Numerical Modelling of a Circular-Water-Basin for Multi-directional freak Waves Using a Particle Based Method

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22396
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Hiroshima University
• Principal Investigator: KANEHIRA Taiga 広島大学, 先進理工系科学研究科(工), 助教 (50880019)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 粒子法 / SPH法 / 数値シミュレーション / FSI / 海洋巨大波

Outline of Final Research Achievements

Directionality of ocean waves is important for accurate evaluation of durability and electric performance of offshore structures such as vessels and ocean energy harvesters. However, it is difficult to reproduce multi-directional wave fields with wave breaking using existing numerical tool. In this study we developed a novel multi-directional wave basin numerical model which can reproduce multi-directional seas. We reproduced numerically a famous freak wave, the Draupner wave, and quantitatively compared wave breaking phenomena with experimentally observed one. The numerical results are good agreement with experimental results. The breaking phenomena such as maximum wave height, wave amplitude, water elevations are well reproduced in the model. The numerical model developed in this study can applied to breaking simulations or FSI probrems in multi-directional seas to provide further insight into the breaking mechanisms of freak waves, and to evaluate durability of offshore structures.

Free Research Field

船舶海洋工学

Academic Significance and Societal Importance of the Research Achievements

沖合は，異なる波向き周波数スペクトルを持つ波群が同時に存在する多方向不規則波浪場となる．しかしながら，現行の設計指針は一方向波浪場を前提として構築されており，設計外力に多峰性は考慮されていない．そのため，多方向波浪場において沈没船などの人命の損失を伴う海難事故が多数発生している．本課題では，現行の単峰性を考慮した設計指針に加え，新たに多峰性を考慮した海洋構造物の設計を可能とすべく，多方向波浪場を再現可能な数値計算技術を開発し，海洋構造物の設計に必要な波の物理諸量を明らかにした．そして，既往の一方向波浪場において構築されてきた破波指標が多方向波浪場においては適用不可能なことを報告した．