Session: 09-01-08: Offshore Wind Energy - Hydrodynamics 2

Paper Number: 105084

105084 - Cfd Investigation of the Iea Offshore 15 Mw Reference Wind Turbine Performance in Full Scale: A Temporal Discretization Analysis 

Due to the expansion of the wind energy market to offshore sites, a significant increase in the wind turbines power capacity was noticed in the past decade. The continuous raising in the wind turbines size leads to several design and manufacturing challenges, mainly due to the difficulties in perform experimental tests which may represent the physics of the device in its operating environment properly. In this regard, numerical simulations used to represent the wind turbine system, considering its geometry in full scale, became a valuable tool to assist the design process and performance analysis. This paper presents a Computational Fluid Dynamics (CFD) methodology used to perform blade-resolved simulations to predict the performance of the IEA 15 MW Offshore Reference Wind Turbine, with which we conduct an investigation on temporal discretization. The computational analyses were carried out employing the Finite Volume Method (FVM) implemented in the OpenFOAM software. For the same spatial discretization, the Unsteady Reynolds Averaged Navier-Stokes (URANS) k-w SST turbulence model was employed and three different Courant–Friedrichs–Lewy (CFL) numbers were tested to predict the rotor performance when it operates in optimal wind-power conversion efficiency, for a wind speed of 10 m/s at hub height. The power production, generated thrust, and distribution of forces along the blade span were calculated and compared against values obtained using the blade element momentum theory, implemented in OpenFAST. The capability of each CFL in capture the physics of the system was assessed considering the computational cost and accuracy of the results. Amongst the CFL numbers investigated, the results obtained with CFL equals to 1 and 2 presented similar behavior and satisfactory accuracy, while those obtained with CFL equal to 4 presented results with unsatisfactory accuracy. Both CFL 1 and 2 are sufficient for the temporal discretization in terms of the rotor performance. While with lower CFL such as 1, more detailed information regarding the flow field in the wake internal gradient region and the flow structures that detach along the blade span were noticed, with CFL equal to 2 a significant reduction in the computational demand was achieved. Therefore, for the cases being investigated in this paper we chose the CFL number equals to 2 as the best option, due to the good results accuracy and optimization of the use of the computational resources.

Presenting Author: Marielle De Oliveira University of São Paulo - Department of Mechanical Engineering

Presenting Author Biography: Marielle received the bachelor degree in Aerospace Engineering from the Federal University of Santa Catarina (2018) in Brazil, went to the University of Tokyo in Japan as a fellowship PhD student, and currently is a Ph.D. candidate at the University of São Paulo working with the open source FVM software OpenFOAM, performing numerical modeling of the VIV phenomenon under High Reynolds numbers. Offshore wind turbines considering the tower interference. Floating platforms for wind turbine applications and the coupled system of a floating offshore wind turbine.

Authors:

Marielle De Oliveira University of São Paulo - Department of Mechanical Engineering
Leandro Silva Delmar Systems
Rodolfo Puraca University of São Paulo - Department of Mechanical Engineering
Bruno Carmo University of São Paulo - Department of Mechanical Engineering