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Article
Publication date: 19 May 2022

Yongjun Jin, Haihang Cui, Li Chen, Kai Sun, Haiguo Yin and Zhe Liu

This study aims to perform flow simulations inside the acinus with fine alveolar pores (Kohn pores) using hexagonal cells and bottom-up geometric modeling, which enabled the…

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Abstract

Purpose

This study aims to perform flow simulations inside the acinus with fine alveolar pores (Kohn pores) using hexagonal cells and bottom-up geometric modeling, which enabled the elimination of invalid voids using previous top-bottom methods and spherical or circular cells.

Design/methodology/approach

Regular hexagonal cells were used to construct alveoli with no gaps via tessellation. Some hexagonal cells were fused to eliminate the inner boundaries to represent the structure of the bronchial tree. For the remaining hexagonal cells, the side lengths of the shared walls were adjusted to construct alveolar pores. Periodic moving boundaries with the same phase were set for all walls to describe synchronous contraction and expansion of the bronchi and alveoli.

Findings

More realistic flow characteristics in the distal lung were obtained. The effects of pore size and the mechanism of auxiliary ventilation of alveolar pores were revealed.

Originality/value

To the best of the authors’ knowledge, this is the first numerical simulation study on the function of multiple alveolar pores at the level of pulmonary acini, which will be helpful for simulating the dynamic process of cough and sputum excretion in the future.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 7 September 2022

Zhe Liu, Zexiong Yu, Leilei Wang, Li Chen, Haihang Cui and Bohua Sun

The purpose of this study is to use a weak light source with spatial distribution to realize light-driven fluid by adding high-absorbing nanoparticles to the droplets, thereby…

143

Abstract

Purpose

The purpose of this study is to use a weak light source with spatial distribution to realize light-driven fluid by adding high-absorbing nanoparticles to the droplets, thereby replacing a highly focused strong linear light source acting on pure droplets.

Design/methodology/approach

First, Fe3O4 nanoparticles with high light response characteristics were added to the droplets to prepare nanofluid droplets, and through the Gaussian light-driven flow experiment, the Marangoni effect inside a nanofluid droplet was studied, which can produce the surface tension gradient on the air/liquid interface and induce the vortex motion inside a droplet. Then, the numerical simulation method of multiphysics field coupling was used to study the effects of droplet height and Gaussian light distribution on the flow characteristics inside a droplet.

Findings

Nanoparticles can significantly enhance the light absorption, so that the Gaussian light is enough to drive the flow, and the formation of vortex can be regulated by light distribution. The multiphysics field coupling model can accurately describe this problem.

Originality/value

This study is helpful to understand the flow behavior and heat transfer phenomenon in optical microfluidic systems, and provides a feasible way to construct the rapid flow inside a tiny droplet by light.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 2
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 28 April 2022

Yongjun Jin, Haihang Cui, Li Chen, Zhe Liu and Kai Sun

The purpose of this paper is to study the mechanism of efficient sputum excretion from the distal lung by using a tessellationally distal lung model with alveolar pores.

98

Abstract

Purpose

The purpose of this paper is to study the mechanism of efficient sputum excretion from the distal lung by using a tessellationally distal lung model with alveolar pores.

Design/methodology/approach

First, a two-dimensional tessellational composite structure of the bronchus, alveoli and alveolar pores (Kohn pore) is constructed with the tessellational splitting and fusion of regular hexagonal elements. Then, the level set method is used to study the effects of alveolar pores and their sizes, expiratory cycles and respiratory intensity.

Findings

The existence of alveolar pores is the prerequisite for sputum excretion, and there is an optimal size of alveolar pores for sputum excretion. Strong asymmetric respiration can break the reversibility of the flow at a low Reynolds number and causes significant net displacement of sputum. The expiratory cycle is negatively correlated with the net displacement of sputum. The respiratory intensity is positively correlated with the net displacement of sputum.

Originality/value

This research is helpful for understanding the complex sputum excretion process in diseases, such as pneumonia, and developing corresponding adjuvant therapy.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 12
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 14 October 2022

Zhe Liu, Hao Wei, Li Chen, Haihang Cui and Bohua Sun

The purpose of this study is to establish an effective numerical simulation method to describe the flow pattern and optimize the strategy of noncontact mixing induced by…

161

Abstract

Purpose

The purpose of this study is to establish an effective numerical simulation method to describe the flow pattern and optimize the strategy of noncontact mixing induced by alternating Gaussian light inside a nanofluid droplet and analyzing the influencing factors and flow mechanism of fluid mixing inside a droplet.

Design/methodology/approach

First, the heat converted by the alternating incident Gaussian light acting on the nanoparticles was considered as the bulk heat source distribution, and the equilibrium equation between the surface tension and the viscous force at the upper boundary force was established; then, the numerical simulation methods for multiple-physical-field coupling was established, and the mixing index was used to quantify the mixing degree inside a droplet. The effects of the incident position of alternating Gaussian light and the height of the droplet on the mixing characteristics inside a droplet were studied. Finally, the nondimensional Marangoni number was used to reveal the flow mechanism of the internal mixing of the droplet.

Findings

Noncontact alternating Gaussian light can induce asymmetric vortex motion inside a nanofluid droplet. The incident position of alternating Gaussian light is a significant factor affecting the mixing degree in the droplet. In addition, the heat transfer caused by the surface tension gradient promotes the convection effect, which significantly enhances the mixing of the fluid in the droplet.

Originality/value

This study demonstrates the possibility of the chaotic mixing phenomenon induced by noncontact Gaussian light that occurs within a tiny droplet and provides a feasible method to achieve efficient mixing inside droplets at the microscale.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

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