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Fluids
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Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications
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Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Flow of Multi-Phase Fluids and Granular Materials".

Deadline for manuscript submissions: closed (31 July 2024) | Viewed by 18713

Special Issue Editor

Dr. Lin Tian

E-Mail Website
Guest Editor
School of Engineering—Department of Mechanical, Manufacturing and Mechatronics Engineering, RMIT University, Melbourne 3000, Australia
Interests: aerosol transport; particle transport and deposition; turbulence modelling; CFD; bio-fluid transport; gas and particle dynamics

Special Issue Information

Dear Colleagues,

Complex particle flows require an understanding of the physics at different multi-scales: micro/nano scale, meso scale and macro scale. Research and development in particle flows are certainly in the climate of significant advancements being achieved in computing power and performance. Nevertheless, there remains much concerted development towards better understanding the associated complicated physics of particle flows through advanced computational methodologies and models.

The aim of this special issue is to present and discuss new developments in particle flow modelling and the applications in environmental and bio-transport engineering fields. Examples include but not limited to transport phenomena in human and animal respiratory systems, deposition and dosage calculation, environmental pollution monitoring and dispersion, occupational exposure risk assessment. The special issue will become an international forum for researchers to summarize the most recent development and ideas, identify critical areas of research need and promote collaborations.

Dr. Lin Tian
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • CFD
  • particle flow
  • respiratory dosimetry
  • targeted drug delivery
  • human and animal respiratory systems
  • environmental exposure
  • particulate matter
  • pollution dispersion
  • inhalation risk assessment

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Published Papers (7 papers)

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Research

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22 pages, 6687 KiB  
Article
A Numerical Evaluation of Airborne Transmission Control through Saliva Modification
by Rajendra Shrestha, Douglas Fontes and Michael Kinzel
Fluids 2024, 9(10), 228; https://doi.org/10.3390/fluids9100228 - 30 Sep 2024
Viewed by 575
Abstract
The present study explored the relationship between airborne transmission and the saliva fluid properties of a human sneeze. Specifically, we aimed to understand if altering the saliva and its relationship to droplet breakup and stability can affect its transmission characteristics. The study aimed [...] Read more.
The present study explored the relationship between airborne transmission and the saliva fluid properties of a human sneeze. Specifically, we aimed to understand if altering the saliva and its relationship to droplet breakup and stability can affect its transmission characteristics. The study aimed to answer this question using computational fluid dynamics, specifically, a hybrid Eulerian–Lagrangian model with a Spalart–Allmaras, detached eddy simulation turbulence model. The effort focused on a scenario with a sneeze event within a ventilated room. The study found that for sneezes, secondary breakdown processes are important. Thicker saliva that increased the Ohnesorge number displayed a clear resistance to aerosolization due to stabilized secondary breakup, leading the bulk of the drops having high settling rates that are less likely to drive airborne transmission. For instance, the use of xanthum gum, which increased the saliva viscosity by 2000%, reduced the formation of aerosols. Additionally, another class of modifiers that reduce saliva content was studied, which was also effective in reducing airborne transmission drivers. Zingiber, which reduced the saliva content, reduced the formation of aerosols. However, when considering the overall reduction in droplet volume, saliva modifiers such as cornstarch, xanthum gum, and lozenges increased the mean droplet size by 50%, 25%, and 50%, respectively, while reducing the overall droplet volume by 71.6%, 71.2%, and 77.2%, respectively. Conversely, Zingiber reduced the mean droplet size by 50% but increased the overall droplet volume by 165.7%. Overall, for this type of respiratory event, this study provides insight into the potential for modifying saliva characteristics that may impact airborne transmission and could introduce new tools for reducing airborne pathogen transmission. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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22 pages, 8299 KiB  
Article
Impacts of Mask Wearing and Leakages on Cyclic Respiratory Flows and Facial Thermoregulation
by Kian Barari, Xiuhua Si and Jinxiang Xi
Fluids 2024, 9(1), 9; https://doi.org/10.3390/fluids9010009 - 27 Dec 2023
Cited by 2 | Viewed by 2316
Abstract
Elevated face temperature due to mask wearing can cause discomfort and skin irritation, making mask mandates challenging. When thermal discomfort becomes intolerable, individuals instinctively or unknowingly loosen or remove their facemasks, compromising the mask’s protective efficacy. The objective of this study was to [...] Read more.
Elevated face temperature due to mask wearing can cause discomfort and skin irritation, making mask mandates challenging. When thermal discomfort becomes intolerable, individuals instinctively or unknowingly loosen or remove their facemasks, compromising the mask’s protective efficacy. The objective of this study was to numerically quantify the microclimate under the mask and facial thermoregulation when wearing a surgical mask with different levels of misfit. An integrated ambient–mask–face–airway computational model was developed with gaps of varying sizes and locations and was validated against complementary experiments. The low Reynolds number (LRN) k-ω turbulence model with porous media was used to simulate transient respiratory flows. Both skin convective heat transfer and tissue heat generation were considered in thermoregulation under the facemask, besides the warm air exhaled from the body and the cool air inhaled from the ambient. The results of this study showed that when wearing a surgical mask with a perfect fit under normal breathing, the temperature at the philtrum increased by 4.3 °C compared to not wearing a mask. A small gap measuring 0.51 cm2 (gap A) at the nose top resulted in 5.6% leakage but reduced the warming effect by 28% compared to zero gap. Meanwhile, a gap of 4.3 cm2 (R1L1) caused 42% leakage and a 62% reduction in the warming effect. Unique temporospatial temperature profiles were observed at various sampling points and for different gap sizes, which correlated reasonably with the corresponding flow dynamics, particularly close to the gaps. The temperature change rate also exhibited patterns unique to the gap site and sampling point, with distinctive peaks occurring during the inspiratory–expiratory flow transitions. These results have the significant implications that by using the temporospatial temperature profiles at several landmark points, the gap location can potentially be pinpointed, and the gap size and leakage fractions can be quantified. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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14 pages, 5645 KiB  
Article
Portable Air Purifiers’ Predicted Efficacy in Mitigating Airborne Pathogen Transmission in an Office Room Featuring Mixing Ventilation
by Xiangdong Li, Milan J. Patel and Ivan S. Cole
Fluids 2023, 8(12), 307; https://doi.org/10.3390/fluids8120307 - 27 Nov 2023
Viewed by 2245
Abstract
Portable air purifiers have been extensively used to improve indoor air quality and mitigate the transmission of airborne diseases. However, the efficacy of mitigation is strongly affected by the interactions between jet flows of processed air from the air purifiers and the background [...] Read more.
Portable air purifiers have been extensively used to improve indoor air quality and mitigate the transmission of airborne diseases. However, the efficacy of mitigation is strongly affected by the interactions between jet flows of processed air from the air purifiers and the background airflows driven by the ventilation system. Critical factors in this context include the position and capacity of air purifiers and the ventilation rate of the heating ventilation and air-conditioning (HVAC) system. These factors are investigated in this study via computational fluid dynamics (CFD) simulations and the infection probability for different scenarios is quantified using the latest airborne infection predictive model incorporating recent pathological and clinical data for SARS-CoV-2. The results show that the use of air purifiers can significantly reduce the concentration of particulate matter, thus contributing to a generally lower risk of airborne transmission. However, the position of air purifiers affects their overall efficacy remarkably. Comparatively, a central HVAC system is more efficient at removing airborne particles under an equivalent ventilation rate assuming it uses a mixing ventilation scheme. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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15 pages, 13867 KiB  
Article
Analysis of Flow Characteristics of Window-Combination-Type Ventilation System Using CFD
by Mok-Lyang Cho, Hyeon-Ji Choi, Seo-Jin Kim and Ji-Soo Ha
Fluids 2023, 8(11), 294; https://doi.org/10.3390/fluids8110294 - 2 Nov 2023
Viewed by 1594
Abstract
In this study, we analyze the performance of ventilation modules to improve air quality in educational facilities. Using (CFD), we examine the flow design variables of a window-mounted ventilation module. Using computational analysis, we analyze various flow design characteristics of window-mounted ventilation modules [...] Read more.
In this study, we analyze the performance of ventilation modules to improve air quality in educational facilities. Using (CFD), we examine the flow design variables of a window-mounted ventilation module. Using computational analysis, we analyze various flow design characteristics of window-mounted ventilation modules and review optimal conditions. First, we measure the carbon dioxide concentration in the classroom and use CFD to analyze the internal air characteristics according to the ventilation module’s inflow speed, inflow angle, and indoor temperature conditions. According to classroom air quality management standards, the concentration of carbon dioxide must be managed below 1000 ppm. When the ventilation module’s inflow velocity was 2.0 m/s, a carbon dioxide concentration of less than 1000 ppm was measured in the classroom. Additionally, an air filter was selected to prevent the inflow of external fine dust through the ventilation module. The suitability of HEPA H14 was reviewed to design the weight concentration of fine dust flowing from the ventilation module to be less than 50 μg/m3. Through research, flow design conditions for a window-mounted ventilation module were presented to reduce carbon dioxide concentration inside the classroom. The analysis of the ventilation system flow characteristics proposed in this study derived primary data for improving the classroom ventilation system. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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19 pages, 8848 KiB  
Article
Numerical Study of Indoor Oil Mist Particle Concentration Distribution in an Industrial Factory Using the Eulerian–Eulerian and Eulerian–Lagrangian Methods
by Yukun Wang, Jingnan Sun, Meng Zhao, Alicia Murga, Sung-Jun Yoo, Kazuhide Ito and Zhengwei Long
Fluids 2023, 8(10), 264; https://doi.org/10.3390/fluids8100264 - 26 Sep 2023
Cited by 5 | Viewed by 1809
Abstract
The transport and prediction of the concentration of particles in confined spaces are crucial for human well-being; this has become particularly evident during the current worldwide pandemic. Computational fluid dynamics (CFD) has been widely used for such predictions, relying on Eulerian–Eulerian (EE) and [...] Read more.
The transport and prediction of the concentration of particles in confined spaces are crucial for human well-being; this has become particularly evident during the current worldwide pandemic. Computational fluid dynamics (CFD) has been widely used for such predictions, relying on Eulerian–Eulerian (EE) and Eulerian–Lagrangian (EL) models to study particle flow. However, there is a lack of research on industrial factories. In this study, a scaled laboratory in an industrial factory was established for oil mist particles in a machining factory, and oil mist dispersion experiments were conducted under roof exhaust and mixed ventilation conditions. After that, the oil mist concentration distribution in the factory under the same working conditions was calculated by Eulerian and Lagrangian methods, and the corresponding calculation errors and resource consumption were compared. It was found that the simulation results of both methods are acceptable for mixed ventilation and roof exhaust ventilation systems. When there are more vortices in the factory, the Lagrangian method increases the computation time by more than 53% to satisfy the computational accuracy, and the computational error between the Eulerian and Lagrangian methods becomes about 10% larger. For oil mist particles with an aerodynamic diameter of 0.5 μm, both Eulerian and Lagrangian methods have reliable accuracy. Based on the same flow field, the Lagrangian method consumes more than 400 times more computational resources than the Eulerian method. This study can provide a reference for the simulation of indoor particulate transport in industrial factories. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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18 pages, 5922 KiB  
Article
Computational Fluid and Particle Dynamics Analyses for Prediction of Airborne Infection/Spread Risks in Highway Buses: A Parametric Study
by Sung-Jun Yoo, Shori Yamauchi, Hyungyu Park and Kazuhide Ito
Fluids 2023, 8(9), 253; https://doi.org/10.3390/fluids8090253 - 17 Sep 2023
Cited by 1 | Viewed by 1624
Abstract
Highway buses are used in a wide range of commuting services and in the tourist industry. The demand for highway bus transportation has dramatically increased in the recent post-pandemic world, and airborne transmission risks may increase alongside the demand for highway buses, owing [...] Read more.
Highway buses are used in a wide range of commuting services and in the tourist industry. The demand for highway bus transportation has dramatically increased in the recent post-pandemic world, and airborne transmission risks may increase alongside the demand for highway buses, owing to a higher passenger density in bus cabins. We developed a numerical prediction method for the spatial distribution of airborne transmission risks inside bus cabins. For a computational fluid dynamics analyses, targeting two types of bus cabins, sophisticated geometries of bus cabins with realistic heating, ventilation, and air-conditioning were reproduced. The passengers in bus cabins were reproduced using computer-simulated persons. Airflow, heat, and moisture transfer analysis were conducted based on computational fluid dynamics, to predict the microclimate around passengers and the interaction between the cabin climate and passengers. Finally, droplet dispersion analysis using the Eulerian–Lagrangian method and an investigation of the spatial distribution of infection/spread risks, assuming SARS-CoV-2 infection, were performed. Through parametric analyses of passive and individual countermeasures to reduce airborne infection risks, the effectiveness of countermeasures for airborne infection was discussed. Partition installation as a passive countermeasure had an impact on the human microclimate, which decreased infection risks. The individual countermeasure, mask-wearing, almost completely prevented airborne infection. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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Review

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28 pages, 2774 KiB  
Review
Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors
by Clive B. Beggs, Rabia Abid, Fariborz Motallebi, Abdus Samad, Nithya Venkatesan and Eldad J. Avital
Fluids 2024, 9(3), 54; https://doi.org/10.3390/fluids9030054 - 22 Feb 2024
Viewed by 7658
Abstract
COVID-19 is an airborne disease, with the vast majority of infections occurring indoors. In comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors and conclude that profound differences exist, which help to explain why [...] Read more.
COVID-19 is an airborne disease, with the vast majority of infections occurring indoors. In comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors and conclude that profound differences exist, which help to explain why SARS-CoV-2 transmission is much more prevalent indoors. Near- and far-field transmission pathways are discussed along with factors that affect infection risk, with aerosol concentration, air entrainment, thermal plumes, and occupancy duration all identified as being influential. In particular, we present the fundamental equations that underpin the Wells–Riley model and show the mathematical relationship between inhaled virus particles and quanta of infection. A simple model is also presented for assessing infection risk in spaces with incomplete air mixing. Transmission risk is assessed in terms of aerosol concentration using simple 1D equations, followed by a description of thermal plume–ceiling interactions. With respect to this, we present new experimental results using Schlieren visualisation and computational fluid dynamics (CFD) based on the Eulerian–Lagrangian approach. Pathways of airborne infection are discussed, with the key differences identified between indoors and outdoors. In particular, the contribution of thermal and exhalation plumes is evaluated, and the presence of a near-field/far-field feedback loop is postulated, which is absent outdoors. Full article
(This article belongs to the Special Issue Computational Modelling of Particle Flows in Environmental and Bio-Transport Applications)
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