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Volume 71 - Issue 684 - December 1967

Contents

Page 1 of 2

Other

Research Article

  • Some Problems of Planetary Atmosphere Entry

  • H. Julian Allen
  • Published online by Cambridge University Press:
    04 July 2016, pp. 813-820

  • Progress in understanding the atmosphere heating problems of space vehicles at hyperbolic entry speeds is reviewed. The various sources of aerodynamic heating are discussed along with the response of suitable heat shield materials to these inputs. It is shown that even for optimum shaped vehicles the problems are formidable at entry speeds greatly in excess of Earth parabolic speed. Much additional research, particularly of ablation materials, will be needed to effect satisfactory designs for such craft.

  • Part 2. Project Management in an Aerospace Firm

  • J. G. Keenan
  • Published online by Cambridge University Press:
    04 July 2016, pp. 824-826

  • The success of a project is not measured simply by the arrival in service of a product giving its promised performance. Success means the arrival in service of a product giving its promised performance, purchased at the promised price and delivered on the promised date.

    To achieve these targets with a complex aerospace product requires the effective management of a large number of people, ranging from scientists through designers, technicians, managers, accountants, typists, fitters and coppersmiths to delivery truck drivers. Their efforts must be directed, each in his proper place and time, towards a single goal. The success of the project can be influenced considerably by the type of organisation adopted for the management of this wide variety of people.

  • Autogyro Developments in North America

  • G. J. Hunt
  • Published online by Cambridge University Press:
    04 July 2016, pp. 827-836

  • It is my pleasure and privilege to deliver this lecture about the state of development of the autogyro in North America. I would like to deal with some of the early history of the autogyro, the progress of which had been steadily increasing up to the start of the Second World War. The introduction of the helicopter and the prospect of cheap transportation for all, tended to bring a temporary halt to autogyro construction. The last of the Cierva line of Autogiros was the C.40 which was a two-seater capable of a jump take-off by spinning up the rotor in zero pitch above the normal rpm required for flight, and using the excess kinetic energy stored in the rotor to achieve a satisfactory jump. Cierva's first autogyro experiments were conducted during 1922 using blades attached rigidly to the hub; the single rotor machines rolled over on take-off due to lift dissymmetry on the disc. Cierva also experimented with a contra-rotating rotor but this system was.unsuccessful, since the two discs did not behave in an identical manner.

  • Some Technical and Management Considerations in European Space Programmes

  • G. K. C. Pardoe
  • Published online by Cambridge University Press:
    04 July 2016, pp. 837-851

  • In 1957 the successful launching of the first artificial earth satellite had little immediate effect on the technical activities of the Aerospace Industry of the European countries. It was some years before various countries in Europe either singly or collectively allocated significant funds from their national budgets to allow any real research and development work to begin. In Britain, for example, it was only with the cancellation of Blue Streak in 1960 that the question of determining some sort of national policy in space activity was really brought into focus.

Other

Technical Notes

  • Strain Rate Changes During The Tensile Test

  • R. K. Penny
  • Published online by Cambridge University Press:
    04 July 2016, pp. 853-854

  • Rates of straining that are met in various engineering parts vary considerably from the very small values appropriate to creep to those amounts many orders of magnitude higher that are necessary during metal working processes. If laboratory testing is to follow the ideas of Taira on creep or McLellan on the effects of strain rate on the Ramberg-Osgood constituitive relationships it is necessary to enquire whether conventional testing procedures are adequate. Bodner and Rosen have shown that the phenomenon of discontinuing yielding is solely a function of a testing procedure which allows strain rate changes because of the interaction of specimen stiffness changes and the machine stiffness.

  • Three-Dimensional Free Jets

  • N. Rajaratnam, K. Subramanya
  • Published online by Cambridge University Press:
    04 July 2016, pp. 858-859

  • Fairly elegant semi-empirical theories are available for predicting the turbulent diffusion of axisymmetric and plane jets. However, there are relatively few investigations on the non-axisymmetric jets, herein denoted as three-dimensional jets. The extensive investigations conducted at the Polytechnic Institute of Brooklyn on three-dimensional jets have shown that the flow field is characterised by three distinct regions; the potential core, the characteristic decay (CD) region and the axisymmetric decay (AD) region. In the CD region the velocity profiles in the direction of the minor axis are similar but the maximum velocity decay curves are different for different shapes. In the AD region the flow characteristics are similar to that of an axisymmetric jet. Yevdjevich has recently conducted another investigation on rectangular jets.

  • On the Use of the Preston Tube in Concentric Annuli

  • H. G. Lyall
  • Published online by Cambridge University Press:
    04 July 2016, p. 865

  • In his technical note in the January 1967 JOURNAL, Quarmby (pp 47-49) concludes that because he was able to predict the axial pressure gradient in a concentric smooth annulus by using Preston tubes to measure the inner and outer wall shear stress, then the Preston tubes are giving correct values for the wall shear stresses. I cannot agree that this is a valid conclusion to draw. A Preston tube can only give wall shear stress correctly if the dimensionless velocity in the wall region is the same as that for which the tube was calibrated.

  • On the Use of the Preston Tube in Concentric Annuli

  • Alan Quarmby
  • Published online by Cambridge University Press:
    04 July 2016, pp. 865-866

  • Mr. Lyall's remarks may be answered from the evidence already present in refs 1 and 2 if these are considered objectively. They establish that the ratio of the shear stresses as given by Preston tubes is correct. Evidence on this point is given by the value obtained for rmt from the Preston tube measurement of shear stress ratio and its agreement with the correlation of rmt as a function of radius ratio given by Leung, Kays and Reynolds.

  • Note on Transition to Turbulence in Vortex-Street Wakes

  • M. M. Zdravkovich
  • Published online by Cambridge University Press:
    04 July 2016, pp. 866-867

  • In their pioneering paper published in 1917 Nayler and Frazer showed that the process of vortex formation behind a circular cylinder can have significant three-dimensional features even when care is taken to create two-dimensional flow. Hama produced photographs which show initially straight vortex filaments becoming curved some distance behind the cylinder, with consequent three-dimensional flow. In their experiments on boundary layers Hama et al found the formation and development of “vortex loops” from such curved vortex filaments to be an essential feature preceding transition from laminar to turbulent flow, and they stated that the same would be true for transition in wakes and jets.

Reviews

The Library

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