| Summary: | 碩士 === 國立海洋大學 === 河海工程學系 === 85 === In the designs of seawall, harbor and ocean structures, the
wave forces areestimated. In order to ensure the safety of the
ocean structures under wave forces,the diffraction and
refraction in wave are discussed.In the pass years, various
numerical models have proposed. Combined boundary element method
and perturbation,dual reciprocity boundary element method have
been presented.Thetwo numerical methods, one of them with domain
integral and the other with great matrix are complex. This paper
presents a numerical model combined dual reciprocity boundary
element method (DRBEM) and perturbation technique to analyze
wave refraction-diffraction around a circular island with the
changes in wave forces and wave pressure. In this paper, the
analyze domains are seperated into two parts. One for contant
water depth,the other one is varying water depth with varying
geometry.the governing equation for contant water depth is the
mild slope equation. Based on perturbation technics, a
homogeneous Helmholtz equation and a non-homogeneous Helmholtz
equation can be obtained. The homogeneous Helmholtz equation can
be applied on boundary element analysis. The slove equation were
substitute into the non-homogeneous Helmholtz equation. Based on
the dual reciprocity boundary element method(DRBEM), the
integration in the domain is improved. In this paper,
combining dual reciprocity boundary element method and
perturbation method, the wave diffraction and refraction
problems are discussed. The calculated results are compared with
those by Homma(1950). Comparisons with those obtained by
Poulin(1996) and Rangogni(1988) are conducted, in order to show
the applicability of this model. Good agreements are obtained.
The model showed to be an adaptable method for solving wave
refraction-diffraction problems with varying geometry. In this
paper, different topography and wave periods are adopted,in
order to discuss the wave forces on circular island with varying
geometry.
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