Nanofiber Face Masks Improve Filtration Efficiency, Need Replacing More Often

Innovations to improve mask efficacy, with increasing focus on nanofiber manufacturing, have resulted in higher filtration efficiency, greater comfort, and easier breathing capacity. However, the effects of microwater droplets on the integrity of nanofibers are relatively unclear. In Physics of Fluids, researchers examine these ambiguities through a visualization of nanofibers interacting with water aerosol exposure. They used high-speed microscopic videos to systematically visualize the evolution of nanofibers with different contact angles, diameters, and mesh sizes under water aerosol exposure.

Protruding Eyes, Mouth Make Stingrays More Hydrodynamically Efficient

In Physics of Fluids, researchers detail how the protruding eyes and mouths on simulated stingrays affect a range of forces involved in propulsion, such as pressure and vorticity. They created a computer model of a self-propelled flexible plate that mimicked a stingray’s up-and-down harmonic oscillations and used it to illustrate the complex interplay between hydrodynamic forces. The group found that the eyes and mouth help streamline stingrays even further.

Turning Plastic into Foam to Combat Pollution

In Physics of Fluids, researchers have developed a method to turn biodegradable plastic knives, spoons, and forks into a foam that can be used as insulation in walls or in flotation devices. The investigators placed the cutlery into a chamber filled with carbon dioxide. As pressure increased, the gas dissolved into the plastic. When they suddenly released the pressure in the chamber, the carbon dioxide expanded within the plastic, creating foaming.

Polymers in Meteorites Provide Clues to Early Solar System

Meteorites that do not experience high temperatures at any point in their existence provide a good record of complex chemistry present when or before our solar system was formed. So researchers have examined individual amino acids in these meteorites, many of which are not in present-day organisms. In Physics of Fluids, researchers show the existence of a systematic group of amino acid polymers across several members of the oldest meteorite class, the CV3 type.

Butterfly Effect Can Double Travel of Virus-Laden Droplets

In Physics of Fluids, investigators from the University of Florida and Lebanese American University carried out detailed computer simulations to test a mathematical theory they developed previously. They found nearly identical exhalations could spread in different directions when miniscule initial variations are substantially amplified by turbulence. This is the so-called butterfly effect.

First Wave COVID-19 Data Underestimated Pandemic Infections

Two COVID-19 pandemic curves emerged within many cities during the one-year period from March 2020 to March 2021. Oddly, the number of total daily infections reported during the first wave is much lower than that of the second, but the total number of daily deaths reported during the first wave is much higher than the second wave.

Fuel Flow, Heat Fluctuations Drive Dangerous Oscillations in Rocket Engines

Combustion engines can develop high frequency oscillations, leading to structural damage to and unsafe operating conditions. In Physics of Fluids, research clarifies the feedback processes that give rise to these oscillations. The investigators studied simulated combustion events in a computational model of a rocket combustor and their analysis involved sophisticated techniques, including symbolic dynamics and the use of complex networks to understand the transition into oscillatory behavior.

Normal Breathing Sends Saliva Droplets 7 Feet; Masks Shorten This

The WHO and the CDC recommend keeping a certain distance between people to prevent the spread of COVID-19. These social distancing recommendations are estimated from a variety of studies, but further research about the precise mechanism of virus transport is still needed. In Physics of Fluids, researchers demonstrate normal breathing indoors without a mask can transport saliva droplets capable of carrying virus particles to a distance of 2.2 meters in a matter of 90 seconds.

Cost-Effective, Easily Manufactured Ventilators for COVID-19 Patients

Particle physicists are at the forefront for pioneering low-cost, mass-producible ventilators to help address the worldwide shortage. An international, interdisciplinary team spearheaded one such effort and presents the design in Physics of Fluids. The ventilator consists of a gas inlet valve and a gas outlet valve, with controls and alarms to ensure proper monitoring and customizability from patient to patient. The design is built from readily available parts and is presented under an open license.

Controlling Sloshing Motions in Sea-Based Fish Farming Cages Improves Fish Welfare

Sea-based fish farming systems using net pens are hard on the environment and fish. A closed cage can improve fish welfare, but seawater must be continuously circulated through the cage. However, waves can cause the water to slosh inside the cage, creating violent motions and endangering the cage and fish. A study using a scale-model containment system is reported in Physics of Fluids and shows why violent sloshing motions arise and how to minimize them.

Irradiating COVID-19 Cough Droplets with UV-C Lamps

The extreme confusion at the beginning of the pandemic inspired Marche Polytechnic University researchers, who happen to be intrigued by saliva droplet diffusion, to search for answers and ways to help. In Physics of Fluids, they describe using a supercomputer to do numerical modeling of cough droplets irradiated by UV-C light. They also report exploring the social distances required to prevent virus transmission.

Complex Fluid Dynamics May Explain Hydroplaning

Research into hydroplaning currently uses a test track equipped with a transparent window embedded in the ground. The area above is flooded and a tire rolling over the window is observed with a high-speed camera. Investigators in France have developed a more sophisticated approach involving fluorescent seeding particles to visualize the flow and used a sheet of laser light to illuminate the area. They discuss their work in Physics of Fluids.

Simply Speaking While Infected Can Potentially Spread COVID-19

COVID-19 can spread from asymptomatic but infected people through small aerosol droplets in their exhaled breath. Most studies of the flow of exhaled air have focused on coughing or sneezing; however, speaking while near one another is also risky. In Physics of Fluids, scientists used smoke and laser light to study the flow of expelled breath near and around two people conversing in various relative postures commonly found in the service industry, such as in hair salons, medical exam rooms, or long-term care facilities.

Advanced Simulations Reveal How Air Conditioning Spreads COVID-19 Aerosols

A restaurant outbreak in China was widely reported as strong evidence of airflow-induced transmission of COVID-19, but it lacked a detailed investigation about exactly how transmission occurred. In Physics of Fluids, researchers at the University of Minnesota report using advanced simulation methods to capture the complex flows that occur when the cold airflow from air conditioners interacts with the hot plume from a dining table and the transport of virus-loading particles within such flows.

Porous Materials Unfavorable for Coronavirus Survival

As COVID-19 spreads via respiratory droplets, researchers have become increasingly interested in the drying of droplets on impermeable and porous surfaces; surfaces that accelerate evaporation can decelerate the spread of the virus. In Physics of Fluids, researchers show a droplet remains liquid for a much shorter time on a porous surface, making it less favorable to survival of the virus. On paper and cloth, the virus survived for only three hours and two days, respectively.

Why Food Sticks to Nonstick Frying Pans

Foods will sometimes get stuck to a heated surface, even if oil or a nonstick frying pan is used. Scientists have investigated the fluid properties of oil on a flat surface and their work, reported in Physics of Fluids, shows convection may be to blame. When the pan is heated from below, a temperature gradient is established in the oil film, as well as a surface tension gradient. This gradient sets up a type of convection known as thermocapillary convection.

Temperature, Humidity, Wind Predict Second Wave of Pandemic

The “second wave” of the coronavirus pandemic has placed much blame on a lack of appropriate safety measures. However, due to the impacts of weather, research suggests two outbreaks per year are inevitable. Though face masks, travel restrictions, and social distancing guidelines help slow the number of new infections in the short term, the lack of climate effects incorporated into epidemiological models presents a glaring hole that can cause long-term effects. In Physics of Fluids, researchers discuss the impacts of these parameters.

Air Purifiers May Do More Harm Than Good in Confined Spaces with Airborne Viruses

The positions of air inlets and outlets in confined spaces, such as elevators, greatly affect airborne virus transmission. In Physics of Fluids, researchers show air purifiers may actually increase the spread. They use ultraviolet radiation to kill viruses and other microbes, but they also circulate air, sucking it in and exhausting cleaned air. This adds to overall circulation.

Eggs Reveal What May Happen to Brain on Impact

Our brains consist of soft matter bathed in watery cerebrospinal fluid inside a hard skull, and in Physics of Fluids, researchers describe studying another system with the same features, an egg, to search for answers about concussions. Considering that in most concussive brain injuries, the skull does not break, they wanted to find out if it was possible to break or deform the egg yolk without breaking the eggshell and did a simple experiment using an egg scrambler, measuring the soft matter deformation.

Disposable Helmet Retains Cough Droplets, Minimizes Transmission to Dentists, Otolaryngologists

Dentists and otolaryngologists are at particular risk of infection of COVID-19, since they need direct access to the mouth, nose, and throat of patients. The current solutions are expensive, not highly effective, and not very accessible. In Physics of Fluids, researchers discuss their design of an open-faced helmet for patient use that is connected to a medical-grade air filtration pump from the top that creates a reverse flow of air to prevent cough droplets from exiting the helmet.

Hand-Held Device Measures Aerosols for Coronavirus Risk Assessment

Understanding aerosol concentrations and persistence in public spaces can help determine infection risks. However, measuring these concentrations is difficult, requiring specialized personnel and equipment. Now, researchers demonstrate that a commercial hand-held particle counter can be used for this purpose and help determine the impacts of risk-reducing measures, like ventilation improvements. They describe the quick and easy, portable process in the journal Physics of Fluids.

The Mask Matters: How Masks Affect Airflow, Protection Effectiveness

Even though it has been widely known that wearing a face mask will help mitigate the community spread of COVID-19, less is known regarding the specific effectiveness of masks in reducing the viral load in the respiratory tracts of those wearing them. In Physics of Fluids, researchers examined the effect of wearing a three-layer surgical mask on inspiratory airflows and the mask’s effects on the inhalation and deposition of ambient particles in the upper respiratory airways.

Fast Walking in Narrow Corridors Can Increase COVID-19 Transmission Risk

Simulations have been used to predict droplet dispersal patterns in situations where COVID-19 might be spread and results in Physics of Fluids show the importance of the space shape in modeling how droplets move. The simulations are used to determine flow patterns behind a walking individual in spaces of different shape. The results reveal a higher transmission risk for children in some instances, such as behind quickly moving people in a long narrow hallway.

Face Masks Slow Spread of COVID-19; Types of Masks, Length of Use Matter

Using face masks to help slow the spread of COVID-19 has been widely recommended by health professionals. This has triggered studies of the materials, design, and other issues affecting the way face masks work. In Physics of Fluids, investigators looked at research on face masks and their use and summarized what we know about the way they filter or block the virus. They also summarize design issues that still need to be addressed.

COVID-19 Virus Survives on Surfaces Within Thin Film

To find out how the COVID-19 virus survives on surfaces, researchers in India are exploring the drying times of thin liquid films that persist on surfaces after most respiratory droplets evaporate. While the drying time of typical respiratory droplets is on the order of seconds, the survival time of the COVID-19 virus was found to be on the order of hours. In Physics of Fluids, the researchers describe how a nanometers-thick liquid film clings to the surface, allowing the virus to survive.

Plasma Treatments Quickly Kill Coronavirus on Surfaces

Researchers from UCLA believe using plasma could promise a significant breakthrough in the fight against the spread of COVID-19. In Physics of Fluids, modeling conducted showed strains of the coronavirus on surfaces like metal, leather, and plastic were killed in as little as 30 seconds of treatment with argon-fed, cold atmospheric plasma. The researchers used an atmospheric pressure plasma jet they built with a 3D printer to spray surfaces that were treated with SARS-CoV-2 cultures.

Valves on N95 Masks Do Not Filter Exhaled Droplets

Matthew Staymates, fluid dynamicist at the National Institute of Standards and Technology, is studying different mask types to determine which are the most effective at reducing disease transmission. In Physics of Fluids, he describes exploring the basic flow dynamics of N95 masks with or without exhalation valves. To do this, he generates stunning video from his schlieren imaging, a method to visualize the fluid flow away from the surface of an object, and light scattering.

Tracking Flight Trajectory of Evaporating Cough Droplets

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.

Squid Jet Propulsion Can Enhance Design of Underwater Robots, Vehicles

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 Inefficient Carriers Of COVID-19 Virus

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.

COVID-19 Cough Clouds in Closed Spaces

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.

Keeping COVID-19 Out of Classrooms: Open Windows, Use Glass Screens In Front of Desks

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.

Evolution of Pine Needles Helps Trees Cope with Rainfall Impact

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.

Evaporation Critical to Coronavirus Transmission as Weather Changes

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, Seaweed Inspire Slippery Surfaces for Ships

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.

Recharging N95 Masks for Continued Usage

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.

Face Shields, Masks with Valves Ineffective Against COVID-19 Spread

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.

Polymers Prevent Potentially Hazardous Mist During Dentist Visit

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.

Effectiveness of Cloth Masks Depends on Type of Covering

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.

Using A Public Restroom? Mask Up!

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.

Humid Air Can Extend Lifetime of Virus-Laden Aerosol Droplets

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.

Masks, PPE Materials Should Be Hydrophilic

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.

Using Physics to Improve Root Canal Efficiency

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.

Droplet Spread from Humans Doesn’t Always Follow Airflow

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.

Respiratory Droplet Motion, Evaporation and Spread of COVID-19-Type Pandemics

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.

Face Mask Construction, Materials Matter for Containing Coughing, Sneezing Droplets

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.

Flushing Toilets Create Clouds of Virus-Containing Particles

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.

Survival of Coronavirus in Different Cities, on Different Surfaces

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.