1 

Studies of ground effect on an inwardly inclined annular jet. Part 1. Apparatus and method of testing; effects of aspect ratio and pressure ratio
A systematic but not exhaustive series of tests was carried out with a 60° inwardly inclined annular nozzle over a wide range of nozzle aspect ratios, pressure ratios (up to 3.0), with and without the presence of simulated ground. Total thrust force was measured and converted to augmentation ratio, using the ideal thrust of an equivalent circular nozzle in freeair as a basis. Nozzle angle of attack
was held at zero degrees. Base pressure distributions and nozzle mass flows were also measured but will be included in Part II to be published later.
Agreement between test results and available theory is only moderate. A very sudden jet focussing phenomenon was observed at high nozzle aspect ratios (AR > 250) as weIl as a very pronounced
hysteresis effect in the focussingunfocussing region.

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2 

Headon interaction of oblique shock waves
When two oblique shock waves that face in opposite directions intersect in a uniform supersonic flow, they give rise in the case of a regular interaction, to a pair of receding shock waves,which are
separated by a contact surlace or slipstream. Such shock interactions have been investigated analytically and experimentally . Exact solutions of the regular flow field, for a perfect, inviscid gas, based on the RankineHugoniot equations, have been computer on an 1. B. M . 650 Digital Computer, in the Mach number range of 1. 0 to 5.5. It was found that the exact theory was weU substantiated by the experimental results, which were obtained in the UTIA 16 in. x 16 in. Supersonic Wind Tunnel.

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3 

Design and calibration of an air ejector to operate against various back pressures
As part of a wind tunnel investigation of GETOL aerodynamics, an air ejector was designed and built to act as a "stepdown transformer" between a high pressure air supply and the modeis. It cons.isted of a
central primary jet discharging into a constant area mixing tube. The thrust and mass augmentation of this ejector were determined for various mixing tube back pressures. These experiments were carried out for a convergent primary nozzle and a supersonic one and for two diameters of the mixing tube with the latter nozzle. The effect of the primary mass flow on the mass and thrust augmentation was obtained for a sonic primary.
A comparison between the experimental results and those predicted by a theory developed in this paper was made. The agreement between theory and experiment was generally within ten percent except when the mixed velocity profile was very nonuniform.

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4 

Nonlinear effects in the longitudinal dynamics of a lifting vehicle in a circular orbit
The second order terms were added to the linear equations of motion for a lifting vehicle in a circular orbit with small perturbations. The gravitygradient effect on pitching moment was also included. The
equations were solved, on an analogue computer, for the vehicle of Ref. 1. Transient solutions were obtained following initial conditions on one or more of 0<, 9, and Û . The effect of gravity gradient becomes more important than the aerodynamic moment at high altitude and governs the pitching mode . The second order effects for the perturbations considered were found to be unimportant. It is concluded that the linear theory is applicable even for q > qo so long as the nondimensional perturbation quantities are of reasonable order, say 0.2.

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5 

Experimental investigation of stability and post buckling behaviour of stiffened curved plates
A series of nineteen flat and curved plates having stiffeners of rectangular crosssection have been tested in compression. Measurements made of initial buckling stress and effective widths subsequent to
buckling were consistent with previous work. The ultim ate strength of the plates was found, to increase markedly with curvature, the rate of increase depending on the ratio of stringer spacing to plate thickness.

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6 

Design of the recoil system for the 4" x 7" hypersonic shock tube
The 4" X 7" hypersonic shock tube incorporates two recoil sections which allow the driver and dump tank to move independently of the channel and test section. In conjunction with these recoil sections a
damping system, consisting of liquid springs, has been designed to absorb the recoil energy and to limit the recoil distance.
The design problem consisted of: (1) the calculation of the pressuretime histories acting on the driver endplate and the rear wall of the dump tank, (2) the design of the damping system for each end based on the above histories, (3) the design of the footings and connecting struts to anchor the channel and test section to the floor.
The calculations of the pressure time histories have been completed in som e detail in this work using a perfect, inviscid gas analysis. The design of the liquid springs was carried out by Dowty Equipment of
Canada Ltd. , but a description of the springs along with their performance characteristics is presented for completeness. For the same reason, passing mention is made of the design of the footings and struts, but no details are included.

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7 

Some methods of generating cylindrical explosions
Methods have been developed for gene rating cylindrical explosions by bursting pressurized glass cylinders. The cylindrical "diaphragms" (2 in. or 4 in. dia.) are initially pressurized with air or
with a combustible gas mixture . The cylindrical blast is produced by breaking the diaphragm with a mechanical breaker or igniting the mixture with an exploding wire and letting the cylinder break due to overpressure .
The properties of the flow are recorded photographically. The records include schlieren wavespeed traces of the timedistance plane as weU as multispark schlieren photographs of the physical plane
which can be taken at the equivalent framing rate of up to 250, 000 pictures per second.
Measurements are made of the rate of decay of the cylindrical shock velocity with time . Comparison with an existing approximate theory by ChisneU shows good agreement except for shock speeds near
the origin of the blast.
The combustion technique developed in the course of cylindrical blasts was also successfuUy extended to the production of spherical explosions

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8 

A preliminary investigation of the use of expanders to generate hypersonic flow in a wind tunnel
A preliminary investigation of secondary nozzles was carried out using the UTIA 5" x 7" supersonic wind tunnel. These secondary nozzles, called expanders, are mounted on the main tunnel nozzle and
serve to accelerate a supersonic flow to higher Mach numbers with attached boundary layers . In the present tests the speed of the wind tunnel, in which the flow with atmospheric inlet was normally separated for pitot Mach number MH 4.0, was increased to MH = 5. 15, with attached and relatively thin boundary layers . The presence of the expanders reduced the effective working aection area to 3" x 5" but a relatively small modification to the tunnel could yield a working section of useful size (5" x 5").

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9 

Measurement of twopoint correlations of velocity near a circular cylinder shedding a karman vortex street
Results of an experimental investigation of twopoint correlations of velocity near a circular cylinder shedding a Karman vortex street are presented. The measurements were made along a line parallel to the generator of the cylinder which is at 900 from the upstream direction. The cylinder was mounted transversely in an airstream, and two hotwire probes were used as anemometers .
The curves of correlation coefficient versus probe separation approach zero as the separation between the probes is increased to large values.
A plot of correlation length versus Reynolds number, based in part on a conservative extrapolation, is also presented and compared with correlation length data from pressure measurements taken from reference 3.

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10 

A simple method for the analogue computation of the meansquare response of airplanes to atmospheric turbulence
The mean square response of an airplane to random atmospheric turbulence is, with certain restrictions. given approximately by the integral of the square of the response to the transient input function A.e&,t. The values of A and √ are fixed by the intensity of the turbulence and the ratio of airplane size to turbulence scale. This result is ideally suited to the calculation of meansquare response on analogue computers.

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11 

Design study of the UTIA low density plasma tunnel
A design study of a low density plasma tunnel has been completed. A combination of an electricarepowered souree of high energy plasma, and a cryogenic pumping system, has been chosen to provide
high energy flows at low pressure. The work reported covers a preliminary investigation of the arc source operating characteristics, some limit estimates of the expansion process. an experimental investigation of a "pilot plant" cryogenic pump, and the design of the overall tunnel and pumping system based on these results. It is concluded that a versatile facility can be built, which will be able to produce the following test section characteristieshypersonic flow, statie pressures less than 10 microns
at 5 lb/hr mass flow, mean free paths of the order of l"", stagnation temperatures up to 10, 000ºK, and low levels of stream fluctuation and contamination.

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12 

Note on the design of redundant structures
This note is concerned with the redesign of redundant structures having undesirable stress distributions. A matrix equation is derived relating specified stresses in certain structural members to
changes in the stiffness distribution necessary to achieve these stresses.
The equation is nonlinear, in general, but can usually be solved quickly by iteration. The method of Argyris and Kelsey (Ref. 3) is used in the analysis.

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13 

Systematic axial load fatigue tests using unnotched aluminium alloy 2024T4 extruded bar systems
This note presents the results of a series ofaxialload fatigue tests performed on Aluminum AHoy 2024T4 extruded bar, using a mean tensile stress of 16 ksi throughout. The basic singlelevel SN relation was established using nine specimens at each of fifteen alternating stress amplitudes . The statistical behavior of the singlelevel fatigue endurances at the 'knee.' of the SN curve was discovered to be consistent with the rise and decay respectively of two endurance distributions, apparently representing the action of two different fatigue mechanisms.
The logendurance population during transition was found to become bimodal in nature, with the first distribution a continuation of the log normal distributions at stress amplitudes above this region.
An extensive twolevel test program was carried out using a procedure formulated by the author from previous exploratory work.
In this procedure, the second (runout) stress level is standardized at Sa2 = 34 ksi, and the endurance at this level is used as an indication of the damage at the first level. Systematic variation of the prestress amplitude, and of the fatigue cycles for the first level, provided for the most part a continuous pattern of damage activity throughout the range of these two parameters available under the singlelevel SN curve. By this procedure, areas of severe damage accumulation were delineated, as were areas of socaHed 'healing' which occur at certain high stress levels (0 . 1% Proof Stress), and at high numbers of cycles at low stress levels. An analytical relation was found to fit the observed damage behavior at high stress levels (over o. 1% Proof Stress).
The data at low stress levels are inadequate to derive a similar continuous analytical relation in this area.

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14 

Temperature Effects on Material Characteristics
Some of the physical properties of the main elements of interest in high temperature technology are reviewed. Some general trends emerge when these properties are viewed as a function of melting point, but there are a few notable exceptions. Titanium, zirconium, niobium and tantalum all have disappointingly low moduli; chromium is excellent in many ways, but has a limited ductility at lower temperatures; molybdenum oxidises catastrophically above about 700 C, and niobium suffers from severe oxygen embrittlement. Beryllium and carbon (in the graphitic form) both stand out as exceptional materials, both have very low densities, beryllium a very high modulus but an unfortunately low ductility, while graphite has a relatively low strength at the lower temperatures, although at temperatures of 2000 C and above it emerges as a quite exceptional (and probably as the ultimate) high temperature material. Some of the fundamental factors involved in high temperature material development are examined, in the light, particularly, of past progress with the nickel alloys. If a similar progress can be achieved with other base elements then a considerable margin still remains to be exploited. Protection from oxidation at high temperatures is evidently a factor of major concern, not only with metals, but with graphite also. Successful coatings are therefore of high importance , and the questions they raise, such as bonding, differential thermal expansion, and so on, represent aspects of an even wider class covered by the term "composite structures". Such structures appear to offer the only serious solution to many high temperature requirements, and their design, construction and utilization has created a whole series of new exercises in materials assessment. Matters have become so complex, that a very radical and fundamental reassessment is required if we are to change, in any very significant way, the wasteful and ad hoc methods which characterise so much of presentday materials engineering.
The College of Aeronautics was founded in 1946 and was granted university status in 1969 becoming the Cranfield Institute of Technology. In 1993 it changed its name to Cranfield University.

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15 

Boundary Layers with Suction and Injection: A review of published work on skin friction
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 the same Reynolds number on an impermeable plate.
The College of Aeronautics was founded in 1946 and was granted university status in 1969 becoming the Cranfield Institute of Technology. In 1993 it changed its name to Cranfield University.

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16 

Research at the College of Aeronautics Cranfield
The College of Aeronautics was founded in 1946 and was granted university status in 1969 becoming the Cranfield Institute of Technology. In 1993 it changed its name to Cranfield University.

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17 

Materials for Astronautic Vehicles
The College of Aeronautics was founded in 1946 and was granted university status in 1969 becoming the Cranfield Institute of Technology. In 1993 it changed its name to Cranfield University.

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18 

The Busemann correction to the characteristics of the twodimensional hypersonic sail
The twodimensional hypersonic sail is examined using the NewtonBusemann 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/in².
The College of Aeronautics was founded in 1946 and was granted university status in 1969 becoming the Cranfield Institute of Technology. In 1993 it changed its name to Cranfield University.

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19 

The free uncoupled vibrations of a uniformly rotating beam
The review derives and presents the equations which govern the free uncoupled flexural and torsional vibrations of an untwisted beam rotating at uniform speed. Consideration is given to the effects of an elastic hinge at the root and of a concentrated mass at the tip. The variation due to these effects of the first three natural frequencies of the root bending moments, torques and shear forces is given in the form of graphs .

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20 

Recent trends in the mechanics of highly rarefied gases
A review of some recent investigations in the flow of h i ghly rarefied gases is presented. The basic nature of the transport process in free molec ule flow is deduced from the Boltzmann equation
for the molecular velocity distribution function. The present semiempirical state of our knowledge of the reflection of molecules from the surface of a solid is summarized and some directions for research are indicate d. The aerodynamic properties of bodies in highly rarefied flows is considered with emphasis on the long cylinder as a case of special interest. The theory is extrapolated to the limit of very h igh speed ratios or Mach numbers and the results are compared with those de duced from
the Newtonian flow theory. The application of recent studies of rarefied gas flows to the development of instruments for the measurement of the pressure, temperature and density of such flows is reviewed in some detail. The use of free molecule probes for the study of boundary layers
and shock waves is outline d. The review is brought to a close with a very brief consideration of some factors involved in the collisionfree flow of a plasma.

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