Local Scour Mechanisms and Prediction Methods Around Offshore Wind Turbine Foundations:Insights and Future Directions

Local scour around offshore wind turbine foundations presents a considerable challenge due to its potential influence on structural stability,driven by hydrodynamic forces.While research has made strides in comprehending scouring mechanisms,notable complexities persist,specifically with newer foundation types.Addressing these limitations is vital for advancing our understanding of scour mechanisms and for improving mitigation strategies in offshore wind energy development.This review synthesizes current findings on local scour across various offshore foundations,encompassing field observations,data-driven approaches,turbulence-sediment interactions,scour evolution processes,influencing factors,and numerical model advancements.The objective is to enrich our understanding of local scour mechanisms.In addition,future research directions are outlined,including the development of robust arti-ficial intelligence models for accurate predictions,the exploration of vortex structure characteristics,and the refinement of numerical models to strengthen prediction capabilities while minimizing computational efforts.

Countermeasures for local scour at offshore wind turbine monopile foundations:A review

Local scour at monopile foundations of offshore wind turbines is one of the most critical structural stability issues.This article reviews the contemporary methods of scour countermeasures at monopile foundations.These methods include armouring countermeasures(e.g.,riprap protection)to enhance the anti-scour ability of the bed materials and flow-altering countermeasures(e.g.,collars and sacrificial piles)to reduce downflow or change flow patterns around the monopiles.Stability number and size-selection equations for riprap armour layers are summarised and compared.Moreover,other alternative methods to riprap are briefly introduced and presented.A typical graph of the scour depth reduction with different collar sizes and elevations under specific test conditions is summarised and compared with a plot for a pile founded on a caisson.Reduction rates for different flow-altering countermeasures,including the collar,are listed and compared.A newly developed soil improvement method,namely microbially induced calcite precipitation(MICP),is also reviewed and introduced as a scour protection method.As a popular bio-soil treatment method,MICP has a good potential as a scour countermeasure method.Bio-soil treatment methods and traditional armouring methods are defined as active and passive soil enhancement scour countermeasures,respectively.

Discussion on Foundation of Offshore Wind Turbine

This paper briefly describes the classification and composition of offshore wind turbine foundation structure,and focuses on different structural forms of offshore wind turbine foundation.The advantages,disadvantages and application fields of offshore wind turbine foundations with different structures are compared and analyzed.Finally,some suggestions on the construction of offshore wind power foundation are put forward.

Circular and Faceted Monopile Installation Fatigue Damage

There are currently no models predicting localised stressing induced in monopole foundations resulting from pile driving installation. A scaled down test was conducted for both circular and faceted monopile, during which monopile stressing was measured. From the stress data gathered fatigue damage was estimated. Fatigue damage of the faceted geometry is significantly larger than that of the circular geometry. It is shown that in the worst case the fatigue damage incurred is still negligible compared to the full service life of the foundation. Suggestions for future developments are made, such developments can be helpful in providing greater understanding of the occasional cases where fatigue damage resulting from pile driving is not negligible and has perhaps resulted in failure.