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Home>Products>Journal and Reviews>I.RE.AS.E.>Latest issue International Review of Aerospace Engineering - February 2009 - Papers
International Review of Aerospace Engineering - Papers
Vol. 2. n. 1, pp. 1-12
Abstract - This paper describes a uniform mathematical formulation involving analytical dynamics, structural dynamics and aerodynamics of a flexible quadrirotor helicopter named XSF in quasi-stationary flight conditions. This micro-flying object or microdrone is made in the IBISC Laboratory at the University of Evry; it has a central body which is connected to flexible components (arms and blades). The strategy to elaborate the dynamic model is oriented to the optimization of the ratio precision/simplicity. The model proposed takes into account the structural flexibility of the components, the aerodynamic and the gyroscopic phenomena on one hand, and has a limited number of degrees of freedom on the other hand to be well adapted for the control and stability analysis. The relative coordinates method is used. Numerical examples are presented at the end to prove the efficiency of this model. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Micro UAV, Design, Flexible Multibody System, Modeling, Simulation, Stabilization.
Vol. 2. n. 1, pp. 13-23
Abstract - This paper presents a computational methodology for tracing the locations of Blade Vortex Interaction (BVI) phenomena on a helicopter rotor disk. This methodology utilizes Vortex Element Method for rotor free wake computations. Wake vortices are modeled by a series of discrete vortex elements and induced velocity on rotor disk is calculated for the distorted wake geometry, integrating Biot-Savart law in closed form over each one of them. Bound circulation variations and unsteady blade airloading as a result of the nonuniform induced downwash are computed by blade element method. Wake roll up process, vortex core modeling and elastic blade motion are some of the aerodynamic topics modeled with special care in the developed procedure. BVI locations are detected and the phenomena are categorized as parallel, perpendicular and oblique regarding their orientation relative to rotor blade. The corresponding intensity and locus for each category are calculated. By these means, specific BVI phenomena can be isolated and their influence on blade downwash and airloads distribution can be demonstrated. The computational results of BVIs effects on blade airloading are compared with experimental data. These data are derived from model-rotor wind tunnel tests, performed in the duration of joined European research programs. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Helicopters, Rotor Aerodynamics, Blade Vortex Interactions, Vortex Core.
Vol. 2. n. 1, pp. 24-28
Abstract - This paper describes the development of a Multi-Disciplinary Optimization (MDO) approach for aircraft conceptual design considering discrete variables. The optimization was driven by a Multi-Objective Genetic Algorithm (MOGA). The results include the conceptual design of two types of aircraft; a Very Light Jet (VLJ) and an Unmanned Aerial Vehicle (UAV) using a simplified approach. A third result shows the optimization of a regional commercial aircraft with a 4 discipline MDO approach. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: MDO, Aircraft Design, Genetic Algorithm.
Vol. 2. n. 1, pp. 29-38
Abstract - An experimental investigation has been carried out to study the mixing and noise characteristic of multijets. A Multijet configuration with inter-nozzle spacing of 1.27 times the centre nozzle diameter has been considered in the investigation. Circular jets of exit Mach numbers (Mj ) 1.82, 3.10 and 3.61 were studied. The multijet configurations of three jets in a row and a centre jet surrounded by four equally spaced jets were considered in the study. In addition to the multijets, the centre jet characteristics also have been investigated for comparison. It is found that the nozzle pressure ratio (NPR) has a dominant influence on both mixing and noise characteristics of multi as well as single jet. For Mj = 1.82 the three jet configuration seems to be superior from mixing point of view. However, at NPRs multijets of Mj = 3.1 show better mixing characteristics. At higher NPRs, the five jet configuration for Mj = 3.61 is found to have significant mixing advantage over the three jet configuration. Thus, the jet Mach number and NPR play an important role on both mixing and noise characteristics of multijets. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Multijets, Shock-cell, Jet mixing, Expansion level, Jet decay, Canting.
by J. Angulo Zevallos, G. Filippone Vol. 2. n. 1, pp. 39-43
Abstract -
The purpose of the current
research is to develop a method to estimate and value quality warranty
time period of any industrial product or machine. To obtain this one the
reliability function that describe the machine over time is require the
knowledge, also the product demand function will be very important. Also
the demand proposes a practical methodology to find the reliability of a
clutch, very useful for engineers of design, manufacturers and engineers
of after sale. The methodology is based on an experimental procedure
based on testing life.
Keywords: Warranty, Reliability, Demand, Elasticity.
Vol. 2. n. 1, pp. 44-51
Abstract - The flutter analysis of a laminated composite tapered NACA-0012-64 wing is conducted using enhanced dynamic finite elements. A thin-walled closed box section based on a Circumferentially Asymmtric Stiffness (CAS) configuration is used to represent the wing model. The wing structure follows Euler-Bernoulli bending and St. Venant torsion beam theories and is subjected to quasi-steady incompressible flow. The refined DFE is validated based on a comparision with other well established methodologies and has proven to converge on the exact natural freuquencies using a lower number of thin-wall beam elements. The wing normal modes are then used in a preliminary aeroelastic stability analysis to determine the flutter and divergence speeds. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Aeroelastic Instability, Bending-Torsion Couplings, Composite Wing-Box, Divergence, Doubly Coupled Vibrations, Dynamic Stiffness Matrix (DSM), Finite Elements Method (FEM), Flutter, Geometric Coupling, Material Coupling, Tapered Wing, Wing Vibrations.
Vol. 2. n. 1, pp. 52-61
Abstract - The slosh dynamics in cryogenic fuel tanks under microgravity is a problem that severely affects the reliability of launching spacecraft. To date, computational fluid dynamics (CFD) models which examine low-gravity slosh behavior, as well as the dynamic coupling between the sloshing liquid and the container’s motion have not been benchmarked against experimental data. This work details a novel framework designed to yield experimental data that can be used for CFD model validation. Experimental measurements of slosh are made using a variety of platforms, including ground-based testing and parabolic flights. It is proposed that the 3-D rigid body acceleration of a tank relative to an inertial frame, along with the initial liquid distribution and tank geometry, uniquely determines a slosh event. The slosh event is completely described by the 6-DOF rigid body acceleration of the tank, and a set of orthogonal images. To benchmark the proposed hypothesis, CFD models were developed using a dynamic mesh solver. Both the tank’s predicted acceleration and images of the liquid profile are used to assess the ability of the proposed approach to correctly predict a slosh event. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Slosh Dynamics, Microgravity, CFD, Dynamic Mesh Model.
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