Interfacial Layers Between Regions of Different Turbulence Intensity

Recent developments in the physics and modeling of interfacial layers between regions with different turbulent intensities are reviewed. The flow dynamics across these layers governs exchanges of mass, momentum, energy, and scalars (e.g., temperature), which determine the growth, spreading, mixing, and reaction rates in many flows of engineering and natural interest. Results from several analytical and linearized models are reviewed. Particular attention is given to the case of turbulent/nonturbulent interfaces that exist at the edges of jets, wakes, mixing layers, and boundary layers. The geometry, dynamics, and scaling of these interfaces are reviewed, and future lines of research are suggested. The dynamics of passive and active scalars is also discussed, including the effects of stratification, turbulence level, and internal forcing. Finally, the modeling challenges for one-point closures and subgrid-scale models are briefly mentioned.