Airflow Dynamics of Human Jets: Sneezing and Breathing - Potential Sources of Infectious Aerosols

10.1371/journal.pone.0059970PLoS ONE84

Fluid dynamics of biological and mechanical olfaction

The sense of smell is critical to a number of animals, from moths all the way to the largest mammal on land, the elephant. Despite these animals ranging across eight orders of magnitude in body mass, there are commonalities in their methods for bringing odor molecules to their sensors. Understanding the olfaction of animals can also inspire the design of autonomous smelling machines, which are currently limited in their speed and sensitivity. Most previous work on olfaction has focused on the neuroscience of animal olfaction or the algorithms involved in processing data from machine olfaction. In this dissertation, we focus on the fluid mechanics of olfaction. We used a combined experimental and theoretical approach, with particular emphasis on building machines that can mimic the olfaction of animals. We show that many animals have a hierarchical structure to their olfaction systems, either antenna or nasal cavities, that increase their surface area to improve the chance of odor deposition. Animals optimize their olfaction with behaviors varying from sniffing to angling their antenna obliquely to the wind. Both methods slow down the air near the sensing surfaces, which increases the number of molecules that can deposit by diffusion.Ph.D

Application of a model for assessing the infection risk from COVID-19 in indoor environment

La tesi tratta l'implementazione di un modello per la valutazione del rischio di infezione per via aerea da COVID-19 in ambiente confinato. Il codice è sviluppato a partire da modelli di rischio esistenti tratti dalla letteratura. L'idea di base è quella di accoppiare il calcolo del rischio ad un modello di ventilazione zonale, il quale valuta il campo di moto dell'aria ambiente previa discretizzazione spaziale dello stesso. L'obiettivo è valutare l'influenza di alcuni parametri sul rischio

Numerical modelling of micron particle inhalation in a realistic nasal airway with pediatric adenoid hypertrophy: A virtual comparison between pre- and postoperative models

Adenoid hypertrophy (AH) is an obstructive condition due to enlarged adenoids, causing mouth breathing, nasal blockage, snoring and/or restless sleep. While reliable diagnostic techniques, such as lateral soft tissue x-ray imaging or flexible nasopharyngoscopy, have been widely adopted in general practice, the actual impact of airway obstruction on nasal airflow and inhalation exposure to drug aerosols remains largely unknown. In this study, the effects of adenoid hypertrophy on airflow and micron particle inhalation exposure characteristics were analysed by virtually comparing pre- and postoperative models based on a realistic 3-year-old nasal airway with AH. More specifically, detailed comparison focused on anatomical shape variations, overall airflow and olfactory ventilation, associated particle deposition in overall and local regions were conducted. Our results indicate that the enlarged adenoid tissue can significantly alter the airflow fields. By virtually removing the enlarged tissue and restoring the airway, peak velocity and wall shear stress were restored, and olfactory ventilation was considerably improved (with a 16∼63% improvement in terms of local ventilation speed). Furthermore, particle deposition results revealed that nasal airway with AH exhibits higher particle filtration tendency with densely packed deposition hot spots being observed along the floor region and enlarged adenoid tissue area. While for the postoperative model, the deposition curve was shifted to the right. The local deposition efficiency results demonstrated that more particles with larger inertia can be delivered to the targeted affected area following Adenoidectomy (Adenoid Removal). Research findings are expected to provide scientific evidence for adenoidectomy planning and aerosol therapy following Adenoidectomy, which can substantially improve present clinical treatment outcomes.</p

Advantages and Disadvantages of Electronic Cigarettes

Electronic cigarettes (ECs) have been present on the consumer market for over a decade, and the number of related scientific publications in the PubMed database has now exceeded seven thousand. Despite the number of publications, there is still no consensus in the scientific community regarding their safety. However, it should be emphasized that a comparison of equivalent quantities of tobacco smoke and the aerosol produced from e-cigarettes showed that there was a significantly lower quantity of toxic compounds in the aerosol compared with the tobacco smoke. Therefore, the use of ECs could be seen as a way of reducing the health damage to cigarette smokers who cannot or are unwilling to quit using conventional methods. In addition, randomized studies are emerging suggesting that ECs could be useful in smoking cessation. On the other hand, ECs are now widely used among adolescents and may pose a serious risk of future nicotine dependence and health problems in this population, as they counteract their advantages in the population gained from smokers who quit using them. Therefore, as most authors stress, further research that will convincingly resolve the current controversies is needed. Clinicians urgently need evidence-based knowledge to better inform their patients about the use of these emerging tobacco products as a harm-reduction strategy, and regulators should regulate these products in ways that best serve public health, especially taking the youth population into account

Acute asthma and recovered airway tree geometry modeling and CFD simulation

This study focuses primarily on the development of modeling approaches for the reconstruction of lung airway tree and arterial vessel geometry models which will assist practical clinical studies. Anatomically-precise geometric models of human airways and arterial vessels play a critical role in the analysis of air and blood flows in human bodies. The generic geometric modeling methods become invalid when the model consists of both trachea and bronchioles or very small vessels. This thesis presents a new region-based method to reconstruct the entire airway tree and carotid vessels from point clouds obtained from CT or MR images. A novel layer-by-layer searching algorithm has been developed to recognize the branches of the airway tree and arterial vessels from the entire point clouds. Instead of applying a uniform accuracy on all branches regardless of the number of available points, the surface patches on each branch are constructed adaptively based on the number of available elemental points, which leads to the elimination of distortions occurring at small bronchi and vessels. Acute asthma is a serious disease of the respiratory system. To understand the difference in geometry and airflow patterns between acute asthma affected and recovered airway trees, a comparison study has been conducted in this research. Two computational models of the airway tree up to six generations deep were reconstructed from computed tomography (CT) scans from a single patient. The first scan was taken one day after an acute asthma episode and the second scan was taken thirty days later when the patient had recovered. The reconstructed models were used to investigate the effects of acute asthma on realistic airway geometry, airflow patterns, pressure drops, and the implications for targeted drug delivery. Comparisons in the geometry found that in general the right side of the airway is larger in diameter than the left side. The recovery of the airway was most significant in the severely asthma affected regions. Additionally the right airway branches exhibited greater dilation after recovery in comparison with the left airway especially from the fifth generation onwards. It was also found that bifurcation angles do not vary significantly between the two models, however small changes were observed which may be caused by the physical scans of the patient being taken at different times. The inhalation effort to overcome airway resistance in the asthma affected model was twice as high as that for the recovered model. Local flow patterns showed that the changes in the airway had significant influence on flow patterns. This was especially true in the region where the airway narrowing was most severe