Origins of the reverse Janssen effect

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• The Janssen effect describes reduced pressure in granular materials compared to liquids.
• The reverse Janssen effect is a counterintuitive phenomenon where base force exceeds total weight.
• Understanding granular material behavior is crucial for various engineering applications.

Purpose of the Study:

• To investigate the reverse Janssen effect experimentally and computationally.
• To determine the influence of the pouring protocol on the reverse Janssen effect.
• To compare experimental findings with simulation results.

Main Methods:

• Experimental setup involving granular particle columns.
• Computational simulations of granular material behavior.
• Systematic variation of pouring height and flux parameters.

Main Results:

• The reverse Janssen effect is strongly dependent on the pouring protocol.
• Increased pouring height (tens of particle diameters) leads to a significantly stronger reverse Janssen effect.
• Pouring flux also influences the effect, though to a lesser extent.

Conclusions:

• The pouring protocol is a critical factor in the reverse Janssen effect.
• Experimental and computational results align, validating the understanding of the phenomenon.
• This study enhances the comprehension of granular physics and its comparison with liquid systems.