1,720,958 research outputs found
A HIGH-PERFORMANCE CODE FOR ANALYZING LOSS TRANSPORT EQUATIONS IN HIGH-FIDELITY SIMULATIONS
No full textThe subject of the present paper is the development of a general procedure to calculate the terms of the total pressure transport equations using a High-Performance Data Analytics (HPDA), based on Proper Orthogonal Decomposition (POD) and leveraging on High Performance Computing. This method is applied to data obtained from high fidelity simulations of low pressure turbine (LPT) blades in order to separate the different loss contributions and to visualize the associated structures to the fluid dynamics phenomena that occur inside the passage. This procedure is developed in Python environment because it easily allows parallel computing. This paper discusses the mathematical framework behind the decomposition of total pressure transport equation and its implementation in Python. The scalability tests are performed for two exemplary datasets and compared to previous implementation showing a considerable speed-up. The procedure applied to Large Eddy Simulation (LES) data shows significant improvement over traditional approaches. It provides more detailed information about the phenomena associated with the generation of losses in the turbine blades, allowing for quick identification of where these losses occur. The HPDA code can be applied to all high fidelity simulations (LES and DNS) in order to get more information from simulations that are extremely expensive, allowing the full exploitation of such large datasets. In addition, to demonstrate the ease of code’s implementation, the data obtained from the POD are compared with data obtained from Fourier decomposition to validate the procedure. The procedure is open access and available in an online repository
Numerical Study of the Interaction between the Sealing Flow Rate and the Main Flow in a Gas Turbine Stage
No full textThis paper focuses on the interaction process between the main and cavity flows in a gas turbine. To this purpose, Reynolds-Averaged Navier-Stokes (RANS) simulations are conducted on the full stage with including the cavity system. Different sealing flow rates injected into the cavity are simulated to study different operating conditions. The study employs a robust computational fluid dynamics (CFD) framework (Cadence) to perform the RANS simulations, leveraging on turbulence models to capture the complex interactions due to the cavity. The aim is to validate the numerical approach in order to provide an accurate flow field within the cavity. To this purpose, the numerical model is compared against experimental data and a good agreement is found. The RANS simulations are validated with experimental data and they allow us to study the time-mean flow field and to calculate an estimate of the time-mean performances of the machine. The increase in the mass flow rate injected into the cavity leads to a local increase in losses near the hub and also to a local variation of the flow angle, with the effect of reducing the aerodynamic efficiency of the downstream blade. This study provides additional data about the main channel-cavity interaction phenomena that may be useful to designers to improve gas turbine performance
SEALING FLOW RATE EFFECTS ON UNSTEADY LOSS PRODUCTION IN A LOW PRESSURE TURBINE STAGE
No full textEfforts to increase efficiency in aircraft and power generation turbines have raised turbine inlet temperatures (TIT), necessitating advanced cooling technologies to maintain material integrity. Preventing the ingestion of hot gases into components not suited for high temperatures, like stator/rotor cavity disks, is crucial. Current gas turbine performance strategies focus on minimizing leakage and optimizing sealing systems. Notably, losses from main flow and cavity interactions are prominent in stator/rotor systems. Using Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, this study explores the unsteady interaction in a low-pressure turbine’s stator/rotor cavity. Numerical simulations of the University of Genova’s cavity rig are validated against experimental results. The investigation examines stator/rotor interaction effects, including wake ingestion from upstream rotor bars and the blocking impact of downstream rotor bars on cavity sealing. Varied cooling air injection rates in multiple calculations reveal insights into stage efficiency and cavity leakage. Emphasis is on unsteady loss mechanisms downstream of the vane row and in the region where the cavity flow is reintroduced in the main channel, providing a better understanding of losses influenced by cooling flow rates. The analysis of the loss amount along the axial direction demonstrates that losses generated in the vane row are increased prior to entering into the downstream rotor bars, due to cavity main flow interaction. This provide useful information about the production of losses due to sealing flow rate
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
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