A two-dimensional discrete element method was used to model the development of single-cell bulk circulation in vibratory beds that had both vertical and horizontal components of motion. The model predictions were compared with experimental measurements of the growth of bulk circulation in beds of steel and glass spheres as a function of bed depth, friction coefficients and the amplitude of vibration. The trends predicted by the model matched those in the experiments. The experimental observations were explained in terms of the resultant shear forces predicted at the vibrating container walls. (C) 2011 Elsevier B.V. All rights reserved.