Mamadou Lamine Sow, Joseph Sarr, Cheikh Mbow, Babacar Mbow, Bernard Claudet and Mamadou Mansour Kane
The purpose of this paper is to study the transient natural convection of a Newtonian fluid which develops in a closed spherical annulus delimited by two vertically eccentric…
Abstract
Purpose
The purpose of this paper is to study the transient natural convection of a Newtonian fluid which develops in a closed spherical annulus delimited by two vertically eccentric spheres by using a bispherical coordinates system. The inner sphere is heated by a heat flux of constant density and the outer one is maintained isothermal.
Design/methodology/approach
The transfer equations are written by using a bispherical coordinates system. The Navier‐Stokes equations are solved and coupled with the energy equation by using the alternating direction implicit (ADI) and the successive over relaxation (SOR) methods.
Findings
The study of the stream function and the Nusselt number shows that the convection motion is reinforced for the geometries characterized by positive values of the eccentricity with heat exchange increasing. The Nusselt number increases with the modified Rayleigh number. The heat exchange increases with the radius ratio. The results show that the steady state is reached faster when the modified Rayleigh number increases and the influence of the eccentricity is very low on the establishment of the steady state. The fluids flow depends strongly on the eccentricity and the modified Rayleigh number.
Research limitations/implications
Simulations are performed for modified Rayleigh numbers ranging from 103 to 106, for eccentricities varying between –0.6 and +0.6 and for radius ratio between 1.5 and 2.
Originality/value
The results of eccentricity and modified Rayleigh number effects in transient natural convection between vertically eccentric spheres have been displayed.
Details
Keywords
Senegal’s history since the nineteenth century has favored collective ownership and work, whether state-run cooperatives or community-based organizations (CBOs). This chapter…
Abstract
Senegal’s history since the nineteenth century has favored collective ownership and work, whether state-run cooperatives or community-based organizations (CBOs). This chapter first examines the history of resistance to cooperatives imposed by the French colonial administration and Senegal’s independent state until 1980. The primary separate community organizations were, and are, within daaras: communities based on Islamic spiritual principles. The chapter then explores today’s CBOs, many of which are faith-based, that resist neoliberal approaches to development, again, through community-based principles. CBOs have grown within the space that state control once occupied, and have as much do with indigenous structures and faith-based principles as they do with globally recognized models of development. These foundational philosophies shape the ways people organize themselves, choose their shared goals, and elect their leaders. To discuss contemporary trends in community organization, the chapter uses ethnographic examples from two present-day communities, one a faith-based daara and the other a five-village CBO. This history and contemporary examples show that locally grown organizations resist easy definitions of colonial, state, or neoliberal development, and take control over the ways they organize their communities.