CoA. Reports

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Open Access
Ablation studies of low melting point bodies in a pre-heated supersonic air stream
(College of Aeronautics, 1960-02) Cleaver, J. W.
This report is an investigation into the melting of axi-symmetric and two-dimensional bogies at a Mach No. of M[infinity] = 1.78 and stagnation temperatures up to 550 [degrees]K. In this temperature range, the most suitable material for the models was found to be an eutectic tin-lead alloy a melting point of 456 [degrees]K. For the cone and hemisphere-cone models two distinct modes of melting were observed. In cases where the estimated equilibrium surface temperature (Tw)o was approximately equal to the material melting temperature Tm, melting occurred only at the stagnation point of the model and was such that a flat surface normal to the gas stream always resulted. If the average rate of heat transfer at the air-liquid interface be defined as qi = LmPm x, where Lm is the latent heat of fusion, Pm is the density of the material and x is the rate of recession of the flat surface, it is found that qi decreases with increase of the radius of the flat nose. A very approximate theory is found to show some agreement with the experimental rates of heat transfer. When (Tw)o was considerably greater than Tm the flat surface was no longer preserved and the resulting steady ablating shape was paraboloidal in nature. When this occurred x was usually constant. This allowed some average steady state heat transfer rates to be evaluated and compared with theory. Preliminary tests were also made with a two-dimensional wedge model.
Open Access
Addendum to type record. Avro "Lancaster" Mk.1 P. A. 474 Type record No. 1/P1/Lancaster. Investigation of boundary layer conditions on wings. M.O.S. Contract No.6/Aircraft/9807/C. B. 6(a)
(College of Aeronautics, 1956-01) College of Aeronautics, Department of Aircraft Design
Introduction The investigation involves, briefly, the mounting of a wing of 45' sweep-back in a dorsal position on the fuselage of 'Lancaster' P.A.474 such that wing incidence will be variable in flight over a 20 range, i.e. ± 100. A ‘partial chord’ technique for swept wings has been established by the College using a similar wing mounting configuration on an Avro 'Anson' Aircraft and this technique has been applied to the current investigation.
Open Access
Aerodynamic characteristics of a hypersonic parachute
(College of Aeronautics, 1961-11) Boyd, E. A.
Newtonian theory, both in the form of the Modified-Newtonian and the Newton- Busemann pressure laws, is used to find the shape, cloth area and drag of the axisymmetric canopy of a hypersonic parachute, whose only load-carrying fibres are longitudinal ones. As an example, an estimate is made of the size of canopy needed to give a drag of 20,000 lb. in flight at a Mach number of 10 at 100,000 feet altitude.
Open Access
The aerodynamic derivatives of an aerofoil oscillating in an infinite staggered cascade
(College of Aeronautics, 1960-01) Craven, A. H.
Thin aerofoil theory is used to obtain, in integral form the aerodynamic derivatives of an aerofoil oscillating in an infinite cascade. The theory allows for arbitrary stagger angle and phase difference between adjacent blades of the cascade. The expressions obtained reduce, for zero stagger and for in phase and antiphase oscillations, to known results.
Open Access
The aerodynamic derivatives with respect to sideslip for a delta wing with small dihedral at supersonic speeds
(College of Aeronautics, 1947-12) Robinson, A.; Hunter-Tod, J. H.
Expressions are derived for the sideslip derivatives on the assumptions of the linearised theory of flow for a delta wing with small dihedral flying at supersonic speeds. A discussion is included in the appendix on the relation between two methods that have been evolved for the treatment of aerodynamic force problems of the delta wing lying within its apex Mach cone. Continues…
Open Access
The analysis of reinforced circular and elliptical cutouts under various loading conditions
(College of Aeronautics, 1961-07) Houghton, D. S.; Rothwell, A.
The effect of reinforced cutouts in a plane sheet under various loading conditions is considered, and a number of experimental results are given for circular and elliptical cutouts with a uniform plate reinforcement, subjected to various systems of biaxial tension and pure shear. These experiments were conducted using a plane loading frame, and the results are compared with the theoretical plane stress solution. For the circular cutout the effect of neglecting the bending stiffness of the reinforcement is considered. Some additional experiments were carried oUt on a 60 in. diameter pressurised cylinder containing an elliptical hole reinforced according •to Mansfield's neutral hole theory. The strains in the sheet in the region of the neutral hole are .compared with the corresponding strains in the uncut sheet. The experimental results obtained generally show a good agreement with the theory.
Open Access
An approximate solution of the turbulent boundary layer equations in incompressible and compressible flow
(College of Aeronautics, 1960-07) Lilley, G. M.
If over the ‘outer’ region/ of the boundary layer, where the mean velocity varies but little from its value outside the shear layer, a virtual eddy viscosity is defined, which is constant over the outer region but varies in the direction of the mainstream, a solution of the turbulent boundary layer equations can be found which satisfies the appropriate boundary conditions. The solution leads to a compatibility condition for the virtual eddy viscosity in terms of the wall shear stress, the boundary layer momentum thickness and the mainstream velocity, at least for the case of a constant external velocity. [...cont.]
Open Access
Aviation fuel problems at high altitudes and high aircraft speeds
(College of Aeronautics, 1959-01) Goodger, E. M.
Much useful data has appeared over recent years concerning the problems incurred by continued increases in operational altitudes and aircraft speeds. This report is an attempt to correlate a representative amount of these data, and to present them in a form suitable both for general information and for project design reference. Frequent references are made to the literature as guides to additional information. Some of the work has formed the basis of research activities at Cranfield.
Open Access
Base pressure at supersonic speeds in the presence of a supersonic jet
(College of Aeronautics, 1960-12) Craven, A. H.; Chester, D. H.; Graham, B. H.
The effects on base pressure of jet Mach number, free stream Reynolds number and jet to base diameter ratio have been investigated experimentally. It was found that, for jet stagnation pressures greater than that required for the nozzle to reach its design Mach number, an increase of jet Mach number reduced the base pressure. Similarly the base pressure increased with increase of the ratio of jet diameter to base diameter and, at nigh jet stagnation pressures, base pressures higher than free stream static pressure were found. The base pressurewas independent of frek: stream Reynolds numbers greater than 2 x 10[to the power of 6] per foot but increased with reduction of Reynolds number below 2 x 10[to the power of 6] per foot. Unsteady wave patterns were found when the jet Mach number did not differ markedly from the free stream Mach number and the jet had just reached its design conditions.
Open Access
Boundary layers with suction and injection a review of published work on skin friction
(College of Aeronautics, 1960-09) Craven, A. H.
Available data on the effects of suction and injection on skin friction are summarised and compared. It is shown that injection into a turbulent boundary layer can produce a skin friction coefficient lower than the laminar value at trio same Reynolds number on an impermeable plate.
Open Access
Buckling due to thermal stress of cylindrical shells subjected to axial temperature distributions
(College of Aeronautics, 1961-05) Johns, D. J.; Houghton, D. S.; Webber, J. P. H.
Thermal stress distributions in uniform circular cylindrical shells due to axial temperature distributions are investigated. The discontinuity effect due to the presence of a cooler stiffening bulkhead is considered, and the possibility of thermal buckling of the shell due to the circumferential discontinuity stress is examined. The buckling analysis is based on Donnell's shell equation, and particular attention is given to shells having clamped edges. An experimental investigation of this buckling problem is discussed, and the results obtained are seen to agree reasonably well with theory.
Open Access
Busemann correction to the characteristics of the two-dimensional hypersonic sail
(College of Aeronautics, 1960-11) Boyd, E. A.
The two-dimensional hypersonic sail is examined using the Newton- Busemann pressure law. The results are compared with those of Daskin and Feldman (1958) who used the empirical modified Newtonian pressure law. It is found that for a given chord length of sail a corrected sail will give a specified lift for a smaller tension in the sail. At a flight Mach number of 10 at 100,000 ft. the tension in one particular sail considered could be supported with a working stress of about 20 tons/in[squared].
Open Access
The characteristics of a two-dimensional supersonic sail
(College of Aeronautics, 1960-12) Boyd, E. A.
The two-dimensional supersonic sail is analysed using Busemann's second-order theory. It is found to have a universal shape, which is part of a Sici spiral. Aerodynamic characteristics are calculated for a few sails. The tension in sails flying at Mach numbers of 2 and 3 at altitudes of 20,000 and 70,000 feet is large and suggests that wire sails will be needed for flight under these conditions.
Open Access
The compressible laminar boundary layer with foreign gas injection
(College of Aeronautics, 1962-01) Craven, A. H.
The equations of the steady compressible two-dimensional laminar boundary layer with foreign gas injection through a porous wall are solved, using an extended form of Lighthill's approximate method, for arbitrary main stream pressure gradient, wall temperature and injection velocity. The wall shear stress and heat transfer rate are obtained in the form of equations suitable for iteration. It is shown that substantial reductions in skin friction and heat transfer rate can be obtained by the injection of a light gas instead of air.
Open Access
Dislocations and twinning in graphite
(College of Aeronautics, 1960-04) Kennedy, A. J.
The twin composition plane in graphite is a 20o tilt boundary between lattices which are rotated, relatively, about an axis In the basal plane. Previous work has led to the proposition that some special type of structure must necessarily exist in the neighbourhood of the boundary which violates normal hexagon arrangement of the carbon atoms. It is demonstrated that tilt boundary of the required form can be explained as an array of partial dislocations, such a boundary being possible in either the hexagonal or the rhombohedral form. A boundary of this type is mobile, and can, by its movement, introduce or eliminate stacking faults and thus change the volume rhombohedral graphite present in the normal hexagonal lattice. Such effects have been reported previously. The true twinning plane in this model is not the composition plane, which is the plane {1101} referred to the structural (not the morphological) axes, but the plane {1121}
Open Access
The dynamic loading of spur gear teeth
(College of Aeronautics, 1959-10) Dunmore, J. H.
In this report, description of the first stage of some work on the dynamic loading of gear teeth is given. The work has been performed on a power circulating gear rig, using gears of 9 inch P. C. D., 4 D.P., and 1/2 inch face width. The rig is capable of running at pitch line velocities up to 20,000 ft/min. with imposed leads of up to 3,000 lbs/ inch of face width. Particular reference is made to the instrumentation problems which were encountered, and to the measurement of the shape of the gears and their associated transmission errors. No attempt is made at a theoretical analysis of the results obtained as this will be the subject of a future report, along with the publication of more results.
Open Access
The effect of curvature on the stress concentrations around holes in shells
(College of Aeronautics, 1962-05) Houghton, D. S.; Rothwell, A.
An experimental investigation has been carried out to investigate the effect of curvature on the stress concentrations around holes in shell structures. Two methods have been employed: - (I) Araldite cylinders, containing holes of various shapes, subjected to axial tension, internal pressure and torsion were examined by the photoelastic frozen stress technique. (2) Aluminium alloy curved panels and hemispheres were used in conjunction with miniature electrical strain gauges. The results are compared with the theoretical solutions and suggest that the curvature effect can be significant, particularly for the case of shear or biaxial loading.
Open Access
The effect of density on jet flow at subsonic speeds
(College of Aeronautics, 1959-07) Craven, A. H.
On the assumption that the velocity and density distributions across a jet of one gas issuing into a stream of a second gas are of exponential form, the momentum integral approach has been employed to find the variation of centre-line velocity downstream of the potential core. The results for the particular case of a jet issuing into a gas at rest are equivalent to those found theoretically by Blottner (Ref. 2) and experimentally by Keagy and Weller (Ref. 1). The results for the jet issuing into a moving stream agree with the limited experiments of the present author. These calculations show the importance of jet to free-stream density ratio with respect to the rate of decay of the jet downstream of the mixing region.
Open Access
The elastic stability of sandwich plates
(College of Aeronautics, 1949-03) Hunter-Tod, J. H.
This paper treats the elastic stability of supported rectangular plates of sandwich construction with isotropic and aeolotropic fillings under compression and shear loading. Formulae are developed for critical stresses for flat and curved panels in compression and flat panels in shear for the buckling of the whole panel, also for the wrinkling or local failure of the faces of flat panels in compression. A method is indicated for calculating the critical load of a cylinder in pure bending. It is established that for a wide range of conditions the critical stress for panels buckling in compression is independent of the form of the filling providing it is symmetrical about the normal; of the elastic constants of the filling only the transverse shear is of concern. As a result a simple extension of the equivalent plate theory of greatly improved accuracy is developed enabling the use of equations treating the plate as a whole.
Open Access
An elementary study of gas injection and sublimation into a simple shear layer
(College of Aeronautics, 1960-02) Clarke, J. F.