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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 3670-3677 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the peculiar impact properties of small spherical shells filled with a viscous liquid. Upon collisions of two identical liquid-filled shells, the fluid is progressively set in rotation by the shell spin induced by tangential impact forces. An analysis of the corresponding fluid motion predicts a collision outcome unlike that of solid spheres where angular velocity is uniform. Observations of colliding vitamin-E pills reveal that the point of contact is rarely involved in gross slip. In the direction of the line of centers, collisions are adequately described by a kinematic restitution coefficient. In the perpendicular direction, they generally exhibit rolling contact. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 1213-1233 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We consider dense, relatively shallow flows of 3 mm glass spheres moving down a chute with a flat, frictional base of 3.6 m length. Sustained flows are observed at inclinations corresponding to an effective friction between the static and dynamic friction of individual grains. A capacitance instrument records the formation of waves with a dominant component traveling upstream. Simultaneous measurements of granular temperature at the base using a load cell reveal that the waves are accompanied by substantial reduction in granular agitation. A theory incorporating contributions from impulsive and enduring interactions with the base produces quantitative predictions for the range of sustained flows observed in the experiments. Closure of the theory is achieved using a balance between the production and dissipation of angular momentum in a narrow basal shear layer. A linear stability analysis of the corresponding hydraulic equations further suggests the origin of the waves. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 47-57 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Computer simulations of two-dimensional rapid granular flows of uniform smooth inelastic disks under simple shear reveal a dynamic microstructure characterized by the local, spatially anisotropic agglomeration of disks. A spectral analysis of the concentration field suggests that the formation of this inelastic microstructure is correlated with the magnitude of the total stresses in the flow. The simulations confirm the theoretical results of Jenkins and Richman [J. Fluid Mech. 192, 313 (1988)] for the kinetic stresses in the dilute limit and for the collisional stresses in the dense limit, when the size of the periodic domain used in the simulations is a small multiple of the disk diameter. However, the kinetic and, to a lesser extent, collisional stresses both increase significantly with the size of the periodic domain, thus departing from the predictions of the theory that assumes spatial homogeneity and isotropy.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 1108-1115 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experiment to measure the properties of the collisions between two small spheres or between a small sphere and a semi-infinite flat wall are described. The apparatus releases the particles in a free-fall without initial spin. The impacts are modeled in terms of three coefficients. The first is the coefficient of normal restitution. The second represents the frictional properties of the contact surfaces. The last characterizes the restitution of the tangential components of the velocity of the contact point for impacts that do not involve sliding. The coefficients are calculated from stroboscopic photographs of the ballistics of the particles near the collision. The results establish that the collision model provides an accurate description of the dynamics of the impacts.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 2253-2269 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper employs computer simulations to test the theory of Jenkins [J. Applied Mech. 59, 120 (1992)] for the interaction between a rapid granular flow of spheres and a flat, frictional wall. This paper examines the boundary conditions that relate the shear stress and energy flux at the wall to the normal stress, slip velocity, and fluctuation energy, and to the parameters that characterize a collision. It is found that while the theory captures the trends of the boundary conditions at low friction, it does not anticipate their behavior at large friction. A critical evaluation of Jenkins' assumptions suggests where his theory may be improved.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 231-250 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of cyanogen and nitrous oxide diluted in argon were shock-heated to measure the rate constants of A broad-band mercury lamp was used to measure CN in absorption at 388 nm [B2Σ+(v = 0) ← X2Σ+(v = 0)], and the spectral coincidence of a CO infrared absorption line [v(2 ← 1), J(37 ← 38)] with a CO laser line [v(6 → 5), J(15 → 16)] was exploited to monitor CO in absorption. The CO measurement established that reaction (3) produces CO in excited vibrational states. A computer fit of the experiments near 2000 K led to \documentclass{article}\pagestyle{empty}\begin{document}$$ k_2 \, = \,10^{11.70\left( { + 0.25, - 0.19} \right)} \,{{{\rm cm}^3 } \mathord{\left/ {\vphantom {{{\rm cm}^3 } {{\rm mol}}}} \right. \kern-\nulldelimiterspace} {{\rm mol}}}\, \cdot \,{\rm s} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \, = \,10^{13.26 \pm 0.26} \,{{{\rm cm}^3 } \mathord{\left/ {\vphantom {{{\rm cm}^3 } {{\rm mol}}}} \right. \kern-\nulldelimiterspace} {{\rm mol}}}\, \cdot \,{\rm s} $$\end{document} An additional measurement of NO via infrared absorption led to an estimate of the ratio k5/k6: with k5/k6 ≃ 103.36±0.27 at 2150 K. Mixtures of cyanogen and oxygen diluted in argon were shock heated to measure the rate constant of and the ratio k5/k6 by monitoring CN in absorption. We found near 2400 K: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_4 \, = \,10^{12.68\left( { + 0.27, - 0.19} \right)} \,{{{\rm cm}^3 } \mathord{\left/ {\vphantom {{{\rm cm}^3 } {{\rm mol}}}} \right. \kern-\nulldelimiterspace} {{\rm mol}}}\, \cdot \,{\rm s} $$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$$ {{k_5 } \mathord{\left/ {\vphantom {{k_5 } {k_6 }}} \right. \kern-\nulldelimiterspace} {k_6 }}\, = \,10^{2.68 \pm 0.28} $$\end{document} The combined measurements of k5/k6 lead to k5/k6 ≃ 10-3.07 exp(+31,800/T) (±60%) for 2150 ≤ T ≤ 2400 K.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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