Buoyant plumes in crossflows

Article By:

Diez, F. Javier Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, New Jersey.

Last reviewed:2008

DOI:https://doi.org/10.1036/1097-8542.YB084170

In environmental flows, the most common way of mixing fluids is through a fluid discharge. Fluid discharges refer in general to releases of liquids, gases, or a combination of both. They are found in many applications, including the following: (1) industrial applications such as furnaces, smoke stacks, or mixing of pharmaceutical drugs; (2) wastewater disposal in rivers, lakes, and oceans; (3) forest fires and building fires; and (4) many common household situations, such as sprinklers, garden hoses, and faucets. Furthermore, based on the geometry of the discharge, they can occur in still environments, coflows, or crossflows, or at an angle. For instance, it is easy to visualize the plume vertically rising from a burning cigarette in a still environment. Similarly, the smoke from a forest fire can be visualized being carried downstream many miles by the wind (that is, in a crossflow). Discharges are also characterized by their amount of momentum or buoyancy. Thus, a jet is a discharge of fluid into a fluid environment of the same density. For instance, a jet ski in a lake will eject water at high speed (that is, momentum) into water to propel itself. On the other hand, if one pours gasoline on the ground and lights it, the smoke will rise due to the difference in density between the air being heated and the cooler surrounding air. Finally, both buoyancy and momentum flux can be present at the source of the injection, and this condition will create a buoyant plume (also called buoyant jet by many researchers). The remainder of this article will focus on the study of buoyant plumes.

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