CAA based noise prediction for wind energy turbines

Abstract

Within the framework of the International Energy Agency Wind Technology Collaboration Programme (IEA Wind TCP) Task 39 (Quiet Wind Turbine Technology), a benchmark for wind turbine sound prediction was initiated [1]. DLR is involved in this work through the HGF (Helmholtz Association of German Research Centres) -funded projects ViSion (Validation of Simulation Tools for the Description of Wind Turbines) and LAiSA (Lastadaptive & Aeroakustische Analyse). The initial goal is to predict the turbulent trailing edge noise (TBLTEN) and the turbulent inflow noise (TIN) dominating the overall sound radiation for a 2.3 MW NM80 wind turbine and compare it with the results of the codes of the Task 39 participants as well as with measurements that have taken place in the EU project DAN-AERO MW [2]. The outcomes of Task 39 are recently published by Bertagnolio et al. [3]. A process chain, originally developed by Rautmann [4] is used, that breaks down the rotor into individual segments, for each of which 2D CAA (computational aeroacoustics) simulations are then performed. Here this tool chain was picked up and supplemented: The rotation of the rotor, the associated amplitude modulation and the variation of the distance to arbitrary evaluation points for the individual rotor blade sections are taken into account. The individual contributions to TBL-TEN and TIN of each blade segment of the entire rotor are finally summed up and averaged over the rotor revolution. In addition to, for example, the certification position according to IEC-64100-11 standard or arbitrary positions distributed in space can be specified as evaluation positions in order to examine noise signatures.