Effect of opposing buoyancy on the flow in free and wall jets

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Abstract
An experimental investigation is carried out into the characteristics of the velocity and thermal fields in free and wall jets in which the buoyancy force opposes the flow. The flow configuration considered is that of a negatively buoyant two-dimensional jet discharged adjacent to a vertical surface, as well as that discharged away from the boundaries of the region. Such convective flows are frequently encountered in heat-rejection processes and in enclosure fires, where, at various locations, the buoyancy force is upward while the flow is downward, resulting in negative buoyancy. An experimental system is developed to study the downward penetration of such jets in which the buoyancy force opposes the externally induced flow. The penetration distance is measured and related to the inflow conditions, particularly the temperature and velocity at the discharge location. A steady state is simulated by allowing the fluid to flow out of the enclosure at the open top. The velocity and temperature distributions are also measured, in order to understand the basic nature of such flows. Several other effects, such as the entrainment into the flow, are also considered in this study.