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.

Read more

In a Pandemic, Migration Away from Dense Cities More Effective than Closing Borders

During the COVID-19 pandemic, closing national borders and borders between states and regions has been prevalent. But does it help? In a paper in Chaos, researchers decided to put this hypothesis to the test and discover if confinement and travels bans are really effective ways to limit the spread of a pandemic disease. Specifically, they focused on the movement of people from larger cities to smaller ones and tested the results of this one-way migration.

Read more

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.

Read more

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.

Read more

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.

Read more

Random Effects Key to Containing Epidemics

To control an epidemic, authorities will often impose varying degrees of lockdown. In the journal Chaos, scientists have discovered, using mathematics and computer simulations, why dividing a large population into multiple subpopulations that do not intermix can help contain outbreaks without imposing contact restrictions within those local communities. When infection numbers are high, random effects can be ignored. But subdividing a population can create communities so small that the random effects matter.

Read more

Interactions Within Larger Social Groups Can Cause Tipping Points in Contagion Flow

Contagion processes, such as opinion formation or disease spread, can reach a tipping point, where the contagion either rapidly spreads or dies out. When modeling these processes, it is difficult to capture this complex transition. In the journal Chaos, researchers studied the parameters of these transitions by including three-person group interactions in a contagion model called the susceptible-infected-susceptible model. In this model, an infected person who recovers from an infection can be reinfected.

Read more

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.

Read more

COVID-19: Second Wave for Some; Others Remain in First Wave

As the COVID-19 pandemic continues, some locations have experienced decreasing numbers of cases followed by an increase. In the journal Chaos, mathematicians report a method to analyze these numbers for evidence of a first or second wave. The authors studied data from all 50 U.S. states plus D.C. for the seven-month period from Jan. 21 to July 31. They found 31 states and D.C. were experiencing a second wave as of the end of July.

Read more

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.

Read more

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.

Read more

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.

Read more