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  • 1
    Digitale Medien
    Digitale Medien
    Direct numerical simulation of particle dispersion in homogeneous turbulent shear flows (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 3346-3364 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In a recent paper [Phys. Fluids 12, 2906 (2000)] we presented the results of our direct numerical simulations (DNS) study of the two-way coupling effects of solid particles dispersed in a homogeneous turbulent shear flow. The objective of that study was to describe the physical mechanism associated with two-way coupling. Here, we present a DNS study of the dispersion of small spherical particles and fluid points in a homogeneous turbulent shear flow with one-way coupling. The effects of varying shear number, particle inertia, gravity magnitude, and direction on particle dispersion were studied. Our results show that the particle mean square displacement in the streamwise direction 〈xp,12〉∝t2 for short times, whereas for large times, the time exponent exceeds 3. The larger the particle inertia, the larger is the exponent. 〈xp,12〉 is at least one order of magnitude larger than the mean dispersion in the two lateral directions. This dispersion anisotropy is due to the dominance of the spanwise vortex layers which are elongated and inclined toward the streamwise direction, thus suppressing the velocity fluctuations in the lateral directions. These layers are generated from the inclined longitudinal vortex tubes by the action of the mean shear [Kida and Tanaka (1994)]. Preferential accumulation of particles in homogeneous shear flows at zero gravity is maximum when τp equals the Kolmogorov time scale. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1405443
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  • 2
    Digitale Medien
    Digitale Medien
    On the mechanisms of modifying the structure of turbulent homogeneous shear flows by dispersed particles (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 2906-2930 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The present study is concerned with answering the question: What are the physical mechanisms responsible for the modification of the turbulence structure by solid particles dispersed in a homogeneous shear flow? We employ DNS (direct numerical simulations) to examine the effects of the two-way interaction between the two phases on the turbulence structure. Our results indicate that particles affect the rate of production of turbulence energy via modifying the vorticity dynamics. It is known that regions of large production rate of turbulence energy are sandwiched between counter rotating vortices whose vorticity, ωs, is aligned with the axes of the longitudinal vortex tubes. These longitudinal vortex tubes are strongly inclined toward the streamwise direction due to the imposed mean shear. The stronger ωs is, the larger the production rate. The dispersed solid particles modify the alignment of the local vorticity vector, ω, with the axis of the longitudinal vortex tube. Increasing this alignment increases ωs, which in turn augments the turbulence production rate, and vice versa. In addition, due to the enhanced strain rate of the carrier fluid by the particles, the dissipation rate of turbulence energy is always increased. The particles also reduce the alignment of the vorticity vector with the intermediate eigenvector (β) of the strain rate tensor. This reduction in alignment is due to an increase in the rotational term and particle-source term in the governing equation of the cosine of the angle between the vorticity vector and the intermediate strain eigenvector. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1308509
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  • 3
    Digitale Medien
    Digitale Medien
    Structural studies on electrodeposited indium on steel surfaces (1988)
    Springer
    Journal of materials science 7 (1988), S. 1350-1352 
    Details
    ISSN: 1573-4811
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00719980
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  • 4
    Digitale Medien
    Digitale Medien
    Electropolishing of large cavities under free convection mass transfer controlling conditions (1990)
    Springer
    Journal of materials science 9 (1990), S. 270-272 
    Details
    ISSN: 1573-4811
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00725821
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  • 5
    Digitale Medien
    Digitale Medien
    A parametric axisymmetric model study on the interface motions in porous-surfaced tibial implants (1989)
    Springer
    Annals of biomedical engineering 17 (1989), S. 411-421 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Axisymmetric finite element ; Interface motion ; Porous tibial implant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract The effects of a number of variables on the interface relative motions in poroussurfaced tibial implants are investigated using a simplified axisymmetric finite element model. The parameters considered are contact or link spacing, height of the central metal stem, presence of a circumferential metal flange, presence of a UHMWP articular plate resting freely on or fixed to the metal base, resting of the prosthesis edge on the cortical shell, and type of the metal alloy. In order to represent the immediate post-surgical situation with no bone ingrowth, the interface between the bone and porous-surfaced metal is modelled by frictionless rigid links oriented normal to the interface. Cases are also studied in which the horizontal interface is assumed to be fixed while the vertical interface remains frictionless. The magnitudes of the interface motion are negligibly affected by the variation in the link spacing from 0.3 mm to about 3.0 mm. The interface relative motion is predicted to decrease in cases with a shorter central metal stem, with the addition of a circumferential metal flange, with the use of more rigid prosthesis, and with the addition of a UHMWP articular plate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02368059
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  • 6
    Digitale Medien
    Digitale Medien
    Utilization of aromatic compounds by phototrophic purple nonsulfur bacteria (1994)
    Springer
    Biodegradation 5 (1994), S. 71-76 
    Details
    ISSN: 1572-9729
    Schlagwort(e): purple nonsulfur bacteria ; utilization of aromatic compounds ; benzoate ; benzyl alcohol ; vanillate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Biodegradation of aromatic compounds byRhodopseudomonas blastica andRhodospirillum rubrum appears to be lacking in the literature. The above species grew phototrophically (illuminated anaerobic conditions) on a variety of organic compounds. They were found to degrade benzoate, benzyl alcohol, 4-hydroxy-3,5-dimethoxybenzoate (Syringate) and 4-hydroxy-3-methoxybenzoate (vanillate). The ability of the above species to photocatabolize aromatic compounds indicates that these organisms may be ecologically significant as scavengers of aromatic derivatives in illuminated anaerobic habitats in nature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00695216
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  • 7
    Digitale Medien
    Digitale Medien
    Natural convection mass transfer at conical surfaces (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 196-199 
    Details
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Rates of natural convection mass transfer were determined at vertical cones by measuring the limiting current of the cathodic deposition of copper from acidified copper sulphate solution. Variables studied were cone position (upward or downward apex), apex angle of the cone and copper sulphate concentration. For vertical cones with upward pointing apex the data were represented in the range 4.9×1010〈(Sc Gr)〈9×1011 by the equation: $$Sh = 0.128 (Sc Gr)^{0.33}$$ For vertical cones with downward pointing apex the data fit the equation: $$Sh = 0.877 (Sc Gr)^{0.25}$$
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01009262
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  • 8
    Digitale Medien
    Digitale Medien
    Effect of surfactants on the rate of mass transfer at gas-evolving electrodes (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 219-224 
    Details
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The effect of sodium lauryl sulphate surfactant on the mass transfer coefficient of the cathodic reduction of ferricyanide ion and the anode oxidation of ferrocyanide ion at hydrogen- and oxygen-evolving electrodes, respectively, was studied. Also, the effect of sodium lauryl sulphate on the gas hold-up and cell voltage was studied. The presence of surfactant in the electrolyte was found to decrease the mass transfer coefficient by an amount ranging from 7.6 to 81% depending on the operating conditions. Gas hold-up and cell voltage were found to increase in the presence of surfactant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01062304
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  • 9
    Digitale Medien
    Digitale Medien
    The role of natural convection mass transfer in the kinetics of electropolishing of horizontal surfaces (1979)
    Springer
    Journal of applied electrochemistry 9 (1979), S. 1-6 
    Details
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Limiting currents were measured for the electropolishing of horizontal copper electrodes facing downwards in phosphoric acid solution under natural convection conditions. The electrode diameter was varied from 1–6 cm and the phosphoric acid concentration between 8–12 M. The limiting current was found initially to decrease with electrode diameter and then to remain constant with further increase. Within the concentration range of phosphoric acid used, the limiting current was found to decrease with phosphoric acid concentration. Mass transfer data was found to agree closely with the equation $$(Sh) = 0 \cdot 18[(Sc)(Gr)]^{0 \cdot 33} for 1 \cdot 1 \times 10^9〈 (Sc)(Gr)〈 2 \cdot 46 \times 10^{11} .$$
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00620580
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  • 10
    Digitale Medien
    Digitale Medien
    Natural convection mass transfer inside cylindrical cavities of different orientation (1995)
    Springer
    Journal of applied electrochemistry 25 (1995), S. 677-681 
    Details
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Rates of free convection mass transfer inside cylindrical cavities were studied by measuring the limiting current for the cathodic deposition of copper from acidified copper sulphate solution using a cylindrical anode placed inside the cavity. Variables studied were cavity orientation (vertical with upward facing opening, vertical with downward facing opening and horizontal), physical properties of the solution and cavity dimensions (diameter and depth). For vertical cavities with upward facing openings the data were correlated by the equation Sh = 0.257 (Sc × Gr)0.33 For horizontal cavities the data were correlated by the equation Sh = 0.139 (Sc × Gr)0.33 For vertical cavities with downward facing openings the data were correlated by the equation Sh = 0.187 (Sc × Gr)0.297 A comparison between the present data and the data obtained from other cavity geometries was made to shed light on the role of cavity geometry in thermosyphon design.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00241930
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