Computational flow studies in a subject-specific human upper airway using a one-equation turbulence model. Influence of the nasal cavity

• Published in: International journal for numerical methods in engineering Vol. 87; no. 1-5; pp. 96 - 114
• Main Authors: Saksono, P. H., Nithiarasu, P., Sazonov, I., Yeo, S. Y.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 08.07.2011; Wiley
• Subjects: Air breathing; Airways; Biological and medical sciences; CBS; Computation; Computational methods in fluid dynamics; Exact sciences and technology; finite element method; Fluid dynamics; Fundamental and applied biological sciences. Psychology; Fundamental areas of phenomenology (including applications); Holes; Human; human upper airway; Inlets; larynx; Mathematical models; Mathematics; Mesh generation; Methods of scientific computing (including symbolic computation, algebraic computation); nose; Numerical analysis. Scientific computation; one-equation turbulence; Physics; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Sciences and techniques of general use; subject-specific; Trachea; Vertebrates: respiratory system; Turbulent flow; Upper respiratory tract; Steady flow; Inlet flow; Respiratory system; Automatic mesh generation; Modeling; Finite element method; CBS; subject-specific; Larynx; Localization; Steady state solution; Trachea; Mesh generation; Human; Method of characteristics; nose; Unstructured mesh; Flow rate; Fluid dynamics; one-equation turbulence; Bifurcation; Fractional step method; Computerized tomography; Air flow; human upper airway; Recirculating flow; Truncated shape; Nasal fossa
• ISSN: 0029-5981; 1097-0207; 1097-0207
• DOI: 10.1002/nme.2986

This paper focuses on the impact of including nasal cavity on airflow through a human upper respiratory tract. A computational study is carried out on a realistic geometry, reconstructed from CT scans of a subject. The geometry includes nasal cavity, pharynx, larynx, trachea and two generations of airway bifurcations below trachea. The unstructured mesh generation procedure is discussed in some length due to the complex nature of the nasal cavity structure and poor scan resolution normally available from hospitals. The fluid dynamic studies have been carried out on the geometry with and without the inclusion of the nasal cavity. The characteristic‐based split scheme along with the one‐equation Spalart–Allmaras turbulence model is used in its explicit form to obtain flow solutions at steady state. Results reveal that the exclusion of nasal cavity significantly influences the resulting solution. In particular, the location of recirculating flow in the trachea is dramatically different when the truncated geometry is used. In addition, we also address the differences in the solution due to imposed, equally distributed and proportionally distributed flow rates at inlets (both nares). The results show that the differences in flow pattern between the two inlet conditions are not confined to the nasal cavity and nasopharyngeal region, but they propagate down to the trachea. Copyright © 2010 John Wiley & Sons, Ltd.