Experimental study on wind speed distribution of the straight roadway and sudden enlarged sections based on LDA

Wind speed distribution is a fundamental basis for calculating the migration of gas,gas fire,dust,tempera- ture,humidity,heat and mass transfer processes within the underground roadway. It also plays a significant role in the arrangement of wind speed sensors and the development of wind instruments. In order to overcome the limitations of traditional contact instantaneous velocity measurement methods,a non-contact technology of LDA is used to test the steady flow in underground roadway and the airflow state at a sudden enlarged section. Under an average wind speed of 4 m / s,it can determine the extreme turbulence pulsations in the wind speed. With steady flow in the straight roadway, the average pulsation amplitude reaches 33% of average speed. The velocity vector and its direction display a normal Gaussian distribution. A large eddy can form in the sudden enlarged area with highly irregular airflow fluctuating around 0. 1-0. 2 m / s. This suggests that the turbulence vortex area can be neglected when considering airflow during the process. Affected by the sudden enlargement,the roadway wind speed resembles the distribution of equal dynamic wavy lines rather than the quasi parabolic distribution. The thickness of the boundary layer of the experimental roadway with smooth surface is about 5 mm with the wind speed reaching the mean value via a transitional “mutation”. Experi- ments show that the traditional measurement principle and method of wind can only satisfy the needs of general re- quirements,but can not meet the other computing requirements,such as gas,gas fire,movement rules of dust,tempera- ture and humidity distribution,and heat and mass transfer process under turbulent conditions in underground roadway.