TOWARDS DEVELOPING AN OPEN-SOURCE IN SILICO LUNG MODEL FOR TARGETED DRUG DELIVERY AND DEVICE ENGINEERING

The purpose of this research is to implement a whole-lung computational fluid dynamics (CFD) model in “OpenFOAM” to simulate transport and deposition of aerosols throughout the respiratory airways using a newly developed stochastic individual pathway (SIP) method. This approach simulates the upper respiratory airways, which could be derived using CT scans. Further, to validate the upper airway CFD models, concurrent in vitro experiments of aerosol transport and deposition are performed in identical 3D printed models of the airways. The lower airways are then modeled using the SIP approach in which ensembles of individual pathways are created and simulated. Currently, the whole-lung model is implemented in the commercial CFD software “ANSYS FLUENT” and, based on in vitro and in vivo validations, many numerical model refinements have been implemented through user-defined functions. Recent studies demonstrated that the SIP approach is an effective method to simulate lung deposition of pharmaceutical aerosols with a computational savings of multiple orders of magnitude compared with simulating all of the tracheobronchial airways. The focus of the current study is to implement the aerosol transport and delivery models using “OpenFOAM” libraries and to validate using relevant in vitro test cases. First, a 90° bend geometry was used as a simple test case for which experimental aerosol deposition data is available in the transitional and turbulent flow regimes. Further, to evaluate the deposition prediction in respiratory airways, a model dry powder inhaler was connected with a realistic model of the mouth-throat geometry and upper tracheobronchial region. Based on CFD predictions in these test cases, it was found that in order to capture transport and deposition with “OpenFOAM”, code improvements are needed to account for many important physical phenomena related to turbulence, near-wall conditions, particle interactions with turbulent eddies, particle-wall hydrodynamic interactions and particle deposition. In this presentation, the effect of turbulence models and corresponding anisotropic corrections, steady-state flow assumption and particle-wall interactions on aerosol transport and depositions will be discussed in detail.