Re: experiments in 2-D hydrodynamics

[Sam Held <held@utkux.utcc.utk.edu>]

Hi all,
	I had some requests for this information but due to my PhD
qualifying exams I was a little busy.  But now I have the free time to
copy over the article on 2D hydrodynamics.  I have included it below.


							Sam Held

sheld@utk.edu


        This article appeared in the July 1998 issue of the APS News and
was a report of part of the activities of the Spring Meeting of the
APS/AAPT that took place in the late April in Columbus, OH (meeting was
hosted by Ohio State).
 	On Sunday afternoon, physicists from Ohio State University
entertained attendees of the APS/AAPT Spring Meeting with demonstrations
illustrating physics principles in everyday objects.  Sponsored by the
Physics Instructional Resource Association (PIRA) and the AAPT Apparatus
Committee, the session was very well attended.  PIRA is an organization
intended to serve the needs of physics educators around the country by
providing means for sharing ideas about demonstrations, laboratory
activities, and instructional resources in general to advance the quality
of physics education at all levels.
        Maarten Rutgers displayed his talents for building some of the
world's largest soap films, which can approach heights of 20 feet.  He has
constructed an apparatus to study two-dimensional fluid flows, which are
typical in planetary atmospheres, for example.  The device consists of two
vertical nylon wires hanging down from a single point, held taut by a
weight to form the sides of the flow channel.  A simple soap solution -
typically one or two parts of Dawn dish soap detergent to 100 parts tap
water - drops onto the wire at the top.  As it dribbles down, the wires
adhere together with the soap solution.  They are then pulled apart,
forming a soap film in between them.  Gravity pulls the film down at a
rate of approximately 10 miles per hour, and a bucket beneath the weight
collects the solution.
        Rutgers' laboratory films are typically about 8 to 10 feet tall
and 2-6 inches wide, but "nothing stops you from making these films as
large as you like," he said.  He has constructed soap films 4 stories high
and 14 feet wide in the atrium of the Carnegie Science Center in
Pittsburgh, PA.  A giant soap film reaching 7 stories (80 feet) and 4 feet
wide was produced at the University of Chicago's James Franck Institute.
Such tall films, says Rutgers, are 10,000,000 times taller than they are
thick.  The Xperiment Museum in Stockholm, Switzerland now has a permanent
installation with a two-story flowing film.
        Roderick grant (a.k.a. "Chef Boy R.G."), a professor emeritus at
Denison University and amateur chef, used simple cooking examples to
demonstrate basic physics concepts.  For example, he added a tablespoon of
hot cocoa to a cup, filled it with hot water, and then tapped the cup's
bottom with a spoon until the pitch stabilized.  He then poured water into
one tall glass, and club soda into a second, tapping the bottoms of each
to compare the pitch.  The pitch of the glass of soda water changed after
it was stirred gently.  "Dissolved air released from mixing cocoa, or from
the release of CO2 in soda, modifies the velocity of sound and
consequently the perceived pitch," Grant explained.  He also demonstrated
conduction and convection cooling, using containers of water and soup,
respectively, and supplied attendees with a reference list for a wide
variety of articles discussing the culinary aspects of physics and
chemistry.
        Leonard Jossem and Richard Noll displayed unexpected electrical
behavior in ordinary light bulbs, showing how to confine an electron in a
Penning trap, as well as how to trap fluorescent particles.  Edward
Adelson demonstrated a spectrum of pastel colors obtained without the
usually required prism or slit.  Alas, a scheduled appearance by
unicyclist Harris Kagan, intended to demonstrate that a ball thrown
straight up in the air while on a moving unicycle will always land right
in front of him, was canceled due to injury during practice.
        Additional information and photos of giant soap films, as well as
directions on how to make your own, links to other Web sites, and
references to books and articles on the subject, can be found at
http://www.physics.ohio-state.edu/~maarten and
http://www.exploratorium.edu/ronh/bubbles/bubbles.html.  More information
about unicycling may be found at http://www.unicycling.org.
 
 


On Sat, 18 Jul 1998, Inge H A Pettersen wrote:

> Sam Held wrote:
> > Harry,
> >         I believe it is very thin liquid that happens to border two
> > systems of different pressures.  In fact, I just read a report in the APS
> > News "paper" about a talk at the Spring APS meeting in Columbus where a
> > professor was using bubles to run experiments in 2-D hydrodynamics.  I can
> > dig it up for more details if you wish.If you know about any reference of these experiments, I would be interested as well