Numerical Simulation Study on the Average Air Velocity Circle in Coal Mine Roadway

To determine the accurate installation position of the air velocity sensor and ensure that it monitors the average air velocity of the full section of the roadway, a numerical simulation method was employed. The results verified the existence of an average air velocity circle on the section of a fully developed turbulent roadway, where the air velocity at any point on it is equal to the average air velocity of the roadway, and its position is approximately fixed, independent of the size of the roadway air velocity. It revealed the rule that the distance from the top of the average air velocity circle to the roof of rectangle, semi-circular arch, and three-centered arch roadways with smooth walls is 0.11-0.12 times the height of the roadway. Through field tests, it was found that in real underground roadways, the distance from the average air velocity circle to the roof is greater than that in roadways with smooth walls. When installing air velocity sensor in real roadway, the installation position of the sensor should be adjusted appropriately based on the roughness of the roadway wall surface.