Natural convection in an externally heated enclosure containing a local heat source

Zia, J. L.; Xin, Mingdao; Zhang, H. J.

doi:10.2514/3.169

Cited by 7 publications

(2 citation statements)

References 19 publications

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“…Despite the contributions of the foregoing experimental studies, much remains to be learned concerning the interaction of the plume motion with its surrounding, in particular with the top surface. To the authors' knowledge, no attempts have yet been made to numerically simulate thermal plumes inside rectangular vessels, except the recent ones of Peyret (1990) for double-diffusive convection and Zia, Xin & Zhang (1990) for an externally heated enclosure containing a local heat source of finite size. The restriction to two-dimensional flows precludes three-dimensional effects along the line source.…”

Section: Introductionmentioning

confidence: 99%

Unsteady confined buoyant plumes

Desrayaud

Lauriat

1993

J. Fluid Mech.

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Two-dimensional time-dependent buoyancy-induced flows above a horizontal line heat source inside rectangular vessels, with adiabatic sidewalls and top and bottom walls maintained at uniform temperature, are studied numerically. Transitions to unsteady flows are performed by direct simulations for various depths of immersion of the source in the central vertical plane of air-filled vessels. For a square vessel and a line source near the bottom wall, the numerical solutions exhibit a sequence of instabilities, called natural swaying motion of confined plumes, beginning with a periodic regime having a high fundamental frequency followed by a two-frequency locked regime. Then, broadband components appearing in the spectra indicate chaotic behaviour and a weakly turbulent motion arises via an intermittent route to chaos. For rectangular vessels of aspect ratio greater than 2 and depths of immersion greater than the width, the flow undergoes a pitchfork bifurcation. This symmetry breaking is driven by the destabilization of an upper unstable layer of stagnant fluid above the plume. Then a subcritical Hopf bifurcation occurs. On the other hand, if the depth of immersion is lower than the width of the vessel, a stable layer of fluid is at rest below the line source. Then penetrative convection sets the whole air-filled vessel in motion and an oscillatory motion of very low frequency arises through supercritical Hopf bifurcation followed by a two-frequency locked state.

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Section: Introductionmentioning

confidence: 99%

Unsteady confined buoyant plumes

Desrayaud

Lauriat

1993

J. Fluid Mech.

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“…Zia et al (1990) numerically analyzed the effect of a local heat source placed at the center of the adiabatic bottom surface in a square enclosure with hot left hand wall, cold right hand wall, and insulated top. The magnitude of the heat source was varied, and it was found that the hot wall Nusselt number decreased and the cold wall Nusselt number increased as the source intensity was increased.…”

Section: Bottom Heated Cavitiesmentioning

confidence: 99%

A review of modeling issues and analysis methods for the thermal response of cargoes transported in the Safe Secure Trailer subjected to fire environments

Howell

Larsen²

1998

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Buoyant plane plumes from heated horizontal confined wires and cylinders

Lauriat

Desrayaud

1994

Sadhana

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Two-dimensional computations are reported for timedependent laminar buoyancy-induced flows above a horizontal heated source immersed in an air-filled vessel. Two kinds of heated source were considered: a line heat source, modelled as a heat source term in the energy equation, and a heat-flux cylinder of small diameter. First, comparisons are presented for the results obtained for these two heated sources. Rather large discrepencies between the velocity fields appeared in the conduction regime due to the weak plume motion, while close agreements were found in the boundary layer regime. Nevertheless, same types of bifurcations occur with almost identical frequencies, whatever the Rayleigh number. It is concluded that for dimensions of the enclosures, which largely compared with the cylinder radius, the heat source term model is a promising way to study the behaviour of unsteady plumes owing to its simplicity, flexibility, and low computational costs. Second, transitions to unsteady flows were studied through direct flow simulations for various depths of immersion of a line heat source in the central vertical plane of a vessel. Different routes to chaos were shown to occur according to the aspect ratio of the vessel and the depth of immersion of the line source. Three distinct regimes were detected with different underlying physical mechanisms called natural swaying motion, penetrative convection and Rayleigh-Benard-like convection. The first bifurcations associated with these regimes are supercritical Hopf bifurcation, pitchfork bifurcation and subcritical Hopf bifurcation. Comparisons with experimental results of confined buoyant plumes above heated wires show very good agreement with laminar frequency correlations.

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Natural convection in an externally heated enclosure containing a local heat source

Cited by 7 publications

References 19 publications

Unsteady confined buoyant plumes

Unsteady confined buoyant plumes

A review of modeling issues and analysis methods for the thermal response of cargoes transported in the Safe Secure Trailer subjected to fire environments

Buoyant plane plumes from heated horizontal confined wires and cylinders

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