Flow patterns in agitated vessels There are three principal currents in the vessel during agitation: (a) radial (perpendicular to the shaft) (b) tangential (tangential to the circular path) (c) longitudinal (parallel to the shaft) Radia! Longitudinal Swirling   (Fig. 40d) Notes: Tangential component induces vortex and swirling, which in turn create stratification responsible for non–uniform mixing. In such case fluid particles are followed by another fluid particle. At relatively higher rpm, the center of vortex may reach impeller and air may be sucked in. This may not be desirable. Swirling can be minimized by placing the shaft slightly away from the center of the vessel, or by putting baffles. In the latter–configuration, tangential streamlines will also be reduced.