Photographer Mike Olbinski returns with another incredible storm-chasing timelapse video, this time all in black-and-white. To me, that choice helps “Pulse” emphasize the ominous majesty of these supercells and tornadoes by highlighting the textures that make up the clouds. Watching clouds in timelapse, they seem to materialize from nowhere as moisture drawn up from the land cools and condenses. Sped up, suddenly the convective rotation and the roiling turbulence inside clouds is perfectly clear. I especially love the sequence beginning at 2:25, where a distant black line slowly transforms into an incredible landscape marked with successive waves of rolling, turbulent clouds. Watch this one on a large screen at a high resolution, if you can. You won’t regret it! (Video credit: M. Olbinski)
Search results for: “waves”
Crowns On Impact
Dropping a partially-filled test tube of water against a table makes the meniscus at the air-water interface invert into a jet of liquid. In some cases, the impact is strong enough to generate splashing crowns of water around the base of the jet. These crowns come in two forms – one with many splashes layered upon one another and the other with only a few splashes and a faster jet.
The many-layered splash crowns come from the pressure wave that reflects back and forth from the bottom of the tube to the surface and back. This pressure wave moves at the speed of sound and vibrates the water surface, creating the many splashes. The same reflected pressure wave occurs in the second type of splash crown, but it gets disrupted by cavitation bubbles that form in the water (visible in the lower left image). Instead the splash crowns form from the shock waves generated when the cavitation bubbles collapse. (Image credits: A. Kiyama et al.)
Creating Moana’s Ocean
Hopefully by now you’ve had an opportunity to see Disney’s film Moana. Fluid dynamics play a central role in the movie, and Disney’s animators faced the challenge of hundreds of shots requiring special effects to animate water, lava, waves, and wind. Science Friday has a great segment interviewing a couple of Moana’s animators, in which they discuss the process of turning the ocean itself into a character.
Because the physics of fluids is so complex, scientists and animators differ in the way they approach simulations. Scientists usually try to capture a full physical representation of a flow, simulating every detail to the smallest scale and time step. Animators, on the other hand, are interested in capturing a realistic feel for a flow. For an animator, the simulation should be exactly as complex as necessary to make the water move in a way a person believes it should. With Moana, animators had the extra challenge of melding the ocean character’s actions with appropriate water physics–think bubbles, drops, and splashes. The results are impressive and exceptionally fun. (Image credits: Disney/Science Friday; via Jesse C.)
Paint Spilling Physics
There is a remarkable amount of physics contained in art. In this video, scientists from The Splash Lab explore some of the physics involved in pouring paint atop a rectangular post. The spreading paint transforms its shape repeatedly, and, at the corners of the post, it preserves a tiny history of all the colors poured. Paint sliding down the sides shifts from a thin sheet to a thicker jet that deposits color in waves. For tall posts, the distance the paint falls is long enough for instabilities to set in, producing a paint puddle that’s riddled with curves and waves between each color of paint. It’s a lovely reminder of the complexity inherent even within a simple action. (Video credit: R. Hurd et al.)
The Sound of a Balloon Popping
The pop of an overfilled balloon is enough to make anyone jump, but you’ve probably never seen it like this. The photo above uses an optical technique known as schlieren photography that reveals changes in density of a transparent gas like air. The shredded rubber of the balloon is still visible in black, and around the balloon there’s an expanding spherical shock wave. It’s the sudden release of energy when the balloon ruptures and the gas inside begins to expand that causes the shock wave. Notice, though, that the gas from the balloon is still clearly visible and balloon-shaped–much like a water balloon that’s just popped. From that clear delineation, I would say that this balloon was filled with a different gas than air–otherwise the density shouldn’t be different enough to make the interior gas distinguishable. (Image credit: G. Settles)
Inside Cavitation
Cavitation bubbles live a short and violent life. It begins when a low-pressure void forms in a fluid–for example, when a liquid is accelerated so that the pressure drops below the vapor pressure, which can happen at the tips of a boat’s propeller or when striking a bottle. The bubbles that form expand and then collapse rapidly as the higher pressure of the liquid surrounding them squeezes them down. That collapse of the bubble is so violent that it heats the fluid inside the bubble to temperatures hotter than the surface of the sun, generating both a flash of light and a shock wave. It’s these shock waves that cause much of the damage associated with cavitation in engineering, but they can be used for good as well. Shock wave lithotripsy uses cavitation-induced shock waves to break down kidney stones. (Image credit: O. Supponen et al., source)
Swirling Pollen
This photo captures the chaotic mixing present in a simple puddle. Pine pollen strewn across the puddle’s surface acts as tracer particles, revealing some of the motion of the underlying water. As wind blows across the puddle, it moves the water through the formation of ripples and by shearing the surface. That deformation on the top of the puddle will cause further motion beneath the surface. With time and changing wind direction, the resulting pattern of flow can be very complex! (Photo credit: K. Jensen, original)
Pelican Surfing
Birds can be incredibly clever about using their surroundings to enhance their flight. Pelicans will even surf! As a line of waves rolls toward shore, it pushes a small updraft ahead of it – just like a line of mountains creates a windy updraft. Pelicans save energy by riding the updraft just like a surfer would ride the swell. Once the wave breaks, the air and water become turbulent and less useful, so the pelican cuts away to find his next ride. (Image and submission credit: N. Yarvin, source)
Inside a Supernova
During a supernova, shock waves moving outward push denser material into less dense plasma and gas. This causes what is known as a Richtmyer–Meshkov instability, where the interface between the two fluids first becomes wavy and then develops finger-like intrusions. Those too break down, as seen in the simulation above, causing large-scale mixing between the different fluids.
Here on Earth this instability shows up in the process of inertial confinement fusion. In that case, the outer shell material is denser than the fuel core and the instability is triggered during the implosion process. As the fusion material is suddenly compressed, waviness and mixing occurs along the interface between the shell and the fuel. That’s undesirable because it reduces the efficiency of the fusion reaction. (Image credit: E. Evangelista et al.)
Ionic Sound
So, as we learned previously, sound can actually travel through space. But the recordings our spacecraft send us from other planets or from the edge of the Solar System aren’t really that kind of sound. Acoustic waves require a medium; they travel when particles bump into one another, which, given the sparseness of space, means that only very low frequency sounds can travel. But space has a lot of ions and plasmas – charged particles like electrons and protons – and those particles can interact without physically contacting one another. Instead their motion causes a changing magnetic field that affects nearby particles, which in turn affect more particles (and so on). This transmits what’s called ionic sound. Check out the video above to hear some awesome examples of the ionic sounds of our solar system! (Video credit: The Point Studios)