Zhang Ziru，Zhang Wenxin， Dai Hongyang， Wang Jiale， Lou Zhihan， LiRan， Han Ren
School of Optical-Electrical and Computer Engineering， University of Shanghai for Science and Technology， Shanghai 200093， China
Abstract
Objective This study investigates the transport and deposition process of micron-sized pharmaceutical powder particles in a realistic oral-pharyngeal model under no-airflow conditions. Considering that practical oral drug delivery is usually accompanied by airflow disturbances， the no-airflow condition is selected as a fundamental research scenario to clarify the controlling roles of initial emission characteristics and wall interactions on the early-stage transport and deposition of pharmaceutical powder particles. On this basis， the coupled effects of initial emission velocity， surface energy， and emission angle on particle kinetic energy evolution and deposition distribution in nine oral regions are analyzed. It quantitatively characterizes early-stageloss mechanisms in the oral cavity，providing a basis for optimizing spray parameters of inhalation devices.
Methods A semi-idealized three-dimensional oral-pharyngeal model was constructed based on real CT data.While preserving the main geometric characteristics related to particle transport，the model was appropriately simplified to facilitate numerical simulations and comparative analysis.Particle motion was then simulated numerically using a wall-contact model that included collision， rebound， and adhesion.To evaluate the influence of initial emission conditions，both single-factor effect and the combined effects of emission velocity， surface energy， and emission angle were investigated.Controlled numerical experiments were designed by varying one parameter at a time， and representative parameter combinations were compared，allowing clearer identification of individual and coupled influence on particle transport and deposition. During the simulations，the full process from particle release to final deposition was tracked. Particle trajectories were reconstructed analyze particle migration in the oral-pharyngeal passage and to identify differences in motion patterns under different parameter settings.At the same time，the temporal evolution of particle kinetic energy was examined to characterize energy attenuation during repeated wall interactions.In addition，final particle deposition was statistically quantified in nine oral regions to compare regional deposition tendencies under different release conditions.By combining controlled-variable numerical experiments with trajectory reconstruction，kinetic-energy attenuation analysis，and regional deposition statistics，the deposition mechanisms were comparatively evaluated from the perspectives of motion behavior，energy dissipation， and spatial distribution.
Results and Discussion The results showed that early-stage particle transport and deposition were jointly affected by emission velocity，surface energy， and emission angle.As emission velocity increased， the average kinetic energy of particles rose， and the probability of rebound after wall impact also increased，resulting in reduced anterior deposition in oral cavity and increased deposition in downstream regions，especially Regions 7—9.This indicated that higher initial velocity reduced early-stage loss of particles and promoted particle migration toward deeper regions of the oral-pharyngeal passage，although its actual effect remained constrained by release direction and wall adhesion.Surface energy mainly affected the balance between post-impact adhesion and continued transport.Under high surface-energy conditions，such as γ=0.30 J/m²，particles were more likely to adhere upon first contact，which increased anterior deposition and reduced further migration.In contrast，under low surface-energy conditions， particles were less likely to adhere immediately after impact，and repeated collisions and rebounds occurred more easily，leading to more complex pathways of energy attenuation.Emission angle also showed a significant effect on particle transport and deposition.Small elevation angles， particularly 0°~15°，were more favorable for forward transport into downstream regions，whereas larger elevation angles of 30°~45°tended to direct particles upward，increasing collisions with the oral cavity roof and promoting premature deposition.Overall，the comparative results indicated that early-stage particle transport and deposition were controlled by the coupled effects of emission velocity，emission angle， and surface energy， rather than by any single factor alone. Among the tested conditions，the optimal combination was identified as V=2.0 m/s，θ=15°，and γ=0.20 J/m²，under which kinetic energy attenuation was relatively smoother，the regional deposition distribution was more uniform， and the delivery efficiency was maximized.
Conclusion Under no-airflow conditions， early-stage transport and deposition distribution of particles are jointly regulated by emission velocity， emission angle， and surface energy. By influencing post-collision kinetic energy， rebound behavior， and wall adhesion， these three factors collectively determine particle transport capability and early-stage loss within the oral cavity. Higher emission velocity facilitates transport toward deeper regions of the oral cavity， but this effect is still constrained by emission direction and adhesive forces. Larger upward angles intensify collisions with the upper wall and aggravate deposition， whereas higher surface energy enhances particle adhesion after the initial collision and suppresses subsequent transport. Optimal performance is achieved only when these three parameters are properly balanced， enabling enhanced kinetic energy retention， reduced deposition， and improved delivery efficiency.
Keywords： inhalable drug particle； oral-pharyngeal model； numerical simulation； deposition behavior； surface energy； emission velocity； emission angle
Get Citation:Zhang Ziru， Zhang Wenxin， Dai Hongyang， et al. Transport mechanisms of pharmaceutical powder particles in a realistic oral cavity model［J］. China Powder Science and Technology， 2026， 32（6）： 1-16.
Received：2026-01-28， Revised： 2026-04-23，Online： 2026-06-23。
Funding： The research was supported by the National Natural Science Foundation of China (Grant No. 12002213).
CLC No.：O469； TB4
Type Code：A
Serial No.：1008-5548（2026）06-0001-16
