The unsteady flow of rotating fluids can exhibit some fascinating and elegant phenomena. The movement of fluid due to the rotation of an encompassing container, or the flow of fluid due to the rotation of a solid object immersed within a body of fluid, is of particular interest. Specifically, we focus on the dynamics resulting from an impulsive change in the rotation rate for both these internal and external flows, including the formation of boundary layers and their subsequent evolution, and the formation of instabilities. Using a combination of analytical, computational and experimental methods, we consider the flow induced by both a torus and a sphere, contained in an otherwise quiescent body of fluid, suddenly imparted with angular momentum. Our results agree well with previous work on this classical problem, known to exhibit a boundary-layer collision process, and we are able to take this problem further to consider the post-collision dynamics, encountering some new and exciting results, such as the development and propagation of a toroidal vortex pair, as a result of the boundary-layer collision, and instability of the radial jet. We also consider the flow within fluid-filled annular and toroidal containers, when there is a sudden change in the rotation rate of the container. Using both analytical and computational approaches, we explore the initial development of the impulsively generated axisymmetric boundary layer, its subsequent instability, and the larger scale transient features within this class of flows. This allows us to compare with and, perhaps, proffer an explanation for previously unexplained experimental results for the flow within a fluid-filled torus. In particular, we demonstrate that small imperfections in the torus surface, introduced during manufacture, can generate substantial secondary motion, considerably different from that which would arise if caused by centrifugal instabilities. This serves to highlight the often overlooked impact of small disturbances on the global dynamics of such flows.

Developing clean, sustainable energy systems is a pre-eminent issue of our time. Most projections indicate that combustion-based energy conversion systems will continue to be the predominant approach for the majority of our energy usage. Unsteady combustor issues present the key challenge associated with the development of clean, high-efficiency combustion systems such as those used for power generation, heating or propulsion applications. This comprehensive study is unique, treating the subject in a systematic manner. Although this book focuses on unsteady combusting flows, it places particular emphasis on the system dynamics that occur at the intersection of the combustion, fluid mechanics and acoustic disciplines. Individuals with a background in fluid mechanics and combustion will find this book to be an incomparable study that synthesises these fields into a coherent understanding of the intrinsically unsteady processes in combustors.

This Volume is the Proceedings of the IUTAM Symposium on Unsteady Separated Flows and Their Control held in Corfu, Greece, 18–22 June 2007. This was the second IUTAM Symposium on this subject, following the symposium in Toulouse, in April 2002. The Symposium consisted of single plenary sessions with invited lectures, - lected oral presentations, discussions on special topics and posters. The complete set of papers was provided to all participants at the meeting. The thematic sessions of this Symposium are presented in the following: Experimental techniques for the unsteady ow separation Theoretical aspects and analytical approaches of ow separation Instability and transition Compressibility effects related to unsteady separation Statistical and hybrid turbulence modelling for unsteady separated ows Direct and Large-Eddy Simulation of unsteady separated ows Theoretical/industrial aspects of unsteady separated ow control This IUTAM Symposium concerned an important domain of Theoretical and Applied Mechanics nowadays. It focused on the problem of ow separation and of its control. It achieved a uni ed approach regrouping the knowledge provided from theoretical, experimental, numerical simulation and modelling aspects for unsteady separated ows (incompressible and compressible regimes) and included ef cient control devices to achieve attenuation or suppression of separation. The subject - eas covered important themes in the domain of fundamental research as well as in the domain of applications.

A state-of-the art analysis of studies in the field of instability of flows, this book contains chapters by leading experts in fluid mechanics. One of the primary aims of the contributors is to determine fruitful directions for future advanced studies and research.