Conjugate Natural Convection in a Square Cavity Heated From Below

2004 ◽  
Author(s):  
F. Sa´nchez ◽  
F. Solorio ◽  
Ruben A´vila
Keyword(s):  
Steady State ◽  
Natural Convection ◽  
Velocity Field ◽  
Two Dimensional ◽  
Square Cavity ◽  
Conjugate Natural Convection ◽  
Natural Convection Problem ◽  
Energy Equations ◽  
Volume Method ◽  
Lateral Walls

This paper presents numerical results for two-dimensional steady-state natural convection in a square cavity. The upper and lower walls are kept at different constant temperatures, whereas the lateral walls have certain thickness and thermal conductivity and are externally insulated. Under these conditions we deal with a conjugate natural convection problem in which the heat conduction in the lateral walls is coupled with the internal convection. The continuity, momentum and energy equations were solved by using the finite volume method. The results here presented include: (i) the temperature distribution in the lateral walls and in the fluid, (ii) the velocity field, and (iii) the average Nusselt number at the upper and lower walls. It was found that the steady state fluid flow is strongly dependent on the initial temperature condition, when the fluid is initially at rest. The PIV technique allowed us to get some experimental data by measuring the velocity field in a two-dimensional square cavity. A good agreement between numerical and experimental results was found.

Turbulent Natural Convection in a Composite Enclosure Using the Thermal Non-Equilibrium Model

2016 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Caio B. Masciarelli
Keyword(s):  
Natural Convection ◽  
Solid Phase ◽  
Porous Matrix ◽  
Working Fluid ◽  
Square Cavity ◽  
Turbulent Natural Convection ◽  
Solid Region ◽  
Energy Equations ◽  
Volume Method ◽  
Non Equilibrium

Turbulent natural convection in a two-dimensional horizontal composite square cavity is numerically analyzed using the finite volume method and the thermal non-equilibrium approach. Distinct energy equations for the working fluid and for the porous matrix are proposed reflecting different energy balances for each phase. The composite square cavity is formed by three distinct regions, namely, clear, porous and solid region. It was found that the fluid begins to permeate the porous medium for values of Ra greater than 10^6. Nusselt number values show that for the range of Ra analyzed there are no significant variation between the laminar and turbulent model solution. When comparing the effects of Ra and Da on Nu, results indicate that the solid phase properties have a greater influence in enhancing the overall heat transferred trough the cavity.

scholarly journals Numerical investigation of natural convection with the presence of surface roughness or complex geometries

2020 ◽  
Vol 330 ◽  
pp. 01028
Author(s):  
Mohamed Elamine GHEDHAB ◽  
Ikram EL ABBASSI ◽  
Rafik ABSI ◽  
Yannick MELINGE
Keyword(s):  
Surface Roughness ◽  
Natural Convection ◽  
Numerical Study ◽  
Energy Performance ◽  
Complex Geometries ◽  
Two Dimensional ◽  
Square Cavity ◽  
Ansys Fluent ◽  
Building Facades ◽  
Energy Equations

This paper represents a numerical study of mixed convection conduction in enclosed two- dimensional square cavity differentially heated. Complex geometries are designed on a vertical partitioned wall, those geometries are applied to building facades aiming to improve the overall energy performance of the building. Our numerical results are based on the resolution of coupled momentum and energy equations using Ansys Fluent. Numerical study has been performed for different values of the Rayleigh number. Triangular geometry element will be considered in the middle wall. Finally, temperature profile and streamlines will be analyzed to examine the influence of this studied shape.

Numerical analysis and explore of asymmetrical fluid flow in a two-sided lid-driven cavity

2020 ◽  
Vol 14 (3) ◽  
pp. 7269-7281
Author(s):  
El Amin Azzouz ◽  
Samir Houat
Keyword(s):  
Velocity Ratio ◽  
Two Dimensional ◽  
Lower Side ◽  
Square Cavity ◽  
Driven Cavity ◽  
Parallel Motion ◽  
Bottom Cavity ◽  
Secondary Vortices ◽  
Volume Method ◽  
Fluid Characteristics

The two-dimensional asymmetrical flow in a two-sided lid-driven square cavity is numerically analyzed by the finite volume method (FVM). The top and bottom walls slide in parallel and antiparallel motions with various velocity ratio (UT/Ub=λ) where |λ|=2, 4, 8, and 10. In this study, the Reynolds number Re1 = 200, 400, 800 and 1000 is applied for the upper side and Re2 = 100 constant on the lower side. The numerical results are presented in terms of streamlines, vorticity contours and velocity profiles. These results reveal the effect of varying the velocity ratio and consequently the Reynolds ratio on the flow behaviour and fluid characteristics inside the cavity. Unlike conventional symmetrical driven flows, asymmetrical flow patterns and velocity distributions distinct the bulk of the cavity with the rising Reynolds ratio. For λ>2, in addition to the main vortex, the parallel motion of the walls induces two secondary vortices near the bottom cavity corners. however, the antiparallel motion generates two secondary vortices on the bottom right corner. The parallel flow proves affected considerably compared to the antiparallel flow.

Numerical Investigation of the Onset of Steady Natural Convection in a Square Cavity Partially Filled With a Single Porous Block

2014 ◽  
Author(s):  
Vinicius Daroz ◽  
Silvio L. M. Junqueira ◽  
Admilson T. Franco ◽  
José L. Lage
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Critical Rayleigh Number ◽  
Contour Plot ◽  
Viscous Effects ◽  
Square Cavity ◽  
Heterogeneous Model ◽  
Porous Block ◽  
Vertical Walls ◽  
Volume Method

The critical Rayleigh number at the onset of natural convection within a square cavity filled with a centralized porous block was investigated. The porous medium is modeled by using the heterogeneous model and the governing equations are solved for each phase separately. The thermal gradient is applied from the bottom to the top horizontal walls while the vertical walls are kept adiabatic. The amount of solid within the cavity was kept constant by fixing both external and internal porosity in 36% and 40%, respectively. The equations are solved using the Finite Volume Method and the interpolation scheme for the convective terms is the Hybrid Scheme. For the pressure-velocity coupling, the SIMPLEC method is used. The effects on the conductive-convective regime transition, reads critical Rayleigh Number, characterized by the average Nusselt number and the heatlines contour plot, was investigated by varying the Rayleigh number and the porous block permeability. The results show that the so called critical Rayleigh number is affected by the block permeability. As the permeability decreases, the flow tends to recirculate around the block being squeezed against the cavity walls and therefore, more susceptible to viscous effects. A correlation to the critical Rayleigh number is presented as a function of the agglomerate permeability showing that the higher the permeability the lower the amount of energy required to trigger the convection.

Laminar Natural Convection Inside a Wavy Enclosure Heated From Top and Uniformly Cooled From the Bottom and Both Sides

2005 ◽  
Author(s):  
Amaresh Dalal ◽  
Manab Kumar Das
Keyword(s):  
Natural Convection ◽  
Simple Algorithm ◽  
Governing Equations ◽  
Square Cavity ◽  
Integral Forms ◽  
Nusselt Number Distribution ◽  
Laminar Natural Convection ◽  
Lower Temperature ◽  
Volume Method ◽  
Spatially Varying

In the present paper, natural convection inside a square cavity with one and three undulations on the top wall has been carried out. The top wall is heated by a spatially varying temperature and other three walls are kept constant lower temperature. The integral forms of the governing equations are solved numerically using finite-volume method in non-orthogonal body-fitted coordinate system. SIMPLE algorithm with higher-order up-winding scheme are used. The streamlines and isothermal lines are presented for different Rayleigh number (103-106) and a fluid having Prandtl number 0.71. Results are presented in the form of local and average Nusselt number distribution for two different undulations (1 and 3) with wave amplitude of 0.05.

A Numerical Study of Natural Convection in a Cavity With Two Fins Attached to Its Vertical Walls

2007 ◽  
Author(s):  
G. A. Sheikhzadeh ◽  
M. Pirmohammadi ◽  
M. Ghassemi
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Square Cavity ◽  
Vertical Walls ◽  
The Mean ◽  
Energy Equations ◽  
Rayleigh Numbers

Numerical study natural convection heat transfer inside a differentially heated square cavity with adiabatic horizontal walls and vertical isothermal walls is investigated. Two perfectly conductive thin fins are attached to the isothermal walls. To solve the governing differential mass, momentum and energy equations a finite volume code based on Pantenkar’s simpler method is developed and utilized. The results are presented in form of streamlines, isotherms as well as Nusselt number for Rayleigh number ranging from 104 up to 107. It is shown that the mean Nusselt number is affected by the position of the fins and length of the fins as well as the Rayleigh number. It is also observed that maximum Nusselt number occurs about the middle of the enclosure where Lf is grater the 0.5. In addition the Nusselt number stays constant and does not varies with width of the cavity (lf) when Lf is equal to 0.5 and Rayleigh number is equal to 104 and 107 as well as when Lf is equal to 0.6 and low Rayleigh numbers.

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