Design of a numerical model of lung by means of a special boundary condition in the truncated branches

• Published in: International journal for numerical methods in biomedical engineering Vol. 33; no. 6
• Main Authors: Tena, Ana F., Fernández, Joaquín, Álvarez, Eduardo, Casan, Pere, Walters, D. Keith
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.06.2017
• Subjects: Aerodynamics; boundary condition; Boundary conditions; CFD; Computational fluid dynamics; Computed tomography; Computer applications; Computer Simulation; Construction specifications; Cost engineering; Diseases; Expiration; Fluid dynamics; Humans; Hydrodynamics; Inspiration; Lung - anatomy & histology; Lung - physiology; Lung - physiopathology; Lung diseases; Mathematical models; Pressure; Reconstruction; Respiratory tract; Tomography, X-Ray Computed; truncated branches; user‐defined function; Velocity; velocity mapping technique; CFD; boundary condition; user-defined function; velocity mapping technique; truncated branches
• ISSN: 2040-7939; 2040-7947
• DOI: 10.1002/cnm.2830

Background The need for a better understanding of pulmonary diseases has led to increased interest in the development of realistic computational models of the human lung. Methods To minimize computational cost, a reduced geometry model is used for a model lung airway geometry up to generation 16. Truncated airway branches require physiologically realistic boundary conditions to accurately represent the effect of the removed airway sections. A user‐defined function has been developed, which applies velocities mapped from similar locations in fully resolved airway sections. The methodology can be applied in any general purpose computational fluid dynamics code, with the only limitation that the lung model must be symmetrical in each truncated branch. Results Unsteady simulations have been performed to verify the operation of the model. The test case simulates a spirometry because the lung is obliged to rapidly perform both inspiration and expiration. Once the simulation was completed, the obtained pressure in the lower level of the lung was used as a boundary condition. The output velocity, which is a numerical spirometry, was compared with the experimental spirometry for validation purposes. Conclusions This model can be applied for a wide range of patient‐specific resolution levels. If the upper airway generations have been constructed from a computed tomography scan, it would be possible to quickly obtain a complete reconstruction of the lung specific to a specific person, which would allow individualized therapies. A reduced symmetrical model is used in a model lung airway geometry up to generation 16 and can be applied in any general model. A user‐defined function has been developed, which applies velocities mapped from similar locations in fully resolved airway sections. If the upper airway generations have been constructed from a computed tomography scan, it would be possible to quickly obtain a complete reconstruction of the lung particularized for each person, which would allow individualized therapies.