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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 1581-1595 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dynamics of well-organized tube-like coherent structures under a free surface and turbulent scalar transfer across the free surface in fully developed turbulent flow in an open channel is investigated. A direct numerical simulation of the three-dimensional Navier–Stokes equations is used to obtain the structure of the free-surface turbulence. First, the effect of the free surface on fully developed turbulence statistics is described. Anisotropy of velocity and vorticity under the free surface are given. Next, the dynamics of the intermittent vortex tubes beneath the free surface are stated. The genesis and development of these coherent structures and their interactions with the free surface are demonstrated. The role of the vortex/surface interactions on the dynamics of turbulence under the free surface, particularly intercomponent energy transfer due to the pressure–strain effect, is discussed. In addition, passive scalar transfer across the free surface is studied. Finally, the promotion of turbulent scalar transfer at the free surface by the vortex/interface interactions is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Turbulence structure in an open-channel flow with a zero-shear gas–liquid interface was numerically investigated by a three-dimensional direct numerical simulation (DNS) based on a fifth-order finite-difference formulation, and the relationship between scalar transfer across a zero-shear gas–liquid interface and organized motion near the interface was discussed. The numerical predictions of turbulence quantities were also compared with the measurements by means of a two-color laser Doppler velocimeter. The results by the DNS show that the vertical motion is restrained in the interfacial region and there the turbulence energy is redistributed from the vertical direction to the streamwise and spanwise directions through the pressure fluctuation. The large-scale eddies are generated by bursting phenomena in the wall region and they are lifted up toward the interfacial region. Then, the eddies renew the interface and promote the scalar transfer across the gas–liquid interface. Both the damping effect and the generation process of the surface-renewal motions predicted by the DNS explain well the experimental results deduced in previously published studies. Furthermore, the predicted bursting frequency and mass transfer coefficient are in good agreement with the measurements.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Flow, turbulence and combustion 51 (1993), S. 423-427 
    ISSN: 1573-1987
    Keywords: heat and mass transfer ; gas-liquid interface ; organized motion ; wind-driven turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Turbulence structure and heat and mass transfer mechanism across a wavy sheared gas-liquid interface are fluid-mechanically investigated in a wind-wave tunnel. Heat and mass transfer velocities are reported and the relationship between the scalar transfer velocities and the turbulence structure is discussed. In addition, three-dimensional direct numerical simulation is carried out to investigate the flow structure over a rigid-wavy wall similar to that over the wave. The results show that the organized motion in the air flow intermittently appears on the front side of the wave crest, and its structure is rather similar to the flow structure over the rigid-wavy wall. The organized motion in the air flow induces the organized motion in the water flow and the organized motion renews the air-water interface. The scalar transfer across a wavy sheared gas-liquid interface is controlled by the organized surface-renewal motion in the water flow
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 957-960 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2393-2404 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Direct numerical simulations were used to investigate turbulence structure and scalar transfer across a shear-free, nonwavy gas-liquid interface (free surface) in stably stratified turbulent flows. These simulations solve the Navier-Stokes and thermal-energy conservation equations, using a finite difference approximation. The relation between the turbulence structure in the stably stratified turbulent boundary layer and organized motion near the free surface are discussed. In addition, scalar transfer across a free surface is investigated by solving a passive scalcr conservation equation after both velocity and temperature fields are fully developed. The effects of stable stratification on the scalar transfer process in a region very close to the free surface are also discussed.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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