news, journals and articles from all over the world.
The ongoing COVID-19 pandemic has led many to study airborne droplet transmission in different conditions and environments, and in Physics of Fluids, researchers from A*STAR conducted a numerical study on droplet dispersion using high fidelity air flow simulation. The scientists found a single 100-micrometer cough droplet under wind speed of 2 meters per second can travel up to 6.6 meters and even further under dry air conditions due to droplet evaporation.
Squids use a form of jet propulsion that is not well understood, especially when it comes to their hydrodynamics under turbulent flow conditions. Discovering their secrets can help create new designs for bioinspired underwater robots, so researchers are exploring the fundamental mechanism. They describe their numerical study in Physics of Fluids; among their discoveries, they found that thrust production and efficiency are underestimated within laminar, or nonturbulent, flows.
Aerosol microdroplets do not appear to be extremely efficient at spreading the virus that leads to COVID-19. While the lingering microdroplets are certainly not risk-free, due to their small size they contain less virus than the larger droplets that are produced when someone coughs, speaks, or sneezes directly on us, said researchers at the University of Amsterdam’s Van der Waals-Zeeman Institute. The results were published in Physics of Fluids.
As the pandemic continues, researchers have increasingly focused on the extent to which respiratory droplets carrying the coronavirus travel and contaminate the air after an infected person coughs. While scientists have studied the properties of air at the mouth, less is known about how these properties change as the cough cloud travels. In Physics of Fluids, researchers estimate the evolving volume of the cough cloud and quantify the reduction in its volume in the presence of a face mask.
Flow velocity distribution and particle size are key in aerosol transport, which is one of the main ways COVID-19 spreads, when aerosol particles are released during exhalation, talking, coughing, or sneezing. In Physics of Fluids, University of New Mexico researchers used computational fluid-particle dynamics to explore aerosol transport within an air-conditioned classroom model. They discovered opening windows increases the fraction of particles that exit the system by nearly 40%, while also reducing aerosol transmission between people within.
If you have been surrounded by the sight and smell of pine trees, you may have taken a closer look at the needles and then wondered how their properties are influenced by rainfall. In Physics of Fluids, researchers are currently probing how well pine needles allay the impact of rain beneath the tree. They explored the impact of raindrops onto fixed, noncircular fibers of the longleaf pine by using high-speed videography to capture the results.
As COVID-19 cases continue to rise, it is increasingly urgent to understand how climate impacts the spread of the coronavirus, particularly as winter virus infections are more common and the northern hemisphere will soon see cooler temperatures. In Physics of Fluids, researchers studied the effects of relative humidity, environmental temperature, and wind speed on the respiratory cloud and virus viability. They found a critical factor for the transmission of the infectious particles is evaporation.
Fish and seaweed secrete a layer of mucus to create a slippery surface, reducing their friction as they travel through water. A potential way to mimic this is by creating lubricant-infused surfaces covered with cavities. As the cavities are continuously filled with the lubricant, a layer is formed over the surface. In the journal Physics of Fluids, researchers in South Korea conducted simulations of this process to help explain the effects.
N95 masks achieve 95% efficiency at filtering out tiny 0.3-micron particles, while maintaining reasonable breathability, thanks to a layer of polypropylene fibers incorporating electrical charges to attract particles. Extended usage and decontamination, provoked by severe shortages during the pandemic, can easily remove the charges and degrade filtration efficiency. In Physics of Fluids, researchers share a method to restore the filtration efficiency of N95 masks to out-of-box levels, as long as the mask is not structurally compromised.
As countries experience a steep surge in COVID-19 infections, face masks have become increasingly accepted as an effective means for combating the spread of the disease when combined with social distancing and frequent hand-washing. Increasingly people are using clear plastic face shields and masks with exhalation valves instead of regular cloth or surgical masks, since they can be more comfortable. In a paper published in Physics of Fluids, researchers investigate whether they are as effective.
Months into the COVID-19 pandemic, wearing a mask while out in public has become the recommended practice. However, many still question the effectiveness of this. To allay doubts, Padmanabha Prasanna Simha, from the Indian Space Research Organisation, and Prasanna Simha Mohan Rao, from the Sri Jayadeva Institute of Cardiovascular Sciences and Research, experimentally visualized the flow fields of coughs under various common mouth covering scenarios. They present their findings in the journal Physics of Fluids.
If the mist in a dentist’s office — sent flying into the air by spinning, vibrating tools — contains a virus or some other pathogen, it is a health hazard for dentists and patients. So researchers in Illinois studied the viscoelastic properties of food-grade polymers and discovered that the forces of a vibrating tool or dentist’s drill are no match for them. Not only did a small admixture of polymers completely eliminate aerosolization, but it did so with ease.
Think you don’t need to worry about COVID-19 while using a public restroom? Researchers from Yangzhou University in China recently reported that flushing public restroom toilets can release clouds of virus-laden aerosols for you to potentially inhale. If that’s not cringeworthy enough, after running additional computer simulations, they’ve concluded that flushing urinals does likewise. In Physics of Fluids, the group shares its work simulating and tracking virus-laden particle movements when urinals are flushed.
The novel coronavirus that causes COVID-19 is thought to spread through natural respiratory activities, but little is known about how the virus is transported through the air. Scientists report in Physics of Fluids on a study of how airflow and fluid flow affect exhaled droplets that can contain the virus. Their model includes a more accurate description of air turbulence that affects an exhaled droplet’s trajectory. Calculations with their model reveal, among other things, an important and surprising effect of humid air.
Since the COVID-19 virus spreads through respiratory droplets, researchers in India set out to explore how droplets deposited on face masks or frequently touched surfaces dry. Droplets can be expelled via the mouth or nose and studies have shown a substantially reduced chance of infection once they dry. In Physics of Fluids, the researchers publish their findings that surface wetting properties to reduce the drying time of droplets could help lessen the risk of infection from coronaviruses.
In Physics of Fluids, scientists report calculations with a model of a conical-shaped root canal inside a tooth. A crucial step in this common dental procedure is irrigation, or rinsing, of the root canal cavity with an antibacterial solution, and the researchers used computational fluid dynamics to determine the effect of temperature on the cleaning efficiency: Higher temperatures can, to a point, improve cleansing, but this benefit falls off if the temperature gets too high.
If aerosol transmission of COVID-19 is confirmed to be significant, as suspected, we will need to reconsider guidelines on social distancing, ventilation systems and shared spaces. Researchers in the U.K. believe a better understanding of different droplet behaviors and their different dispersion mechanisms is also needed. In Physics of Fluids, the group presents a model that demarcates differently sized droplets. This has implications for understanding the spread of airborne diseases, because the dispersion tests revealed the absence of intermediate-sized droplets.
It is well established the COVID-19 virus is transmitted via respiratory droplets. Consequently, much research targets better understanding droplet motion and evaporation. In Physics of Fluids, researchers developed a mathematical model for the early phases of a COVID-19-like pandemic using the aerodynamics and evaporation characteristics of respiratory droplets. The researchers modeled the pandemic dynamics with a reaction mechanism and then compared the droplet cloud ejected by an infected person versus one by a healthy person.
While the use of face masks in public has been widely recommended by health officials during the current COVID-19 pandemic, there are relatively few specific guidelines pertaining to mask materials and designs. A study in Physics of Fluids looks to better understand which types are best for controlling respiratory droplets that could contain viruses. The team experimented with different choices in material and design to determine how well face masks block droplets as they exit the mouth.
Researchers used a computer simulation to show how a flushing toilet can create a cloud of virus-containing aerosol droplets that is large and widespread and lasts long enough that the droplets could be breathed in by others. With recent studies showing the COVID-19 virus can survive in the human digestive tract and show up in feces of the infected, this raises the possibility the disease could be transmitted with the use of toilets.
One of the many questions researchers have about the COVID-19 virus is how long it remains alive after someone infected coughs or sneezes. In Physics of Fluids, researchers examine the drying time of respiratory droplets from COVID-19-infected subjects on various surfaces in six cities around the world. Using a model well established in the field of interface science, the drying time calculations showed ambient temperature, type of surface and relative humidity play critical roles.
Researchers from the Indian Institute of Technology Roorkee have discovered how to make bottles empty faster, which has wide-ranging implications for many areas beyond the beverage industry. In this week’s Physics of Fluids, they explore this bottle-emptying phenomenon from the perspective of bubble dynamics on a commercial bottle by using high-speed photography. Image analysis allowed them to conceptualize various parameters, such as liquid film thickness, bubble aspect ratio, rise velocity and bottle emptying modes.
Biohydrogels have been studied closely for their potential use in biomedical applications, but they often move between sols and gels, depending on their temperature, changes that can pose issues depending on the intended use. In Physics of Fluids, researchers discuss their work studying the effect of temperature on hydrogels. They found that creating hydrogels at room temperature or below results in more robust materials that function more effectively when used in the body.
In many coastal zones and gorges, unstable cliffs often fail when the foundation rock beneath them is crushed. Large water waves can be created, threatening human safety. In this week’s Physics of Fluids, scientists reveal the mechanism by which these cliffs collapse, and how large, tsunami-like waves are created. Few experimental studies of this phenomenon have been carried out, so this work represents valuable new data that can be used to protect from impending disaster.
Acquiring a better understanding for how objects drift in the ocean has importance for many uses, but most models lack a systematic approach. One new effort looks to provide a clearer alternative. Researchers have released the results from an experiment aimed at tracking different objects as they drift in the Florida Current. Using satellite data, the group developed a new model for how objects drift. They discuss their work in this week’s Physics of Fluids.
Traditional methods of vacuum suction and previous vacuum suction devices cannot maintain suction on rough surfaces due to vacuum leakage, which leads to suction failure. Researchers Xin Li and Kaige Shi developed a zero-pressure difference method to enhance the development of vacuum suction units. Their method overcame leakage limitations by using a high-speed rotating water ring between the surface and suction cup to maintain the vacuum. They discuss their work in Physics of Fluids.
When making bread, it’s important not to overknead the dough, because this leads to a dense and tight dough due to a reduced water absorption capacity that impairs its ability to rise.
The entry probe of the Galileo mission to Jupiter entered the planet’s atmosphere in 1995 in fiery fashion, generating enough heat to cause plasma reactions on its surface. The data relayed about the burning of its heat shield differed from the effects predicted in fluid dynamics models, and new work examines what might have caused such a discrepancy.
During the past 20 years, the oil industry has begun to transition away from light oils toward heavier oils. But transporting heavy oils cost-effectively is a challenge because heavy oils are viscous — essentially a thick, sticky and semifluid mess. One way to outmaneuver this problem, reported in Physics of Fluids, is a viscoplastic lubrication technique.
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