Documentation of a Computer Code by HKC Research to Calculate the Transmission of a Sonic Boom Through a Wavy Ocean Surface

Nonlinear interaction of shear flow with a free surface

Journal of Fluid Mechanics ◽

10.1017/s0022112094003496 ◽

1994 ◽

Vol 260 ◽

pp. 211-246 ◽

Cited By ~ 21

Author(s):

Athanassios A. Dimas ◽

George S. Triantafyllou

Keyword(s):

Free Surface ◽

Velocity Field ◽

Shear Flow ◽

Nonlinear Evolution ◽

Ocean Surface ◽

Computer Code ◽

Linear Instability ◽

Free Surface Elevation ◽

Instability Waves ◽

Induced Velocity

In this paper the nonlinear evolution of two-dimensional shear-flow instabilities near the ocean surface is studied. The approach is numerical, through direct simulation of the incompressible Euler equations subject to the dynamic and kinematic boundary conditions at the free surface. The problem is formulated using boundary-fitted coordinates, and for the numerical simulation a spectral spatial discretization method is used involving Fourier modes in the streamwise direction and Chebyshev polynomials along the depth. An explicit integration is performed in time using a splitting scheme. The initial state of the flow is assumed to be a known parallel shear flow with a flat free surface. A perturbation having the form of the fastest growing linear instability mode of the shear flow is then introduced, and its subsequent evolution is followed numerically. According to linear theory, a shear flow with a free surface has two linear instability modes, corresponding to different branches of the dispersion relation: Branch I, at low wavenumbers; and Branch II, at high wavenumbers for low Froude numbers, and low wavenumbers for high Froude numbers. Our simulations show that the two branches have a distinctly different nonlinear evolution.Branch I: At low Froude numbers, Branch I instability waves develop strong oval-shaped vortices immediately below the ocean surface. The induced velocity field presents a very sharp shear near the crest of the free-surface elevation in the horizontal direction. As a result, the free-surface wave acquires steep slopes, while its amplitude remains very small, and eventually the computer code crashes suggesting that the wave will break.Branch II: At low Froude numbers, Branch II instability waves develop weak vortices with dimensions considerably smaller than their distance from the ocean surface. The induced velocity field at the ocean surface varies smoothly in space, and the free-surface elevation takes the form of a propagating wave. At high Froude numbers, however, the growing rates of the Branch II instability waves increase, resulting in the formation of strong vortices. The free surface reaches a large amplitude, and strong vertical velocity shear develops at the free surface. The computer code eventually crashes suggesting that the wave will break. This behaviour of the ocean surface persists even in the infinite-Froude-number limit.It is concluded that the free-surface manifestation of shear-flow instabilities acquires the form of a propagating water wave only if the induced velocity field at the ocean surface varies smoothly along the direction of propagation.

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Imaging of biogenic and anthropogenic ocean surface films by the multifrequency/multipolarization SIR-C/X-SAR

Journal of Geophysical Research Atmospheres ◽

10.1029/98jc01915 ◽

1998 ◽

Vol 103 (C9) ◽

pp. 18851-18866 ◽

Cited By ~ 68

Author(s):

Martin Gade

Keyword(s):

Ocean Surface ◽

Surface Films

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Subnose-1. electrochemical tracking of odor plumes at 900 m beneath the ocean surface

Marine Ecology Progress Series ◽

10.3354/meps075303 ◽

1991 ◽

Vol 75 ◽

pp. 303-306

Author(s):

J Atema ◽

PA Moore ◽

LP Madin ◽

GA Gerhardt

Keyword(s):

Ocean Surface ◽

Odor Plumes

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The Computational Sublime in Nick Montfort's ‘Round’ and ‘All the Names of God’

CounterText ◽

10.3366/count.2015.0027 ◽

2015 ◽

Vol 1 (3) ◽

pp. 348-365 ◽

Cited By ~ 2

Author(s):

Mario Aquilina

Keyword(s):

Computer Code ◽

Computer Programs ◽

Literary Text ◽

Text Generation ◽

Mathematical Concepts ◽

Literary Space

What if the post-literary also meant that which operates in a literary space (almost) devoid of language as we know it: for instance, a space in which language simply frames the literary or poetic rather than ‘containing’ it? What if the countertextual also meant the (en)countering of literary text with non-textual elements, such as mathematical concepts, or with texts that we would not normally think of as literary, such as computer code? This article addresses these issues in relation to Nick Montfort's #!, a 2014 print collection of poems that presents readers with the output of computer programs as well as the programs themselves, which are designed to operate on principles of text generation regulated by specific constraints. More specifically, it focuses on two works in the collection, ‘Round’ and ‘All the Names of God’, which are read in relation to the notions of the ‘computational sublime’ and the ‘event’.

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