Physical Processes in Near Field Buoyant Plumes: Turbulence, Mixing and Lateral Spreading

Buoyant plumes are characterized by a distinct contrast in properties between plume and ambient water. An understanding of their physics is crucial for interdisciplinary study of estuarine and coastal regions because discharge flow is often a source of nutrients, biological species, sediment, and toxic contaminants. This book investigates the nature of physical processes associated with near field buoyant plumes, and describes the relationship between processes. Two field sites, one thermal plume in Massachusetts, USA, and the Merrimack River plume, Massachusetts, USA are studied. Observed mixing in the near-field of the thermal plume is driven by bottom friction. The industrial plume studied here is dynamically similar to larger geophysical plumes, but differs in important aspects that can be fully characterized by the initial aspect ratio of the discharging plume. Estimates of three non-dimensional parameters, which represent mixing, spreading, and the bulk Richardson number, suggest that a quadratic relationship exists between mixing and spreading for the river plume. Estimates also yielded time scales for turbulence evolution that are consistent with values in literature.