Multi-Physical Simulation Toolchain for the Prediction of Acoustic Emissions of Direct Drive Wind Turbines

Abstract

To address the acoustic behaviour of wind turbines, particularly tonalities, in an early design stage, accurate simulation toolchains have to be developed. In this work a novel simulation approach for the prediction of tonalities of direct drive wind turbines is presented. Comprehensive work is carried out in the fields of electromagnetic force excitation, structural sound transfer and radiation as well as airborne sound propagation. The developed methods are combined to a simulation toolchain to formulate a multi-physical system model of a direct drive wind turbine in order to predict tonal sound behaviour. These methods will be presented and discussed in detail in the course of this work. First, the approach, integrating the electromagnetic airgap forces of the large generator into a multi body simulation model of the mechanical turbine, is explained and validated with test bench measurements. Following, the modeling of the respective mbs is presented which calculates the resulting surface velocities. This model is solved in the time domain to account for the interaction between the external loads that are highly nonlinear and low-frequency and the high-frequency excitation forces of the generator. Subsequently, the methods for calculating the airborne sound emission in the vincinity of the turbine resulting from the surface velocities are discussed.