Interaction of buoyant plumes with two-layer stably stratified media

Abstract

A buoyant plume originating in the lower layer of a two-layer, density-stratified stable medium and its interaction with the density interface are discussed. As the buoyant plume reaches the density interface, it penetrates through or spreads under the interface, or does both, depending on the flow parameters. The subsequent natural circulation and mixing of fluids will be largely limited to the upper layer if the plume penetrates completely at the interface, or to the lower layer if the plume is stopped at the interface from rising further, or it will spread in both layers throughout the enclosure if the plume penetrates partially. The purpose of this experimental study was to investigate by means of salt water analog experiments whether the latter phenomenon can be observed under controlled flow conditions and, if so, what flow parameters govern the plume behavior. The actual experiment involves injection of high-concentration salt water from the top of a two-layer flow field (having a fresh water layer on top of a low-concentration salt water layer), allowing flow visualization of an “upside-down” analog of a rising hot gas plume. Partial plume penetration behavior was indeed observed on videotaped flow patterns. The ratio of mass penetrating the layer interface to the mass introduced in the plume source was estimated and correlated to variables representing the buoyant plume and the stratified medium.