Regulatory Mechanisms of Particle Dynamics and Deposition Distribution in Bend Pipes with Curvature Ratio

Curvature ratio (δ) governs secondary flows in gas–solid two-phase flow through bends, thereby affecting particle dynamics and leading to non-uniform wall deposition and increased erosion risk. In this study, a coupled Reynolds stress model (RSM) and Discrete phase model (DPM) framework was employed. A wall contact model incorporating adhesion, rebound, and removal mechanisms was implemented via a User-Defined Function (UDF). The spatial distribution and deposition characteristics of particles with different inertia (Stokes number range: 0.020 ≤ St ≤ 30.176) were systematically investigated in the range of δ = 2.0~3.5. The results reveal a distinct inertial dependence in particle spatial distribution: particles with St < 1 exhibit a “high-dispersion, weak-aggregation” pattern, whereas those with St > 1 form an “outer-wall agglomeration, inner-wall cavity” characteristic. As δ increases, the secondary flow intensity decreases while the effective centrifugal path lengthens. Governed by the combined effects of the effective collision coefficient (Rc) and effective adhesion rate (ηa), particle deposition is inhibited for St < 1 but enhanced for St > 1. This study advances the understanding of deposition under geometric constraints and provides a basis for optimizing pipeline design.