Pressure distribution and flow dynamics in a nasal airway using a scale resolving simulation

TL;DR

This study uses scale-resolving CFD simulations to analyze unsteady airflow in the nasal cavity, revealing flow behaviors at different inhalation rates and validating results with experimental data.

Contribution

It introduces a hybrid RANS-LES CFD approach to accurately capture unsteady nasal airflow and compares it with experimental measurements across various flow rates.

Findings

Large pressure drops at nasal valve and nasopharynx

Turbulent activity in posterior nasal cavity at high flow rates

Laminar flow dominance at lower flow rates

Abstract

Airflow through the nasal cavity exhibits a wide variety of fluid dynamicsbehaviour due to the intricacy of the nasal geometry. The flow is naturallyunsteady and perhaps turbulent, despite CFD in the literature that assumesa steady laminar flow. Time-dependent simulations can be used to generatedetailed data with the potential to uncover new flow behaviour, although theyare more computationally intensive compared with steady-state simulations. Furthermore, verification of CFD results has relied on reported pressure drop(e.g. nasal resistance) across the nasal airway although the geometries usedare different. This study investigated the unsteady nature of inhalation atflow rates of 10, 15, 20, and 30 L/min. A scale resolving CFD simulationusing a hybrid RANS-LES model was used and compared with experimentalmeasurements of the pressure distribution and the overall pressure drop in thenasal cavity. The experimental results indicated a large pressure drop acrossthe nasal valve, as well as across the nasopharynx with the latter attributedto a narrow cross-sectional area. At a flowrate of 30 L/min, the CFD simula-tions showed that the anterior half of the nasal cavity displayed dominantlylaminar but disturbed flow behaviour in the form of velocity fluctuations. Theposterior half of the nasal cavity displayed turbulent activity, characterised byerratic fluctuating velocities, which was enhanced by the wider cross-sectionalareas in the coronal plane. At 15L/min, the flow field was laminar dominantwith very little disturbance confirming a steady-state laminar flow assumptionis viable at this flow rate.