Computational studies on Darrieus VAWT noise mechanisms employing a high order DDES model

The aerodynamic and aeroacoustic behaviors of the Darrieus vertical axis wind turbine are very complicated. Hence, it is challenging to simulate the real flow behavior using the computational fluid dynamics approach. In the present study, the behavior of two different numerical techniques, Unsteady Reynolds Averaged Navier Stokes and Delayed Detached-Eddy Simulation (DDES), are compared to predict the aerodynamic and aeroacoustic performance. The DDES approach with the higher order scheme is used to investigate the noise mechanisms of Darrieus VAWT at several operating conditions. It is concluded that the dominant noise mechanism, when the turbine operates at low and high speed ratios, is a dipole noise, without any contribution from the monopole sound in the time averaged signal. Moreover, all the blade segments along the chord have a significant contribution to noise production. The leading edge segment is responsible for the noise reflects the load fluctuations by the variation of the effective angle of attack, flow blade relative velocity, and Blade vortex interaction. On the other hand, the rest of the blade segments reflect the load fluctuations by the massively separated flow at low speed ratio, while at high speed ratio it is as the same as the leading edge. (C) 2019 Elsevier Ltd. All rights reserved.