RESPONSE OF PHASE DOPPLER ANEMOMETER SYSTEMS TO NONSPHERICAL DROPLETS

The Phase Doppler Anemometer (PDA) technique measures particle diamete r assuming sphericity. A means for detecting nonsphericity has usually been implemented in commercial PDA systems to avoid sizing errors if the sphericity assumption is not valid. In the present research the re sponse of standard and planar PDA systems is examined experimentally i n more detail by passing nonspherical droplets of known shape through the measurement volume. The effectiveness of nonsphericity detection s chemes can be evaluated, and furthermore the influence of the droplet oscillations on the frequency and phase evolution of individual signal s can be quantified. The light scattering from such particles has been simulated by using geometric optics, and the computed response of sta ndard and planar PDA systems agrees well with the experimental observa tions. We conclude with some remarks concerning the possibilities of c haracterizing the nonsphericity with PDA systems. (C) 1998 Optical Soc iety of America.