Turbulent heat transfer and coherent vortical structures in gas turbine film cooling

Unsteady coherent structures and turbulent heat transfer in a film cooling flow is studied by using detached eddy simulation (DES). Detailed computations for an inclined jet in crossflow by a single row of 35 degree round holes on a flat plate were performed at blowing ratios of 0.5 and 1.0, and a density ratio of 2.0. The correlation between the coherent vortical structures and the unsteady heat transfer is carefully examined. The instantaneous flow fields and heat transfer distributions are found to be characterized by the formation of large coherent vortical structures. These structures enhance the thermal mixing process and turbulent heat transfer to the wall. From the inspection of both unsteady adiabatic film cooling effectiveness and heat transfer coefficient, these two are found to have substantial local fluctuations due to the large unsteadiness of coherent structures. The fluctuation of the adiabatic effectiveness and heat transfer coefficient, for example, can be as high as 15 and 50 percent of the time-mean value, respectively. It could result in the detrimental effect on film cooling performance.

Victims, Violence and Voice: Transitional Justice, Oral History and Dealing with the Past

Transitional justice is concerned with the legal and social processes established to deal with the legacy of violence in post-conflict and post-authoritarian contexts. These processes are essentially “creatures of law” – they are established by statute, their work is molded and shaped by lawyers, and their outcomes are benchmarked against what is or is not acceptable in domestic and international law. Concerns have mounted in recent years about the dominance of legalism within the field and the instrumentalization of those most directly affected by past violence. A commonly prescribed – but as yet largely empirically untested – corrective is that transitional justice theory and practice must become more open to interdisciplinary insights and perspectives. The interview – in different guises, contexts and settings – is at the heart of most transitional justice processes. As a historian now working in a School of Law I reflect in this article on the theoretical and practical intersections between law, history, and the interview. Drawing on more than 200 interviews concerning the Northern Ireland conflict and six other international case studies I concentrate in particular on interview-based initiatives that purport to be “victim-centered”. Having identified three interrelated risks - the manipulation of victim voice by vested interests, the affording of authority to particular voices, and the reification or “freezing” of identity - and having related these to the constraints of legal mechanisms and a wider failure to manage victims’ expectations, I argue that a greater familiarity with oral history theory and praxis can usefully illuminate the tensions between legal and historical approaches to engaging voice, and ultimately offer guidance to the shared challenge of victim-centered transitional justice.

Periodically loaded 1-D metallodielectric electromagnetic bandgap structures for miniaturisation and bandwidth enhancement

Periodic loading of 1-D metallodielectric electromagnetic bandgap (MEBG) structures has been rigorously investigated. Miniaturised and broadband MEBG structures have been produced by means of periodically loading a dipole array. A study has been carried out with regard to the loading mechanism, the number of stubs, the topology of the structure and the order of loading. Simulations have been carried out using a method of moments based software. First order uniform loading stubs have yielded a significant size reduction of the MEBG array and the bandwidth has doubled. Good agreement between simulations and measurements has been achieved. The current distribution on the proposed structure has been studied, yielding valuable insight. An interdigital topology has resulted in further miniaturisation and bandwidth enhancement. Fractal-type arrays have been produced after applying second order loading. A maximum miniaturisation of 2.5:1 has been achieved.

Women's History Review:Special Issue: Family, Private Life and Sexuality

A collection of essays based on the conference of the International Federation for Research in Women's History which was held in Queen's University Belfast in August 2003.