7,338 research outputs found
Optimal design of a composite wing structure for a flying-wing aircraft subject to multi-constraint
No full textThis thesis presents a research project and results of design and optimization of a composite wing structure for a large aircraft in flying wing configuration. The design process started from conceptual design and preliminary design, which includes initial sizing and stressing followed by numerical modelling and analysis of the wing structure. The research was then focused on the minimum weight optimization of the /composite wing structure /subject to multiple design /constraints. The modelling, analysis and optimization process has been performed by using the NASTRAN code. The methodology and technique not only make the modelling in high accuracy, but also keep the whole process within one commercial package for practical application.
The example aircraft, called FW-11, is a 250-seat commercial airliner of flying wing configuration designed through our MSc students Group Design Project (GDP) in Cranfield University. Started from conceptual design in the GDP, a high-aspect-ratio and large sweepback angle flying wing configuration has been adopted. During the GDP, the author was responsible for the structural layout design and material selection. Composite material has been chosen as the preferable material for both the inner and outer wing components. Based on the derivation of structural design data in the conceptual phase, the author continued with the preliminary design of the outer wing airframe and then focused on the optimization of the composite wing structure. Cont/d
Optimal design of a flying-wing aircraft inner wing structure configuration
No full textFlying-wing aircraft are considered to have great advantages and potentials in
aerodynamic performance and weight saving. However, they also have many
challenges in design. One of the biggest challenges is the structural design of
the inner wing (fuselage). Unlike the conventional fuselage of a tube
configuration, the flying-wing aircraft inner wing cross section is limited to a
noncircular shape, which is not structurally efficient to resist the internal
pressure load. In order to solve this problem, a number of configurations have
been proposed by other designers such as Multi Bubble Fuselage (MBF),
Vaulted Ribbed Shell (VLRS), Flat Ribbed Shell (FRS), Vaulted Shell
Honeycomb Core (VLHC), Flat Sandwich Shell Honeycomb Core (FLHC), Y
Braced Box Fuselage and the modified fuselage designed with Y brace
replaced by vaulted shell configurations. However all these configurations still
inevitably have structural weight penalty compared with optimal tube fuselage
layout. This current study intends to focus on finding an optimal configuration
with minimum structural weight penalty for a flying-wing concept in a preliminary
design stage.
A new possible inner wing configuration, in terms of aerodynamic shape and
structural layout, was proposed by the author, and it might be referred as
‘Wave-Section Configuration’. The methodologies of how to obtain a structurally
efficient curvature of the shape, as well as how to conduct the initial sizing were
incorporated.
A theoretical analysis of load transmission indicated that the Wave-Section
Configuration is feasible, and this was further proved as being practical by FE
analysis. Moreover, initial FE analysis and comparison of the Wave-Section
Configuration with two other typical configurations, Multi Bubble Fuselage and
Conventional Wing, suggested that the Wave-Section Configuration is an
optimal design in terms of weight saving. However, due to limitations of the
author’s research area, influences on aerodynamic performances have not yet
been taken into account
Influence of wing kinematics on aerodynamic performance in hovering insect flight
No full textThe influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied. The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.Aerospace Design, Integration and OperationsAerospace Engineerin
Preliminary fuselage structural configuration of a flying-wing type airline
No full textThe flying-wing is a type of configuration which is a tailless airplane accommodating all of its parts within the outline of a single airfoil. Theoretically, it has the most aerodynamic efficiency. The fuel consumption can be more efficient than the existed conventional airliner. It seems that this configuration can achieve the above mentioned requirements.
According to these outstanding advantages, many aircraft companies did a great deal of projects on the flying-wing concept. However, the application was only for sport and military use; for airliner, none of them entered production.
FW-11 is a flying-wing configuration airliner which is a design cooperation between Cranfield University and Aviation Industry Corporation of China (AVIC). Aiming the spatial economic and environmental needs, this 200-seat airliner would attract attention from airline companies for cost saving and environmental protection.
Before start, this program is designated for a new generation commercial aircraft to compete with the existing same capability airliner, such as Airbus A320 and Boeing 767. As the first team of this program, the aim is to finish the conceptual design and prepare the relevant document for next two teams that will perform preliminary and detail design.
As a member of FW-11 program and as part of the GDP, the author has been through the four conceptual design stages: engine manufacturers, aircraft family issues, structure design and the establishment of 3-D CAD model.
The aim of IRP study is to focus on the initial fuselage design
Analysis of composite wing structures with a morphing leading edge
No full textOne of the main challenges for the civil aviation industry is the reduction of its environmental impact. Over the past years, improvements in performance efficiency have been achieved by simplifying the design of the structural components and using composite materials to reduce the overall weight. These approaches however, are not sufficient to meet the current demanding requirements set for a „greener‟ aircraft.
Significant changes in drag reduction and fuel consumption can be obtained by using new technologies, such as smart morphing structures. These concepts will in fact help flow laminarisation, which will increase the lift to drag ratio. Furthermore, the capability to adapt the wing shape will enable to optimise the aerodynamic performance not only for a single flight condition but during the entire mission. This will significantly improve the aircraft efficiency.
The current research work has been carried out as part of the European Commission founded Seventh Framework Program called „Smart High Lift Device for the Next Generation Wing‟ (SADE), which main aim is to develop and study morphing high lift devices. The author‟s investigation focused on developing a design concept for the actuation mechanism of a morphing leading edge device. A detailed structural analysis has been carried out in order to demonstrate its feasibility.In the first phase of the research the attention was directed on the preliminary design and analysis of the composite wing box. The parameters of the key structural components, such as skin, spars, ribs and stringers were set to satisfy the static stress and buckling requirements. Moreover, numerical and experimental studies were conducted to analyse the static failure and buckling behaviour of two typical composite wing structural components: a spar section and a web and base joint assembly.
In the second stage of the research, a design for the morphing leading edge actuation mechanism was developed. The actuation system was designed in such a way that the target shape was reached with minimum actuation force demand. A geometrical nonlinear FE analysis was conducted to simulate the leading edge morphing deflection and ensure that structural strength requirements were satisfied. Furthermore, the behaviour of the skin integrated with the internal actuation mechanism was modelled under the aerodynamic pressure, at different flight conditions and gust loads, in order to prove that the proposed actuation system can compete with the conventional rigid rib.
This study demonstrated that a feasible morphing leading edge design for a next generation large aircraft wing can be achieved. Developing the readiness of this technology will have a significant impact on aircraft efficiency and considerable contribution towards a more environmental friendly aviation
Aeroacoustic interactions of installed subsonic round jets
No full textAdditional noise sources are generated when an aircraft engine is mounted beneath a wing. The two main installation sources include: (1) reflection of the exhaust jet mixing noise from the underside of the wing, and (2) interaction between the turbulent jet plume and the trailing edge of the wing, or deployed flap. The strength, directivity and frequency content of these particular sources all serve to increase the time-averaged flyover aircraft noise level heard on the ground by residents beneath the flight path. As the bypass ratio and nacelle diameter of modern turbofan engines continues to increase, constraints on ground clearance are forcing under-wing-mounted engines to be coupled more closely to the wing and flap system, which, in turn, serves to accentuate both of these noise sources. Close-coupled nacelle-airframe designs are now a critical issue surrounding efforts to meet the future environmental targets for quieter civil aircraft.This research is principally aimed at understanding and predicting the groundpropagating noise generated by the latter of these two installed jet noise sources. In order to characterise the jet-surface interaction noise source, however, it is first necessary to isolate it. A small 1/50th model-scale acoustic experiment, therefore, is conducted in a semi-anechoic university laboratory using a single stream jet installed beneath a flat plate. Both far-field acoustic and near-field plate surface pressure data are measured to investigate the jet-surface interaction noise source. Results from this fundamental experiment are then used to help drive a larger, and more realistic, 1/10th modelscale test campaign, at QinetiQ's Noise Test Facility, where 3D wing geometry effects, Reynolds number scaling effects and static-to-flight effects are investigated. A jet-flap impingement tonal noise phenomenon is also identified and investigated at particularly closely-coupled jet-wing configurations. Finally, the first version of a fast, semi-empirical engineering tool is developed to predict the additional noise caused by jet-wing interaction noise, under static ambient flow conditions. It is hoped that this tool will serve to inform future commercial aircraft design decisions and, thus, will help to protect the acoustic environment of residents living beneath flight paths
Direct numerical simulation of the flow around a wing section at moderate Reynolds numbers
No full textA three dimensional direct numerical simulation has been performed to study the flow around the asymmetric NACA-4412 wing at a moderate chord Reynolds number (Rec = 400, 000) with an angle of attack of 5◦ . The flow case under investigation poses numerous challenges for a numerical method due to the wide range of scales and complicated flow physics induced by the geometry. The mesh is optimized and well resolved to account for such varying scales in the flow. An unsteady volume force is used to trip the flow to turbulence on both sides of the wing at 10% chord. Full turbulent statistics are computed on the fly to further investigate the complicated flow features around the wing. The present simulation shows the potential of high-order methods in simulating complex external flows at moderately high Reynolds numbers
The aerodynamic design and optimization of a wing-fuselage junction fillet as part of a multi-disciplinary optimization process during the early aircraft design stages
No full textAn attempt to minimize interference drag in a wing-fuselage junction by means
of inserting a fillet is presented in this thesis. The case of a low-wing com-
mercial transport aicraft at cruise conditions is examined. Due to the highly
three dimensional behaviour of the flow field around the junction, a thin-layer
Navier-Stokes code was implemented to estimate the drag forces at the junc-
tion. Carefully selected design variable combinations based on-the theory of
Design of Experiments constituted the initial group of feasible cases for which
the flow solver had to be run. The drag values of these feasible cases were then
used to create a second order response surface which could predict with rea-
sonable accuracy the interference drag given the value of the design variables
within the feasible region. A further optimization isolated the minimum in-
terference drag combination of design variable values within the design space.
The minimurn interference drag combination of design variable values was eval-
uated numerically by the flow solver. The prediction of the response surface
and the numerical value obtained by the flow solver for the interference drag
of the optimal wing-fuselage combination differed by less than five percent. To demonstrate the ability of the method to be used in an interdisciplinary
analysis and optimization program, a landing gear design module is included
which provides volume constraints on the fillet geometry during the fillet sur-
face definition phase.
The Navier Stokes flow analyses were performed on the Cranfield Cray su-
percomputer. Each analysis required between eight to twelve CPU hours, and
the total CPU time required for the optimization of the six variable model
described in the thesis required thirty Navier Stokes runs implementing the
Design of Experimens and Surface Response Methodology implementation.
For comparison, a typical optimization implementing a classical conjugate di-
rections optimizer with no derivative information available would probably
require more than forty iterations.
Both the optimization and the flow solver results are discussed and some
recommendations for improving the efficiency of the code and for further ap-
plications of the method are given
Wing Sweeping Mechanism for Active Control and Stabilisation of a Flapping Wing MAV
No full textDuring flight, natural fliers flap, twist and bend their wings to enhance flight performance. Lift and thrust benefit from flexibility as well as from both passive and active wing deformation. At the same time, the active deformations are used for flight control. In this study, we investigate strategies of control moments generation in a bio-inspired flapping-wing micro air vehicle (FWMAV). In particular, we propose a method for active control and attitude stabilization by introducing a wing deformation through adjustable wing sweep. The control method is demonstrated on a tailless FWMAV with independent wing sweep modulation on each of its four wings. The actuation mechanism consists of an arm joint at the leading edge, about which the wings are swept. Forces from the servo actuation are transferred to the leading edge of the robot through strings. The actuated strings alter the wing sweep, which affects the roll and pitch movement via different combinations of string pulls. The effectiveness of the designed mechanism is being evaluated on the basis of tethered force balance tests and free flight tests. An advantage of the proposed mechanism is its lightweight design, which is crucial for small FWMAVs with stringent weight restrictions.Control & Simulatio
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