# Extreme Wave Loading on a Vertical Circular Cylinder
## 5 Conclusions  
A set of physical experiments on wave-truncated cylinder interactions were carried out, aiming to improve understanding of the nonlinear characteristics of extreme wave loading on a vertical cylinder, representing supporting foundations of offshore oil and gas platforms or offshore floating wind turbines. A transient wave group was used to model the individual extreme event in random seas in a more efficient and controlled manner. A range of wave conditions with varying wave steepness and spectral peak wave frequencies were considered, and the model cylinder was suspended at various heights, representing the breaker height and the instantaneous vertical position of the columns in water waves. The following conclusions are drawn:  
1. The four-phase separation method is found to work well even for long shallow-water waves of strong nonlinearity. The extracted harmonic structure of the wave fields is still apparent, and the \(n\)th harmonic wave scales with the \(n\)th power of the envelope of the linear wave component.
2. The four-phase separation method, in tandem with the iterative technique, works well for generating the desired focused wave groups even in the nearly shallow water regime. The known issue of downshifting in both spatial and temporal domains is resolved.
3. The relative contribution from the fundamental wave decreases with the increasing Ursell number, while the contributions from the higher-order harmonics increase, and both arrive at their corresponding saturation levels at larger Ursell numbers. The Ursell number indicates the wave nonlinearity in the long-wave regime, i.e., weighting the respective importance of the nonlinear and shallow-water effects.
4. Both horizontal and vertical impact forces are found to increase with the increasing inundation level, while the effect from the wave steepness is relatively small. The Santo scaling, i.e., \(\rho g(A_{L})^{2}h_{d}\), is introduced for non-dimensionalizing the peak horizontal force, which works very well. A reasonably good collapse in data is observed,  
Figure 12: Variation in the peak horizontal force with the inundation level. The horizontal force is made non-dimensional using \(\rho g(A_{L})^{2}h_{d}\).  
indicating that the 'destruction of momentum' argument may still be applicable to structures with curved surfaces.  
Conceptualization, S.L. and L.C.; methodology, L.C.; software, Y.Y.; validation, L.C., Y.Y. and X.G.; formal analysis, L.C.; investigation, L.C.; resources, S.L., Y.Y. and X.G.; data curation, Y.L.; writing--original draft preparation, Y.L.; writing--review and editing, L.C.; visualization, L.C.; supervision, L.C.; project administration, X.G.; funding acquisition, S.L., L.C. and X.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by [the National Key R&D Program of China] grant number [2019 YFB1504400], [China Southern Power Grid Technology Co. Ltd.] grant number [NY]S2020 KJ005-23], [the Natural Science Foundation of Liaoning Province] grant number [2021-KF-16-03] and [the Natural Science Foundation of China] grant number [grant no. 52001053].  
Not applicable.  
The authors declare no conflict of interest.  
The author declare no conflict of interest.