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Home>Products>Journal and Reviews>I.RE.AS.E.>Latest issue International Review of Aerospace Engineering - April 2009 - Papers
International Review of Aerospace Engineering - Papers
Vol. 2. n. 2, pp. 72-76
Abstract - The present article presents the Explicit Force Method (EFM). In the context of this method the Forces and Moments are computed first, and in a second step the displacements and rotations. The method is introduced for a Truss element. Its force matrix is based on interpolations and force equilibrium is stated. Following computation of forces, a stiffness matrix is derived, also based on interpolations, for the computation of the displacements. In a third step, it is also possible to derive new member forces based on the computed displacements. The Force Method can provide information on how applied loads etc., are distributed and sustained by a structure and supports. A truss structure is studied for which there exists an analytic solution. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Explicit Force Method EFM, Truss element, Interpolations, Computation.
Vol. 2. n. 2, pp. 77-83
Abstract - A design optimization of a supersonic converging-diverging nozzle for use in an open-loop wind tunnel was completed. The method developed uses the commercial CFD solver Fluent and the SQP optimization routine fmincon within Matlab. Grid adjustment was implemented within Fluent using user defined functions. It was shown that a cost function based on the normalized Mach number defect from the design value was the most successful at producing a nozzle profile with a uniform exit Mach profile. Averaging the Mach defect cost over the straightening section rather than just the exit plane produced an exit Mach profile smoother than that produced by the method of characteristics alone. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Supersonic nozzle, Shape optimization.
Vol. 2. n. 2, pp. 84-90
Abstract - Existence of cracks in industrial structures is one of the important causes of their failure. Therefore, it must be considered in stress analysis, designing and loading of such structures. In this paper, the buckling phenomenon in cracked plates is investigated. The effects of geometrical and mechanical parameters on deformation of plates and determination of buckling load are studied. The main purpose of this research is to investigate the buckling and post-buckling of cracked plates under axial compression loading in elastic-plastic materials, by consideration some parameters, such as crack length, crack angle, boundary conditions, imperfection and different material of plates (i. e. steel and aluminum).The numerical solution is carried out by the ABAQUS finite element software. The results show considerable effects of the above mentioned parameters on the buckling loads and post-buckling behavior of plates. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Cracked Plate, Buckling, Post-buckling, Finite Element Method.
Vol. 2. n. 2, pp. 91-97
Abstract - Multi-rotor airship have the potential to lift and transport very heavy payloads directly. For the quad rotor hybrid airship, the rotors are not only used for low speed control but also to provide overall lift to compensate for the payload. The objective of this paper is to present a model of such an airship, taking into account wind effect as well as the varying mass effects. Euler angles are used for kinematics. For dynamics, a mathematical description of a dirigible flight must contain the necessary information about aerodynamic, structural and other internal dynamic effects (engine, actuation) that influence the response of the airship to the controls and external atmospheric disturbances. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Lighter Than Air, Wind Effect, Payload.
Vol. 2. n. 2, pp. 98-103
Abstract - This paper examines the way to formulate and design the orbital analytical software and also designing the satellite subsystems; which are using the propulsions with low thrust. In recent years; remarkable advantages of electrical propulsions; which have low propulsive scale, attract attention of spatial engineers and designers in west countries and also in Iran. Hence, it is crucial to formulate the software with the orbital transfer capability and to conceptually design the satellite subsystems with low propulsive. Formulated software by using the parameters such as initial orbit, find orbit, transition time, initial mass and satellite systematic parameters, designs the subsystems. This software has the capability to examine the three groups of electrical propulsion: pulse-plasma, Xenon-ion and Xenon-hull. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Satellite, Software, Low Thrust.
Vol. 2. n. 2, pp. 104-111
Abstract - Flapping wing aerodynamics is a recent topic of interest for the design of micro aero vehicles (MAVs), particularly in the case of hovering. Inspiration for flapping motion has come from the study of birds and insects. For example, a dragonfly’s wing is known to produce lift through an unsteady aerodynamic mechanism based on the generation of leading edge vortices. Various researchers have considered motions that mimic birds and insects, though little work has been done to generate optimal flapping motions that are not rooted in observations of nature. This paper describes the optimization of the flapping airfoil motion for hovering using computational fluid dynamics (CFD) and numerical optimization. The objective of the optimization was to find the flapping motion that generates the highest time-averaged lift subject to various constraints. The optimization problem was solved using a parallel evolutionary algorithm. As an example, the method was used to determine the optimal flapping motion for an symmetric airfoil in order to maintain hover. The example demonstrates the utility of unsteady CFD analysis combined with numerical optimization for determining optimal flapping motion. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Flapping flight, Design optimization, Parallel computing, Optimal control
Vol. 2. n. 2, pp. 112-122
Abstract - Characteristics of “skip” atmospheric entry for a crewed lunar return mission are analyzed. A simplified skip reentry analysis is presented to support the assertion that skip reentry with precision landing is infeasible when the vehicle lift-to-drag ratio drops below 0.3. Especially for extended range missions, there exists a “cliff” where lateral control is no longer available. The use of flaps to modify the trim angle-of-attack examined. The effectiveness of the flap system was evaluated using first order “engineering” design tools that are based on traditional closed-form incidence angle methods. Engineering tools were used to size the flap system and subsequently CFD methods were used to verify and refine the engineering estimates. Comparisons between the two methods showed excellent agreement. A flap with surface area as small as 1 square-meter increases the trim Lift-to-Drag ratio from approximately 0.26 to greater than 0.32. This aerodynamic enhancement increases available cross range from essentially zero to greater than 1000 km. These enhancements significantly increase the flexibility of landing site operations, and offer a larger matrix of available landing sites for any time lunar return. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Skip-reentry, Lunar Return, CFD, Lift-to-Drag Ratio, Hypersonic Flow
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