Convection in boxes: experiments

Stork, K.; Möller, Uwe

doi:10.1017/s0022112072000898

Cited by 147 publications

(51 citation statements)

References 5 publications

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“…He found that the rolls always form parallel to the shorter walls of the box, and when the gap thickness is less than the other dimensions of the box the rolls are of nearly square cross-section. These results were confirmed experimentally by Stork & Muller (1972). It was found in our studies that, in a manner similar to the three-dimensional box, the transverse vortices in the upper part of the moderate-gap annulus set-up parallel to the endwalls which form the shorter sides of the upper region of the annulus.…”

Section: Moderate-gap Annulus With Airsupporting

confidence: 87%

“…The cross-section of the vortices is similarly nearly square. Stork & Muller (1972) observed experimentally that an even or odd number of rolls can form in the rectangular box, but an even number is preferred. In the moderate-gap annulus, however, our numerical results indicate that only an even number of vortical cells form between the cells located at the endwalls.…”

Section: Moderate-gap Annulus With Airmentioning

confidence: 99%

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A numerical and experimental investigation of stability of natural convective flows within a horizontal annulus

1999

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This is an author's version published in: http://oatao.univ-toulouse.fr/20645To cite this version: A numerical and experimental study of buoyancy-driven flow in the annulus between two horizontal coaxial cylinders at Rayleigh numbers approaching and exceeding the critical values is presented. The stability of the flow is investigated using linear theory and the energy method. Theoretical predictions of the critical Rayleigh number for onset of secondary flows are obtained for a wide range of radius ratio R and are verified by comparison with results of previous experimental studies. A subcritical Rayleigh number which provides a necessary condition for global flow stability is also determined. The three-dimensional transient equations of fluid flow and heat transfer are solved to study the manifestation of instabilities within annuli having impermeable endwalls, which are encountered in various applications. For the first time, a thorough examination of the development of spiral vortex secondary flow within a moderate gap annulus and its interaction with the primary flow is performed for air. Simulations are conducted to investigate factors influencing the size and number of post-transitional vortex cells. The evolution of stable three-dimensional flow and temperature fields with increasing Rayleigh number in a large gap annulus is also studied. The distinct flow structures which coexist in the large gap annulus at high Rayleigh numbers preceding transition to oscillatory flow, including transverse vortices at the end walls which have not been previously identified, are established numerically and experimentally. The solutions for the large-gap annulus are compared to those for the moderate-gap case to clarify fundamental differences in behaviour. Heat transfer results in the form of local Nusselt number distributions are presented for both the moderate-and large-gap cases. Results from a series of experiments performed with air to obtain data for validation of the numerical scheme and further information on the flow stability are presented. Additionally, the change from a crescent-shaped flow pattern to a unicellular pattern with centre of rotation at the top of the annulus is investigated numerically and experimentally for a Prandtl number of 100. Excellent agreement between the numerical and experimental results is shown for both Prandtl numbers studied. The present work provides, for the first time, quantitative three-dimensional descriptions of spiral convection within a moderate-gap annulus containing air, flow structures preceding oscillation in a large-gap annulus for air, and unicellular flow development in a large-gap annulus for large Prandtl number fluids.

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Section: Moderate-gap Annulus With Airsupporting

confidence: 87%

Section: Moderate-gap Annulus With Airmentioning

confidence: 99%

A numerical and experimental investigation of stability of natural convective flows within a horizontal annulus

1999

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“…On the other hand spatial structures of decreasing symmetry are observed, depending on both the Rayleigh number (the constraint or control parameter related to the temperature gradient) and the Prandtl number [3][4][5][6]. However [7,8].…”

mentioning

confidence: 99%

Hydrodynamic transitions to chaos in the convection of an anisotropic fluid

1986

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Abstract. -We present the first spontaneous sequence of hydrodynamic instabilities due to the evolution of the convective flow from the rest state toward chaos in an anisotropic fluid : a nematic liquid crystal subjected to an AC electric field. The resulting structures are of decreasing symmetry as the control parameter is gradually increased. The study of the streamlines allows the interpretation of the entire sequence by the evolution of the convective flow up to the onset of chaos. We show that the first important step in the flow evolution is the build up of a second mode of rotation which is associated with a pinching instability of the vortex lines. A simple picture is then proposed in order to describe the essential steps of a possible route to chaos, and which could be extended to other convective systems.

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“…electronic cooling, double-pane windows, heating and cooling of buildings, refrigerators, room ventilating, heat exchangers, solar collectors, environmental phenomena and so on. Several research are oriented toward the study of rectangular enclosures wherein the heat flow is typically unidirectional, i.e., the buoyancy is induced by imposing a heating either from the side or from below, as also performed in the general review works on natural convection in closed cavities by Stork et al [1] Ostrach [2], De Vahl Davis et al [3], Khalifa Bdul-Jabbar [4] and Oztop et al [5].…”

Section: Introductionmentioning

confidence: 99%

Natural convection in tilted rectangular cavities due to bidirectional temperature gradient

Benyoucef¹,

Zeroual²,

Benmoussa³

2017

IJHT

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The study by the CFD for a 3D natural convection in a tilted rectangular cavity filled by silicone oil at high Prandtl number has been compared to experimental results. A constant vertical temperature gradient has been performed by subjecting the horizontal walls to temperature Th and Tc; respectively. Other walls are adiabatic except the left small sidewall is differentially heating with temperature TA creating the horizontal temperature gradient. Different values of the lateral heating and the tilt with respect to the horizontal plane are imposed. The results draw dynamic maps. The influence of two factors (TA and ) on the flow pattern and on the convective heat transfer are analysed and discussed. The simulation flow pattern results are close to those obtained experimentally for treated cases with a minimum discrepancy between the both. A spectral analysis is done to show the fluctuations seen on the natural convective flow after the stability caused by the lateral heating and tilted angle; which based on the visualization of the amplitude as a function to the frequency. The results also show a significant impact on the flow fields and the heat transfer performance is improved.

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Convection in boxes: experiments

Cited by 147 publications

References 5 publications

A numerical and experimental investigation of stability of natural convective flows within a horizontal annulus

A numerical and experimental investigation of stability of natural convective flows within a horizontal annulus

Hydrodynamic transitions to chaos in the convection of an anisotropic fluid

Natural convection in tilted rectangular cavities due to bidirectional temperature gradient

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