Abstract

Objective The inertial migration of particles in circular pipe Poiseuille flow （Segré-Silberberg effect） holds important application value in microfluidic technologies such as particle enrichment， separation， and detection. Existing studies have mainly focused on the final radial equilibrium position of particles， while the understanding of the dynamic characteristics throughout the entire migration process （such as the evolution patterns of trajectory， migration velocity， and rotational velocity） and their dependence on the initial position remains insufficient. To investigate the influence mechanism of the initial position on the inertial migration dynamics of particles， this study conducts numerical simulations of the motion of a single neutrally buoyant spherical particle in a circular pipe Poiseuille flow.

Methods Using the fictitious domain method based on the coupling of computational fluid dynamics and the discrete element method， a three-dimensional circular pipe flow model was established. The pipe had a diameter of 8 mm and a length of 0.5 m. The particle diameter was 1.3 mm. Both the particle and fluid densities were 1 050 kg·m^-3， and the kinematic viscosity of the fluid was 1.428 6×10^-6 m²·s^-1. A fully developed Poiseuille-flow velocity boundary was imposed at the pipe inlet， a zero-pressure boundary was set at the outlet， and a no-slip condition was applied at the pipe wall. The initial radial positions of the particle covered three cases： between the equilibrium position and the pipe center， near the equilibrium position， and between the equilibrium position and the pipe wall. The reliability of the numerical model was validated through mesh independence verification （using 655 583 static meshes with three-level dynamic refinement in the particle domain） and by comparison with results from the literature. Simulations were conducted under Reynolds numbers Re=200， 400， 600， and 800 to analyze the time evolution and final equilibrium characteristics of particle radial position， radial migration velocity， and rotational velocity.

Results and Discussion As the Reynolds number increased， the inertial migration trajectory of particles exhibited three typical modes： monotonic， overshooting， and oscillatory migration. At Re=200， particles monotonically approached the radial equilibrium position. At Re=400， overshooting occurred， and particles returned after crossing the equilibrium position. When Re exceeded 600， particles oscillated with decaying amplitude after reaching the equilibrium position and eventually became stabilized. The radial equilibrium position of particles was independent of the initial position. However， with increasing Reynolds number， the equilibrium position first moved toward the pipe wall （Re=200-400） and then toward the centerline （Re = 400-800）. The dimensionless equilibrium position r*/R varied from 0.687 to 0.716， with a change rate of less than 2.6%. In the monotonic migration regime （Re=200）， when the initial position deviated from the equilibrium position， the radial migration velocity first increased and then decreased to 0. In the overshooting regime （Re=400）， the radial velocity first decreased to 0， then increased in the opposite direction， and finally decreased to 0 again. In the oscillatory regime （Re=600 and 800）， the radial velocity showed a decaying oscillation. The average radial migration velocity for particles to reach the equilibrium position for the first time was jointly affected by the initial position and the Reynolds number. When the initial position was close to the pipe center， the average velocity increased monotonically with Re. However， when the initial position was close to the pipe wall， the average velocity at Re=500 was significantly lower than that at Re=400 because oscillatory migration at high Reynolds numbers prolonged the time required to first reach the equilibrium position. The temporal evolution patterns of the particle rotational velocity were highly consistent with the radial migration trajectory， and the final rotational velocity increased monotonically with the Reynolds number and was independent of the initial position. The fundamental reason was that particle rotation was dominated by the velocity gradient of the local flow field， and this gradient increased with Reynolds number.

Conclusion The Reynolds number governs the inertial migration mode and final equilibrium position of particles， whereas the initial position determines the migration dynamic characteristics （such as the evolution path of radial velocity and the average migration velocity）. The findings provide a theoretical basis for achieving precise regulation and efficient separation of particles through inertial migration.

Keywords： liquid-solid two-phase flow； Poiseuille flow； inertial migration； particle dynamics； computational fluid dynamics-discrete element method （CFD-DEM）

Get Citation：Fan Fengxian， Chen Chaofan， Luo Weile. Influence of initial position on inertial migration of particles in circular pipe Poiseuille flow［J］. China Powder Science and Technology， 2026， 32（5）： 1-12.

Received：2026-03-21，Revised： 2026-05-10，Online： 2026-06-18.

Funding：The research was supported by the National Natural Science Foundation of China (Grant No. 52476157) and China Machinery Industry Federation Key Laboratory of Multiphase Flow Measurement (Grant No. 2024SA-05-22).

DOI：10.13732/j.issn.1008-5548.2026.05.002

CLC No.：O359； TB44

Type Code：A

Serial No.：1008-5548（2026）05-0001-12