Time-domain delay-and-sum beamforming for time-reversal detection of intermittent acoustic sources in flows.
This study focuses on the identification of intermittent aeroacoustic sources in flows by using the time-domain beamforming technique. It is first shown that this technique can be seen as a time-reversal (TR) technique, working with approximate Green functions in the case of a shear flow. Some numerical experiments investigate the case of an array measurement of a generic acoustic pulse emitted in a wind-tunnel flow, with a realistic multi-arm spiral array. The results of the time-domain beamforming successfully match those given by a numerical TR technique over a wide range of flow speeds (reaching the transonic regime). It is shown how the results should be analyzed in a focusing plane parallel to the microphone array in order to estimate the location and emission time of the pulse source. An experimental application dealing with the aeroacoustic radiation of a bluff body in a wind-tunnel flow is also considered, and shows that some intermittent events can be clearly identified in the noise radiation. Time-domain beamforming is then an efficient tool for analyzing intermittent acoustic sources in flows, and is a computationally cheaper alternative to the numerical TR technique, which should be used for complex configurations where the Green function is not available.
Institut PPRIME UPR 3346, CNRS - Université de Poitiers - ENSMA, Bât. B17 - 6 rue Marcel Doré, 86022 Poitiers Cedex, France.
Ifanila
I
Rakotoarisoa
Institut PPRIME UPR 3346, CNRS - Université de Poitiers - ENSMA, Bât. B17 - 6 rue Marcel Doré, 86022 Poitiers Cedex, France.
Jeoffrey
J
Fischer
Institut PPRIME UPR 3346, CNRS - Université de Poitiers - ENSMA, Bât. B17 - 6 rue Marcel Doré, 86022 Poitiers Cedex, France.
Vincent
V
Valeau
Institut PPRIME UPR 3346, CNRS - Université de Poitiers - ENSMA, Bât. B17 - 6 rue Marcel Doré, 86022 Poitiers Cedex, France.
David
D
Marx
Institut PPRIME UPR 3346, CNRS - Université de Poitiers - ENSMA, Bât. B17 - 6 rue Marcel Doré, 86022 Poitiers Cedex, France.
Christian
C
Prax
Institut PPRIME UPR 3346, CNRS - Université de Poitiers - ENSMA, Bât. B17 - 6 rue Marcel Doré, 86022 Poitiers Cedex, France.
Laurent-Emmanuel
LE
Brizzi