Intermittent dry granular flow in a vertical pipe

Density waves in dry granular media falling through a vertical pipe.

We report experimental measurements of density waves in granular materials flowing down in a capillary tube. The density wave regime occurs at intermediate flow rates between a low density free fall regime and a high compactness slower flow. We observe this intermediate state when the ratio of the tube diameter and the particles size lies between 6 and 30. The propagation velocity of the waves ...

Intermittent flow of a collection of rigid frictional disks in a vertical pipe.

We study the quasistatic flow of a collection of rigid frictional disks pushed upward (against the gravity) inside a narrow vertical pipe by a compliant mechanism. The contact dynamics method was used for the numerical simulations in combination with a friction law at disk-disk and wall-disk contacts characterized by discontinuous velocity weakening from a static threshold to a dynamic coeffici...

Interaction between dry granular flow and deflectors

The application of seawall deflectors for reflecting inviscid waves into the sea have been well established. Recently, rigid barrier deflectors have been proposed prescriptively for mitigating geophysical landslides, but flow characteristics differ fundamentally from waves and merit investigation. In this study, flume tests were used to calibrate a discrete element model to explore the interact...

Optimizing naturally driven air flow in a vertical pipe by changing the intensity and location of the wall heat flux

Heat transfer from the internal surfaces of a vertical pipe to the adjacent air gives rise to the air flow establishment within the pipe. With the aim of optimizing the convective air flow rate in a vertical pipe, the details of the flow and thermal fields were investigated in the present study. Conservation equations of mass, momentum, and energy were solved numerically using simple implicit f...

Stability, Avalanches, and Flow in Dry and Wet Granular Materials