This equipment grant provides a Phase Doppler Particle Analyzer to conduct research which requires the simultaneous measurement of particle size and two components of velocity. The instrument is basically a two component, two color Laser Doppler Velocimeter which has been enhanced to perform particle size measurements. The device provides a diagnostic non-intrusive tool capable of making point measurements of particle size distribution and velocity. This equipment will be part of many thermal science projects including studies of heat and mass transfer in rotating systems, materials processing, non-Newtonian flows, fuel spray atomization and dispersion, spray ignition and combustion, sampling of fluid suspensions, and others. The ability to measure both particle size and velocity in such problems will enhance the understanding and development of the processes.