Characteristics of pressure drop, mass flow distribution and flow asymmetry in three‐dimensional branching networks based on model human bronchial tree

The complex flow field in the three‐dimensional internal passages of a model human bronchial tree is studied computationally. Up to five generations of branches, both in‐plane and out‐of‐plane configurations, two velocity profiles and varying inlet Reynolds number are considered. There exists substantial non‐uniformity of the fluid dynamic features (e.g. velocity field, pressure field, mass flow distribution or viscous dissipation) over any longitudinal plane or cross‐sectional plane of a particular branch as well as that between different branches of any generation. The flow asymmetry is explained here by attributing the fluid dynamics to three important features ‐ curvature of flow path, flow division at bifurcations and inertia of the flow. A synthesis of the present comprehensive study leads to the generalization that the out‐of‐plane configuration fosters greater degree of uniformity in the mass flow distributions in the various branches of any generation, but gives rise to greater flow non‐uniformity on any particular cross‐sectional plane as compared to the in‐plane configuration. The out‐of‐plane configuration also causes greater secondary flow and greater loss in total pressure in the network. The effectiveness of previously developed modular computational approaches is assessed through separate simulations for networks comprising two, three, four and five generations (containing 3, 7, 15 and 31 branches respectively). The inadequacy of Hagen‐Poiseuille type 1D model is demonstrated ‐ it can neither predict the flow asymmetry (captured by the 3D computations) nor determine the overall magnitude of loss in total pressure. The complex flow field in the three‐dimensional internal passages of a model human bronchial tree is studied computationally. Up to five generations of branches, both in‐plane and out‐of‐plane configurations, two velocity profiles and varying inlet Reynolds number are considered. There exists substantial non‐uniformity of the fluid dynamic features (e.g. velocity field, pressure field, mass flow distribution or viscous dissipation) over any longitudinal plane or cross‐sectional plane of a particular branch as well as that between different branches of any generation….