The dynamics of offshore structures evaluated by boundary integral techniques

Abstract

SUMMARYThis paper is concerned with the development of transfer functions for the dynamic response of multidegree-of-freedom offshore structures, excited by sinusoidal waves. The problem is formulated in terms of the principal modes of the structure vibrating freely in zlucuo. The hydrodynamic analysis is performed through use of a distribution of wave sources on the submerged surface of the structure, which leads to an approximate solution satisfying the boundary condition on the fluid-structure interface at a discrete set of points. Generalized forces are obtained corresponding both to excitation by waves and to the hydrodynamic reactions induced by motions of the structure: the latter are expressed in terms of added mass and damping matrices. Results are given for simple geometries to illustrate the approach.

Stochastic hydroelastic analysis of pontoon-type very large floating structures considering directional wave spectrum

“…The single frequency velocity potential  of water can be separated into the diffracted part D  and the radiated part R  based on the linear potential theory. The radiated potential R  can be further decomposed as [11] …”

Flow chart for numerical coupling of dynamic problems in elastic media

“…This allows us to define, by analogy, the basic matrices [.9] and [4] satisfying C L @ I {~l = C a I {~9 > -Now in the general case where [9] and [d] are nonsymmetrical, they produce the following steps. Let The relative value is the real part (resp.…”

“…The matrices [9] and [4] are diagonal and the matricial form obtained is that obtained by the integral representation. This allows us to define, by analogy, the basic matrices [.9] and [4] satisfying C L @ I {~l = C a I {~9 > -Now in the general case where [9] and [d] are nonsymmetrical, they produce the following steps.…”

“…3 The method of singularities is also appropriate for this type of problem and may be combined with the FEM. [4][5][6] For confined and external light fluids separated by a structure, Astley and Cummings used the modal series and the FEM both for the structure and for the external fluid near the structure.' M. A. Hamdi used the boundary integral method (BIM) and the FEM to describe the acoustical field inside and outside an open-ended duct with elastic walls.…”

Network dynamic stability of floating airport based on amplitude death

“…Different from the pontoon-type proposed by Japanese, the US navy also proposed mobile offshore base (MOB) which consists of several semi-submersible modules with a total length of about 5000 ft in the late1999s to support military operations where conventional land bases were not available (Bhattacharya et al, 2006). Apart from Japan and USA, other countries such as Norway (Faltinsen, 1996;Rognaas et al, 2001), the United Kingdom (Taylor and Waite, 1978), Netherlands (Pinkster and Fauzi, 1997), China (Chen et al, 2001;Fu et al, 2007), Korea (Hong et al, 1999) and Singapore (Koh and Lim, 2009) have carried out researches on VLFS. Design of large scale floating airport is difficult, because it has to satisfy stringent functional and operational requirements (Gao et al, 2011).…”