The waterwheel at the Fachhochschule Brugg-Windisch (Switzerland) was constructed in the context of Environmental Ethics Courses introduced by Fridolin Stähli and Fritz Gassmann in the 1990s. Its task is to remind the students that predictability of the outcome of anthropogenic influences on natural systems (e.g. the global climate system, ecosystems, etc.) is limited. In the 21st century, the technical question "how can this be done?" has to give more and more room to the ethical question "should we do or better leave this?"
The interplay between ethics and natural sciences is explained in more detail in:
Fridolin Stähli; Fritz Gassmann: Umweltethik -- Die Wissenschaft führt zurück zur Natur, Sauerländer, Aarau, Fortis, Frankfurt/M., Bohmann, Salzburg, will be published in fall 2000.
The waterwheel was constructed by Dieter Meier (Windisch, former physics teacher at FH) and the FH mechanical Lab Group and sponsored by the FH-Stiftungsrat. It looks impressing with its diameter of 2 m and attracts attention of students, visitors and many other people walking or driving by.
Chaos is creative: The waterwheel mouvement never repeats!
For getting convinced that the waterwheel never repeats a longer sequence, count the number of buckets passing below the faucet between reversals of turning direction: The sequence begins as 8-16-30-21-8-13-9-9-8-13 over the first 4 minutes after reset. You see that the short sequence 8-13 repeats. I did not wait until the whole sequence of the above 10 numbers appears again, I expect it would take some days. But even this reappearance of a short sequence is far from being periodic. A sequence of around 50 numbers will need the age of the universe to repeat once again!
Select Waterwheel FH Brugg. The presetted
parameters correspond to the normal operating conditions of the FH-waterwheel
and lead to chaotic mouvement. To see the effect of the magnetic brake
(its strength is proportional to angular velocity "omega"), you can set water
supply rate to zero. By "kicking" the waterwheel, you see the strong damping:
it is a strongly dissipative system. You understand the importance of the
brake by setting it to zero while supply rate is at e.g. 500 g/s. Realize
also transient chaos when increasing inflow rate to 2000 g/s with brake
strength as presetted: after a while of ongoing chaotic movements, the
waterwheel "finds" the stationary state (with constant angular velocity):
chaos is for high water supply rates of transient nature. The length of the
chaotic transient depends on the initial conditions: Kick the waterwheel
several times just after starting to change its initial conditions and
observe different transient lengths. Another way to influence transient
length is to slightly change water supply rate or brake strength.
Many transients will last between 35 and 70 s, but also shorter and longer
transients are possible.
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