Particle shape dependent energy dissipation behaviour of granular dampers with circular toroid particles

The energy dissipation effectiveness of a granular damper shows high performance in two motional phases. It is shown that particle shape affects one of these phases, the bouncing bed. A parallel study using experiments and Discrete Element Method simulations involving circular toroidal particles is used to evaluate the effect of particle shape on the non-linear energy dissipation over a wide range of excitation frequencies and amplitudes. The results show that the excitation amplitude that provides optimum bouncing-bed performance can be increased above that for spherical particles using high-sphericity toroidal ones. Further deviations in shape (reducing sphericity) reduce this level below that for spheres. This behaviour is related to the packing density achieved and hence the clearance in the enclosure. While small spheres can achieve random close packing and slight deviation in shape allows denser arrangements, large shape deviations can reduce the packing density significantly. For the other motional phase, fluidisation, which occurs at lower amplitudes, particle shape does not have a significant effect. This is attributed to the motional behaviour that involves compaction and decompaction every cycle and is dominated by local interactions at the contact points between individual particles.