Abstract

Objective The simulation of aerosol transport and deposition in confined spaces is essential for indoor air quality control and nuclear reactor safety analysis. The Eulerian drift-flux model is an effective approach for predicting aerosol behavior， with lower computational cost compared to Lagrangian methods. However， the main difficulty in applying this model arises from the numerical instability and convergence issues caused by improper treatment of the gravitational settling source term and wall deposition boundary conditions. This leads to limited accuracy and restricted applicability in large-scale simulations. Based on the three-layer deposition theory and computational fluid dynamics （CFD） techniques， the gravitational settling term and wall concentration boundary condition are reformulated. The methods and results of this study contribute to the accurate simulation of aerosol natural removal in nuclear containments or ventilated rooms.

Methods In this study， firstly， the aerosol transport equation was established based on the drift-flux model， incorporating Brownian diffusion， turbulent diffusion， and gravitational settling. The gravitational settling velocity was introduced as a source term， and the wall deposition boundary condition was derived from the Lai-Nazaroff three-layer model by converting the deposition flux into a Dirichlet-type concentration boundary condition， where the wall concentration was expressed as a function of near-wall cell concentration， mainstream concentration， and local deposition velocity. Secondly， the above model was implemented in ANSYS Fluent via user-defined scalar （UDS） transport equations. A one-way coupled solution procedure was adopted. The steady flow field was solved first using the RNG k-ε turbulence model， followed by a transient UDS simulation. Thirdly， the model was validated by simulating the aerosol distribution and deposition experiments of Chen et al. in a 0.8 m×0.4 m×0.4 m ventilated chamber. 1 μm and 10 μm particles were considered， and the simulated concentration profiles were compared with experimental data and previous simulation results. Fourthly， the validated model was applied to simulate the natural removal of NaOH aerosol in the AHMED facility （1.81 m³ cylindrical vessel）. The polydisperse aerosol was divided into five size bins （0.6， 0.85， 1.2， 1.7， and 2.4 μm） to represent the lognormal distribution， and the transport of each bin was solved simultaneously. Finally， the simulated mass concentration decay curves were compared with the experimental data， and the spatial concentration stratification phenomenon was analyzed.

Results and Discussion According to the model established above， it was found by calculation that the 1 μm particles were nearly uniformly distributed after 1 800 s， while the 10 μm particles exhibited noticeable spatial inhomogeneity and remained stratified， which agreed well with the experimental observations and previous simulations shown in Fig.5 and Fig.6. Therefore， the proposed boundary treatment yielded stable and accurate predictions. When the model was applied to the AHMED natural deposition case， gravitational settling dominated the removal process. Larger particles （2.4 μm） were completely deposited at approximately 3 500 s， followed by 1.7 μm particles at about 6 500 s. As a result， the decay curves of normalized total mass concentration showed a piecewise linear trend rather than a single exponential decay （Fig.7）. The concentration stratification along the vertical direction became increasingly evident over time， with lower concentration near the bottom due to the net deposition flux， while Brownian diffusion only smoothed the interfacial gradient （Fig.6）. The initial and final stages showed excellent agreement. Discrepancies in the middle stage were attributed to the assumptions of uniform initial concentration and stagnant airflow， as well as the limited number of particle size bins.

Conclusion In this study， a numerically robust and physically comprehensive drift-flux aerosol model is developed within a commercial CFD platform. By reformulating the gravitational settling term as an implicit source and converting the wall deposition flux into a concentration boundary condition， significant improvements in convergence and stability are achieved. The model is systematically validated against benchmark ventilated chamber experiments and successfully reproduces the natural deposition behavior of polydisperse NaOH aerosols in the AHMED facility. It is found that gravitational settling is the primary removal mechanism under stagnant conditions， leading to strong vertical concentration stratification. The piecewise decay of total mass concentration reflects the sequential depletion of different particle size classes. To further improve the accuracy for polydisperse aerosols， the number of particle size bins can be increased， and future work should extend the model to include thermophoresis and diffusiophoresis. The present model is general and can be used as a reliable tool for predicting aerosol transport and deposition in nuclear containments， cleanrooms， and other ventilated enclosures.

Keywords： computational fluid dynamics； Eulerian-Eulerian approach； drift-flux model； aerosol； natural removal

Get Citation：Qi Zhichao， Gu Haifeng， Sun Xiaohui， et al. Development and application of aerosol drift-flux model based on computational fluid dynamics［J］. China Powder Science and Technology， 2026， 32（4）： 32-42.

Received：2026-02-12， Revised： 2026-06-02，Online： 2026-06-16.

Funding：The research was supported by National Key Research and Development Program of China (Grant No. 2020YFB1901400).

DOI：10.13732/j.issn.1008-5548.2026.04.001

CLC No.：TB44；TL364

Type Code：A

Serial No.：1008-5548（2026）04-0032-11