Determination of velocity profiles in pipes by a pulsed photoacoustic method

Abstract

The present work describes the development of a pulsed photoacoustic (PA) flowmeter. An acoustic wave in a flowing fluid is produced by absorption of a laser pulse focused over a path flow line. The acoustic propagations, along and against the flow, are monitored by two cw probe beams. In the interaction, the probe beam undergoes a transient deflection that is detected by a fast response photodiode (PD). Measurements of the acoustic arrival time through the pipe cross section are acquired. The velocity distribution data profile of a square pipe is obtained applying the cylindrical shockwave model developed by Vlasses and the velocity equation established in an earlier work by Zapka and Tam [9]. The profiles determined with this method are fixed through two turbulent pipe flow models, showing good agreement.