Rise time of inverted triangular prism intruder in vibrating granular bed: Experiments and model

Experiment results and a qualitative model of the phenomenon called Brazil nut effect (BNE) with inverted triangular prism are reported in this work. The model is constructed by considering some forces (earth gravitational force, buoyant force, and fluid viscous force) and using Newton's second law of motion. The rise time of BNE T is defined as time needed for the intruder to be on granular surface with all of his parts (no part is still immersed in the granular bed). One side of the triangular base of the intruder l is varied from 1.5 to 5 cm with other two sides are kept in constant values (1 and 3 cm). It has been observed in experiment that l with value 3-4 cm gives the smaller rise time. Plot of T versus l has the form of concave up parabolic curve with minimum lies at l between 3-4 cm. This observation has been confirmed by the proposed model with the same order of magnitude and similar curve trend.