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Corral R.,ITP Group | Corral R.,University Politecnicade Madrid | Vega A.,Technical University of Madrid
Journal of Propulsion and Power

The unsteady aerodynamics of low-pressure turbine vibrating airfoils in flap mode is studied in detail using a frequency-domain linearized Navier-Stokes solver. Both the traveling-wave and influence coefficient formulations of the problem are used to highlight key aspects of the physics and understand the trends of the modulus and phase of unsteady pressure with the reduced frequency and Mach number. The study is focused in the low reduced-frequency regime, which is of paramount relevance for the design of aeronautical low-pressure turbines and compressors. It is concluded that the variation of the influence coefficient phase with the reduced frequency is linear, whereas the effect of the Mach number can be neglected in the first order approximation; moreover, the unsteadiness of the vibrating and adjacent airfoils is driven by vortex shedding mechanisms. Finally, a simple model to estimate the work per cycle as a function of the reduced frequency and Mach number is provided for bending modes. The edgewise and torsion modes are presented in less detail, but it is shown that acoustic waves are essential to explain its behavior. The nondimensional work per cycleofthe edgewisemode showsaweak dependence with the Mach number, whereasinthe torsion mode, a large number of airfoils is needed to reconstruct the work per cycle departing from the influence coefficients, and the mean value is Mach independent. © Copyright 2015 by Industria de Turbopropulsores S.A. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Source

Gomez-Vilda P.,University Politecnicade Madrid | Rodellar-Biarge V.,University Politecnicade Madrid | Nieto-Lluis V.,University Politecnicade Madrid | De Ipina K.L.,University of the Basque Country | And 4 more authors.

Speech production in patients suffering of dementias of Alzheimer's type is known to experience noticeable changes with respect to normative speakers. Classically this kind of speech has been described as presenting altered prosody, rhythmic pace, anomy, or impaired semantics. Phonation, conceived as the production of voice in voiced speech fragments remains as an unexplored field. The aim of the present paper is to open a preliminary study presenting biomechanical estimates from phonation produced by two patients (male and female) suffering Alzheimer's Disease (AD), contrasted on two controls of both genders (CS: control speakers). A vocal fold biomechanical model is inverted to facilitate estimates of the vocal fold stiffness to analyze significant segments of phonated speech as long vowels and fillers. The estimates of both the AD patients and CS subjects are contrasted on a database of phonation features from a normative speaker population of both genders, as well as in paired tests contrasting AD and CS subjects. Results show the possibility of establishing significant discrimination between AD and CS when using f0, as well as vocal fold body stiffness, although this last feature seems to be more relevant and shows larger statistical significance. © 2015 Elsevier B.V. Source

Totry E.,University Politecnicade Madrid | Molina-Aldareguia J.M.,IMDEA Madrid Institute for Advanced Studies | Gonzalez C.,University Politecnicade Madrid | Gonzalez C.,IMDEA Madrid Institute for Advanced Studies | And 2 more authors.
Composites Science and Technology

The effect of fiber, matrix and interface properties on the in-plane shear response of carbon-fiber reinforced epoxy laminates was studied by means of a combination of experiments and numerical simulations. Two cross-ply laminates with the same epoxy matrix and different carbon fibers (high-strength and high-modulus) were tested in shear until failure according to ASTM standard D7078, and the progressive development of damage was assessed by optical microscopy in samples tested up to different strains. The composite behavior was also simulated through computational micromechanics, which was able to account for the effect of the constituent properties (fiber, matrix and interface) on the macroscopic shear response. The influence of matrix, fiber and interface properties on each region and on the overall composite behavior was assessed from the experimental results and the numerical simulations. After the initial elastic region, the shear behavior presented two different regions, the first one controlled by matrix yielding and the second one by the elastic deformation of the fibers. It was found that in-plane shear behavior of cross-ply laminates was controlled by the matrix yield strength and the interface strength and was independent of the fiber properties. © 2010 Elsevier Ltd. Source

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