The measurement of complex intensity near the open end of a flanged cylindrical pipe

Jevgenija Prisutova , Kirill Horoshenkov

The measurement of acoustic intensity assumes taking the time average of the energy flow and treating the intensity as a real quantity. However, one may extract additional information if the intensity is viewed as a complex quantity which contains information about the local mean energy flow and local energy oscillations. In this paper experiments are reported using a tri-axial Microflown intensity probe to measure the complex instantaneous intensity near the open end of a flanged pipe. The measurements are then used to quantify the energy travelling out of the pipe and the energy oscillating back and forth inside the pipe. This has a potential significance for acoustic detection of structural and operational conditions inside the pipe as one would expect oscillating energy to be increased and travelling energy to be decreased in the presence of a cross-sectional change. These experiments are carried out in the high frequency range to show the interaction between a plane wave and the first circumferential mode. Here, the amplitude of the circumferential mode is found to be strongly related to the relative position of the source in the pipe, and the complex intensity is seen to change in transverse as well as the axial direction.

Domaines: Acoustique [physics.class-ph]

Jevgenija Prisutova, Kirill Horoshenkov. The measurement of complex intensity near the open end of a flanged cylindrical pipe. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811111⟩