CFD models of the bronchial airways with dynamic boundaries

摘要

Obtaining reliable CFD predictions of the bronchial flow that reflects the actual flow\udwithin a living lung requires the development of a deforming airways model, and the\udimposition of physiological subject-specific boundary conditions. This thesis addresses\udthese two issues by the development of dynamic CFD models of the bronchial airways\udusing a dynamic CT data set covering the breathing cycle of a laboratory animal. A\uddeformation algorithm is proposed that matches the CFD mesh of the subsequent\udairway geometries generated from the dynamic CT data set. In addition, a novel\udnonlinear dynamic airway model generated from a pair of CT images is introduced. The\udproposed non-linear deforming model is capable of successfully capturing the non-linear\udmotion characteristics of the bronchial airways based on the clinical measurements of\udthe lung volume change. Furthermore, a technique to drive physiological subject specific\udboundary conditions for the terminal surfaces of the CFD models of the\udbronchial airways is introduced. The proposed technique depends on approximating the\udlung volume associated to each terminal surface over several time points over the\udbreathing cycle based on the mechanical coupling between the bronchial airways and\udthe vascular tree. The computed dynamic subject-specific boundary conditions were\udimposed on the terminal surfaces of the deforming airway model and the effect of wall\udmotion on the flow features during tidal breathing is investigated for the first time.\udThe outcome of this thesis is expected to improve the fidelity of the CFD predictions of\udthe bronchial flow compared to the actual flow within a living lung. In addition, the\udavailability of a new non-linear dynamic model of the bronchial airways that requires\udone pair of CT images as input, which complies with the radiation dosage restrictions for\udhumans will facilitate the development of well-resolved CFD models of the human\udbronchial airways.