Characterization of base roughness for granular chute flows

Area of Science:

• Physics
• Engineering
• Geology

Background:

• Base roughness significantly impacts granular flow dynamics but lacks precise quantification methods.
• Existing models often overlook key geometric factors like particle size ratios and base packing arrangements.

Purpose of the Study:

• To propose and validate a new, generalized definition of base roughness (Ra) for granular flows.
• To establish a predictive relationship between base roughness and slip/nonslip conditions in granular chutes.
• To identify critical roughness values for designing nonslip granular bases.

Main Methods:

• Developed a novel definition of base roughness (Ra) incorporating size ratio and particle distribution.
• Generalized the Ra definition for both random and regular multilayered sphere packings.
• Applied the Ra definition to 2D and 3D granular chute flow simulations.

Main Results:

• The proposed base roughness (Ra) definition successfully predicts slip occurrence in granular chute flows.
• A clear transition from slip to nonslip conditions was observed as Ra increased.
• Critical Ra values were determined for achieving nonslip bases across different inclination angles.

Conclusions:

• The new Ra definition offers a quantifiable metric for base roughness in granular flows.
• Base roughness is a critical factor controlling slip behavior, with predictable transitions.
• This work provides practical insights for engineering nonslip granular surfaces.