Advanced CFD-MBS coupling to assess low-frequency emissions from wind turbines

Abstract

Abstract. The low-frequency emissions from a generic 5 MW turbine are investigated numerically. In order to regard airborne noise and structure-borne noise simultaneously a process chain was developed. It considers fluid-structure coupling (FSC) of a computational fluid dynamics (CFD) solver and multibody simulations (MBS) solver as well as a Ffowcs Williams-Hawkings (FW-H) acoustic solver. The approach was applied to a generic 5 MW turbine to get more insight into the sources and mechanisms of low-frequency emissions from wind turbines. For this purpose simulations with increasing complexity in terms of considered components in the CFD model, degrees of freedom in the structural model and inflow in the CFD model were conducted. Consistent with literature, it has been found that aeroacoustic low-frequency emission is dominated by the blade-passing frequency harmonics. The tower base loads, which excite seismic emission, tend to be dominated by structural eigenfrequencies with increasing complexity of the model. The main source of aeroacoustic emissions is the blade-tower interaction and the contribution of the tower as an acoustic emitter is stronger than the contribution of the rotor. Aerodynamic tower loads also significantly contribute to the external excitation acting on the structure of the wind turbine.

Aero-elastic analysis of wind turbines under turbulent inflow conditions

“…In order to allow the communication between FLOWer and SIMPACK, moving, undeformed and reference system markers need to be defined as prescribed in (Klein et al (2018)). In the present study no controller is taken into account, that is why each simulation is conducted with a fixed rotational speed and pitch.…”

“…In section 2 the high-fidelity framework (as presented in Klein et al (2018)) is described for fluid-structure interaction coupled simulations on the NM80 2MW wind turbine rotor, also known as DANAERO rotor, (DANAERO). Additionally the inflow conditions and setup for the different cases are listed.…”

Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

“…Thereby, the movements of the different components are realized with the overset grid technique (Benek et al, 1986). At the authors' institute, FLOWer is continuously developed to improve simulation capabilities of rotary wings, including high-order schemes (Kowarsch et al, 2013), advanced turbulence modeling (Weihing et al, 2016), fluid structure interaction (Sayed et al, 2016;Klein et al, 2018), wake modeling (Weihing et al, 2017) and optimization for high-performance computing (Letzgus et al, 2018). The code has been extensively validated for wind turbine flows during the MexNext projects, providing accurate predictions of loads and wake measurements (Schepers et al, 2012;Boorsma et al, 2018).…”