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Papers & preprints
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A topographic map of---almost---flatland!
The interference
patterns of light reflected from a soap film (see the section on soap films for more info) have a dramatic appearance when the light source is monochromatic (has only one
wavelength). The reflected light is
essentially either turned on or off. This leads to beautiful black and
white curves which trace regions of the film with the same
thickness. The examples shown are mainly of a Von Karman vortex street
behind a single circular rod:
You can also imagine bringing two cylinders, each shedding its own vortex street, close together. The type of behavior observed is dependent on both the size of the cylinders and the distance between them. When this distance gets to a few cylinder diameters they start to interact sporadically, sometimes locking phase, sometimes slipping by each other in a ratcheting sort of motion. As their distance apart is reduced (to roughly 3 diameters) they lock into a pattern of vortex shedding 180 degrees out of phase so that the two streets are a mirror image of one another and ultimately form a hexagonal array of vortices. When their spacing is reduced even further (to about 2 diameters) the vortex streets lock in-phase to create a dramatically different pattern:
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