Search

This article numerically investigates the mixed convection of Bingham fluid in a narrow annulus. The temperature of the inner fixed cylinder ( θ i ) is higher than that of the outer one ( θ o ), which rotates at a constant angular velocity. An OpenFOAM solver, icoFoam, which works based on the finite volume method and the PISO algorithm, is modified to perform the simulations. The modified solver can solve unsteady heat transfer problems for Bingham fluids without using regularization methods. After validating the solver, it solves the problem in different conditions to show the effect of relevant parameters, such as Reynolds number, Bingham number, and aspect ratio, on the flow field and thermal performance of the enclosure for constant amounts of Grashof and Prandtl numbers. The results are presented as streamlines and isotherms, the size and shape of the unyielded regions, the local and mean Nusselt number, and the torque coefficient. The results demonstrate that the flow is steady at Re = 10 for all Bingham numbers, and a decrease in the Reynolds number may result in an unsteady flow depending on the value of the Bingham number. The flow's time history reveals that at a fixed Reynolds number, the flow shifts from periodic to steady-state by enhancing the Bingham number so that the flow becomes entirely steady for a given Bingham number. An interesting phenomenon is observed, the formation, movement, and disappearance of the plug zones (unyielded regions) for the periodic flow at Re = 1 and Bn = 5. [ABSTRACT FROM AUTHOR]

The present study aims to explore and explain the collapse of Pahlavi II using the destabilizing state theory. The reasons for the collapse of the said government have been analyzed based on historical documents and the destabilizing state theory. The paper portrays the subject by scrutinizing historical reasons and evidence found in credible sources. The fundamental issue is the identification of factors and explaining their role in the collapse. The indicators of the destabilizing state theory have been used to examine and explain various historical data. This research, based on library sources, memoirs, documents, and newspapers, and a descriptive-analytical qualitative method, aims to answer the question of ‘Which variables involved in the collapse of the Pahlavi II government are based on the destabilizing state theory and why did the Pahlavi government collapse?’ The results indicated that the variables involved in the collapse of the Pahlavi regime include: Legitimacy crisis, inefficiency in providing public services, law evasion accompanied by violence, coercion and suppression, infiltration of the SAVAK security forces, foreign interventions, especially by the United States, demographic pressure, migration from villages to cities and particularly to Tehran, superiority and decisiveness of revolutionary forces, undeveloped economic structure, rapid and erratic economic growth, and financial corruption. [ABSTRACT FROM AUTHOR]

Using Spragens's crisis theory, which oversees the understanding of political theories, the present article has explained the question of the development process and the nature of "constitutional theory" in Iran during the Qajar era. The purpose of this research is to apply Spragens's theory to understand the nature and explain the development process of constitutional theory in Iran. The results obtained from this research, based on the descriptive-explanatory method, show that the constitutionalism theory did not emerge in the last days of the movement; Rather, it has had a historical-evolutionary process. Regarding its nature, it can be said that the theory of constitutionalism was "the theory of the rule of law" and a movement to "establish freedom" and get rid of tyranny. The development process of this theory by using the theoretical approach of Spragens in the four steps of the problem and observation of disorder; causes of disorder; order and fantasy (rebuilding society); And the prescription phase will be explained. [ABSTRACT FROM AUTHOR]