Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

► Some combination of mean flow and turbulent eddies provides solids suspension in stirred tanks. ► The solids suspension mechanism changes when the impeller geometry is changed. ► For a T/3 impeller the dominant mechanism is the turbulence. For a T/2 impeller, neither the turbulence nor the mean flow dominates, but both play a role. ► The T/3 impeller is more energy efficient, possibly because a single mechanism dominates.