1,721,175 research outputs found
High speed aerodynamics and flow control using porous plates
No full textMacManus, David G. - Associate SupervisorThe integrated design of supersonic intakes and flow control systems is critical for stable aero-engine operation across various flight conditions. Porous bleed systems play a key role in mitigating shock wave-boundary layer interactions, improving intake efficiency and stability range by removing the low-momentum portion of the incoming boundary layers. However, accurately simulating intakes with fully resolved bleed systems using computational fluid dynamics is costly, and existing porous wall models often lack the complexity to capture the intricate physics of bleed flows, limiting their predictive accuracy.
This research aims to enhance the aerodynamic understanding of porous plates with 90-degree bleed holes and to develop a refined porous wall model. Steady-state simulations were used to analyse porous plates under varying conditions, including different domain geometries, shock positions, and operating regimes.
Using the computational database generated from these simulations, a model using local performance characteristics of individual bleed holes was developed. Additionally, a surface model was formulated to account for the flow field at the inflow of each bleed hole, enabling the computation of features such as capture streamtubes, shock topologies, and separation patterns. The proposed porous wall model was implemented in ANSYS CFX using MATLAB and benchmarked against existing approaches from the literature.
The results of this comparison demonstrate major improvements over existing porous wall models, particularly during choked suction and within shock-affected regions. By incorporating discrete bleed actuation regions, local performance metrics, and accurate flow profiles at each hole, the proposed bleed model recreates the results of the simulation campaign and addresses major limitations of existing models, improving their flowfield predictions by a 13.5% on average.PhD in Aerospac
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Computational aerodynamics for open rotor tip vortex interaction noise prediction
Full text linkOpen rotor engines can provide fuel savings of up to twenty seven percent compared to
a modern high bypass turbofan engine. They were subject to intense research in the
1980s in response to the 1973 oil crisis. They have come back into consideration to
combat the strict environmental regulations currently imposed on the aviation industry
and to meet the ACARE 2020 requirements. Recent large scale European projects such
as DREAM and Clean Sky have included signi cant research on the open rotor since
their comeback.
Their major drawback is the noise levels generated when the wake and tip vortices of
the front rotor interact with the aft rotor. The noise generated from these interactions
is highly tonal which makes the open rotor prohibitively noisy.
The Unducted Fan (UDF) demonstrator engine was built in the 1980s by General Electric
in collaboration with NASA. During the design phase of this project a computer code
named CRPFAN was developed to predict the noise of open rotors. CRPFAN is used as
a representative preliminary design noise prediction tool and was the only representative
tool available to the author at the time of the project.
Included in CRPFAN is a vortex model which relies heavily on outdated empirical re-
lations. There is currently a better knowledge of tip vortex properties relative to when
the code was created. However, there has been no signi cant study on how the speci c
parameters of a tip vortex relate to the noise of an open rotor or how to more accurately
predict the tip vortex parameters, which is what this project aims to do.
The rst part of the project developed methods to quantify how the tip vortex param-
eters relate to the noise generated by its interaction with the aft blade row. The next
step was to further develop the state of the art of tip vortex models. This is done using
basic analytical models integrated into CRPFAN and the use of Computational Fluid
Dynamics (CFD) to model the tip vortices.
CFD was used to develop bespoke tip vortex correlations which relate the tip vortex
parameters to the open rotor performance parameters such as the lift, thrust and power
coe cients. Correlations for the tip vortex axial velocity, trajectory, circulation and
core size have been developed and integrated into CRPFAN with a detailed analysis of
their performance relative to the current state of the art included.
This thesis includes recommendations to improve the tip vortex models such as taking
into account the spatial orientation of the vortex, inclusion of a vortex axial velocity
component and how strip theory codes can under predict the noise
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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