Tribocharging of granular materials flowing in grounded inclined tubes.

Granular materials charge as they flow through inclined tubes due to the triboelectric effect. This charging persists even when the tube is grounded and is influenced by the tube's angle. In this study, we demonstrate that the tribocharging of granular materials can be accurately replicated through numerical simulations using the patch model. Charge transfers occur between the grains and the tube from donor patches to acceptor patches, ensuring the tube does not retain charge to simulate grounded conditions. Interactions between the grains and the tube are modeled using the method of image charges. We conducted experiments to validate the numerical results. Our findings reveal that the density difference between donor patches on the grains and the tube determines the charge acquired by the granular materials. Additionally, we observed both in experiments and simulations that granular materials charge less with the tube when it is shorter or less tilted. We interpret the influence of the tube's angle and length using the patch model. This model offers valuable insights into the tribocharging mechanisms of various materials.