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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and computational fluid dynamics 10 (1998), S. 3-21 
    ISSN: 1432-2250
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract: Typhoons in the northwest Pacific and hurricanes in the northeast Atlantic are particular instances of a global phenomenon with frequently disastrous consequences known as the Tropical Cyclone (TC). This is an intense cyclone, generated over a tropical ocean with kinetic energy 1018 J or more, which extends over several hundred kilometres and yet is above all characterized by its calm central region: “the eye of the storm”. In a TC (not, of course, to be confused with such completely different phenomena as tornadoes) both the energy input and its dissipation mainly occur within that boundary layer between air and ocean which, at high TC wind speeds of 50–60 m/s, comprises essentially “a third fluid”: ocean spray. Afterwards, as a TC reaches land, disastrous effects of several different kinds may occur, and this paper outlines how fluid mechanics contributes towards worldwide struggles to reduce the human impact of TC disasters.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and computational fluid dynamics 6 (1994), S. 261-280 
    ISSN: 1432-2250
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The lecture begins by sketching some of the background to contemporary jet aeroacoustics. Then it reviews scaling laws for noise generation by low-Mach-number airflows and by turbulence convected at “not-so-low” Mach numbers. These laws take into account the influence of Doppler effects associated with the convection of aeroacoustic sources. Next, a uniformly valid Doppler-effect approximation exhibits the transition, with increasing Mach number of convection, from compact-source radiation at low Mach numbers to a statistical assemblage of conical shock waves radiated by eddies convected at supersonic speed. In jets, for example, supersonic eddy convection is typically found for jet exit speeds exceeding twice the atmospheric speed of sound. The lecture continues by describing a new dynamical theory of the nonlinear propagation of such statistically random assemblages of conical shock waves. It is shown, both by a general theoretical analysis and by an illustrative computational study, how their propagation is dominated by a characteristic “bunching” process. That process—associated with a tendency for shock waves that have already formed unions with other shock waves to acquire an increased proneness to form further unions—acts so as to enhance the high-frequency part of the spectrum of noise emission from jets at these high exit speeds.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Flow, turbulence and combustion 58 (1997), S. 191-206 
    ISSN: 1573-1987
    Schlagwort(e): bubbles ; drops ; spray ; ocean spray ; evaporation ; Tropical Cyclones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Because of the potentially important influence of ‘spray cooling’ on the thermodynamics of Tropical Cyclones, there is a need for estimates of ocean spray distribution at extreme wind speeds, at least twice those for which detailed spray observations have been made. To assist in such extrapolation, a simplified probabilistic model is developed, with the three main effects (gusts, gravity, evaporation) that influence how spray droplets are distributed taken into account, but with as much simplicity as possible in other respects.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of engineering mathematics 30 (1996), S. 35-78 
    ISSN: 1573-2703
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Abstract Helical distributions of stokeslets can valuably model microbial locomotion through a fluid, and also the flow field generated, wherever a flagellum actively executes helical undulations (as in many single-celled algae and protozoa) or where (as in many bacteria) the action of rotary motors causes a passive structure of helical shape (which may be a flagellum or else the cell body itself) to rotate. Here, previous biomechanical studies of such modes of locomotion are extended to include analyses of three-dimensional flow fields. In some cases, a rotlet field (curl of a stokeslet) needs to be incorporated in the models. For example, spirochete swimming is modelled by combined helical distributions of stokeslets and rotlets; the computed flow field being confined to within distances of less than twice the radius of the cell body's helical shape from its axis, while including a powerful jet-like interior flow through the coils of the swimming spirochete.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of engineering mathematics 35 (1999), S. 11-42 
    ISSN: 1573-2703
    Schlagwort(e): hurricanes ; typhoons ; spray ; droplets ; evaporation.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Abstract Serious gaps in knowledge about ocean spray at wind speeds over 40m/s remain difficult to fill by observation or experiment; yet refined study of the thermodynamics of Tropical Cyclones (including typhoons and hurricanes) requires assessment of the hypothesis that 'spray cooling' at extreme wind speeds may act to reduce (i) the initial temperature of saturated air rising in the eyewall and so also (ii) the input of mechanical energy into the airflow as a whole. Such progressive reductions at higher speeds could, for example, make any possible influence of future global warming on Tropical Cyclone intensification largely self-limiting. In order to help in extrapolation of knowledge on ocean spray to extreme wind speeds, a probabilistic analysis is introduced which allows for the effects of gusts, gravity and evaporation on droplet distributions, yet in other respects is as simple as possible. Preliminary indications from this simplified analysis appear to confirm the potential importance of spray cooling.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of engineering mathematics 30 (1996), S. 25-34 
    ISSN: 1573-2703
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Abstract Lorentz [1] pioneered the representation of flows at very low Reynolds number by a surface distribution of stokeslets — whose strengths, nowadays, are computed by surface-velocity collocations. That method is here compared with a representation widely used in flagellar hydrodynamics, by a curvilinear distribution of stokeslets and dipoles along the flagellar centreline; with the velocity of each cross-section expressed as a centreline value of the combined fields of singularities beyond a certain cutoff distance. The latter is also a good representation, and offers moreover some computational advantages. This paper establishes the equivalence of the two representations, and identifies those properties of Stokes flows which make both the dipoles and the cutoff essential to that equivalence.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 1994-10-01
    Print ISSN: 0935-4964
    Digitale ISSN: 1432-2250
    Thema: Maschinenbau , Physik
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 1998-01-01
    Print ISSN: 0935-4964
    Digitale ISSN: 1432-2250
    Thema: Maschinenbau , Physik
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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