A modified law‐of‐the‐wall applied to oceanic bottom boundary layers

Perlin, A.; Moum, James N.; Klymak, Jody M.; Levine, Murray D.; Boyd, T.; Kosro, P. Michael

doi:10.1029/2004jc002310

Cited by 99 publications

(104 citation statements)

References 19 publications

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“…This is probably due to the violation of assumptions underlying the law-of-the-wall parameterization (Li 1994;Smith and McLean 1977). In addition, the presence of stable stratification (e.g., Lien and Sanford 2004;Perlin et al 2005) and the details of bottom roughness and corresponding form drag (Li 1994;Sanford and Lien 1999;Edwards et al 2004) also contribute to the disparity. Lozovatsky et al (2008b) present further discussions on this issue with application to ECS shelf.…”

Section: Background Tidal Dynamics and Stratificationmentioning

confidence: 95%

“…It was found, however, that in the presence of weak stable stratification, velocity profile may exhibit a seemingly logarithmic structure, even though this log-layer may not support a constant vertical momentum flux, and u * so deduced can be much larger than the actual friction velocity. Specific modifications to u * obtained from shear profiles dU(ζ)/dζ have been suggested (e.g., Friedrichs and Wright 1997;Perlin et al 2005;Taylor and Sarkar 2008) to account for the influence of stratification. The u * deduced from the modified formulae was approximately half of its law-ofthe-wall-based counterpart.…”

Section: Introductionmentioning

confidence: 99%

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Shallow water tidal currents in close proximity to the seafloor and boundary-induced turbulence

et al. 2011

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Velocity measurements with vertical resolution 0.02 m were conducted in the lowest 0.5 m of the water column using acoustic Doppler current profiler (ADCP) at a test site in the western part of the East China Sea. The friction velocity u * and the turbulent kinetic energy dissipation rate ε wl (ζ) profiles were calculated using loglayer fits; ζ is the height above the bottom. During a semidiurnal tidal cycle, u * was found to vary in the range (1-7)Â10 −3 m/s. The law-of-the-wall dissipation profiles ε wl (ζ) were consistent with the dissipation profiles ε mc (ζ) evaluated using independent microstructure measurements of small-scale shear, except in the presence of westward currents. It was hypothesized that an isolated bathymetric rise (25 m height at a 50-m seafloor) located to the east of the measurement site is responsible for the latter. Calculation of the depth integrated internal tide generating body force in the region showed that the flanks of the rise are hotspots of internal wave energy that may locally produce a significant turbulent zone while emitting tidal and shorter nonlinear internal waves. This distant topographic source of turbulence may enhance the microstructure-based dissipation levels ε mc (ζ) in the bottom boundary layer (BBL) beyond the dissipation ε wl (ζ) associated with purely locally generated turbulence by skin currents. Semi-empirical estimates for dissipation at a distance from the bathymetric rise agree well with the BBL values of ε mc measured 15 km upslope.

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Section: Background Tidal Dynamics and Stratificationmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Shallow water tidal currents in close proximity to the seafloor and boundary-induced turbulence

et al. 2011

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“…It is clear that a tight logarithmic profile is not observed. Also, a two-fold log layer ('modified law of the wall'), as in Perlin et al (2005), is not observed here. These discrepancies with figure 5.…”

Section: Discussionmentioning

confidence: 89%

Bottom-pressure observations of deep-sea internal hydrostatic and non-hydrostatic motions

Haren

2013

J. Fluid Mech.

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In the ocean, sloping bottom topography is important for the generation and dissipation of internal waves. Here, the transition of such waves to turbulence is demonstrated using an accurate bottom-pressure sensor that was moored with an acoustic Doppler current profiler and high-resolution thermistor string on the sloping side of the ocean guyot 'Great Meteor Seamount' (water depth 549 m). The site is dominated by the passage of strong frontal bores, moving upslope once or twice every tidal period, with a trail of high-frequency internal waves. The bore amplitude and precise timing of bore passage vary every tide. A bore induces mainly non-hydrostatic pressure, while the trailing waves induce mainly internal hydrostatic pressure. These separate (internal wave) pressure terms are independently estimated using current and temperature data, respectively. In the bottom-pressure time series, the passage of a bore is barely visible, but the trailing high-frequency internal waves are. A bore is obscured by higher-frequency pressure variations up to ∼ 4 × 10 3 cpd ≈ 80N (cpd, cycles per day; N, the large-scale buoyancy frequency). These motions dominate the turbulent state of internal tides above a sloping bottom. In contrast with previous bottom-pressure observations in other areas, infra-gravity surface waves contribute little to these pressure variations in the same frequency range. Here, such waves do not incur observed pressure. This is verified in a consistency test for large-Reynoldsnumber turbulence using high-resolution temperature data. The high-frequency quasiturbulent internal motions are visible in detailed temperature and acoustic echo images, revealing a nearly permanently wave-turbulent tide going up and down the bottom slope. Over the entire observational period, the spectral slope and variance of bottom pressure are equivalent to internal hydrostatic pressure due to internal waves in the lower 100 m above the bottom, by non-hydrostatic pressure due to high-frequency internal waves and large-scale overturning. The observations suggest a transition between large-scale internal waves, small-scale internal tidal waves residing on thin (∼1 m) stratified layers and turbulence.

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“…The 3-D simulations will also be equipped with virtual Eulerian ADVs spanning the lower 10% of the water column and virtual seafloor pressure sensors. Simulated dissipation rates combined with virtual ADV data will help assess the efficiency of proposed parameterizations of NLIW energy losses due to interactions with the seafloor (Perlin et al 2005) and the energetic impact of such losses in along-path energy transport by NLIWs (Moum et al 2007) as measured in the ONR-funded New Jersey Shallow Water 06 experiment on the New Jersey shelf. Furthermore, high-pass filtered virtual pressure sensor data can provide insight towards the signature of NLIW-induced turbulence in high-frequency seafloor pressure sensors (Moum and Nash 2007) compensated for hydrostatic pressure effects.…”

Section: Resultsmentioning

confidence: 99%

Benthic Turbulence and Mixing Induced by Nonlinear Internal Waves

Diamessis¹

2007

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LONG-TERM GOALSThe long term goal of this work is to develop a fundamental understanding and predictive capability of the underlying physics of the interaction of nonlinear internal waves (NLIWs) with the continental shelf seafloor over a broad range of environmental conditions. We are particularly interested in how such interactions impact underwater optics and acoustics and shelf energetics and ecology by stimulating enhanced benthic turbulence and bottom particulate resuspension. OBJECTIVESThe specific objectives of this project are directed towards:• Characterizing the structure and energetics of the three-dimensional turbulence and mixing in the NLIW-induced time-dependent boundary layer as a function of wave-based Reynolds number and wave amplitude.• Comparing results of Direct Numerical Simulation (DNS) of NLIW-induced boundary layers with equivalent field observations to:o Flesh out the underlying fluid dynamics and, in particular, determine whether global instability of the NLIW-induced boundary layer is operative in the coastal ocean.o Provide consistency checks for the DNS along with means for further refining future simulations.o Develop predictive tools for designing future deployments focused towards identifying signatures of energetic NLIW-induced benthic events. APPROACHOur approach uses Direct Numerical Simulation (DNS) based on a spectral multidomain penalty method Navier-Stokes solver developed by the PI (Diamessis et al. 2005) for the simulation of high Reynolds number incompressible flows in vertically finite domains. The advantages of this computational tool lie in its high (spectral) accuracy, spatial adaptivity (straightforward resolution of 1

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A modified law‐of‐the‐wall applied to oceanic bottom boundary layers

Cited by 99 publications

References 19 publications

Shallow water tidal currents in close proximity to the seafloor and boundary-induced turbulence

Shallow water tidal currents in close proximity to the seafloor and boundary-induced turbulence

Bottom-pressure observations of deep-sea internal hydrostatic and non-hydrostatic motions

Benthic Turbulence and Mixing Induced by Nonlinear Internal Waves

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