Air-fluctuation nozzle and its periodic, wave-like air distribution evaluation

In order to investigate dynamic characteristics of fluctuating air, one kind of nozzles of producing periodical fluctuating air is presented in this paper. Assume that the jet is isothermal and free, the typical parameters of the airflow characteristics, such as the maximum jet velocity decay, the non-dimensional velocity profile on different sections and the turbulence intensity have been discussed. In addition, power spectrum density of experimental data was calculated and analysed. The result shows that compared with stable air supply, the fluctuating air velocity decay is slower, thus forming a more uniform velocity field. Furthermore, turbulence intensity of the fluctuating air is larger. The power spectrum density exponent value approaches to the value of typical natural wind when the air velocity decreases to 0.6 m/s. With airflow diffusion, the fluctuation characteristic of airflow changes to that of natural wind gradually.