Focus on Fluids Highlighted Article

The paper Statistical Nonlocality of Dynamically Coherent Structures was recently highlighted in the Focus on Fluids article Ineffective Diffusivity

The abstract of the Focus on Fluids article is as follows: An important problem in passive scalar transport is to parametrize the effect of a fluctuating component of the flow, in order to overcome a limited resolution. A local effective diffusivity is one such parametrization, and over the years there have been many different suggestions for ‘closures’ that relate the advective flux to gradients of the mean concentration. Souza et al. (J. Fluid Mech., 2023, in press) introduce a stochastic framework where the local effective diffusivity is replaced by an exact effective diffusivity operator. By computing this operator for various examples, they quantify deviations from the local approximation, which can suggest areas of improvement and novel closure models.