# Numerical Simulation and Parameter Optimization of Air Slide Based on CFD-DEM
## 3 Numerical Simulation of the Conveying Process
### Experimental Protocol  
The simulation experiment considered inlet air velocity, aperture ratio (porosity), and chute inclination angle as influencing factors. Single-factor experiments were first conducted to analyze the impact of each factor on conveying performance, followed by orthogonal tests to optimize within the set parameter ranges. The initial design parameters were as follows: an inlet air velocity v of 1.8 m/s, a permeable baffle with staggered circular holes (diameter: 1.5 mm, porosity \(\varphi\approx 50.61\%\)), and a chute inclination angle \(\theta\) of 7\({}^{\circ}\). The first set of simulation experiments took the inlet air velocity v as the variable, with values set at 1.4 m/s, 1.6 m/s, 1.8 m/s, and 2.0 m/s. The second set of simulation experiments used the porosity \(\varphi\) of the permeable baffle as the variable, with values set at 37.84%, 47.24%, 50.60%, and 58.13%. The third set of simulation experiments used the chute inclination angle \(\theta\) as the variable, with four test values of 5\({}^{\circ}\), 6\({}^{\circ}\), 7\({}^{\circ}\), and 8\({}^{\circ}\). The experimental section considered inlet air velocity and chute inclination angle as influencing factors. The input air velocity and inclination angle of the chute were adjusted, respectively, through fan speed regulation and spacer blocks, corresponding to simulated settings of 1.4 m/s, 1.6 m/s, 1.8 m/s, and 2.0 m/s for air velocity and 5\({}^{\circ}\), 6\({}^{\circ}\), 7\({}^{\circ}\), and 8\({}^{\circ}\) for inclination angle. The initial design parameters were as follows: an inlet air velocity v of 1.8 m/s, a permeable baffle with staggered circular holes (diameter: 9 mm, porosity \(\varphi\approx 50.61\%\)), and a chute inclination angle \(\theta\) of 7\({}^{\circ}\). The first set of experiments took the inlet air velocity v as the variable, with values set at 1.4 m/s, 1.6 m/s, 1.8 m/s, and 2.0 m/s. The second set of experiments used the chute inclination angle \(\theta\) as the variable, with four test values of 5\({}^{\circ}\), 6\({}^{\circ}\), 7\({}^{\circ}\), and 8\({}^{\circ}\). \[n_{\text{out}}=\frac{\sum\limits_{i=1}^{n}n_{i}}{n} \tag{2}\]  
\[\delta=\frac{n_{\text{out}}}{n_{\text{in}}} \tag{3}\]  
where \(n_{i}\) is the average mass flow rate of material at time \(i\); \(m_{i}\) is total particle mass within the statistical domain at time \(i\); \(t_{i}\) is transit time of particle cluster through the domain at time \(i\); \(s\) is length of the statistical domain; \(v_{i}\) is average particle velocity at time \(i\); \(n_{out}\) is output mass flow rate; \(n_{in}\) is input mass flow rate; and \(\delta\) is conveying ratio. The fluctuation of the material layer surface is an important indicator of the stability of fluidized flow in the reacting material. Smaller fluctuations indicate weaker interactions between particles and less turbulent airflow generated at the material layer surface, leading to more stable fluidized flow. Conversely, larger fluctuations result in significant dust dispersion, causing pollution. Using the fluctuation of the material layer surface as the second indicator, the maximum height of particle splashing and its average value within the statistical domain of the material layer surface are measured. The difference between these two values, denoted as h, represents the surface fluctuation. A smaller h indicates greater stability of the material layer. The fluctuation of the material layer surface is an important indicator of the stability of fluidized flow in the reacting material. Smaller fluctuations indicate weaker interactions between particles and less turbulent airflow generated at the material layer surface, leading to more stable fluidized flow. Conversely, larger fluctuations result in significant dust dispersion, causing pollution. Using the fluctuation of the material layer surface as the second indicator.