Simultaneous Measurement of Volocity and Size of Flowing Particles: (Detection of Phase Shift of Doppler Signals by Fast Digital Processor)

The present processing system was designed to measure size and velocity of particles in dense two-phase flows. A fast Fourier transform method was adopted to detect not only Doppler frequencies but also phase shifts of Doppler signals, where a particle size was proportional to the phase difference of Doppler signals observed by photodetectors at different positions. A fast digital signal processor was employed for the high speed calculation of FFT processing. The transmitting and receiving optical systems of the present LDV was constructed by fiber optics to stabilize and compact it. The present system provided a high accuracy in measurements of particle velocity and size for noisy signals.