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Longitudinal mixing by the human larynx

A F Simone, J S Ultman

Respiration Physiology

|August 1, 1982

Summary

The human larynx cast enhanced gas mixing downstream of the glottis, but overall mixing decreased due to turbulence. This study investigated airflow and dispersion characteristics within a larynx model.

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Area of Science:

Fluid dynamics
Respiratory physiology
Acoustic science

Background:

Understanding airflow dynamics within the human larynx is crucial for respiratory health.
Previous studies have explored laryngeal airflow but lacked detailed dispersion analysis.
The impact of laryngeal geometry on gas mixing requires further investigation.

Purpose of the Study:

To investigate the velocity field and longitudinal dispersion of tracer gases in a human larynx cast.
To analyze the effects of different airflow rates (laminar, transitional, turbulent) on gas mixing.
To determine the influence of the glottis and resulting turbulence on overall mixing efficiency.

Main Methods:

Experiments were conducted using a cast of a human larynx within a 5m tube.
Airflow was introduced at three rates: 206, 425, and 775 ml/s, creating laminar, transitional, and turbulent flow.
Longitudinal dispersion of helium, oxygen, and sulfur hexafluoride was measured downstream of the glottis.

Main Results:

A significant enhancement in longitudinal mixing was observed immediately downstream of the glottis, attributed to jetting and Taylor dispersion.
This enhancement was independent of airflow rate but inversely related to molecular diffusivity.
Intense local turbulence generated by the glottis propagated significantly, flattening velocity profiles and reducing downstream mixing.

Conclusions:

The glottis significantly impacts airflow characteristics and gas dispersion within the larynx.
While localized mixing is enhanced, the overall longitudinal mixing is reduced due to glottis-induced turbulence.
These findings have implications for understanding gas transport in the respiratory system.

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