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  • 1
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    Moscow MV Lomonosov State University Radiocarbon Dates I (1980)
    Cambridge University Press
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    Publikationsdatum: 1980-01-01
    Beschreibung: The following list sums up the results of radiocarbon age determinations obtained at the Laboratory in 1974-1975. The list is prefaced with a brief description of the measurement procedure and discussion of some methodological aspects of the investigation that result in a higher accuracy of dating.
    Print ISSN: 0033-8222
    Digitale ISSN: 1945-5755
    Thema: Klassische Archäologie , Energietechnik , Geologie und Paläontologie
    Publiziert von Cambridge University Press
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  • 2
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    Axisymmetric stagnation flow of a spherical particle near a finite planar surface at zero Reynolds number (1982)
    Cambridge University Press
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    Publikationsdatum: 1982-09-01
    Beschreibung: The general axisymmetric creeping motion of a spherical particle in a stagnation region near a finite surface is modelled by the motion of a sphere of arbitrary size towards a disk for the following conditions: (a) pure translation in quiescent fluid, (6) uniform flow past a fixed sphere-disk configuration, and (c) a neutrally buoyant sphere carried by the fluid towards a disk. The combined analytic and numerical solution procedure is similar to that described in Dagan, Weinbaum & Pfeffer (1982 b) for the motion of a sphere towards an orifice. The drag force acting on the sphere and on the disk under the flow conditions mentioned above is presented. In addition, the fluid velocity field has been obtained for the case of uniform flow past a fixed sphere-disk configuration. These solutions show the formation and coalescence of separated regions of closed streamlines adjacent to the sphere and the disk. © 1982, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 3
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    General theory for the creeping motion of a finite sphere along the axis of a circular orifice (1982)
    Cambridge University Press
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    Publikationsdatum: 1982-04-01
    Beschreibung: This paper presents the first infinite-series solutions to the creeping-flow equations for the axisymmetric motion of a sphere of arbitrary size towards an orifice whose diameter is either larger or smaller than the sphere. To obtain the solution the flow field is partitioned in the plane of the opening, and for the flow to the left and right of the fluid interface separate solutions are developed that satisfy the viscous-flow boundary conditions in each region and unknown functions for the axial and radial velocity components in the plane of the opening. The continuity of the fluid stress tensor at the matching interface leads to a set of dual integral equations which are solved analytically to determine the unknown functions for the velocity components in the matching plane. A boundary collocation technique is used to satisfy the no-slip boundary conditions on the surface of the sphere.The accuracy and convergence of the present solution is tested by detailed numerical comparison with the exact bipolar co-ordinate solutions of Brenner (1961) for the drag on a sphere translating perpendicular to an infinite plane wall up to a distance of 0.1 sphere radii and is found to be in agreement to five significant digits. The converged-series collocation solutions are presented for the sphere in motion in quiescent fluid or for flow past a rigidly held sphere positioned axisymmetrically near a fixed orifice. Solutions are also presented for the zero-drag velocity of a neutrally buoyant sphere in a flow through an orifice, and the pressure-volume flow relation for a ball-valve geometry. © 1982, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 4
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    The self-excited axisymmetric jet (1982)
    Cambridge University Press
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    Publikationsdatum: 1982-02-01
    Beschreibung: The characteristics of a self-excited axisymmetric air jet driven by a whistler (i.e. pipe-collar) nozzle have been explored experimentally for various choices of the controlling parameters: namely, pipe length, jet diameter, collar length, step height, and jet speed. By appropriate choices of these parameters as well as the stage and mode (half- and full-wave), the self-sustained excitation has been induced at specific values of the excitation amplitude and the Reynolds number RD. The jet characteristics up to Rd 3.1 x 105 and x/D 60 have been documented for both laminar and turbulent flows at the pipe exit. Comparison with corresponding unexcited-jet data reveals that self-excitation produces a large increase in the fluctuation intensity in the near field of the jet, while it increases the jet spread and decay rate for the entire x-range of measurement. The dependence of the jet structure on the initial condition is stronger when self-excited than when unexcited. The first stage of excitation always produces the highest turbulence augmentation and the spectral evolution is significantly modified by self-excitation up to x/D 6. The excitation produces a significant increase in the broad-band turbulence level over that of the unexcited jet. The broad-band amplification is maximized at x/D 4 and is the highest at the largest Rd studied.These data suggest interesting possibilities for the self-excited jet in the augmentation or control of entrainment, mixing and aerodynamic noise production. © 1982, Archives Europeennes de Sociology. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 5
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    Flow between rotating disks. Part 1. Basic flow (1983)
    Cambridge University Press
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    Publikationsdatum: 1983-09-01
    Beschreibung: Laser-Doppler velocity measurements were obtained in water between finite rotating disks, with and without throughflow, in four cases: ω1= ω2= 0; ω2/ω1=- 1; ω2/ω1=0; ω2/ω1= 1. The equilibrium flows are unique, and at mid-radius they show a high degree of independence from boundary conditions in r. With one disk rotating and the other stationary, this mid-radius ‘limiting flow ’ is recognized as the Batchelor profile of infinite-disk theory. Other profiles, predicted by this theory to coexist with the Batchelor profile, were neither observed experimentally nor were they calculated numerically by the finite-disk solutions, obtained here via a Galerkin, B-spline formulation. Agreement on velocity between numerical results and experimental data is good at large values of the ratio RQ/Re, where Rq= Q/2πVs Is the throughflow Reynolds number and Re= R22ω/v is the rotational Reynolds number. © 1983, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 6
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    The effect of a passive cross-stream temperature gradient on the evolution of temperature variance and heat flux in grid turbulence (1983)
    Cambridge University Press
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    Publikationsdatum: 1983-03-01
    Beschreibung: The evolution of temperature variance and heat flux in decaying grid turbulence with a linear cross-stream temperature gradient is studied by producing the temperature gradient by means of two different methods: (a) by placing a ‘mandoline’ (Warhaft & Lumley 1978) downstream from the grid but with its wires differentially heated for the present study, and (b) by differentially heating ribbons of nichrome (a ‘toaster’) placed in the plenum chamber of the wind tunnel. For the former method the initial thermal/mechanical lengthscale ratio LθL was varied by changing the mandoline configuration. For this method it is shown that the gradient causes Lθ/L to equilibrate to a value of about 0.9 regardless of its initial value, and that when this value is achieved the temperature variance increases approximately linearly with time. The toaster was used to produce a temperature gradient without the associated initial temperature variance (and initial thermal lengthscale) that is necessarily produced by the mandoline wires; for the toaster the temperature variance was produced solely by the action of turbulence against the temperature gradient. For this experiment too, the thermal variance grew linearly with time, and Lθ/L was approximately the same as the equilibrium value for the mandoline experiments. The equilibrium value of the ratio of temperature-variance production to temperature-variance dissipation was approximately 1.5 for all of the experiments. The ratio of the mechanical-dissipation/thermal-dissipation timescales was also found to equilibrate, but there was considerably more scatter in the data for this parameter. The values of the equilibrium length and timescale ratios were not affected by the magnitude of the temperature gradient, which was varied for both experiments. Good transverse homogeneity in the thermal field was achieved in all cases, in contrast with previous experiments (using heated grids). © 1983, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 7
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    Asymmetric flow between parallel rotating disks (1984)
    Cambridge University Press
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    Publikationsdatum: 1984-09-01
    Beschreibung: Flows occurring between parallel rotating disks have recently been generalized by Parter & Rajagopal (1984) to include solutions that are not axisymmetric. They prove existence, whereas in the present paper we report, for the first time, numerical results for two cases: (i) rotation about a common axis, and (ii) rotation about distinct axes. Calculations were performed for two values of the Ekman number E = v /d2ω at the relative disk rotations of s= 0.8, s= 0 and s= 0.25, where s= ω2/ω1. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 8
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    The interference of thermal fields from line sources in grid turbulence (1984)
    Cambridge University Press
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    Publikationsdatum: 1984-07-01
    Beschreibung: The interference of passive thermal fields produced by two (and more) line sources in decaying grid turbulence is studied by using the inference method described by Warhaft (1981) to determine the cross correlation coefficient p between the temperature fluctuations produced by the sources. The evolution of p as a function of downstream distance, for 0.075 〈 d/l 〈 10, where d is the wire spacing and l is the integral lengthscale of the turbulence, is determined for a pair of sources located at various distances from the grid. It is found that p may be positive or negative (thereby enhancing or diminishing the total temperature variance) depending on the line source spacing, their location from the grid and the position of measurement. It is also shown that the effects of a mandoline (Warhaft & Lumley 1978) may be idealized as the interference of thermal fields produced by a number of line sources. Thus new light is shed on the rate of decay of scalar variance dissipation. The thermal field of a single line source is also examined in detail, and these results are compared with other recent measurements. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Digitale ISSN: 1469-7645
    Thema: Maschinenbau , Physik
    Publiziert von Cambridge University Press
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  • 9
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    Fourth BIOMASS Progress Report (1983)
    Cambridge University Press
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    Publikationsdatum: 1983-09-01
    Print ISSN: 0032-2474
    Digitale ISSN: 1475-3057
    Thema: Ethnologie , Geographie
    Publiziert von Cambridge University Press
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  • 10
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    Third BIOMASS Progress Report (1982)
    Cambridge University Press
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    Publikationsdatum: 1982-09-01
    Print ISSN: 0032-2474
    Digitale ISSN: 1475-3057
    Thema: Ethnologie , Geographie
    Publiziert von Cambridge University Press
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