Study of Free Span VIV Reduction for Undersea Pipeline

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14974
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 24020:Marine engineering-related
• Research Institution: National Institute of Maritime, Port and Aviation Technology
• Principal Investigator: Fujiwara Tomo 国立研究開発法人海上・港湾・航空技術研究所, その他部局等, 研究員 (70511591)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: パイプライン / 渦励振 / free span VIV / 水槽実験 / 流体力計測 / ストレーキ / ディンプル / 3Dプリンター

Outline of Final Research Achievements

As a damping mechanism for pipelines, several surface patterns were proposed, and a scaled model was fabricated using a 3D printer to measure fluid forces during excitation and non-excitation. The results showed that (1)the damping coefficient of the lift component increases as the gap between the pipe and the bottom narrows during excitation, (2)it is possible to realize a strake surface pattern that does not generate VIV with a positive damping coefficient at any excitation amplitude, even if the fin is high enough and shaped enough not to damage it when the pipeline laid, (3)Dimpling can reduce the drag coefficient of a vibrating pipeline, but is not expected to be effective in suppressing VIV.

Free Research Field

船舶海洋工学

Academic Significance and Societal Importance of the Research Achievements

本研究で提案する表面パターンを施したパイプラインは、接地位置の間に浮いた状態の部分に海底近傍を流れる不規則な潮流が当たることで渦剥離に起因する振動が発生しないため、繰り返し振動することによる疲労が発生せず、運用年数の向上と交換頻度の減少が期待できる。
また、加振円柱のwall effectを実験的に評価したことと平滑円柱以外の表面パターンの加振流体力計測を行ったことは、類似研究を進めるうえで貴重な計測データとなる。