bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics and Control of Single-Line Kites
Authors: Sánchez G. 
Published: February 2016

AbstractThis paper presents a dynamic analysis of a single-line kite with two degrees of freedom. A Lagrangian formulation is used to write convenient equations of motion. The equilibrium states of the system and their stability are studied; Eigenvalues and eigenmodes are calculated by using linear theory. The stability in the parametric plane δ – W0 is discussed, where δ defines the bridle geometry and W0 is wind velocity. The system goes through a Hopf bifurcation and periodic branches of solutions appear. The orbits and their stability have been calculated numerically using Floquet theory and wind velocity seems to play an important role in their existence. Finally the kite response against gusts is considered and an open loop control system developed to keep the flight altitude invariant under changing atmospheric conditions. Modifying the bridle’s geometry seems to be a convenient way to control a kite’s performance.
Longitudinal flight control design with handling quality requirements
Authors: Saussié D. , Saydy L. , Akhrif O. 
Published: February 2016

AbstractThis work presents a method for selecting the gain parameters of a C* control law for an aircraft’s longitudinal motion. The design incorporates various handling quality requirements involving modal, time- and frequency-domain criteria that were fixed by the aircraft manufacturer. After necessary model order-reductions, the design proceeds in essentially two-steps: stability augmentation system (SAS) loop design and control augmentation system (CAS) loop design. The approach partly relies on the use of guardian maps to characterise, in each case, the set of gain parameters for which desired handling quality requirements are satisfied. The approach is applied throughout the full flight envelope of a business jet aircraft and yields satisfactory results.
Single and multi–objective UAV aerofoil optimisation via hierarchical asynchronous parallel evolutionary algorithm
Authors: Gonzalez L. F. , Lee D. S. , Srinivas K. , Wong K. C. 
Published: February 2016

AbstractUnmanned aerial vehicle (UAV) design tends to focus on sensors, payload and navigation systems, as these are the most expensive components. One area that is often overlooked in UAV design is airframe and aerodynamic shape optimisation. As for manned aircraft, optimisation is important in order to extend the operational envelope and efficiency of these vehicles. A traditional approach to optimisation is to use gradient-based techniques. These techniques are effective when applied to specific problems and within a specified range. These methods are efficient for finding optimal global solutions if the objective functions and constraints are differentiable. If a broader application of the optimiser is desired, or when the complexity of the problem arises because it is multi-modal, involves approximation, is non-differentiable, or involves multiple objectives and physics, as it is often the case in aerodynamic optimisation, more robust and alternative numerical tools are required. Emerging techniques such as evolutionary algorithms (EAs) have been shown to be robust as they require no derivatives or gradients of the objective function, have the capability of finding globally optimum solutions among many local optima, are easily executed in parallel, and can be adapted to arbitrary solver codes without major modifications. In this paper, the formulation and application of a evolutionary technique for aerofoil shape optimisation is described.Initially, the paper presents an introduction to the features of the method and a short discussion on multi-objective optimisation. The method is first illustrated on its application to mathematical test cases. Then it is applied to representative test cases related to aerofoil design. Results indicate the ability of the method for finding optimal solutions and capturing Pareto optimal fronts.
Thermal buckling of a thin uniform circular disk: a comparison of predictions
Authors: Seffen K. A. 
Published: February 2016

AbstractThe conditions for thermally-induced buckling of an unloaded thin, circular disk are compared from two well-known but unconnected studies: an approximate solution by Freund for a constant thickness disk, which must neglect the free edge condition, and an exact solution by Mansfield but only for a disk whose thickness tapers to zero in a particular manner. It is shown that buckling occurs at slightly higher values compared to a finite element analysis of a constant thickness disk but that the case of variable thickness seems to offer a closer result, which suggests that it better models the boundary layer behaviour near the free edge.
Considerations for UAV design and operation in South African airspace
Authors: Ingham L. A. , Jones T. , Maneschijn A. 
Published: February 2016

AbstractAt present, the lack of UAV regulations and standards precludes UAVs from being certified to operate commercially in un-segregated civilian airspace. Because of strategic, economical and security requirements, it is necessary to devise a method to operate UAVs in South African airspace within existing regulatory arrangements. This paper suggests specific UAV missions, viz; maritime patrol/boarder control, search and rescue, and cargo transport, together with design considerations and possible concepts of UAV; operations, maintenance and training, that will enable UAVs to satisfy the immediate South African strategic requirements whilst further UAV standards and regulations are being developed.
Computational and experimental
investigations of low-Reynolds-number flows past an
aerofoil
Authors: Yuan W. , Khalid M. , Windte J. , Scholz U. , Radespiel R. 
Published: February 2016

AbstractThis paper presents investigations of
low-Reynolds-number flows past an SD7003 aerofoil at
Re = 60k, where transition takes place across a
laminar separation bubble (LSB). Results of
experimental measurements and numerical calculations
are analysed and discussed. In particular,
reasonably good results were obtained using two
different numerical approaches: Large-eddy
simulation (LES) that demonstrated vortical
structures at different transition stages, and where
the transition occurred naturally; unsteady
Reynolds-averaged Navier-Stokes (URANS) simulations
for several turbulence models based on the
ω-length-scale equation, coupled to a linear
stability solver to predict the transition
position.
Effect of stagnation temperature on
supersonic flow parameters application for air in
nozzles
Authors: Zebbiche T. , Youbi Z. 
Published: February 2016

AbstractWhen the stagnation temperature of a perfect gas
increases, the specific heats and their ratio do not
remain constant and start to vary with the
temperature. The gas remains perfect; its state
equations remain valid, so it can be named as
calorifically imperfect gas. The aim of this
research is to develop the necessary thermodynamic
and geometrical equations and to study the
supersonic flow at high temperature, lower than the
dissociation threshold. The results are found by the
resolution of nonlinear algebraic equations and
integration of complex analytical functions where
the exact calculation is impossible. The dichotomy
method is used to solve the nonlinear equations and
Simpson’s algorithm for the numerical integration
applied. A condensation of the nodes is used. The
functions to be integrated have a high gradient at
the extremity of the interval of integration. The
comparison is made with the calorifically perfect
gas to determine the error. The application is made
for air in a supersonic nozzle.
Aircraft flight characteristics in
conditions of windshear and icing
Authors: Cao Yihua , Yuan Kungang 
Published: February 2016

AbstractComplex weather conditions, especially windshear and
icing encounter, have severe effects on aircraft
flight safety. The effect of low-altitude windshear
and ice accretion on aircraft performance and
control has been studied in this paper. With the
employment of a windshear model and nonlinear
inverse dynamics (NID) method, a low-altitude
windshear penetration flight control law is
designed. The effect of ice accretion was modeled on
the stability and control of an aircraft. Several
icing parameters are imported to the small
disturbance flight dynamics model to calculate the
change of performance, stability and control
derivatives between clean and iced aircraft. These
derivatives were used to calculate the elevator, the
aileron and the rudder step responses to investigate
the icing effect.The simulation results indicate that the NID control
logic works effectively in the trajectory control of
the aircraft during the penetration of windshear.
The method used to study the effect of ice accretion
on aircraft is valid and it can provide data for
real-time calculation for icing encounter.
New commercial opportunities in space
Authors: Ashford D. M. 
Published: February 2016

AbstractThis paper assesses new commercial opportunities in space. The main conclusion is that spaceplanes can reduce the cost of human transport to orbit sufficiently for large new commercial markets to develop. Combining the reusability of spaceplanes with the high traffic levels of space tourism offers the prospect of a thousandfold reduction in the cost per seat to orbit. The result will be airline operations to orbit involving dozens of spaceplanes, each capable of one or two flights per day. These low costs will make possible a rapid expansion of space science and exploration.The prototype of a small orbital spaceplane, needed to trigger this line of development, could be developed in about six years at a cost comparable to one or two flights of the Space Shuttle. It might be possible to progress from this prototype to airline operations within ten years, given a massive development effort.
Performance of non-rigid airships operating in the neutral buoyancy condition
Authors: Dorrington G. E. 
Published: February 2016

AbstractThe feasibility of using neutrally-buoyant (or fully-buoyant) airships for passenger and cargo transportation is investigated. The drag coefficients of rigid and non-rigid airships are deduced from flight data. Comparisons are made with empirical drag formulas and previous wind tunnel data. Some general trends for airship drag are derived. The mass breakdown of non-rigid airships with hull volumes up to 35,000m3is analysed using parametric equations. The maximum feasible airspeed and useful load carrying capacity of projected airships are calculated. ‘Specific productivity’ is found to be lower than values achievable with fixed-wing aircraft, but ‘fuel-specific productivity’ is found to be competitive, confirming results of a previous NASA study. The use of gaseous hydrogen and fuel cells is briefly discussed.
A review of supersonic business jet design Issues
Authors: Smith H. 
Published: February 2016

AbstractKey issues relating to the Supersonic Business Jet (SBJ) concept are reviewed with the intent to assess the readiness of enabling technologies and hence the concept itself. The multidisciplinary nature of aircraft design precludes an in-depth analysis of each specific aspect, which could individually be the subject of a separate discipline review, hence an overview is presented.The review looks at the market, environmental issues, with particular reference to the sonic boom phenomenon & solutions, technological issues, including prediction methods, flight testing, systems, certification and interested aerospace companies and design organisations.It is apparent that the need to reduce the sonic boom signature is vital if the vehicle is to be permitted to operate over land and hence be economically viable. It is clear that sonic boom acceptability requirements must be set if resources are to be effectively focused and designs are to converge. Despite this challenge, considerable investment is aimed at de-risking many of the enabling technologies and raising readiness levels. Many technologies are moving beyond theoretical and numerical analysis into the experimental and flight test domains. Collaboration between the civil and military sectors is increasing.Clearly, supersonic air travel is not an efficient means of personal conveyance; however, concerns for the environment are difficult to balance against the ‘value of time’ benefits offered by the SBJ concept. Air travel, of which this is a specialised form, is important to the global economy. Continued effort in the areas of human factors, customer demand and certification & requirements would be beneficial.
A model for solar powered aircraft preliminary design
Authors: Rizzo E. , Frediani A. 
Published: February 2016

AbstractSolar powered aircraft are becoming more and more interesting for future long endurance missions at high altitudes, because they could provide Earth monitoring, telecommunications, etc. without any atmospheric pollution and, hopefully in the near future, with competitive costs compared with satellites. The research activities carried out till now have been mainly focused on flying wings or conventional aircraft configurations, with a great emphasis on the technological aspects. The present paper aims to define a mathematical model for solar powered aircraft preliminary design, valid independently of the aerodynamic configuration. A preliminary analysis is carried out in order to simulate Helios and the results are compared with those available from the flights of this aircraft. The proposed mathematical model is used also to compare four different aircraft configurations, namely: a flying wing, a conventional aircraft, a twin boom aircraft and a biplane aircraft. The results obtained are discussed in the paper and an optimum aircraft is analysed.
What price supersonic speed? A design anatomy of supersonic transportation Part 1
Authors: Chudoba B. , Coleman G. , Oza A. , Czysz P. A. 
Published: February 2016

AbstractThe first generation of supersonic commercial transportation has seen three serious attempts to arrive at an economically and environmentally viable aircraft. The US B2707-200/300 design was cancelled early before a prototype could emerge; the Russian Tu-144 design succeeded to become the first supersonic transport but spanned only a few years of restricted airline service; the Anglo-French Concorde endured more than 27 glamorous airline service years until the last of its species was retired on 30 August 2003. This first generation was followed by a second generation of supersonic commercial transport projects in the time period between 1986 until about 1999, designs which did not proceed towards the production hardware stage. This study critically examines the anatomy of two generations of supersonic commercial transport design failures and successes in order to arrive at lessons learned free of ‘wishful thinking’. The design conditions leading to the identification of the product ‘solution space’ for an economically and environmentally acceptable supersonic commercial transport are discussed. Having assembled an understanding of the product metrics valid for supersonic commercial transports, the paper then provides an outlook for the first generation of supersonic corporate and cargo jet projects. This first generation of supersonic business jet (SSBJ) and supersonic cargo jet (SSCJ) projects spans a period of nearly two decades of development, starting from 1988 until today. The present study identifies that the product development metrics of this class of aircraft is radically different compared to the metrics valid for supersonic commercial transports. The challenges in VIP transportation and dedicated freight transportation at supersonic speeds are portrayed leading to two principal trains of thought targeting the development of the first supersonic business jet and/or supersonic cargo jet hardware: the development based on a new airframe, and alternatively the development based on an existing airframe.
Dynamic performance investigations of a turbojet engine using a cross-application visual oriented platform
Authors: Kyprianidis K. G. , Kalfas A. I. 
Published: February 2016

AbstractThis paper presents the development of visual oriented tools for the dynamic performance simulation of a turbojet engine using a cross-application approach. In particular, the study focuses on the feasibility of developing simulation models using different programming environments and linking them together using a popular spreadsheet program. As a result of this effort, a low fidelity cycle program has been created, capable of being integrated with other performance models. The amount of laboratory sessions required for student training during an educational procedure, for example for a course in gas turbine performance simulation, is greatly reduced due to the familiarity of most students with the spreadsheet software. The model results have been validated using commercially available gas turbine simulation software and experimental data from open literature. The most important finding of this study is the capability of the program to link to aircraft performance models and predict the transient working line of the engine for various initial conditions in order to dynamically simulate flight phases including take-off and landing.
Aerodynamic load characterisation of a low speed aerofoil using particle image velocimetry
Authors: van Oudheusden B. W. , Casimiri E. W. F. , Scarano F. 
Published: February 2016

AbstractParticle image velocimetry (PIV) measurements of the flow around a wing section are employed as a basis for non-intrusive aerodynamic mean loads characterisation, providing sectional lift, drag and pitching moment. The technique relies upon the application of control-volume approaches in combination with the deduction of the pressure from the PIV experimental data through application of the momentum equation. The treatment can also be applied when the flow is unsteady; in that case time-mean loads are obtained from velocity statistics, through the use of Reynolds-averaged formulation of the governing equations. The procedure was applied in the experimental investigation of a NACA 642A015 aerofoil, in which the PIV approach is validated against standard pressure-based methods (surface pressure distribution and wake rake). The chord Reynolds number considered in the investigation ranges between 1 – 7 × 105. In addition, the consistency and potential performance of the method was assessed by means of synthetic velocity field data obtained from a numerical flow simulation.
Whirl flutter analysis of prop-rotors using unsteady aerodynamics reduced-order models
Authors: Gennaretti M. , Greco L. 
Published: February 2016

AbstractThe prediction of this aeroelastic phenomenon is an urgent need of the designer and requires devoted numerical tools. This work examines the influence of the accuracy of the aerodynamic modelling on whirl flutter analysis, with particular attention to those models that can conveniently be applied to preliminary design and control purposes. Considering a simple pylon/prop-rotor structure, the aeroelastic instability boundaries are identified by 2D quasi-steady and 2D unsteady aerodynamics theories, along with a 3D unsteady, potential flow BEM solver. A methodology for deriving reduced-order models from unsteady aerodynamic solutions is used. The numerical investigation highlights that the accuracy of the aerodynamic solver included in the analysis may be of crucial importance. The use of 2D aerodynamic models does not always guarantee conservative stability predictions, and this is particularly true for three-bladed rotors where a fully 3D unsteady solver coupled with a wake alignment algorithm seems to be necessary.
Linear theory of optimum hot air balloon performance – application to Titan
Authors: Lorenz R. D. 
Published: February 2016

AbstractWe develop a simple theory for hot air balloon performance with fixed thermal power and linear heat transfer to the environment, applicable to low-temperature situations such as Titan’s atmosphere. The theory results in a closed-form solution and it is shown that an optimum balloon diameter exists – the maximum payload is achieved when the envelope mass and payload mass are equal. It is also shown simply that the floating mass for a given power has a stronger sensitivity to heat transfer coefficient than to the envelope specific mass. A hot air balloon on Titan with a ~2kW heat source could loft a theoretical maximum payload of ~195kg or ~100kg with appropriate margins.
Transitional separation bubbles and unsteady aspects of aerofoil stall
Authors: Sandham N. D. 
Published: February 2016

AbstractA time-accurate solution method for the coupled potential flow and integral boundary-layer equations is used to study aerofoils near stall, where laboratory experiments have shown high-amplitude low-frequency oscillations. The laminar-turbulent transition model incorporates an absolute instability formulation, which allows the transition process in separation bubbles to be sustained in the absence of upstream disturbances, in agreement with recent direct numerical simulations. The method is demonstrated to capture large scale flow oscillations with Strouhal numbers and amplitudes comparable to experiments. The success of this particular physical model suggests that bubble bursting is primarily due to a potential-flow/boundary-layer interaction effect, in which relatively simple models of boundary layer transition and turbulence suffice to describe the key phenomena.
Cold flow analysis of trapped vortex combustor using two equation turbulence models
Authors: Selvaganesh P. , Vengadesan S. 
Published: February 2016

AbstractA new combustor concept referred as the trapped vortex combustor (TVC) employs a vortex that is trapped inside a cavity to stabilise the flame. The cavity is formed between two axisymmetric disks mounted in tandem. TVC offers many advantages when compared to conventional swirl stabilisers. In the present work, numerical investigation of cold flow (non-reacting) through trapped vortex combustor is performed. The numerical simulation involves passive flow through TVC to obtain an optimum cavity size to trap stable vortices inside the cavity and to observe the important characteristics of TVC. One of the main objectives is to evaluate various two equation turbulence models for the aerodynamic predictions of TVC. Commercial CFD software Fluent is used for the present study. In addition to many models available, Non-linear k-ω and modified k-ω models are incorporated through user defined functions. Results obtained include streamlines, residence time and entrainments for all models. The reattachment length obtained by non-linear k-ω model closely matches with that obtained by DNS in the case of forebody-spindle alone. Non-linear k-ω model alone captures the corner vortices while all the other models failed to capture. From the entrainment characteristics study, it is inferred that the primary air needs to be injected for accommodating the decrease in oxidizer inside the cavity to obtain better performance from the TVC.