College Of Aeronautics Research Articles

Aeroservoelastic Analysis for Transonic Missile Based on Computational Fluid Dynamics

Aeroservoelastic Analysis for Transonic Missile Based on Computational Fluid Dynamics

Fractional Calculus in Biomechanics: A 3D Viscoelastic Model Using Regularized Fractional Derivative Kernels with Application to the Human Calcaneal Fat Pad

A viscoelastic model of the K-BKZ (Kaye, Technical Report 134, College of Aeronautics, Cranfield 1962; Bernstein et al., Trans Soc Rheol 7: 391-410, 1963) type is developed for isotropic biological tissues and applied to the fat pad of the human heel. To facilitate this pursuit, a class of elastic solids is introduced through a novel strain-energy function whose elements possess strong ellipticity, and therefore lead to stable material models. This elastic potential - via the K-BKZ hypothesis - also produces the tensorial structure of the viscoelastic model. Candidate sets of functions are proposed for the elastic and viscoelastic material functions present in the model, including two functions whose origins lie in the fractional calculus. The Akaike information criterion is used to perform multi-model inference, enabling an objective selection to be made as to the best material function from within a candidate set.

Cranfield University Joins ‘Silent’ Aircraft Initiative

Cranfield started life in 1946 as a graduate College of Aeronautics. In 1969 a royal charter was granted, which saw the name change to Cranfield Institute of Technology, and then in 1993 it became Cranfield University. Today it has a world-wide reputation as a centre of excellence in aviation. Its facilities include its own aircraft for flight-test operations and, through collaboration with Cranfield Aerospace Limited, the ability to design, build and fly aircraft. It also has relationships with leading aerospace and aviation companies worldwide.

The more electric aircraft—assessing the benefits

The concept of the more electric aircraft (MEA), where electrical power is used for at least some of the on-board functions at present powered by hydraulics and pneumatics, has many claimed benefits and is far from new. However, almost all larger aircraft retain hydraulics and pneumatics.Over recent years there has been a great deal of interest in the MEA concept, with developments in relevant technologies and their adoption in other areas of engineering. In support of UK efforts on this and related concepts, the College of Aeronautics has been performing studies since the mid 1980s to assess the benefits of changes. This paper describes the background to these studies and the relationships between them as well as some of their findings, concluding that it is important that such assessment work should be continued in the future.

Graduate-level design education, based on flight demonstrator projects

The College of Aeronautics (CoA) at Cranfield University believes that the best way of teaching design is for the students to learn design by doing it, in a structured manner. It also believes in the maxim – “the devil is in the detail” and that a design is only complete when it has been built, flown and certificated. Designers need to be aware of, and experienced in, all of the intermediate stages between concept design and certification. They also need to be taught to function as members of group design teams, because that is the usual way that Industry works. All of these factors led to the establishment of a full-time Masters programme in Aerospace Vehicle Design, the focus of which is the Group Design Project (GDP). This philosophy was proved to be successful over many years and was continued and expanded in the design of the Masters course in Aircraft Engineering – the subject of this paper. This programme is a three-year part-time M.Sc. course, which comprises the same major elements as the full-time course. The students attend lecture modules, perform a piece of individual research and work on a GDP. It was this last element that particularly attracted the launch and predominant customer for the course, the then Military Aircraft Division of British Aerospace (BAe). BAe like the basic philosophy of teaching the design process by placing someone in a project group with an individual responsibility but having to cater for the needs of the group and project as a whole. In February 1995 the Aircraft Engineering course was launched with 15 students, who began the first intake, working on major modifications to the CoA's A1 Aerobatic aircraft, which itself resulted from work of former students. The GDP on the full-time course in Aerospace Vehicle Design concentrates on the preliminary and detail design of a whole aircraft, which has been previously defined in terms of basic geometry, mass, performance, characteristics etc. by staff. However, BAe and Cranfield wished to address a greater extent of the full-design process, as mentioned above. In this way the students would, in the space of three years, be given first-hand experience of a much wider extent of an aerospace project than could ever be the case whilst working on major aircraft projects in a manufacturing company. This paper will give details of the Aircraft Engineering teaching programme and describe the first GDP, a major modification programme and flight of the Cranfield A1 Aerobatic Aircraft. The students were set the task of modifying the existing single seat aircraft to a two-seat configuration with performance similar or better than that of the existing aircraft, despite the weight increase of a second pilot. At approximately one year into the project, a joint BAe/CoA decision was made to progress the project to completion with an `affordable’ set of modifications, providing the basic two seat capability, increased endurance, and approaching the desired performance. The aircraft was modified by BAe and CoA personnel and successfully completed its official first flight on the 30th September 1998 at Cranfield's own airfield, flown by its own Chief Test Pilot, thus completing the first of the 5 GDPs described in this paper. Information will also be given of progress being made on more recent intakes of students. The subject for intake 2 was further modifications to the A1 to further improve its lateral manoeuvrability by means of a new composite vertical stabiliser and rudder. Intakes 3 and 4 are capitalising on Cranfield's extensive expertise in the design and flight-testing of small UAV's, to develop jet-powered UAVs to act as flight-test demonstrators for unstable aircraft with diamond and blended-wing-body configurations. These will contribute significantly to Cranfield's extensive research programmes in these areas. The fifth intake has started to design a medium altitude, long endurance (MALE) UAV which will provide a platform for Cranfield's, and other researchers in the fields of remote sensing and payloads for Micro-Satellites. Ref. [4] gives more details of the 1st and 3rd GDPs. These are exciting, but challenging projects which continue to develop the best of design teaching and relevant applied research. Fig. 1 shows how the above 5 GDPs are integrated into Cranfield's strategic aircraft configuration demonstrator programme. It includes a large number of Ph.D. studies, full-time and part-time GDPs and inputs from government-funded programmes.

The design challenge of high altitude long endurance (Hale) unmanned aircraft

AbstractThe requirement for an aircraft to operate in the thin atmosphere at high altitudes for long periods provides a particular challenge to all areas of aeronautical engineering. This is reflected in a range of difficulties encountered when attempting to design aircraft for this type of operation.This paper first considers the reasons for adopting an unmanned solution for high altitude long endurance (Hale) aircraft. It then indicates how the demands of Hale operations lead to problems in applying the design approach taken for more common aircraft types. Some of the work performed at the College of Aeronautics (CoA), in attempting to address the problem areas for the design process and produce initial designs for a range of Hale unmanned aircraft (UMA) types, is then reviewed. The lack of data/methods to allow the prediction of Hale UMA structure mass, engine performance at high altitudes and aerodynamic parameters for low Reynolds number operation and high aspect ratio configurations are identified as particular problems. However, initial design, based on standard approaches, has been shown to be possible, provided caution is exercised.

Systems design for an advanced short take‐off vertical landing combat aircraft ‐ Part 3

Reports on the MSc group design project of students at the College of Aeronautics, Cranfield University. Details the design of the aircraft systems and their reliability and maintainability.

The structural design of an advanced short take‐off vertical landing combat aircraft — part 1

Reports on the MSc group design project of students at the College of Aeronautics, aerospace vehicle design in 1995. The students worked on advanced short take‐off and vertical landing of a combat aircraft. Details the project showing aircraft dimensions and design. Full assessment of the results is pending, but outlines a number of problems faced by the students.

Scaling of incipient separation in high speed laminar flows

College of Aeronautics* Cranfield Institute of Technology, UK This study provides a sound theoretical foundation for a well -established but heretof ore-empirical cri t eri on for incipient separation in moderateiyhypersonic shock/boundary i a yer interactions. It is based on an examination of the leading high Reynolds number approxima tion to trip1 e deck theory combined with its reformulation in terms of the Reference Temperature concept. The analysis further provides extensions giving the effects of both low supersonic Mach numbers and non-adiabatic wail temperatures on incipient separation. 6 = flow deflection angle '&= wall shear stress a = Moo3/&* , viscous mteractlon parameter Subscripts AdrAB= adiabatic wall conditions = body surface e = local inviscid flow conditions at edge of boundary layer i.~. = incipient separation 0 = stagnation value R E F = based on Reference Temperature w = wall surface conditions Su erscript A ( ) = non-dimensional version of ( )

Numerical Computation of Two-Dimensional Unsteady Detonation Waves in High Energy Solids

We are concerned with theoretical modelling of unsteady, two-dimensional detonation waves in high energy solids. A mathematical model and a numerical method to solve the associated hyperbolic system of equations are presented. The model consists of the Euler equations augmented bby extra conservation laws and source terms to accoxint for chemical reaction and tracking of materials. Both the thermodynamics and the chemistry are treated in a simple way. Using a detonation analogue due to Fickett, we test several numerical methods and assess their performance in modelling the essential features of detonation waves. The numerical method selected for the full model is an extension of the conservative, shock capturing technique of Roe, together with an adaptive mesh refinement procedure that allows the resolution of fine features such as reaction zones. Results for some typical tests problems are presented. Starting in 1946 as the College of Aeronautics, the Cranfield Institute of Technology was granted university status in 1969. In 1993 it changed its name to Cranfield University.

Careers:

Cranfield Institute of Technology (CIT), founded as a college of Aeronautics in 1946, will this year celebrate 40 years of growth and innovation. Cranfield was awarded a Royal Charter in 1969, when degree‐awarding powers were granted by the Privy Council. Throughout its history Cranfield has maintained a policy of encouraging close collaboration between its various faculties and industry and it is therefore appropriate that its 40th anniversary falls in Industry Year '86.

A composite crack profile model for CTOD determination—II. An experimental application to a small scale yielding situation

An analytical model namely the “Composite Crack Profile (CCP) model” has been presented earlier for the evaluation of crack tip opening displacement (CTOD) from the measured crack mouth opening displacements (CMODs). The model has been applied in the present work for the small scale yielding situation under the conditions of different specimens and loading geometries (SEN tension, SEN bending, CT). The CTOD evaluated by the model has been compared with the CTOD obtained by the methods prescribed in [A. A. Wells, Symp. Crack Propagation, Paper B4, College of Aeronautics, Cranfield (1961), and T. Hollstein and J. Blanel, Int. J. Fracture 13, 385 (1977).] It is sufficient that whereas the model does not necessitate the use of rotational factor for the evaluation of CTOD, it is more versatile in that it can be used with different loading geometries. The effect of thickness, a/w ratio and the loading geometry on the CTOD at crack initiation (CTOD i) has also been presented and discussed.

Aerodynamic noise — a review of the contributions to jet noise research at the College of Aeronautics, Cranfield 1949-1961 (together with some recent conclusions)

SummaryIt is a pleasure and indeed an honour to be invited to contribute this paper to the 70th Birthday Tribute to Professor A. D. Young, in recognition of his longstanding friendship and as a colleague of the author for many years.It was Professor A. D. Young, at the College of Aeronautics in 1949, who gave the necessary guidance and encouragement to the author in starting research into aerodynamics noise, which was possibly one of the first attempts made in making a quantitative assessment of the noise from a turbulent air jet.The paper discusses the early experimental work and its conclusions, and how it led to attempts to reduce jet noise through the use of vortex generators and the corrugated nozzle. The comparison between theory and experiment is commented on with reference to the early work on acoustic sources and the questions this comparison raised. A final section is included which attempts to close the gap in our understanding of jet noise generation.

A Very Large Cargo Aircraft Design Project

For many years it has been the College of Aeronautics' philosophy that the best way to teach aircraft design is to actually do it. To this end the Aircraft Design MSc students perform an annual group design project based on types of aircraft that are of current interest.

Early Development of an "Acoustic Analogy" Approach to Aeroacoustic Theory

I is a special pleasure to contribute with this brief historical paper to AIAA's celebrations of its 50th anniversary. I am, also, particularly glad that the paper gives me an opportunity to commemorate the energy and vision shown in 1949 by the late H. B. Irving, in his then position as Assistant Director of Scientific Research (Air) within Britain's government machine. Part of his job was to think about the future of aeronautics, with the object of identifying serious problems likely to arise as part of that future; and to draw attention to new research fields that needed to be opened up without delay if timely solutions to those problems were to be found. Remarkable vision was shown by Irving in recognizing so clearly, as early as 1949, that jet engines were bound to cause severe noise problems when (as must ultimately happen) they penetrated the civil transport market. This may have made him the first person in the world to identify research on jet noise and means for its reduction as a major new field of research to which effort urgently needed to be devoted. Great energy, too, was shown by Irving when he followed up that insight by a vigorous campaign waged with the object of setting up substantial research groups in this field within British university institutions. These groups (supported, where necessary, by contributions from the modest funds at Irving's disposal) were invited to pursue basic experimental and theoretical studies of the noise of jets; studies that might be usefully complementary to a large-scale program of empirical studies of jet-engine noise and schemes for its reduction initiated at Rolls Royce Ltd. Irving ensured, too, that the university groups created in this way (especially, the group including G. M. Lilley at the College of Aeronautics in Cranfield, the University of Southampton group that included E. J. Richards and A. Powell, and the University of Manchester group including myself on the theoretical side and J. H. Gerrard on the experimental side) would all take part together in frequent meetings with the outstanding Rolls Royce team under the leadership of F. B. Greatrex. These regular meetings very powerfully influenced the progress of the research work. I remember this in my own case: as the participant mainly concerned with developing theoretical approaches, I was helped by constant contact with several growing bodies of experimental data to adopt the necessary critical and selective approach to my own growing collection of theoretical ideas. The only Satisfactory theories are those that simultaneously accord with empirical data and with scientific logic!—a formidable pair of requirements. I recall Irving coming up to my attic room in the deeply blackened old Owens College building (since revealed by modern stone-cleaning technology as a charming blend of light brown and blue shades!) at Manchester University. In 1949, I was a 25-year-old Senior Lecturer in Applied Mathematics, already copiously involved in compressibleflow theory (especially, high-speed aerodynamics and shockwave dynamics). Somehow, Irving convinced me that jet noise was an exceptionally exciting theoretical challenge. I recognized that a jet was one of the classical turbulent flows, characterized to be sure by a complex pattern of vorticity; but not (according to views then current) by any dilatation. Compressibility had not been regarded hitherto as a significant factor in vortex motions or turbulence; yet it must be playing a part if any radiated sound were to result. Next morning I had to go to London, which in 1949 necessitated a four-hour train journey. Once in the train J could not stop thinking about the j£t-noise conundrum. It is, furthermore, the literal truth that the only piece of paper I had on me was the proverbial back of an envelope'M How fortunate that was. Sitting in the impersonal confines of the railway compartment, after having awakened that morning still more clearly conscious of what an exceptionally exciting theoretical problem in mechanics of fluids had been put to me, I had four hours to think about it while prevented from succumbing to the theoretician's besetting weakness; namely, rushing into filling sheets of paper with endless equations.... The essential idea of the acoustic analogy approach came before my journey's end. Iremember that the first part of the journey was entirely devoted to considering what would be the appropriate dependent variable in a system of equations to describe jet noise. I had found in many problems of compressible flow that the key to producing tractable equations was the correct choice of dependent variable. Often the pressure was an optimum choice (for example, in the aerodynamics of disturbances to a nonuniform oncoming stream). However, I soon decided against use of the pressure,

Some possibilities for composite light aircraft construction

The College of Aeronautics has a considerable interest in composite materials, and in their application in particular to aerospace vehicles, over a number of years, and during this time we have conducted several research programmes on these types of materials.During recent years, an area of research which has attracted our interest is in the application of composite materials to light aircraft, forming part of a more general study of light aircraft which has resulted in our constructing and testing aircraft in this category on two occasions in recent years.Some of the work on these programmes has been conducted by students at Cranfield studying for higher degrees, and I acknowledge my indebtedness to them for some of the results presented in this paper.

Error Synthesis

This paper discusses the drawbacks of observational methods of analysing navigational errors and shows the advantages of a synthesizing technique, whereby the effect of any change in the magnitude and distribution of a component error upon the overall resultant error can be evaluated and examined. To this end a computer program has been developed which is capable of accepting both analytical and numerical statistical distributions, representing errors in the components, and combining them to yield the overall effective error. A new error distribution better representative of many navigational error distributions is introduced. The work described is applicable to the investigation of any error which depends upon the interaction of many component errors and is not restricted to the navigation field. An extension of the method to mixed samples is indicated.The paper describes the final step in the development of a universal computer program aimed at synthesizing navigational errors in order that they can be used in evaluating their effect on any proposed A.T.C. system. The investigation was commenced at the College of Aeronautics in 1963 and has been the subject of several published papers during the interim period.

Second Cranfield International Conference on Information Storage and Retrieval

This report appeared originally in Computer Weekly for 18th September, and is reprinted here, with small alterations, by kind permission of the publishers of Computer Weekly. The papers presented at the conference will be published in forthcoming issues of ‘Information Storage and Retrieval’, but copies of preprints may be obtained at Xerox cost price from Mr. C. W. Cleverdon, Librarian, College of Aeronautics, CRANFIELD, Bedford.

Personalities in the news

Air Commodore F. R. Banks, C. B., O.B.E., C.Eng., C.G.I.A., F.R.Ae.S., Hon. F.A.I.A.A., F.Inst.Pet., M.S.A.E., Commander of the Legion of Honour (France), Commander of the Legion of Merit (U.S.A.), R.A.F. (retd.), has taken office as President of the Royal Aeronautical Society succeeding Prof. D. Keith‐Lucas, M.A., C.Eng., F.R.Ae.S., (Professor of Aircraft Design, College of Aeronautics, Cranfield).

Fluid Logic for Machine Tool Control?: British Experimental Work at the College of Aeronautics

Fluid Logic for Machine Tool Control?: British Experimental Work at the College of Aeronautics