Channeling patterns and erosion in fluid flow over granular beds
When fluid flows across a granular substrate, shearing forces detach material from the interface and transport it downstream. Although erosion-deposition constitutes a central geomorphological process that shapes Earth’s landforms, decades of research has failed to yield a complete description of these systems at the microscopic level. Utilizing a flume apparatus to simulate river flow over a gravel bed, Pascale Aussillous et al. examine the threshold stress beyond which solid flow spontaneously arises and characterize the spatial organization of the erosion flux. The authorS show that near the origin of erosion the flow of particles is spatially heterogeneous, carried by only a few concentrated channels in the bed whose distribution is strongly power-law correlated in the along-flow direction. Furthermore, the authors demonstrate that these results support a model in which erosion is ultimately governed by a give and take between channelization, which accelerates erosion, and interactions among particles which tend to interfere with channeling. The findings argue that erosion along a fluid-sheared granular bed effectively represents a dynamic phase transition, consistent with other systems such as type II superconductors.
Work from the group of M. Lisa Manning to understand how glass transitions in tissues might impact cancer reseach was featured in Quanta magazine: https://www.quantamagazine.org/20160816-researchers-unpack-a-cellular-traffic-jam/
Two scientists affiliated with the collaboration, Pierfrancesco Urbani and Silvio Franz, are invited to present their work at the American Physical Society March Meeting in New Orleans. The symposium will focus on soft excitations in glasses and jammed solids, and also feature Emanuela Del Gado, Frances Hellman, and Mark Ediger.
In a work just published in Nature Physics G. Biroli and P. Urbani show that in amorphous solids standard elasticity theory breaks down. At low enough temperature or high enough pressure all non-linear elastic moduli diverge. Beyond this transition, the response to deformation becomes history and time-dependent.
arXiv preprint arXiv:1601.06724
Andrea Liu was elected to be a General Councilor for the APS. Her term starts on January 1, 2017.
Congratulations to Andrea Liu on her election to the National Academy of Sciences
Lisa Manning received the Young Scientist Award for 2016 in recognition of her outstanding statistical physics contributions to the fields of granular materials, jamming, and biological cell dynamics.