Session: 01-03-02 Hydrodynamics-2

Submission Number: 181451

Hydrodynamic Forces on a Jacket Stick Array From an Embedded Focused Wave Within Random Seas 

Extreme wave crests govern the design and reliability of jacket-type offshore structures yet quantifying their transient loads in realistic random seas remains challenging and computationally costly. This study examines hydrodynamic forces on a simplified jacket using an embedded focused wave within a random sea state, the imposed wave shape being that of NewWave – the average shape of an extreme crest in a linear random Gaussian sea. The approach efficiently generates extreme events while preserving background variability. Fifty independent random realizations were simulated. Wave kinematics were used to compute Morison drag forces on a single vertical stick and on a five-stick array representing a jacket leg cluster. The coefficient of variance of peak force is approximately twice that of crest elevation, indicating stronger run-to-run variability in load than in surface elevation. The space-averaged peak force over the five-stick array is distinctly lower than the single-stick peak, indicating array-averaging and timing effects. An extreme crest of ~22 m was captured; the associated sub-crest kinematics were strongly localized in time and space. Four combinations of normal and inverted focused and background conditions were evaluated. Phase decomposition of these shows that a focused wave propagating through a random background remains largely unaltered relative to a standalone NewWave: the focus time and location shift only slightly, and peak kinematics are only modestly perturbed. These findings validate the embedded focused wave method as an effective and practical tool for producing extreme wave events within random seas for jacket-load assessment.

Presenting Author: Min Gao The University of Western Australia

Presenting Author Biography: Min Gao is a Research Fellow at the ARC ITRH TIDE group, The University of Western Australia. His research addresses wave–structure interaction and extreme wave events on offshore structures, combining laboratory experiments, high-fidelity numerical simulation and analytical modelling.

Authors:

Min Gao The University of Western Australia
Paul H. Taylor The University of Western Australia
Hugh Wolgamot The University of Western Australia