Abstract

An existing horizontal density stratification in a fluid gives rise to buoyancy-driven currents. Such exchange flows between two zones at different densities cause advective transport of mass, heat, particulates, chemical and biological substances, which often has undesirable consequences for one or both zones. They may occur in a variety of natural and industrial settings, across a wide range of temporal and spatial scales. It is often impossible to stop these buoyancy-driven flows by mechanically shutting the gates or the doors since this would hinder or obstruct the passage of humans, vehicles or ships. Thus, alternative mitigation strategies for reducing the buoyancy-driven exchange flows have been devised. In this talk, we will consider plane turbulent flows, such as air curtains and bubble curtains, that act as separation barriers between two zones at different densities. In particular, we will discuss the performance of an air curtain in a variety of practical situations and present experimental and theoretical results for their sealing effectiveness. We will also explore the behaviour of a bubble curtain and highlight the similarities and the differences between an air curtain and a bubble curtain.