# Study on Airflow Field Distribution and Dust Distribution Characteristics at Blast Piles
## 3 Results and Discussion
### Dust Dispersion Distribution Patterns at Blast Piles  
#### 3.3.1 Dust Transport and Dispersion Patterns at Stationary Blast Piles  
To analyze the concentration change process of dust on a single blasting pile platform, three observation time points are selected: 50 s from the start of dust generation, 300 s at the middle of dust generation, and 600 s before the end of the experiment. The changes in dust concentration are shown in Figure 14.  
Figure 14: Cloud map of dust concentration variations (Red: Large particle size; Green: Medium particle size; Blue: Small particle size).  
By comparing the following three sets of figures, it can be observed that as the inlet wind speed increases, both the concentration of dust and the affected range decrease. The diffusion paths of dust differ depending on whether the inlet has wind or not. Without wind, dust is influenced by gravity and weak wind flow, diffusing downward along the slope of the platform. With wind, dust spreads upward along the slope of the platform, then diffuses from the upper platform towards the outlet. When the inlet wind speed is 0 m/s, at time t = 50 s, the dust begins to generate and accumulate on the dust-generating surface; at t = 300 s, when dust can spread downward to the outlet of wind flow direction, the concentration of dust increases, at t = 600 s, the affected area further expands. When the inlet wind speed is 1 m/s, at time t = 50 s, dust has spread upward along the slope in the direction of wind flow; at t = 300 s, dust has already spread to the fluid domain's outlet, increasing in concentration; at t = 600 s, the affected area further expands. When the inlet wind speed is 3 m/s, at times t = 50 s, 300 s, and 600 s, the dust diffusion pattern remains consistent but the concentration and affected area are much smaller than those at the other two different wind speeds. This indicates that for a single blasting pile platform, the higher the inlet wind speed is, the easier for dust to be expelled.  
To explore the spatial movement trajectories of dust particles of different sizes at different wind speeds, the same three time points, 50 s, 300 s, and 600 s, are selected and the trajectories of dust movement are shown in Figure 15.  
As shown in Figure 15, when the inlet wind speed is 0 m/s, at time t = 50 s the large red particles settle near the dust-generating surface; at time t = 300 s, medium green and  
Figure 15: Dust particles variations.  
small blue particles in size move along with the wind flow and most of the green particles in medium size also settle along the way; at time t = 600 s, only blue particles smaller in size continue to move forward. This indicates that when the wind speed is very low till 0, small particles can move out of the blasting pile platform only while other particle sizes mostly settle around the platform. When the inlet wind speed is 1 m/s and 3 m/s, at time t = 50 s, dust particles move upward along the slope under the impact of the wind flow; some large red particles settle along the way, while other medium-sized green particles remain in the air. At a wind speed of 1 m/s, more medium green particles are present, at a wind speed of 3 m/s, more large red particles are present. This suggests that when the wind speed reaches 3 m/s, particles under 24 m in diameter can be lifted by the wind flow and expelled out of the blasting pile platform. The affected area of dust gradually expands over time and due to the vortex near the ground on the top platform, some dust particles accumulate and then form dust clusters while others continue to move towards the outlet of the fluid field.