Research on the Structural Reinforcement to Optimize the Axial Tension of Rigid Riser in Water Depth Below 4,000m

Research Project

Project/Area Number	23K04265
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 24020:Marine engineering-related
Research Institution	National Institute of Maritime, Port and Aviation Technology
Principal Investigator	山本マルシオ国立研究開発法人海上・港湾・航空技術研究所, 海上技術安全研究所, 主任研究員 (10608631)
Co-Investigator(Kenkyū-buntansha)	村井基彦横浜国立大学, 大学院環境情報研究院, 教授 (60292893)
Project Period (FY)	2023-04-01 – 2026-03-31
Project Status	Granted (Fiscal Year 2023)
Budget Amount *help	¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000) Fiscal Year 2025: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2024: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000) Fiscal Year 2023: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Keywords	Deep Sea Mining / Hangoff Riser / Mathieu Instability / Rigid Riser / Structural Optimization
Outline of Research at the Start	We propose two structural reinforcements to reduce the axial tension of the vertical steel pipe that shall be used to produce manganese nodules in a water depth below 4,000m. However, it is unclear if such tension reduction could result in Mathieu's Instability. Thus, we will conduct experiments using reduced-scale models and simulations using Finite Element Analysis to verify the occurrence of this instability.
Outline of Annual Research Achievements	In this research, we want to develop structural reinforcement to reduce the axial tension of a vertical steel riser pipe, which will produce manganese nodules in water depths of 4,000m or deeper. We will investigate whether the reduced axial tension may result in Mathieu's Instability on the riser pipe. In FY2023, we simulated and experimented with the reference cases. In other words, we assumed a single pipe WITHOUT structural reinforcement for the simulation and experiment. [Simulation] We simulated the single pipe riser and observed this instability in a riser pipe with reduced axial tension. [Experiment] We developed the experimental apparatus to measure the strain on the pipe model. We used strain gauges to measure the strain.
Current Status of Research Progress	Current Status of Research Progress 3: Progress in research has been slightly delayed. Reason [SIMULATION] The simulation part progressed smoothly. We could simulate the single pipe riser (reference case). Further, we also observed Mathieu's instability when the axial tension was reduced. [Experiment] The development and procurement of the experiment apparatus progressed smoothly. Our initial plan was to measure the axial strain with and without internal pressure. The problem was we could not purchase several high-pressure components to apply the internal pressure because of the shortage of such stainless steel components. Therefore, we only carried out the experiment without pressure.
Strategy for Future Research Activity	In FY2024, we will carry out the experiment using the single pipe (FY2023 model) with internal pressure. In addition, we will develop and test a second model with structural reinforcement. In the simulation, we will also develop a numerical model, including the structural reinforcement. We plan to publish an article comparing the results of the single pipe and reinforced pipe.