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  • 1
    Electronic Resource
    Electronic Resource
    Turbulent Mixing in Stratified Fluids (1991)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 23 (1991), S. 455-493 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fl.23.010191.002323
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  • 2
    Electronic Resource
    Electronic Resource
    Note on secondary flows in oscillating-grid, mixing-box experiments (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1849-1851 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oscillating-grid induced turbulence in confined geometries (tanks) is commonly used in the study of turbulence with zero-mean shear. It is demonstrated that the mean secondary circulation generated during such experiments can be reduced by selecting conditions that lessen the Reynolds-stress gradients within the fluid. A simple power law for the spatial decay of turbulent velocity fluctuations is realized only in the absence of such mean circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858808
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  • 3
    Electronic Resource
    Electronic Resource
    Turbulent wakes of linearly stratified flow past a sphere (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1687-1696 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental observations and associated scaling analyses are presented for the flow of a linearly stratified fluid past a sphere for conditions under which the wake is fully turbulent. It is shown that for internal Froude numbers Fi(approximately-less-than)2, the turbulent wake is suppressed by stratification in the immediate lee of the sphere. For Fi(approximately-greater-than)2, the normalized thickness δT/D grows as t1/3 before the wake height reaches its maximum (which takes place at Nt≈2.0), much the same as for wakes of spheres in homogeneous flow; here D is the sphere diameter, N is the buoyancy frequency, and t is the time. The normalized horizontal wake dimension γT/D, on the other hand, grows in the near wake as t1/3 for all Fi but, for Nt(approximately-greater-than)2.0, grows somewhat more rapidly as t1/2. The Strouhal number for the far-wake vortex street is measured and shown to be roughly a constant St≈0.18, independent of the Reynolds and Froude numbers. It is suggested that the frequency of the far-wake, quasi-two-dimensional vortices is established by the eddy shedding frequency of the near wake and thus is independent of stratification effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858389
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  • 4
    Electronic Resource
    Electronic Resource
    A numerical study on the formation of a thermocline in shear-free turbulence (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 422-426 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of a thermocline generated by the interaction between a stabilizing buoyancy flux and shear-free turbulence was studied using a numerical model. The time evolutions of the vertical distributions of the buoyancy and turbulent kinetic energy were calculated and were used to evaluate the depth of the thermocline and the time required for its formation. The numerical results are compared with the results of previous laboratory experiments. The mechanisms responsible for the formation of the thermocline are discussed in view of the numerical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858098
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  • 5
    Electronic Resource
    Electronic Resource
    Dispersion of suspended particles in turbulent flow (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1730-1740 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The upward dispersion of heavy particles in suspension in turbulent flow was studied using a numerical model. The interaction between the turbulence and the particle diffusion leads to the formation of a horizontal front (or a "lutocline''), across which the diffusion of particles and the propagation of turbulent energy are inhibited. However, as the settling velocity of the particles becomes larger, or as the particle concentration becomes smaller, the interaction weakens, thus suppressing the front formation. One-dimensional model equations for the problem are solved numerically to calculate the evolution of the particle concentration. A criterion for the formation of the front is proposed and the steady depth of the suspension layer is determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857952
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular-diffusive effects in penetrative convection (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1592-1596 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental study was performed to investigate the influence of molecular diffusion on turbulent entrainment during penetrative convection. The entrainment coefficient E was determined as a function of the Richardson number Ri and Peclet number Pe. It appears that, in parameter ranges 65〈Ri〈150 and 103〈Pe〈104, E is a function of Ri, independent of Pe, which indicates inertial-buoyancy dominated mixing and the unimportance of molecular diffusive effects. At high interfacial stabilities, 30〈Ri〈300, the entrainment law was found to be given by E∼Ri−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857566
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  • 7
    Electronic Resource
    Electronic Resource
    Propagation of grid turbulence in homogeneous fluids (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 2435-2440 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The purpose of this paper is to present the results of a laboratory experiment dealing with one-dimensional propagation of a turbulent front induced by an oscillating grid in a homogeneous fluid. The symmetrical quadrupolar mode of the flow, induced by the grid elements, was studied in the range KC=4–45, S=1–20 (KC is the Keulegan–Carpenter number, S is the Stokes number). It is shown that the depth H of the turbulent layer increases with time t as H∝t1/2. Experimental data for different grid parameters and oscillation amplitudes and frequencies are presented in the nondimensional form h=const τ1/2, using nondimensional depth h of the turbulent layer and nondimensional time τ. A semiempirical model is presented to explain this behavior. This model is based on the properties of a flow induced in a visous fluid by localized forcing of a line force dipole (force doublet). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869028
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  • 8
    Electronic Resource
    Electronic Resource
    Starting and steady quadrupolar flow (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 384-396 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Planar flow induced in a viscous fluid by a small cylinder oscillating in the direction normal to its axis is modeled theoretically and reproduced experimentally. In the model, a line force dipole (force doublet) was used as the source of motion. In an initially quiescent unbounded fluid this source produces zero net momentum and generates symmetrical quadrupolar flow consisting of two dipolar vorticity fronts propagating in opposite directions from the source. For starting flow at low Reynolds numbers, a second-order unsteady solution is obtained in terms of a power series of the Reynolds number, Re=Q/4πν2, where Q is the forcing amplitude and ν is the kinematic viscosity. This solution demonstrates that, as time t→∞, the flow in the vicinity of the source becomes steady and radial. To describe this steady asymptote, the Jeffery–Hamel nonlinear solution for radial flow is used. A particular solution is derived using the nondimensional intensity Re of the force dipole as a governing parameter. It is shown that the problem permits a similarity solution for all values of Re when a mass sink of prescribed intensity q=q(Re) is added to the flow. This steady asymptote is reproduced experimentally, using a vertical porous cylinder that oscillates horizontally in the shallow upper layer of a two-layer fluid and sucks fluid through its porous walls. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868792
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  • 9
    Electronic Resource
    Electronic Resource
    Experimental examination of Eulerian frequency spectra in zero-mean-shear turbulence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 1168-1170 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Eulerian frequency spectra were measured in zero-mean-shear (oscillating-grid induced) turbulent flows and were compared with the spectral form proposed by Tennekes [J. Fluid Mech. 67, 561 (1975)]. A satisfactory agreement between the theoretical prediction and experimental results were obtained in a limited frequency range. The empirical constants pertinent to the spectral law, obtained experimentally, were in good agreement with the numerical simulation results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868560
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  • 10
    Electronic Resource
    Electronic Resource
    The transition in the sedimentation pattern of a particle cloud (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3049-3055 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments were carried out to study the sedimentation of a two-dimensional particle cloud. When a large number of particles (glass beads) of uniform size are released from a two-dimensional opening into a column of fresh water, the mixture initially descends as a thermal; however, after some time, the particles start settling individually, thus leaving the parent fluid behind. For a given type of particle, the critical depth zc at which this transition occurs, measured from a virtual origin, was found to change as zcws/ν∼(Q/νws)α, with α(approximately-equal-to)0.3, where ws is the terminal velocity of a single particle, ν is the kinematic viscosity, and Q is the total buoyancy of the released particles per unit length. The descending velocity and the spatial growth of the particle cloud were found to depend on its sedimentation characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858715
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