To respond to the ongoing pandemic of SARS-CoV-2, this contribution deals with recently highlighted COVID-19 transmission through respiratory droplets in form of aerosols. Unlike other recent studies that focused on airborne transmission routes, this work addresses aerosol transport and deposition in a human respiratory tract. The contribution therefore conducts a computational study of aerosol deposition in digital replicas of human airways, which include the oral cavity, larynx and tracheobronchial airways down to the 12th generation of branching. Breathing through the oral cavity allows the air with aerosols to directly impact the larynx and tracheobronchial airways and can be viewed as one of the worst cases in terms of inhalation rate and aerosol load. The implemented computational model is based on Lagrangian particle tracking in Reynolds-Averaged Navier–Stokes resolved turbulent flow. Within this framework, the effects of different flow rates, particle diameters and lung sizes are investigated to enable new insights into local particle deposition behavior and therefore virus loads among selected age groups. We identify a signicant increase of aerosol deposition in the upper airways and thus a strong reduction of virus load in the lower airways for younger individuals. Based on our findings, we propose a possible relation between the younger age related fluid mechanical protection of the lower lung regions due to the airway size and a reduced risk of developing a severe respiratory illness originating from COVID-19 airborne transmission.

Since end of 2019 the COVID-19 pandemic, caused by the SARS-CoV-2 virus, is threatening humanity. Despite the fact that various scientists across the globe try to shed a light on this new respiratory disease, it is not yet fully understood. Unlike many studies on the geographical spread of the pandemic, including the study of external transmission routes, this work focuses on droplet and aerosol transport and their deposition inside the human airways. For this purpose, a digital replica of the human airways is used and particle transport under various levels of cardiovascular activity in enclosed spaces is studied by means of computational fluid dynamics. The influence of the room size, where the activity takes place, and the aerosol concentration is studied. The contribution aims to assess the risk of various levels of exercising while inhaling infectious pathogens to gain further insights in the deposition behavior of aerosols in the human airways. The size distribution of the expiratory droplets or aerosols plays a crucial role for the disease onset and progression. As the size of the expiratory droplets and aerosols differs for various exhaling scenarios, reported experimental particle size distributions are taken into account when setting up the environmental conditions. To model the aerosol deposition we employ $$\text{OpenFOAM}$$ OpenFOAM  by using an Euler-Lagrangian frame including Reynolds-Averaged Navier–Stokes resolved turbulent flow. Within this study, the effects of different exercise levels and thus breathing rates as well as particle size distributions and room sizes are investigated to enable new insights into the local particle deposition in the human airway and virus loads. A general observation can be made that exercising at higher levels of activity is increasing the risk to develop a severe cause of the COVID-19 disease due to the increased aerosolized volume that reaches into the lower airways, thus the knowledge of the inhaled particle dynamics in the human airways at various exercising levels provides valuable information for infection control strategies.

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This work deals with taking advantage of the available numerical methods when trying to excel in automotive competition. First, the optimization problem is outlined, to be followed by the proposed numerical solution, as well as the practical consequences of this solution, not as a proof of validity of the numerical approach, but rather as a description of a modern design flow.Formula SAE is an international competition having the common goal of designing and manufacturing of a racing car. While efforts have been made to keep the average velocity as low as possible, for safety reasons (around 50 km/h), by designing an especially tortuous track, there is fierce competition among competitors. This, rather low, velocity presents an additional challenge before the designerincreasing downforce results in higher corner speeds, and this, in turn, leads to better final times during the competition. The design criterion was, therefore, to construct, and manufacture a vehicle which exerted as much downforce as possible.The body of work related to the rear wings has been performed at Monash University see Wordley and Saunders [1]. However, their work covered 2D computational fluid dynamics (CFD) analysis citing availability of a full-scale wind tunnel. This approach, while completely understandable, is not suitable for those without access to such expensive facilities. We believe and have proven in this work, that similar results can be achieved using full-scale 3D CFD modeling. In addition, we believed that modeling rotating wheels and a moving road were absolutely necessary in order to achieve meaningful results. Also, Wordley and Saunders [1] were not concerned with optimization of height but were rather changing the angle of attack, such approach being understandable for wind tunnel tests. Doddegowda et al. [2] have also shown generally agreeable computational results without focusing on particular parts of the car. On the contrary, De Silva et al.[3] used CFD for fine-tuning of side panels in order to maximize the use of cooling air. They used moving ground however, not spinning wheels, which, in our opinion, is absolutely necessary to capture the vortex formation around the side walls of the car. The importance of a rotating wheel was, albeit from a different perspective, confirmed by Huminic and Chiru [4].The surprising scientific result shown herein is that the effect of the slat was more pronounced than the effect of the second flap, for the maximum angle of attack, at the upmost main rear wing position, and this is documented herein. Unfortunately, the final design could not incorporate this result as this would • Several different layouts were analyzed. Optimization of SAE Formula Rear Wing• The addition of a slat at the expense of a second flap results in significant increase of downforce (about 6 %).• Boundary layer separation causes a significant decrease in lift, and occurs for higher angles of attack in the case of using a slat as opposed to the case without a slat and with the second flap.

This paper presents and discusses the results of the "2022 International Computational Fluid Dynamics Challenge on violent expiratory events" aimed at assessing the ability of different computational codes and turbulence models to reproduce the flow generated by a rapid prototypical exhalation and the dispersion of the aerosol cloud it produces. Given a common flow configuration, a total of seven research teams from different countries have performed a total of eleven numerical simulations of the flow dispersion by solving the Unsteady Reynolds Averaged Navier-Stokes (URANS) or using the Large-Eddy Simulations (LES) or hybrid (URANS-LES) techniques. The results of each team have been compared with each other and assessed against a Direct Numerical Simulation (DNS) of the exact same flow. The DNS results are used as reference solution to determine the deviation of each modeling approach. The dispersion of both evaporative and non-evaporative particle clouds has been considered in twelve simulations using URANS and LES. Most of the models predict reasonably well the shape and the horizontal and vertical ranges of the buoyant thermal cloud generated by the warm exhalation into an initially quiescent colder ambient. However, the vertical turbulent mixing is generally underpredicted, especially by the URANS-based simulations, independently of the specific turbulence model used (and only to a lesser extent by LES). In comparison to DNS, both approaches are found to overpredict the horizontal range covered by the small particle cloud that tends to remain afloat within the thermal cloud well after the flow injection has ceased.