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- Andreas P. J. Breu, H-M Ensner, Christof A Kruelle, Ingo Rehberg
- Physical review letters
- 2003

We report on experiments on vertically shaken binary granular mixtures, which separate into their components due to the external excitation. This well-known phenomenon, where large particles rise to the top of the mixture, is called the Brazil-nut effect. Recent theoretical findings predict also a reverse Brazil-nut effect, where large particles sink to the… (More)

- Sébastien Aumaître, Christof A Kruelle, Ingo Rehberg
- Physical review. E, Statistical, nonlinear, and…
- 2001

A segregation phenomenon in a horizontally vibrated monolayer of granular matter is studied experimentally. In a binary mixture of small spheres and larger disks, the collapse speed of the disks increases dramatically with increasing granular temperature. The scaling behavior can be understood by applying arguments from kinetic gas theory.

- Frank Gollwitzer, Ingo Rehberg, Christof A Kruelle, Kai Huang
- Physical review. E, Statistical, nonlinear, and…
- 2012

The influence of a liquid film on the coefficient of restitution (COR) is investigated experimentally by tracing freely falling particles bouncing on a wet surface. The dependence of the COR on the impact velocity and various properties of the particle and liquid is presented and discussed in terms of dimensionless numbers that characterize the interplay… (More)

- Christopher Groh, Andreas Wierschem, Nuri Aksel, Ingo Rehberg, Christof A Kruelle
- Physical review. E, Statistical, nonlinear, and…
- 2008

A well-defined two-dimensional single barchan dune under the force of a shearing water flow is investigated experimentally. From an initially prepared triangular heap a rapid relaxation to a steady-state solution is observed with constant mass, shape, and velocity. This attractor exhibits all characteristic features of barchan dunes found in nature, namely… (More)

- T Schnautz, Richard Brito, Christof A Kruelle, Ingo Rehberg
- Physical review letters
- 2005

Transport effects in a monolayer consisting of a binary granular mixture, confined in a horizontally vibrating circular dish, are studied experimentally and compared with a reduced theoretical model. Depending on the ratio of the particles' material density and size, migration of the larger particles occurs either towards the boundary or to the center of… (More)

- Anne-Marie Bétat, Christof A Kruelle, Vidar Frette, Ingo Rehberg
- The European physical journal. E, Soft matter
- 2002

The formation of sand ripples under water shear flow in a narrow annular channel and the approach of the ripple pattern towards a steady state were studied experimentally. Four results are obtained: i) The mean amplitude, the average drift velocity and the mean sediment transport rate of the evolving bed shape are strongly related. A quantitative… (More)

- Marina Montaine, Michael Heckel, Christof A Kruelle, Thomas Schwager, Thorsten Pöschel
- Physical review. E, Statistical, nonlinear, and…
- 2011

The coefficient of restitution of a spherical particle in contact with a flat plate is investigated as a function of the impact velocity. As an experimental observation we notice nontrivial (non-Gaussian) fluctuations of the measured values. For a fixed impact velocity, the probability density of the coefficient of restitution, p(ɛ), is formed by two… (More)

The dependence of the barchan dune dynamics on the size of the grains involved is investigated experimentally. Downsized barchan dune slices are observed in a narrow water flow tube. The relaxation time from an initial symmetric triangular heap towards an asymmetric shape attractor increases with dune mass and decreases with grain size. The dune velocity… (More)

A summary of results is presented from experiments in granular systems, which are excited by vertical and/or horizontal vibrations. The transitions between different dynamic states depend on internal properties of the granular system like the density of particles and on external parameters of the driving shakers. Characteristic for granular systems are such… (More)

- Andreas Wierschem, Christopher Groh, Ingo Rehberg, Nuri Aksel, Christof A Kruelle
- The European physical journal. E, Soft matter
- 2008

The formation of granular ripples under liquid shear flow in an annular channel is studied experimentally. The erodible granular bed is subject to weakly turbulent flows without a defined sharp boundary layer close to the granular bed. The flow field and the degree of turbulence is characterized quantitatively by using a particle image velocimeter and a… (More)