“…Also, raised shear stress and reduced pressure in the stenosis zone were demonstrated. Moreover, the accurate choice of the boundary condition of the outflow in an actual sneeze can considerably affect the stenosis zone conditions as it also analyzes and confirmed in the previous studies (Mortazavy Beni et al 2019a , b , 2021 ; Mortazavi et al 2020 ). Images produced from CT with formatting DICOM (Digital Imaging and Communications in Medicine) were imported to Mimics software using thresholding to reconstruct the human respiratory point cloud.…”
Section: Introductionsupporting
confidence: 65%
“…Figure 3 in the graphical abstract shows step-by-step modeling of the respiratory system, including point cloud, CFD, FSI, particle deposition by discrete phase model (DPM) method, and final validation of the results using the particle image velocimetry (PIV) and stereolithography (SLA) method (Mortazavy Beni et al 2019a , b , 2021 ; Mortazavi et al 2020 ). Fig.…”
“…Also, raised shear stress and reduced pressure in the stenosis zone were demonstrated. Moreover, the accurate choice of the boundary condition of the outflow in an actual sneeze can considerably affect the stenosis zone conditions as it also analyzes and confirmed in the previous studies (Mortazavy Beni et al 2019a , b , 2021 ; Mortazavi et al 2020 ). Images produced from CT with formatting DICOM (Digital Imaging and Communications in Medicine) were imported to Mimics software using thresholding to reconstruct the human respiratory point cloud.…”
Section: Introductionsupporting
confidence: 65%
“…Figure 3 in the graphical abstract shows step-by-step modeling of the respiratory system, including point cloud, CFD, FSI, particle deposition by discrete phase model (DPM) method, and final validation of the results using the particle image velocimetry (PIV) and stereolithography (SLA) method (Mortazavy Beni et al 2019a , b , 2021 ; Mortazavi et al 2020 ). Fig.…”
“…(1) Use large eddy simulation (LES) instead of RANS model combined with overset mesh method to model the turbulence ambient airflow fields waked by the walking motion of human (Edge, Paterson, & Settles, 2005;Settles, 2006); (2) Consider the atomization and coagulation between liquid bulk and droplets using the hybrid volume of fluid (VOF)-discrete phase model (DPM) method (Balasubramanian, Kumar, Nakod, Schütze, & Rajan, 2020;Xiao, Liu, & Liu, 2019); (3) Perform extensive parametric analysis to seek for other vital factors that can influence the airborne transmission of the SARS-CoV-2 laden droplets, e.g., droplet size distributions generated by different emission activities (e.g., sneeze (Hassani & Khorramymehr, 2019), vigorous breath, and loud speech (Asadi et al, 2019)), human heights, and emitted jet waveforms, jet spread angle variability (Gupta, Lin, & Chen, 2009), mouth opening variabilities during the emission, and environmental temperature; and (4) Integrate the human respiratory system with the virtual human body shell to simulate the resultant transport and deposition of COVID-19 virus-laden droplets in airways and the stimulated immune system responses using established multiscale models (Haghnegahdar et al, 2019;Kuga et al, 2020;Zhao et al, 2019) The future work will be done continuously to enhance the fundamental understanding of the airborne transmission of SARS-CoV-2 for better preparations against the post-pandemic period with the high possibility of resurgence (Kissler et al, 2020).…”
Section: Limitations Of the Study And Future Workmentioning
It has been confirmed that the coronavirus disease 2019 (COVID-19) can transmit through droplets created when an infected human coughs or sneezes. Accordingly, 1.83-m (6-feet) social distancing is advised to reduce the spread of the disease among humans. This is based on the assumption that no air circulation exists around people. However, it is not well investigated whether the ambient wind and relative humidity (RH) will cause SARS-CoV-2 laden droplets to transport farther in the air, and make the current social distancing policy insufficient. To provide evidence and insight into the "social distancing" guidelines, a validated computational fluidparticle dynamics (CFPD) model was employed to simulate the transient transport, condensation/evaporation, and deposition of SARS-CoV-2 laden droplets emitted by coughs, with different environmental wind velocities and RHs. Initial droplet diameters range from 2 to 2000 μm, and the wind velocities range from 0 to 16 km/h, representing different wind forces from calm air to moderate breeze. The comparison between a steady-state wind and a gust with a constant frequency has also been performed. Ambient RHs are 40% and 99.5%. The distances between the two virtual humans are 1.83 m and 3.05 m (6 feet and 10 feet). The facial covering effect on reducing the airborne transmission of the cough droplets has also been evaluated. Numerical results indicate that the ambient wind will enhance the complexity of the secondary flows with recirculation between the two virtual humans. Microdroplets follow the airflow streamlines well and deposit on both human bodies and head regions, even with the 3.05-m (10-feet) separation distance. The rest of the microdroplets can transport in the air farther than 3.05 m (10 feet) due to wind convection, causing a potential health risk to nearby people. High RH will increase the droplet sizes due to the hygroscopic growth effect, which increases the deposition fractions on both humans and the ground. With the complex environmental wind and RH conditions, the 6feet social distancing policy may not be sufficient to protect the inter-person aerosol transmission, since the suspending micro-droplets were influenced by convection effects and can transport from the human coughs/sneezes to the other human in less than 5 seconds. Due to the complex real-world environmental ventilation conditions, a social distance longer than 1.83 m (6 feet) needs to be considered. Wearing masks should also be recommended for both infected and healthy humans to reduce the airborne cough droplet numbers.
“…The method allows for visualizing both bone structures and soft tissues and to segment the airways [7,12,31] by digital tomographic image processing [31,[49][50][51][52]. In addition, CFD models, which are based on computed tomography data, allow to study the aerodynamic characteristics of the upper respiratory tract [7,10,13,23,[53][54][55][56][57][58][59][60]. The works in which the correlation of the results between the data of computed tomography, rhinomanometry and acoustic rhinometry are studied are quite relevant [22,[61][62][63].…”
Section: Analysis Of Existing Methods Of Nasal Breathing Researchmentioning
This study analyzes the existing methods for studying nasal breathing. The aspects of verifying the results of rhinomanometric diagnostics according to the data of spiral computed tomography are considered, and the methodological features of dynamic posterior active rhinomanometry and the main indicators of respiration are also analyzed. The possibilities of testing respiratory olfactory disorders are considered, the analysis of errors in rhinomanometric measurements is carried out. In the conclusions, practical recommendations are given that have been developed for the design and operation of tools for functional diagnostics of nasal breathing disorders. It is advisable, according to the data of dynamic rhinomanometry, to assess the functioning of the nasal valve by the shape of the air flow rate signals during forced breathing and the structures of the soft palate by the residual nasopharyngeal pressure drop. It is imperative to take into account not only the maximum coefficient of aerodynamic nose drag, but also the values of the pressure drop and air flow rate in the area of transition to the turbulent quadratic flow regime. From the point of view of the physiology of the nasal response, it is necessary to look at the dynamic change to the current mode, given the hour of the forced response, so that it will ensure the maximum possible acidity in the legend. When planning functional rhinosurgical operations, it is necessary to apply the calculation method using computed tomography, which makes it possible to predict the functional result of surgery.
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