推导了气粒两相流中颗粒所见流场速度的滤波密度函数(FDF,filtered density function)输运方程,建立稀相气粒多相流的LES/FDF模型并对气粒两相平面尾迹流动中颗粒的湍流扩散进行了数值模拟研究.将模拟的结果与实验数据及不使用FDF模型得出的结果进行对比,说明LES/FDF模型能够更好地描述颗粒的空间扩散.
An LES/FDF model was developed by the authors to investigate the SGS effect on the particle motion in the gas-particle two-phase plane wake flow.The simulation results of dispersion rate for different particles were compared with the results without using the FDF model.It was shown that the large eddy structure is the dominant factor influencing the particle diffu-sion in space for small particles(small Stokes-number particles),but for intermediate or large diameter particles,the influence of the sub-grid scale eddies on the dispersion rate is in the same order as that of the large eddies.The sub-grid scale eddies increase the particle dispersion rate in most time,but sometimes they decrease the dispersion rate.The sub-grid scale particle dispersion rate is decided not only by the intensity of sub-grid scale eddies and the Stokes number of the particles,but also by the large eddy structure of the flow field.For the particles in isotropic turbulence,the dispersion rate decreases as the particle diameter increases.
JIN HanHui1,CHEN SuTao1,CHEN LiHua1 & FAN JianRen2 1 School of Aeronautics and Astronautics,Zhejiang University,Hangzhou 310027,China
The time-dependent variation of airborne particle concentration for different sizes in a test chamber was numerically predicted with drift-flux model. The performance of the drift-flux model for particle transport in different kinds of airflow fields was analyzed. The results show the drift-flux model can predict the transport of indoor fine particles reasonably well. When the air flow field varies slowly, the model can predict both the time-dependent variation ratio of the particle concentration and final stable concentration very well, and the difference for particles with different sizes can be also well predicted. When the air flow varies drastically, the accuracy of the model is decreased due to the neglect of the particles’ independent convective terms in the air flow.
