Experiments and visualizations established that the properties of granular convective flows are greatly influenced by the frictional interaction between granules and the walls of the container that holds them. When the frictional coupling of adjacent particles to the sidewalls is strong,
convection is rapid and highly organized, consisting of circulatory cells in which granules move down to the bottom along the sides and up to the surface throughout the central portion of the container. When the frictional coupling is weak, the convective flow is slow and asymmetric,
lacking obvious container-wide organization.