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International Review of
Aerospace Engineering - Papers
Aerodynamic-Shape Optimization of Supersonic-Missiles Using Monte-Carlo
by A. Z. Al-Garni, A. H. Kassem, A. M. Abdallah
Abstract
- This paper presents a fast and reliable technique for aerodynamic shape
optimization of supersonic missiles using Monte Carlo optimization method. The
technique is based on two modules: Aerodynamics module and optimization module.
The aerodynamic module is based on components build-up method where analytical,
and semi-empirical of different missile components were added together, with
some interference factors, to calculate the overall aerodynamics of the missile.
The Aerodynamics module is validated against known wind tunnel data and showed
good agreement. The optimization module is aimed at finding Missile geometry
(such as length, fins dimensions and fins location, etc.) which maximize
lift-over-drag using Monte Carlo technique. Monte Carlo simulation Technique has
proved itself as a simple and easy to implement tool for aerospace vehicles
shape optimization.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Analytical aerodynamic model, component build-up method, Monte Carlo, missile
shape configuration optimization, supersonic.
Free
Flight Simulation Prediction for Fin-Stabilized Projectiles
by D. N. Gkritzapis, E. P. Panagiotopoulos, D. P. Margaris
Abstract
-
Any model predictive control
scheme is dependent upon the accuracy of the underlying dynamic flight
trajectory model. Under most flight conditions, the full equations of motion can
be adequately represented by a full six degrees of freedom (6-DOF) rigid body
model for fin-stabilized projectiles via atmospheric flight to final impact
point. The nonlinear applied mathematical model is based on no-roll body
reference frame and is integrated numerically from given initial conditions at
the firing site. In addition, a modified linear theory is used for comparison
with the full 6-DOF flight analysis based on a series of suitable manipulations
and simplifications under restricted flight conditions. The projectile
maneuvering motion depends on the most externally-applied significant
aerodynamic forces and moments variations. The computational trajectory analysis
takes into consideration the Mach number and total angle of attack effects by
means of variable and constant aerodynamic coefficients during the whole
atmospheric flight motion.. It can be further coupled to a suitable trajectory
tracking control system for current and future control actions applied to a
projectile for minimizing the estimated error to target impact area.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Fin-stabilized projectiles, Modified linear theory, Six degree of freedom.
Inverse Simulation Study of Aircraft in Prescribed Trajectory Flight
by W. Blajer, J. Graffstein, M. Krawczyk
Abstract
- A systematic approach to the modeling and simulation of aircraft in prescribed
trajectory flight is presented. The aircraft is subject to follow a prescribed
trajectory in space (two constraints on its mass centre position), and two other
demands are imposed on aircraft motion on the trajectory and the airframe
attitude with respect to the trajectory. The aircraft is controlled by aileron,
elevator and rudder deflections, and the thrust value. By combining the four
servo-constraint requirements with the aircraft dynamic equations and some
kinematical relationships, the governing equations of the prescribed motion are
developed in the form of index-three differential-algebraic equations. An
effective numerical code for solving the governing DAEs is described. The
solution consists of time variations of the state variables and the required
control that ensures realization of the prescribed motion. This gives a unique
opportunity to study the simulated control strategies and evaluate feasibility
of the modeled aircraft maneuvers. The inverse simulation of a landing maneuver
of a light training aircraft serves as illustration of the proposed technique.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Aircraft prescribed trajectory flight, Inverse simulation, Servo-constraints.
Design and Testing
of ISU-AABL Wind and Gust Tunnel
by P. P. Sarkar, F. L. Haan, Jr.
Abstract
- A wind tunnel with advanced capabilities will aid research efforts to
understand the complex fluid structure interaction problems encountered in
aerospace engineering, industrial aerodynamics and wind engineering applications
since wind tunnels remain an integral component of the design process for wind
sensitive structures. Whether dealing with the aerodynamics of aerospace,
mechanical or civil engineering structures many issues remain to be fully
resolved-including the role of non-stationary gust interactions, Reynolds number
effects, and the significance of small-scale turbulence. Building the next
generation of such wind tunnels will contribute to the understanding of these
issues. A combination Aerodynamic/Atmospheric Boundary Layer (AABL) Wind and
Gust Tunnel with a unique active gust generation capability has been developed
for various applications at Iowa State University (ISU). This wind tunnel is
primarily a closed-circuit tunnel that can be also operated in open-return mode.
It is designed to accommodate two test sections (2.44m x 1.83m and 2.44m x
2.21m) with a maximum wind speed capability of 53 m/s. This paper describes the
wind tunnel and its components and presents a comparison of the predicted and
measured design parameters. It shows that the wind tunnel is capable of
generating uniform flow with very low turbulence in the aerodynamic test section
and produces gust magnitudes around 27% of the mean flow speed.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Active Gust Generation, Industrial Aerodynamics, Unsteady Flow, Wind
Engineering, Wind Tunnel Design.
by P. P. Krimbalis, C. Poon, K. Behdinan, Z. Fawaz
Abstract
- A novel methodology for predicting the bearing strength of fibre metal
laminates (FMLs) was developed and implemented based on theoretical and
empirical results. Finite element (FE) analyses were carried out on layer by
layer models of several different variants of GLARE and lead to a redefinition
of the compressive characteristic dimension (CCD). The new definition is
governed by the yield strength of the aluminum layers and it was shown,
analytically, that the contribution of the glass layers to bearing strength, in
a bearing mode, is negligible. As a result, it was proposed that bearing
strength in FMLs is governed by delamination and yielding of the aluminum
layers. A novel experimental methodology was the designed using strain gages to
measure the local deformation of a pin bearing configuration based on the new
CCD definition. Novel bearing strength versus measured strain curves were
generated which lead to a redefinition of bearing yield and a complete
characterization of the material response. Yielding has in fact occurred within
the predicted CCD distance – according to the new definition(s) – and further
work is currently underway to support this notion further.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Fibre Metal Laminates, GLARE, Bearing Strength, Characteristic Length Method,
Delamination Buckling, Finite Element Method, Experimental Methodology.
Travelling Shock
Interaction with Rocket Nozzle
by H. S. Chopra, D. R. Greatrix, J. G. Kawall
Abstract
- An experimental and numerical study has been undertaken to examine various
aspects pertaining to the interaction of an incident travelling axial shock wave
with a choked exhaust nozzle for a rocket motor. A cold-flow experiment, based
on a shock tube scheme tailored to the present application, proved useful in
providing information surrounding the interaction process. Both experimental and
numerical results confirmed the existence of substantial transient radial wave
activity superimposed on the base reflected axial shock wave. By analogy to
actual propulsion system combustion chambers, the transverse wave activity
superimposed on the principal axial wave is potentially a factor in supporting
an augmentation of the local combustion rate in the aft region of a rocket motor
combustor. These results illustrate the potential weaknesses of one-dimensional
flow models for certain engineering applications, where important
multidimensional phenomena, such as those observed in this study, may not be
captured.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Axial combustion instability, travelling shock wave, rocket motor nozzle.
Visualization and Size Measurement of Vortex Shed by Flat and Arc Plates in an
Uniform Flow
by Y. Takama, K. Suzuki, E. Rathakrishnan
Abstract
- The vortices shed from the edges of flat and arc plates kept normal to an
uniform water flow has been investigated using a simple experimental facility.
The twin vortex behind the plate is formed at Reynolds numbers which are much
higher than that for a circular cylinder. This indicates the dominant role
played by the reverse flow on the vortex formation. Describing the vortex shape
as an ellipse, the semi-major axis has been measured by visualization. The
vortex size behind the arc plate is found to be smaller than that behind a
comparable flat plate at identical flow conditions. It implies that the base
smoothness reduces the strength of the reverse flow. Thus in general, it appears
that there is a limiting situation at which the twin vortex formation is
dominated by the reverse flow and not by the upstream flow rolling from the
plate edge towards the base. Furthermore, it is seen that the size of the vortex
can be controlled with plate geometry.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Vortex, Visualization, Flat plate, Low Reynolds number.
Shifted Cross-Wire for Jet
Flow Control
by P. Lovaraju, E. Rathakrishnan
Abstract
- The results of an experimental investigation conducted to assess the
effectiveness of a passive control in the form of a cross-wire (a thin wire
running normal to the jet axis) located downstream of the nozzle exit, for
altering the shock structure in the jet core and promoting jet mixing, has been
presented in this paper. The idea of keeping the control at a distance
downstream of the nozzle exit is to keep the nozzle exit area clean and the flow
exiting the nozzle undisturbed, as these are the most important parameters from
thrust loss point of view. Mach 0.6, 0.8 and 1.0 axi-symmetric jets from
convergent nozzle were studied by placing the cross-wire at X/De = 1.0. The
cross-wire was found to be effective in promoting the jet mixing. For the
underexpanded sonic jet studies NPR 3, 5 and 7 were chosen and it was found that
the cross-wire reduced the pitot pressure amplitudes, which is a direct measure
of shock strength reduction. The reduction in supersonic core region (defined as
the axial extent of the pitot pressure oscillations) for the controlled jets is
around 36% and 34%, for NPR 5 and 7, respectively.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
control, Supersonic core reduction, Jet mixing enhancement, Shifted cross-wire.
Effect of Arc-Tabs on the Mixing Charactrestics of Subsonic and Sonic Jets
by S. Thanigaiarasu, S. Elangovan, E. Rathakrishnan
Abstract
- The effect of tabs placed at the exit of a circular nozzle of 10 mm exit
diameter on the near flow field characteristics of the jet was investigated
experimentally for subsonic and sonic Mach numbers. The tab used was a sem-
circular arc of diameter 1.5 mm and length 2 mm. The near field characteristics
of the jet was studied for two configurations of the tab, namely, the concave
surface facing the flow exiting the nozzle (arc-tab facing-in), convex surface
facing the flow (arc-tab facing-out) and flat rectangular tab, for the blockage
ratio of 7.64%. The centerline Mach number decay shows that, for the jet with
arc-tab facing-in, a maximum reduction in core length of about 80% of the core
of the plain jet was achieved at all subsonic and correctly expanded sonic
conditions. Arc-tab facing-out and rectangular tab configurations reduce the
core length by about 50%. The decay of arc-tab controlled jet was compared with
that obtained for rectangular tab of same blockage and a plain circular nozzle.
The jet was found to decay at a faster rate in the case of arc-tab facing-in
configuration as compared to the facing-out and rectangular tab configurations.
Mach number profiles show that, the arc-tab facing-in distorts the jet
effectively by spreading the jet wider in the plane normal to the tab compared
to arc-tab facing-out. Iso-Mach contours show that, the jet spread is wider in
the plane normal to the tab and the effect of spread is more pronounced in the
jet with arc-tab facing-in as compared to arc-tab facing-out. The effect of the
tab orientation and its shape seem to have a profound influence on the evolution
of the jet.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Arc-tab facing-in, Arc-tab facing-out, Streamwise vortices, Mach number decay.
High Temperature and Real Gas Flow Phenomena of Hypersonic Earth Entry Flight
by E. E. Panagiotopoulos, D. P. Margaris
Abstract
- Real gas effects in high entry temperatures are taken into consideration
combining flight conditions during hypersonic flight into Earth’s atmosphere.
Convective stagnation heating loads are estimated from the original full
Fay-Riddell formula and compared with other engineering analytical methods. A
new engineering correlation formula is proposed for wall stagnation temperature
distribution during reentry motion. The efficiency of the applied analysis gives
satisfactory results compared with published data of verified experiments and
computational codes for the lifting Space Shuttle STS-40 and ballistic Apollo4
capsule missions.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Convective Heat Transfer, High Temperatures, Hypersonic Flight, Real Gas
Properties, Wall temperature.
Nonlinear Optimal Closed-Loop Guidance Law for Lunar Landing Mission Using
Perturbation Feedback Control
by H. H. Afshari, N. Rostamy, I. S. Nejad, A. B. Novinzadeh
Abstract
- An optimal trajectory design of a nonlinear lunar landing mission for soft
landing on the moon by minimizing the landing time is reported in this paper. It
is an exact solution to the two-point boundary value problem which determines
the state variables and optimal control history in the open-loop form by
satisfying the terminal conditions. Furthermore, in this paper the lunar landing
mission is closed-loop against the environment disturbances by using of optimal
open-loop solution and applying an analytical method named perturbation feedback
control. By using the perturbation feedback method based on the calculus of
variations theory, one can compute the feedback control law for nonlinear lunar
landing mission in each instant of time. This law is a function of states
perturbation and constraints perturbation which can minimize the landing time
and satisfy the terminal conditions appropriately.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Closed-loop Optimal Control, Nonlinear Terminal Guidance, Perturbation Feedback
.
Optimal
Prolonged Spacecraft Rendezvous Using Tethers
by P. Williams, C. Blanksby
Abstract
- Many proposed scenarios for capturing non-cooperative payloads using tethers
involve instantaneous rendezvous at the tether tip. This paper examines the
possibility of extending the proximity time of the capture device and the
payload by utilizing an actuator mass that “crawls” along the tether. The
prolonged rendezvous maneuver is studied using optimal control methodology, and
the effect of various system parameters such as system mass ratios and
rendezvous windows are examined. In addition, the requirements for the
precapture maneuver are also studied. Close proximity times on the order of
several minutes are possible.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Spacecraft rendezvous, tethered satellites, tethered elevator, optimal control,
pseudospectral.
Logging Airplane Sensors Measurements to a Remote Database Using LabVIEW and
FieldPoint
by M. Lascu
Abstract
- Using the networking features in LabVIEW (graphical programming) it is
possible to perform following tasks: share live data with other VIs (virtual
instruments) running on a network, publish front panel images and virtual
instruments documentation on the web, build virtual instruments that communicate
with other applications and virtual instruments through low-level protocols. The
main task of the paper is to create a virtual instrument for acquisition,
control and monitoring temperature in eight points inside of an airplane, to
create storage of the data in data files and to send the files to Remote
Computers, that means to log temperature data to Remote Databases.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Airplane, Acquisition, Control, Fieldpoint, Graphical Programming, Labview,
Monitoring, Remote Computers, Remote Databases.
Vibration of Cracked Composite Beams: A Dynamic Finite Element
by S. M. Hashemi, S. R. Borneman, H. Alighanbari
Abstract
- A Dynamic Finite Element (DFE) is developed to analyze the vibration
characteristics of cracked composite beams. Stress intensity factors, corrected
for geometry and material anisotropy, have been used to develop the local
flexibility of a through-thickness cracked uniform laminated unidirectional
unbalanced beam. By exploiting the principle of virtual work and the Dynamic
Trigonometric Shape Functions (DTSF’s), developed from the exact solutions to
the equations governing uncoupled flexural and torsional vibrations of the
system, the element Dynamic Stiffness Matrix (DSM) is developed. By implementing
the local flexibility of crack, the element matrices exhibiting both mass and
stiffness properties are then assembled and the boundary conditions are applied
to form the eigenproblem of the overall system. The natural frequencies and
modes are then extracted using the well-known Wittrick–William (W-W) root
counting algorithm. Numerical tests are conducted for a flat, solid rectangular
cross-section, uniform, cantilever, laminated composite beam. Both intact and
damaged scenarios (for cracks located at 20% and 50% of beam length), with
various crack ratios, , and ply angles, , are investigated. Numerical results
on natural frequencies and convergence tests demonstrate the higher accuracy and
faster convergence of the proposed DFE and its superiority over the classical
Finite Element Methods (FEM).
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Bending-Torsion Couplings, Cracked Composite Beam, Dynamic Finite Element (DFE),
Dynamic Stiffness Matrix, FEM, Materially Coupled Vibrations.
Enterprise Risk Optimization Model with Using Risk Analysis Tools and ANP-based
Approach
by A. Kucuk Yilmaz
Abstract
- Enterprise risk optimization (ERO) is considered as building stone to
establish Enterprise Risk Management (ERM) in the airport business. In this
study, ERO model is deal with solving “how is optimal risk amount determine?”
main question and the new model has been developed for solving of this problem.
This paper is prepared to offer a new approach to corporate risk optimization by
ERO model. The model is consisted of five steps: corporate swot analysis,
determining risk appetite, prioritization of enterprise-wide risks using with
newly created risk score formula and Analytic Network Process (ANP)-based
approach, determining risk tolerance level, developing corporate risk profile
and corporate risk mapping. ERO model is prepared to TAV Holding Co. So, this
study is offered the sample as real world situation.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Corporate Risk score formula Enterprise Risk Management, Enterprise Risk
Optimization.
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