Investigation of granular flow through a bottleneck: When does an obstacle increase the flow rate in an hourglass?


The question of how to improve the granular flow when it passes through a bottleneck has applications to industrial granular flow, traffic flow and escape dynamics under panic. Optimal plant design for the conveyance, transport and storage of powders and bulk solids is a challenge faced by nearly all industries, from powder coating to food, from nano-scale powders and pharmaceuticals to cement, coal and ore.


Dr Fernando Alonso-Marroquin

Research Location

Civil Engineering

Program Type



Empirical placement of inserts (obstacles) in silos before outlet openings to improve the flow regime and remove stagnant zones in silos has been utilized since the sixties. We have examined granular flow across a bottleneck and find that contrary to expectations, the flow rate of particulate materials across a bottleneck actually increases if an optimized obstacle is placed before it. We also confirm that the obstacle allows transition from funnel flow to uniform (mass) flow. The aim of this project is to further investigate this effect, and show who it depends on the particle shape and the shape of the obstacle, and to give a physical explanation by using conservation equations of granular flow and empirical relation from traffic flow and funnel flow.  This project will be developed in the Centre of Geotechnical Research, and it will be supported by experimental results provided by key European Researchers: Alvaro Ramirez, from Polytechnic University of Madrid, and Iker Zuriguel from the University of Navarra, Spain.

Additional Information

The PhD candidate is expected to have demonstrated skills in numerical modeling and software programming, strong background in physics and mathematics, and be interested in related areas of geo-mechanics.

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Traffic flow, silo flow, hopper flow, granular materials

Opportunity ID

The opportunity ID for this research opportunity is: 1092

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