scholarly journals Aerodynamic Dispersion of Respiratory Droplets and Aerosols by Turbulent Airflow

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 119
Author(s):  
Pablo Cornejo ◽  
Nicolás Guerrero ◽  
Vicente Sandoval
Keyword(s):  
Velocity Field ◽  
Social Interactions ◽  
Scientific Evidence ◽  
Public Debate ◽  
Dispersion Characteristics ◽  
Air Velocity ◽  
Turbulent Airflow ◽  
Ballistic Trajectory ◽  
Precautionary Measures ◽  
Respiratory Droplets

The precautionary measures recommended during the current COVID-19 pandemic do not consider the effect of turbulent airflow. We found the propagation of droplets and aerosols highly affected by this condition. The spread of respiratory droplets by the action of sneezing is characterized by the dynamics of two groups of droplets of different sizes: Larger droplets (300–900 μm) have a ballistic trajectory and can be spread up to 5 m, while a cloud of smaller droplets (100–200 μm) can be transported and dispersed at longer distances up to 18 m by the action of the turbulent airflow. In relation to the spread of exhaled aerosols during respiration, these remain in the air for long periods of time. In the presence of intense or moderate airflow, this set of particles follow airflow streamlines, and thus their propagation is directly determined by the air velocity field. Given the scientific evidence, these results should be considered in public debate about the aerodynamic dispersion characteristics of scenarios where social interactions occur and about the measures to mitigate the spread of the virus.

Airflow Simulation of the Huge Telescope Assemble

2010 ◽  
Vol 439-440 ◽  
pp. 880-883
Author(s):  
Fu Zhao ◽  
Ping Wang ◽  
Yan Jue Gong ◽  
Yu De Liu ◽  
Hong Bin Xin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Convection ◽  
Temperature Distribution ◽  
Velocity Field ◽  
Three Dimensional ◽  
Horizontal Line ◽  
Air Velocity ◽  
Turbulent Airflow ◽  
Dynamics Method

With the three-dimensional computational fluid dynamics method, the airflow effects over the huge telescope assemble is investigated in this article. The distributing of velocity field and natural convection are studied by modeling and simulating the turbulent airflow of the huge telescope. Numerical simulations show the best observation direction is the 90o angle between the main optics axis and the horizontal line in which the air velocity distribution is the least. And the air temperature distribution and uniformity around the telescope are also provided by simulation.

The Sanitary and Phytosanitary Agreement of the World Trade Organization: Debunking Its Reliance on Scientific Evidence and Reluctance to Endorse Potential Biotechnology Risks

2021 ◽  
pp. 1-17
Author(s):  
Muhammad ISLAM
Keyword(s):  
Risk Assessment ◽  
World Trade Organization ◽  
World Trade ◽  
Dispute Settlement ◽  
Scientific Evidence ◽  
Scientific Uncertainty ◽  
The World ◽  
Precautionary Measures ◽  
Phytosanitary Measures ◽  
Biotech Products

The World Trade Organization (WTO) Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement) relies on scientific evidence as a conclusive risk assessment criterion, which ignores the inherent limitations of science. This article highlights certain trade-restrictive effects of scientific evidence and comments on the Agreement’s aversions to precautionary measures and the consumer concern of the harmful effects of biotech products that may be necessary to protect public health and biosecurity in many WTO Member States. These measures and concerns have become pressing issues due to surging consumer awareness and vigilance concerning environmental protection and food safety. The Agreement is yet to overcome the weaknesses of its endorsed international standardising bodies, the problematic definition of scientific evidence and treatment of justification for scientific risk assessment methods and the implementation difficulties faced by most developing states. This article analyses these issues under the provisions of the Agreement and the interpretations of the WTO Dispute Settlement Body in disputes involving SPS matters, which fall short of addressing scientific uncertainty surrounding biotech products and their associated risks.

scholarly journals Promoting Interpersonal Relationships through Elbow Tag, a Traditional Sporting Game. A Multidimensional Approach

2021 ◽  
Vol 13 (14) ◽  
pp. 7887
Author(s):  
Verónica Muñoz-Arroyave ◽  
Miguel Pic ◽  
Rafael Luchoro-Parrilla ◽  
Jorge Serna ◽  
Cristòfol Salas-Santandreu ◽  
...  
Keyword(s):  
Decision Making ◽  
Social Interactions ◽  
Interpersonal Relationships ◽  
Predictive Power ◽  
Ad Hoc ◽  
Scientific Evidence ◽  
Point Of View ◽  
Registration System ◽  
Motor Behaviors ◽  
Quasi Experimental

The aim of this research was to study from a multidimensional point of view (decisional, relational and energetic) the interpersonal relationships established by girls and boys in the traditional sport game of Elbow Tag. Scientific evidence has shown that Traditional Sport Games (TSG) trigger different effects on male and female genders in relation to emotional experiences, decision-making, conflicts and motor relationships. Despite the fact that these dimensions are intertwined, there are hardly any studies that interpret motor behaviors holistically, i.e., taking a multidimensional (360°) view of these dimensions. For this study, a quasi-experimental design was used and a type III design was applied, inspired by the observational methodology N/P/M. A total of 147 university students participated (M = 19.6, SD = 2.3): 47 girls (31.97%) and 100 boys (68.02%). A mixed ‘ad hoc’ registration system was designed with acceptable margins of data quality. Cross-tabulations, classification trees and T-patterns analysis were applied. The results indicated that social interactions between girls and boys in a mixed group were unequal. This difference was mainly due to decision-making (sub-role variable), which has much greater predictive power than the energetic variables (MV and steps).

Why scientific evidence is no longer enough in public debate

2021 ◽  
Author(s):  
Toby Pilditch
Keyword(s):  
Climate Change ◽  
Scientific Evidence ◽  
Public Debate ◽  
Climate Change Denial ◽  
Overwhelming Evidence ◽  
Global Problems

Many of the global problems humanity is facing concern acting appropriately given the available evidence. However, issues including climate change denial (McGlade and Ekins, 2015; Steffen et al., 2015) and anti-vaccination movements (Hargreaves, Lewis, and Speers, 2003; Petrovic, Roberts, and Ramsay, 2001) appear to run contrary to overwhelming evidence. The investigation of these issues has pointed to two possible causes; either insufficient exposure to the evidence at hand, or ulterior / biased motives5. Here I show such explanations are unnecessary, and further, why current counterarguments focussed on scientific evidence may not only be ineffective, but may backfire. I highlight that denialist arguments focusing on credibility-based attacks can provoke rational scepticism of the issue at hand, requiring a shift in counterargument strategy – away from the evidence itself. I show the maximally effective counterargument strategy is to separately and directly address credibility-attacks, salvaging both the immediate issue, and future debate.

Effect of Initial Velocity Field on Smoke Diffusion Characteristic in Subway Tunnel

2009 ◽  
Author(s):  
Hui Yang ◽  
Li Jia ◽  
Lixin Yang
Keyword(s):  
Velocity Field ◽  
Field Condition ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Wind Effect ◽  
Diffusion Characteristic ◽  
Subway Tunnel ◽  
Air Velocity ◽  
Initial Field ◽  
Fire Disaster

In this paper, piston wind effect on smoke diffusion characteristic in subway tunnel is studied by using three-dimensional transient computational fluid dynamics (CFD) method. In the first simulation case, fire disaster is simulated with homogeneous resting initial field condition. In the second simulation case, the train’s decelerating process till stopping in the tunnel is simulated for getting three-dimensional tunnel air velocity field distribution. Then the final heterogeneous air velocity field when the train stops in the tunnel is taken as initial field condition and the same fire scenario as the first case is simulated again. The data obtained under both initial conditions are compared by detecting people evacuation safety and the influence of initial air velocity field is analyzed. The results show that the inertial air velocity field caused by train’s movement has significant influence on smoke diffusion at the first few minutes of fire disaster, which is the key time for people’s evacuation. The adopted method in this paper and the simulation result could be used in establishing more effective subway fire evacuation plan.

scholarly journals Calculation of turbulent diffusion jets under effects of gravity and moving surrounding air

2001 ◽  
Vol 23 (2) ◽  
pp. 87-94
Author(s):  
Bui Van Ga ◽  
Nhan Hong Quang ◽  
Jean Marc Vignon
Keyword(s):  
Velocity Field ◽  
Turbulent Diffusion ◽  
Concentration Field ◽  
Integral Model ◽  
System Of Equations ◽  
Kutta Method ◽  
Air Velocity ◽  
Runge Kutta Method ◽  
Jet Axis ◽  
General Conditions

The basis theory for the turbulent diffusion of jet and flame has been presented previously [1, 2]. But that one applies only in quiet surrounding air with the effects of buoyancy neglected. In the present paper, the theory is developed further by establishing an integral model for a jet in more general conditions with variable inclined angles, under effects of gravity and surrounding air velocity in any direction compared to the jet axis. The system of equations is closed by turbulence k-E model and is solved by 4th order Runge-Kutta method. In the first stage, the model is applied to predict the velocity field, the concentration field and with development of a 0.3 m diameter jet.

scholarly journals Unsteady RANS Simulation of Air Distribution in a Ventilated Classroom with Numerous Jets

2019 ◽  
Vol 111 ◽  
pp. 02010
Author(s):  
Nikolay Ivanov ◽  
Marina Zasimova ◽  
Evgueni Smirnov ◽  
Alexey Abramov ◽  
Detelin Markov ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Flow Structure ◽  
Air Distribution ◽  
Air Velocity ◽  
3D Flow ◽  
Ansys Fluent ◽  
Test Conditions ◽  
Rectangular Form ◽  
Unsteady Rans

The study is devoted to the Unsteady Reynolds-Averaged Navies-Stokes (URANS) simulation of ventilation in an isothermal room with numerous jets supplied from ceiling diffusers. The computations of the airflow under the test conditions considered were carried out in the classroom of the Technical University of Sofia with no occupants. The room floor has a simple rectangular form, but several columns, beams, window sills, and four radiators are located inside the room that makes the geometry more complex. Air is supplied to the room through four ceiling fan coils, the Reynolds number is 2×104. Calculations were carried out using the ANSYS Fluent 18.2 software with the standard k-ε turbulence model chosen. Computational meshes of up to 33 million hexahedral cells clustered to the inlet and outlet sections were used. The main aim of the study presented is to analyze and discuss the complicated 3D flow structure in the room and to give foundation for future measurements of air velocity field in the room.

Direct and Compensatory Parental Responses to Peer Victimization

2020 ◽  
Vol 41 (1) ◽  
pp. 197-217 ◽  
Author(s):  
Stephen A. Erath ◽  
Gregory S. Pettit ◽  
Wendy Troop-Gordon
Keyword(s):  
Social Interactions ◽  
Peer Victimization ◽  
Psychological Health ◽  
Parental Influence ◽  
Scientific Evidence ◽  
Future Research ◽  
Activity Involvement ◽  
Parental Responses ◽  
Support Activity

Scientific evidence for effective parental responses to peer victimization (PRPV) is sorely lacking. In this conceptual article, we first consider direct parental efforts to reduce peer victimization (i.e., direct PRPV) through explicitly coaching children about how to cope with peer victimization or intervening in the situation. We encourage researchers to examine whether and how direct PRPV may be successful, acknowledge possible limitations, and explore other forms of parental influence in the context of peer victimization. As an alternative or supplemental approach, we describe indirect, or compensatory, parental efforts to support the psychological health of children who experience peer victimization (i.e., compensatory PRPV). We provide illustrations of compensatory PRPV in which parents step up their efforts to encourage positive self-appraisals, facilitate positive social interactions, and support activity involvement in response to children’s experiences of peer victimization. We also suggest directions for future research on PRPV.

Influence of the Ventilation Apertures on Low Voltage Switchboard Heating

2016 ◽  
Vol 856 ◽  
pp. 368-373 ◽  
Author(s):  
Ivan Yatchev ◽  
Ivan Hadzhiev ◽  
Dian Malamov
Keyword(s):  
Velocity Field ◽  
Computer Model ◽  
Thermal Field ◽  
Low Voltage ◽  
Forced Ventilation ◽  
Air Velocity

The paper presents a computer model, developed in the software programme Comsol, for studying the influence of the ventilation apertures on low voltage (LV) switchboard heating. Results have been obtained, concerning the distribution of the LV switchboard thermal field and air velocity field in cases of closed LV switchboards and switchboards with ventilation apertures both at natural and forced ventilation. The influence of the ventilation apertures location, as well as of the air velocity at forced ventilation, on heating the current carrying circuits in the LV switchboard has been studied.

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