1,721,086 research outputs found
Supercritical reactive flow modeling in LRE thrust chambers
Full text linkThis CFD study is devoted to the characterization and the analysis of the flow field and heat loads evaluation in oxygen/methane liquid rocket engines. Thanks to CFD we obtain a compromise between details and experimental cost and it is possible a full scale engine analysis as support to the engine design phase. Our work is focused on the heat flux evaluation, hot gas and on flame structure in a thrust chamber. The importance of flame position leads to a study of mesh refinement of post tip. As consequence, a small recirculation zone near the post tip is identified and is studied to guarantee a stable flame also in term of position in the chamber. Also three large recirculation zones of hot gases are located in the combustion chamber and their presence assures, near the walls and the plate, the presence of high heat fluxes. We considered the usage of EOSs and a preliminary analysis was realised before the CFD simulations. Simple test cases are simulated and used to identify the best numerical strategy employ. Finally, we reproduced a simulation of the DEMO a regenerative cooled chamber LOX/methane, obtaining by combustion process simulation the heat flux at the chamber and nozzle walls
Classification of ignition regimes in HCCI combustion using computational singular perturbation
No full textThe computational singular perturbation (CSP) technique is applied as an automated diagnostic tool to classify ignition regimes encountered in homogeneous charge compression ignition (HCCI) engines. Various model problems representing HCCI combustion are simulated using high-fidelity computation with detailed chemistry for hydrogen-air system. The simulation data are then analyzed by CSP. In a homogeneous system, the occurrence of two branches of explosive eigenvalues characterizes chain-branching and thermal ignition. Their merging point serves as a good indicator of the completion of the explosive stage of ignition. However, the merging point diagnostics is insufficient to differentiate spontaneous ignition from deflagration. As an alternate method, the active reaction zones are first identified by the locus of minimum number of fast exhausted time scales (based on user-specified error thresholds). Subsequently, the relative importance of transport and chemistry is determined in the region ahead of the reaction zone. A new index IT, defined as the sum of the absolute values of the importance indices of diffusion and convection of temperature to the slow dynamics of temperature, serves as a criterion to differentiate spontaneous ignition from deflagration regimes. These diagnostic tools are applied to 1D and 2D ignition problems under laminar and turbulent mixture conditions, respectively, allowing automated detection of different ignition regimes at different times and location during the ignition events. The implication of the results in the context of modeling autoignition of nearly homogeneous turbulent mixtures is discussed. © 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved
sj-docx-1-jer-10.1177_14680874231200759 – Supplemental material for Development of correlation model for cavitating spray using Eulerian simulations
No full textSupplemental material, sj-docx-1-jer-10.1177_14680874231200759 for Development of correlation model for cavitating spray using Eulerian simulations by Xinlei Liu, Junjun Guo and Hong G. Im in International Journal of Engine Research</p
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
sj-docx-1-jer-10.1177_14680874221135278 – Supplemental material for DoE-ML guided optimization of an active pre-chamber geometry using CFD
No full textSupplemental material, sj-docx-1-jer-10.1177_14680874221135278 for DoE-ML guided optimization of an active pre-chamber geometry using CFD by Mickael Silva, Balaji Mohan, Jihad Badra, Anqi Zhang, Ponnya Hlaing, Emre Cenker, Abdullah S. AlRamadan and Hong G Im in International Journal of Engine Research</p
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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