Laser Doppler velocimetry and computer automation to measure low velocities in a pulmonary model

Laser Doppler measurements of the velocity field in a channel simulating pulmonary flows, characterized by a large range of velocities extending on the low side, are presented. A technique using a computer-controlled spectrum analyzer for the low velocities and a conventional period counter for the higher ones is discussed. The aim of the study is to determine the characteristics of a laminar, three-dimensional, steady flow at low Reynolds number in one bifurcation. The computer automation of measurements developed to overcome the complexity of the control of the measurement technique and the large number of measurement points necessary to characterize the flow in the bifurcation is described. Very good accuracy is obtained, and both measurement methods give extremely coherent results