1,720,976 research outputs found
A time-explicit immersed boundary projection method for thin elastic surfaces and stationary bodies
Get PDFDSpace SAF Submission Ingestion Package generated from Vireo submission #16604 on 2021-09-16 at 17:06:38We present an immersed-boundary method for flows around either an arbitrary body undergoing prescribed kinematics, or a thin elastic body whose motion is fully coupled to the flow dynamics (i.e., involving fully coupled fluid-structure interaction, FSI). The key novelty here is that the proposed method uses an explicit time integration approach (via a Runge-Kutta-Chebyshev framework) for the stiff diffusive term while retaining a formal projection formulation to ensure that the no-slip boundary condition is exactly satisfied to within machine precision at each time instance. The explicit treatment of the diffusive term avoids the embedded large linear solves that plague the majority of fractional step formulations for incompressible flows, while the projection formulation avoids the use of heuristic parameters to satisfy the constraint at the immersed interface. Moreover, in the FSI setting the projection formulation results in a strongly coupled algorithm that can accurately simulate FSI dynamics involving arbitrarily large structural motions. The governing flow equations are spatially discretized using a nullspace approach that automatically enforces the incompressibility constraint, and when the immersed body is deformable the structural dynamics are spatially discretized using a finite element method. The structural model allows for geometric nonlinearity via a co-rotational formulation. We analytically demonstrate that the proposed time advancement scheme is temporally second order accurate for the primary state variables (e.g., vorticity) and first-order accurate for the surface stress. The method is verified using a suite of two-dimensional test problems: flow past both a rigid stationary cylinder at Re = 200 and past a deformable flag for various dimensionless parameters. In all cases the results are shown to be in good agreement with the literature.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-05-01The student, Noah Osman, accepted the attached license on 2021-04-28 at 12:30.The student, Noah Osman, submitted this Thesis for approval on 2021-04-28 at 13:37.This Thesis was approved for publication on 2021-04-30 at 08:47.Made available in DSpace on 2021-09-17T02:34:50Z (GMT). No. of bitstreams: 2
OSMAN-THESIS-2021.pdf: 2837528 bytes, checksum: 47975ea5b2cad224762c80b4edaf0fbc (MD5)
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Previous issue date: 2021-04-30Embargo set by: Seth Robbins for item 118596
Lift date: 2023-09-17T02:34:57Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Onl
Surface actuation based flow control for low Reynolds number flow past an airfoil
No full textSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-10-19 without embargo termsThe student, Ernold Thompson, accepted the attached license on 2025-04-30 at 20:53.The student, Ernold Thompson, submitted this Thesis for approval on 2025-04-30 at 20:58.This Thesis was approved for publication on 2025-05-05 at 13:26.DSpace SAF Submission Ingestion Package generated from Vireo submission #22136 on 2025-10-19 at 18:11:25In this thesis, surface actuation for the flow past an airfoil at a Reynolds number of 1000 has been studied numerically. First, prescribed normal actuation in the form of a backward traveling wave on the suction surface with sinusoidal spatial and temporal characteristics has been studied for the purpose of lift improvement. The kinematics of actuation are defined by wavenumber and wavespeed, both of which are varied over a wide range of values to include parameters that considerably change the lift dynamics as well as those that do not. First, the effect of actuation at an angle of attack of α = 5◦ where the unactuated flow is steady is considered. Lift benefits are found to be maximal when the morphing kinematics align with the intrinsic advection velocity of the flow. Then, the role of morphing in the presence of an unsteady, separated baseline flow (with intrinsic vortex-shedding processes) at α = 15◦ is investigated. At this higher angle of attack, three distinct behavioral regimes based on the relationship between morphing and the underlying shedding frequency are identified. Actuation is found to yield lift benefits when the actuation time scales are close to those of shedding with the highest increase in mean lift occurring when the actuation frequency is slightly smaller than the shedding frequency of the unactuated flow. The influence of the actuation on the flow field is discussed in terms of the variations in the pressure field resulting from the velocity boundary condition imposed by surface actuation. The velocity boundary condition imposed by actuation is also used to describe the variations in vortex shedding behavior at α = 15◦. Although backward traveling wave on the suction surface can lead to improvements in mean lift, a concurrent increase in drag occurs. To explore actuation for the separate purposes of lift improvement and drag mitigation, in the second part of this thesis numerical optimization is used to determine the actuation for the separate goals of lift improvement and drag mitigation at α = 15◦ with actuation permissible on the entire surface of the airfoil (including the pressure side). The gradient information required by the optimization algorithm is computed in a computationally efficient way using the adjoint of the governing equations. The optimal actuation profiles for the two performance aims are compared. Where possible, similarities with actuation in the form of backward traveling waves on the suction surface have been highlighted. The flow features emerging from the optimal actuation variations, and their consequent influence on the instantaneous aerodynamic coefficients, have been analyzed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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