In Physics of Fluids, researchers simulate an atomic bomb explosion from a typical intercontinental ballistic missile and the resulting blast wave to see how it would affect people sheltering indoors.
In Physics of Fluids, researchers design and analyze droplet experiments that were done on the International Space Station. The researchers sent four different surfaces with various roughness properties to the station, where they were mounted to a lab table. Cameras recorded the droplets as they spread and merged. The experimental results confirmed and expanded the parameter space of the Davis-Hocking model, a simple way to simulate droplets.
In Physics of Fluids, researchers explore the lift production mechanism of flying snakes, which undulate side-to-side as they move from the tops of trees to the ground to escape predators or to move around quickly and efficiently. The investigators developed a computational model derived from data obtained through high-speed video of the snakes and considered several features, such as the angle of attack that the snake forms with the oncoming airflow and the frequency of its undulations, to determine which were important in producing glide.
In Physics of Fluids, researchers have been studying the dynamics of how crescent-shaped sand dunes are formed. Known as barchans, these formations are commonly found in various sizes and circumstances, on Earth and on Mars. Using a computational fluid dynamics approach, the team carried out simulations by applying the equations of motion to each grain in a pile being deformed by a fluid flow, showing the ranges of values for the proper computation of barchan dunes down to the grain scale.
Superheated steam dishwashers could provide a more effective, environmentally friendly solution than conventional dishwashers. In Physics of Fluids, researchers simulated such a dishwasher, finding that it killed 99% of bacteria on a plate in just 25 seconds. The model of an idealized dishwasher looks like a box with solid sides, a top opening, and a nozzle at the bottom. A plate covered with heat-resistant bacteria is placed directly above the nozzle. Once the plate reaches a certain threshold temperature, the microorganisms are deemed inactivated.
A common method of administering drugs is orally, by swallowing a pill or capsule. But oral administration is the most complex way for the human body to absorb an active pharmaceutical ingredient, because the bioavailability of the drug in the gastrointestinal tract depends on the medication’s ingredients and the stomach’s dynamic physiological environment. In Physics of Fluids, researchers from employ a biomimetic in-silico simulator based on the realistic anatomy and morphology of the stomach – a “StomachSim” – to investigate and quantify the effect of body posture and stomach motility on drug bioavailability.
There is much more that comes out of the pop of an opening champagne bottle than meets the senses. In Physics of Fluids, computational fluid dynamics simulations revealed the formation, evolution, and dissipation of shock wave patterns as the carbon dioxide mixture shoots through the bottleneck in the first millisecond after cork popping. The findings could provide insight into the complex and transient behavior of supersonic flow in applications ranging from rocket launchers, ballistic missiles, and wind turbines to electronics manufacturing and underwater vehicles.
In Physics of Fluids, researchers create a model to connect what biologists have learned about COVID-19 superspreading with how such events have occurred in the real world. They use occupancy data to test several features ranging from viral loads to the occupancy and ventilation of social contact settings. They found that 80% of infections occurring at superspreading events arose from only 4% of those who were carrying the virus into the event. The top feature driving the wide variability in superspreading events was the number of viral particles found in index cases.
In Physics of Fluids, researchers present clinicians with information about the risk factors for atherosclerotic plaque formation from a mechanical point of view. The scientists are exploring whether it is possible to screen and intervene early for people at risk for atherosclerotic disease from the perspective of hemodynamics, using color Doppler ultrasound, coronary computed tomography angiography, and other screenings. The researchers used a multipoint, noncontact laser flow measurement method called microparticle image velocimetry.
In Physics of Fluids, scientists describe their work on an at-home study of rheology, which is used to study the way non-Newtonian liquids or semisolid substances flow. The projects assigned to students had two parts: gathering qualitative visual evidence of rheological properties and taking quantitative measurements. The students checked for four behaviors – shear thinning viscosity, viscoelasticity, shear normal stress difference, and extensional viscosity – and even without access to laboratory rheometers, they developed creative and unique ways to carry out their measurements.
In Physics of Fluids, researchers use principal component analysis along with fluid dynamics simulation models to show the crucial importance of proper fit for all types of masks and how face shape influences the most ideal fit. They modeled a moderate cough jet from a mouth of an adult male wearing a cloth mask over the nose and mouth with elastic bands wrapped around the ears and calculated the maximum volume flow rates through the front of mask and peripheral gaps at different material porosity levels.
As we approach two full years of the COVID-19 pandemic, we now know it spreads primarily through airborne transmission. The virus rides inside tiny microscopic droplets or aerosol ejected from our mouths when we speak, shout, sing, cough, or sneeze. It then floats within the air, where it can be inhaled by and transmitted. This inspired researchers in India to explore how we can better understand and engineer airflow to mitigate the transmission of COVID-19.
Meteorologists and emergency workers continue to contest the popular thinking that waiting out a tornado under an overpass is safe. According to the National Weather Service, doing so could actually increase the risk of death, in part because the wind from a tornado is thought to accelerate as it flows under the overpass, in what’s known as the wind tunnel effect.
In Physics of Fluids, by AIP Publishing, researchers from the Indian Institute of Science studied the fate of a large-sized surrogate cough droplets at different velocities, corresponding from mild to severe, while using various locally procured fabrics as masks.
In Physics of Fluids, by AIP Publishing, scientists from the Indian Institute of Science and the Narayana Nethralaya Foundation explain how tears ejected from the eye during a procedure that tests for glaucoma can theoretically transmit disease.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.