A dynamic convergence control scheme for the solution of the radial equilibrium equation in through-flow analyses

One of the most frequently encountered numerical problems in scientific analyses is the solution of non-linear equations. Often the analysis of complex phenomena falls beyond the range of applicability of the numerical methods available in the public domain, and demands the design of dedicated algorithms that will approximate, to a specified precision, the mathematical solution of specific problems. These algorithms can be developed from scratch or through the amalgamation of existing techniques. The accurate solution of the full radial equilibrium equation (REE) in streamline curvature (SLC) through-flow analyses presents such a case. This article discusses the development, validation, and application of an 'intelligent' dynamic convergence control (DCC) algorithm for the fast, accurate, and robust numerical solution of the non-linear equations of motion for two-dimensional flow fields. The algorithm was developed to eliminate the large extent of user intervention, usually required by standard numerical methods. The DCC algorithm was integrated into a turbomachinery design and performance simulation software tool and was tested rigorously, particularly at compressor operating regimes traditionally exhibiting convergence difficulties (i.e. far off-design conditions). Typical error histories and comparisons of simulated results against experimental are presented in this article for a particular case study. For all case studies examined, it was found that the algorithm could successfully 'guide' the solution down to the specified error tolerance, at the expense of a slightly slower iteration process (compared to a conventional Newton-Raphson scheme). This hybrid DCC algorithm can also find use in many other engineering and scientific applications that require the robust solution of mathematical problems by numerical instead of analytical means

An Authorisation Scenario for S-OGSA

The Semantic Grid initiative aims to exploit knowledge in the Grid to increase the automation, interoperability and flexibility of Grid middleware and applications. To bring a principled approach to developing Semantic Grid Systems, and to outline their core capabilities and behaviors, we have devised a reference Semantic Grid Architecture called S-OGSA. We present the implementation of an S-OGSA observant semantically-enabled Grid authorization scenario, which demonstrates two aspects: 1) the roles of different middleware components, be them semantic or non-semantic, and 2) the utility of explicit semantics for undertaking an essential activity in the Grid: resource access control

S-OGSA as a Reference Architecture for OntoGrid and for the Semantic Grid

The Grid aims to support secure, flexible and coordinated resource sharing through providing a middleware platform for advanced distributing computing. Consequently, the Grid’s infrastructural machinery aims to allow collections of any kind of resources—computing, storage, data sets, digital libraries, scientific instruments, people, etc—to easily form Virtual Organisations (VOs) that cross organisational boundaries in order to work together to solve a problem. A Grid depends on understanding the available resources, their capabilities, how to assemble them and how to best exploit them. Thus Grid middleware and the Grid applications they support thrive on the metadata that describes resources in all their forms, the VOs, the policies that drive then and so on, together with the knowledge to apply that metadata intelligently

Managing semantic Grid metadata in S-OGSA

Grid resources such as data, services, and equipment, are increasingly being annotated with descriptive metadata that facilitates their discovery and their use in the context of Virtual Organizations (VO). Making such growing body of metadata explicit and available to Grid services is key to the success of the VO paradigm. In this paper we present a model and management architecture for Semantic Bindings, i.e., firstclass Grid entities that encapsulate metadata on the Grid and make it available through predictable access patterns. The model is at the core of the S-OGSA reference architecture for the Semantic Grid

Architectural Patterns for the Semantic Grid

The Semantic Grid reference architecture, S-OGSA, includes semantic provisioning services that are able to produce semantic annotations of Grid resources, and semantically aware Gridservices that are able to exploit those annotations in various ways. In this paper we describe the dynamic aspects of S-OGSA by presenting the typical patterns of interaction among these services. A use case for a Grid meta-scheduling service is used to illustrate how the patterns are applied in practice

Athens by Sound

Architecture is not only that which is built. Architecture is made up of different aspects, both material and immaterial. The atmosphere, the sounds, the smells, the possibility of interaction between human bodies: these all constitute characteristics of space, characteristics that are assuming an increasing importance within architectural research worldwide. Within this field of thought about “Architecture Beyond Building”, we focus on one particular non-material spatial phenomenon that lies ‘beyond the built’: sound. We have created, thus, an interactive sonic map of Athens, which presents, in an unexpected way, fragments of the atmosphere of the city. What would a non-visual map look like? What would it feel like if you wandered within a forest of headphones, playing sounds from different places in Athens? How would it feel if you found yourself in a ‘map’ that only appeared when you walked in it? What would it be like if the map only appeared when you invited one more person to be with you? The Greek pavilion addresses these questions through an atmospheric interactive ‘game’, presenting fragments of sounds and visual sequences of Athens. The visitor recreates the space around him through his own presence and movement. The map appears only where he walks, and/or when he invites one more person to sit next to him. The bodies of the visitors react with one another and with the space itself, creating a dynamic, changing field. This walk in the pavilion takes you “out there”, through invisible Athens. The pavilion brings forth the aspects of architecture that are ‘beyond the material’: the ‘beyond the built’, the almost unreachable, elusive aspects of space, such as sound, non-visual senses, atmosphere. It challenges, thus, the limits of architecture, the limits of what can be mapped and re-located and what cannot. An edited collection by A. Karandinou, C. Achtypi, S. Giamarelos, including texts by: Ιntothepill, Katie Lloyd Thomas, Martin Parker, Panayiotis Tournikiotis, Mark Wigley, Dorian Wiszniewski, Leslie Kavanaugh, Stephen Cairns, Jonathan Hill, Vassilis Ganiatsas, Anastasios Kotsiopoulos, Constance Classen, Stavros Stavrides, Ole Bouman, William Mitchell, Richard Coyne, Neil Spiller, Kas Oosterhuis, Nora Schueler, Zissis Kotionis, Stelarc, Andreas Angelidakis, Aristide Antonas, Slavoj Žižek, Nikolaos Laskaris, Argyris Rokas, Andreas Kourkoulas, John Peponis, Yorgos Ioannou, Yorgos Tzirtzilakis, Konstantinos Vita, Dionyssis Kapsalis, United Visual Artists, Platon Rivellis, and Dimitris Filippidis. Contributors to the Greek National Participation to the 11th International Architecture Exhibition La Biennale di Venezia "Out there. Architecture beyond building" (2008) Organised by: Hellenic Ministry of Culture [yppo.gr] General Directorate of Modern Culture Directorate of Visual Arts Department for the Promotion of Contemporary Art Curators: Anastasia Karandinou Christina Achtypi Stylianos Giamarelos Video works by Intothepill net [intothepill.net] Artists: Yiannis Grigoriadis Yiannis Isidorou Lina Theodorou Sound Recording / Sound Design Dimitris Miyakis [movement.gr] Vangelis Lympouridis Exhibition Graphics / Catalogue Design Company [company-london.com] Design and Implementation of interactive environment 2monochannels [2monochannels.com] Audiovisual and interactive systems design / acoustic design / construction supervision Iraklis Lampropoulos Giorgos Lampropoulos Software programming Vassilis Boukis Electronic subsystem design Michail Kritsotakis Electrical Design Giorgos Satolias Interconnection of interactive elements Vangelis Lympouridis [inter-axions.com] Dimitris Miyakis Light design L+DG lighting architects [lightingdg.com] Thomas Gravanis Christina Frangeti Construction Gavrilos Michalis [gavrilos.gr] Digital printing Polichromo [polichromo.com] Translations Rachel Howard Nikos Masourides Catalogue photographs Intothepill – Internet video platform Catalogue published by futura publications Marketing communication Chryssa Vrouzi Communication associate Katerina Stamidi Photographer Cathy Cunliffe [cathycunliffeΑΤgmail.com] For their financial and material support for the Greek participation at the 11th International Exhibition of Architecture, La Biennale di Venezia, we express our deepest thanks to the sponsors: Alexander S. Onassis Public Benefit Foundation [onassis.gr] Akzonobel [akzonobel.com] Carteco - Architectural Materials & Design [carteco.gr] L+DG Lighting Architects [lightingdg.com] Plaisio [plaisio.gr] Polichromo Advertising Applications [polichromo.com] iGuzzini illuminazione [iguzzini.com] Diathlasis Architectural Lighting [diathlasis.gr

The effect of upstream duct boundary layer growth and compressor blade lean angle variation on an axial compressor performance

The compressor of a gas turbine engine is extremely vulnerable on upstream duct- induced flow non-uniformities whether the duct is an engine intake or an interconnecting duct. This is justified by its position being literally an extension of the duct flow path, coupled to the fact that it operates under adverse pressure gradients. In particular, this study focuses on performance deviations between installed and uninstalled compressors. Test results acquired from a test bed installation will differ from those recorded when the compressor operates as an integral part of an engine. The upstream duct, whether an engine intake or an inter-stage duct, will affect the flow-field pattern ingested into the compressor. The case study presented here aims mostly at qualifying the effect of boundary layer growth along the upstream duct wall on compressor performance. Additionally, the compressor performance response on blade lean angle variation is also addressed, with the aim of acquiring an understanding as to how compressor blade lean angle changes interact with intake-induced flow non-uniformities. Such studies are usually conducted as part of the preliminary design phase. Consequently, experimental performance investigation is excluded at this stage of development, and therefore, computer-aided simulation techniques are used if not the only option for compressor performance prediction. Given the fact that many such design parameters need to be assessed under the time pressure exerted by the tight compressor development programme, the compressor flow simulation technique needs to provide reliable results while consuming the least possible computational time. Such a low computational time compressor flow simulation method, among others, is the two-dimensional streamline curvature (SLC) method, being also applied within the frame of reference of the current study. The paper is introduced by a brief discussion on SLC method. Then, a reference is made to the radial equilibrium equation, which is the mathematical basis of SOCRATES, a turbomachinery flow simulation tool that was used in this study. Subsequently, the influence of the upstream duct on the compressor inlet radial flow distribution is being addressed, with the aim of adjusting the compressor blade inlet lean angle, in order to minimize compressor performance deterioration. The paper concludes with a discussion of the results