Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session E01: Biological Fluid Dynamics: Infectious Disease II |
Hide Abstracts |
Chair: Rajat Mittal, Johns Hopkins University Room: North 120 AB |
Sunday, November 21, 2021 2:45PM - 2:58PM |
E01.00001: Fluid dynamics of transmission in a waiting line Ruixi Lou, Devin Kenney, Varghese Mathai Waiting lines represent a critical social interaction that occurs frequently in many public spaces, such as supermarkets, voting centers, COVID-testing centers and vaccination clinics. Here will simplify these complex scenarios into a fluid mechanical problem, with an objective of assessing person-to-person transmission in the waiting line. We use a combined experimental and numerical investigation to assess the flow patterns created by periodic movements mimicking the kinematics of a waiting line. Since field experiments can be challenging during the pandemic, we apply the concept of dynamic similarity to transform the waiting-line fluid flows to a laboratory setting (with water as working fluid). A conveyor belt system mounted with 3-D printed circular cylinders (dummies), driven by a stepper motor, was used to model the people in the waiting line. We matched the relevant non-dimensional numbers: Reynolds number, reduced frequency, and dimensionless spacing to those of realistic waiting lines. UV-induced fluorescence, combined with particle imaging techniques, was used to study the unsteady flow patterns and the spreading of passive scalar. Some strategies will be proposed to reduce cross-contamination in the waiting line setting — that go beyond the six-foot guideline currently in place. |
Sunday, November 21, 2021 2:58PM - 3:11PM |
E01.00002: Effect of wetness on penetration dynamics of droplets impacted on facemasks Abhishek Saha, Sombuddha Bagchi, Saptarshi Basu, Swetaprovo Chaudhuri Properly designed facemasks can limit the spread of ballistic droplets and aerosol particles coming out of oral and nasal cavities during respiratory events, such as sneezing, coughing, singing, talking etc. Furthermore, it can also protect the user from inhaling small droplets, droplet nuclei, or aerosol particles. Thus, proper usage of facemasks can prevent the transmission of many diseases, including Covid19, influenza, measles, and the common cold. Although N95 masks are particularly designed to provide the best protection, various types of facemask became popular during the Covid19 pandemic due to a shortage of supply and high demand. In our recent study (Sharma et al. Sc. Adv. (2021) 7, eabf0452), we reported the fate of a respiratory droplet impacting on a dry facemask to show that larger droplets can penetrate the mask layers and undergo secondary atomizations leading to multiple smaller droplets. In this work, we focus on the effect of the wetness of the mask matrix on this atomization process. Indeed, due to the condensation process, longtime use renders the masks wet, and hence, its influence on the efficacy in blocking the droplet is worth investigating. We will present a regime map to show the penetration probability with impact velocity and wetness for two different types of masks. We will also present a scaling argument to explain the observed effects of wetness on penetration. |
Sunday, November 21, 2021 3:11PM - 3:24PM |
E01.00003: Characterization of point-source aerosol and airborne particle generation, dispersal, and decay in confined spaces Niloufar S Sadoughipour, Homa Momeni Eskandari, Carol Wiese, Darya Dabiri, Omid Amili, George H Choueiri At the onset of the COVID-19 pandemic, many dental offices were asked to shut down due to a perceived elevated risk of virus transmission owing to the nature of dental procedures that produce a high number of aerosolized particles ejected from the oral cavity. In this study we quantify the aerosol and airborne particle distribution in a typical dental clinic setting as a result of common dental procedures. Spatio-temporal particle concentration maps were derived from an array of approximately 40 particle sensors distributed around a dental practitioner and their assistant as well as in critical locations throughout the clinic during common dental procedures on a patient simulator. Various clinical setting scenarios were implemented; including those recommended by the Center for Disease Control; and their efficacy at reducing micron sized aerosolized particles was determined by characterizing the rates of aerosol and airborne particle generation and decay. As this study focuses on the aerosolized and airborne particles, these results can be extended to non-clinical scenarios concerning the spreading of airborne particles form a localized source in confined spaces. |
Sunday, November 21, 2021 3:24PM - 3:37PM Not Participating |
E01.00004: Drop Transmission After the Impact on Woven fabrics Yang Liu, Mehdi Vahab, Kourosh Shoele, Mark M Sussman
|
Sunday, November 21, 2021 3:37PM - 3:50PM |
E01.00005: Analytical Model to Infer Mask Peripheral Leakage Pattern in Large Population Akshay Anand, Tso-Kang Wang, Tomas Solano, Kenneth Breuer, Rajat Mittal, Kourosh Shoele Using a facemask with proper fit is an effective method to diminish the airborne transmission of pathogenic agents, and facemasks have been a critical element in our defense against COVID-19. The mask material and fit on the wearer’s face are critical to the overall effectiveness of the mask against the virus. Here, we propose an analytical integral boundary layer solution to quantify the flow field in the interface region between face and mask. The mask deployment study is performed for more than 1000 distinct morphable faces and different mask shapes. The space between the mask and face is represented with many radial interconnected channels. Each channel has a porous top boundary and extends from the inner mouth/nose high-pressure region to the mask's outer edge. The flow distribution in the channels is determined by the compatibility condition of the inlet pressure. The model is validated with a detailed flow simulation and employed to find the interconnected relation between fitness, porosity, and leakage through the mask. The results demonstrate the relation between breathability and filtration performance of the mask as a function of the mask’s permeability coefficient and fit. Finally, we discuss the statistics of peripheral leakage patterns in a large cohort of faces obtained from the model. |
Sunday, November 21, 2021 3:50PM - 4:03PM |
E01.00006: The connection between mask deformation and peripheral leakage Tomas Solano, Kourosh Shoele, Kenneth Breuer, Rajat Mittal Due to the COVID-19 pandemic, the use of face masks has been adopted by the general public as an effective method to reduce transmission. Respirators such as the N95 are highly effective at mitigating airborne diseases if properly fitted. The limited supply of these respirators led the general public to turn to more accessible protection such as surgical masks and fabric masks. The effectiveness of these masks has been shown to depend strongly on the mask material and fit. However, the aerodynamics of face masks is still not well-understood. The billowing caused by the increased pressure in the region between the mask and the face during expiratory events alters how the mask fits on the face resulting in increased peripheral leakage. Direct numerical simulations of the flow dynamics of respiratory events while wearing a face mask can be used to quantify the distribution of the peripheral leaks. Here we present a novel model for porous membranes (i.e., masks) and use it to explore the fluid-structure interactions of realistic faces wearing a fabric face mask. The mask deformation and resulting leakage jets generated from different types of faces are of particular interest. The current model can be used to inform the quantification of face mask effectiveness and guide future mask designs that reduce or redirect the leakage jets to limit the dispersion of respiratory aerosols. |
Sunday, November 21, 2021 4:03PM - 4:16PM |
E01.00007: Flow permeability and flow-induced deformations of medical face masks and mask materials Erin Tucker, Juhi Chowdhury, Jay-Young Cho, Kourosh Shoele, Rajat Mittal, Kenneth Breuer After more than a year of SARS-CoV-2 pandemic, the face mask has been recognized as the most effective and practical piece of personal protective equipment (PPE) used to minimize the virus spread. Although there have been numerous studies performed on the filtration efficiencies of different mask materials, little attention has been paid to the deformation of mask materials due to respiratory activities and how the fluid-structure interactions affect the mask fit and effectiveness. We study this performance of multiple mask materials by characterizing permeability and mechanical deformation, including the fit of the mask on the face. Several combinations of flow rates and velocities corresponding to various respiratory activities, such as breathing, sneezing, coughing, speaking, and exercising, are defined for people of different ages and genders. The deformation of several mask materials is recorded using a laser profilometer, and the permeability is calculated from a modified Darcy's Law using pressure drop measurements at various flow rate conditions. |
Sunday, November 21, 2021 4:16PM - 4:29PM |
E01.00008: Physical properties of saliva change the atomization morphology Biruk Teka Gidreta, Hyoungsoo Kim The fast spread of COVID-19 underscored the need for a better understanding of the transmission mechanism of airborne diseases. Human respiratory activities such as sneezing and coughing expel a huge amount of pathogen-laden liquids that drive the airborne transmission pathway. During drinking and eating, when mask-wearing is impractical, saliva's physical properties are changed. Accordingly, we investigate the atomization morphology of expelled saliva from the perspective of varying fluid physical properties. Using experiments on artificial saliva, on which we apply a step-function pressure profile to mimic the short and violent act of sneezing, we show that the breakup mechanism of saliva is dependent on the fluid physical properties. By analyzing high-speed images, we find that the size of the droplets formed from exhaled respiratory liquid varies with the surface tension and viscosity of saliva. Furthermore, we also show that the viscoelastic behavior of saliva has an effect on the breakup morphology of the ligaments. We observe that the fragmentation of viscoelastic filaments, which form beads-on-a-string structures, takes longer than that of Newtonian fluid filaments. Finally, based on the experimental results, we performed scaling arguments to explicate the observations. |
Sunday, November 21, 2021 4:29PM - 4:42PM |
E01.00009: DNS and assessment of the D2-law for evaporation in turbulent diluted sprays Jietuo WANG, Francesco Picano, federico Dalla Barba In many natural and applicative environments, the evaporation of dispersed droplets within high Reynolds number turbulent sprays plays an important role whose significance has been further emphasized during the outbreak of the COVID-19 pandemic. Actually, the virus SARS-CoV-2 is transmitted among human subjects through respiratory droplets expelled from an infected source during spasmodic events, such as talking, coughing, and sneezing. To better understand and model the basic mechanisms governing this phenomenon, we conducted numerical studies of a dilute turbulent spray at Re=10,000 using a Direct Numerical Simulation approach, performing a detailed statistical analysis. We firstly observed intensive preferential segregation of the dispersed phase which originates from the entrainment of environmental dry air into the mixing layer and is intensified by small-scale clustering in the far-field region, contributing to extend the spray vaporization length. On the other hand, we showed that employing the classical D2-law, often used in modeling spray evaporation, would lead to an extreme overestimation of the droplet evaporation rate, a phenomenon also recently reported in unsteady respiratory flows. From our DNS dataset, we noted that the model inaccuracy was mainly induced by the assumed value for the droplet temperature. Based on that, we propose a revision of the classical D2-law capable to accurately determine droplet evaporation rate in dilute conditions by a proper estimate of the asymptotic droplet properties. Finally, our revised D2-law model has been tested against DNS of diluted turbulent evaporating sprays showing very good agreements. |
Sunday, November 21, 2021 4:42PM - 4:55PM |
E01.00010: Thin liquid layer atomization: a simple numerical model of cough Cesar I Pairetti, Stephane L Zaleski, Leonardo Chirco, Raphael Villiers, Yue Ling
|
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700