3D Buoyancy-Induced Flow and Entropy Generation of Nanofluid-Filled Open Cavities Having Adiabatic Diamond Shaped Obstacles

Buoyancy-induced flow occurs in the cavity between two corotating compressor disks when the temperature of the disks and shroud is higher than that of the air in the cavity. Coriolis forces in the rotating fluid create cyclonic and anticyclonic circulations inside the cavity, and—as such flows are three-dimensional and unsteady—the heat transfer from the solid surfaces to the air is difficult either to compute or to measure. As these flows also tend to be unstable, one flow structure can change quasi-randomly to another. This makes it hard for designers of aeroengines to calculate the transient temperature changes, thermal stresses, and radial growth of the disks during engine accelerations and decelerations. This paper reviews published research on buoyancy-induced flow in closed rotating cavities and in open cavities with either an axial throughflow or a radial inflow of air. In particular, it includes references to experimental data that could be used to validate cfd codes and numerical models.

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Buoyancy-induced flow, heat, and mass transfer in a porous annulus

Numerical Heat Transfer Part A Applications ◽

10.1080/10407782.2017.1359014 ◽

2017 ◽

Vol 72 (2) ◽

pp. 107-125 ◽

Cited By ~ 1

Author(s):

F. Moukalled ◽

J. Kasamani ◽

M. Darwish ◽

A. Hammoud ◽

M. Khamis Mansour

Keyword(s):

Mass Transfer ◽

Heat And Mass Transfer ◽

Flow Heat ◽

Induced Flow ◽

Buoyancy Induced Flow

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Experimental and numerical study of buoyancy-induced flow and heat transfer in an open annular cavity

International Journal of Heat and Mass Transfer ◽

10.1016/0017-9310(95)00300-2 ◽

1996 ◽

Vol 39 (10) ◽

pp. 2053-2066 ◽

Cited By ~ 9

Author(s):

Chetan P. Desai ◽

Kambiz Vafai

Keyword(s):

Heat Transfer ◽

Numerical Study ◽

Flow And Heat Transfer ◽

Induced Flow ◽

Buoyancy Induced Flow

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The Influence of Real Gas Radiation On the Stability and Development of Benard Convection in a Two-Dimensional Layer

Journal of Heat Transfer ◽

10.1115/1.4051499 ◽

2021 ◽

Author(s):

Brent W. Webb ◽

Vladimir Solovjov

Keyword(s):

Rayleigh Number ◽

Critical Rayleigh Number ◽

Radiative Heating ◽

Two Dimensional ◽

Gas Temperature ◽

Layer Depth ◽

Real Gas ◽

Gas Radiation ◽

Induced Flow ◽

Buoyancy Induced Flow

Abstract The influence of real gas radiation on the thermal and hydrodynamic stability is investigated in a two-dimensional layer of radiatively participating H2O and/or CO2 heated from below. The non-gray radiation effects of the two species are treated rigorously using a global spectral approach, the Spectral Line Weighted-sum-of-gray-gases model. The phenomena are explored by solving the full coupled laminar equations of motion, energy, and radiative transfer from the low-Rayleigh number, pure conduction-radiation regime through the onset of buoyancy-induced flow to the developed Bénard convection regime. The evolution of the thermal, velocity, and radiative heating fields is studied, and the critical Rayleigh number is characterized as a function of species mole fraction, average layer gas temperature, layer depth, wall emissivity, and the total gas pressure. It is found that participating radiation in the medium has the effect of stabilizing the layer, delaying transition to buoyancy-induced flow. The development of buoyancy-induced flow and temperature, along with the radiative heating are presented. It is found that the critical Rayleigh number in the radiatively participating gas layer can be more than an order of magnitude higher than the classical convection-only scenario. The onset of instability is found to depend on the species mole fractions, average gas temperature in the layer, wall emissivity, layer depth, and total pressure. Generally, all other variables being the same, H2O has a greater stabilizing influence on the layer than CO2.

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Measurement and Analysis of Buoyancy-Induced Heat Transfer in Aero-Engine Compressor Rotors

Volume 7C: Heat Transfer ◽

10.1115/gt2020-16219 ◽

2020 ◽

Author(s):

Richard W. Jackson ◽

Dario Luberti ◽

Hui Tang ◽

Oliver J. Pountney ◽

James A. Scobie ◽

...

Keyword(s):

Heat Transfer ◽

Three Dimensional ◽

Outer Region ◽

Conjugate Problem ◽

Radial Temperature ◽

Nusselt Numbers ◽

Induced Flow ◽

Aero Engines ◽

Inner Region ◽

Buoyancy Induced Flow

Abstract The flow inside cavities between co-rotating compressor discs of aero-engines is driven by buoyancy, with Grashof numbers exceeding 1013. This phenomenon creates a conjugate problem: the Nusselt numbers depend on the radial temperature distribution of the discs, and the disc temperatures depend on the Nusselt numbers. Furthermore, Coriolis forces in the rotating fluid generate cyclonic and anti-cyclonic circulations inside the cavity. Such flows are three-dimensional, unsteady and unstable, and it is a challenge to compute and measure the heat transfer from the discs to the axial throughflow in the compressor. In this paper, Nusselt numbers are experimentally determined from measurements of steady-state temperatures on the surfaces of both discs in a rotating cavity of the Bath Compressor-Cavity Rig. The data are collected over a range of engine-representative parameters and are the first results from a new experimental facility specifically designed to investigate buoyancy-induced flow. The radial distributions of disc temperature were collected under carefully-controlled thermal boundary conditions appropriate for analysis using a Bayesian model combined with the equations for a circular fin. The Owen-Tang buoyancy model has been used to compare predicted radial distributions of disc temperatures and Nusselt numbers with some of the experimentally determined values, taking account of radiation between the interior surfaces of the cavity. The experiments show that the average Nusselt numbers on the disc increase as the buoyancy forces increase. At high rotational speeds the temperature rise in the core, created by compressibility effects in the air, attenuates the heat transfer and there is a critical rotational Reynolds number for which the Nusselt number is a maximum. In the cavity, there is an inner region dominated by forced convection and an outer region dominated by buoyancy-induced flow. The inner region is a mixing region, in which entrained cold throughflow encounters hot flow from the Ekman layers on the discs. Consequently, the Nusselt numbers on the downstream disc in the inner region tend to be higher than those on the upstream disc.

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