Mathematical Physics


Depth-Integrated Characteristics of Nonlinear Water Waves

Authors: Yakov A. Iosilevskii

This exposition has the following main objects in view. (1) All main depth-integrated time-dependent and time-averaged characteristics, – as the velocity potential, velocity, pressure, momentum flux density tensor, volumetric kinetic, potential, and total energies, Poynting (energy flux density) vector, radiation (wave) stress tensor, etc, – of the ideal (inviscid, incompressible, and irrotational) fluid flow in an imaginary wave-perturbed infinite water layer with an arbitrary shaped bed and with a free upper boundary surface, and also the pertinent depth-integrated time-dependent and time-averaged differential continuity equations, – as those of the mass density, energy density, and momentum flux density (Euler’s and Bernoulli’s equations), etc, – are rigorously deduced from the respective basic local (bulk and surface) characteristics and from the respective bulk continuity equations, with allowance for the corresponding exact kinematic boundary conditions at the upper (free) and bottom surfaces and also with allowance for the corresponding exact dynamic boundary condition at the free surface, which follows from the basic Bernoulli equation. (2) The recursive asymptotic perturbation method with respect to powers of ka that has been developed recently by the present author for the local characteristics and bulk continuity equations of the ideal fluid flow in the presence of a priming (seeding) progressive, or standing, monochromatic gravity water wave (PPPMGWW or PSPMGWW) of a wave number k>0 and of wave amplitude a>0 in an imaginary infinite water layer of a uniform depth d>0 is extended to flow’s momentary and time-averaged (TA), depth-integrated (DI) characteristics and to their continuity equations, particularly to the 3x3 radiation, or wave, stress tensor (RST). (3) The extended recursive method is applied to PPPMGWW’s and PSPMGWW’s with the purpose to obtain their main TADI characteristics in terms of elementary functions. (4) The first non-vanishing asymptotic approximation of a characteristic, particularly that of the 3x3-TADIRST, of a PPPMGWW or PSPMGWW is generalized to a priming progressive, or standing, quasi-pane (PPQP or PSQP) MGWW. (5) The longshore wave–induced sediment transport rate, expressed by the so-called CERC (Coastal Engineering Research Council) formula, is briefly discussed in its relation to the (x,y)-component of the 3x3-TADIRST of the pertinent PPQPMGWW. (6) The presently common 2x2-TADIRST’s of progressive and standing water waves, which have been deduced by various writers from intuitive considerations and have been canonized about 55 years ago, are revised in accordance with the 3x3 ones of the recursive asymptotic theory.

Comments: 72 pages

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[v1] 2017-04-24 08:43:53

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