Computational Fluid Dynamics Based Optimal Design of Vertical Axis Marine Current Turbines
Abstract Marine turbines are being increasingly used to harness kinetic energy of water and convert it into other useful forms of energy. Widespread commercial acceptability of these machines depends upon their efficiency. This largely depends upon the geometric features of the marine turbines such as number of blades, shape of blades etc. Researchers have been using experimental facilities to optimise these machines for maximum power generation. With the advent of advanced computational techniques, it has now become possible to numerically simulate the flow of water in the vicinity of marine turbines and monitor their performance output. In this work Computational Fluid Dynamics (CFD) based techniques have been used to analyse the effects of number of blades within the stator and rotor, of an in-house built Vertical Axis Marine Current Turbine (VAMCT), on the performance output of the turbine. Furthermore, an effort has been put forward towards better understanding of the flow structure in the vicinity of the blades during transient interaction between rotor and stator blades. This study provides vital information with regards to the flow sensors’ requirements and placements in order to monitor various blade configurations of a VAMCT in real world. The results of this study show that the torque output from a VAMCT is a strong function of blade configurations and there is a significant degradation in the performance output of marine turbines as the inequality between the number of rotor and stator blades increases. Hence, CFD has the potential to optimise the design of marine turbines and can be used as a potential modelling tool in the near future for on-line health monitoring of such systems.
Effect of blade vortex interaction on performance of Darrieus-type cross flow marine current turbine
In this work, in-house computational fluid dynamics (CFD) code was utilized to simulate a cross-flow vertical-axis marine current turbine (straight-bladed Darrieus type). Particular emphasis was placed on the influence of interaction between vortices and blades on hydrodynamic performance. A physical transient-rotor–stator model with a sliding mesh technique was used to capture changes in flow field at a particular time step. The Spalart–Allmaras turbulence model was adopted for the turbulence. For a Darrieus-type marine current turbine, hydrodynamic characteristics such as power coefficient and flow behavior were then numerically investigated. The results suggest that vortices shed from previous blade passages and the close encounter of a rotor blade with these vortices can cause a variation in performance for this type of turbine during operation at different tip speed ratios.
The Bastille: A History of a Symbol of Despotism and Freedom
This book is both an analysis of the Bastille as cultural paradigm and a case study on the history of French political culture. It examines in particular the storming and subsequent fall of the Bastille in Paris on July 14, 1789 and how it came to represent the cornerstone of the French Revolution, becoming a symbol of the repression of the Old Regime. Lusebrink and Reichardt use this semiotic reading of the Bastille to reveal how historical symbols are generated; what these symbols’ functions are in the collective memory of societies; and how they are used by social, political, and ideological groups.

To facilitate the symbolic nature of the investigation, this analysis of the evolving signification of the Bastille moves from the French Revolution to the nineteenth century to contemporary history. The narrative also shifts from France to other cultural arenas, like the modern European colonial sphere, where the overthrow of the Bastille acquired radical new signification in the decolonization period of the 1940s and 1950s. The Bastille demonstrates the potency of the interdisciplinary historical research that has characterized the end of this century, combining quantitative and qualitative approaches, and taking its methodological tools from history, sociology, linguistics, and cultural and literary studies.