Causality Correlation in Aeroacoustic Experiments by Means of Simultaneous PIV and Microphone-Array Measurements

Abstract

In this paper we present applications of the causality correlation technique by means of simultaneous PIV measurements in a turbulent flow and microphone-array measurements in the aeroacoustic far field of the flow. Both measurements were conducted in a synchronized manner so as to enable the calculation of the cross-correlation between the acoustic pressure and flow quantities derived from the measured velocity fluctuations. The main idea of the concept presented here is to use the coefficient matrix obtained from the aforementioned correlation to identify regularities in the near-field fluctuations that are related to the radiated sound field. The method is used for the identification of flow structures that are involved in the generation mechanism of aeroacoustic noise sources. Results for measurements on a Rod-Airfoil configuration with a strong tonal component in the acoustic far-field as well as for a cold jet with a broadband spectrum are presented.