Special Issue: Jets, Plumes, and Thermals: Application to Environmental Flows

Motions comprising of jets, plumes, and thermals are commonly encountered in geophysical and environmental flows. Some examples include release of hot gases during volcanic eruptions, ocean overflows, effluent discharge and transport, convection, cloud formation, melting and solidification. These fluid motions are greatly modified in the presence of stratification, rotation, or different phases in the environment [List 1982, Deremble 2016, Boufadel et al., 2020]. In the presence of gravity, the density differences have a dramatic impact on the dynamics and mixing of heterogeneous fluids. For example, thermal stratification in reservoirs can reduce the vertical mixing of oxygen to the point that water at the bottom becomes anoxic through the action of biological processes. The 2010 Gulf oil spill disaster is yet another instance where ocean stratification modified the dynamics of the oil-gas jet. Meltwater and sediment-laden jets/plumes at tidewater glaciers, resulting from the localized subglacial discharge of surface melt, influence submarine melting of the glacier and the delivery of nutrients to the fjord’s surface waters. Thermals play a key role in cloud micro-physics and determine the type and composition of clouds. Rotation is known to strongly modify the dynamics of jets and plumes. Given the rich physics and wide application, study of jets, plumes, and thermals is an important underlying problem in geophysical and environmental flows.

The study of jets, plumes, thermals, and currents dates back to the 1950’s with the pioneering work of Morton, Taylor, and Turner (MTT) in 1956. Since then, a lot of work has been done to understand the dynamics of these flow systems, development of empirical parameterizations and new theory and models. Although notable progress has occurred in recent years, there are still important questions unanswered, which limit our capability to accurately model these flows. Over the years, different aspects of jets, plumes and thermals have been studied in some detail, namely, pure jets and plumes, buoyant jets, lazy plumes, melt plumes, thermals, particle-laden/particle-bearing jets and plumes, thermals with phase change, and much more. All of these research studies have helped advance our understanding of this topic. Five decades down, the topic seems as relevant as before and clearly some of the questions remain, which could be answered through detailed investigations of the small scales via Direct Numerical Simulations (DNS) or Large-Eddy Simulations (LES), detailed experiments with sophisticated technology, and the development of novel constitutive relations. These results could later be extended to real-life situations such as ocean mixing, cloud modeling, ice melting, avalanches etc.

The aim of this Special Issue is to present a group of papers that could summarize the state-of-the-art of the knowledge of jets, plumes, and thermals in environmental and geophysical applications, at the time of reporting novel pathways in research. It will contain experimental, theoretical and numerical contributions on the topic.