The stability of vertical thermal buoyancy induced flows in cold pure and saline water

Abstract

Buoyancy driven flows in cold pure and saline water very commonly arise. The anomalous density behavior of cold water, for example, a density extremum at about 4°C in pure water at atmospheric pressure, commonly has very large effects on flow and transport. Resulting mechanisms have been studied for various geometries and conditions, primarily for laminar flow. This study assesses the stability and instability mechanisms of developing flows adjacent to a vertical surface subject to both uniform flux and isothermal bounding conditions, in pure water at two pressure levels. The specific condition treated is that in which the quiescent ambient medium is at the density extremum condition. It is found that even this relatively weak effect, the variation to a density extremum across the thermal layer in the fluid, has important effects on instability and disturbance growth downstream. However, the nature of the instabilities and their selective amplification are similar to those well known for more ordinary fluid conditions. The new results here are compared with recent measurements of disturbance behavior, with excellent agreement.