Viscoelastic microfluidics has become a new trend for particle/cell manipulation in recent years. The coupling of fluid viscoelasticity and inertia has been proved to be effective for achieving particle elasto-inertial focusing at the channel centerline experimentally, which is important for downstream particle counting and detection. However, the mechanism of particle elasto-inertial focusing in viscoelastic flow is still unclear. This paper systematically explores particle elasto-inertial focusing in straight microchannels through using numerical simulation. The performance of particle focusing is studied under various control parameters. Numerical simulation is conducted under different Reynolds numbers Re, Weissenberg numbers Wi and particle diameters d to elucidate the force competition mechanisms. The results show that the increase of flow intensity and particle diameter d can speed up the focusing migration. Elasticity of the flow quantified by Wi can attenuate the particle rotation and thus weaken the lateral particle focusing towards the channel centerline. The separatrix for particle focusing towards the channel centerline or the channel walls is observed in the simulation. The results provide new insight into understanding particle elasto-inertial focusing in viscoelastic flows, and can be useful for guiding the design of viscoelastic microfluidics.

近年来，粘弹性微流体已经成为粒子/细胞操纵的新趋势。流体粘弹性和惯性的耦合已被证明对于通过实验实现通道中心线处的粒子弹惯性聚焦是有效的，这对于下游粒子计数和检测很重要。然而，粘弹性流中颗粒弹惯性聚焦的机理仍不清楚。本文通过数值模拟系统地探索了在直线微通道中的粒子弹惯性聚焦。在各种控制参数下研究了粒子聚焦性能。在不同的雷诺数Re，魏森伯格数Wi和粒径d下进行数值模拟阐明部队竞争机制。结果表明，增加流动强度和粒径d可以加快聚焦迁移。通过Wi量化的流动弹性可以减弱粒子旋转，从而减弱侧向粒子集中到通道中心线的现象。在仿真中观察到粒子集中在通道中心线或通道壁上的分离线。结果提供了新的见解，以了解粘弹性流中的粒子弹性惯性聚焦，并可以用于指导粘弹性微流体的设计。