Positioning Of Average Wind Speed Circle On Tunnel Cross-sections And Improving Wind Measurement Accuracy Technology

The intelligent construction of mine ventilation system is an important component of future smart mine construction.Accurate measurement of ventilation parameters such as tunnel wind speed and pressure is an important prerequisite for ensuring the safety of mine ventilation system and achieving intelligent ventilation system.The existing methods for measuring wind speed in tunnels are difficult to meet the accuracy requirements of mines’ intelligent construction.To address the above issues,this article adopts methods such as theoretical analysis,numerical simulation,and on-site experiments to study the distribution of wind speed on the tunnel cross-sections,determine the measurement position of average wind speed on the tunnel cross-sections,and improve the accuracy of wind speed measurement results.The main achievements are as follows:(1)Explored the influencing factors of the average wind speed circle of the tunnel cross-sections.Based on the Ludwig Prandtl mixing length theory and the hydraulics open channel flow theory,the mathematical model of the average wind speed circle position on typical tunnel cross-sections such as rectangular,trapezoidal,and semicircular arches is established by theory carding and derivation.The study indicates that the position of the average wind speed circle on the tunnel cross-sections is mainly related to the roughness of the wall and the size of the tunnel.(2)Studied the distribution pattern of wind speed on typical tunnel cross-sections under different working conditions.The distribution characteristics of wind speed on the tunnel cross-sections under 20 working conditions were obtained through numerical simulation,and the results showed that: The distance for the fully developed airflow in the tunnel is about 52 times the equivalent diameter of the cross-section.After the airflow is fully developed,the inlet wind speed will not affect the position of the average wind speed circle of the cross-section;The wind speed contour lines of the tunnel crosssections are basically parallel to the tunnel wall,and the wind speed contour lines are densely distributed near the wall;The distance between the average wind speed line and the boundary length increases with the increase of the aspect ratio and roughness height of the cross-sections,and the point wind speed increases in a logarithmic function with the increase of the distance from the tunnel boundary.(3)The distribution pattern of average wind speed point on tunnel cross-sections is studied.Selecting the return tunnel of working face 1305 of Caiyuan Coal Mine in Yulin City as the on-site wind speed measurement location.The average wind speed measurement position of the tunnel cross-section was studied using the wind speed contour lines and the wind speed distribution law on the axis of the cross-section,the results indicate that: There is a difference in the roughness of the two sides and the top and bottom walls of the tunnel,resulting in an asymmetric distribution of wind speed on the cross-section;The single point wind measurement value at a distance of 0.15 m from the roof on the mid high line on the experimental tunnel cross-section can be used as the average wind speed value of the tunnel.(4)The accuracy of wind speed measurement results has been improved based on uncertainty theory.Using adaptive Monte Carlo algorithm to improve the accuracy of wind speed measurement results on tunnel cross-sections,the results show that: The airflow in the tunnel has a random pulsation characteristic.As the wind speed in the tunnel increases,the distribution range of wind speed measurement results expands,and the data stability gradually decreases;The adaptive Monte Carlo algorithm not only preserves a large amount of original data information,but also integrates wind speed information and environmental information during the optimization process of measurement results,so data processing is more scientific and accurate.The research results are helpful to improve the accuracy of wind speed measurement on the whole cross-sections.