Verification of a Numerical Model of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Within OC5 Phase III

Abstract

The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (OC5) project, is validation of aero-hydro-servo-elastic simulation tools for offshore wind turbines (OWTs) through comparison of simulated results to the response data of physical systems. Phase III of the OC5 project analyzes the Senvion 5M wind turbine supported by the OWEC Quattropod from the alpha ventus offshore wind farm. This paper shows results of the verification of the OWT models (code-to-code comparison). A subsequent publication will focus on their validation (comparison of simulated results to measured physical system response data). Based on the available data, the participants of Phase III set up numerical models of the OWT in their simulation tools. It was necessary to verify and to tune these models. The verification and tuning were performed against an OWT model available at the University of Stuttgart – Stuttgart Wind Energy (SWE) and documentation provided by Senvion and OWEC Tower. A very good match was achieved between the results from the reference SWE model and models set up by OC5 Phase III participants.

Validation of Numerical Models of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Against Full-Scale Measurements Within OC5 Phase III

“…For the majority of the simulation results, the mean pitch angle is slightly larger than the measured one during the power production (45 to 50 s). This is caused by differences in blade aerodynamics between the tuned NREL 5-MW blades (utilized in OC5 Phase III) and the real Senvion 5M turbine, as explained by Popko [7]. The measured pitch angle during the shutdown increases linearly to 70 • from 50 up to 76 s, afterward it is kept constant for around 4 s, and then continues pitching to feather with a slightly higher rate.…”

“…A description of the numerical model of the OWT consisting of the rotor-nacelle assembly (RNA), the tower, the transition piece (TP), the jacket substructure (OWEC Quattropod), its foundation piles, and soil properties was set up at Fraunhofer IWES [8] based on the data provided by Senvion and OWEC Tower. The complexity of the OWT models was proven adequate for this validation task [7]. On the other hand, the models were relatively simple (load analysis level) to minimize the implementation effort and modeling errors in the simulation tools.…”

“…Therefore, it was also considered as a reference model for the verification of other numerical models prior to their validation in Phase III. The verification results of the models, which are used in the validation exercise presented in this paper, were published in a separate paper by Popko et al [7].…”

“…It should be noted that prior to the validation, all numerical OWT models were verified to fix modeling errors. Their verification was published in a separate paper by Popko et al [7]. The models were not calibrated to the data after the verification step.…”

Validation of Numerical Models of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Against Full-Scale Measurements Within OC5 Phase III

“…A description of the numerical model of the OWT consisting of the rotor-nacelle assembly (RNA), the tower, the transition piece (TP), the jacket substructure (OWEC Quattropod), its foundation piles, and soil properties was set up at Fraunhofer IWES 2 [8] based on the data provided by Senvion and OWEC Tower. The complexity of the OWT models was proven adequate for this validation task [7]. On the other hand, the models were relatively simple (load analysis level) to minimize the implementation effort and modeling errors in the simulation tools.…”