Transition of steady air flow into an anharmonic acoustic pulsed flow in a prototype reactor column: Experimental results and mathematical modeling

Abstract

A prototype experimental setup is designed to convert steady air flow into an oscillatory anharmonic acoustic pulsed flow, under special experimental conditions. The steady flow in a cylindrical reactor column of 3 m height and 15 cm in diameter with a porous layer, transforms itself abruptly into an oscillatory acoustic pulsed flow. Experimental results show the existence of a threshold for flow-rate, beyond which this transformation into anharmonic oscillatory flow takes place. This change in flow regime is analogous to the phenomenon of bifurcation in a chaotic system, with abrupt change from one energy state into another. Experimental results show that the acoustic oscillations amplitude depends on system size. Preliminary mathematical model will be presented that includes; relaxation oscillations, non-equilibrium thermodynamics, and Joule-Thomson effect. The frequencies at peak amplitude for the acoustic vibrations in the reactor column are expressed in terms of flow-rate, pressure-drop, viscosity, and dimensionless characteristic numbers of the air flow in the system.