# Numerical Simulation and Parameter Optimization of Air Slide Based on CFD-DEM
## 4 Experimental Results and Discussion  
### Single-Factor Analysis  
In the simulation, an inlet was positioned directly above the left end of the chute to introduce particles (Figure 6). The generated particles were released with zero initial velocity, allowing them to fall freely into the inclined chute. The chute was oriented at a specific inclination angle \(\theta\) relative to the horizontal plane. The particle size and physical parameters remained consistent with those described in previous sections. Figure 6: Simulation process diagram. 1. Particle inlet. 2. Particle outlet. The simulation process is illustrated in Figure 7. The conveying ratio of the air slide in both simulation and experiment and the oscillation amplitude obtained from simulation calculations are shown in Figure 8.  
As the input air velocity increased, the conveying ratio of the air slide improved accordingly, while the fluctuation difference in the material layer surface first increased and then decreased. This phenomenon occurs because, with higher input air velocities, the void fraction between particles increases, reducing interparticle interactions and increasing the average velocity of the particle group, thereby enhancing the conveying ratio. The material layer enters a bubbling bed stage similar to that in a fluidized bed, where the fluid tends to penetrate specific regions of the bed, causing surface particles to jump and resulting in significant fluctuation differences. As the input air velocity continues to rise, the material layer transitions from the bubbling bed stage to a stable phase, and surface fluctuations begin to diminish. Due to the simplified treatment of the experimental platform, there were certain discrepancies between the conveying ratios of the three types of flour in experiments and the simulation results, though their variation trends remained consistent. This can, to some extent, validate the reliability of the simulation model. Overall, the conveying ratio of the air slide exhibits a positive correlation with the input air velocity, whereas the influence of input air velocity on surface fluctuations is more complex. The simulation process is illustrated in Figure 9. Analysis of the experimental results (Figure 10) reveals that the conveying ratio of the air slide is negatively correlated with porosity, whereas the surface fluctuation difference in the material layer is positively correlated with porosity. Figure 8: Experimental results under changing wind conditions. (**a**) Effect on conveying ratio. (**b**) Effect on surface fluctuation. Figure 7: Simulation process diagram under varying wind speed. (**a**) Input wind speed: 1.4 m/s. (**b**) Input wind speed: 1.6 m/s. (**c**) Input wind speed: 1.8 m/s. (**d**) Input wind speed: 2.0 m/s. The underlying mechanism can be explained as follows: Since the input air velocity remains unchanged, the airflow velocity passing through the permeable layer decreases as porosity increases, leading to a decline in the conveying ratio. Meanwhile, the air velocity acting on the particles falls within the latter segment of Figure 8b. The variation in porosity results in a more uniform fluid distribution inside the air slide, causing a slight reduction in fluctuation amplitude. The simulation process is illustrated in Figure 11. Analysis of the experimental results (Figure 12) shows that as the inclination angle of the chute increases, the conveying ratio gradually improves, while the surface fluctuations of the material layer decrease. This occurs because the gravitational component of the material particles along the chute direction increases with the inclination angle, enhancing particle acceleration and velocity in that direction, thereby improving the conveying ratio. Figure 11: Simulation diagram under varying chute inclination angles. (**a**) The chute inclination angle: \(5^{\circ}\). (**b**) The chute inclination angle: \(6^{\circ}\). (**c**) The chute inclination angle: \(7^{\circ}\). (**d**) The chute inclination angle: \(8^{\circ}\).