Qualitative Investigation of Wake Composition in Offshore Wind Turbines: A Combined Computational and Statistical Analysis of Inner and Outer Blade Sections

¹ Department of Mechanical Engineering and Technology Management, Norwegian University of Life Sciences, Drøbakveien 31, 1432, Ås, Norway
² Department of Mechanical Engineering, University of Bahrain, Bahrain
³ Division of Energy and Sustainability, Cranfield University, UK
⁴ Abu Dhabi Maritime Academy, Abu Dhabi P.O. Box 54477, United Arab Emirates
⁵ Department of Mechanical, Electronics and Chemical Engineering, Oslo Metropolitan University, Norway

^* Corresponding author: muhammad.salman.siddiqui@nmbu.no

Abstract

High-fidelity numerical simulations are used to thoroughly analyze the evolution of the wake behind a megawatt-scale offshore wind turbine. The wake features are classified in terms of wake dynamics composition and the associated turbulence characteristics originating from the inner and outer sections of the blades. Understanding the wake is essential for developing compact layouts for future wind farms. We employed a transient Sliding Mesh Interface (SMI) technique to analyze the fully dynamic wake evolution of the offshore NREL 5MW full turbine. Our high-fidelity results have been validated against previously published results in the literature. We thoroughly investigated the dominant structures of the wake using Proper Orthogonal Decomposition (POD) techniques, which we applied to transient simulations of fully developed flows after five wind turbine revolutions over the snapshot data. Our findings show that the inner section of the blades, which is composed of airfoils with larger cross-sections, is responsible for the dominant components of the wake, while the contribution of the wake from the outer section of the blade is significantly lower. Therefore, designing more aerodynamic sections for the blade’s inner section can help reduce the dominant wake components and thus decrease the inter-turbine distance in future wind farms.