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  • 1
    Electronic Resource
    Electronic Resource
    Stably stratified turbulent channel flows. I. Stratification regimes and turbulence suppression mechanism (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 2569-2594 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Our objective in this study is to study inhomogeneous stratified shear flows using large eddy simulation; stratified pressure-gradient-driven channel flow was selected. The flows can be separated into three regimes: buoyancy affected, buoyancy controlled, and buoyancy dominated flows. The regime boundaries are defined by Richardson and Reynolds numbers based on the friction velocity. Buoyancy affected flows remain actively turbulent and attain a statistical steady state that resembles a lower Reynolds number unstratified flow. Flows in the buoyancy controlled regime are not in equilibrium. In the cases studied, an asymmetry develops with respect to the channel centerline leading to one-sided turbulence. Eventually, the "inactive" half undergoes a transition initiated by the active half and symmetry is restored. At higher Richardson numbers, the flows are buoyancy dominated, the near-wall burst-sweep process is completely disrupted and turbulence production ceases, leading to relaminarization. In relaminarizing flows, the inner and outer regions behave nearly independently. While the inner region turbulence decays monotonically, large-scale restratification, internal waves, and potential energy-driven motions are observed in the outer region. The simulation results are used to construct a physical model of stratified wall-bounded flows. Stable stratification weakens the interaction between the inner and outer regions by decreasing the vertical transport, leading to near-decoupling of the two layers at strong enough stratification. The notion that the disappearance of the log region marks the onset of buoyancy control provides a criterion for estimating the Richardson number delineating the transition from buoyancy affected to buoyancy controlled flows. Data that should be useful for creating parametrizations for prediction of stratified flows are also presented. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288608
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Hybrid spectral finite difference simulations of stratified turbulent flows on distributed memory architectures (1997)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 1129-1158 
    Details
    ISSN: 0271-2091
    Keywords: spectral finite difference ; direct numerical simulation ; message-passing computers ; data partitioning ; fractional step methods ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A method for efficient implementation of a combined spectral finite difference algorithm for computation of incompressible stratified turbulent flows on distributed memory computers is presented. The solution technique is the fractional step method with a semi-implicit time advancement scheme. A single-programme multiple-data abstraction is used in conjunction with a static data-partitioning scheme. The distributed FFTs required in the explicit step are based on the transpose method and the large sets of independent tridiagonal systems of equations arising in the implicit steps are solved using the pipelined Thomas algorithm. A speed-up analysis of a model problem is presented for three partitioning schemes, namely unipartition, multipartition and transpose partition. It is shown that the unipartitioning scheme is best suited for this algorithm. Performance measurements of the overall as well as individual stages of the algorithm are presented for several different grids and are discussed in the context of associated dependency and communication overheads. An unscaled speed-up efficiency of up to 91% on doubling the number of processors and up to 60% on an eightfold increase in the number of processors was obtained on the Intel Paragon and iPSC/860 Hypercube. Absolute performance of the code was evaluated by comparisons with performance on the Cray-YMP. On 128 Paragon processors, performance up to five times that of a single-processor Cray-YMP was obtained. The validation of the method and results of grid refinement studies in stably stratified turbulent channel flows are presented. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 3
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    Seawater carbonate chemistry and fertilization success of red abalone (2017)
    PANGAEA
    In:  Supplement to: Boch, Charles A; Litvin, Steven Y; Micheli, Fiorenza; De Leo, Giulio; Aalto, Emil A; Lovera, Christopher; Woodson, C Brock; Monismith, Stephen; Barry, J P (2017): Effects of current and future coastal upwelling conditions on the fertilization success of the red abalone (Haliotis rufescens). ICES Journal of Marine Science, https://doi.org/10.1093/icesjms/fsx017
    Details
    Publication Date: 2024-03-15
    Description: Acidification, deoxygenation, and warming are escalating changes in coastal waters throughout the world ocean, with potentially severe consequences for marine life and ocean-based economies. To examine the influence of these oceanographic changes on a key biological process, we measured the effects of current and expected future conditions in the California Current Large Marine Ecosystem on the fertilization success of the red abalone (Haliotis rufescens). Laboratory experiments were used to assess abalone fertilization success during simultaneous exposure to various levels of seawater pH (gradient from 7.95 to 7.2), dissolved oxygen (DO) (60 and 180 µm/kg SW) and temperature (9, 13, and 18 °C). Fertilization success declined continuously with decreasing pH but dropped precipitously below a threshold near pH 7.55 in cool (9 °C upwelling) to average (13 °C) seawater temperatures. Variation in DO had a negligible effect on fertilization. In contrast, warmer waters (18 °C) often associated with El Nino Southern Oscillation conditions in central California acted antagonistically with decreasing pH, largely reducing the strong negative influence below the pH threshold. Experimental approaches that examine the interactive effects of multiple environmental drivers and also strive to characterize the functional response of organisms along gradients in environmental change are becoming increasingly important in advancing our understanding of the real-world consequences of changing ocean conditions.
    Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Animalia; Aragonite saturation state; Benthic animals; Benthos; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Comment; Date; Eggs; Eggs, abnormal; Eggs, four-cell stage; Eggs, two-cell stage; Eggs, unfertilized; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Haliotis rufescens; Individuals; Laboratory experiment; Mollusca; Name; North Pacific; OA-ICC; Ocean Acidification International Coordination Centre; Oxygen; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Potentiometric; Registration number of species; Reproduction; Salinity; Sample ID; Single species; Species; Temperate; Temperature; Temperature, water; Time in hours; Time in minutes; Time in seconds; Treatment; Type; Uniform resource locator/link to reference
    Type: Dataset
    Format: text/tab-separated-values, 9002 data points
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    DATA PANGAEA
  • 4
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    Laboratory experiments of fine-scale mixing and mass transport within a coral canopy (2007)
    American Institute of Physics
    Details
    Publication Date: 2007-07-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics
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  • 5
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    A field investigation into the effects of a kelp forest (Macrocystis pyrifera) on coastal hydrodynamics and transport (2007)
    American Geophysical Union
    Details
    Publication Date: 2007-02-16
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 6
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    Spectral wave flow attenuation within submerged canopies: Implications for wave energy dissipation (2007)
    American Geophysical Union
    Details
    Publication Date: 2007-05-11
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 7
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    Transport Between Palau and the Eastern Coral Triangle: Larval Connectivity or Near Misses (2018)
    American Geophysical Union
    Details
    Publication Date: 2018-05-23
    Description: Physical connectivity by transport of larvae between different habitats plays a fundamental role in marine population dynamics and is often assessed using circulation models assuming that computed large-scale connectivity describes the actual connectivity. This paper presents observations of drifters released into the Philippine Sea offshore of the western lagoon of Palau that were tracked as were first carried by the Mindanao Eddy toward Mindanao and other parts of the Celebes and Sulu Seas, where they were removed from the water. While following expected transport pathways for this region, our drifters remained at least several kilometers offshore of the various islands they passed by, suggesting that larvae moving similarly would have been too far offshore to recruit to nearshore reefs. Thus, estimates of connectivity made using large-scale models must be taken as upper bounds to connectivity across ocean basins. ©2018. American Geophysical Union. All Rights Reserved.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 8
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    Three-Dimensional Modeling of Fine Sediment Transport by Waves and Currents in a Shallow Estuary (2018)
    American Geophysical Union
    Details
    Publication Date: 2018-05-06
    Print ISSN: 2169-9275
    Electronic ISSN: 2169-9291
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 9
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    Mixing Efficiency in the Presence of Stratification: When Is It Constant? (2018)
    American Geophysical Union
    Details
    Publication Date: 2018-06-14
    Description: The efficiency of the conversion of mechanical to potential energy, often expressed as the flux Richardson number, Rif, is an important determinant of vertical mixing in the ocean. To examine the dependence of Rif on the buoyancy Reynolds number, ReB, we analyze three sets of data: microstructure profiler data for which mixing is inferred from rates of dissipation of turbulent kinetic energy (ε) and temperature variance (χ) measured in the open ocean, time series of spectrally fit values of ε and covariance-derived buoyancy fluxes measured in nearshore internal waves, and time series of spectrally fit values of ε and χ measured in an energetic estuarine flow. While profiler data are well represented by Rif ≈ 0.2 for 1 〈 ReB 〈 1,000, the covariance data have much larger values of ReB and, consistent with direct numerical simulation results, show that Rif ~ ReB −0.5. The estuarine data have values of ReB that fall between those of the other two data sets but also shows Rif ≈ 0.2 for ReB 〈 5000. Overall, these data suggest that Rif is in general not constant and may be substantially less than 0.2 when ReB is large, although the value at which the transition from constant to ReB-dependent mixing may depend on additional parameters that are yet to be determined. Nonetheless, for much of the ocean, ReB 〈 100 and so Rif is constant there. ©2018. American Geophysical Union. All Rights Reserved.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 10
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    Temporal Variability in Thermally Driven Cross-Shore Exchange: The Role of Semidiurnal Tides (2018)
    American Meteorological Society
    Details
    Publication Date: 2018-07-01
    Description: We examine temporal variability of thermally driven baroclinic cross-shore exchange in the context of a tropical fringing reef system focusing on the role of tidally driven alongshore flow. Ensemble diurnal phase averaging of cross-shore flow at the Kilo Nalu Observatory (KNO) in Oahu, Hawaii, shows a robust diurnal signal associated with an unsteady buoyancy/diffusive dynamic balance, although significant variability is observed at subdiurnal time scales. In particular, persistent fortnightly variability in the cross-shore diurnal flow pattern is consistent with modulation by the semidiurnal alongshore tidal flow. The alongshore flow plays a direct role in the cross-shore exchange momentum balance via Coriolis acceleration but also affects the cross-shore circulation indirectly via its influence on vertical turbulent diffusion. An idealized linear theoretical model for thermally driven cross-shore flow is formulated using the long-term time-averaged diurnal dynamic balance at KNO as a baseline. The model is driven at leading order by the surface heat flux, with contributions from the alongshore flow and cross-shore wind appearing as linear perturbations. Superposition of the idealized solutions for Coriolis and time-varying eddy viscosity perturbations are able to reproduce key aspects of the fortnightly variability. Modifying the model to consider a more realistic alongshore flow and considering effects of nightly convection lead to further improvements in comparisons with KNO observations. The ability of the theoretical approach to reproduce the fortnightly patterns indicates that semidiurnal variations in the alongshore flow are effective in modulating the cross-shore flow via Coriolis and vertical turbulent transport mechanisms.
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
    Published by American Meteorological Society
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