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  • 1
    Electronic Resource
    Electronic Resource
    LONG NONLINEAR INTERNAL WAVES (2006)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 38 (2006), S. 395-425 
    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
    Notes: Over the past four decades, the combination of in situ and remote sensing observations has demonstrated that long nonlinear internal solitary-like waves are ubiquitous features of coastal oceans. The following provides an overview of the properties of steady internal solitary waves and the transient processes of wave generation and evolution, primarily from the point of view of weakly nonlinear theory, of which the Korteweg-de Vries equation is the most frequently used example. However, the oceanographically important processes of wave instability and breaking, generally inaccessible with these models, are also discussed. Furthermore, observations often show strongly nonlinear waves whose properties can only be explained with fully nonlinear models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fluid.38.050304.092129
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Wave transport of deep mantle material (1988)
    [s.l.] : Nature Publishing Group
    Nature 336 (1988), S. 59-61 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Streamlines of a solitary wave calculated in the frame moving with the solitary wave speed c for the case s = 9. Radius r is normalized by the radius of the conduit and the conduit axial dimension z is normalized by a natural length scale of the problem3. Note the large region of closed ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/336059a0
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  • 3
    Electronic Resource
    Electronic Resource
    Flow localization in fissure eruptions (1999)
    Springer
    Bulletin of volcanology 60 (1999), S. 432-440 
    Details
    ISSN: 1432-0819
    Keywords: Key words Fissure eruption ; Flow localization ; Temperature-dependent viscosity ; Solidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  During a basaltic fissure eruption heat transfer from the hot magma to the surrounding rock causes a dramatic increase in the magmatic viscosity and solidification at the margins. Both viscosity contrast and solidification can amplify initial variations in the flow rate and lead to localization of the flow along the strike of the fissure. However, for typical parameters, amplification driven by solidification is slower and significantly weaker than amplification driven by viscosity variations. In fact, for the parameters examined, the amplification due to solidification is so weak that its effect is almost insignificant, whereas viscosity variation provides a strong active mechanism for flow localization. Laboratory experiments illustrate viscous localization and suggest that this mechanism is robust. The dependence of viscosity on temperature can cause a small change in the pressure of the magma chamber to lead to a large jump in the flow rate of magma through the fissure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050243
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  • 4
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    Decay and return of internal solitary waves with rotation (2007)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author, 2007. This is the author's version of the work. It is posted here by permission of American Institute of Physics for personal use, not for redistribution. The definitive version was published in Physics of Fluids 19 (2007): 026601, doi:10.1063/1.2472509.
    Description: The effect of rotation on the propagation of internal solitary waves is examined. Wave evolution is followed using a new rotating extension of a fully-nonlinear, weakly nonhydrostatic theory for waves in a two-layer system. When a solitary wave solution of the non-rotating equations is used as the initial condition the wave initially decays by radiation of longer inertia-gravity waves. The radiated inertia-gravity wave always steepens, leading to the formation a secondary solitary-like wave. This decay and re-emergence process then repeats. Eventually a nearly localized wavepacket emerges. It consists of a longwave envelope and shorter, faster solitary-like waves that propagate through the envelope. The radiation from this mature state is very weak, leading to a robust, long-lived structure that may contain as much as 50% of the energy in the initial solitary wave. Interacting packets may either pass through one another, or merge to form a longer packet. The packets appear to be modulated, fully-nonlinear versions of the steadily translating quasi-cnoidal waves.
    Description: This work was supported by a Woods Hole Oceanographic Institution Mellon Independent Study Award and ONR Grant N000140610798.
    Keywords: Nonlinear internal waves ; Solitary waves ; Rotation
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 5
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    On the stability of ocean overflows (2009)
    Cambridge University Press
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Cambridge University Press, 2008. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of Fluid Mechanics 602 (2008): 241-266, doi:10.1017/S0022112008000827.
    Description: The stability of a hydraulically driven sill flow in a rotating channel with smoothly varying cross-section is considered. The smooth topography forces the thickness of the moving layer to vanish at its two edges. The basic flow is assumed to have zero potential vorticity, as is the case in elementary models of the hydraulic behaviour of deep ocean straits. Such flows are found to always satisfy Ripa's necessary condition for instability. Direct calculation of the linear growth rates and numerical simulation of finite-amplitude behaviour suggests that the flows are, in fact, always unstable. The growth rates and nonlinear evolution depend largely on the dimensionless channel curvature κ=2αg′/f2, where 2α is the dimensional curvature, g′ is the reduced gravity, and f is the Coriolis parameter. Very small positive (or negative) values of κ correspond to dynamically wide channels and are associated with strong instability and the breakup of the basic flow into a train of eddies. For moderate or large values of κ, the instability widens the flow and increases its potential vorticity but does not destroy its character as a coherent stream. Ripa's condition for stability suggests a theory for the final width and potential vorticity that works moderately well. The observed and predicted growth in these quantities are minimal for κ≥1, suggesting that the zero-potential-vorticity approximation holds when the channel is narrower than a Rossby radius based on the initial maximum depth. The instability results from a resonant interaction between two waves trapped on opposite edges of the stream. Interactions can occur between two Kelvin-like frontal waves, between two inertia–gravity waves, or between one wave of each type. The growing disturbance has zero energy and extracts zero energy from the mean. At the same time, there is an overall conversion of kinetic energy to potential energy for κ〉0, with the reverse occurring for κ〈0. When it acts on a hydraulically controlled basic state, the instability tends to eliminate the band of counterflow that is predicted by hydraulic theory and that confounds hydraulic-based estimates of volume fluxes in the field. Eddy generation downstream of the controlling sill occurs if the downstream value of κ is sufficiently small.
    Description: This work was supported by the National Science Foundation (Grant OCE- 0525729).
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Mixing at the head of a canyon : a laboratory investigation of fluid exchanges in a rotating, stratified basin (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C12004, doi:10.1029/2006JC003667.
    Description: Observations indicate that oceanic mixing is intensified near the head of submarine canyons. How the presence of canyon walls affects the local production and distribution of mixed fluid is an open question. These dynamics are addressed through rotating tank experiments which impose mixing at middepth at the closed end of a channel open to a larger body of water. Turbulence is generated in a linearly stratified fluid with initial buoyancy frequency N by means of a single bar oscillated with frequency ω. The mixed fluid quickly reaches a steady state height h ∼ (ω/N)1/2 independent of the Coriolis frequency f and collapses into the channel interior. A small percentage of the fluid exported from the turbulent zone enters a boundary current. The bulk forms a cyclonic circulation in front of the bar. As the recirculation cell expands to fill the channel, it restricts horizontal entrainment into the turbulent zone. Mixed fluid flux decays with time as t inline equation and is dependent on the size of the mixing zone and the balance between turbulence, rotation, and stratification. The recirculation cell is confined within the channel, and export of mixed fluid into the basin is restricted to the weak boundary current. As horizontal entrainment is shut down, long-term production of mixed fluid relies more on vertical entrainment. However, the scalings indicate that short-term dynamics are the most applicable to oceanic conditions.
    Description: This work was supported by the Ocean Ventures Fund, the Westcott Fund, and the WHOI Academic Programs Office. Financial support was also provided by the National Science Foundation through grant OCE-9616949.
    Keywords: Mixing ; Canyon ; Laboratory
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Strongly nonlinear, simple internal waves in continuously-stratified, shallow fluids (2011)
    Copernicus Publications on behalf of the European Geosciences Union and the American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Nonlinear Processes in Geophysics 18 (2011): 91-102, doi:10.5194/npg-18-91-2011.
    Description: Strongly nonlinear internal waves in a layer with arbitrary stratification are considered in the hydrostatic approximation. It is shown that "simple waves" having a variable vertical structure can emerge from a wide class of initial conditions. The equations describing such waves have been obtained using the isopycnal coordinate as a variable. Emergence of simple waves from an initial Gaussian impulse is numerically investigated for different density profiles, from two- and three-layer structure to the continuous one. Besides the first mode, examples of second- and third-mode simple waves are given.
    Description: KRH is supported by the Office of Naval Research IWISE Program grant N00014-09-1-0227.
    Repository Name: Woods Hole Open Access Server
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  • 8
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    Upward swimming of competent oyster larvae Crassostrea virginica persists in highly turbulent flow as detected by PIV flow subtraction (2013)
    Inter-Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Inter-Research, 2013. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 488 (2013): 171-185, doi:10.3354/meps10382.
    Description: Investigating settlement responses in the transitory period between planktonic and benthic stages of invertebrates helps shape our understanding of larval dispersal and supply, as well as early adult survival. Turbulence is a physical cue that has been shown to induce sinking and potentially settlement responses in mollusc larvae. In this study, we determined the effect of turbulence on vertical swimming velocity and diving responses in competent eastern oyster larvae Crassostrea virginica. We quantified the behavioural responses of larvae in a moving flow field by measuring and analyzing larval velocities in a relative framework (where local flow is subtracted away, isolating the behavioural component) in contrast to the more common absolute framework (in which behaviour and advection by the flow are conflated). We achieved this separation by simultaneously and separately tracking individuals and measuring the flow field around them using particle image velocimetry in a grid-stirred turbulence tank. Contrary to our expectations, larvae swam upward even in highly turbulent flow, and the dive response became less frequent. These observations suggest that oyster larvae are stronger swimmers than previously expected and provide evidence that turbulence alone may not always be a sufficient cue for settlement out of the water column. Furthermore, at a population level, absolute velocity distributions differed significantly from isolated larval swimming velocities, a result that held over increasing turbulence levels. The absolute velocity distributions indicated a strong downward swimming or sinking response at high turbulence levels, but this observation was in fact due to downwelling mean flows in the tank within the imaging area. Our results suggest that reliable characterization of larval behaviour in turbulent conditions requires the subtraction of local flow at an individual level, imposing the technical constraint of simultaneous flow and behavioural observations.
    Description: This work was supported by NSF grant OCE-0850419, grants from WHOI Coastal Ocean Institute, discretionary WHOI funds to purchase the infrared laser and high-speed camera, and a WHOI Ocean Life Fellowship to L.S.M.
    Keywords: Turbulence ; Crassostrea virginica ; Settlement ; Larval behaviour ; Particle image velocimetry
    Repository Name: Woods Hole Open Access Server
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  • 9
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    Laboratory experiments and simulations for solitary internal waves with trapped cores (2014)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of Fluid Mechanics 757 (2014): 354-380, doi:10.1017/jfm.2014.501.
    Description: We perform simultaneous coplanar measurements of velocity and density in solitary internal waves with trapped cores, as well as viscous numerical simulations. Our set-up comprises a thin stratified layer (approximately 15 % of the overall fluid depth) overlaying a deep homogeneous layer. We consider waves propagating near a free surface, as well as near a rigid no-slip lid. In the free-surface case, all trapped-core waves exhibit a strong shear instability. We propose that Marangoni effects are responsible for this instability, and use our velocity measurements to perform quantitative calculations supporting this hypothesis. These surface-tension effects appear to be difficult to avoid at the experimental scale. By contrast, our experiments with a no-slip lid yield robust waves with large cores. In order to consider larger-amplitude waves, we complement our experiments with viscous numerical simulations, employing a longer virtual tank. Where overlap exists, our experiments and simulations are in good agreement. In order to provide a robust definition of the trapped core, we propose bounding it as a Lagrangian coherent structure (instead of using a closed streamline, as has been done traditionally). This construction is less sensitive to small errors in the velocity field, and to small three-dimensional effects. In order to retain only flows near equilibrium, we introduce a steadiness criterion, based on the rate of change of the density in the core. We use this criterion to successfully select within our experiments and simulations a family of quasi-steady robust flows that exhibit good collapse in their properties. The core circulation is small (at most, around 10 % of the baroclinic wave circulation). The core density is essentially uniform; the standard deviation of the density, in the core region, is less than 4 % of the full density range. We also calculate the circulation, kinetic energy and available potential energy of these waves. We find that these results are consistent with predictions from Dubreil-Jacotin–Long theory for waves with a uniform-density irrotational core, except for an offset, which we suggest is associated with viscous effects. Finally, by computing Richardson-number fields, and performing a temporal stability analysis based on the Taylor–Goldstein equation, we show that our results are consistent with empirical stability criteria in the literature.
    Description: Funding from NSF grant OCE-1029672 is gratefully acknowledged. P.L.F. is thankful for support from the Postdoctoral Scholar program at the Woods Hole Oceanographic Institution, and for funding from the Devonshire Foundation.
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 10
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    Light stimulates swimming behavior of larval eastern oysters Crassostrea virginica in turbulent flow (2017)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 571 (2017): 109-120, doi:10.3354/meps12106.
    Description: Planktonic larvae of the eastern oyster Crassostrea virginica are able to regulate their vertical position in the water, but the environmental cues responsible for this regulation, particularly in turbulent settings, remain unclear. We quantified swimming responses of late-stage oyster larvae in a grid-stirred turbulence tank to determine how light affects the swimming behavior of larvae over a range of hydrodynamic conditions similar to their natural coastal environments. We used particle image velocimetry and larval tracking to isolate larval swimming from local flow and to quantify 3 behavioral metrics: vertical swimming direction, proportion of larvae diving, and proportion of larvae swimming helically. We compared these metrics across turbulence levels ranging from still water (ε = 0 cm2 s-3) to estuarine-like conditions (ε = 0.4 cm2 s-3) in light and dark. At all turbulence levels, light had no effect on the proportion of upward swimming larvae, but elicited detectable increases in the proportion of helical swimming and diving behaviors. We further examined the effect of light and turbulence on specific characteristics of helical trajectories, and found that these environmental cues induce changes to both vertical and horizontal velocities of helically swimming larvae, changing the helix geometry. The increased prevalence of these behaviors in light likely plays an ecological role: increased diving in light (in conjunction with turbulence) is a potential mechanism to enhance settlement success, while changes to helical swimming in light may serve an anti-predatory function. Together, these behaviors provide insight into potentially complex larval responses to multiple simultaneous environmental cues.
    Description: Funding was provided by NSF grant OCE-0850419, NOAA Sea Grant NA14OAR4170074, grants from WHOI Coastal Ocean Institute, discretionary WHOI funds, a WHOI Ocean Life Fellowship to LM, a Grove City College Swezey Fund Grant to EA, and a WHOI Summer Student Fellowship to EL.
    Keywords: Larval invertebrate ecology ; Larval swimming ; Environmental cues ; Hydrodynamics
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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