Experiments on a thin layer of cohesive wet granular matter under vertical vibrations reveal kink separated domains that collide with the container at different phases. Due to the strong cohesion arising from the formation of liquid bridges between adjacent particles, the domains move collectively upon vibrations. Depending on the periodicity of this collective motion, the kink fronts may propagate, couple with each other and form rotating spiral patterns in the case of period tripling, or stay as standing wave patterns in the case of period doubling. Moreover, both patterns may coexist with granular 'gas bubbles' -phase separation into a liquidlike and a gaslike state. Stability diagrams for the instabilities measured with various granular layer mass m and container height H are presented. The onsets for both types of patterns and their dependency on m and H can be quantitatively captured with a model considering the granular layer as a single particle colliding completely inelastically with the container.

The magnetic field of a cuboidal cluster of eight magnetic spheres is measured. It decays with the inverse seventh power of the distance. This corresponds formally to a multipole named a dotriacontapole. This strong decay is explained on the basis of dipole-dipole interaction and the symmetry of the ensuing ground state of the cuboidal cluster. A method to build such dotriacontapoles is provided.

The coupling of two rotating spherical magnets is investigated experimentally, with particular emphasis on those motions where the driven magnet follows the driving one with a uniform angular speed, which is a feature of the so called cogging free couplings. The experiment makes use of standard equipment and digital image processing. The theory for these couplings is based on fundamental dipole-dipole interactions with analytically accessible solutions. Technical applications of this kind of coupling are foreseeable particularly for small machines, an advantage which also comes handy for classroom demonstrations of this feature of the fundamental concept of dipoledipole coupling.

Due to the opacity of most granular materials, it is often desirable to have three dimensional (3D) particle tracking techniques beyond optical imaging to explore granular dynamics. Using inertial measurement units (IMU) embedded in a projectile, we obtain the trajectory of projectile impacting on a granular medium under microgravity using tri-axial acceleration and angular velocity data. In addition to the standard algorithm for reconstruction, we emphasize solutions to various sources of error to determine projectile trajectory accurately.

We investigate experimentally the dynamics of a single polygonal disk (regular n-gon with 3 ⩽ n ⩽ 8) confined in a closed container under vertical vibrations against gravity. The disks tend to precess continuously upon vibrations, transferring mechanical energy into rotational and lateral translational degrees of freedom (DoF). An analysis of the velocity distribution functions in both DoF suggests that the mobility in both DoF are coupled with each other, exhibiting a characteristic angular velocity that depends on confinement and disk shape. The characteristic angular velocity can be captured with an analytical model considering sustainable precession due to continuous driving. Depending on confinement, translational and rotational kinetic energy fluctuations within one vibration cycle can be synchronized with each other and there exists a regime where injected energy is equally distributed in different DoF. Depending on n, the tendency for the disk to precess varies and there exists a regime (n ⩽ 6) where persistent rotation of the disk rarely lasts longer than one vibration period. Our results suggest the possibility of tuning energy injection into different DoF in vibrated granular disk mono-layers via shape design and confinement.