Estimation of the average velocity of a fluid by means of a single modulated beam

We propose an optical method to estimate the average velocity of a liquid fluid circulating through a square pipe with transparent walls. The velocity is obtained from the photovoltage data measured in a semiconductor crystal when is illuminated with a single intensity modulated laser beam, transmitted through the pipe in a perpendicular direction of the moving fluid. Experimental results considering parameters as wavelength, modulation frequency, particles concentration and fluid speed were obtained, and a comparative statistical analysis considering additional measurements obtained by Laser Doppler Anemometry (LDA) as a reference, was performed too.