  We study the order-disorder transition of horizontally swirled dry and wet
granular disks by means of computer simulations. Our systematic investigation
of the local order formation as a function of amplitude and period of the
external driving force shows that a large cluster of hexagonally ordered
particles forms for both dry and wet granular particles at intermediate driving
energies. Disordered states are found at small and large driving energies. Wet
granular particles reach a higher degree of local hexagonal order, with respect
to the dry case. For both cases we report a qualitative phase diagram showing
the amount of local order at different state points. Furthermore we find that
the transition from hexagonal order to a disordered state is characterised by
the appearance of particles with square local order.
