid actual flow. An exact non-local expression was previously derived by author using Green's function. Even though profile of a channel flow evaluated, its only discussed phenomenologically. In this study, approach validated with help direct numerical simulation (DNS) data homogeneous isotropic turbulence an inhomogeneous mean propose systematic expression. Initially, it verified that agrees value directly obtained from DNS. addition, effect accounts overestimation counter-gradient diffusion phenomenon. temporal behaviour further evaluated DNS data. Its being proportional two-point velocity correlation proposed manner customary statistical theory well value, reproduced flux. These results substantiate potential model.