Acoustic investigation of rod vortex generators on a wind turbine rotor

Purpose: This paper aims to investigate the acoustic impact of the rod vortex generator (RVG) on the noise emitted by the National Renewable Energy Laboratory Phase VI wind turbine rotor operating at off-design conditions.

Design/methodology/approach: An assessment of the impact of RVGs on the rotational far-field noise emission is conducted for the rotor with/without RVGs using an in-house aeroacoustic code based on the Ffowcs-Williams Hawkings acoustic analogy (FW–H). The influence of RVGs on the trailing-edge far-field separation noise analysis is conducted using the Amiet-Schlinker theory for rotating bodies.

Findings: Results show that the RVGs do not significantly impact the rotational noise emission. They do increase the broadband noise emitted in the higher frequency range. They reduce flow separation through the streamwise vortices generated, increasing aerodynamic performance. However, this leads to increased pressure fluctuations thus shifting peak pressure signals toward higher frequencies. There is an increase of ∼2 dB at the off-plane microphone locations.

Originality/value: RVGs have been successfully investigated for turbulent boundary layer separation control. However, studies on their impact on sound emission are limited. Although the aeroacoustic tools (based on FW–H and Amiet’s theory) are not new, their application to investigate the acoustic impact of RVGs on a wind turbine rotor is original.