A CFD Analysis of Ocean Destratification by Monopile Wind Turbine Foundations
Comparing Regular and Perforated Designs
R.J. Lip (TU Delft - Civil Engineering & Geosciences)
O. Colomés – Mentor (TU Delft - Offshore Engineering)
T. Raaijmakers – Mentor (TU Delft - Delft University Wind energy research institute)
Wim Uijttewaal – Mentor (TU Delft - Environmental Fluid Mechanics)
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Abstract
As offshore wind energy expands, the environmental impact of monopile foundations on ocean stratification has become a growing concern. Thermal stratification occurs when layers of seawater with different temperatures form due to solar heating, creating a stable density gradient that limits vertical mixing. However, monopile-induced turbulence can disrupt this layering, a process known as destratification, which may have significant ecological consequences.
This study investigates a novel perforated monopile design as a potential solution to mitigate these effects. Using Computational Fluid Dynamics (CFD) simulations in OpenFOAM, the research compares the hydrodynamic behavior of regular and perforated monopiles, focusing on turbulence intensity, wake formation, and destratification rates.
The results indicate that perforated monopiles reduce turbulence intensity and modify wake dynamics compared to regular monopiles, by allowing partial water flow through the structure and reducing recirculation zones. However, their impact on destratification rates remains minor. While perforations alter hydrodynamic behavior, they do not significantly mitigate stratification breakdown.
These findings suggest that while perforated monopiles influence flow dynamics, their effectiveness in reducing destratification is not significant enough to definitely recommend these structural modifications. Future research should explore different perforation patterns and other alternatives develop more sustainable offshore wind turbine foundations.