The video beside shows the wall friction induced convection in a monolayer of cohesionless dry spheres. Together with Andrea Fortini from Surrey/UK, we investigate how topological defects inside influence the onset of convection, combining molecular dynamic simulations and experiments.

We found that wall-induced convection starts before the granular bed starts to melt ( in the bouncing-bed regime where the granular layer moves together as a single object. Moreover, the topological defects inside the initial packing of particles influence strongly the onset of convection. The next step questions are:

• How to modify the boundary condition to control convections?

• How does wetting liquid play the role?

• How does convection influence melting?