Assessing respiratory airflow unsteadiness under different tidal respiratory frequencies using large eddy simulation...

Area of Science:

• Fluid dynamics
• Respiratory physiology
• Aerosol science

Background:

• Unsteady respiratory airflow is critical for particle deposition and drug delivery in the respiratory tract.
• Variations in respiratory flow rate and glottis motion at different frequencies complicate airflow analysis.

Purpose of the Study:

• To investigate the impact of respiratory frequencies on unsteady airflow characteristics.
• To analyze pressure fields, power loss, modal patterns, and vortex structures.
• To understand the role of glottis motion in energy consumption and airflow transitions.

Main Methods:

• Large-eddy simulations were employed to study airflow dynamics.
• Analysis included pressure fields, power loss, modal spatial patterns, and vortex structures.
• Modal decomposition and spectral entropy were used to characterize flow patterns.

Main Results:

• Respiratory frequencies significantly alter airflow unsteadiness, turbulence, and vortex dissipation.
• Pressure drops and flow rates at the glottis follow a power-law relationship, especially at low frequencies.
• Glottis motion influences energy consumption differently during inspiration and expiration and can be predicted by a polynomial function.

Conclusions:

• Modal decomposition is effective for studying respiratory flow, with separate analysis of inspiration and expiration recommended.
• Dominant modal spatial distributions characterize respiratory flow and are frequency-dependent.
• Glottis motion and slow breathing delay upper airway transitions, highlighting the impact of respiratory physiology on airflow.