GFD-1 LAB #3 CORIOLIS-1 - I
P.B.Rhines, E.G.Lindahl
This is an excellent experiment by Satoshi Sakai
(http://dennou-t.ms.u-tokyo.ac.jp/library/gfd_exp/exp_e/)
at University of Tokyo.
A two-layer fluid has long, hydrostatic gravity
waves excited by a plunger (an up-and-down moving solid) which
is in the corner of this square tank. The visualization is using
polarization of light by a birefringent fluid (limonene, a somewhat
poisonous material found in orange peels) in water).
Light coming up through the fluid has its polarization vector rotated
by the fluid, by an amount proportional to the fluid layer depth.
Then it is viewed with poloroid sheets (like sunglasses).
The circular wave crests emanate from the corner, later to reflect from the walls
and form a standing wave (which in the video appeared as a checkerboard pattern
of up-and-down motion). With rotation (upper figure) and frequency > f, no
free waves are possible except Kelvin waves which propagate round the boundary,
cyclonically. They are trapped to the boundary by rotation.
Falling under 'gravity'
A dense falling object falls at an angle between that of the
geopotential gradient (the normal to the paraboloidal 'geo'potential of
the rotating table) and the rotation axis.
(Above 2 images) Small, tall cyclonic convection cells as warm water cools
on a rotating
table. These exquisite tornadoes occur due to evaporation at the water surface.
The latent heat flux upward cools the water (a glass of water sitting on a table has
an equilibrium temperature cooler than the air temperature around it). The 'tree
trunks' are the sites of sinking (downwelling) at the center of each vortex.
______________________
Deflection of a low Reynolds number jet by the Coriolis force
This slow, dyed jet enters from a capillary tube and is deflected on an
inertial
trajectory...yet it is not a free particle. It begins to interact with the surroundings in the
images below. The dye is slightly heavy, and drifts downward. Imagine the fluid trying
to 'find' a geostrophic balance, a pressure field that can oppose Coriolis. In this geometry
it is not possible because it would require a pressure difference across the jet, extending out
to "infinity". A chain of eddies seems the inevitable result.
Vortex driven by upper source, lower sink, with pingpong ball tracers
Taylor column in red, is trapped over a mountain
until flow speed is increased, sweeping it off:
vertical stretching gives it cyclonic vorticity
Here the cyclone has moved well away from its parent mountain,
which has a bound anticyclonic vortex resident above it.