The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
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TIME-DOMAIN COMPUTATION METHODS FOR A FLOATING PLATFORM OF COMPLICATED GEOMETRY WITH MULTIPLE WAVE INTERACTIONS


Go-down ichd2016 Tracking Number 42

Presentation:
Session: Hydrodynamics in Ocean II
Room: Room 3
Session start: 14:00 Mon 19 Sep 2016

Yuichi Ashida   ashida_yuichi@naoe.eng.osaka-u.ac.jp
Affifliation: Osaka University

Takeshi Hara   hara_takeshi@naoe.eng.osaka-u.ac.jp
Affifliation: Osaka University

Takuya Taniguchi   taniguchi_takuya@naoe.eng.osaka-u.ac.jp
Affifliation: Osaka University

Masashi Kashiwagi   kashi@naoe.eng.osaka-u.ac.jp
Affifliation: Osaka University


Topics: - Hydrodynamics in ocean, coastal and estuary engineering

Abstract:

Wave interactions are complicate and thus important in evaluating the performance of a floating platform of complicate geometry which consists of several different members of submerged structures, because generated waves will be reflected infinitely back and forth among the submerged structure members. Due to these multiple wave interactions, resulting hydrodynamic forces on the platform may fluctuate depending on the wave frequency and hence the rate of approaching zero in the damping force with increasing the wave frequency becomes slow. This is related to the slow convergence in the memory-effect function with the increase in time and also related to the increase of computation time in the time-domain direct computation for obtaining a steady state after multiple wave reflections among submerged structure members of a floating platform. These phenomena and associated difficulties in the time-domain computation methods for a floating platform of complicated geometry will be discussed in the paper. The time-domain Green function method and higher-order boundary element method will be used in the time-domain direct computation method, and obtained results are compared with corresponding results by the other method which computes a convolution integral using the memory-effect function which can be computed from the damping-force coefficient obtained in the frequency-domain problem. A numerical technique to reduce the computation time while keeping the sufficient accuracy will be proposed in the paper.