bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boundary Layers over Infinite Yawed Wings
Authors: Cooke J. C. 
Published: July 2016

SummaryA method of calculating turbulent boundary layers on infinite yawed wings is given, making use of a method of calculating turbulent boundary layers due to Spence and of an analogy between three-dimensional and axi-symmetric boundary layers. It is also shown that the displacement thickness is equal to that computed using chordwise components and that the streamwise momentum thickness is approximately equal to the chordwise momentum thickness. Shock-free flow and small boundary layer cross-flow are assumed.
The Aerodynamic Forces Associated with Harmonic Motion of Slender Wings on Stationary Bodies of Revolution
Authors: Milne R. D. 
Published: July 2016

SummaryThe slender-body theory is applied to the determination of the unsteady aerodynamic forces on slender wing-body combinations when the body is stationary and the wing is deforming harmonically. The uniform body is circular in cross section, the wings are placed symmetrically and the wing deformation mode is necessarily symmetrical about a vertical plane through the body axis. The frequency parameter is restricted to that range for which the “cross-flow” potential equation is Laplace's equation. The case of an allmoving slender control surface on a body is treated in detail and numerical results are given for the forces and moments on body and control surface when the control plan form is triangular: the presence of a gap is neglected.
The Quasi-Cylinder of Specified Thickness and Shell Loading in Supersonic Flow
Authors: Portnoy H. 
Published: July 2016

SummaryThe methods of the operational calculus are used to obtain a linear approximation to the shape of the mean camber surface of a quasi-cylinder in a supersonic flow in terms of its shell thickness and loading distributions. The analysis deals with a generalised quasi-cylinder; that is one which, although lying close to a mean cylinder, need not possess axial symmetry. The quasi-cylinder is also permitted to be within the small disturbance field of other separate components, e.g. a centre-body. Because the linearised theory is inadmissable for internal duct flows close to and beyond the first reflected characteristic cone, the present solution is likewise invalid close to and beyond the position where this characteristic meets the mean cylinder. The work given here enables the camber shapes of “ring-wings”, which have been used theoretically to reduce or even nullify the wave-drag of a central slender-body, to be found. An example illustrates the general method.
The Effect of Fuel Distribution on Reaction Rates
Authors: Herbert M. V. 
Published: July 2016

SummaryTheoretical reaction rate considerations normally require homogeneity of the mixture supply. An attempt—necessarily crude by reason of the analytical difficulties—is made here to cater for the case of non-uniform fuel distribution. Assuming a point-source injector in a parallel pipe, the “loss” in reaction rate is calculated for a limited number of specimen cases.
Compression Tests on Thin-Walled Cylinders
Authors: Holmes M. 
Published: July 2016

SummaryThe paper describes compression tests on eight thin-walled cylinders of 3 ft. diameter and 0·035 in. wall thickness made of aluminium alloy plate. The lengths of the cylinders were either 6 ft. or 9 ft. Three of the cylinders were tested under axial compression up to buckling failure, and the initial buckling load, failing load and mode of buckling were observed. A further three cylinders were similarly tested, but these cylinders were subjected to internal pressure before applying the compressive load. The internal pressure had a twofold strengthening effect on these cylinders. Firstly, it induced a tensile pre-stress along the axis of the cylinder and, secondly, it resulted in the value of the compressive stress at which buckling occurred being greater than the buckling stress value for the unpressurised cylinders. The six cylinders were tested in a manner which allowed the end face of each cylinder to rotate about a diametral axis. A parallel platen device was used in testing the last two cylinders (in an unpressurised condition) which restrained rotation of the end faces of the cylinders. These tests enabled the effect of end restraint to be studied, and also enabled measurements of load-carrying capacity at large axial deflections to be made. The initial buckling loads, failing loads and modes of buckling observed in the tests were compared with existing large deflection theory.
Mass Transfer Cooling in a Boundary Layer
Authors: Hurley D. G. 
Published: July 2016

SummaryPrevious theoretical work on mass transfer cooling is reviewed and it is shown that this may be complemented by similar solutions that occur when the velocity outside a two-dimensional boundary layer varies as some power of the distance from the front stagnation point. The case of stagnation point flow with constant wall temperature is investigated in some detail, under the assumption that the temperature differences are everywhere small compared with the absolute temperature. Calculations on an analogue computer, supplemented by an investigation of the asymptotic behaviour, are used to determine the boundary layer development and heat transfer rates when the coolant is hydrogen, helium, steam or carbon dioxide. It is found that, on a mass flow basis, hydrogen reduces the heat transfer rate most and that steam is the next most effective of the substances investigated.
Lift/Drag Ratios of Optimised Slewed Elliptic Wings at Supersonic Speeds
Authors: Smith J.H.B. 
Published: July 2016

SummaryPrevious work by R. T. Jones on the drag minimisation of elliptic wings is extended to the case of the slewed wing with thickness. These results are used to calculate lift/drag ratios of idealised configurations related to a supersonic transport aircraft. The values of lift/drag ratio and optimum slenderness ratio found are comparable with those calculated earlier in studies of delta-like plan forms.
The Deformational Behaviour of Low Aspect Ratio Multi-Web Wings
Authors: H. Gallagher R. , Rattinger I. 
Published: July 2016

SummaryResults of a study of the accuracy attainable from various approaches to low aspect ratio wing deformational analyses are described. Seven model multi-web wings, representing a restricted range of sweep angles, aspect ratios and other geometric factors, were tested for deflection influence coefficients. Methods of matrix structural analysis and other techniques, involving numerous idealisations, were then applied in the prediction of the test data. This paper presents the experimental data. Subsequent papers will describe the analytical methods, the level of test-theory correspondence, and the merits and shortcomings of the theories studied.
The Static Aeroelastic Deformation of Slender Configurations
Authors: Hancock G. J. 
Published: July 2016

SummaryCalculations have been applied to a series of flexible plates (delta, gothic and ogee) to estimate their static aeroelastic behaviour. Assuming linear aerodynamics, the general tendencies of Part I are particularised. Assuming non-linear aerodynamics, it is shown that in general two positions of equilibrium are apparently possible at each speed. The stability of the models is not considered.
The Correlation of Unstable Crack Length Data for Sheet Materials
Authors: Welbourne E. R. 
Published: July 2016

SummaryA semi-empirical analysis of unstable crack propagation in thin sheets is given. An effective value of the crack tip strain concentration factor is used as the criterion for instability. Good correlation is achieved with experimental results from unreinforced sheets of aluminium and titanium alloys and high-strength steels. The interdependence of geometry and stressstrain curve properties in determining the unstable crack propagation characteristics of sheet materials is illustrated in an appendix.
Shear Buckling of Clamped and Simply-Supported Infinitely Long Plates Reinforced by Transverse Stiffeners and a Central Longitudinal Stiffener
Authors: Rockey K. C. , Cook I. T. 
Published: July 2016

SummaryThe paper presents a solution to the buckling under shear stress of infinitely long plates which are reinforced by both transverse stiffeners and longitudinal stiffeners. Each family of stiffeners is assumed to consist of equally spaced stiffeners. Both simply-supported and clamped edge conditions are examined. Numerical results are obtained for the case of a plate with transverse stiffeners and a central longitudinal stiffener and relationships between the buckling stress and the flexural rigidity parameters of the stiffeners are provided for three different spacings of the transverse stiffeners.
Effects of External Heat Addition on Supersonic Cruise Performance
Authors: Townend L. H. 
Published: July 2016

SummaryHeat addition in the external flow around a supersonic aircraft may produce a field of increased pressure and thereby a propulsive and a lifting force. Less specifically, such effects could be produced by alternative processes involving the gradual expenditure of energy stored in an aircraft, and, according to the process, could be available at hyper-, super-, or subsonic speeds. A generalised study is made of associated effects on cruising range. Results are presented as performance “frameworks,” within which future experimental or analytic data should define regions of feasibility for particular systems.
Stress Concentrations for a Family of Uniformly Reinforced Square Holes with Rounded Corners
Authors: Wittrick W. H. 
Published: July 2016

SummaryThe stress concentration factors for a family of square holes, with varying degrees of curvature at the corners, and with varying amounts of compact uniform reinforcement on the boundary, have been computed for each of four loading cases. Poisson's ratio was assumed to be 1/3.
An Approximate Theoretical Approach for the Determination of Oscillatory Aerodynamic Coefficients for a Helicopter Rotor in Forward Flight
Authors: Molyneux W. G. 
Published: July 2016

SummaryA method is described for the determination of the oscillatory aerodynamic coefficients for a helicopter rotor in forward flight. The method treats the blades and the recirculating wakes on a three-dimensional basis, but certain approximations are made so that the problem is tractable. In particular it is assumed that the downwash effect of a wake sheet beneath the rotor can be represented by concentrating the doublet distribution in the sheet in a single line of doublets.
Fatigue of Unmachined Aluminium Alloy Extrusions
Authors: Gunn K. W. , Woodward A. R. 
Published: July 2016

SummaryThe fatigue properties of unmachined extrusions of high-strength aluminium-copper alloys are known to be lower than those of conventional fully-machined test pieces. Work described in this note has shown that the removal of a layer of metal 0·025 in. thick from the surface of B.S. L65-type extrusions results in an increase in fatigue properties to values approaching those obtained from the conventional laboratory test pieces. Because the removal of material from the surface is not always a practical proposition, other methods of improving strength have been examined and the effect of surface compressive stresses has been shown to be beneficial. Sufficient compressive stress can be induced by surface-rolling to increase the fatigue properties to those of conventional specimens, but this method can only be easily applied to round sections and it is suggested that shot-peening or vapour-blasting could be used for more complicated sections.
Impact Theory Calculations of the Lift and Drag of Ducted Bodies
Authors: Tinkler J. 
Published: July 2016

SummaryNewtonian impact theory has been used to estimate the external pressure forces on ducted bodies of rectangular, circular and semi-circular cross section. With an allowance for skin friction (or other incidence-independent drag) it is shown that maximum lift/drag ratios of about three to four are possible with little effect of body geometry provided that short and very divergent, or tall and narrow rectangular ducts are avoided.Large changes occur in the separate lift and drag at maximum lift/drag ratio and these have to be made compatible with the weight and thrust capacity of the configurations. The maximum lift/drag ratio of a duct can be improved by the addition of wings, especially for a duct with poor lift/drag ratio, but the best overall performance is with a duct of good lift/drag ratio and low drag.It is anticipated that impact theory underestimates the pressure forces, and hence the lift/drag ratios, which would obtain at finite Mach numbers but the trends with geometrical changes should be reasonably reliable.
Estimating Jet Noise
Authors: Coles G. M. 
Published: July 2016

SummaryA large number of far-field jet noise measurements obtained over a considerable period of time are presented, correlated in such a manner that they may be used to provide a complete noise assessment for any jet of which the performance parameters are known. The data are presented in two sections, one dealing with the problem of a static source near ground level, the other dealing with the case of a source in flight.Much of the data was derived from Avon engine tests, but a wide range of other jet noise sources has also been encompassed. Comparisons are drawn which show good correlation to exist between the overall sound pressure levels produced by jets of all sizes. It appears also that even the spectra quoted, which are based only on Avon measurements, are valid over a fairly wide range of jet sizes and are not peculiar to the Avon engine.
An Anomaly in the Theory of Tunnel-Wall Interference on a Lifting Wing
Authors: Garner H. C. , Holder D. R. , Acum W. E. A. 
Published: July 2016

SummaryThere appear in the literature some discrepancies in the various mathematical expressions for the upwash constituting the wall interference on a small lifting wing placed symmetrically in a rectangular tunnel with closed side-walls and open floor and roof. The representation of the interference field as that of a doubly infinite array of image doublets is shown to lead to divergence. An independent calculation by relaxation confirms the correctness of an analytical solution by expansion in Fourier series. The discrepancies are found to arise from incomplete flow conditions at the open boundaries, and it is shown in this paper how the various theories are reconciled.
A Simple Model Representing Internal Damping in Solid Materials
Authors: Neubert H. K. P. 
Published: July 2016

SummaryBased on earlier theories of mechanical, electrical and magnetic relaxation phenomena, the paper discusses a simple mathematical model representing qualitatively the basic characteristics of “internal” damping in solid materials. The model is assessed with respect to variation with frequency of stiffness and loss factor at simple harmonic oscillations, and is applied to oscillatory systems with discrete parameters and to continua.
Stress Concentrations for Uniformly Reinforced Equilateral Triangular Holes with Rounded Corners
Authors: Wittrick W. H. 
Published: July 2016

SummaryThe stress concentration factors for equilateral triangular holes, with varying degrees of curvature at the corners, and with varying amounts of compact reinforcement on the boundary, have been computed for each of three loading cases. Poisson's ratio was assumed to be 1/3.
The Turbulent Jet from a Series of Holes in Line
Authors: Knystautas R. 
Published: July 2016

SummaryThe possibility of obtaining two-dimensional turbulent jet flow from a series of closely-spaced uniform holes in line has been investigated both theoretically and experimentally. The case studied was that of a jet discharging into still fluid of similar density at incompressible speeds. Such a quasi-two-dimensional jet is a particular example of a multiple-interfering jet group.
The Effects of Introducing a Restoring Moment Proportional to Stick Velocity on the Hovering of an Unstabilised Jet-Lift Aircraft
Authors: Holden K. J. 
Published: July 2016

SummaryThis paper covers an investigation into a new way of assisting the pilot to hover an unstabilised jet-lift aircraft. In a normal control system the aircraft is controlled by a moment which varies linearly with stick position. In this paper control systems were considered in which the controlling moment was a linear function of the position and rate of change of position of the stick. The investigation was primarily limited to optimising such a system with freedom restricted to rolling motion and the associated lateral displacement. Effects of limited control power and engine failure were considered. With the optimum control the mean errors in position recorded when hovering were under half those achieved with a normal manual control and the results were almost as good as for an ideal rate-stabilised aircraft. Extending the investigation to both pitch and roll planes led to an even greater improvement, even when the effects of gyroscopic coupling between the two planes were taken into account. The precise engineering of a “mixed” control system of the type discussed needs much thought and it will require considerable development, but the results achieved indicate that it may prove an attractive alternative to an autostabiliser
Stress Distribution in Rotating Discs with Non-Central Holes
Authors: Green W. A. , Hooper G. T. J. , Hetherington R. 
Published: July 2016

SummaryThe stress distribution in rotating circular discs containing a central hole and a symmetrical array of non-central holes is determined by numerical solution of the equations of generalised plane stress. Particular attention is given to an annulus containing the holes and of width approximately eight hole diameters, in which the full two-dimensional equations are solved. The region outside this annulus is treated as radially symmetric and the stresses there are determined from a simpler one-dimensional model. Stress distributions are reported for uniform discs of fixed geometry containing 10, 20 and 45 holes. Results are also obtained for 20-hole discs of non-uniform thickness comprising a uniformly tapered disc, a disc with a thickened annulus containing the holes, and a uniform disc with each hole surrounded by thickened bosses. As a check on the numerical method, calculations have been carried out on a disc of identical geometry to one examined photoelastically bv Leist and Weber with good agreement. The effect of changing Poisson's ratio for this particular disc is also examined.
Electrical Analogue Solutions for the Deformation of Skew Plates
Authors: Rushton K. R. 
Published: July 2016

SummaryA study has been made of the deformation of skew slabs using a pure resistance electrical analogue with a square mesh. The three commonly occurring boundary conditions of simply-supported, clamped, or free edges have been represented on the analogue, and the results of typical problems with these edge conditions are given.
Influence of the Torsional Rigidity of Transverse Stiffeners upon the Shear Buckling of Stiffened Plates
Authors: Rockey K. C. , Cook I. T. 
Published: July 2016

SummaryThe paper provides relationships between the buckling resistance of simply-supported transversely stiffened plates and the flexural rigidity of the stiffeners for various values of the ratio of torsional rigidity to nexural rigidity. Results are presented for four different stiffener spacings.
Stresses Round Pins in Holes
Authors: Cox H. L. , Brown A. F. C. 
Published: July 2016

SummaryThe existing data relating to stresses round pins in holes are reviewed and co-ordinated.The first part of the paper deals with pins of which the diameter is less than half the plate width and which are no better than a push fit in the hole; the second section deals with larger pins; and the third section deals with interference fit of the smaller pins. The theoretical background is sketched in two appendices, and the results of three series of photoelastic measurements of the effects of clearance of the pin in the hole are described.
The Effects of Small Changes of Prandtl Number and the Viscosity-Temperature Index on Skin Friction
Authors: Young A. D. 
Published: July 2016

SummaryThe analytic simplifications in boundary-layer analysis that result from the assumptions that the Prandtl number σ and the viscosity-temperature index ω are unity make it desirable to be able to assess the effects of the departures of the actual values of these parameters from unity. In this paper only the effects on skin friction are considered. Formulae of acceptable validity and wide application are first used to produce generalised curves for these effects for given main-stream Mach numbers and wall temperature conditions for the case of zero external pressure gradient for both laminar and turbulent boundary layers (Figs. 1 and 2).A number of calculated results for the laminar boundary layer with favourable and adverse pressure gradients is then analysed (Figs. 3, 4 and 5) and it is shown that these results are consistent with the assumption that, for a given wall temperature, the effects of small changes of σ and ω on skin friction are independent of the external gradient, so that the appropriate curves of Figs. 1 and 2 apply. Where the change of a- is associated with a change of wall temperature (e.g. if the heat transfer is specified as zero) then the interaction between pressure gradient and this temperature change can be significant in its effects on skin friction for the laminar boundary layer and can only be assessed if the effects of changes of wall temperature with constant σ and ω have been separately determined for the pressure distribution considered. It is inferred that in all cases, except with large adverse pressure gradients and imminent separation, the effects of changes of ω and σ for the turbulent boundary layer are reliably predicted by the zero pressure gradient curves of Figs. 1 and 2 and the effect of any associated change of wall temperature can then be reliably inferred from the zero pressure gradient formula (equation (15)) in the absence of more specific calculations covering a range of wall temperatures.
Shock-Induced Separation of a Laminar Boundary Layer in Supersonic Flow Past a Convex Corner
Authors: Curle N. 
Published: July 2016

SummaryThis paper presents a theoretical investigation of the interactions which occur when a laminar boundary layer on a flat surface encounters an expansive corner followed by a shock or other compressive agency. The method consists basically of two equations; the first relates deflections in the external streamlines to pressure changes and the second relates pressure changes to thickening or thinning of the boundary layer. For simplicity it is assumed that the pressure changes and streamline deflections are small.A comparison is made with the only available experimental results, under conditions which are far outside the range of applicability of the theory. In these circumstances the agreement between the predicted and experimental pressure distributions is reasonable.
An Analysis of the Turbulent Base Pressure Problem in Supersonic Axisymmetric Flow
Authors: McDonald H. 
Published: July 2016

SummaryThe problem of predicting the turbulent supersonic base pressure in axisymmetric flow is treated by an extension of a method of solution to the two-dimensional problem given in Ref. 1. The solution consists principally in tracing the boundary-layer development from upstream of the base to downstream of the recompression region for a given base pressure. A unique solution is obtained by specifying the shape of the rehabilitated boundary-layer velocity profile.A comparison with experiment in the case of the step-down cylinder problem (the sting-support problem) yields some very favourable results. It is pointed out that, while it has not been found possible to obtain a solution to the problem of a vanishingly small sting, the base pressure does not vary appreciably while the sting is decreased from about 0-3 of the base diameter down to zero. It would appear that the present analysis is capable of giving accurate results down to sting/diameter ratios of the order of 0·3.