Experimental comparison between acoustic and pressure signals from a bubbling flow

Experiments were performed on both the acoustic and pressure signals produced by bubbles formed from an underwater nozzle. The data were analyzed by a comprehensive set of spectral and nonlinear-dynamical techniques. As air flow rates increase, it is well known that such flows became chaotic. However, the present study of both acoustic and pressure signals showed that chaos could appear in different regimes and was manifested in different ways in the acoustic and pressure signals. The use of different time delays for the chaotic analysis of acoustic and pressure signals were found necessary. The acoustic signals offer data primarily on the bubble size while the pressure signals offer data primarily on the bubble production rate. The present results suggest that chaos can appear in the bubble size and bubble production rate independently. (c) 2008 Elsevier Ltd. All rights reserved.