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  • Articles  (114)
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  • 1
    Electronic Resource
    Electronic Resource
    Induced anisotropy in large ice shields: theory and its homogenization (1998)
    Springer
    Continuum mechanics and thermodynamics 10 (1998), S. 293-318 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: For polycrystalline ice, an isothermal flow law is derived from microscopic considerations concerning constitutive equations and kinematic assumptions. On the basis of an elasto-plastic decomposition of the deformation gradient on the grain level and by assuming a continuous distribution of different orientated grains in the vicinity of each material point the classical macroscopic field quantities are obtained by calculating the weighted mean values of the associated microscopic quantities. The weighting function is represented by a so called Orientation Distribution Function (ODF). For the general two dimensional (plane and rotationally symmetric) flow regime analytical representations of the ODF are derived under the assumption of a uniform stress distribution over all polycrystals (Sachs-Condition) and a plane or rotationally symmetric orientation distribution. Additionally, the influence of the macroscopic constitutive relations on the microscopic level is restricted to isotropic parts only. Simple examples are used to demonstrate the ability of the ODF to perform the evolving texture. The microscopic constitutive relation for the dissipation potential is assumed to be an objective function of the stress deviator and is expressed as a polynomial law up to the power $n_{max}=4$ , as proposed by Lliboutry (1993). A second order structure tensor which depends on the ODF is introduced to consider induced anisotropy. The resulting macro fluidities (inverse viscosities) are then calculated from the analytical representation of the ODF for the case of uniaxial loading underlying linear $n_{max}=1$ and nonlinear $n_{max}=3$ material behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001610050095
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  • 2
    Electronic Resource
    Electronic Resource
    Modeling wind-induced circulation in the homogeneous Lake Constance using k-ɛ closure (1998)
    Springer
    Aquatic sciences 60 (1998), S. 266-277 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Turbulence, k-ɛ model, wind-driven currents, eddy viscosity, vertical mixing, inertial oscillations.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: Barotropic models of wind-driven circulation commonly use vertical eddy-viscosities which are prescribed functions of depth and applied wind speed rather than a parameterization that is dictated by the turbulence intensity. We use a first order k-ɛ-closure to do this and demonstrate important qualitative differences with this classical turbulence closure in the pattern of wind induced barotropic currents in ideal basins, as well as in Lake Constance: penetration and Ekman layer depths respond with some delay time to the applied wind history as does the attenuation of inertial oscillations established by the wind. This also affects the topographically-induced current pattern. We demonstrate these features by subjecting the homogeneous Lake Constance to impulsive and spatially uniform external wind forcing of different strengths in the long direction. Specifically, the shallow-water equations are coupled via the vertical eddy-viscosity with the correspondingly approximated balance laws of turbulent kinetic energy and its dissipation, which are then solved numerically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00001317
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  • 3
    Electronic Resource
    Electronic Resource
    A letter from the editors (1989)
    Springer
    Continuum mechanics and thermodynamics 1 (1989), S. 1-1 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01125882
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  • 4
    Electronic Resource
    Electronic Resource
    A letter from the editors (1993)
    Springer
    Continuum mechanics and thermodynamics 5 (1993), S. 1-1 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01135370
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  • 5
    Electronic Resource
    Electronic Resource
    A letter from the editors (1995)
    Springer
    Continuum mechanics and thermodynamics 7 (1995), S. 385-385 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175664
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  • 6
    Electronic Resource
    Electronic Resource
    Original Article On the frame dependence and form invariance of the transport equations for the Reynolds stress tensor and the turbulent heat flux vector: its consequences on closure models in turbulence modelling (1996)
    Springer
    Continuum mechanics and thermodynamics 8 (1996), S. 341-349 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: The present paper shows that the transport equations governing second order turbulent closures are form invariant, but remain frame dependent through the emergence of the body force; thus they do not fulfil the principle of material frame indifference as formulated by Truesdell & Noll (1965). However, this frame dependence corresponds to that first discussed by Müller (1972) and today developed in the framework of the new concept of extended thermodynamics. Following this new concept, these relations are consequently incorporated as additional basic balance laws. The results are: 1) in the case of the Reynolds-stress-transport equation, this eliminates the so-called constraints imposed in [15–17, 19] on turbulence models; 2) to ensure the closure of the new set of basic balance laws, closure assumptions can then be considered as proper constitutive equations which must be restricted by the well known constitutive theory principles in extended thermodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001610050048
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  • 7
    Electronic Resource
    Electronic Resource
    A letter from the editors (1995)
    Springer
    Continuum mechanics and thermodynamics 7 (1995), S. 259-259 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01176287
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  • 8
    Electronic Resource
    Electronic Resource
    The thermomechanical response of the Greenland Ice Sheet to various climate scenarios (1996)
    Springer
    Climate dynamics 12 (1996), S. 243-260 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Using a three dimensional numerical model for land based ice sheets in the shallow ice approximation simulations are performed to determine the velocity and temperature distributions within the Greenland Ice Sheet through time for various climate scenarios. The ice is treated as a rheologically nonlinear heat conducting viscous fluid and the substrate is a heat conducting rigid solid. This system is fed from above by prescribing as the climatic inputs the atmospheric temperature and the accumulation-ablation-rate functions at the free surface and from below by the geothermal heat. We present the governing equations in the shallow-ice approximation, discuss the parameterizations used in the descriptions of the ice-surface temperature and accumulation-ablation functions, briefly state how the complicated initial boundary value problem is numerically solved, and how the input data that are available from measurements are implemented. Results of preliminary calculations disclose how the model performs and delimit its validity. We study the role played by basal sliding and make clear that sliding should be accounted for where ever the basal ice is temperate and that the frictional heat generated in this sliding is thermomechanically significant. We also study the reaction of the Greenland Ice Sheet to various climate scenarios and make clear that today's thermal regime depends significantly upon the prior climate history. Moreover, the thermomechanical properties of the ice are equally significant as is the thermal interaction of the Ice Sheet with the rockbed beneath.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219499
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  • 9
    Electronic Resource
    Electronic Resource
    The thermomechanical response of the Greenland ice sheet to various climate scenarios (1996)
    Springer
    Climate dynamics 12 (1996), S. 243-260 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. Using a three dimensional numerical model for land based ice sheets in the shallow ice approximation simulations are performed to determine the velocity and temperature distributions within the Greenland Ice Sheet through time for various climate scenarios. The ice is treated as a rheologically nonlinear heat conducting viscous fluid and the substrate is a heat conducting rigid solid. This system is fed from above by prescribing as the climatic inputs the atmospheric temperature and the accumulation-ablation-rate functions at the free surface and from below by the geothermal heat. We present the governing equations in the shallow-ice approximation, discuss the parameterizations used in the descriptions of the ice-surface temperature and accumulation-ablation functions, briefly state how the complicated initial boundary value problem is numerically solved, and how the input data that are available from measurements are implemented. Results of preliminary calculations disclose how the model performs and delimit its validity. We study the role played by basal sliding and make clear that sliding should be accounted for where ever the basal ice is temperate and that the frictional heat generated in this sliding is thermomechanically significant. We also study the reaction of the Greenland Ice Sheet to various climate scenarios and make clear that today's thermal regime depends significantly upon the prior climate history. Moreover, the thermomechanical properties of the ice are equally significant as is the thermal interaction of the Ice Sheet with the rockbed beneath.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050106
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  • 10
    Electronic Resource
    Electronic Resource
    Large scale water movements in lakes (1991)
    Springer
    Aquatic sciences 53 (1991), S. 100-135 
    Details
    ISSN: 1420-9055
    Keywords: Physical limnology ; hydrodynamic fundamentals ; exterior/interior seiches ; coupled oscillations ; barotropic/baroclinic circulation ; three dimensional numerical techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By large scale circulation in lakes one means motions whose characteristic length scales extend over most parts or all of the water masses in a lake or the ocean. We present the governing equations and motivate, by means of a scale analysis, the various simplified versions of model equations that are in use in computational lake dynamics. This scale analysis not only permits rational deduction of the reduced equations, it equally provides a means of estimating their limitations. These are discussed as are the difficulties and the peculiarities inherent in the proposed equation sets. Special features of external and internal wave motions are studied. For barotropic oscillations of a lake system (Lake of Lugano) it is shown that substantial water masses are exchanged between the individual basins at the resonating periods. Baroclinic seiches of a three layer model in which each layer is effective within its own domain show (for the North basin of the Lake of Lugano) that mode structures may differ from layer to layer pointing at important modifications of classical interpretations of higher baroclinic wave dynamics. And in large lakes in the equatorial belt theβ-effect forces modifications of the classical understanding of seiche behavior. Long periodic oscillating features may be attributed to topographic Rossby waves or higher baroclinic internal gravity waves; the observational identification is, however, difficult because lack of spatial resolution of the data makes this identification non-unique. We, finally present results of a full nonlinear numerical baroclinic circulation model and demonstrate that it is able to reproduce the gross features of the immediate response to strong storms during a few days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877057
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