Search Results (2)

Aiming at the limited applicability of traditional empirical formulas in roll prediction for offshore wind turbine installation vessels (WTIVs), this study proposes a collaborative verification method that integrates model tests with Computational Fluid Dynamics (CFD) simulations. This approach reveals the influence mechanism of the fluid trapped in the leg-spudcan well region on the roll period and damping, facilitating high-precision prediction. A numerical model of the WTIV in a jack-up operating condition was established, and a CFD method based on the RANS equations was employed alongside experimental data for synergistic analysis. The results demonstrate that the fluid in the leg-spudcan well generates a significant additional moment of inertia, which reduces the natural roll period by approximately 7% and increases the damping coefficient by approximately 58%. Furthermore, an increase in leg length leads to a linear increase in damping and a linear decrease in the roll period. The motion response transfer functions derived from tests and the motion response errors of key structures in irregular waves are generally less than 10%. On this basis, a motion response conversion method applicable to any location on the entire ship is derived, providing a reliable numerical analysis tool for WTIV seakeeping evaluation and operational window assessment. Full article

Few studies have addressed jack-up substructures with spudcans for offshore wind turbines targeting multi-layer seabed conditions, which are frequently found in the Korean seabed. This study analyzed existing guidelines to establish geotechnical design procedures for a newly proposed jack-up substructure supported by tubular legs with spudcans, as well as to present design cases for a target site. This jack-up spudcan was designed for seabed conditions representative of the Korean southwestern offshore seabed, consisting of a sand–clay–sand layer. Analytical procedures from ISO and InSafeJIP guidelines were adopted to estimate the vertical bearing capacity of the spudcan. The yield envelope was determined based on this estimation, and the spudcan size was selected using structural reaction forces. Predictions from theoretical equations were compared with results from centrifuge tests for verification and discussion. Theoretical vertical capacities according to ISO match well with centrifuge results in sand-over-clay layers, while InSafeJIP shows a similar trend in intermediate clay layers. For clay-over-sand layers, only the vertical capacity formula for a single-sand layer case is available in the guidelines, which tends to overestimate the actual capacity for the underlying sand. However, by applying appropriately selected strength reduction factors, the actual foundation behavior can be reasonably predicted for design, but it is still overestimated, requiring further study. Full article