http://yetl.yabesh.ir/yetl1/handle/yetl/19048 Sun, 03 May 2026 10:01:12 GMT 2026-05-03T10:01:12Z http://localhost:80/yetl1/bitstream/id/184269/ http://yetl.yabesh.ir/yetl1/handle/yetl/19048 http://yetl.yabesh.ir/yetl1/handle/yetl/4310771 Hydroelastic Analysis of Interconnected Offshore Floating Photovoltaic Floats Leventopoulou, Theano; Dai, Jian; Jiang, Zhiyu Floating photovoltaic (FPV) concepts have recently emerged as a promising solution for sustainable energy generation, gaining increasing market interest. Despite their potential, FPV systems face significant design challenges related to cost-effectiveness and structural integrity. For FPV arrays in offshore conditions, the structural and hydrodynamic performance of interconnected modules under wave action is a critical consideration, yet research in this area remains limited. This numerical study focuses on the frequency-domain hydroelastic analysis of a novel FPV concept with semi-submersible floats and rope connections. Each float is simplified as a rectangular plate and modeled using the Mindlin plate theory. A hybrid boundary element-finite element method code is modified and verified to account for the connection stiffness between the floats. Subsequently, a case study is conducted for two and three interconnected plates in two orientations, considering realistic material properties for the connections. The analysis examines the bending moments, deformations, and stresses of the plates under various wave periods and headings. Additionally, the effect of connection stiffness on the responses of the floats is evaluated under varying wave periods. The findings indicate that softer connections mitigate adverse effects, and the differences in structural responses remain below 5% for connections with two material properties. While the system exhibits sensitivity to shorter wave periods, the maximum von Mises stress is well below the allowable yield stress. Overall, the hydroelastic response confirms the good structural integrity of the configurations. This study contributes to a fundamental understanding of modular floating systems under wave effects. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4310771 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310768 Efficient Project Planning for Floating Offshore Wind Farm Development1 Sobashima, Shintaro; Wada, Ryota; Manuel, Lance The expectation of rapid growth in floating offshore wind farms (FOWFs) calls for urgent development of the associated supply chain comprising floater fabrication, transportation, assembly, and installation. As the intermediate stock of floaters is limited, irregular and unplanned suspension of operations that could arise due to unfavorable weather conditions would strongly influence the supply chain. Successful throughput in the supply chain results from available infrastructure that defines the stock and flow capacity for each step in the project. The complexity of the interactions among the processes and the uncertainty of weather conditions pose significant challenges in planning an efficient infrastructure development plan to meet the future demand for FOWFs. This study proposes a planning method that evaluates the performance of various configurations in such development using a stock–flow simulation model while considering weather conditions. By using this dynamic model, challenges in the supply chain arising from limited stock or unfavorable weather conditions can be replicated, and the infrastructure development plans necessary to meet project requirements can be suggested. The model is validated by using data from an existing FOWF project and applied to a case study in Kyushu, Japan to propose port infrastructure development plans to achieve the desired performance. From the case study, setting the operational limit for weather conditions was identified as the primary bottleneck by quantifying operation rates and downtime for each infrastructure. Improvement solutions for the identified bottlenecks significantly alleviate demands on other infrastructure and decrease the impact of weather uncertainty. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4310768 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310765 Analysis of Tensile Response of an Unbonded Flexible Riser With Belt Corrosion in Tensile Armor Layers Lei, Qinglong; Chen, Chenyang; Xia, Wenxiu; Zhu, Xiaohua Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4310765 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310764 Torsional Vibration of Drill String Induced by Heave Motion in Deepwater Drilling Kaneko, Tatsuya; Inoue, Tomoya; Wada, Ryota; Katsui, Tokihiro; Suzuki, Hiroyoshi Understanding drill string dynamics is essential to improving drilling efficiency and preventing accidents. Previous studies have mainly focused on self-excited oscillations due to stick–slip and bit-bounce. However, in deepwater drilling, large weight-on-bit (WOB) fluctuations due to heave motion are a significant concern that can affect torsional dynamics. This article reports analytical, numerical, and field data investigations on torsional vibrations of a drill string in deepwater drilling. First, we analyzed the field data from a deep-sea scientific drilling vessel Chikyu. The field data showed that heave, WOB, and torque oscillated at similar frequencies. This result indicated that the drill string could have forced torsional vibrations due to heave instead of self-excited vibrations due to stick–slip. Second, we analytically and numerically investigated drill string torsional dynamics. The torsional vibration of the drill string can be described only by self-excited vibration due to stick–slip if WOB is constant. However, when the WOB fluctuates, the forced vibration of the WOB must be considered. The results showed that vibration at the heave frequency had a more significant effect on torsional vibration than the axial self-excited frequency for the same amplitude of WOB variation. In addition, large WOB fluctuations increased the risk of stick–slip and reverse rotation of the drill bit. Numerical experiments with the field data showed that the forced torsional vibration caused by heave motion was predominant in deepwater drilling. These results show the importance of capturing forced torsional vibrations and reducing WOB fluctuations. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4310764 2025-01-01T00:00:00Z