https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/153 2025-12-18T19:56:11Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/11002 Title: High fidelity simulations of a floating offshore wind turbine in irregular waves by coupling OpenFOAM and OpenFAST Authors: Kim, Young Jun; Charlou, Moran; Bouscasse, Benjamin; Leroy, Vincent; Aliyar, Sithik; Bonnefoy, Felicien; Kim, Kyong-Hwan; Choi, Young-Myung Abstract: This study introduces a solver that integrates the computational capabilities of OpenFAST, OpenFOAM, and MoorDyn to simulate a floating offshore wind turbine (FOWT) by considering aerodynamics, servo-control, hydrodynamics, and mooring system under various environmental conditions. This solver aims to model the wave？structure interaction around the platform with high fidelity while simplifying the servo-aerodynamic loads on the wind turbine. The coupling is validated using the database from the SOFTWIND benchmark project at ？cole Centrale Nantes. A spar-type FOWT in three irregular wave conditions with and without a wind field, are selected for the validation. The FOWT motions and mooring line tensions obtained from simulations and experiments are compared. The simulations closely matched the experimental results, confirming the effectiveness and high fidelity of the coupling solver in replicating real-time hybrid experiments and its potential use in general FOWT analyses. 2025-04-01T00:00:00Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/10602 Title: Design and thermodynamic evaluation of onboard NH3 BOG re-liquefaction systems for ocean-going NH3 Carriers Authors: Ji, Sangmin; Park, Sejun; Seo, Youngkyun; Choi, Minsoo; Lee, Jinkwang Abstract: This study stems from the burgeoning interest in ammonia (NH3) as a green energy source, particularly for maritime applications where conventional refrigeration cycles pose both environmental and economic challenges, specifically focusing on an 88,000 m3 class Very Large Ammonia Carrier (VLAC). Two distinct refrigeration cycle concepts were evaluated for the re-liquefaction system. The optimization technique used in the study was a hybrid method that combined the SQP and BOX algorithms to optimize the system. Key process variables were set to the final compression and expansion pressures of the refrigeration cycle, which were optimized to minimize the specific energy consumption (SEC) of the systems. An economic analysis was conducted to assess the costs associated with the equipment used in both systems. The first optimized re-liquefaction system employs a vapor-compression refrigeration cycle using NH3 as the refrigerant. The thermodynamic analysis indicated energy consumption, SEC, and exergy efficiency of 112.44 kW, 0.1898 kWh/kg, and 38.31 %, respectively. The second system utilizing the Linde？Hampson refrigeration cycle demonstrated energy consumption, SEC, and exergy efficiency of 102.35 kW, 0.1728 kWh/kg, and 43.03 %, respectively. Exergy destruction within these systems was predominantly observed in the heat exchangers, accounting for 43.00 % and 51.80 % of the total exergy destruction, respectively. Economic analysis revealed that the life cycle cost (LCC) and sensitivity analysis of the re-liquefaction system using the Linde-Hampson refrigeration cycle are approximately 2.0 million USD lower than the system using the vapor compression refrigeration cycle. In conclusion, the Linde-Hampson re-liquefaction system is energy efficient and economical. ？ 2024 The Author(s) 2025-02-01T00:00:00Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/11001 Title: Numerical Study of Slamming Loads on Bow Flare of FPSO Model by Irregular Waves Authors: Kim, Young Jun; Kim, Kyong-Hwan; Nam, Bo Woo; 홍사영; Ha, Yoon Jin Abstract: Numerical studies were performed to investigate bow flare slamming loads under irregular waves. To estimate the slamming forces in the simulations, two time windows were selected based on existing experimental data. This study examined horizontal and vertical slamming phenomena by analyzing the relationship between the motions and the resulting slamming forces. The horizontal and vertical slamming forces from the simulations were directly compared with the experimental data. Furthermore, the experiment and simulation results were compared against a representative classification code for additional validation. The findings provide insights into the physical phenomena of horizontal and vertical slamming and confirm that the formulation suggested by classification societies provides a reasonable estimation of slamming loads. Finally, the results emphasize that both horizontal and vertical slamming forces are significant design parameters. 2025-02-01T00:00:00Z https://www.kriso.re.kr/sciwatch/handle/2021.sw.kriso/10527 Title: Performance improvement of a cross-flow air turbine for oscillating water column wave energy converter by nozzle and blade optimization Authors: Baddegamage, B.H.B.P.D.; Bae, Seong Jong; Jang, Seung Hyun; Gunawardane, S.D.G.S.P.; Lee, Young-Ho; Kim, Kilwon; Yoon, Min Abstract: The global pursuit of renewable energy solutions has highlighted the potential of wave energy converters (WECs), particularly oscillating water column (OWC) systems, as viable clean energy sources. This study focuses on optimizing a cross-flow air turbine (CFAT) through comprehensive numerical simulations, aimed at enhancing its performance as the power take-off system in OWC applications. The influences of various geometrical parameters, such as including nozzle entry arc angle, nozzle starting angle, and angle of attack, on the performance of the CFAT are investigated. The optimized turbine model achieves a peak efficiency (η) of 0.71 in unidirectional flow at a flow coefficient (Φ) of 0.41, representing a significant improvement over the reference model (η = 0.61 at Φ = 0.29). In addition, the performance of the optimized CFAT is evaluated under regular wave conditions, simulating the bidirectional flow typical of real-world OWC applications. Although the peak efficiency in reciprocating flow slightly decreases, shifting to 0.68 at Φ = 0.53, the turbine maintains a high mean efficiency throughout the operating cycle. The results demonstrate that the optimized CFAT model provides robust performance in both unidirectional and bidirectional flows, making it a promising candidate for enhancing the efficiency of OWC-based WECs. ？ 2024 Elsevier Ltd 2025-01-01T00:00:00Z