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ERIC Number: EJ876100
Record Type: Journal
Publication Date: 2010-Feb
Pages: 5
Abstractor: As Provided
Reference Count: 13
ISSN: ISSN-0031-921X
The Ekman Layer and Why Tea Leaves Go to the Center of the Cup
Heavers, Richard M.; Dapp, Rachel M.
Physics Teacher, v48 n2 p96-100 Feb 2010
Consider a transparent, cylindrical container filled with water and sitting in the center of a record player turntable. When the turntable is started suddenly, the container rotates with the turntable, but the bulk of the fluid initially remains at rest. A thin ([approximately]1 mm) viscous boundary layer (Ekman layer) forms almost immediately at the bottom and top (if there is a lid) of the fluid. Here we describe a laboratory or demonstration exercise in which we use dye crystals and fine particles as tracers to study the flow in the Ekman layer. We also give a general method for using fine particles to measure the time it takes for the bulk of the fluid to rotate with the turntable (spin-up time) for different rates of rotation and fluid depths.
American Association of Physics Teachers. One Physics Ellipse, College Park, MD 20740. Tel: 301-209-3300; Fax: 301-209-0845; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Identifiers - Location: Rhode Island