I confess I’d never heard the term derecho before moving to Colorado, but I’ve experienced a few of these wind storms now. They’re intense! Last December’s derecho formed when a high-pressure system in the western United States met a strong low-pressure system over the northern plains. In fluids, flow moves preferentially from areas of high pressure to those with low pressure, and that’s no different when it comes to weather. The strong pressure gradient drove high winds from the Rocky Mountains to Minnesota. The animation above shows the strongest winds in in yellow-white but even the “weaker” pink areas saw winds comparable to a fast-moving car in speed. The visualization is constructed from data reported by ships, buoys, aircraft, satellites, and other sources, all processed through a NASA weather algorithm. (Image credit: J. Stevens/NASA; via NASA Earth Observatory)
Tag: physics
Inside a Coronavirus Aerosol
This is a glimpse inside a tiny aerosol droplet with a single SARS-CoV-2 coronavirus inside it. The numerical simulation required a team of 50 scientists, 1.3 billion atoms, and the second most powerful supercomputer in the world. By simulating every atom, the researchers hope to observe what happens to a coronavirus in these micron-sized, long-lasting droplets. Does the virus survive? How do variants fare?
Their simulation shows that the positive charge of the coronavirus’s spike proteins helps attract mucins that shield the virus and protect it from the droplet interface where evaporation could destroy it. Variants like Delta and Omicron have even more positive charge to their spike proteins, giving themselves a better cloak of mucins and potentially making them all the more infectious. Definitely check out the full New York Times write-up for more spectacular visualizations from the work. (Image and research credit: R. Amaro et al.; via NYTimes; submitted by Kam-Yung Soh)
“Shadows in the Sky”
This moody music video features storm chasing footage from photographer Mike Olbinski. As always, his captures are stunningly majestic. Watch closely and you’ll see everything from bulbous mammatus clouds to powerful microbursts, from horizon-obscuring haboobs to sky-splitting lightning. And if this video isn’t enough, there’s plenty more to enjoy. (Video and image credit: M. Olbinski)
Swirls in the Wake
Rocky islands make excellent atmospheric swirls, as seen here around Guadalupe Island. Winds blowing in from the ocean get forced up and around the island’s topography, resulting in vortices that shed alternately from either side of the island. The pattern they form is known as a von Karman vortex street and is easily seen in satellite imagery, thanks to the swirls that can persist for tens of kilometers downstream. Personally, I never get tired of this one! (Image credit: NASA/GSFC/JPL; video credit: NOAA/CIRA; via Dakota Smith; submitted by @SellaTheChemist)
Opera Singer Air Flow
What does the air flow from a trained opera singer look like? That’s the question behind this study, which combines music and fluid dynamics. Using an infrared camera tracking carbon dioxide (CO2) exhalations from a singer during a performance allowed researchers to identify several important flow features. When breathing, air flows out the singer’s nose in a tight, downward jet with an initial velocity around 1 m/s.
While singing, air leaves the mouth at a much lower velocity, especially during vowels where the mouth is open. With less momentum behind these exhalations, they can drift upward on the buoyant warmth of the singer’s breath. During consonants — especially plosives like t, k, p, b, d, and g — a rapid burst of air leaves the mouth, traveling at nearly 10 m/s. From the perspective of COVID-19 safety, it’s these plosive jets that are likely to spread contaminated droplets. (Image and video credit: MET Orchestra; research credit: P. Bourrianne et al.; via Improbable Research; submitted by Kam-Yung Soh)
The Hot Chocolate Effect
Stir hot chocolate powder into milk or water, and you can recreate this bizarre acoustic phenomenon. Once the powder is mixed in, tapping the side of the cup creates a low pitch that steadily rises as you continue tapping. This is known as the hot chocolate, or allossonic, effect. When you stir, it creates tiny bubbles in the fluid, which changes the effective speed of sound. As the bubbles pop, the speed of sound goes up and the pitch of your tapping gets higher! Stirring the cup up again (even without adding more powder) should lower the pitch once more. (Video credit: C. Kalelkar)
The Best of FYFD 2021
A year ago I observed what a strange year 2020 had been, and in many ways, I could say the same of 2021. Before the pandemic, I spent quite a lot of time traveling. In 2021, the only nights I slept outside my own bed came on a long weekend up to the mountains with my family. But 2021 also saw a bit of a return to normalcy – I was giving keynote addresses and workshops again, albeit virtually. What will 2022 hold? Who knows?!
As per tradition, here are the top FYFD posts of 2021:
- A superior mirage leaves a ship floating in mid-air
- Drone videos of sheep herding are mesmerizing
- Permeable pavement allows water to drain
- The slow and dreamy fluid landscape of “Le Temps et l’Espace”
- What do you do when you’re an insect researcher with a high-speed camera?
- Satellite images… or paint?
- The intricate lacework of the Venus’s flower basket sea sponge
- Building a Bluetooth speaker with ferrofluid music visualization
- Finding the acoustics of Stonehenge
- Making butter by traditional French methods
It’s an eclectic mix of topics this year: bizarre phenomena, stunning art, archaeological exploration, and a touch of biophysics!
If you enjoy FYFD, please remember that it’s primarily reader-supported. You can help support the site by becoming a patron, making a one-time donation, buying some merch, or simply by sharing on social media. And if you find yourself struggling to remember to check the website, remember you can get FYFD in your inbox every two weeks with our newsletter. Happy New Year!
(Image credits: mirage – D. Morris, sheep – L. Patel, pavement – Practical Engineering, Le Temps – T. Blanchard, insects – Ant Lab, Satellike – R. De Giuli, sea sponge – G. Falcucci et al., speaker – DAKD Jung, Stonehenge – T. Cox et al., butter – Art Insider)
“Fire and Fusion”
Photographer Andrew McCarthy constructed this spectacular 300-megapixel image of our sun by compositing thousands of individual images. Sunspots, coronal mass ejections, and feathery convective swirls abound. Check out his site for prints of this and other celestial images! (Image credit: A. McCarthy; via Colossal)
Tougher Hydrogels
Hydrogels are soft, stretchy solids made from polymer chains immersed in water. Engineers hope these materials will be good candidates for medical implants, but to reach that goal, hydrogels need to be durable enough to withstand repeated stretching and contortion without tearing. One team has built a better hydrogel by encouraging entanglement within the gel’s polymer network.
The polymers inside a hydrogel form their network with two main components: physical entanglements between polymer chains and chemical cross-links. If you imagine the polymers as a tangle of yarn, the cross-links would be spots where pieces of yarn are knotted together and the entanglements are spots where strands wrap and cross without knotting. If you pull on the network, cross-links (knots) will allow very little stretching, whereas the looser entanglements can stretch and deform without tearing. In a hydrogel with lots of entangled polymers but very few cross-links, the material is strong and stretchy without becoming brittle or easily torn. (Video credit: Science; research credit: J. Kim et al.)
Cavitation-Induced Microjets
In cavitation, tiny bubbles of vapor form and collapse in a liquid, often sending shock waves ricocheting. In most occurrences beyond the lab, cavitation bubbles aren’t a solo act; many bubbles can form and interact. This video takes a look at some of the effects of those interactions. When close together, two cavitation bubbles can act to focus the flow during collapse, generating a microjet strong enough to penetrate into nearby surfaces. Researchers hope this technique may one day be used for needle-free injections. (Image, video, and submission credit: A. Mishra et al.)
