## 1 Introduction  
With the developments of economy, science, and technology, the world energy structure has changed and clean energies, such as solar energy and wind energy, are included in the new energy development strategy. Yet coal is still the most abundant and widely used energy source on the Earth [1; 2; 3]. In recent years, the safety of coal mine production has been improved and gradually stabilized, yet there are still a large number of coal mine accidents, among which coal fire accidents are most frequent [4; 5]. For a long time, coal fire has been one of the main hazards in underground coal mining workplaces, and the spontaneous combustion of residual coal in gob is the main contributor to coal fire [6; 7]. The main internal factor of coal spontaneous combustion is the spontaneous combustion propensity of coal, while the factor determining the spontaneous combustion propensity of coal is the coal petrographic composition [8; 9; 10]. Domestic and foreign scholars have proposed several methods to identify the spontaneous combustion propensity of coal based on different identification techniques. [PERSON] [11; 12] has tested and obtained the industrial analysis parameters of coal through corresponding identification techniques, and divided the spontaneous combustion propensity grade of coal. Coal fire is the most unpredictable hazard and most difficult to be controlled because it often occurs in the gob [13]. Therefore, how to quickly locate the coal spontaneous combustion in gob and accurately implement targeted measures is of great significance to ensure safe production in mines. To clearly identify the hazardous areas of spontaneous residual coal combustion, a field test method has been established by monitoring the gas distribution in the gob and the concept of \"three zones\", namely the heat dissipation zone, the oxidation zone, and the suffocation zone, is proposed. The division of the oxidation zone and suffocation zone using oxygen concentration can usually result in an accurate boundary. [PERSON] et al. [14] measured the oxygen concentration using buried tubes and determined the range of the gob spontaneous combustion \"three zones\" based on the oxygen concentration distribution and temperature rise. [PERSON] et al. [15] identified the range of spontaneous combustion \"three zones\" in the gob of a super long fully mechanized mining fac during the withdrawal based on oxygen concentration and the thickness of the floating coal. Due to certain limitations in on-site observation, CFD software has been widely used to characterize the flow field in coal seam gob. [PERSON] [16] studied the oxygen distribution in coal seam gob by combining CFD and field measurements and determined the spontaneous combustion hazardous areas. [PERSON] [17] thoroughly analyzed the gas seepage characteristics in the goal of a fully mechanized mining face with a U-shaped ventilation system through CFD software, determined the critical values of the seepage velocity and oxygen concentration in the goat, established a mathematical model for coal spontaneous combustion, and simulated and calculated the gas concentration index in the upper corner of the distribution of the spontaneous combustion hazard area in the goal, establishing a composite risk assessment model. [PERSON] [18] aimed at the impact of porosity and overlying rock fractures in the goat on the coal spontaneous combustion risk zone, taking Bulianta Coal Mine as the background, introduced the model into the FLUENT software, and conducted numerical simulation of the O\({}_{2}\) concentration field, CO concentration field, and wind speed field in the goat. The simulation results are in good agreement with the on-site measured data. [PERSON] [19] et al. quantitatively simulated gob porosity distribution from the microscopic point of view by the discrete element method (DEM) and wrote a user-defined function (UDF) code that was then substituted into CFD to simulate the gas distribution in gob. The results indicated that that gas was mainly distributed in the upper gob.