Experimental study on uncertainty mechanism of mine airvelocity and pressure with non-external disturbance

Fluctuations of mine air velocity and pressure are generally considered to be caused by external disturb- ances. But even if external disturbances are fully controlled in a lab environment,the indicated values of velocity and pressure still present irregular fluctuations which is known as uncertainty phenomenon. Mechanism which causes the uncertainty phenomenon was studied from the turbulent theory. Time-series data of air velocity and static pressure in a tunnel model were measured by laser dopper anemometer (LDA) and digital differential manometer. The results show that the fluctuations still exist in both magnitude and direction,which generally present a random fluctuation around an average value. The maximum pulsating amplitude of air velocity and pressure reach 1. 19 m / s and 4. 9 Pa respectively when their average values are 2. 57 m / s and 17. 1 Pa respectively. Both velocity and pressure fluctuation signals follow a normal distribution. Their average pulsating amplitudes are respectively proportional to velocity and its square,but the uncertainty phenomenon is only affected by turbulence intensity instead of velocity. Experiments show that mine air velocity and pressure are uncertainty even with non-external disturbances which is essentially caused by turbulence fluctuations. Yet,turbulence can be measured accurately because it has regular statistical average value. To get accu- rate parameters in the tunnel airflow the development of test instruments should be based on the statistical average val- ue of turbulence.