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  • 1
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    Solution of the wedge entry problem by numerical conformal mapping (1972)
    Cambridge University Press
    Details
    Publication Date: 1972-11-14
    Description: An accurate quasi-analytic method of solution is presented for the classical hydrodynamics problem of the constant-velocity entry of a prismatic wedge into a weightless incompressible inviscid fluid. The method uses the Wagner function W, which reduces the problem to the determination of a mapping function λ = ℒ(W) for the hodograph. ℒ(W) is constructed by using the hodograph for an unsymmetric diamond together with a modifying or ‘preparatory’ trans-formation. A computer method of conformal mapping is developed and is used to obtain this latter transformation. Results are presented for the case of a 90° wedge and show that the solution is both more accurate than previous solutions, having an error of less than 1 %, and more complete, as it portrays the entire flow field and furnishes information about the functional dependence among the variables. © 1972, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 2
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    An experimental and theoretical study of internal waves generated by the collapse of a two-dimensional mixed region in a density gradient (1972)
    Cambridge University Press
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    Publication Date: 1972-01-11
    Description: Previously reported experiments with a self-propelled body submerged in a fluid with a stable vertical density gradient have demonstrated that the turbulently mixed wake first expands more or less uniformly and then collapses vertically while continuing to expand horizontally (Schooley & Stewart 1963). It was also shown that the vertical collapse of the wake generates internal waves. Essentially two-dimensional experiments have also been used to explore some of the build-up and decay characteristics of vertical wake collapse induced by a sub-merged burst of turbulent mixing (Wu 1969; Schooley 1968). The present paper reports new experimental measurements and a linear theoretical analysis of the internal wave field created in stratified water by a burst of submerged turbulent mixing. The forcing function has been obtained in integral form for an initial-value model of wake collapse in terms of a general Brunt-Väisälä frequency profile, using normal mode theory. Numerical results have been determined for the specialized case of a completely mixed circular wake in a constant Brunt-Väisälä profile. These results are compared to the experimental measurements. © 1972, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 3
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    On the interaction of surface and internal waves (1972)
    Cambridge University Press
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    Publication Date: 1972-03-14
    Description: The steady-state interaction between surface waves and long internal waves is investigated theoretically using the radiation stress concepts derived by Longuet-Higgins & Stewart (1964) (or Phillips 1966). It is shown that, over internal wave crests, those surface waves for which cg0cosϕ0 〉 ci experience a change in direction of propagation towards the line of propagation of the internal waves and their amplitudes are increased. Here cg0 is the surface-wave group speed at U = 0, Φ0 is the angle between the propagation direction of the surface waves at U = 0 and the propagation direction of the internal waves, and ci is the phase speed of the internal waves. If c g0cos Φ0 〈 ci the direction of the surface waves is turned away and their amplitudes are decreased. Over troughs the opposite effects occur. At positions where the local velocity of surface-wave energy transmission measured relative to the internal wave phase velocity is zero, i.e. cg + U - ci = 0, there is a singularity in the energy of the surface waves with resulting infinite amplitudes. It is shown that at these critical positions two wavenumbers which were real and distinct on one side coalesce and become complex on the other. The critical positions are thus shown to be barriers to the propagation of those wave-numbers. It is also shown that there is a critical position representing the coalescence of three wavenumbers. Surface-wave crest configurations are shown for three numerical examples. The frequency and direction of propagation of surface waves that exhibit critical positions somewhere in an internal wave field are shown as a function of the maximum horizontal surface current. This is compared with measurements of wind waves that have been reported elsewhere. © 1972, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 4
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    The stability of unsteady axisymmetric incompressible pipe flow close to a piston. Part 2. Experimental investigation and comparison with computation (1971)
    Cambridge University Press
    Details
    Publication Date: 1971-12-29
    Description: Flow visualization has been used quantitatively to determine the flow relative to a piston and a free surface started from rest. The discharge of water from a cylindrical reservoir was investigated. Flow with a free surface started from rest was found to have a critical Reynolds number (based on tube diameter and surface speed) of about 450 above which a ring vortex was produced just below the surface. Measurements at Reynolds numbers of 525 and 1200 were compared with computations made by the methods described in Part 1. The computed drift of tracer particles agreed well with observed values. The largest discrepancies occurred in the radial component of the drift in the early stages of the motion and amounted to 2½% of the tube diameter. © 1971, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 5
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    The flow due to an oscillating piston in a cylindrical tube: a comparison between experiment and a simple entrance flow theory (1971)
    Cambridge University Press
    Details
    Publication Date: 1971-11-15
    Description: The velocity on the axis of a circular tube was measured over a range of distances from a piston reciprocating in simple harmonic motion. These velocities become independent of axial distance sufficiently far from the piston. The method of calculating the developing flow is based on a comparison with steady laminar flow which, in the entry region of a circular tube, approaches the fully developed state exponentially with distance x from the entry. The steady flow is a function of xν/R2u0 where ν is the kinematic viscosity, R is the tube radius and u0 is the entry velocity. It is shown that within the limits of experimental error, an oscillating flow follows the steady flow development if u0 is the instantaneous entry velocity and if the characteristic length is changed from R to the oscillating boundary-layer thickness in the established flow. © 1971, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 6
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    The non-protein nitrogen composition of grass silages: II. The changes occurring during the storage of silage (1970)
    Cambridge University Press
    Details
    Publication Date: 1970-12-01
    Description: SUMMARYThe nitrogenous composition of the water soluble fraction of maturing grass silage was investigated in detail. Empirical methods of group analysis demonstrated the complete absence of water soluble proteins, and that the major changes, involving the formation of amino acids and volatile amines, were completed within the first 2 months of ensiling. These methods were unable to account for a high proportion of the soluble nitrogen. Changes occurring within the soluble carbohydrate and volatile fatty acid fractions indicated that while secondary fermentations occurred some 8 months after ensiling they did not have any marked influence on the nitrogenous components.A detailed analysis of the individual components of the nitrogenous fraction was undertaken using both conventional methods of ion exchange chromatography and techniques developed especially for this purpose (see Hughes, 1969). Selective degradation of the amino acids liberated by the proteolysis of the grass proteins occurred. The volatile basic nitrogen content was comprised of ammonia. The non-volatile amine fraction, which accounted for a considerable proportion of the soluble nitrogen, was mainly composed of putrescine and cadaverine. There was no free histamine and only low concentrations of bound histamine were found. Evidence suggested that these amines were being further metabolized during the storage of the silage.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
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    The non-protein nitrogen composition of grass silage:III. The composition of spoilt silages (1971)
    Cambridge University Press
    Details
    Publication Date: 1971-06-01
    Description: SUMMARYThe nitrogenous composition of the water soluble, non-protein nitrogen fractions of three samples of high-pH-spoilt silage and one sample of overheated silage were examined in detail. The amino acid nitrogen content of the high-pH-spoilt silages declined with increasing extent of spoilage, due to a selective degradation of the amino acids. Losses of amino acids were associated with proportionate increases in the amount of volatile basic nitrogen. Lower aliphatic amines were not present and it was therefore concluded that the ultimate end product of nitrogen metabolism in high-pH-spoilt silages was ammonia. Only low concentrations of putrefaction products, such as putroscine, cadaverine and histamine were present.The composition of the non-protein nitrogen fraction of the overheated silage was unusual in that the ammonia nitrogen content was high and associated with the complete destruction of certain amino acids. The free amino acid nitrogen content was low but this was partially compensated for by a very high ‘peptide’ nitrogen content. There was no evidence of putrefaction products in this silage.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
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    Some international agreement on essentials of stratigraphy (1972)
    Cambridge University Press
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    Publication Date: 1972-01-01
    Description: SummaryAn agreed short text in English, French and German, presents a unified statement on those aspects of stratigraphy that require formal international acceptance. The statement is designed to avoid philosophical hazards and misunderstandings between the three language communities; it also harmonizes differences of three national traditions as far as is yet possible.Stratigraphy is presented as an indivisible science dependent for its successful pursuit and synthesis on the application of numerous widely different methods.The argument is presented in successive numbered steps to facilitate its critical discussion.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 9
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    Ordovician stratigraphy of Abereiddy Bay, Pembrokeshire (1971)
    Cambridge University Press
    Details
    Publication Date: 1971-11-01
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 10
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    A Tertiary thrust fault on the southern margin of the Bovey Basin (1971)
    Cambridge University Press
    Details
    Publication Date: 1971-01-01
    Description: SummaryGeological investigations and borehole drilling on the southern margin of the Bovey basin around Mainbow ball clay mine and Ringslade open pit have shown that Devonian slate up to 30 m thick is superimposed on Tertiary sediments. A drag fold beneath the slate indicates that the slate has moved eastwards over the Tertiary material. As the slate is relatively intact and not disaggregated, hillcreep cannot be responsible for the superimposition. A large landslip involving a rotational shear cannot be responsible, as the movement plane dips into the hill over too large an area. The southern margin of the Bovey basin is therefore interpreted as a thrust fault of Tertiary age, with thrust plane dipping 10° to 30° S. It is suggested that this is a rejuvenation of the Variscan thrust recognized in the Bickington area and further west in the Holne area and that the movement on the Tertiary thrust is related to the dextral wrench movement on the Sticklepath fault.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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