湍流射流中示踪粒子的跟随性数值模拟分析

Numerical Study on the Flow Tracking Capability of Tracer Particles in a Turbulent Jet

为了探究聚苯乙烯颗粒在射流场中的跟踪效果,采用大涡模拟(LES)方法求解射流流场,并与实验结果进行对比,以验证流场模型.定义了密度与水相同的5种不同粒径的虚拟颗粒,采用离散相模型(DPM)计算其运动轨迹,将其响应时间的理论分析结果与数值模拟结果进行对比,验证了DPM模型的准确性.随后对粒径范围为1~400μm的11种不同粒径的聚苯乙烯颗粒在一定雷诺数射流流场中的跟随特性进行了模拟计算,并与初始时刻相同位置的质点运动轨迹进行对比分析.结果表明,流场的复杂变化对颗粒的跟随性有很大影响,这表现在即使颗粒粒径很小时,颗粒与流场的速度依然存在一定偏差.在所研究工况下,粒径小于200μm的聚苯乙烯颗粒与水的速度偏差大部分在20%以内.

In order to study the tracking effect of polystyrene particles in a jet, the method of large eddy simulation （LES） was adopted to simulate the jet flow field and the results were compared with the experimental data to verify the numerical model. A kind of virtual particles with different sizes and the same density as water was defined. Through the calculation based on the discrete phase model （DPM）, the theoretical analysis on the responding time was adopted to compare with the results of numerical simulation to confirm the accuracy of DPM. The simulations were then performed for the flow tracking capability of the polystyrene particles with the size in the rangefrom 1 μm to 400 μm in the jet flow field with a certain Reynolds number. And the polystyreneparticles trajectories were compared with the trajectory of a massless that the complex flow field has a great influence on the flow tracking capability of particles. That is to say that even the particle size is very small,a certain speed deviation between the particles and fluid still exists. Besides, the speed deviation between the fluid and polystyrene particles with the size below 200 μm issmaller than 20%.