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Material flow in a rectangular quasi-two-dimensional silo discharging simultaneously through two orifices has been investigated. A number of variations of the proximity of the sidewall of the silo with an individual orifice and the distance between the two orifices have been tried. It has been observed that beyond a certain distance between the two orifices, a neutral axis parallel to the axes of the orifices can be identified. The neutral axis divides the flow field in the silo between two non-interfering zones each of which is created due to the flow through a single orifice. Flow field created by a single orifice on the other hand depends on its proximity to the sidewall. Based on the above observation, an extension of the kinematic model for material discharge through a single orifice has been extended for predicting the velocity field during simultaneous discharge through two orifices. Based on the distance between two orifices, the limitation of this model has also been predicted.

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A comprehensive investigation of granular discharge through the eccentric opening of rectangular silos has been presented. Slip flow of the grains over the vertical wall closer to the orifice was observed experimentally. This has not been emphasized by the earlier researchers. Considering slip flow at the wall, the kinematic model of granular discharge has been extended to simulate the hydrodynamics during drainage through any eccentric opening. The simulation is applicable over the entire range of eccentricity possible and for both the uniform and the triangular velocity profile through the orifice. Results from the experiments using sand grains (300–500 μm) and glass beads (400–600 μm) have been used for validating the model. The excellent agreement not only justifies the application of the kinematic model for eccentric discharge, it also extends the model for irregular and much smaller grain size. Finally, some limitations of the kinematic model have been examined critically. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1439–1453, 2016

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The article discusses the response of rapid granular downslope flow to an abrupt change in basal friction. Although granular discharge from silo and hoppers has received considerable attention in the past, the flow behavior for an abrupt change in basal friction is hitherto unexplored. In the present study, the channel floor comprises of a smooth surface (bed friction angle—δS) and a rough surface (bed friction angle—δR) such that the angle of repose of the granular material (θr) lies between δS and δR and the flow features are observed as the channel inclination (θ) is varied from ≈δS to >δR. Experiments are performed in two channels with different extent of rough surface for two grain sizes with the same angle of repose and different inlet depth of granular flow. The visualization studies reveal a rich variety of flow features namely moving bore, rapid granular flow, flying avalanche and granular jump. Natural granular jump formed by mere frictional dissipation without any external forcing has not been reported earlier. The variety of flow features primarily results from the interplay of downslope motion of variable depth, collision‐driven piling of grains, and slope shaving avalanches. The observed flow phenomena have been satisfactorily analyzed by the well‐known depth‐averaged avalanche flow equations under conditions of incompressible granular flow.

We tested both real and model branches of four local tree species in a wind tunnel, for wind speeds up to 20 m/s. The model branches were same-size replicas of the real branches obtained via photogrammetry and 3D-printed or CNC-machined. Real leaves were attached to the models in approximately similar configuration. After comparing the streamwise force, drag coefficient (based on initial frontal area) and streamwise deflection, we found that the models exhibited similar trends to that of the real branches. Although not identical in value, the measurements for the model branches were similar in magnitude to the real branches. In particular, the drag coefficients appeared to approach very similar plateaus. We believe the differences in streamwise force and deflection to be due to the plastic used for the models, as well as perhaps how the leaves were attached to the models. We thus consider these physical models to be generally feasible for studying tree branches.

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