1,720,959 research outputs found
ADJOINT BASED SHAPE OPTIMIZATION OF SEMI-SUBMERGED INLETS AND DEVELOPMENT OF A NOVEL BOUNDARY LAYER DIVERTER
Full text linkIn this study, boundary layer ingesting and diverting submerged air inlets are design optimized with an adjoint-based optimization methodology based on RANS solu tions. The opensource SU2 software is employed for both RANS and adjoint solutions and for driving the gradient-based optimization. Total pressure recovery at the aerodynamic interface plane is taken as the main objective of the optimization, and the mass flow rate and the momentum distortion are closely monitored. It is first shown that the shape optimization of an inlet duct for a semi-submerged boundary layer ingesting inlet provides a limited performance increase since the performance of the inlet strongly depends on the amount of ingested boundary layer which develops over the upstream wall. The shape optimization of the upstream wall together with the inlet duct is next performed and is shown that the performance of the inlet is improved significantly. The optimum upstream wall obtained now provides a bound ary layer diverting inlet. Based on the optimum upstream wall configuration, a novel boundary layer diverter is then designed and similarly adjoint optimized. The design optimized novel boundary layer diverter is highly compact, flush to the surface and has a lower drag compared to the conventional diverter geometries. It provides a 2.4% increase in total pressure recovery and a 64% decrease in circumferential momentum distortion. It is also shown that further performance increase is achievable when the duct and the flush diverter are optimized together.Bu çalışmada sınır tabakası emen ve ıraksatan hava alıkları adjoint tabanlı yöntemler ile eniyilenmiştir. Akış ve adjoint analizler için açık kaynak SU2 yazılımı kullanılmıştır. Aerodinamik arayüz düzleminde elde edilen basınç toparlama katsayısının yükseltilmesi temel hedef olarak alınmış, kütle akış debisi ve momentum bozuntusu çalışma boyunca takip edilmiştir. Çalışmada öncelikle sadece hava alığı geometrisi
değiştirilerek eniyileme gerçekleştirildiğinde performans artışının kısıtlı olduğu görülmüştür. Bunun nedeni incelenen hava alığının önemli derecede sınır tabakasına maruz kalmasıdır. Hava alığı duvarları ile birlikte, emilen sınır tabakasının oluştuğu hava alığı girişi önündeki duvarlarda eniyilendiğinde, önemli mertebede performans artışı elde edilebilmiştir. Bu eniyilenmiş konfigürasyon sınır tabakasını hava alığı girişinden ıraksatmaktadır. Burada elde edilen sonuçlardan esinlenilerek özgün bir sınır tabaka ıraksatıcısı tasarlanmış ve adjoint tabanlı yöntem ile eniyilenmiştir. Bu ıraksatıcı kompakt yapıda, yüzeye silme şekilde tasarlanmıştır ve bilinen diğer ıraksatıcı geometrilerine göre daha düşük sürükleme kuvveti yaratmaktadır. Bu yüzeye silme olarak tasarlanmış ve eniyilenmiş ıraksatıcı ile hava alığı basınç toparlama katsayısında %2.4, çevresel bozuntu katsayısında ise %64 iyileşme sağlanmıştır. Bunun yanı sıra hava alığı ve silme sınır tabaka ıraksatıcısı birlikte eniyilendiğinde daha yüksek performansın elde edilebildiği gösterilmiştir.Ph.D. - Doctoral Progra
Yarı gömülü hava alığında pasif akış kontrolü.
No full textSubmerged intake designs with high compactness provide lower radar cross sectional area, less noise, higher packaging e ffciency and lower drag compared to the conventional designs. However, in such an intake fl ow exposed to strong adverse pressure gradients both in streamwise and circumferential directions due to the centerline curvature and high diff usion rate through the intake. Since, flow inside submerged intakes is very sensitive to the upcoming flow quality, it is very common to encounter with high total pressure distortion and low total pressure recovery inside boundary layer ingesting submerged intakes. Therefore, fl ow control methods used for reducing distortion and/or increasing pressure recovery can provide crucial advantageous to the intake designers. In this thesis, e ffect of vortex generators used as a passive fl ow control devices in a semi submerged boundary layer ingesting intake is computationally investigated with commercially available fl ow solver Fluent 14.0. In order to reach high confi dence about computational strategy and turbulence model selection validation study is conducted with an available experimental data in the open literature for a serpentine intake with and without vortex generator application. Validation results indicate that Validation results indicate that _ {u100000} ! SST provide more accurate results compared to the computations obtained with Spalart Allmaras and Realizable _ {u100000} " turbulence models. Base intake geometry developed for a flow control investigation is formed through the conventional design approaches. After computational investigation of performance of clean intake without flow control, effect of vortex generators on intake performance are investigated. Design variables of vortex generator sets are taken as vortex generator height relative to local boundary layer thickness, angle of incidence, number of vortex generators thus lateral spacing and distance between separation point and vortex generator set. Effect of the each design variable on intake performance are discussed in detail at the end of the work. Best vortex generator set provide 80% reduction in total pressure distortion with only 0:35% reduction in total pressure recovery at design condition. Moreover it is shown that, passive flow control ensure suffciently uniform flow reaching engine face such that possibility of the engine surge totally eliminated with only negligible decrease in pressure recovery for not only design condition but also whole angle of attack range that mostly encountered in flight envelope.M.S. - Master of Scienc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
ADJOINT-BASED SHAPE OPTIMIZATION FOR A SEMI-SUBMERGED ENGINE INLET
No full textIn this study, adjoint-based optimization is conducted for increasing the performance of a semi-submerged inlet exposing a large amount of boundary layer ingestion. Flow and adjoint solutions are conducted with the open-source software SU2. In the optimizations, the highlight area and its shape, overall diffusion ratio and vertical offset are kept constant and total pressure recovery is maximized. Results indicate that the surface modifications obtained with the optimization algorithm lead to a performance increase both in design and off-design conditions. It is further shown that this performance increase is mostly generated by diverting the upcoming boundary layer away from the inlet entrance.</p
ADJOINT-BASED SHAPE OPTIMIZATION FOR A SEMI-SUBMERGED ENGINE INLET
Full text linkIn this study, adjoint-based optimization is conducted for increasing
the performance of a semi-submerged inlet exposing a large amount of
boundary layer ingestion. Flow and adjoint solutions are conducted with
the open-source software SU2. In the optimizations, the highlight area
and its shape, overall diffusion ratio and vertical offset are kept
constant and total pressure recovery is maximized. Results indicate that
the surface modifications obtained with the optimization algorithm lead
to a performance increase both in design and off-design conditions. It
is further shown that this performance increase is mostly generated by
diverting the upcoming boundary layer away from the inlet entrance
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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