Nonlinear Effects due to Variations of Volume and Configuration and Scale Effects of Airchamber of OWC Type WECs

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01646
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 24020:Marine engineering-related
• Research Institution: Nihon University
• Principal Investigator: IKOMA Tomoki 日本大学, 理工学部, 教授 (50302625)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 振動水柱 / 縮尺影響 / 波力発電 / 圧縮性 / 空気室 / 粘性 / ポテンシャル理論 / 強制動揺実験

Outline of Final Research Achievements

Regarding an airchamber of oscillating water column type wave energy converters, degree of scale effects between a small-scaled model and a full-scale model and their reasons were investigated. The study performed forced-oscillation tests in a still water and theoretical calculations based on the linear potential theory.
From a result, configurations of OWC models with large air pressure made the scale effect to be strong. However, the pressure and the variation were affected little by the homothetic ratio to set airchamber-volume of the models in both cases when it was considered or not that the atmosphere is always same for model scale and full scale. The things suggest that the scale effect due to the compressibility of the air affected to the results little. Besides, it was suggested that small phase difference between the pressure and the volume variation due to the air compressibility influenced the primary conversion performance of the OWC models little from the calculations.

Free Research Field

船舶海洋工学

Academic Significance and Societal Importance of the Research Achievements

振動水柱型波力発電装置における空気室の体積設定は，少なくとも模型実験ではその大きさが顕著に結果に影響しない。また，高周波数域で高速に空気室体積が変化するときに空気の圧縮影響が数パーセント程度であることが実験と理論計算から定量的に示された。理論的なモデル化とスケール影響の考慮が最も困難だと言われる振動水柱型システムの広範な波周波数域での最適化精度を向上できるなど，実機モデル製作の前段階で発電システムをより正確に再現した実験モデルの設計やそれを用いた実証実験のレベル向上が見込まれる。このことはTRL 5, 6レベルの実験をより優位に実施できることに貢献する。