Published in Proceedings of the 2001 ASME Fluids Engineering Division Summer Meeting: New Orleans, LA, May 29, 2001, pages 85-91. Copyright 2001 American Society of Mechanical Engineers (ASME). Publisher website: http://store.asme.org/.
NOTE: At the time of publication, the author William Durgin was not yet affiliated with Cal Poly.
A study was conducted to examine how a coherent sound burst, such as those used in an ultrasonic flowmeter, crosses a turbulent flow field. Many ultrasonic flowmeters use a time of flight method to determine the mean flow. This measurement method sends sound waves at some angle across a velocity field between two transducers, and the time required for the sound burst to cross this distance is measured on the order of nanoseconds. The system then reverses so that the sound wave burst is sent in the opposite direction. Knowing the distance traveled, the local average sound speed, and the back and forth travel times, the integrated velocity along the sound path can be computed. By using average values for distance and time, an average flowrate may be determined. To perform this analysis, data from several velocity fields were used to determine how a coherent sound burst would travel across the field. Comparisons of the infinitely thin case and the finite thickness case are performed. The study focused on using a modified ray trace method on a velocity field data set obtained using PIV.