When you shut off the valve and the fluid in the piping system is flowing fast, large cavitation bubbles may occur, which is also called water column separation. When the bubbles collapse, the implosion is violent and may cause major failures such as pipe bursting.
Why humans walk in a certain way? For example, when you walk, your gait is very different from that of a penguin, but why? We can explain this using a minimum mathematical model. Combining a multi-body dynamics model of human and simple optimization, we can predict how a person walks on level ground, a ramp, and stairs by minimizing the power output. The animation shows a predicted gait that requires the least power to walk on a ramp. This work is under collaboration with professor Dan Hu from the University of Coventry, UK.
A smoke-filled bubble was punctured from above and the spherical film quickly receded from the initial opening. While it is difficult to notice the film flapping, it is strongly suggested by the horizontal ringlets formed in the smoke by the oscillating wake. At the same time, the fingers slice through these ringlets making fine longitudinal indentations, producing a shape reminiscent of the hair of Buddha. Finally, the ringlets grow larger toward the bottom as a result of the accumulated liquid adding to the mass of the receding boundary, and thus reducing its oscillatory frequency. Nature has its own way of producing modern art in milliseconds and destroying it in the blink of an eye; the smoke acts as clay and the film as the sculptor.
Blow a soap bubble and observe it. You may study it all your life and draw one lesson after another in physics from it.