#pinch-off

[fuckyeahfluiddynamics]

Drops of Fiber Suspensions

To 3D print with fiber-infused liquids, we need to understand how these drops form, break-up, and splash. That's the subject of this research poster, which shows drops of a fiber suspension forming and pinching off along the top of the image. (Image credit: S. Rajesh and A. Sauret; via GoSM) Read the full article

[fuckyeahfluiddynamics]

Draining a Bottle

Turn a bottle upside-down to empty it, and you'll hear a loud glug-glug-glug as the liquid in the bottle empties and air rushes in. In this video, researchers aim a high-speed camera at the very first bubble that forms during the process. (Image and video credit: H. Mayer et al.)

[fuckyeahfluiddynamics]

There is a surprising variety of forms in the pinch-off of a liquid drop. This short video shows three examples, and you'll probably find yourself replaying it a few times to catch the details of each. On the left, a drop of water pinches off in air. As the neck between the nozzle and the drop elongates, the drop end of the neck thins to a point around which the drop's surface dimples. This is called overturning. When the drop snaps off, the neck disconnects and rebounds into a smaller satellite droplet. The middle video shows a drop of glycerol, which is about 1000 times more viscous than water. This droplet stretches to hang by a thin neck that remains nearly symmetric on the nozzle end and the drop end. There is no satellite drop when it breaks. The rightmost video shows a polymer-infused viscoelastic liquid pinching off. This liquid forms a very long, thin thread with a fat satellite drop still attached. When gravity eventually becomes too great a force for the stresses generated by the polymers in the liquid, the drops break off. (Video credit: M. Roche)

[fuckyeahfluiddynamics]

This high-speed video reveals a fascinating bit of kitchen sink physics.  When a water droplet pinches off from the nozzle, the thin filament of fluid that connected the droplet to the water on the nozzle often breaks off as well.  Surface tension snaps the filament together into a sphere, causing wild oscillations and even ejection of microjets in the tiny satellite droplet. (Video from S. Thoroddsen et al. 2008's Annual Review)

[fuckyeahfluiddynamics]

A decane liquid lens floating on water (think drops of fat in chicken soup) displays different breakup and pinch-off than seen in three-dimensional droplet breakup. The pinch-off process in two dimensions relies on line tension rather than surface tension, and the quasi-2D liquid lens system is somewhere between these. The video above is a magnification of the filament connecting one liquid lens as it is broken into two smaller liquid lenses (the dark areas on the left and right of the screen). # (via scienceisbeauty)