Turbulence characteristics of wall jet in heading face using a laser doppler anemometer

Wall jet in heading face has both mean and turbulence characteristics that makes it have replacement and mixing effects on the air flow field. Thus,wind fluctuations play critical roles in the transportation and diffusion of gas and dust,for example,dust suspension entirely depends on that effect. However,the available experimental data on the subject are rather limited due to the limitations of experimental equipment and its complexity. This paper studies the turbulence characteristics of wall jet in heading face. For this purpose,the authors carried out some measurements of instantaneous 3D velocity in experimental model by using a three-dimensional laser doppler anemometer. After that,the authors have studied the distribution and scale of the turbulence intensity that calculated from the experiment data based on the statistical theories of turbulence. The experimental results indicate that there are serious wind fluctuations not only in the jet zone but also in the recirculation zone affected by the return flow and the side walls. The turbulence intensity in three directions are anisotropy but in the same order. Besides,the authors noticed that turbulence intensity increases firstly and then decreases with the distance from the axis of the jet reached the recirculation zone where the turbulence intensity are closer to the magnitudes of the mean air velocity. According to the analysis,shear instability that caused by velocity gradient between the flow layer is an important factor to cause the violent turbulence. At last, the authors suggest that a full attention should be given to the fluctuation term in motion equations when a further study of ventilation efficiency and migration law of gas and dust in heading face is made by any means.