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  • 1
    Electronic Resource
    Electronic Resource
    Proper orthogonal decomposition and low-dimensional models for driven cavity flows (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 1685-1699 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A proper orthogonal decomposition (POD) of the flow in a square lid-driven cavity at Re=22,000 is computed to educe the coherent structures in this flow and to construct a low-dimensional model for driven cavity flows. Among all linear decompositions, the POD is the most efficient in the sense that it captures the largest possible amount of kinetic energy (for any given number of modes). The first 80 POD modes of the driven cavity flow are computed from 700 snapshots that are taken from a direct numerical simulation (DNS). The first 80 spatial POD modes capture (on average) 95% of the fluctuating kinetic energy. From the snapshots a motion picture of the coherent structures is made by projecting the Navier–Stokes equation on a space spanned by the first 80 spatial POD modes. We have evaluated how well the dynamics of this 80-dimensional model mimics the dynamics given by the Navier–Stokes equations. The results can be summarized as follows. A closure model is needed to integrate the 80-dimensional system at Re=22,000 over long times. With a simple closure the energy spectrum of the DNS is recovered. A linear stability analysis shows that the first (Hopf) bifurcation of the 80-dimensional dynamical system takes place at Re=7,819. This number lies about 0.7% above the critical Reynolds number given in Poliashenko and Aidun [J. Comput. Phys. 121, 246 (1995)] and differs by about 2% from the first instability found with DNS. In addition to that, the unstable eigenvector displays the correct mechanism: a centrifugal instability of the primary eddy, however, the frequency of the periodic solution after the first bifurcation differs from that of the DNS. The stability of periodic solutions of the 80-dimensional system is analyzed by means of Floquet multipliers. For Re=11,188−11,500 the ratio of the two periods of the stable 2-periodic solution of the 80-dimensional system is approximately the same as the ratio of the two periods of the 2-periodic solution of the DNS at Re=11,000. For slightly higher Reynolds numbers both solutions lose one period. The periodic solutions of the dynamical system at Re=11,800 and the DNS at Re=12,000 have approximately the same period and have qualitatively the same behavior. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869686
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  • 2
    Electronic Resource
    Electronic Resource
    Are lysosomes directly involved in the iron uptake by reticulocytes?
    Amsterdam : Elsevier
    International Journal of Biochemistry 16 (1984), S. 39-45 
    Details
    ISSN: 0020-711X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0020-711X(84)90048-X
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  • 3
    Electronic Resource
    Electronic Resource
    Two mechanisms are involved in the process of iron-uptake by rat reticulocytes
    Amsterdam : Elsevier
    International Journal of Biochemistry 16 (1984), S. 383-389 
    Details
    ISSN: 0020-711X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0020-711X(84)90136-8
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  • 4
    Electronic Resource
    Electronic Resource
    Direct numerical simulation of driven cavity flows (1993)
    Springer
    Flow, turbulence and combustion 51 (1993), S. 377-381 
    Details
    ISSN: 1573-1987
    Keywords: DNS ; periodic and chaotic driven cavity flows ; explicit time-integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Direct numerical simulations of 2D driven cavity flows have been performed. The simulations exhibit that the flow converges to a periodically oscillating state at Re=11,000, and reveal that the dynamics is chaotic at Re=22,000. The dimension of the attractor and the Kolmogorov entropy have been computed. Explicit time-integration techniques are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01082564
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  • 5
    Electronic Resource
    Electronic Resource
    The role of periodic solutions in the Falkner-Skan problem for λ〉0 (1986)
    Springer
    Journal of engineering mathematics 20 (1986), S. 81-93 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Summary The Falkner-Skan equation $$f''' + ff'' + \lambda (1 - f'^2 ) = 0$$ and those being periodic. In both cases, numerical evidence is given for a rich structure of multiple solutions. Branching occurs for λ=1,2,3,.... All solutions can be characterized by means of a special subset of periodic solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039325
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  • 6
    Electronic Resource
    Electronic Resource
    Spectro-Consistent Discretization of Navier-Stokes: a Challenge to RANS and LES (1998)
    Springer
    Journal of engineering mathematics 34 (1998), S. 163-179 
    Details
    ISSN: 1573-2703
    Keywords: spatial discretization schemes ; turbulent flows ; DNS ; LES ; RANS.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract In this paper, we discuss the results of a fourth-order, spectro-consistent discretization of the incompressible Navier-Stokes equations. In such an approach the discretization of a (skew-)symmetric operator is given by a (skew-)symmetric matrix. Numerical experiments with spectro-consistent discretizations and traditional methods are presented for a one-dimensional convection-diffusion equation. LES and RANS are challenged by giving a number of examples for which a fourth-order, spectro-consistent discretization of the Navier-Stokes equations without any turbulence model yields better (or at least equally good) results as large-eddy simulations or RANS computations, whereas the grids are comparable. The examples are taken from a number of recent workshops on complex turbulent flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004316430201
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  • 7
    Electronic Resource
    Electronic Resource
    A new calculation of the wake of a flat plate (1975)
    Springer
    Journal of engineering mathematics 9 (1975), S. 65-70 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Summary A new method is presented for the calculation of the wake of a finite flat plate. The method is based upon the recent investigations of the boundary layer near the trailing edge, which led to the triple-deck structure. This multi-layered structure has now been extended to the “classical” wake, which in fact is the continuation of the lowest two layers of the triple-deck. With this new numerical formulation an accuracy of 10−3% can easily be achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01535498
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  • 8
    Electronic Resource
    Electronic Resource
    Incompressible viscous flow near the leading edge of a flat plate admitting slip (1975)
    Springer
    Journal of engineering mathematics 9 (1975), S. 235-249 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Summary The shear stress at the leading edge, calculated on basis of the Navier-Stokes equations and the no-slip boundary condition, approaches infinity. However, taking into account the mean free path of the molecules, which implies admitting a certain slip, the shear stress becomes inversely proportional to the square root of the Knudsen numberk ifk→0.k is defined as the ratio between the mean free path and the viscous length. The new boundary condition modifies the shear stress only within the Knudsen region of which the size is of the order of 3 to 4 times the mean free path.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01535449
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  • 9
    Electronic Resource
    Electronic Resource
    Playing with nonuniform grids (1992)
    Springer
    Journal of engineering mathematics 26 (1992), S. 119-130 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Numerical experiments with discretization methods on nonuniform grids are presented for the convection-diffusion equation. These show that the accuracy of the discrete solution is not very well predicted by the local truncation error. The diagonal entries in the discrete coefficient matrix give a better clue: the convective term should not reduce the diagonal. Also, iterative solution of the discrete set of equations is discussed. The same criterion appears to be favourable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043231
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  • 10
    Electronic Resource
    Electronic Resource
    Branching of the Falkner-Skan solutions for λ〈0 (1982)
    Springer
    Journal of engineering mathematics 16 (1982), S. 295-308 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Summary The Falkner-Skan equation f‴+ff″+λ(1-f′2)=0,f(0)=f′(0), is discussed for λ〈0. Two types of problems, one with f′(∞)=1 and another with f′(∞)=-1, are considered. For λ=0- a close relation between these two types is found. For λ〈-1 both types of problem allow multiple solutions which may be distinguished by an integer N denoting the number of zeros of f′-1. The numerical results indicate that the solution branches with f′(∞)=1 and those with f′(∞)=-1 tend towards a common limit curve as N increases indefinitely. Finally a periodic solution, existing for λ〈-1, is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00037732
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