In this video, researchers investigate swirling fluids by studying the shapes of the free surface between air and the liquid. As parameters like the diameter of the glass, initial (unperturbed) height of the liquid, and angular velocity of the rotation change, the surface of the liquid displays different modal behaviors, seen in the photos on the lower left of the video. By non-dimensionalizing the physical parameters of the system (students: think Buckingham pi theorem), they are able to replicate the shape of the free surface by matching a Froude number and dimensionless depth and offset. Such similitude between fluids under different conditions is key to understanding the underlying physics. (Video credit: M. Reclari et al; submitted by co-author M. Farhat)
Tag: slosh
Sloshing to Dampen
In this high-speed video, two flexible spheres are dropped from the same height. The one on the left is filled with air, the other is partially filled with a liquid. Although both spheres rebound to nearly the same height after the first bounce, their behavior differs drastically after that. The sloshing of the liquid inside the sphere acts as a damper, absorbing energy that would otherwise cause the ball to continue bouncing. The effects of contained liquids sloshing are important for understanding the dynamics of tankers, fuel on spacecrafts, and even how to walk without spilling your coffee.