Study on Three-Dimensional Natural Convection Induced by Variation in the Diagonal Positions of Four Cylinders with a Rectangular Array inside an Enclosure

A heightened awareness of the importance of natural convective cooling as a driving factor in design and thermal management of aircraft braking systems has emerged in recent years. As a result, increased attention is being devoted to understanding the buoyancy-driven flow and heat transfer occurring within the complex air passageways formed by the wheel and brake components, including the interaction of the internal and external flow fields. Through application of contemporary computational methods in conjunction with thorough experimentation, robust numerical simulations of these three-dimensional processes have been developed and validated. This has provided insight into the fundamental physical mechanisms underlying the flow and yielded the tools necessary for efficient optimization of the cooling process to improve overall thermal performance. In the present work, a brief overview of aircraft brake thermal considerations and formulation of the convection cooling problem are provided. This is followed by a review of studies of natural convection within closed and open-ended annuli and the closely related investigation of inboard and outboard subdomains of the braking system. Relevant studies of natural convection in open rectangular cavities are also discussed. Both experimental and numerical results obtained to date are addressed, with emphasis given to the characteristics of the flow field and the effects of changes in geometric parameters on flow and heat transfer. Findings of a concurrent numerical and experimental investigation of natural convection within the wheel and brake assembly are presented. These results provide, for the first time, a description of the three-dimensional aircraft braking system cooling flow field.

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Prandtl number effect on external natural convection heat transfer from irregular three-dimensional bodies

International Journal of Heat and Mass Transfer ◽

10.1016/0017-9310(89)90114-2 ◽

1989 ◽

Vol 32 (11) ◽

pp. 2075-2080 ◽

Cited By ~ 3

Author(s):

A.V. Hassani ◽

K.G.T. Hollands

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Prandtl Number ◽

Three Dimensional ◽

Convection Heat Transfer ◽

Natural Convection Heat Transfer ◽

Convection Heat

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Laminar natural convection about an isothermally heated sphere at small Grashof number

Journal of Fluid Mechanics ◽

10.1017/s0022112068001825 ◽

1968 ◽

Vol 34 (1) ◽

pp. 163-176 ◽

Cited By ~ 36

Author(s):

Francis E. Fendell

Keyword(s):

Natural Convection ◽

Three Dimensional ◽

Perturbation Expansion ◽

Outer Sphere ◽

Convective Transport ◽

Convection Flow ◽

Constant Density ◽

Boussinesq Model ◽

Grashof Number ◽

Recirculating Flow

The flow induced by gravity about a very small heated isothermal sphere introduced into a fluid in hydrostatic equilibrium is studied. The natural-convection flow is taken to be steady and laminar. The conditions under which the Boussinesq model is a good approximation to the full conservation laws are described. For a concentric finite cold outer sphere with radius, in ratio to the heated sphere radius, roughly less than the Grashof number to the minus one-half power, a recirculating flow occurs; fluid rises near the inner sphere and falls near the outer sphere. For a small heated sphere in an unbounded medium an ordinary perturbation expansion essentially in the Grashof number leads to unbounded velocities far from the sphere; this singularity is the natural-convection analogue of the Whitehead paradox arising in three-dimensional low-Reynolds-number forced-convection flows. Inner-and-outer matched asymptotic expansions reveal the importance of convective transport away from the sphere, although diffusive transport is dominant near the sphere. Approximate solution is given to the nonlinear outer equations, first by seeking a similarity solution (in paraboloidal co-ordinates) for a point heat source valid far from the point source, and then by linearization in the manner of Oseen. The Oseen solution is matched to the inner diffusive solution. Both outer solutions describe a paraboloidal wake above the sphere within which the enthalpy decays slowly relative to the rapid decay outside the wake. The updraft above the sphere is reduced from unbounded growth with distance from the sphere to constant magnitude by restoration of the convective accelerations. Finally, the role of vertical stratification of the ambient density in eventually stagnating updrafts predicted on the basis of a constant-density atmosphere is discussed.

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A numerical study on three-dimensional conjugate heat transfer of natural convection and conduction in a differentially heated cubic enclosure with a heat-generating cubic conducting body

International Journal of Heat and Mass Transfer ◽

10.1016/s0017-9310(00)00063-6 ◽

2000 ◽

Vol 43 (23) ◽

pp. 4229-4248 ◽

Cited By ~ 102

Author(s):

Man Yeong Ha ◽

Mi Jung Jung

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Conjugate Heat Transfer ◽

Numerical Study ◽

Three Dimensional ◽

Conducting Body

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Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.831.83 ◽

2016 ◽

Vol 831 ◽

pp. 83-91

Author(s):

Lahoucine Belarche ◽

Btissam Abourida

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Numerical Study ◽

Control Volume ◽

Vertical Wall ◽

Three Dimensional ◽

Maximum Temperature ◽

Cubical Enclosure ◽

Simplec Algorithm ◽

Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

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