7,301 research outputs found
Fan Noise Boundary Layer Ingestion Installation Effects for NOVA Aircraft Configuration
No full textAim of this paper is to investigate the effects of the turbulent flow developing over a fuselage on fan noise for Boundary Layer Ingestion (BLI) embedded propulsion systems. Such engine configurations can suffer from inlet flow distortions and ingestion of turbulence at the fan plane with consequent impact on both broadband and tonal fan noise. The analysis is performed by considering a modified version of the Low-Noise configuration of the NASA Source Diagnostic Test (SDT) integrated into the Nextgen ONERA Versatile Aircraft (NOVA) fuselage in order to reproduce the NOVA BLI configuration. The numerical flow solution is obtained by solving the explicit, transient and compressible lattice-Boltzmann equation implemented in the high-fidelity CFD/CAA solver Simulia PowerFLOW R®. The acoustic far-field is computed by using the Ffwocs-Williams & Hawkings integral solution applied to a permeable surface encompassing the fan-stage. Simulations are performed for an operating condition representative of a take-off with power cutback. Installation effects due to the BLI configuration are quantified by comparison with an isolated configuration of the modified Low-Noise SDT fan-stage geometry at same operating conditions. Comparisons are carried out in terms of fan-stage intake/interstage velocity fields, fan blades section air-loads and far-field noise; correlations between the fan-stage velocity field and noise emission for the BLI configuration are outlined. It is found that the BLI fan-stage is characterized by strong azimuthal fan blade loading unsteadiness, less periodic and coherent rotor wake tangential velocity variations and higher levels of in-plane velocity fluctuations compared to the isolated engine, resulting in far-field noise spectra with no distinct tonal components and higher broadband levels. This study represents the first high-fidelity CFD/CAA simulation of a full-scale aircraft geometry comprehensive of a BLI fan/Outlet Guide Vane (OGV) stage. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Wind Energ
Numerical analysis of fan noise for the NOVA boundary-layer ingestion configuration
No full textAim of this paper is to investigate the effects of the turbulent flow developing over a fuselage on fan noise for BLI embedded propulsion systems. Such configurations can suffer from inlet flow distortions and ingestion of turbulence at the fan plane with consequent impact on both broadband and tonal fan noise. The analysis is performed on a modified version of the Low-Noise NASA SDT fan-stage integrated into the ONERA NOVA fuselage in order to reproduce the NOVA BLI configuration. The numerical flow solution is obtained by solving the explicit, transient and compressible lattice-Boltzmann equation implemented in the high-fidelity CFD/CAA solver Simulia PowerFLOW®. The acoustic far-field is computed by using the Ffowcs-Williams & Hawkings integral solution applied to a permeable surface. All simulations are performed for an operating condition representative of a take-off with power cut-back. Installation effects due to the BLI configuration are quantified by comparison with an isolated configuration of the modified Low-Noise SDT fan-stage at the same operating condition. It is found that the BLI fan-stage, which is not optimal, is characterized by strong azimuthal fan blade loading unsteadiness, less axisymmetric and coherent rotor wake tangential velocity variations and higher levels of in-plane velocity fluctuations compared to the isolated engine. This resulted in no distinct tonal components and higher broadband levels in the far-field noise spectra, as well as in an increment of cumulative noise levels up to 18 EPNdB. This study, which represents the first high-fidelity CFD/CAA simulation of a full-scale aircraft geometry comprehensive of a BLI fan/OGV, provides with a clear understanding of the change of the noise sources in BLI integrated configurations.Wind Energ
Using performance assessment in secondary school mathematics: an empirical study in a Singapore classroom
No full textThis article reports an exploratory study on using performance assessment in mathematics instruction in a high-performing secondary school in Singapore. An intact mathematics class participated in the study, and received chapter-based performance tasks as intervention during regular mathematics lessons for about one and a half school years. The performance tasks used included authentic and/or open-ended tasks. The students’ academic achievements and attitudes in mathematics were compared with a comparison class that did not receive the intervention. Both quantitative and qualitative data were collected, mainly through questionnaire surveys, performance task tests, conventional school exams, and interviews with students and teachers. The results suggest that the students receiving the intervention performed significantly better than their counterparts in solving conventional exam problems, and in general they also showed more positive changes in attitudes towards mathematics and mathematics learning. The students from the experimental class also expressed positive views about the benefits of using performance tasks in promoting their ability in higher order thinking, though no statistically significant difference was detected between the two classes of students in solving unconventional tasks before and after intervention. Overall, the results appear to support teachers’ using contextualised problems in real life situations and open-ended investigations in students’ learning of mathematic
Richardson, Barbauld, and the construction of an early modern fan club
No full textMPhilMuch has been written about the life and long works of the eighteenth century epistolary novelist, Samuel Richardson, but the prospect of his position as the first celebrity novelist – responsible for courting his own fame as well as initiating his own fan club – has largely been ignored. The body of manuscripts housed at the National Art Library in the Victoria and Albert Museum in London provides the modern scholar with evidence of the skeletal beginnings of an early fan club. This thesis aims to show how these manuscripts were turned into a saleable commodity by the publisher and entrepreneur Richard Phillips, while under the guiding hand of another, slightly later, literary celebrity, Anna Laetitia Barbauld. In order to restore Richardson’s reputation amongst a new nineteenth century audience, Barbauld was required to construct her own idea of him as an eighteenth century celebrity author, and in doing so the insecurities of a self-professed, apparently diffident man, are revealed. Barbauld’s capacious, but heavily edited selection of letters is analyzed in this thesis, providing ample evidence that Richardson’s correspondents were more than just eager letter writers. By using Barbauld’s biography of Richardson this thesis aims to show how she manipulates the genre of life writing in her construction of him.
This thesis offers an alternative reading of how the Richardson manuscripts are viewed, redefining them as not simply a collection of letters, but as a collective entity, deliberately selected and archived as evidence of an early modern fan club, and its celebrity managing director
Development of a rotor model for the numerical simulation of helicopter exterior flow-fields
No full textIncludes bibliographical references (leaves 84-85).A numerical methodology is developed to model the effect of a rotor on the surrounding flow-field. The model calculates the time-averaged aerodynamic forces exerted on the air by the fan blades within the blade-swept region, and permits the user to specify blade properties such as cross-sectional profile and orientation at a particular radial and azimuthal location. The calculated forces are included as source terms within the Reynolds-averaged Navier-Stokes equations for an incompressible fluid, which are solved by the commercial CFD solver, FLUENT. The effects of turbulence are incorporated through the use of Launder and Spalding's k-g turbulence model. This method is selected as being the most efficient use of the resources available, giving the economic advantages of a steady simulation, while allowing radial and azimuthal variations of rotor characteristics. In order to validate the accuracy of the numerical model for both aligned and non-aligned inflow conditions, results are compared with experimental data reported for an axial flow fan. Agreement between experimental and numerical results is excellent to good. Fan static pressure rise is closely predicted by the numerical solution, while fan power consumption and fan static efficiency are under and over-predicted respectively. This error may be attributed to frictional losses not accounted for in the numerical model. These include physical rotational instabilities, leading to increased mechanical losses, and tip effects due to the clearance between the fan blade tips and the fan casing. Trends are nevertheless consistently predicted by the numerical model for inflow angles up to 45°, and for the range of blade pitch settings used. The adverse effect of off-axis inflow on the fan static pressure rise is numerically predicted, while fan power consumption is found to remain independent of inflow angle, as had been experimentally observed. The rotor model is finally integrated with the fuselage of the CIRSTEL (Combined Infra-Red Suppression and Tail rotor Elimination) prototype in an analysis of the helicopter exterior flow-field. No experimental data for this configuration was available for validation purposes. However, the model is used in the simulation of several common helicopter flight conditions. Results are presented graphically, and generally indicate good agreement with physically observed phenomena
sj-docx-1-son-10.1177_23779608231215580 - Supplemental material for A Multisample Path Analysis Including a Novel Psychological Indicator, Attitude Toward Life, After the First Wave of COVID-19
No full textSupplemental material, sj-docx-1-son-10.1177_23779608231215580 for A Multisample Path Analysis Including a Novel Psychological Indicator, Attitude Toward Life, After the First Wave
of COVID-19 by Fan Li, Haiping Gu, Umit Tokac, Kimberly Werner, Anne F. Fish and Qingqing Lou in SAGE Open Nursing</p
Fan Fiction and Copyright: Outsider Works and Intellectual Property Protection
No full textAs long as there have been fans, there has been fan fiction. There seems to be a fundamental human need to tell additional stories about the characters after the book, series, play or movie is over. But developments in information technology and copyright law have put these fan stories at risk of collision with the content owners’ intellectual property rights. Fan fiction has long been a nearly invisible form of outsider art, but over the past decade it has grown exponentially in volume and in legal importance. Because of its nature, authorship, and underground status, fan fiction stands at an intersection of key issues regarding property, sexuality, and gender. In Fan Fiction and Copyright, author Aaron Schwabach examines various types of fan-created content and asks whether and to what extent they are protected from liability for copyright infringement. Professor Schwabach discusses examples of original and fan works from a wide range of media, genres, and cultures. From Sherlock Holmes to Harry Potter, fictional characters, their authors, and their fans are sympathetically yet realistically assessed. Fan Fiction and Copyright looks closely at examples of three categories of disputes between authors and their fans: Disputes over the fans’ use of copyrighted characters, disputes over online publication of fiction resembling copyright work, and in the case of J.K. Rowling and a fansite webmaster, a dispute over the compiling of a reference work detailing an author's fictional universe. Offering more thorough coverage of many such controversies than has ever been available elsewhere, and discussing fan works from the United States, Brazil, China, India, Russia, and elsewhere, Fan Fiction and Copyright advances the understanding of fan fiction as transformative use and points the way toward a safe harbor\u9d for fan fiction
Learning of algorithms: a theoretical model with focus on cognitive development
No full textTaking a broad perspective on algorithm in mathematics, the author presents a theoretical model about the learning and teaching of algorithm with focus on students’ cognitive development. The model consists of three cognitive levels: 1. Knowledge and Skills, 2. Understanding and Comprehension, and 3. Evaluation and Construction. The model suggests that teaching and learning of algorithm does not simply mean routine learning, memorization, or lead to a low level of cognition. The paper also discusses different teaching strategies and activities that can be used to support students’ cognitive development at different cognitive levels
The author in the postinternet age: Fan works, authorial function, and the archive
No full textFifty years since Roland Barthes proclaimed the death of the author, there still exists difficulty in framing the nature of interaction between commercial (professional) creators and fan (transformative) authors. In the postinternet age, the visibility of unsanctioned (or tacitly sanctioned) derivative fictional works has only increased, as have the number of commercial creators with experience in creating derivative works for a fan audience. It has therefore become necessary to interrogate whether the author has truly died in the Barthian sense, and if not, what role the construct of the author plays in today's popular mediascape. In an analysis of the Foucauldian author function (that is, the role discursively constructed authors play relative to their work) assessing both Euro-American and Japanese histories of fan practice, a move to a more open-source style of fan practice is evident. The author in an open-source fandom functions as a heuristic device through which fans may access and search the database, as well as a means of decentralizing commercial authority over media content
Computational aerodynamic study of automotive cooling fan in blocked conditions
No full textIn this paper, a CFD study of two types of axial-flow automotive cooling fans was conducted to investigate the effects of upstream and downstream blockage on aerodynamic performance of each fan. The realizable k-ε turbulence model was applied and simulations were performed to represent an automotive engine bay and quantify performance changes as a function of blockage distance. Modeling was performed for two fan designs: one optimized for a low flow rate, high-pressure operation; and a second optimized for high flow rate, low-pressure operation. The results show that the pressure loss caused by engine blockage increases at higher vehicle speed, and decreasing blockage distance. A new relation between blockage to fan proximity and fan performance was established. It is determined that the pressure change follows a quadratic type dependence, but the coefficients may vary, depending on fan type. The fan efficiency can be improved by taking advantage of larger blockage distances at higher speeds of the vehicle. The blockage condition causes an increase in the reverse flow near the fan interface, and a dramatic increase in radial flow
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