THREE-DIMENSIONAL NATURAL CONVECTION IN A POROUS MEDIUM ENCLOSED WITH CONCENTRIC INCLINED CYLINDERS

1982 ◽  
Author(s):  
Yasuyuki Takata ◽  
K. Fukuda ◽  
Shu Hasegawa ◽  
Kengo Iwashige ◽  
H. Shimomura ◽  
...  
Keyword(s):  
Porous Medium ◽  
Natural Convection ◽  
Three Dimensional

Three-dimensional natural convection in a confined porous medium heated from below

1979 ◽  
Vol 92 (4) ◽  
pp. 751-766 ◽  
Author(s):  
Roland N. Horne
Keyword(s):  
Porous Medium ◽  
Energy Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Governing Equations ◽  
Flow Situation ◽  
Definition Of ◽  
The Relationship

Previous analyses of natural convection in a porous medium have drawn seemingly contradictory conclusions as to whether the motion is two- or three-dimensional. This investigation uses numerical results to show the relationship between previous contending observations, and demonstrates that there exists more than one mode of convection for any particular physical configuration and Rayleigh number. In some cases, a particular flow situation may be stable even though it does not maximize the energy transfer across the system.The methods used are based on the efficient numerical solution of the governing equations, formulated with the definition of a vector potential. This approach is shown to be superior to formulating the equations in terms of pressure.For a cubic region the flow pattern at a particular value of the Rayleigh number is not unique and is determined by the initial conditions. In some cases there exist four alternatives, two- and three-dimensional, steady and unsteady.

scholarly journals Numerical study of the effects of natural convection in a thermoacoustic configuration

2019 ◽  
Vol 20 (8) ◽  
pp. 807
Author(s):  
Omar Hireche ◽  
Catherine Weisman ◽  
Diana Baltean-Carlès ◽  
Virginie Daru ◽  
Yann Fraigneau
Keyword(s):  
Porous Medium ◽  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
Acoustic Resonator ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Convection Flow ◽  
Conductivity Anisotropy

This study focuses on natural convection flows within a cylindrical guide containing a porous medium. This configuration is applicable to standing-wave thermoacoustic engines, usually composed of an acoustic resonator where a (short) stack (or porous medium) is inserted, with a heat exchanger placed at one of its ends. The resulting horizontal temperature gradient, when high enough, triggers the onset of an acoustic wave. Natural convection effects are usually neglected in thermoacoustics so that axisymmetry is often assumed. Here a 3D numerical study of natural convection flow is performed using a finite volume code for solving mixed Navier-Stokes and Darcy-Brinkman equations under Boussinesq approximation. The influence of the porous medium’s physical characteristics (permeability, thermal conductivity, anisotropy) on the flow and temperature fields is investigated. It is shown that such flows are fully three-dimensional and therefore can modify significantly starting as well as steady operating conditions of the thermoacoustic engine.

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