Measurement techniques for aeroacoustics: from aerodynamic comparisons to aeroacoustic assimilations

Abstract

Sustainability has encouraged studies focusing on lowering the aeroacoustic impact of new aerodynamically optimized mechanical systems for several applications in wind energy, aviation, automotive and urban air mobility. The deployment of effective noise reduction strategies start with a deep understanding of the underlying mechanisms of noise generation. To elucidate the physics behind the formation of aerodynamic sources of sound, experimental techniques used for aerodynamic purposes have been combined with acoustic measurements. In the last decades, new experimental post processing techniques have additionally been developed, by leveraging aeroacoustic analogies in a new multi disciplinary framework. New approaches have been developed with the intent of translating near field velocity and pressure information into sound. The current review describes how such breakthroughs have been achieved, briefly starting from an historical overview, to quickly bridge to the measurement techniques and the facilities employed by the scientific community. Being the measurement principles already reported in literature, this review only focuses on the most relevant studies trying to relate near field information to the perceived sound in the far field. Aspects related to the uncertainty of the measurement techniques will be thus very briefly discussed, together with their relation to the background noise of the testing facilities, including acoustic reflections/refractions, and issues due to installation of the instrumentation.

Experimental Study on the Noise Evolution of a Horizontal Axis Icing Wind Turbine Based on a Small Microphone Array

“…The aerodynamic noise can be classified into the turbulent boundary layer trailing-edge noise, separation stall noise, laminar boundary layer vortex shedding noise, blunt trailing-edge noise, blade tip vortex noise, etc. [12][13][14][15]. Many experts and scholars have conducted a lot of research work on wind turbine noise source identification and noise source sound pressure spectrum distribution.…”