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  • 1
    Electronic Resource
    Electronic Resource
    The linear and nonlinear shear instability of a fluid sheet (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2392-2400 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical and computational investigation of the inviscid Kelvin–Helmholtz instability of a two-dimensional fluid sheet is presented. Both linear and nonlinear analyses are performed. The study considers the temporal dilational (symmetric) and sinuous (antisymmetric) instability of a sheet of finite thickness, including the effect of surface tension and the density difference between the fluid in the sheet and the surrounding fluid. Previous linear-theory results are extended to include the complete range of density ratios and thickness-to-wavelength ratios. It is shown that all sinuous waves are stable when the dimensionless sheet thickness is less than a critical value that depends on the density ratio. At low density ratios, the growth rate of the sinuous waves is larger than that of the dilational waves, in agreement with previous results. At higher density ratios, it is shown that the dilational waves have a higher growth rate. The nonlinear calculations indicate the existence of sinuous oscillating modes when the density ratio is of the order of 1. Sinuous modes may result in ligaments interspaced by half of a wavelength. Dilational modes grow monotonically and may result in ligaments interspaced by one wavelength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858177
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  • 2
    Electronic Resource
    Electronic Resource
    Nonlinear growth of Kelvin–Helmholtz instability: Effect of surface tension and density ratio (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1845-1855 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear evolution of initially small disturbances at an interface separating two fluids of different density and velocity, including surface tension effects, is investigated with the use of the vortex-sheet discretization approach. The location of the interface is tracked in time by following the motion of each vortex under the combined influence of all other vortices. The influence of surface tension and density discontinuity is incorporated in an equation governing the evolution of the circulation of each vortex. Increasing the surface tension or the density ratio is shown to reduce the growth of the disturbance. For density ratios larger than 0.2 a critical wavenumber exists that divides the unstable part of the spectrum into a region where a vorticity singularity can develop (with interface rollup) and a region where two finite vortical centers are formed (with partial or no rollup). For lower density ratios this bifurcation phenomenon is not observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866682
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  • 3
    Electronic Resource
    Electronic Resource
    Heat transfer analysis of a particle-containing channel flow (1991)
    Springer
    Heat and mass transfer 26 (1991), S. 153-161 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Diese Arbeit beschreibt ein analytisches Modell der Wärmeübertragung in einer zweidimensionalen, stetigen, nichtreaktiven mit Partikeln beladenen Kanalströmung. Zwischen zwei parallelen, isolierten Platten wurde eine ideale Gasströmung mit einer bestimmten gleichmäßigen Geschwindigkeit angenommen und die nichtverdampfenden Partikel sind so anzusehen, falls sie in einer dünnen Schicht enthalten sind, die in der Symmetrieebene eingeblasen wird. Zwei dimensionslose Parameter, die die Lösung beeinflussen, sind beschrieben worden. Dies sind die effektive Gas-DiffusionskonstanteK und die PartikelzahldichteP. Die linearen, gekoppelten Differentialgleichungen, die den Energieaustausch zwischen Gas- und Flüssigkeitsphase erfassen, sind mit der Greenschen Funktion gelöst worden. Durch dieses Verfahren erzielt man eine Reihe von Volterra-Integralgleichungen als Lösung der Energiegleichung der Gasphasen. Eine Reihe von Lösungen dieser Integralgleichungen wurde mit dem sukzessiven Substitutionsverfahren erhalten und die Terme wurden bis zur zweiten Ordnung berechnet.
    Notes: Abstract This paper describes an analytical model of heat transfer in a two-dimensional, steady, nonreacting particle-containing channel flow. An idealized gas flow of specified uniform velocity between insulated parallel plates is assumed and the nonvaporizing particles are conceptualized as contained within an thin sheet injected at the symmetry plane. Two dimensionless parameters that affect the solution are described. These are the effective gas diffusivityK and the dimensionless particle number densityP. The linear, coupled differential equations governing the energy exchange between the gas and liquid phases are solved by means of the Green's function technique. This procedure yields a Volterra integral-series equation as the solution of the gas-phase energy equation. A series solution of this integral equation is obtained by the method of successive substitutions and terms up to second order are calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01590115
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Numerical analysis of the deformation and solidification of a single droplet impinging onto a flat substrate (1993)
    Springer
    Journal of materials science 28 (1993), S. 3313-3321 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An existing model has been modified to explore the deformation and solidification of a single droplet impinging on a substrate. The modification accounts for possible solid fraction of material at impact. Numerical results predict that the kinetic energy dominates the process at impinging velocities greater than about 100 m s−1. In addition, the thermal diffusivity of the solidifying material controls the process, but the temperature of the substrate relative to the melting temperature of the material must be considered when comparing materials. It is believed that droplets solidifying into thinner, wider discs would reduce porosity; therefore, dense materials accelerated to high speed would solidify into masses with the highest bulk density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354253
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    An improved model for droplet solidification on a flat surface (1997)
    Springer
    Journal of materials science 32 (1997), S. 1519-1530 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An existing model of the deformation and solidification of a single droplet impinging on a cold surface has been revised and improved. The original model is based on a two-dimensional axisymmetric flow approximation of the velocity field, the Neumann solution to the one-dimensional Stefan solidification problem, and an integral mechanical energy balance. The improved model features a more appropriate velocity field which satisfies the no-shear boundary condition at the free surface, and an accurate derivation of the dissipation term from the mechanical energy equation. This equation has been solved numerically. Comparisons of the original and the improved models have been performed. Results show that the original model over-estimates the final splat size by about 10%. The discrepancy is more pronounced at larger Weber numbers, where viscous effects dominate. The effects of the Weber number, We, the Reynolds numbers, Re, and the solidification parameter have been investigated through detailed numerical calculations. Two regimes of spreading/solidification have been identified. If Re/We is small, the process is one of dissipation of the incident droplet kinetic energy; whereas for large values of Re/We the process can rather be characterized as a transfer between kinetic and potential energy. In the latter case, the variations of the final splat size versus the solidification constant exhibit a non-monotonic behaviour. This indicates that, for a given material, the deposition process can be optimized. Correlations relating the final splat size to the process parameters are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018522521531
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Generalized integral transform solution for boundary layer flow over a sphere (1994)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 18 (1994), S. 721-731 
    Details
    ISSN: 0271-2091
    Keywords: Generalized integral transform technique ; Boundary layer ; Sphere ; 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: The generalized integral transform technique is applied to the boundary layer equations for flow over a sphere in their primitive variables. Even though a diffusion-based eigenvalue problem is used, the velocity profile, shear stress and separation point have been calculated with high accuracy. Low-order approximations are shown to be accurate near the surface and the predictions of the separation point is very good. Comparison with finite difference results shows the better convergence behaviour of the integral transform method.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650180802
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