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  • 1
    Electronic Resource
    Electronic Resource
    Oscillatory Stokes flow in periodic porous media (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2099-2116 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The unsteady Stokes equations for the microscopic flow in model porous media subject to an oscillatory pressure gradient are solved. The media consist of periodic lattices (SC, BCC, FCC) of spheres ranging from dilute systems with isolated spheres to highly concentrated consolidated media with overlapping spheres. Detailed results are presented for the dynamic permeability and comparisons are made with previously published results, asymptotic limits, and approximate theories. The wave speed and attenuation rate for acoustic waves are evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858507
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  • 2
    Electronic Resource
    Electronic Resource
    A periodic grain consolidation model of porous media (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 38-46 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Calculations are presented for a periodic grain consolidation model of porous media. The model is an extension of previous work on lattices of spheres, in which the radius of the spheres is allowed to increase past the point of close touching to form a consolidated medium. A collocation method is used for the solution of Stokes flow in terms of Lamb's general solution in spherical coordinates. Excellent accuracy is achieved with only moderate computational effort. At low concentrations up to the close touching limit excellent agreement is found with the earlier calculations of Zick and Homsy [J. Fluid Mech. 115, 13 (1982)]. For high concentrations above the close touching limit, an asymptotic theory is presented that agrees within a few percent with the numerical computations over the entire consolidated range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857545
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of pressure gradients on Stokes flows over cavities (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 112-114 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Prior studies of Stokes flow over cavities have been limited to simple shear and simple stagnation point flows. In the present work, it is shown that the presence of a transverse pressure gradient has a dramatic effect on the character of the flow, eliminating the separated flow region in many cases. Consequences of this phenomenon for mass transfer are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857687
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The kinematics of the four-roll mill (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 274-276 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical computations are employed to study the flow field produced by a four-roll mill. The radius of the cylinders a, the cylinder spacing 2b, and the size 2l of the square container are varied to assess the effects on the kinematics of the flow field. It is found that a ratio of a/b=0.625 with l/b≥3.0 produces the best approximation to a pure extensional flow. With these parameter values, the extension rate remains constant with an error of less than 1% over an axial region x/b≤0.5. By contrast, the commonly accepted design a/b=0.772 suggested by Fuller and Leal [J. Polym. Sci. Polym. Phys. 19, 557 (1981)] produces a variation in extension rate of 50% over the same region. Streamline patterns and velocity gradient error contours are presented for these two designs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858782
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  • 5
    Electronic Resource
    Electronic Resource
    Instability of compound vortex layers and wakes (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2965-2975 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of two adjoining vortex layers with constant vorticity of opposite sign is analyzed. Linear stability analysis shows that two families of instability may exist, depending on the relative strength of the vortex layers. The first type for moderate and long waves produces simultaneous growth of disturbances on both layers, while the second for short waves is associated primarily with the weaker layer. Numerical calculations show that the nonlinear growth of the various types of instability leads to asymptotic states of different character. For wake-like flows with equal but opposite vorticity distributions, the fastest growing eigenmodes lead to the formation of a classic vortex street with an aspect ratio of 0.345. Longer waves lead to the break up of the layer into a number of small vortex regions producing disorganized motion and a general dispersal of the wake vorticity. For compound shear layers with unequal strength, the fastest growing modes show a progression from wake-like behavior to pure shear-layer behavior as the strength of the second layer diminishes. In addition, there is a new type of instability associated with short-wavelength disturbances on the weaker layer. In this case, the shear layer ejects the opposite signed vorticity along with an equal quantity of its own circulation. The ejected vorticity propagates away from the layer at a 45° angle in the form of neutral vortex pairs. The remaining vorticity forms a simpler shear layer of reduced strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866074
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  • 6
    Electronic Resource
    Electronic Resource
    Boundary integral/spectral element approaches to the Navier-Stokes equations (1992)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 15 (1992), S. 1361-1381 
    Details
    ISSN: 0271-2091
    Keywords: Boundary integral ; Spectral methods ; Navier-Stokes ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Numerical algorithms are presented which combine spectral expansions on elemental subdomains with boundary integral formulations for solving viscous flow problems. Three distinct algorithms are described. The first demonstrates the use of spectral elements for the classic boundary integral method for steady Stokes flow. The second extends this algorithm to include domain integrals for solution of the unsteady Navier-Stokes equations. The third algorithm explores the use of boundary integrals as a means of consolidating uncoupled elemental solutions in a domain decomposition approach. Numerical results demonstrating high-order convergence are presented in each case.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650151202
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    Paper (German National Licenses)
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