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CONTENTS
Volume 3, Number 4, October 2016
 

Abstract
Thrust Vectoring is a dynamic feature that offers many benefits in terms of maneuverability and control effectiveness. Thrust vectoring capabilities make the satisfaction of take-off and landing requirements easier. Moreover, it can be a valuable control effector at low dynamic pressures, where traditional aerodynamic controls are less effective. A numerical investigation of Fluidic Thrust Vectoring (FTV) is completed to evaluate the use of fluidic injection to manipulate flow separation and cause thrust vectoring of the primary jet thrust. The methodology presented is general and can be used to study different techniques of fluidic thrust vectoring like shock-vector control, sonic-plane skewing and counterflow methods. For validation purposes the method will focus on the dual-throat nozzle concept. Internal nozzle performances and thrust vector angles were computed for several range of nozzle pressure ratios and fluidic injection flow rate. The numerical results obtained are compared with the analogues experimental data reported in the scientific literature. The model is integrated using a finite volume discretization of the compressible URANS equations coupled with a Spalart-Allmaras turbulence model. Second order accuracy in space and time is achieved using an ENO scheme.

Key Words
thrust vectoring; dual throat nozzles; computational fluid dynamics

Address
Michele Ferlauto and Roberto Marsilio: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129, Turin, Italy

Abstract
In this manuscript, free vibrations of a unidirectional composite orthotropic Timoshenko beam based on finite strain have been studied. Using Green-Lagrange strain tensor and comprising all of the nonlinear terms of the tensor and also applying Hamilton\'s principle, equations of motion and boundary conditions of the beam are obtained. Using separation method in single-harmonic state, time and locative variables are separated from each other and finally, the equations of motion and boundary conditions are gained according to locative variable. To solve the equations, generalized differential quadrature method (GDQM) is applied and then, deflection and cross-section rotation of the beam in linear and nonlinear states are drawn and compared with each other. Also, frequencies of carbon/epoxy and glass/epoxy composite beams for different boundary conditions on the basis of the finite strain are calculated. The calculated frequencies of the nonlinear free vibration of the beam utilizing finite strain assumption for various geometries have been compared to von Karman one.

Key Words
finite strain; composite beam; Timoshenko model; nonlinear free vibration; GDQM

Address
Ahmad Reza Ghasemi and Masood Mohandes: Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran

Abstract
The dynamical requirements are obtained for airplanes to travel on inclined circular trajectories. Formulas are provided for determining the load factor, the bank angle, the lift coefficient and the thrust or power required for the motion. The dynamical properties of the airplane are taken into account, for both, airplanes with internal combustion engines and propellers, and airplanes with jet engines. A procedure is presented for the construction of tables from which the flyability of trajectories at a given angle of inclination can be read, together with the corresponding minimum and maximum radii allowed. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and a F-16 jet airplane.

Key Words
airplane circular trajectory; inclined circular trajectories, airplane equation of motion; circular arc connection; automatic trajectory planning

Address
Gilles Labonte: Department of Mathematics and Computer Science and Department of Electrical Engineering and Computer Engineering, Royal Military College of Canada, Kingston, Ontario, Canada

Abstract
Star sensors are the attitude estimation sensors of the satellite orbiting in its path. It gives information to the control station on the earth about where the satellite is heading towards. It captures the images of a predetermined reference star. By comparing this image with that of the one captured from the earth, exact position of the satellite is determined. In the process of imaging, stray lights are eliminated from reaching the optic lens by the mechanical enclosures of the star sensors called Baffles. Research in space domain in the last few years is mainly focused on increased payload capacity and reduction in launch cost. In this paper, a star sensor baffle made of Aluminium is considered for the study. In order to minimize the component weight, material wastage and to improve the structural performance, an alternate material to Aluminium is investigated. Carbon Fiber Reinforced Polymer is found to be a better substitute in this regard. Design optimisation studies are carried out by adopting suitable design modifications like implementing an additional L-shaped flange, Upward flange projections, downward flange projections etc. A better configuration of the baffle, satisfying the design requirements and achieving manufacturing feasibility is attained. Geometrical modeling of the baffle is done by using UNIGRAPHICS-Nx7.5R. Structural behavior of the baffle is analysed by FE analysis such as normal mode analysis, linear static analysis, and linear buckling analysis using MSC/PATRANR, MSC-NASTRANR as the solver to validate the stiffness, strength and stability requirements respectively. Effect of the layup sequence and the fiber orientation angle of the composite layup on the stiffness are also studied.

Key Words
FE analysis; carbon fiber reinforced polymer; design optimisation

Address
M. Vinyas: UBDTCE, Davangere 577004, Karnataka, India
M. Vishwas: Siddaganga Institute of Technology, Tumkur, Karnataka, India
C.S. Venkatesha: UBDTCE, Davangere 577004, Karnataka, India
G. Srinivasa Rao: Scientist-Engineer, ISRO, Bangalore, Karnataka, India

Abstract
Limit cycle oscillations (LCO) as well as nonlinear aeroelastic analysis of a swept aircraft wing with cubic restoring moments in the pitch degree of freedom is investigated. The unsteady aerodynamic loading applied on the wing is modeled by using the strip theory. The harmonic balance method is used to calculate the LCO frequency and amplitude for the swept wing. Finally the super and subcritical Hopf bifurcation diagrams are plotted. It is concluded that the type of bifurcation and turning point location is sensitive to the system parameters such as wing geometry and sweep angle.

Key Words
cubic nonlinearity; bifurcation; limit cycle oscillations (LCO); harmonic balance method; sweep angle

Address
Saied Irani, Mohammadreza Amoozgar and Hamid Sarrafzadeh: Department of Aerospace Engineering, Khaje Nasir Toosi University of Technology, Tehran, Iran

Abstract
This paper presents the dynamic instability analysis of un-damped elastically supported piezoelectric functionally graded (FG) beams subjected to in-plane static and dynamic periodic thermomechanical loadings with uncertain system properties. The elastic foundation model is assumed as one parameter Pasternak foundation with Winkler cubic nonlinearity. The piezoelectric FG beam is subjected to non-uniform temperature distribution with temperature dependent material properties. The Young\'s modulus and Poison\'s ratio of ceramic, metal and piezoelectric, density of respective ceramic and metal, volume fraction exponent and foundation parameters are taken as uncertain system properties. The basic nonlinear formulation of the beam is based on higher order shear deformation theory (HSDT) with von-Karman strain kinematics. The governing deterministic static and dynamic random instability equation and regions is solved by Bolotin\'s approach with Newmark\'s time integration method combined with first order perturbation technique (FOPT). Typical numerical results in terms of the mean and standard deviation of dynamic instability analysis are presented to examine the effect of slenderness ratios, volume fraction exponents, foundation parameters, amplitude ratios, temperature increments and position of piezoelectric layers by changing the random system properties. The correctness of the present stochastic model is examined by comparing the results with direct Monte Caro simulation (MCS).

Key Words
dynamic instability; functionally graded beams; Bolotin

Address
Niranjan L. Shegokar and Achchhe Lal: Department of Mechanical Engineering, S.V.N.I.T. Surat-395007, India

Abstract
Variances in turbomachinery blades caused by manufacturing, operation or regeneration can result in modified structural behavior. In this work, the scatter of geometrical and material properties of a turbine blade and its influence on structure performance is discussed. In particular, the vibration characteristics and the lifetime of a turbine blade are evaluated. Geometrical variances of the surface of the blades are described using the principal component analysis. The scatter in material properties is considered by 16 varying material parameters. Maximum vibration amplitudes and the number of load cycles the turbine blade can withstand are analyzed by finite element simulations incorporating probabilistic principles. The probabilistic simulations demonstrate that both geometrical and material variances have a significant influence on the scatter of vibration amplitude and lifetime. Dependencies are quantified and correlations between varied input parameters and the structural performance of the blade are detected.

Key Words
aeroengine; probabilistic analysis; structural analysis; starting dynamics; lifetime

Address
Ricarda Berger, Timo Rogge, Eelco Jansen and Raimund Rolfes: Leibniz Universität Hannover, Institute of Structural Analysis, AppelstraBe 9A, 30167 Hanover, Germany


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