驻点流中的颗粒动力学

Particle dynamics in a stagnation point flow

驻点流中的颗粒动力学可见于化工管道输运、航空发动机叶片等,相应基础研究的开展是为了建立可预测的两相流模型。针对化工管道中的驻点流颗粒问题,采用颗粒解析的直接数值模拟方法,对颗粒动力学与流体动力学的耦合机理进行了研究。研究发现,单个有限尺寸中性颗粒在驻点流对称轴上的动力学非常反常:远离壁面的时候,无论颗粒的有限尺寸或惯性大小,颗粒动力学呈现示踪粒子行为;靠近壁面,示踪粒子行为不再成立。开发了可以自适应颗粒惯性并且可以反应真实物理材料特性的弹性碰撞模型。研究发现,颗粒相对携带流体的惯性是驻点流颗粒动力学的关键。加速/减速流场导致的无黏环境压力是产生反常的流体力驱动的颗粒非接触反弹现象的根本原因。

Stagnation point flows with particles are commonly found in chemical pipe transportation,rocket combustion chambers,and aeroengines,etc.The development of reliable predictive models for practical industrial problems requires full understanding of particle dynamics in such flows.Therefore,particle dynamics in a stagnation point flow was investigated by means of a Particle-Resolved Direct Numerical Simulation(PRDNS).It is found that the dynamics of a single finite-size neutrally-buoyant particle in a stagnation point flow is unusual.When the particle is far from the wall,it behaves as a fluid tracer,regardless of its finite size and inertia,while near the wall,such a fluid-tracer behavior disappears.A time-adaptive wet collision model reflecting real physical properties has been developed.The empirical parameter-tuning is not necessary for this model.Results indicate that the particle inertia is the crux of the particle-wall interaction,and that the inviscid ambient pressure,which is unique in stagnation point flows,plays a key role in the unusual contactless bouncing.