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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 32 (2000), S. 165-202 
    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
    Notes: Abstract This article reviews some aspects of the roles that laboratory experiments have played in the study of orographic effects in the Earth's atmosphere and oceans. The review focuses on, but is not restricted to, physical systems for which the effects of both background stratification and rotation are important. In the past, such laboratory studies have been largely decoupled from attempts to make quantitative comparisons with the results of numerical-model studies or observations from field programs. Rather, they have been used mostly in the important task of better understanding the physics of rotating and stratified flows. Furthermore, most laboratory experiments concerned with the effects of orography on either homogeneous or stratified rotating fluids have considered laminar flows, whereas their counterpart flows in the atmosphere and ocean are turbulent. We argue that laboratory investigations are likely to be more useful in addressing critical environmental problems if the studies are more closely allied with numerical-modeling efforts. The latter, in turn, should be tied to field projects, with the overall objective of improving our ability to predict the behavior of natural systems. In this same spirit, we conclude that far more attention should be given to the laboratory simulation of the turbulent characteristics of natural flows. The availability of rapidly developing technology to acquire and analyze laboratory data provides the capability necessary to support the increasingly important roles that laboratory experiments can play in understanding and predicting the behavior of our natural environment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 239-252 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The flow past a horizontally translating, streamwise oscillating sphere through a linearly stratified fluid is investigated in a series of laboratory experiments. The pertinent governing parameters are shown to be the internal Froude number Fi, the Reynolds number Re, the Keulegan–Carpenter number KC, and the normalized forcing frequency Sf. A KC against Sf regime diagram for flows at Fi=0.07 and Re=190 is developed; for these parameters the flow is approximately two dimensional in the horizontal zone, −1/2(approximately-less-than)z/D(approximately-less-than)1/2, where z is the vertical coordinate and D is the sphere diameter. Numerous flow regimes are delineated, and it is shown that the regime boundaries approximate the lines of constant u1/u0=2π(KC)(Sf), where u1 is the amplitude of the sphere oscillation and u0 is the magnitude of the mean background flow. Vortex shedding occurs for the entire range of experiments at these Fi, Re values. Lock-on of the shedding frequency to the sphere oscillation frequency occurs for u1/u0(approximately-greater-than)0.1. Flows at large Fi are shown to exhibit three-dimensional motions in the near wake, and, owing to stratification, exhibit vertical collapse at a certain distance downstream. The far wake develops into a horizontal vortex street pattern for all flows when stratification is present. At large Fi, Re combinations, turbulent patches are found in the wake. The inverse normalized streamwise distance between shed vortices (an effective Strouhal number) is shown to scale as Sf, independent of KC. Measurements of the horizontal separation angles and times for the collapse of the vertical structure are also presented.
    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 5 (1993), S. 868-880 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The flow of a homogeneous, incompressible, rotating fluid past a vertical circular cylinder oscillating laterally in a uniform free stream is investigated experimentally. An a/D against λ/D flow regime diagram is developed under conditions of fixed Ekman number, E=3.6(10)−4 and cylinder aspect ratio H/D=1.0; here a is the amplitude of the cross-stream oscillation, D is the cylinder diameter, λ is the streamwise wavelength of the oscillation, and H is the fluid depth (cylinder height). Six distinct characteristic flow types are identified, including fully attached flow, eddy shedding for pure oscillatory motion (i.e., a zero free-stream current), double eddy structures, vortex shedding/merging, eddy chains, and irregular eddy shedding. For comparison purposes, experiments are also conducted in the same ranges of a/D and λ/D for nonrotating flows. The effects of rotation are found to be most important for the smaller values of a/D and λ/D. Rotation tends to induce rectified anticyclonic currents (i.e., in a direction opposite to the background rotation) near the cylinder boundary. Rotation also has the tendency to destroy the cross-streamwise centerline symmetry characteristic of nonrotating flows. Numerous flow observables are measured and, where possible, compared with scaling analyses.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 115-126 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A horizontal jet emerging continuously from a small round nozzle (concentrated source of momentum) in a rotaing stratified fluid is investigated using laboratory experiments. The jet either (i) deflects from the direction of injection, forming an anticyclonic spiral monopole (monopole regime), or (ii) propagates along the injection direction, forming a dipolar structure (dipole regime). Which of these characteristic flows occurs depends on the system parameters, the Reynolds number Re, and the buoyancy frequency to Coriolis parameter ratio N/f; a flow regime diagram is developed for the parameter ranges 40(approximately-less-than) Re(approximately-less-than)200 and 0(approximately-less-than)N/f(approximately-less-than)35, respectively. A theoretical analysis is advanced to explain the conditions under which the monopole and dipole regimes occur, including the transition curve between the two regimes. The theory is supported by laboratory experiments. Some geophysical examples of the considered flows are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 2243-2255 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laboratory measurements were carried out to investigate the evolution of a turbulent wake behind a right circular cylinder moving in a linearly stratified fluid. The flow field is mainly determined by the internal Froude number Fi and the Reynolds number Re, but at high Re, Fi becomes the only governing parameter. Measurements show that stratified turbulent wakes can be classified into three flow regimes, based on Fi. When Fi〈2, the wakes do not grow downstream, and remain at an approximately constant height. For 2〈Fi〈3, the wakes grow to a maximum height at Nt≈5 and then collapse physically; for Fi(approximately-greater-than)3, the maximum height is achieved at Nt≈2.5, before the collapse begins. The evolution of such other length scales as the Ozmidov, Kolmogorov, overturning, and Thorpe scales and the maximum Thorpe displacements was measured, and their behavior in the above Fi ranges was delineated. Length scale diagrams for the evolution of stratified turbulence in cylinder wakes were constructed and compared with previous theoretical predictions. The present results provide new insights into the evolution, collapse, and long-term evolution of stratified turbulent flows. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 1440-1453 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The motion field resulting from an oscillatory, rotating flow parallel to a vertical wall and bounded from below by a horizontal plane along which there is no slip and from above by a horizontal frictionless lid is investigated numerically by using primitive equations. The model is barotropic and forced by oscillatory, spatially uniform, along-wall, and lateral pressure gradients. The pertinent parameters are the Rossby, temporal Rossby, and Ekman numbers. By means of simulated particle tracking, including a statistical analysis, and a consideration of momentum balances, the physical mechanisms leading to flow rectification are identified; i.e., the exchange of along-wall momentum of fluid parcels communicating between the bottom Ekman layer, the vertical shear layer, and the fluid interior. A rectified flow is generated along the wall for all subinertial, inertial, and superinertial oscillation frequencies investigated. The direction of the rectified current is such that the sidewall is on the right, facing downstream, for a vertically upward or Northern Hemisphere rotation. The mean transports and widths of the rectified currents are determined as functions of the appropriate system parameters. The current width is much larger than the classical E1/4 Stewartson layer thickness. The numerical results are in good agreement with recent laboratory experiments.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2008-10-29
    Print ISSN: 1567-7419
    Electronic ISSN: 1573-1510
    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
    Published by Springer
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  • 8
    Publication Date: 1993-04-01
    Print ISSN: 0899-8213
    Topics: Physics
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  • 9
    Publication Date: 1994-01-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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  • 10
    Publication Date: 1997-01-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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