Rotating-drum experiments for particle-laden flows: a new view.

Shear in the annular space between drums is a well-known model for particle-laden flows. When this technique was introduced by Bagnold, it was assumed that the shear rate and particle concentration were uniform within the annular space. It is now known that this is not generally the case, in part because the distribution of particles in the annulus is influenced by hydrodynamic lift, which is discussed in the paper. The shear stress attributable to solids is also found to be influenced by different boundary conditions, and all these factors affect the usefulness of drum experiments for predicting other flow configurations. [ABSTRACT FROM AUTHOR]