Internal waves from a body accelerating in a thermocline

Nicolaou, D.; Garman, J. F. R.; Stevenson, T. N.

doi:10.1007/bf00868470

Cited by 9 publications

(8 citation statements)

References 18 publications

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“…Perturbations generated by the boat give birth to both modes, especially when the acceleration of the boat is important. This result is consistent with the study of Nicolaou et al (1995), verified experimentally by Robey (1997), stating that an accelerated object in a continuously stratified fluid, with a Brunt-Väisälä frequency N (z), excites a continuum of modes whose vertical profile w(z) is described by…”

Section: Discussionsupporting

confidence: 90%

“…In a slightly different perspective, Nicolaou et al (1995) demonstrated that an object accelerating in a stratified fluid generates oblique and transverse internal waves, the latter can be decomposed as a sum of baroclinic modes with the lowest mode always present. Shishkina (2002) further showed through experiments that in such a dynamical evolution, the baroclinic modes generated propagate independently of each other, although nonlinear effects must become : 3 important when the amplitude of the internal waves is increasing.…”

Section: Other Dead-water Related Workmentioning

confidence: 99%

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Resurrecting dead-water phenomenon

Mercier

Vasseur

Dauxois

2011

Nonlin. Processes Geophys.

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Abstract.We revisit experimental studies performed by Ekman on dead-water (Ekman, 1904) using modern techniques in order to present new insights on this peculiar phenomenon. We extend its description to more general situations such as a three-layer fluid or a linearly stratified fluid in presence of a pycnocline, showing the robustness of dead-water phenomenon. We observe large amplitude nonlinear internal waves which are coupled to the boat dynamics, and we emphasize that the modeling of the wave-induced drag requires more analysis, taking into account nonlinear effects.Dedicated to Fridtjöf Nansen born 150 yr ago (10 October 1861).

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Section: Discussionsupporting

confidence: 90%

Section: Other Dead-water Related Workmentioning

confidence: 99%

Resurrecting dead-water phenomenon

Mercier

Vasseur

Dauxois

2011

Nonlin. Processes Geophys.

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“…The profile I1I is given by the following function, which was also used by Ermanyuk & Gavrilov (2002, 2003) and Nicolaou et al. (1995) in their studies: …”

Section: Methodsmentioning

confidence: 99%

“…Robey (1997) studied internal waves generated by a sphere moving below a pycnocline using experimental and numerical techniques for a wide range of body based Reynolds numbers ( Re ) and Froude numbers ( Fr ). Nicolaou, Garman & Stevenson (1995) experimentally studied the waves of an accelerating sphere in a thermocline (a pycnocline where density gradients are a result of temperature gradients).…”

Section: Introductionmentioning

confidence: 99%

Disk wakes in nonlinear stratification

et al. 2023

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Nonlinearity of density stratification modulates buoyancy effects. We report results from a body-inclusive large eddy simulation of a wake in nonlinear stratification, specifically for a circular disk at diameter-based Reynolds number ( ${\it Re} $ ) of $5000$ . Five density profiles are considered; the benchmark has linear stratification and the other four have hyperbolic tangent profiles of the same thickness to model a pycnocline. The disk moves inside the central core of the pycnocline in two of those four cases and, in the other two cases with a shifted density profile, the disk moves partially/completely outside the pycnocline. The maximum buoyancy frequency ( $N_{max}$ ) for all the profiles is the same. The first part of the study investigates the centred cases. Non-uniform stratification results in increasing wake turbulence relative to the benchmark owing to reduced suppression of turbulence production as well as wave trapping in the pycnocline. Steady lee waves are also quantified to understand the limitations of linear theory. The second part pays attention to the effect of a relative shift between the pycnocline and the disk. The wake defect velocity decays substantially faster in the cases with a shift and the wake has higher turbulence level. The effect of disk location on the Kelvin wake waves (a family of steady waves within the pycnocline) and its modal form is obtained and explained by solving the Taylor–Goldstein equation. The family of unsteady internal gravity waves that are generated by the wake is also studied and the effect of disk shift is quantified.

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“…The internal wave fields were measured for supercritical densimetric Froude numbers, > 1, and compared with the theoretical results by Tulin and Miloh (1991). Nicolaou et al (1995) studied an impulsively accelerating source in a thermocline using ray theory (Stevenson, 1973;Woodhead, 1983) with focus on unsteady waves, analyzing both oblique and transverse internal waves. It was observed that low speeds created transverse waves with longer wavelength and they could be decomposed as a sum of baroclinic modes with permanent presence of the lowest mode.…”

Section: Ships and Submarines In Stratified Flowsmentioning

confidence: 99%

A ship advancing in a stratified fluid

Esmaeilpour¹

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for all his support, guidance and encouragement in the preparation of this thesis. He accepted me in his research group and spent a lot of time for discussing concepts and reviewing my work. Without his helps this work could not have been accomplished. I would like to acknowledge Dr. Juan E. Martin for all his support and advice during my graduate studies. His expertise in ship hydrodynamics was quite valuable in helping me to achieve the project goals in my work. I would also like to thank my committee members, Professors Udaykumar, Buchholz and Harwood for their dedication to the examination of the thesis. Undoubtedly, their criticism, suggestions and support help me to improve my work significantly. My appreciation also extends to my amazing friends in my research group at the University of Iowa, whom provided a light-hearted working atmosphere and they certainly made work very enjoyable during this journey. I also like to express gratitude to the sponsors of this work.

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Internal waves from a body accelerating in a thermocline

Cited by 9 publications

References 18 publications

Resurrecting dead-water phenomenon

Resurrecting dead-water phenomenon

Disk wakes in nonlinear stratification

A ship advancing in a stratified fluid

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