This article is about characteristic velocity for a rotary drums. Rotary drums are used in many industrial processes for particulate materials. The research entered five various of the drum diameter - ranged from 300 to 700 mm. This paper includes analysis of results that have been carried out by research and calculated by the equations for the characteristics velocity. Applied method of research - DPIV (Digital Particle Image Velocimetry) - allows to determine the velocity field of filler particle and afford to designate the trajectory of its motion.