Resonance is a funny creature, as Dianna discovered when she tried to sing a rising scale through a tube. At certain notes, everyone who attempted to do it had their voices crack. Tracking down the source of the mystery means digging into what exactly resonance is and what the differences are between driving a system just before, at, and after resonance. Check out the video for the full acoustic story. (Video credit: Physics Girl)
Category: Phenomena
Plant Week: Introduction
Spring has sprung! The trees have leaves, the flowers are in bloom, and snow is (almost) a distant memory.* And here at FYFD, we’re getting ready to kick off a full week of celebrating the intersection of fluid dynamics and plants.
To get you into the mood, here’s a look at some previous plant-filled posts:
– How trees use negative pressure to hydrate
– The catapulting seeds of the hairyflower wild petunia
– Seeds that self-dig
– How desert moss drinks from the air
– The swimming of zoosporesStay tuned all next week for lots more plant physics!
*Confession: it’s still snowing at my house as I type this. But the trees do have leaves and there are flowers blooming. Poor things. – Nicole
(Original image: Pixabay)
Tornado from a Drone
One of the challenges in studying tornadoes is being in the right place at the right time. In that regard, storm chaser Brandon Clement hit the jackpot earlier this week when he captured this footage of a tornado near Sulphur, Oklahoma from his drone. He was able to follow the twister for several minutes until it apparently dissipated.
Scientists are still uncertain exactly how tornadoes form, but they’ve learned to recognize the key ingredients. A strong variation of wind speed with altitude can create a horizontally-oriented vortex, which a localized updraft of warm, moist air can lift and rotate to vertical, birthing a tornado. These storms most commonly occur in the central U.S. and Canada during springtime, and researchers are actively pursing new ways to predict and track tornadoes, including microphone arrays capable of locating them before they fully form. (Image and video credit: B. Clement; via Earther)
Fluid at Work
For many engineering students, their first experience with flow visualization comes in undergraduate labs, where dye introduced into a flume demonstrates basic flow features around airfoils, cylinders, and spheres. This short video by undergraduate Nick Di Guigno and partners quietly illustrates that experience, from the introduction to the equipment to loading the dye and watching the flow develop under the commentary of one’s professor. For those of you who have done this, I suspect it may ignite a bit of nostalgia. For those who haven’t, I think it captures some of the magical feeling of stepping into the lab the first time, even when you’re just recreating a phenomenon others have seen a thousand times before. (Image and video credit: N. Di Guigno et al.)
As Ice Flows
The movement of glaciers is driven by gravity. The immense weight of the ice causes it to both slide downhill and deform – or creep. As glacier melting speeds up, scientists have debated how glacier flow will respond: will the loss of ice cause the glaciers to move more slowly since they have less mass, or will the increase in meltwater help lubricate the underside of glaciers and make them flow even faster?
By analyzing satellite image data of Asian glaciers collected between 1985 and 2017, researchers are finally answering that question. Their research shows that these glaciers are slowing down as they lose mass and speeding up as they gain mass. Nearly all – 94% – of the flow changes they observed can be accounted for solely from ice thickness and slope. This is valuable information as scientists continue to monitor and predict the changes we must expect as the world continues to warm. (Image credit: J. Stevens; research credit: A. Dehecq et al.; via NASA Earth Observatory)
Fiery Backdraft
Combustion is ultimately a chemical reaction, and like any chemical reaction, it requires the right balance of ingredients. The only way to completely exhaust the reaction is to have the perfect amount of fuel (i.e. stuff to burn) and oxidizer (i.e. oxygen). When those ratios don’t match, the reaction can slow down or even appear to end, but that doesn’t mean a fire’s gone out.
Firefighters face one of the dangerous consequences of this situation in the form of backdrafts. When a fire has been burning in a sealed container and exhausted its oxygen supply, it can get extremely hot even if the flames seem to have died down. When oxygen is added back by opening a door or window, the fire can react explosively, as the Slow Mo Guys demonstrate above. The good news is that backdrafts are relatively rare and there are steps you can take to avoid them. (Image and video credit: The Slow Mo Guys)
Weirs
Hydraulic engineers use weirs, like the one shown below, to control upstream flow conditions. Weirs can come in many forms, but they essentially look like a small dam with water flowing over the top. They’re used to control both the flow rate and the upstream water level. As Grady from Practical Engineering explains, there are a few characteristics hydraulic engineers can vary to help adapt to changing water conditions. Check out the full video above to learn more about these important engineering features you’ve likely seen but never learned about. (Video and image credit: Practical Engineering)
Sniffing
In many ways, smell is a strange sense. The very act of sniffing – pulling air and odor molecules into our noses – changes what remains behind in a way that sight and sound do not. Humans aren’t great sniffers, but dogs have an exquisite sense of smell, and in this video, Deep Look describes how and why that is. From special scent organs to their experimental protocols, dogs are well-adapted to reading the world by smell. (Image and video credit: Deep Look)
Slow Mo Geyser
Geysers are one of the most surreal wonders of our planet – pools of turquoise that periodically erupt into towers of water and steam. But what we see from the surface is only a small part of the story. Geysers require two main ingredients: an intense geothermal heat source and the right plumbing. Below ground, that plumping needs both a reservoir for water to gather and narrow constrictions that encourage the build-up of pressure.
A cycle begins with water filling the reservoir; this can be both geothermally heated water and groundwater seeping in. As the geyser fills, the pressure at the bottom increases. Eventually, the water becomes superheated, meaning that it’s hotter than its boiling point at standard atmospheric pressure. That’s when the steam bubbles you see above rise to the surface. When they break through, it causes a sudden drop in the reservoir pressure. The superheated water there flashes into steam, causing the geyser to erupt. Check out the full video below for some awesome high-speed video of those eruptions, and, if you’re curious what the inside of an active geyser looks like check out Eric King’s video. (Image and video credit: The Slow Mo Guys; submitted by @eclecticca)
Seeing Shock Waves
This week NASA released the first-ever image of shock waves interacting between two supersonic aircraft. It’s a stunning effort, requiring a cutting-edge version of a century-old photographic technique and perfect coordination between three airplanes – the two supersonic Air Force T-38s and the NASA B-200 King Air that captured the image. The T-38s are flying in formation, roughly 30 ft apart, and the interaction of their shock waves is distinctly visible. The otherwise straight lines curve sharply near their intersections.
Fully capturing this kind of behavior in ground-based tests or in computer simulation is incredibly difficult, and engineers will no doubt be studying and comparing every one of these images with those smaller-scale counterparts. NASA developed this system as part of their ongoing project for commercial supersonic technologies. (Image credit: NASA Armstrong; submitted by multiple readers)
