Analysis of the Angle of Maximal Stability and Flow Regime Transitions in Different Proportions of Bi-phasic Granular Matter Mixtures

This study investigates the dependence of the critical angle $\theta $c of stability on different mass ratios $\gamma $ of layered bi-phasic granular matter mixtures and on the critical angle of its mono-disperse individual components. It also aims to investigate and explain regime transitions of granular matter flowing down a tilted rough inclined plane. Critical angles and flow regimes for a bi-phasic mixture of sago spheres and bi-phasic pepper mixture of fine powder and rough spheres were observed and measured using video analysis. The critical angles $\theta_{\mathrm{c\thinspace MD}}$ of mono-disperse granular matter and $\theta_{\mathrm{c\thinspace BP}}$ of biphasic granular matter mixtures were observed and compared. All types of flow regimes and a supramaximal critical angle of stability exist at mass ratio $\gamma \quad =$ 0.5 for all biphasic granular matter mixtures. The $\theta_{\mathrm{c\thinspace BP\thinspace }}$of sago spheres was higher than the $\theta_{\mathrm{c\thinspace MD}}$ of sago spheres. Moreover, the $\theta_{\mathrm{c\thinspace BP}}$ of the pepper mixture was in between the $\theta_{\mathrm{c\thinspace MD}}$ of fine pepper and $\theta_{\mathrm{c\thinspace MD}}$ of rough pepper spheres. Comparison of different granular material shows that $\theta_{\mathrm{c\thinspace MD}}$ is not simply a function of particle diameter but of particle roughness as well. Results point to a superposition mechanism of the critical angles of biphasic sphere mixtures.