Computation of compressible quasi-axisymmetric slender vortex flow and breakdown

The unsteady, compressible Navier-Stokes equations are used to compute and analyze compressible quasi-axisymmetric isolated vortices. The Navier-Stokes equations are solved using an implicit, upwind, flux difference splitting finite volume scheme. The developed three dimensional solver was verified by comparing its solution profiles with those of a slender, quasi-axisymmetric vortex solver for a subsonic, quasi-axisymmetric vortex in an unbounded domain. The Navier-Stokes solver is then used to solve for a supersonic, quasi-axisymmetric vortex flow in a configured circular duct. Steady and unsteady vortex-shock interactions and breakdown were captured. The problem was also calculated using the Euler solver of the same code; the results were compared with those of the Navier-Stokes solver. The effect of the initial swirl was investigated

Supersonic quasi-axisymmetric vortex breakdown

An extensive computational study of supersonic quasi-axisymmetric vortex breakdown in a configured circular duct is presented. The unsteady, compressible, full Navier-Stokes (NS) equations are used. The NS equations are solved for the quasi-axisymmetric flows using an implicit, upwind, flux difference splitting, finite volume scheme. The quasi-axisymmetric solutions are time accurate and are obtained by forcing the components of the flowfield vector to be equal on two axial planes, which are in close proximity of each other. The effect of Reynolds number, for laminar flows, on the evolution and persistence of vortex breakdown, is studied. Finally, the effect of swirl ration at the duct inlet is investigated

Israel\u27s 2001 Elections: Stability at Stake

The first and second issue of four volumes, this volume addresses elections in the Middle East. Contributors include: Assia Boutaleb, Judith Harik, Mona Markram-Ebeid, Christopher Parker, Curtis Francis Doebbler, Maye Kassem, Baskin Oran, Sami Zemni.https://fount.aucegypt.edu/faculty_book_chapters/2027/thumbnail.jp

Civil Society in Egypt Under the Mubarak Regime

There is no doubt that most of the structural changes that took place in Egypt since the 23rd July 1952 army-led coup were operated from the top of the political pyramid and not as an expression of a mass movement. The same holds true for the restricted political diversity in the Sadat period, or the controlled liberal policies in the Mubarak regime. The controlled mode of change from above, conforms with the Pharaonic Political system described by Gamal Hemdan. The ruler or head of state in Egypt always enjoyed unlimited authority that borders on deification, and the legal and constitutional framework of the Egyptian state endorses this situation from 1971. This study aims to present an informed vision of the development of civil society in Egypt under Mubarak. The growing number of the NGOs could be seen as a sign of democratization. However, in a case like Egypt, it is a move towards consolidating authoritarianism

Navier-Stokes Simulation of Quasi-Axisymmetric and Three-Dimensional Supersonic Vortex Breakdown

Computational simulation of supersonic vortex breakdown is considered for internal and external flow applications. The interaction of a supersonic swirling flow with a shock wave in bounded and unbounded domains is studied. The problem is formulated using the unsteady, compressible, full Navier-Stokes equations which are solved using an implicit, flux-difference splitting, finite-volume scheme. Solutions are obtained for quasi-axisymmetric and three-dimensional flows. The quasi-axisymmetric solutions are obtained by forcing the components of the flowfield vector to be equal on two axial planes, which are in close proximity to each other. For the flow in a bounded domain, a supersonic swirling flow is introduced into a configured circular duct. The duct is designed such that a shock wave intersects with the incoming swirling flow in the inlet portion. For the quasi-axisymmetric flow problem, a parametric study is performed which includes the effects of the Reynolds number, Mach number, swirl ratio and the type of exit-boundary conditions on the development and behavior of vortex breakdown. The effect of the duct wall boundary-layer flow on the vortex breakdown is also investigated. For the same duct geometry, three-dimensional effects are studied along with the effect of the duct wall boundary-layer flow. For the external flow application, a supersonic swirling jet is issued from a nozzle into a uniform supersonic flow of lower Mach number. For the quasi-axisymmetric flow problem, the effects of the Reynolds number and the type of downstream-boundary conditions are studied. For the three-dimensional flow problem, the effects of the grid fineness, grid-point distribution, grid shape and swirl ratio on the vortex breakdown are studied. The results show several modes of vortex breakdown such as no-breakdown, transient single-bubble breakdown, transient multi-bubble breakdown, periodic multi-bubble multi-frequency breakdown and helical spiral breakdown. In another application, a subsonic steady quasi-axisymmetric flow of an isolated slender vortex core is considered. The solution is obtained using a simple set of parabolic equations. The results are in excellent agreement with those of the full Navier-Stokes equations

Religion as a Security Threat

Religious extremism presents an ideological perspective found in most major religions and is currently associated with various forms of religiously motivated acts of violence. A conceptual framework is adopted to study the warning features of religious extremism and apply it to case studies of Nigeria, Uganda, and the Central African Republic (CAR). The application of a religious jihadism model to Christianity provides a comparative basis for assessing Islamic radical jihadism, helping to understand religion as a security threat, with particular reference to Christian contexts and examples. Using extremist rhetoric and the mobilization of Christian rituals, members of religious groups attempt to renegotiate their position in the public space within a society from which they are excluded due to political, social, and economic dynamics based on their exclusion. This study finds no significant difference between Islamic jihad and Christian jihad, as each seeks to politically exploit religion for political ends

Sufi islamic discourse in Africa: From the greatest jihad to the establishment of the african caliphate

© 2020 by the author. Licensee MDPI, Basel, Switzerland. In the nineteenth century, African Muslim societies were marked by the emergence of a reformist Sufi Islamic discourse aimed at changing and moving away from traditional Islamic practices. Although this discourse was influenced, to some extent, by external sources of inspiration, it was linked to the local African context. This study demonstrates that the reformist discourse of major Sufi figures such as Sheikh Amadu Bamba in Senegal and Sheikh Usman Dan Fodio in Nigeria reflects a number of common features of Islamic reform in Africa, yet their reform programs were shaped by the conditions of the local context. This research contribution aims to understand the actual role that the discourse of Sufi spirituality played—and still does—in the religious, economic, and political life of Muslim societies in Africa. This study has shown that despite the prevailing belief that Sufi discourse does not tend to politicize as it tries to maintain a safe distance away from matters of politics and governance in order to achieve its message of moral and spiritual purity, it may turn into violent radicalism as embodied by the jihadist Sufi experience in West Africa

Islamic State and the Transformation of Islamic Discourse in the Middle East

The purpose of this paper is to highlight the origin and evolution of the Islamic State (IS) with special focus on the root causes that helped construct its Islamic narrative, such as the idea of..