A fibre forming smectic twist-bent liquid crystalline phase

We demonstrate the nanostructure and filament formation of a novel liquid crystal phase of a dimeric mesogen below the twist–bend nematic phase. The new fibre-forming phase is distinguished by a short-correlated smectic order combined with an additional nanoscale periodicity that is not associated with density modulation

The role of the particle aspect ratio in the discharge of a narrow silo

The time evolution of silo discharge is investigated for different granular materials made of spherical or elongated grains in laboratory experiments and with discrete element model (DEM) calculations. For spherical grains, we confirm the widely known typical behavior with constant discharge rate (except for initial and final transients). For elongated particles with aspect ratios between 2 ⩽ L/d ⩽ 6.1, we find a peculiar flow rate increase for larger orifices before the end of the discharge process. While the flow field is practically homogeneous for spherical grains, it has strong gradients for elongated particles with a fast-flowing region in the middle of the silo surrounded by a stagnant zone. For large enough orifice sizes, the flow rate increase is connected with a suppression of the stagnant zone, resulting in an increase in both the packing fraction and flow velocity near the silo outlet within a certain parameter range

Silo outflow of soft frictionless spheres

Outflow of granular materials from silos is a remarkably complex physical phenomenon that has been extensively studied with simple objects like monodisperse hard disks in two dimensions (2D) and hard spheres in 2D and 3D. For those materials, empirical equations were found that describe the discharge characteristics. Softness adds qualitatively new features to the dynamics and to the character of the flow. We report a study of the outflow of soft, practically frictionless hydrogel spheres from a quasi-2D bin. Prominent features are intermittent clogs, peculiar flow fields in the container and a pronounced dependence of the flow rate and clogging statistics on the container fill height. The latter is a consequence of the ineffectiveness of Janssen's law: the pressure at the bottom of a bin containing hydrogel spheres grows linearly with the fill height

Design and Development of the Observation and Analysis of Smectic Islands in Space Experiment

The primary objective of Observation and Analysis of Smectic Islands in Space (OASIS) experiment is to exploit the unique characteristics of freely suspended liquid crystals in a microgravity environment to advance the understanding of fluid state physic

The role of the particle aspect ratio in the discharge of a narrow silo

The time evolution of silo discharge is investigated for different granular materials made of spherical or elongated grains in laboratory experiments and with discrete element model (DEM) calculations. For spherical grains, we confirm the widely known typical behavior with constant discharge rate (except for initial and final transients). For elongated particles with aspect ratios between 2 < L/d < 6.1, we find a peculiar flow rate increase for larger orifices before the end of the discharge process. While the flow field is practically homogeneous for spherical grains, it has strong gradients for elongated particles with a fast-flowing region in the middle of the silo surrounded by a stagnant zone. For large enough orifice sizes, the flow rate increase is connected with a suppression of the stagnant zone, resulting in an increase in both the packing fraction and flow velocity near the silo outlet within a certain parameter range

The role of the particle aspect ratio in the discharge of a narrow silo

The time evolution of silo discharge is investigated for different granular materials made of spherical or elongated grains in laboratory experiments and with discrete element model (DEM) calculations. For spherical grains, we confirm the widely known typical behavior with constant discharge rate (except for initial and final transients). For elongated particles with aspect ratios between 2 < L/d < 6.1, we find a peculiar flow rate increase for larger orifices before the end of the discharge process. While the flow field is practically homogeneous for spherical grains, it has strong gradients for elongated particles with a fast-flowing region in the middle of the silo surrounded by a stagnant zone. For large enough orifice sizes, the flow rate increase is connected with a suppression of the stagnant zone, resulting in an increase in both the packing fraction and flow velocity near the silo outlet within a certain parameter range

Visualization of Thin Liquid Crystal Bubbles in Microgravity

The Observation and Analysis of Smectic Islands in Space (OASIS) experiment exploits the unique characteristics of freely suspended liquid crystals in a microgravity environment to advance the understanding of fluid state physics

Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition

We present structural studies of a dimeric compound composed of a central heptyl spacer linking two mesogens consisiting of terphenyl units at which two adjacent fluoro groups are attached to each central ring. The terminal rings are linked to pentyl chains as terminal groups. The material exhibits a nematic-nematic transition and a low temperature modulated phase. The higher temperature nematic phase was found to exhibit an anomaly of the bend elastic constant similar to that of the dimers with N-Ntb phase sequence, and the physical properties of the low-temperature nematic phase are similar to those of the known Ntb materials. The structure of the low-temperature modulated smectic/columnar phase is described together with its ability to form freely suspended films and fibres. The relation of the modulated structure to the fibre formation and to the appearance of the labyrinthine instability in freely-suspended films is discussed

Linking bottleneck clogging with flow kinematics in granular materials: the role of silo width

We demonstrate experimentally that clogging in a silo correlates with some features of the particle velocities in the outlet proximities. This finding, that links the formation of clogs with a kinematic property of the system, is obtained by looking at the effect that the position of the lateral walls of the silo has on the flow and clogging behavior. Surprisingly, the avalanche size depends nonmonotonically on the distance of the outlet from the lateral walls. Apart from evidencing the relevance of a parameter that has been traditionally overlooked in bottleneck flow, this nonmonotonicity supposes a benchmark with which to explore the correlation of clogging probability with different variables within the system. Among these, we find that the velocity of the particles above the outlet and their fluctuations seem to be behind the nonmonotonicity in the avalanche size versus wall distance curve