Multi-scale dynamics at the turbulent/non-turbulent interface of jets and plumes

Lead Research Organisation: Imperial College London
Department Name: Civil & Environmental Engineering

Abstract

Flows in environmental fluid mechanics contain a wide range of scales at which important physical processes are taking place. For instance, in wastewater outfall hydrodynamics, the relevant processes range from large scales e.g. the size of the water body (order of 10^4 m), to the smaller scales of the discharge (order of 10 m) and down to the Kolmogorov scale at which turbulent energy is dissipated (order 10^-3 m). The separation between scales is even more evident in the atmospheric dynamics, where over ten orders of magnitude separate the largest cyclonic scales of several thousand kilometres from the smallest ones.
These examples highlight the challenges engineers and scientists are facing to study such problems. In particular, existing modeling tools should be able to describe outcomes related to large scale dynamics in problems like pollutant dispersion, ocean outfalls or atmospheric plumes, where the smaller scales, though substantially affecting the overall physics, are often approximated rudimentarily. The overarching goals of the research proposed here are to provide a detailed insight into the role that different scales have on the dynamics of jets and buoyant plumes, which occur in a wide variety of natural and man-made situations, and to develop better modeling solutions, based on the physics of the small scales, that might be employed, e.g., in the context of Large Eddy Simulation (LES), to improve the representation of near field processes in existing modeling tools. New models will be built into open source codes and this will increase the impact of the project on environmental science and industrial applications. In fact, understanding the multi-scale interactions between sub-metre scale installations and ocean scales over hundreds of metres is crucial for assessing environmental impacts and optimisation of modeling tools is vital to minimize project costs or maximize profits.

Publications

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Cimarelli A (2021) Spatially evolving cascades in temporal planar jets in Journal of Fluid Mechanics

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Neamtu-Halic M (2020) Connecting the time evolution of the turbulence interface to coherent structures in Journal of Fluid Mechanics