The role of the hopper angle in silos: experimental and CFD analysis

In this work, we reported experimental and numerical results of granular flows in silos and hoppers. We used a very flexible experimental setup, allowing us to explore the entire domain of the hopper angles. In addition, the granular flow was also studied numerically using Computational Fluid Dynamics. First, the numerical protocol was validated, comparing the output with experimental data of mass flow rate. In general, we obtained a good quantitative agreement between numerical and experimental results using a single set of the model parameters. Remarkably, the numerical results reproduced very well the weak non-monotonic behavior of the mass flow rate dependence on the hopper angle obtained experimentally. Stepping forward, we examined the scaling properties of the simulated velocity v(r) and density $$\phi (r)$$ profiles at the outlet region. Finally, we also analyzed the velocity and volume fraction field inside the silo. The outcomes suggested that fast dynamics at orifice perturbs the system distinctly, depending on the hopper angle. Interestingly, small and large angles showed a larger zone of influence in comparison with intermediate angles.