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Search results for: “waves”

  • Waves on Other Planets

    Waves on Other Planets

    On Earth, most waves form when wind blows across the water. The shear and added energy from the wind ripples the surface, eventually building up waves (through the Kelvin-Helmholtz instability). The same process should happen anywhere else where wind and open liquid surfaces meet–even on other planets. To explore this, researchers built a new model, PlanetWaves, that predicts the waves based on a planet’s gravity, atmospheric conditions, and the density, viscosity, and surface tension of its surface liquid.

    After validating the model with conditions on Earth, the team explored wave conditions for Titan, ancient Mars, and several exoplanets. They found that Titan’s lighter gravity and liquid ethane (which is less dense than water) combined to make waves on Titan much taller than those generated at the same wind speed on Earth (top image). You can watch them in action in the video below. Standing in a light breeze on Titan, you’d watch giant 3-meter waves rolling in.

    The team also found that waves on Mars would have gotten shorter as Mars lost its atmosphere and the air pressure dropped. Over time, the same wind speed would have elicited smaller and smaller waves. Wave action has a big effect on a landscape’s erosion, so understanding how waves look on other planets will help us parse their geography. (Video, image, and research credit: U. Schneck et al.; via MIT News; submitted by Joseph S.)

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    “Frozen Waves”

    Photographer Jan Erik Waider is a master of capturing incredible landscape imagery. In these videos, he uses a drone to film waves in the Baltic Sea gently undulating polygonal slabs of ice on the ocean surface. The interplay of light, color, and motion looks almost surreal, but nature is better than we credit at making imagery too good to look away from. (Video and image credit: J. Waider/NorthLandscapes; via Colossal)

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  • Frozen Waves

  • Watching Waves on the Nanoscale

    Watching Waves on the Nanoscale

    It’s tough to simulate nonlinear wave dynamics, so scientists often test theories in wave flumes, where they can create more controlled waves than what we see in the wild. But conventional wave flumes are big–meters-long, complicated equipment–and can only test a small range of conditions. To reach more extreme nonlinear dynamics, researchers have turned to a chip-based approach. These 100-micron-long wave flumes carry a film of superfluid helium less than 7 nanometers thick. But despite that tiny size, the system can reach levels of nonlinearity five orders of magnitude greater than their full-sized counterparts. (Image and research credit: M. Reeves et al.; via Physics Today)

    Labeled diagram of a 100-micron-long wave flume.
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  • Seeing Sound Waves

  • Radiant Waves

    Radiant Waves

    Photographer Kevin Krautgartner captures the powerful waves of Western Australia from above. His latest series, Waves | Ocean Forces, features luminous turquoise waves, crystalline foam, and brilliant beaches. I could delight in staring at them for hours. Fortunately, he sells prints on his website! (Image credit: K. Krautgartner; via Colossal)

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  • Toward Predicting Rogue Waves

    Toward Predicting Rogue Waves

    Rogue waves were once the stuff of nautical legend. Tales of giant lone waves were considered sailors’ tall tales, until an oil rig in the North Sea was hit by a 25.6-meter wave on 1 January 1995. The wave was more than twice the height of any others around it and much steeper, too. Since then, scientists have been working to understand how and why these rogue waves form.

    A recent study, like many others, attributes rogue waves to the subtle nonlinearities of ocean waves, which don’t match a smooth sinusoid even though they are sometimes modeled that way. When it comes to rogue waves, the sharpness of a wave’s peak and flattening of its trough affect whether waves come together into a lone giant.

    The study is based on 18 years worth of wave data collected at an offshore platform in the North Sea. With such an extensive data set, researchers were able to find patterns in the waves that precede the arrival of a rogue wave. That’s an important step toward being able to predict a rogue wave, which would help protect platforms, ships, and personnel. (Image credit: C. Wou; research credit: S. Knobler et al.; via SciAm)

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  • Radiant Waves

  • Waves Over Sand Ripples

    Waves Over Sand Ripples

    Look beneath the waves on a beach or in a bay, and you’ll find ripples in the sand. Passing waves shape these sandforms and can even build them to heights that require dredging to keep waterways passable to large ships. To better understand how the sand interacts with the flow, researchers build computer models that couple the flow of the water with the behavior of individual sand grains. One recent study found that sand grains experienced the most shear stress as the flow first accelerates and then again when a vortex forms near the crest of the ripple. (Image credit: D. Hall; research credit: S. DeVoe et al.; via Eos)

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  • Roll Waves in Debris Flows

    Roll Waves in Debris Flows

    When a fluid flows downslope, small disturbances in the underlying surface can trigger roll waves, seen above. Rather than moving downstream at the normal wave speed, roll waves surge forward — much like a shock wave — and gobble up every wave in their way.

    Such roll waves are fairly innocuous when flowing down a drainage ditch but far more problematic in the muddy debris flows of a landslide. Debris flows are harder to predict, too, thanks to their combined ingredients of water, small grains, and large debris.

    A new numerical model has shed some light on such debris flows, after showing good agreement with a documented landslide in Switzerland. The model suggests that roll waves get triggered in muddy flows at a higher flow speed than in a dry granular flow but a lower flow speed than is needed in pure water.

    For a great overview of roll waves, complete with videos, check out this post by Mirjam Glessner. (Image credit: M. Malaska; research credit: X. Meng et al.; see also M. Glessmer; via APS)

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