#water impact

[fuckyeahfluiddynamics]

Crowned Jets

If you fill a test tube with water and drop it, the impact causes a pressure wave that travels up from the bottom and creates a focused jet (left). (Image credit: H. Watanabe et al.)

[fuckyeahfluiddynamics]

Curved Rocks Hit Harder

Intuition suggests that a flat rock will hit the water with greater force than a spherical one, and experiments uphold that. But a flat rock, interestingly, doesn't produce the greatest impact force.  (Image credit: J. Wixom; research credit: J. Belden et al.; via APS Physics) Read the full article

[fuckyeahfluiddynamics]

Shaking on Impact

When objects impact water with enough speed, they create a smooth-walled, air-filled cavity around and behind them. Here, the impacting object is one with some give, like a spring.  (Image credit: J. Antolik et al.) Read the full article

[fuckyeahfluiddynamics]

Diving From Above

Blue-footed boobies, like many other seabirds, climb to a particular altitude before folding their wings and diving head-first into the water. This acrobatic feat balances the bird's force of impact and the depth it can reach to ensnare fish swimming there. (Image credit: H. Spiers, Bird POTY; via Colossal)

[fuckyeahfluiddynamics]

Plunge a disk into water and you'll get a dome-like splash that closes back on itself. But what happens when that disk has a patterned surface? (Image, research, and video credit: H. Kim et al.)

[fuckyeahfluiddynamics]

How spheres impact water has been studied for more than a century. The typical impact for a rigid sphere creates a cavity like the one on the upper left - relatively narrow and prone to pinching off at its skinny waist. If the sphere is elastic --squishy -- instead, the cavity ends up looking much different. This is shown in the upper right image, taken with an elastic ball and otherwise identical conditions to the upper left image. The elastic ball deforms; it flattens as it hits the surface, creating a wider cavity. If you watch the animations in the bottom row, you can see the sphere oscillating after impact. Those changes in shape form a second cavity inside the first one. It’s this smaller second cavity that pinches off and sends a liquid jet back up to the collapsing splash curtain. 

From the top image, we can also see that the elastic sphere slows down more quickly after impact. This makes sense because part of its kinetic energy at impact has gone into the sphere’s shape changes and their interaction with the surrounding water. 

If you’d like to see more splashy stuff, be sure to check out my webcast with a couple of this paper’s authors. (Image credits: top row - C. Mabey; bottom row - R. Hurd et al., source; research credit: R. Hurd et al.)

[darkwindjr]

Tengai Shinsei Minazuchi! 

 Water Type Meteor 

Anime: Tsugumomo

[fuckyeahfluiddynamics]

A sphere falling into water is a classic problem in fluid dynamics, but scientists are becoming increasingly interested in what happens when they introduce new dimensions to the problem. Here researchers float an extremely thin elastic sheet atop water and study how it wrinkles when a steel sphere impacts it. Despite its elasticity, the sheet does not stretch when the ball hits. Instead it compresses and forms wrinkles. Some of those wrinkles deepen into folds, but the wrinkle pattern that forms right at impact determines the way the film will bunch up. If the ball is heavy enough, it will drag the sheet entirely underwater; if not, the sheet will catch the ball and continue floating. Scientists are interested in these interactions between liquids and thin solids because sheets could be used to encapsulate liquids for applications like targeted drug delivery. (Image credit: M. Inizan et al., source)