Flow characteristics in a nasal to tracheo-bronchial airway using a scale resolving simulation

Area of Science:

• Fluid dynamics
• Respiratory physiology
• Computational modeling

Background:

• Airflow dynamics are critical for respiratory function but complex in the nasal and tracheo-bronchial pathways.
• Previous studies have not fully characterized flow regimes across these interconnected regions.

Purpose of the Study:

• To provide a unified, scale-resolving characterization of airflow dynamics from the nasal cavity to the 7th-generation bronchioles.
• To identify dominant flow structures and energy transfer mechanisms across different airway generations.

Main Methods:

• Utilized a patient-specific respiratory model from CT scans (nasal cavity to 7th-generation bronchioles).
• Employed hybrid Stress-Blended Eddy Simulation (SBES) for unsteady flow structures.
• Applied Dynamic Mode Decomposition (DMD) and spectral analysis for dominant flow dynamics.

Main Results:

• Laminar-dominant flow in the nasal cavity (6.2-8.4 m/s), transitioning to high-velocity jets in the larynx (up to 14.9 m/s) with significant unsteadiness.
• Flow became laminar-dominant in distal bronchioles (0.8-3.6 m/s) with low energy.
• Identified asymmetric flow partitioning between left (44.65%) and right (55.35%) bronchial branches.

Conclusions:

• This study offers a comprehensive airflow characterization across the upper and lower airways.
• Key regions of unsteadiness and energy dissipation were identified, impacting respiratory modeling and device design.
• Findings link flow behavior across airway regions, enhancing understanding of respiratory mechanics.