turbulent flow - 2025 ACF Nationals

Bonus

Despite the Orr–Sommerfeld equation always predicting stable eigenvalues for planar Couette (“coo-ET”) flow, this phenomenon is observed experimentally at a Reynolds number of about 360. For 10 points each:

[10e] Name this kind of unstable flow that is contrasted with laminar flow.

ANSWER: turbulent flow [accept turbulence]

[10m] A high Reynolds number and the presence of this process can indicate turbulent flow. A “street” named for von Kármán can form behind a body as it does this action to vortices.

ANSWER: vortex shedding

[10h] The onset of turbulence can be photographed using this imaging technique invented by August Toepler to view shock waves. Like the shadowgraph technique, it uses changes in refractive index as a proxy.

ANSWER: schlieren photography [or schlieren imaging]

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Conversion

Team	Opponent	Part 1	Part 2	Part 3	Total	Parts
Arizona State	Ottawa	10	0	0	10	E
British Columbia	Georgia State	10	0	0	10	E
Chicago A	WUSTL A	10	10	10	30	EMH
Chicago B	MIT	10	0	0	10	E
Columbia A	Northwestern	10	10	0	20	EM
Cornell A	Georgia Tech	10	10	0	20	EM
Florida	Penn State	10	10	0	20	EM
Harvard	Johns Hopkins	10	0	0	10	E
Illinois B	Virginia	10	10	10	30	EMH
Indiana	Rutgers	10	10	10	30	EMH
Maryland	North Carolina B	10	10	0	20	EM
Michigan	Cornell B	10	0	0	10	E
Minnesota	Iowa State	10	0	0	10	E
NYU	Waterloo B	10	10	0	20	EM
RIT	Columbia B	10	10	0	20	EM
Stanford	North Carolina A	10	10	10	30	EMH
Texas	Toronto C	10	0	0	10	E
Toronto A	Waterloo A	10	10	10	30	EMH
Toronto B	Virginia Tech	10	0	0	10	E
UC Berkeley A	Illinois A	10	0	0	10	E
UC Berkeley B	LSE	10	0	0	10	E
UCF	Winona State	10	0	0	10	E
Vanderbilt	Ohio State	10	0	0	10	E
Yale	WUSTL B	10	0	0	10	E

Summary

Tournament	Exact Match?	Heard	PPB	Easy %	Medium %	Hard %
2025 ACF Nationals	Yes	24	16.67	100%	46%	21%