Near-Wall Double-Diffusive Convection

Double-diffusive convective flows have been studied extensively in the context of physical oceanography.i-7' The most intensively investigated one of these is the thermohaline convection. The thermohaline convection may play an important role in the,mJ'xing of upper and lower layers of sea water. It has also been suggested that double-diffusive convection has some relevance to geophysical and metallurgical processes.8' No extensive studies on these processes, however, seem to have been initiated yet. Apart from these applications, a phenomenon of double-diffusive convection Per se is of fluid-mechanical interest. In recent years, the so called dissipative structures in diverse flow systems including double-diffusive convection have attracted many investigators.9-iL" Benard convection which occurs when a layer of fluid is heated from below gives rise to one of the typical dissipative structures (Benard cells). It was the study of this type of flow that led to evolution of the concept of chaos.i3-t6' The double-diffusive convective flows give rise to the dis.sipative structures more complicated than those due to a single diffusivecomponent convectlon. The purpose of this paper is to report some laboratory results relevant to the doublediffusive (mainly thermohaline) convection occurring near vertical plane walls of a water tank. Many photographs of the convective flow patterns in the tank will be presented.