HIGH-RESOLUTION LASER DOPPLER VELOCITY MEASUREMENT OF BIDIRECTIONAL PULSATILE FLUID FLOW

A laser Doppler heterodyning system has been developed for localized measurement of the magnitude and direction of time-varying fluid flow velocity. Directional sensitivity is achieved by shifting the frequency of the reference laser beam by an acoustical diffraction cell. A Doppler frequency shift proportional to fluid flow velocity is obtained by heterodyning the scattered laser light with a frequency-shifted reference laser beam. Experimental results for time-varying flow velocity in perturbed flow sections are presented.