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Data supporting the article, "Transonic buffet characteristics under conditions of free and forced transition" published in the AIAA Journal, 2022
No full textThis dataset supports the publication by Moise, P., Zauner, M., Sandham, N. D., Timme, S. & Wei, H "Transonic Buffet Characteristics Under Conditions of Free and Forced Transition", AIAA Journal, https://doi.org/10.2514/1.J062362.
The data contains
DataSets.zip, containing ".csv" (comma separated values, CSV) files in ASCII format. These CSV files correspond to several plots presented in the article, "Transonic Buffet Characteristics Under Conditions of Free and Forced Transition" published in the AIAA Journal, 2022. Plots with aerofoil geometry are not provided due to copyright reasons. All CSV files are named in a "fig[No][subfigure][description].csv" format (e.g. fig30d_X.csv refers to figure 30d in the article with X being the variable stored). The figures for which data is provided are:
3,6,7,8,11,12,13,18,A1,B1.
A sample MATLAB script, sample Code.m is provided for plotting the data in the .csv files.
Padeep Moise is an Assistant Professor, Department of Aerospace Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India (email [email protected])
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Transonic buffet characteristics under conditions of free and forced transition
No full textTransonic buffet is commonly associated with self-sustained flow unsteadiness involving shockwave/boundary-layer interaction over aerofoils and wings. The phenomenon has been classified as either laminar or turbulent based on the state of the boundary layer immediately upstream of the shock foot and distinct mechanisms for the two types have been suggested. The turbulent case is known to be associated with a global linear instability. Herein, large-eddy simulations are used for the first time to make direct comparisons of the two types by examining free and forced-transition conditions. Corresponding simulations based on the Reynolds-averaged Navier–Stokes equations for the forced-transition case are also performed for comparison with the scale-resolving approach and for linking the findings with existing literature. Coherent flow features are scrutinised using both data-based spectral proper orthogonal decomposition of the time-marched results and operator-based global linear stability and resolvent analyses within the Reynolds-averaged Navier–Stokes framework. It is demonstrated that the essential dynamic features remain the same for the two buffet types (and for the two levels of the aerodynamic modelling hierarchy), suggesting that both types arise due to the same fundamental mechanism
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
On Transonic Wing Shock Unsteadiness
Full text linkAircraft wings in high-speed flight experience detrimental flow unsteadiness. Its interaction with the flexible wing structure and resulting dynamic loads are addressed in the certification specifications which stipulate a cruise design point free from any structural vibration and buffeting. One such flow unsteadiness is shock buffet and its inherent dynamics near the onset of unsteadiness are addressed herein. Specifically, an extensive experimental dataset of a large aircraft wing geometry and complementary scale-resolving simulations are scrutinised. Whilst the experimental dataset comprises a wide range of flow conditions from pre-onset to established buffet for Mach numbers between 0.70 and 0.84 and four configurations, the primary focus is on the clean wing at the design Mach number of 0.80 and Reynolds number of approximately 3.6 million (based on mean aerodynamic chord). Key to this study are highly-resolved unsteady surface pressure data acquired by dynamic pressure-sensitive paint, in addition to conventional data from pressure transducers and a wing-root strain gauge. To match the experiment and thereby aiding a richer elucidation of the flow physics, detached-eddy simulations are performed using two subgrid length-scale definitions, motivated by the challenge of simulating separating and reattaching shallow shear layers. Modal decomposition techniques are instrumental in pursuing a thorough data analysis. Experimentally, two distinct phenomena in shock-buffet conditions are identified. First, low-frequency shock unsteadiness with characteristic Strouhal numbers between 0.05 and 0.15 (where Strouhal number is based on mean aerodynamic chord and reference freestream velocity) propagates pressure disturbances predominantly inboard. Importantly, this coherent unsteadiness is exclusive to the experiment and even occurs before the strain gauge detects structural buffeting. Second, a broadband higher-frequency behaviour for Strouhal numbers between 0.2 and 0.5 is characterised by three-dimensional cellular patterns describing localised pockets of shear-layer pulsation synchronised with an outboard-propagating shock oscillation. Dominant modal features capturing this characteristic signature show striking similarity between experiment and simulation, detailing the pertinent attributes of shock-buffet unsteadiness whilst contrasting it with the first phenomenon. These findings will help clarify these edge-of-the-envelope flow phenomena and ultimately inform future wing design
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
On Modal Identification of Transonic Buffet on Elastic Wings
Full text linkShock buffet on wings is a phenomenon caused by strong shock-wave/boundary-layer interaction resulting first in self-sustained flow unsteadiness and eventually in a detrimental structural response called buffeting. While it is an important aspect of wing design and aircraft certification, particularly for modern transonic air transport, not all the underlying multidisciplinary physics are thoroughly understood. This work details such a multidisciplinary study. First, a triglobal stability analysis of a fluid-structure coupled system is presented, utilising the implicitly restarted Arnoldi method with a sparse iterative Krylov solver and novel preconditioner. An asymmetry resulting from a static aeroelastic simulation based on a finite-element model of the underlying geometry in a wind-tunnel modifies the global modes of a symmetric full-span analysis. A flutter stability analysis at wind-tunnel flow conditions below shock-buffet onset finds no instability in the structural degrees-of-freedom, whereas in shock-buffet flow with globally unstable fluid modes additional marginally unstable structural (and fluid) modes emerge. The developed stability tool for coupled analysis is instrumental in identifying those physically relevant and strongly coupled modes where a standard pk-type flutter analysis fails. Incorporating the computation of adjoint eigenmodes, the core of the instability is pinpointed to a relatively small wing area, which is insightful to effect the control and delay of this detrimental transonic unsteadiness. Second, iterative resolvent methods are used to compute the dominant singular triplets (of gain, forcing and response). The application of the resolvent method as a predictive tool to detect transonic buffet flow unsteadiness, well before global stability analysis can first identify its dynamics through weakly damped eigenmodes, is demonstrated. Its ability to uncover modal physics, not identifiable through global stability analysis, is discussed. It is also shown that even non-dominant modal features can be found using a windowed formulation. Lastly, the impact of a flexible structure on the (pseudo-) resonant properties is also investigated. This study contributes to the further understanding of shock buffet on finite wings and details novel methods to investigate modal features in edge-of-the-envelope flight for use in industrial applications of future wing design
Kunststoff-Verbundmaterialien im Brandtest
No full textWesentlich für das Sicherheitsniveau und damit der nachhaltigen Wettbewerbsfähigkeit des Technologiestandortes Deutschland ist der Brandschutz in Industrieanlagen, in Gebäuden und im Transportwesen. Die Verwendung von neuen innovativen Materialien, im Leichtbau oder von neuen Brandschutzbeschichtung, resultiert in neuartigen Herausforderungen und sich verändernden Brandschutzvorschriften. Im Rahmen des Vortrages werden Brandversuche von neuen Materialien bis hin zu Raumbränden, neue und alte Brandprüfungen gezeigt und Rückschlüsse für den heutigen Brandschutz gezogen
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