## 4 Flow Field Analysis of Corner-Filled Goaf Area Using ANSYS Fluent
### Simulation Analysis of Different Filling Interval Distances at the Corners of the Working Face  
A simulation study was carried out to investigate the optimal filling interval distance, building upon the analysis results from the preceding section. The study specifically targeted various filling interval distances for both the upper and lower corners of the working face. The simulated interval distances encompassed C4--10 m, C5--30 m, C6--50 m, and C7--70 m. The aim was to evaluate the impact of these diverse filling interval distances on the extent of the oxidation zone in the goat. Figure 14 displays the pressure distribution in the goat on the z = 1.5 m plane with varying intervals between the filling bodies. It is evident from Figure 14 that an increase in the interval distance between the filling bodies results in a reduction in pressure in the deeper parts of the goat. Specifically, with interval distances of 10 m, 30 m, and 50 m, the green range of the pressure contour lines (5-6 Pa) gradually diminishes, while the blue range (3-4 Pa) progressively expands. Additionally, when the interval distance reaches 50 m, the two pressure ranges become nearly identical, indicating a relatively balanced pressure field in the goat. However, with an interval distance of 70 m, the expanded  
Figure 12: Contour maps depicting the oxidation zone in the goat under different corner-filling conditions. Figure 13: Width of the oxidation zone in the goat under different corner-filling conditions. interval distance significantly increases the blue pressure zone of 2-3 Pa, amplifying the pressure difference between the return air side and the lower corner angle of the goat and resulting in a greater influx of air leakage into the goat. Furthermore, the presence of the two filling bodies on the return air side obstructs the movement of air leakage, causing its accumulation between the two filling bodies and adversely impacting the reduction in the width of the oxidation zone on the return air side. In conclusion, by increasing the spacing between the filling bodies, the pressure difference between the corner of the working face and the deep part of the goat is reduced. This effectively prevents the backflow of internal airflow to the upper corner angle, mitigating the risk of exceeding the gas limit in that area. Additionally, the secondary filling process makes it more challenging for air leakage from the lower corner angle to infiltrate the goal, leading to a decrease in air leakage and facilitating the management of the spontaneous combustion zone in the goat. Figure 15 presents the oxygen concentration distribution in the goat at z = 1.5 m with various interval distances between filling bodies. After the secondary interval filling of the two corners of the working face, a noticeable reduction in the width of the oxidation zone within the goat is observed. This reduction is attributed to the increased resistance encountered by the airflow from the intake side, hindering its entry into the goat and resulting in weakened airflow within the goat. Consequently, this decrease in airflow within a certain range contributes to a narrower oxidation zone within the goat, leading to improved control over air leakage from the working face and the oxidation zone. More detailed data on the width of the oxidation zone in the goat for different interval distances of filling bodies can be found in Table 4.  
Figure 16 presents a schematic diagram demonstrating the extent of the oxidation zone in the goat at various interval distances of filling bodies. It is evident from the figure that an increase in the interval distance, from primary filling to intervals of 10 m, 30 m, and 50 m, leads to a decrease in the average width of the oxidation zone within the goat. Interestingly, at an interval distance of 50 m, the oxidation zone width in different parts of the goat is the smallest.