1,720,996 research outputs found
Performance calculation for hybrid-electric aircraft integrating aero-propulsive interactions
No full textThe potential benefits of hybrid-electric or full-electric propulsion have led to an increased interest in this topic over the past decade. Hence the need to develop modern and innovative methods to analyze the performance of aircraft with unconventional propulsion systems. The purpose of this paper is to describe and apply a simulation-based algorithm integrating aeropropulsive effects for the mission analysis of conventional, hybrid-electric, and full-electric aircraft. The method composes the analysis toolbox of the aforementioned software, HEAD (Hybrid-Electric Aircraft Designer), developed by the DAF Research Group. Analysis toolbox has to perform a detailed mission simulation of a generic airplane. The proposed application deals with the evaluation of the effects on performance that wingtip-mounted propellers and distributed electric propulsion on regional turboprop category. The reference aircraft is similar to an ATR-42
Experimental analysis of aircraft directional control effectiveness
No full textAircraft directional control effectiveness is analyzed through experiments in wind tunnel. Control surfaces on low aspect ratio lifting surfaces exhibit different lifting capabilities compared to those with high aspect ratio. Such behavior must be carefully considered in the preliminary design phase to avoid any overestimation in size, weight, costs and emissions. Traditional sizing methodologies are based on coupling the effects of the wing planform (e.g. aspect ratio) at low angles of control surface deflection with the effects of wing section (e.g. chord ratio) evaluated on section data in the full range of control surface deflection, so that the non-linear aerodynamics is inherited from 2D data, completely neglecting the different aerodynamic behavior of a low aspect ratio wing at high angles of deflection. To fill this gap, an experimental wind tunnel test campaign on a generic regional turboprop aircraft model with a modular vertical tail with rudder has been performed. Results indicate that the aircraft design methodologies present in public literature underestimate the control surface effectiveness at high angle of deflections by 15% to 25%, leading to an average overestimation of control surface size
Aerodynamics characteristics of an innovative large turboprop through wind tunnel tests including propulsive effects
No full textThis paper deals with the assessment of both longitudinal and directional aerodynamic characteristics of an innovative large capacity turboprop aircraft by means of a wind tunnel test campaign on a scaled model. The aircraft under investigation is an innovative turboprop platform providing for a three lifting surface layout and a rear engine installation. The scope of this research is to deeply investigate the aerodynamic behavior of such an innovative platform to assess the aerodynamic interferences among the aircraft components. In particular, the effects of the third lifting surface (the canard), installed in front of the main wing, must be carefully investigated to have a reliable estimate of the aircraft stability and controllability characteristics. This innovative platform provides for a rear engine installation at the tip of the horizontal tailplane. Thus, a specific experimental campaign has been dedicated to investigating the aircraft aerodynamic characteristics in power on conditions
Conceptual design of commuter aircraft including distributed electric propulsion
No full textA comprehensive developed conceptual design and analysis tool is here employed in the design of hybrid electric 19 passenger’s commuter aircraft. Particular attention is payed to the regulation under which aircraft must be certified. The sizing activity accounts for the aero-propulsive interactions when distributed electric propulsion is present. Output of this activity are the energetic requirements and the mass breakdown, by combining the free choice of the designer with aviation regulations and requirements. The application here presented provides parametric studies based on different operating combinations of distributed electric propulsion and e-storage. The aim of the present work is the identification of a design range which would make the choice of the new technologies profitable. The most promising result is a full-electric concept having 16 distributed propellers and designed for a flight mission of 200 nmi certifiable under FAR-23 (or CS-23) regulation
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
Development of new preliminary design methodologies for regional turboprop aircraft by CFD analyses
No full textSince 2011 the aerodynamic research group of the Dept. of Industrial Engineering of the University of Naples "Federico II" makes use of the University's computing grid infrastructure SCoPE to perform parallel computing simulations with the commercial CAE package Star-CCM+. This infrastructure allows Navier-Stokes calculations on complete aircraft configurations in a relative short amount of time. Therefore, the software and the above mentioned infrastructure allow the parametric analysis of several configurations that are extremely useful to the correct estimation of aerodynamic interference among aircraft components and to highlight some useful trends that could indicate how a specific aerodynamic characteristic (i.e. the drag of a component, the wing downwash or the directional stability contribution of the vertical tail) is linked to aircraft geometrical parameters. Thus, with the choice of a specific set of test-cases it is possible to make a deep investigation on some aerodynamic features and, from the analyses of results, it is possible to extract and develop ad-hoc semi-empirical methodologies that could be used in preliminary design activities.
In this paper, two investigations are presented: the aerodynamic interference among aircraft components in sideslip and the aerodynamic characteristics of a fuselage, focusing on typical large turbopropeller aircraft category
AIRCRAFT DIRECTIONAL STABILITY AND CONTROL: NEW IMPROVED APPROACH IN TAIL DESIGN
Full text linkThis work deals with a review and proposed improvements of vertical tail classical design methods dealing with aircraft directional stability and control.
The research presented is based on many numerical and experimental results obtained by the authors (DAF research group, www.daf.unina.it) through both CFD calculations and wind-tunnel tests carried out on an aircraft modular configuration. A new improved methodology to predict the directional stability and control characteristics of an aircraft and a reliable sizing procedure for the vertical tail is proposed. The methodology obtained and all results are particularly relevant for the regional turboprop category, but they can also be applied to other transport aircraft configurations. A wind tunnel investigation involving more than 150 configurations has also been involved in order to validate the numerical approach for which about 200 configurations were involved. The analyses covered both the linear and the non-linear range of the aerodynamic coefficients
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