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.

Scientists Check the Math for Improved Models of Liquids and Gases in Earth’s Atmosphere

Discretization is the process of converting continuous models and variables, such as wind speed, into discrete versions to make equations that are compatible with computer analysis. Energy consistent discretization ensures that the method does not have any inaccurate sources of energy that can lead to unstable and unrealistic simulations. In this research, scientists provided a discretization for equations used by global models of the Earth’s atmosphere.

Simulating sneezes and coughs to show how COVID-19 spreads

Two groups of researchers at Sandia National Laboratories have published papers on the droplets of liquid sprayed by coughs or sneezes and how far they can travel under different conditions. Both teams used Sandia’s decades of experience with advanced computer simulations studying how liquids and gases move for its nuclear stockpile stewardship mission.

Rutgers Engineers Developing Rapid Breathalyzer Test for COVID-19

New Brunswick, N.J. (April 30, 2021) – Rutgers University–New Brunswick engineering professors Edward P. DeMauro, German Drazer, Hao Lin and Mehdi Javanmard are available for interviews on their work to develop a new type of fast-acting COVID-19 sensor that detects the presence…

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.

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.

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.

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.

Masks Not Enough to Stop COVID-19’s Spread Without Distancing

Simply wearing a mask may not be enough to prevent the spread of COVID-19 without social distancing. In Physics of Fluids, researchers tested how different types of mask materials impacted the spread of droplets that carry the coronavirus when we cough or sneeze. Every material tested dramatically reduced the number of droplets that were spread. But at distances of less than 6 feet, enough droplets to potentially cause illness still made it through several of the materials.

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.

FSU researchers investigate how face shape affects COVID-19 mask performance

Face masks are helpful in preventing the spread of COVID-19, but researchers believe they can be made even more effective, something that has implications far beyond the current pandemic as masks could become a more commonly used public health intervention. Kourosh Shoele, an assistant professor in the Department of Mechanical Engineering at the FAMU-FSU College of Engineering, is part of a team that has received an $800,000 grant from the National Science Foundation to improve the efficacy of face masks as a defense against COVID-19 and other pathogens.

Face Shields No Match for Sneeze Vortex Rings

Do face shields provide enough protection to the wearers against COVID-19 if they don’t also wear a mask? No. But researchers in Japan are working to create face shields safe enough to be worn alone. In Physics of Fluids, Fujio Akagi and colleagues describe their work to gain a better understanding of what happens to the airflow around a face shield when someone nearby sneezes.

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.

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.

Estimating Risk of Airborne COVID-19 with Mask Usage, Social Distancing

In Physics of Fluids, researchers used a model to understand airborne transmission that is designed to be accessible to a wide range of people, including nonscientists. Employing concepts of fluid dynamics and factors in airborne transmission, they propose the Contagion Airborne Transmission inequality model. While not all factors may be known, it can still be used to assess relative risks. The researchers determined protection from transmission increases with physical distancing in an approximately linear proportion.

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.

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.

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.

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.

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.

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.

Bubble Dynamics Reveal How to Empty Bottles Faster

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.

Simulations Show Effects of Buoyancy on Drift in Florida Current

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.

Following the lizard lung labyrinth

Mammals inhale oxygen-rich air and they exhale depleted air, exhibiting a so-called tidal flow pattern. In contrast, bird breath travels through part of the respiratory system, but in a one-way loop throughout most of the lung. Biologists have discovered that Savannah monitor lizards have lung structures that are hybrid system of bird and mammal lungs.

Insects’ Drag-Based Flight Mechanism Could Improve Tiny Flying Robots

Thrips don’t rely on lift in order to fly. Instead, the tiny insects rely on a drag-based flight mechanism, keeping themselves afloat in airflow velocities with a large ratio of force to wing size. In a study published in this week’s Journal of Applied Physics, researchers performed the first test of the drag force on a thrip’s wing under constant airflow in a bench-top wind tunnel. Drawing from experience in microfabrication and nanomechanics, they created an experiment in which a thrip’s wing was glued to a self-sensing microcantilever.

Gallery of Fluid Motion: Capturing Liquids and Gases in Action

Tears stream down your face. A beer flows down the side of a pint glass. Fluid mechanics is central to understanding the world around us. The beauty of fluid motion was on display last week in Seattle, where more than 3,000 scientists gathered for the 72nd Annual Meeting of the American Physical Society’s Division of Fluid Dynamics. Created in 1987, the Gallery of Fluid Motion (GFM) is the premier visual record of contemporary fluid mechanics.

Schedule for the APS DFD Press Conferences with Live Webcasts from Seattle

Press conferences for the 72nd Annual Meeting of the American Physical Society Division of Fluid Dynamics in Seattle will be held Monday, Nov. 25, at the Washington State Convention Center. The conferences, which will be webcast, will focus on research into how flow control is making some MLB pitchers nearly unhittable, predicting tornado formation from the sounds that storms make and teaching fluid mechanics through dance, as well as other discoveries in fluid dynamics.

Fluid Dynamics Provides Insight into Wildfire Behavior

The Kincade Fire has been burning through Sonoma County, displacing people from their homes and leaving destruction in its wake. It is a stark reminder of the increasingly pressing need for a better understanding of how fires begin and spread. This is where Rodman Linn and his research come in. He develops and uses computational models of the coupled interaction between the wildfires and surrounding atmosphere at Los Alamos National Laboratory. In the November 2019 issue of Physics Today, Linn describes a few of the many ways that fluid dynamics controls the behavior of fires.

Analysis of Galileo’s Jupiter Entry Probe Reveals Gaps in Heat Shield Modeling

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.

Stabilizing Multilayer Flows May Improve Transportation of Heavy Oils

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.