Data Driven Modal Decomposition of the Wake Behind an NREL 5-MW Wind Turbine

Authors

Giovanni De Cillis - Politecnico di Bari
Stefania Cherubini - Politecnico di Bari
Onofrio Semeraro - LIMSI,CNRS, Univerité de Paris-Saclay,
Stefano Leonardi - University of Texas at Dallas
Pietro De Palma - Politecnico di Bari

Abstract

The wake produced by a utility-scale wind turbine invested by a laminar, uniform inflow is analyzed. The turbine considered is the NREL 5-MW at tip-speed ratio λ = 7. Its size leads to a diameter-based Reynolds number of the order of 108. The flow is simulated through a Large Eddy Simulation, where the forces exerted by the blades are modeled using the Actuator Line Method, whereas tower and nacelle are modeled employing an Immersed Boundary Method. The wake flow is analyzed using both Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition in its sparsity-promoting variant (SP-DMD). The main flow structures identified by both techniques are compared, and significant differences emerged, which can be of great importance for the formulation ofa reduced-order model.