1 

Laminar separation in supersonic flow woth emphasis on threedimensional pertubations at reattachment
It was shown that regular and repeatable spanwise flow perturbations existed in the reattachment region of a laminar supersonic boundarylayer on a twodimensional backwardfacing step model. It was found that the model span and leadingedge thickness, when below 0.1 mm, had no effect on the wave length of the flow perturbations. On backward facingsteps, at a Mach number of 2.16, the ratio of wavelength of the flow perturbations to boundary layer thickness was a function of the ratio of stepheight to boundarylayer thickness. Similar perturbations were found at the reattachment region of a laminar boundarylayer on forwardfacing steps, on compressioncorners, on rectangular cavities and in the case of interaction between a shockwave and the .boundarylayer. They were also detected in unseparated boundarylayer. The presence of threedimensional perturbations seems to be related to the general question of boundarylayer stability.

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2 

A note on the total drag of jet flapped wings

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3 

Bulletin and annual progress report 1960

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4 

An experimental investigation of the headon collision of spherical shock waves

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5 

The telescopic strut as a beamcolumn
A cantilever strut such as used in shock absorbers for aircraft landing gear is analysed taking into account the effect of lateral deflections. The concept of overlapping stiffnesses is applied to the
cylinderpiston combination. As an alternative to the method of successive approximation explicit formulae are deriveCl for a number of simple configurations and loads. A diagram is devised in which the effects of strut andsupport flexibility on the buckling load are combined. A numerical example shows the usefulness of the latter load in determining the bending moments.

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6 

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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7 

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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8 

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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9 

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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10 

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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11 

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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12 

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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13 

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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14 

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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15 

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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16 

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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17 

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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18 

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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19 

The optimization of an autopilot for an airplane subjected to random atmospheric turbulence

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20 

A review of the jet flap

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