Working Principle and Experimental Results for a Differential Phase-Doppler Technique

By replacing the two detectors of a standard phase-Doppler anemometer (PDA) with a charge coupled device (CCD) line scan sensor, the scattered light can be measured not only with high temporal but also with improved spatial resolution. Thereby, the quantity to be measured by PDA, the phase difference ΔΦ, can be determined as function of the elevation angle υ. This allows a statistical evaluation of the received signal and permits precise measurements of the size and velocity even of non-ideal solid particles with inhomogeneous composition, aspherical shape or rough surface. In this paper, the basis of data acquisition and evaluation is described. This is followed by experimental results for glass spheres with intact and defect surfaces and, for comparison, for water droplets. These results demonstrate the potential of this measuring device, described as a differential phase-Doppler anemometer (DPDA).