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Home>Products>Journal and Reviews>I.RE.AS.E.>Latest issue
International Review of Aerospace Engineering - June 2008 - Papers
International Review of Aerospace Engineering - Papers
Abstract - The present paper deals with synthetic jet actuators. The synthetic jet actuator is a low power, highly compact fluidic system and efficient to control a boundary layer. In this study, the development of synthetic jet is first analysed and characterized then its interaction with boundary layer along a flat plate is studied. The designed actuator is used in a wind tunnel. Different inclinations of the jet are investigated for a fixed forcing frequency (60 Hz). Both hot wire anemometer and the Particle Image Velocimetry (PIV) are used. First, the synthetic jet normal to the wall without cross flow is characterised. The inclination effect is then examined. The same situations are studied in presence of cross flow. For the normal jet, the PIV results show a decrease of the mean wall velocity. The phase-averaged velocity profiles revealed that spanwise large-scale vortices are generated downstream of the slot and persist farther downstream. The inclination of the synthetic jet has an important effect on the expansion of the jet. It has been observed that the interaction with the wall modify strongly this expansion. The modification induced by the jet angle variation will be analysed in details in this paper. We will focus on the wall behaviour. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Synthetic jet, vortex, turbulence, control.
Abstract - This document presents the results of a coupled fluid-thermal simulation along the trajectory of a hypersonic vehicle for different surface coatings. This kind of simulations will become more and more important in a reliable design of the thicknesses of the Thermal Protection System (TPS) of hypersonic vehicles. The considered vehicle is a suborbital payload carrier launched by a Lorentz Rail Accelerator (LRA). It is non-propelled and reaches an altitude of 115 km, where it leaves its payload. To reach the desired altitude, the payload carrier has to be accelerated at the Rail reaching a Mach number of 6,2 at its outlet. To determine the temperature evolution of the vehicle, the accurate simulation of the first instants of the trajectory is of outmost importance. Therefore, a coupled simulation provides a better estimation of the maximal temperature, necessary to dimension the TPS. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Aerothermodynamics, Multidisciplinary simulation, Electromagnetic Launcher, Hypersonics.
Abstract - This paper presents the experimental results on the flow characteristics of a 15º slanted entry Convergent-Divergent (CD) nozzle with a design Mach number of 2.94 exposed to M = 1.6, 1.8 and 2.0 streams. The 15º slanted entry nozzle results are compared with the results of identical geometry straight entry nozzle. The objective is to check whether a slanted entry nozzle, kept in a supersonic flow, with a detached shock present at its mouth, can choke and deliver supersonic flow. The results show that the nozzle can choke and deliver supersonic flow. The present study also explores the flow separation inside a slanted entry supersonic nozzle when it is exposed to a supersonic stream. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Slanted entry nozzle, Flow separation, Schilling relation, Shock and flow deflection angle.
by M. Bidabadi, R. Khalilinezhad, N. Moallemi
Abstract -
At present article we work on
physics and dynamics of iron particles in combustion chamber crossing
the flame zones of (iron- air) suspension. In this article we focus on
an iron dust free body diagram and forces on it. Gravity forces, drag
force from gas and thermopherotic force are these forces on an iron
particle. By existing of these forces on a particle, acceleration will
be inducted to a particle in flame zones and by solving the differential
equation of dynamic equation for a particle with continues boundary
condition in velocity curve of dusts in dust- air suspension we can
estimate the velocity profile across the flame zones. Theoretical
estimation of velocity profile in this study has been compared to an
experimental study on velocity and concentration profile of iron
particles across the flame propagating through the particles cloud.
Keywords: Iron dust, velocity profile, gravity force, combustion.
Abstract - The starting of crack initiation from micro-heterogeneities of the structure is often causes degradation of element’s structure. The industrial metallic materials are generally alloys of complex composition with defects (work hardening, dislocation, segregation of addition elements, grain boundaries, and porosities) which locally create an incompatibility of deformation and/or a stress concentration. Microscopic cracks can then start by accumulation of dislocation on the defect, if local crystallography is favorable there. In fretting fatigue, the application of mechanical under pressure contact during the complex loading of fretting fatigue involves cracks born from crystallographic dislocations. In order to understand and to enrich knowledge of the fretting fatigue phenomenon, a complete study of the parameters of elliptical inclined cracks by three dimensional Finite Element Method under conditions of fretting fatigue with complete contact was carried out. An initial crack was supposed to be nucleate at the end of the complete contact zone between the two bodies (specimen and pads). The crack shape and its dimensions have been varied parametrically to model the structured mesh in order to calculate the Stress Intensity Factors in three modes (I, II, III) and the Integral J. The simulations were carried out under conditions of axial loading with variable amplitude and nonlinear contact. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: 3D Finite Element, Elliptical Inclined Crack, Fretting Fatigue, Complete Contac, SIF, Integral J.
Abstract - A Dynamic Stiffness Matrix (DSM) is developed to analyze the free vibration characteristics of doubly coupled, cracked, laminated, unidirectional, unbalanced composite beams. Based on the closed form solution of the governing differential equations, an ‘exact’ DSM formulation for bending-torsion vibration of an intact composite beam is first presented. Both material and geometric/structural couplings are taken into account. Stress intensity factors, corrected for geometry and material anisotropy, are used to develop the local flexibility of a through-thickness cracked uniform beam. The system is modeled using two interconnected intact beams and the crack is modeled by implementing its local flexibility. The intact elements’ DSMs exhibiting both mass and stiffness properties are then assembled and the boundary conditions are applied to form the nonlinear eigenproblem of the overall system. The natural frequencies and modes are extracted using the well-known Wittrick–William (W-W) root counting algorithm. Numerical tests are conducted for a long, slender, flat, uniform, cantilever, laminated composite beam of solid rectangular cross-section, exhibiting material couplings. Both intact and damaged scenarios for a ply angle, η=30°, the crack located at 30% of the span, and the crack ratio of α=0.3, are investigated. Numerical results on natural frequencies and modes are in excellent agreement with the literature. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Bending-Torsion Couplings, Cracked Composite Beam, Doubly Coupled Vibrations, Dynamic Stiffness Matrix (DSM), Exact Formulation, Local Flexibility Matrix, Material Coupling.
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