We study fully developed, steady granular flows confined between parallel flat frictional sidewalls using numerical simulations and experiments. Above a critical rate, sidewall friction stabilizes the underlying heap at an inclination larger than the angle of repose. The shear rate is constant and independent of inclination over much of the flowing layer. In the direction normal to the free surface, the solid volume fraction increases on a scale equal to half the flowing layer depth. Beneath a critical depth at which internal friction is invariant, grains exhibit creeping and intermittent cage motion similar to that in glasses, causing gradual weakening of friction at the walls.
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http://dx.doi.org/10.1103/PhysRevLett.101.248002 | DOI Listing |
J Morphol
January 2025
Department of Biology, Gonzaga University, Spokane, Washington, USA.
For over a century researchers have marveled at the square-shaped toe tips of several species of climbing salamanders (genus Aneides), speculating about the function of large blood sinuses therein. Wandering salamanders (Aneides vagrans) have been reported to exhibit exquisite locomotor control while climbing, jumping, and gliding high (88 m) within the redwood canopy; however, a detailed investigation of their digital vascular system has yet to be conducted. Here, we describe the vascular and osteological structure of, and blood circulation through, the distal regions of the toes of A.
View Article and Find Full Text PDFMaterials (Basel)
December 2024
Huanjiang Laboratory, Zhuji 311800, China.
Flexible fibers, such as biomass particles and glass fibers, are critical raw materials in the energy and composites industries. Assemblies of the fibers show strong interlocking, non-Newtonian and compressible flows, intermittent avalanches, and high energy dissipation rates due to their elongation and flexibility. Conventional mechanical theories developed for regular granular materials, such as dry sands and pharmaceutical powders, are often unsuitable for modeling flexible fibers, which exhibit more complex mechanical behaviors.
View Article and Find Full Text PDFInt J Pharm
December 2024
Department of Chemical Engineering, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai, China. Electronic address:
The study of the flow properties of particles is crucial because it directly impacts the efficiency and product quality of various industrial particulate processes, such as continuous manufacturing of solid oral dosages. However, challenges arise due to the flow behavior of cohesive particles, which tend to adhere to surfaces or other particles, necessitating careful process design. The importance of selecting appropriate measurement pathways for accurate characterization has been overlooked.
View Article and Find Full Text PDFSci Rep
November 2024
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences (CAS), Chengdu, 610041, China.
Phys Rev E
October 2024
State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China.
Granular materials in nature are nearly always nonspherical, but particle shape effects in granular flow remain largely elusive. This study uses discrete element method simulations to investigate how elongated particle shapes affect the mobility of dense granular flows down a rough incline. For a range of systematically varied particle length-to-diameter aspect ratios (AR), we run simulations with various flow thicknesses h and slope angles θ to extract the well-known h_{stop}(θ) curves (below which the flow ceases) and the Fr-h/h_{stop} relations following Pouliquen's approach, where Fr=u/sqrt[gh] is the Froude number, u is the mean flow velocity, and g is the gravitational acceleration.
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