Aeroacoustics of Darrieus Wind Turbine

Abstract

The objective of this paper is to validate two different numerical methods for noise prediction of the H-Darrieus wind turbine using a complementary approach consisting of experimental measurements and numerical simulations. The acoustic measurements of a model scale rotor were performed in an anechoic wind tunnel. This data is the basis for the validation of the computational aeroacoustic simulations. Thereby, we have applied two different numerical schemes for noise prediction using hybrid methods. As usual in hybrid aeroacoustic approaches, flow field and acoustic calculations are carried out in separate software packages. For both schemes the time-dependent turbulent flow field is solved with Scale-Adaptive Simulation. The two schemes then differ in how the location of the acoustic sources and their propagation is calculated. In the first scheme the acoustic source terms are computed according to Lighthill's acoustic analogy which gives source terms located on the original CFD grid. These source terms are projected onto a coarser acoustic grid on which Lighthill's inhomogenous wave equation is solved by the Finite Element (FE) method. The second scheme uses the Ffowcs WilliamsHawkings (FW-H) method which is based on a free field Green's function. The scheme uses a porous integration surface and implements an advanced time formulation. Both methodologies are compared with experimental data.

A review of H-Darrieus wind turbine aerodynamic research

“…The first wind tunnel research programmes for VAWT applications were used to obtain the turbine's characteristic operating curves as the basis for machine design under various steady wind conditions. For example, Mazarbhuiya et al 155 investigated a turbine's performance using different asymmetric blades with a focus on the influence of blade aspect ratio whilst specialist facilities enable the breadth of experimentation to be expanded as exemplified by Weber et al 156 who studied turbine noise in the wind tunnel with a 1/2-inch free-field microphones. They showed that the main sources of the H-Darrieus sound pressure field were the separation-stall and the blade vortex interaction.…”

Insights into the Aeroacoustic Noise Generation for Vertical Axis Turbines in Close Proximity

“…Figure 5 shows the sound pressure level spectrum for the isolated VAWT at a microphone placed 1 m downstream the axis of the turbine (see Figure 6a for the microphone location). We compare our simulations (black) to experimental data (red), which is extracted from [23]. Comparable experiments for similar VAWT can be found in [22].…”

“…The experiments were performed in the anechoic closed return (with an open test section) wind tunnel at the University of Erlangen-Nurnberg, which has a low turbulence level of 0.15%, see [23] for details. Our simulations use the flow conditions detailed in Table 1, which correspond to the "Full-scale" conditions detailed in [23]. Figure 5a illustrates the good agreement obtained between our simulations and the experiments.…”

Location of aerodynamic noise sources from a 200 kW vertical-axis wind turbine

“…Both studies indicate lower noise levels compared to HAWTs. The VAWT noise studies based on 2D CFD setups were presented in [16,17], the latter including experimental validation using a small VAWT at very low TSR. In [18], noise predictions using a semi-three-dimensional large-eddy simulation were performed, and [19] used an unsteady three-dimensional (3D) inviscid panel method to predict parts of the noise spectrum.…”