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

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.

Height and stability of laminar plane fountains in a homogeneous fluid

“…The numerical data obtained here compares reasonably well with the scaling given by Campbell and Turner [6] and the virtual source model of Zhang and Baddour [7]. The Goldman and Jaluria [9] scaling is seen to produce significantly different results, which may be due to the use of a different method to determine the fountain height, or due to the geometry of their experimental rig. The constant of proportionality (C = 1.285) in the Eq.…”

“…(2) with C set to 1.75, the scaling of Goldman and Jaluria [9], z m ¼ 5:83Fr 0:88 , the small Fr virtual source scaling of Zhang and Baddour [7], Eq. (3) and the large Fr scaling of Zhang and Baddour, Eq.…”

“…Goldman and Jaluria [9] carried out an experimental investigation on plane turbulent fountains by blowing hot air vertically downward into a chamber and obtained z m ¼ 5:83 Fr 0:88 , by regression analysis. Recently, Lin and Armfield [10] investigated the effect of the Reynolds number on the height of plane fountains.…”

Impinging plane fountains in a homogeneous fluid

“…This definition is similar to that used by Goldman and Jaluria [21] in their experiments on free fountains. Fig.…”

Experimental Studies for the characterization of the mixing processes in negative buoyant jets

“…Many studies were dedicated to vertical NBJs (e.g. Goldman and Jaluria 1986 [12], Campbell and Turner 1986 [9], Baines et al 1990 [13], Zhang et al 1998 [14], Davidson et al 2002 [15], Kaye et al 2007 [16]), and to inclined NBJs. The first one was possibly Bosanquet et al (1961) [17] and presented results for horizontal and 45° jets.…”