A pilot plant gas atomizer was designed and assembled at the center of pyrometallurgy, University of Missouri--Rolla, to produce metal powders. The pilot plant utilizes a confined, annular, supersonic nozzle to yield spherical metal powders (aluminum and zinc alloys have been atomized) of average size of 15 um in diameter. A cold model of the atomizing nozzle was constructed to simulate the pilot plant. First, the high-speed gas flow was studied; later, modeling of the atomizing process was carried out by using water as the atomized liquid. This work has investigated the complex gas flow in the converging-diverging nozzle and around the metal flow insert tip to gain a physical understanding of the fluid dynamics of the process. Equipment was developed to utilize the schlieren technique for a small field of view (about 20 mm square). A number of different nozzle designs were constructed with special facilities for pressure measurement at different positions along the flow direction. The pressure measurements near the insert tip have been used to deduce flow parameters such as exit velocity, temperature, mach number, and the boundary layer thickness. These parameters can be used to estimate the resultant powder size. The tests using water showed that the envelope of gas flow close to the nozzle was not significantly affected by the presence of the liquid being atomized.