Effect of humidity on the static angle in granular systems

BINDA, L.; VIDALES, A. M.; UÑAC, R.; ROHT, Y. L.; GÓMEZ-ARRIARAN, I.; IPPOLITO, I.

Granular Matter

Springer

Año: 2021 vol. 23

1434-5021

The purpose of the present work is to study the influence of humidity effect on the static angle for single particles withdiverse sizes on surfaces with differing roughness. The aim is to provide information about the characteristics of cohesiveforces between grains and rough surfaces with different grain geometries. The study has an experimental part and it iscomplemented by Monte Carlo simulations (MCS) and an empirical formulation of the dependence of the critical angle ontwo important parameters of the problem. The experimental device consists of an inclined surface that allows studying theevolution of the static angle (Ɵs), that is, the angle at which a 50% percent of spheres are put in motion. Relative Humidity(RH) is controlled through hygroscopic salts saturated solutions. Values obtained at different humidity rates are compared.For the MCS, the balance of the moments applied to the particle and necessary for its destabilization are taken into accountas a basis for calculating the probabilities for movement. Simulations help to establish a fitting curve that is able to describethe complete set of results by correlating the fitting parameters with the surface roughness and the Bond number for theparticles. We determine that for systems with high humidity, the formation of liquid bridges between particles affects thestatic angle for the onset of movement and this angle decrease as the diameter of the spheres increases. The type of surfacehas an important role on the static angle values.