# CFD Simulation of Airflow Dynamics During Cough Based on CT-Scanned Respiratory Airway Geometries

^{1}

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Governing Equation

#### 2.2. Turbulent Model

#### 2.3. Boundary Condition

^{3}and a viscosity of 1.81 × 10

^{5}Pa·s in 20 °C and a standard atmosphere. The mass flow inlet was chosen and the mass flow rate was coded through the Fluent user defined function using the model proposed by Gupta which is presented in Equations (3) and (4) [17].

#### 2.4. Numerical Modelling

## 3. Validation

## 4. Results and discussion

#### 4.1. Air Velocity, Wall Pressure, and Wall Shear Stress of the Cough Process

^{5}Pa (absolute pressure) which appeared at the end of the bronchi. Due to the high airflow velocity, the wall pressure at some places, which have been labeled by a red circle, was below the atmospheric pressure.

#### 4.2. Local Flow Properties

#### 4.3. Influence of the Cough Peak Flow Rate on Airflow Dynamics

^{5}Pa, and 35.91 Pa, respectively.

## 5. Conclusions

^{5}Pa and 35.91 Pa, respectively. Additionally, the cough peak flow rate had little influence on the flow distribution of the left and right main bronchi during the cough process.

## Author Contributions

## Funding

## Conflicts of Interest

## Nomenclature

CT | Computerized tomography |

CFD | Computational fluid dynamics |

CPFR | Cough peak flow rate |

MRI | Magnetic resonance imaging |

QUICK | Quadratic upwind interpolation |

SST | Shear stress transport |

SIMPLE | Semi-implicit method |

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**Figure 4.**Comparison of the velocity profile for the right main bronchus. (

**a**) The locations of the extracted face, X axis, and Y axis. (

**b**) The velocity along the X direction. (

**c**) The velocity along the Y direction.

**Figure 5.**Airflow velocity streamlines at four time points (

**a**) 0.02 s; (

**b**) 0.08 s; (

**c**) 0.2 s; (

**d**) 0.5 s.

**Figure 6.**Spatial distribution of the wall pressure at four time points (

**a**) 0.02 s; (

**b**) 0.08 s; (

**c**) 0.2 s; (

**d**) 0.5 s.

**Figure 8.**Local flow properties of the four cross sections at four time points (

**a**) 0.02 s; (

**b**) 0.08 s; (

**c**) 0.2 s; (

**d**) 0.5 s.

**Figure 9.**The variation in airflow dynamics with the cough peak flow rate (

**a**) maximum velocity; (

**b**) maximum wall pressure; (

**c**) maximum wall shear stress.

Right Main Bronchus | Current CFD Simulation | Measurement (Rochefort (2007)) |
---|---|---|

A (cm^{2}) | 4.75 | 5.10 |

Q (L/s) | 0.139 | 0.140 ± 0.011 |

Location | 3 L/s | 4 L/s | 5 L/s | 6 L/s | 7 L/s | 8 L/s | 9 L/s | 10 L/s |
---|---|---|---|---|---|---|---|---|

Left main bronchus | 46.19% | 46.14% | 46.12% | 46.06% | 46.12% | 46.08% | 46.11% | 46.07% |

Right main bronchus | 53.81% | 53.86% | 53.88% | 53.94% | 53.88% | 53.92% | 53.89% | 53.93% |

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## Share and Cite

**MDPI and ACS Style**

Kou, G.; Li, X.; Wang, Y.; Lin, M.; Zeng, Y.; Yang, X.; Yang, Y.; Gan, Z.
CFD Simulation of Airflow Dynamics During Cough Based on CT-Scanned Respiratory Airway Geometries. *Symmetry* **2018**, *10*, 595.
https://doi.org/10.3390/sym10110595

**AMA Style**

Kou G, Li X, Wang Y, Lin M, Zeng Y, Yang X, Yang Y, Gan Z.
CFD Simulation of Airflow Dynamics During Cough Based on CT-Scanned Respiratory Airway Geometries. *Symmetry*. 2018; 10(11):595.
https://doi.org/10.3390/sym10110595

**Chicago/Turabian Style**

Kou, Guiyue, Xinghu Li, Yan Wang, Mouyou Lin, Yuping Zeng, Xiaopin Yang, Yanyan Yang, and Zhimei Gan.
2018. "CFD Simulation of Airflow Dynamics During Cough Based on CT-Scanned Respiratory Airway Geometries" *Symmetry* 10, no. 11: 595.
https://doi.org/10.3390/sym10110595