scholarly journals The Role of Compressibility in the Linear-stability of Centrifugal Buoyancy-induced Flow

2020 ◽  
Author(s):  
Deepak Saini ◽  
Richard Sandberg
Keyword(s):  
Linear Stability ◽  
Induced Flow ◽  
Buoyancy Induced Flow

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

2017 ◽  
Vol 72 (2) ◽  
pp. 107-125 ◽  
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

scholarly journals The role of thermal diffusion, particle clusters, hydrodynamic and magnetic forces on the flow behaviour of magneto-polymer composites

2021 ◽  
Vol 379 (2205) ◽  
pp. 20200302 ◽  
Author(s):  
William R. Suarez-Fernandez ◽  
Juan D. G. Duran ◽  
Modesto T. Lopez-Lopez
Keyword(s):  
Polymer Composites ◽  
Magnetic Particles ◽  
Hydrodynamic Forces ◽  
Particle Movement ◽  
Dimensionless Numbers ◽  
Anionic Polymer ◽  
Experimental Conditions ◽  
Magnetic Attraction ◽  
Induced Flow

In this paper, we study the shear-induced flow of magneto-polymer composites, consisting of dispersions of magnetic particles in solutions of polymers, as a competition between the colloidal forces amid particles and their bulk transport induced by the hydrodynamic forces. For this aim, we analyse the role of different experimental parameters. Firstly, by using only solutions of a well-known anionic polymer (sodium alginate), we provoke a moderate hindering of particle movement, but keeping the liquid-like state of the samples. On the contrary, a gel-like behaviour is conferred to the samples when a cationic polymer (chitosan) is additionally added, which further reduces the particle movement. We analyse the effect of an applied magnetic field, which is opposed to particle transport by hydrodynamic forces, by inducing magnetic attraction between the particles. We perform the analysis under both stationary and oscillatory shear. We show that by using dimensionless numbers the differences between samples and experimental conditions are emphasized. In all cases, as expected, the transport of particles driven by bulk hydrodynamic forces dominates at high values of the shear rate. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.

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

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.

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

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.

Calculation Of Vertical Parallel Wall Fires With Buoyancy-induced Flow

2000 ◽  
Vol 6 ◽  
pp. 671-682 ◽  
Author(s):  
H. Wang ◽  
Jose Torero ◽  
P. Joulain
Keyword(s):  
Parallel Wall ◽  
Induced Flow ◽  
Buoyancy Induced Flow
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