Question
Surface tension drives some forms of this phenomenon that initiate at the interface of two fluids. For 10 points each:
[10m] Name this phenomenon in which perturbative solutions have negative imaginary frequencies, causing the system to be forced out of equilibrium as the perturbations grow exponentially.
ANSWER: fluid instability [or fluid instabilities; accept unstable or not stable]
[10h] Surface tension drives this instability that is sometimes named for a Belgian physicist who observed it by exciting a liquid thread using a cello. Inkjet printers induce this instability in the inkjet stream to create a regular stream of small droplets.
ANSWER: Plateau–Rayleigh instability [or Rayleigh–Plateau instability or Rayleigh instability; prompt on Plateau instability; reject “Rayleigh–Taylor instability”]
[10e] Negative imaginary frequencies exist when there is a sharp gradient in this quantity in a shear flow, causing the Kelvin–Helmholtz instability. The curl of this quantity is vorticity.
ANSWER: flow velocity [accept velocity field or velocity profile; reject “speed” or “flow speed”]
<Physics>
Summary
| 2023 ACF Nationals | 04/22/2023 | Y | 1 | 10.00 | 100% | 0% | 0% |
Data
| Georgia Tech A | Chicago A | 0 | 0 | 10 | 10 |