Internal wave boluses as coherent structures in a continuously stratified fluid

Vieira, Guilherme S.; Allshouse, Michael

doi:10.1017/jfm.2019.993

Cited by 13 publications

(28 citation statements)

References 88 publications

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“…After this time, the bolus begins to slow down as the wave slows in the shrinking water column, as found in numerical simulations by Arthur et al. (2017) and Vieira and Allshouse (2020). Despite forcing only 1.5 periods, a second and third bolus signature can be observed in Figure 3d.…”

Section: Resultsmentioning

confidence: 55%

“…In our experiments, the wave amplitude a has a value 0.016 ± 0.001 m, independent of the pycnocline thickness δ (see Figure 2d). Using the approximation method in Vieira and Allshouse (2020), we find that L sw for the initial wave generated ranges from 0.46 to 0.61 m, which yields Iribarren numbers ranging from 0.94 to 1.10. This puts the wave in the surging classification of Sutherland et al.…”

Section: Resultsmentioning

confidence: 96%

“…Figure 1e presents the induced horizontal velocity profile corresponding to the three stratifications in Figure 1d for ω = π /5 rad/s. For each pycnocline thickness, the plate amplitudes are adjusted to inject the same amount of kinetic energy in every experiment ( E h =0.56 mJ per half period; see Vieira and Allshouse (2020) equation (2.7) for the kinetic energy equation).…”

Section: Description Of the Experimentsmentioning

confidence: 99%

“…Numerical investigations by Arthur et al. (2017) and Vieira and Allshouse (2020) studied the impact of the pycnocline thickness on mixing and transport, as a function of the topography, stratification, and the properties of the incoming wave. Arthur et al.…”

Section: Introductionmentioning

confidence: 99%

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Dependence of Internal Wave Bolus Transport on Pycnocline Thickness

Allshouse

Swinney

2020

Geophysical Research Letters

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A bolus is a vortex formed by an internal wave propagating upslope with the shoaling wave. The amount of sediment and biota transported by boluses travelling up the world's continental slopes and onto the continental shelves has not been established but could be vital for maintaining nutrient‐rich coastal ecosystems. Previous laboratory experiments and simulations of shoaling boluses have considered a two‐layer density stratification or a linear density profile. We present experiments on bolus formation and propagation in a stratification with a density profile ρ(z) represented by a tanh‐profile, which describes many ocean pycnoclines. Our laboratory experiments examine pycnoclines with thicknesses varying from nearly zero (a two‐layer system) to large thicknesses where the density varies almost linearly with depth. The bolus volume, displacement upslope, and available potential energy are measured as a function of pycnocline thickness. Maximum upslope displacement is found to be twice that observed for a two‐layer stratification.

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Section: Resultsmentioning

confidence: 55%

Section: Resultsmentioning

confidence: 96%

Section: Description Of the Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dependence of Internal Wave Bolus Transport on Pycnocline Thickness

Allshouse

Swinney

2020

Geophysical Research Letters

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“…Cluster-based LCS methods take root in the field of unsupervised machine learning. Several algorithms have been adapted recently to LCS detection in geophysical flows [20,23,59]. A recurring concern with these methods is that the results rely on a set of user-input parameters, making the outcome subjective.…”

Section: Introductionmentioning

confidence: 99%

A Parameter-Free Spectral Clustering Approach to Coherent Structure Detection in Geophysical Flows

Filippi¹,

Rypina²,

Hadjighasem³

et al. 2020

Preprint

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In Lagrangian dynamics, the detection of coherent clusters can help understand the organization of transport by identifying regions with coherent trajectory patterns. Many clustering algorithms, however, rely on user-input parameters, requiring a priori knowledge about the flow and making the outcome subjective. Building on the conventional spectral clustering method of Hadjighasem et al (2016), a new parameter-free spectral clustering approach is developed that automatically identifies parameters and does not require any user-input choices. A noise-based metric for quantifying the coherence of the resulting coherent clusters is also introduced. The parameter-free spectral clustering is applied to two benchmark analytical flows, the Bickley Jet and the asymmetric Duffing oscillator, and to a realistic, numerically-generated oceanic coastal flow. In the latter case, the identified model-based clusters are tested using observed trajectories of real drifters. In all examples, our approach succeeded in performing the partition of the domain into coherent clusters with minimal inter-cluster similarity and maximum intra-cluster similarity. For the coastal flow, the resulting coherent clusters are qualitatively similar over the same phase of the tide on different days and even different years, whereas coherent clusters for the opposite tidal phase are qualitatively different.

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Dense pulses formed from fissioning internal waves

2022

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Cold pulses generated by the fission of internal solitary waves over gentle slopes are an important source of nutrients and relief from excess heat to benthic ecosystems. This numerical study investigates the effect of stratification form on pulses produced by fission of internal solitary waves propagating over a smooth, gentle, linear topographic slope in 2D simulations. Three stratification types are investigated, namely (i) thin tanh (homogeneous upper and lower layers separated by a thin pycnocline), (ii) surface stratification (linearly stratified layer overlaying a homogeneous lower layer) and (iii) broad tanh (continuous density gradient throughout the water column). Incident wave amplitude was varied. In the thin tanh stratification, good agreement is seen with past studies, whilst the dynamics observed in the surface stratification are very similar to those in the thin tanh stratification. However, in the broad tanh stratification, due to the different form of incident waves, the fission dynamics differ, but produce pulses similar in form to those produced by fission in the other stratifications. Pulse amplitude, wavelength and propagation velocity are found to strongly depend on incident wave amplitude, and each degenerate linearly as the pulse propagates upslope.

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Internal wave boluses as coherent structures in a continuously stratified fluid

Cited by 13 publications

References 88 publications

Dependence of Internal Wave Bolus Transport on Pycnocline Thickness

Dependence of Internal Wave Bolus Transport on Pycnocline Thickness

A Parameter-Free Spectral Clustering Approach to Coherent Structure Detection in Geophysical Flows

Dense pulses formed from fissioning internal waves

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