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Experimental characterization of turbulence spots on a flat plate at Mach 6
No full textTransition modelling and prediction is a critical topic at hypersonic speeds because of the physically large extent of the transition region and the impact of large variations or uncertainties in heat transfer, skin friction and other flow properties. The experimental activity presented in this paper is concerned with the intermittent region of transition, which extends from the initial breakdown of the laminar layer into turbulent ‘spots’ up to the position where the boundary layer is fully turbulent. The turbulent spots and roughness induced transition are strongly affected by compressibility and wall temperature.To improve the quantitative understanding of these effects direct and large-eddy simulations can be performed for prescribed surface characteristics. The simulation output will provide details of boundary layer intermittency, heat transfer and skin friction for comparison with dedicated experiments conducted in an high-speed wind tunnel.The paper will presents the results of the simulations and the first set of experiment carried out in the framework of the ATLLAS project, for a flight configuration at Mach 6. A brief critical discussion of the results will also be presented
A Reduced Order Model for Preliminary Design and Performance Prediction of Tapered Inducers: Comparison with Numerical Simulations
Full text linkThe article recalls the recent development of a reduced order model for the preliminary design, geometric definition and noncavitating performance prediction of tapered-hub, variable-pitch, mixed-flow inducers, and illustrates its application to a typical three-bladed, high-head inducer for liquid propellant rocket engines. The mean axisymmetric flow field at the trailing edge of the inducer blades and the noncavitating head coefficient at both design and off-design conditions are then compared with those obtained from the numerical flow simulations generated by a commercial CFD code. Together with earlier experimental validations, the results dramatically confirm the capability of the proposed model to generate interpretative and useful engineering solutions of the inducer preliminary design problem at a negligible fraction of the computational cost required by 3D numerical simulations
Mhd flow control experiment in air: Test article design
No full textAn advanced flow control experiment, concerning magnetohydrodynamics (MHD) interaction over a blunt body, has been designed by Alta, CIRA and Department of Electrical Engineering (DIE) of University of Bologna and to be realized in CIRA's plasma wind tunnel "Scirocco" under a technology research program (TRP) funded by the European Space Agency (ESA). This work is a further step of the researches performed during the last decade by Alta and DIE in the field of MHD interaction. This experimental campaign foresees the employment of a 50 kW electromagnet, enclosed into an insulated blunt-shaped metallic TPS convectively cooled and electrically insulated by a ceramic coating. The test article has been designed for an air flow with nominal stagnation conditions of p0=2 bar and h0=22 MJ/kg, but several other conditions are planned to be investigated. The aim of the experimental campaign, along with a better understanding of the physical phenomena occurring within an highly ionized shock layer with an applied magnetic field, is the comparison of the collected data with the numerical predictions of CFD codes developed by CIRA. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved
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
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