A FINITE ELEMENT MODEL FOR WIND WAVE DIFFRACTION

Ove Skovgaard, Lars Berhrendt, Ivar G. Jonsson

Abstract


The applicability of a hybrid finite element model for the calculation of combined diffraction-refraction of small time-harmonic water waves is demonstrated. The model is valid for arbitrary water depths and wave lengths, i.e. it is based on intermediate depth theory (IDT). The model includes arbitrarily varying partial reflection along the boundaries. Superposition of waves (to simulate a spectrum approach) with different incident directions is demonstrated, and CPU-times and core memory requirements are given. The model is verified and documented with respect to sensitivity of the model parameters in detailed tables, using the classical Homma island on a parabolic shoal. The wave period is here chosen in such a way that a small number of elements (larger than 500 and less than 2,000) is enough to get an accurate solution. For a new simple, but realistic harbour geometry many detailed and accurate graphical results are given. The wave period (T = 9 sec.) is here chosen so that it is representative for natural wind waves, and the size of the harbour is selected, so that the model gets a fairly large number of elements (of the order 10,000).

Keywords


diffraction; wind wave; finite element model; diffraction model

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