Multiphase Flow Systems (MPS), Otto-von-Guericke-University Magdeburg, Hoher Weg 7b, D-06120 Halle (Saale), Germany.
Multiphase Flow Systems (MPS), Otto-von-Guericke-University Magdeburg, Hoher Weg 7b, D-06120 Halle (Saale), Germany.
Eur J Pharm Sci. 2021 Nov 1;166:105959. doi: 10.1016/j.ejps.2021.105959. Epub 2021 Jul 26.
Airflow and aerosol deposition in the human airways are important aspects for applications such as pulmonary drug delivery and human exposure to aerosol pollutants. Numerical simulations are widely used nowadays to shed light in airflow features and particle deposition patterns inside the airways. For that purpose, the Euler/Lagrange approach is adopted for predicting flow field and particle deposition through point-particle tracking. Steady-state RANS (Reynolds-averaged Navier-Stokes) computations of flow evolution in an extended lung model applying different turbulence models were conducted and compared to measurements as well as high resolution LES (large-eddy simulations) for several flow rates. In addition, various inlet boundary conditions were considered and their influence on the predicted flow field was analysed. The results showed that the mean velocity field was simulated reasonably well, however, turbulence intensity was completely under-predicted by two-equation turbulence models. Only a Reynolds-stress model (RSM) was able predicting a turbulence level comparable to the measurements and the high resolution LES. Remarkable reductions in wall deposition were observed when wall effects were accounted for in the drag and lift force expressions. Naturally, turbulence is an essential contribution to particle deposition and it is well known that two-equation turbulence models considerably over-predict deposition due to the spurious drift effect. A full correction of this error is only possible in connection with a Reynolds-stress turbulence model whereby the predicted deposition in dependence of particle diameter yielded better agreement to the LES predictions. Specifically, with the RSM larger deposition is predicted for smaller particles and lower deposition fraction for larger particles compared to LES. The local deposition fraction along the lung model was numerically predicted with the same trend as found from the measurements, however the values in the middle region of the lung model were found to be somewhat larger.
空气在人体气道中的流动和悬浮颗粒的沉积是肺部给药和人体暴露于气溶胶污染物等应用的重要方面。目前广泛采用数值模拟的方法来研究气道内的流动特征和颗粒沉积模式。为此，采用欧拉/拉格朗日方法通过质点追踪来预测流场和颗粒沉积。针对扩展的肺部模型，采用不同的湍流模型进行了稳态 RANS（雷诺平均 Navier-Stokes）计算，以预测流场演化，并将计算结果与测量值以及不同流量下的高分辨率 LES（大涡模拟）结果进行了比较。此外，还考虑了各种入口边界条件，并分析了它们对预测流场的影响。结果表明，平均速度场得到了较好的模拟，但双方程湍流模型完全低估了湍流强度。只有雷诺应力模型（RSM）能够预测出与测量值和高分辨率 LES 相当的湍流水平。当在曳力和升力表达式中考虑壁面效应时，壁面沉积显著减少。显然，湍流是颗粒沉积的一个重要贡献，众所周知，由于虚假漂移效应，双方程湍流模型会大大高估沉积。只有在与雷诺应力湍流模型相结合的情况下，才能对这种误差进行完全修正，从而使预测的沉积与 LES 预测结果更一致。具体来说，与 LES 相比，RSM 预测的较小粒径颗粒沉积较多，而较大粒径颗粒的沉积分数较低。采用相同的方法预测了肺部模型的局部沉积分数，与测量值的趋势一致，但在肺部模型的中间区域，预测值稍大。
